Abstract

The role of the father in psycho-affective development is indispensable. Yet, the neurobehavioral effects of paternal deprivation (PD) are poorly understood. Here, we examined the behavioral consequences of PD in the California mouse, a species displaying monogamous bonding and biparental care, and assessed its impact on dopamine (DA), serotonin (5-HT), and glutamate (GLU) transmission in the medial prefrontal cortex (mPFC). In adult males, deficits in social interaction were observed, when a father-deprived (PD) mouse was matched with a PD partner. In adult females, deficits were observed when matching a PD animal with a non-PD control, and when matching 2 PD animals. PD also increased aggression in females. Behavioral abnormalities in PD females were associated with a sensitized response to the locomotor-activating effect of amphetamine. Following immunocytochemical demonstration of DA, 5-HT, and GLU innervations in the mPFC, we employed in vivo electrophysiology and microiontophoresis, and found that PD attenuated the basal activity of low-spiking pyramidal neurons in females. PD decreased pyramidal responses to DA in females, while enhancing responses to NMDA in both sexes. We thus demonstrate that, during critical neurodevelopmental periods, PD leads to sex-dependent abnormalities in social and reward-related behaviors that are associated with disturbances in cortical DA and GLU neurotransmission.

Introduction

Early attachment experiences with the primary caregiver forge an internal working model for subsequent adult relationships, and parental neglect is notoriously linked to neurodevelopmental and behavioral disorders that may persist through adulthood (Bowlby 1978; Tyrka et al. 2008; Murray et al. 2012). Despite emerging evidence for the impact of parental deprivation (Helmeke et al. 2001; Ziabreva et al. 2003; Bredy et al. 2004; Kaffman and Meaney 2007), the primary focus has been on mother-offspring relationships. Nevertheless, human studies have pointed out that paternal deprivation (PD) impairs psychological and mental development, and increases risk for substance abuse and personality disorders (Grossmann et al. 2002; Jablonska and Lindberg 2007; Lamb 2010). However, the neurobiological substrate underlying PD-induced behavioral and neurobiological impairments remains unknown.

Paternal care or biparental rearing patterns are found only in a minority of mammalian species (Kleiman and Malcolm 1981). California mice (Peromyscus californicus) display permanent father–mother pair bond and extensive biparental investments that have accounted for increased offspring survival and growth (Yogman 1981; Gubernick and Alberts 1987; Ribble and Salvioni 1990; Gubernick and Teferi 2000; Becker et al. 2005; Schradin and Pillay 2005). This species therefore represents a useful model for examining the behavioral and neurobiological impact of PD. Few studies in biparental rodents have suggested that PD impairs cognitive and emotional functions in offsprings, especially in low-resource availability and high-foraging demand conditions (Bredy et al. 2004, 2007). This effect of PD is not surprising as all maternal offspring-directed nurturing behaviors (huddling, licking and grooming, hover-crouching, carrying, and retrieving), except for parturition and lactation, are also performed by the father (Dudley 1974; Gubernick and Alberts 1987), and are uncompensated by the mother in the father's absence (Dudley 1974; Bester-Meredith and Marler 2003; Helmeke et al. 2009; Jia et al. 2009). Paternal behaviors also include involvement in social play and enhanced attention when juveniles are distressed (Wilson and Kleiman 1974; Becker et al. 2005; Bredy et al. 2007; Lambert et al. 2013), which are associated with lower activation of brain structures involved in emotional integration, including prefrontocortical regions (Lambert et al. 2013).

Evidence in monogamous rodents suggests that PD can compromise synaptic development in the medial prefrontal cortex (mPFC) (Helmeke et al. 2009; Pinkernelle et al. 2009). The mPFC is involved in processing socially relevant information (Insel 2003; Wolff and Sherman 2007), and activity in its dorsomedial subregions has been linked to prosocial behaviors (Waytz et al. 2012). DA is known to interact with neurobiological systems regulating social behavior, including the neurohormones oxytocin and vasopressin (Insel 2003; Baskerville and Douglas 2010). Dopamine (DA) and serotonin (5-HT) receptors are highly expressed and co-localized with NMDA receptors in the mPFC, where they regulate synaptic plasticity and neural activity, as well as emotional behavior. In addition, alterations in NMDA receptor subunits have been associated with PD (Bredy et al. 2007). Sexually dimorphic effects of NMDA antagonists have been observed on social and alloparenting behavior (Kirkpatrick and Kakoyannis 2004), and on behavioral functions associated with the reward circuit (Hönack and Löscher 1993; D'Souza et al. 1999) and modulated by gonadal steroid hormones (D'Souza et al. 2003).

In this study, we examined social interaction (SI) and aggressive behavior, as well as the reward response to amphetamine, in adult California mice raised under sole maternal care in comparison to those raised under biparental care. In addition to providing the first description of DA, 5-HT, and glutamate (GLU) innervations in the California mouse mPFC, we characterized the electrophysiological responses to DA, 5-HT, and NMDA in order to correlate behavioral consequences of PD with synaptic function in the mPFC.

Materials and Methods

Animals

Adult California mice (Peromyscus californicus) that were used for breeding (first batch) were kindly offered by Dr Michael Meaney (McGill University, Montreal, Canada) or obtained (second batch) from the University of South Carolina Peromyscus Genetic Stock Center. All procedures were undertaken in compliance with the standards and ethical guidelines mandated by the local facility animal care committee of McGill University, the Canadian Institutes of Health Research, and the Canadian Council on Animal Care. Breeding pairs were age-matched (within a 3-month age range), and no siblings were mated. Pairs were housed in standard polycarbonate cages (26.5 cm W × 48.5 cm D × 20.3 cm H) with corncob bedding, kept under standard vivarium conditions (12:12 h light/dark cycle, lights on at 7:30 AM and temperature at 20 ± 2°C, 50–60% relative humidity) and given ad libitum access to food and water.

Paternal Deprivation

On postparturition day (PND) 3, litters (1–3 pups/litter) were randomly designated to either be left with only the mother (PD) or with both parents (control, CT), as already described by Bredy et al. (2004). Fathers were then permanently removed from the PD litter. Mother and pups were thereafter left undisturbed until weaning on PND30 (de Jong et al. 2012), except for routine maintenance. CT litters were left undisturbed with both parents until weaning. After weaning, a PD mouse was housed with a PD mouse and a CT mouse with another CT, in same-sex littermate pairings. Because cognitive and behavioral effects of PD can be detected as early as PND 60 (Bredy et al. 2004), we began experiments when offsprings were at least 70 days old, just at the onset of the average age of natal dispersal (in the wild) and maturity (McCabe and Blanchard 1950; Ribble 1992; de Jong et al. 2012). A chronological representation of procedures is depicted in Figure 1.

Figure 1.

Experimental design. The chronogram shows a simplified organization of events pooled from separate experiments for 2 different batches of animals obtained from 2 groups of breeding pairs. After mating that commenced on Day 1, a month was allotted to obtain a sufficient number of offsprings that were subsequently assigned at PND3 to the father-deprived (PD) group or the biparental (CT) group (maximal age range = 30 days). The offsprings were weaned at PND30, and then housed in same-sex pairs. Upon reaching a sufficient number of animals, the open field (OF) and social interaction (SI) tests were conducted on Day 70 (animals at PND70-PND100). Some of these animals were used for electrophysiological experiments from Day 72 to Day 105 (animals were at PND72 to PND105). Some animals that did not undergo the OF and SI tests were also used for electrophysiology. Prior exposure to the OF, SI, and similar behavioral tests does not produce detectable changes in monoaminergic neural activity as we have previously demonstrated (Bambico et al. 2010a, 2010b). Another group was used for the amphetamine (amph) sensitization experiments (PND72-PND102), which was not further tested for electrophysiology.

Figure 1.

Experimental design. The chronogram shows a simplified organization of events pooled from separate experiments for 2 different batches of animals obtained from 2 groups of breeding pairs. After mating that commenced on Day 1, a month was allotted to obtain a sufficient number of offsprings that were subsequently assigned at PND3 to the father-deprived (PD) group or the biparental (CT) group (maximal age range = 30 days). The offsprings were weaned at PND30, and then housed in same-sex pairs. Upon reaching a sufficient number of animals, the open field (OF) and social interaction (SI) tests were conducted on Day 70 (animals at PND70-PND100). Some of these animals were used for electrophysiological experiments from Day 72 to Day 105 (animals were at PND72 to PND105). Some animals that did not undergo the OF and SI tests were also used for electrophysiology. Prior exposure to the OF, SI, and similar behavioral tests does not produce detectable changes in monoaminergic neural activity as we have previously demonstrated (Bambico et al. 2010a, 2010b). Another group was used for the amphetamine (amph) sensitization experiments (PND72-PND102), which was not further tested for electrophysiology.

Behavioral Assays

The SI test was used to assess social behavior in same-sex dyads. The open field (OF) test was conducted for the assessment of locomotor activity and anxiety-like thigmotactic (wall-following) behavior. On the day of testing, mice were acclimated for about 60 min in the behavioral room before the procedures were initiated. The apparatus was cleaned with 70% alcohol and water after each run. The behaviors were recorded, stored, and analyzed as MPEG files using an automated tracking system (Videotrack, View Point Life Science, Montréal, QC, Canada) equipped with infrared lighting-sensitive CCD cameras. The analog signals supplied by the camera were measurements of the luminosity of each point from images scanned point-by-point and line-by-line at the rate of 25 images per second. These signals were transmitted to the videotrack system and digitized on 8 bits by digital analog conversion. Before experiments, animal/image background contrast detection thresholds were calibrated by visual inspection to distinguish different behavioral patterns. Additional offline analyses were conducted by a rater who was blind to the experimental manipulations. All behavioral experiments were carried out from 2:00 PM to 7:00 PM.

OF and SI Tests

For the OF test, each mouse was placed at the center of a white-painted OF arena (40 × 40 × 15 cm) and left to explore the whole field for 5 min of recording. Four identical arenas were used to test 4 animals at a time. Arena assignments were counterbalanced so that all experimental groups were equally distributed to each of the arenas. Each animal underwent a single OF test. The experiment took place under standard room lighting (∼350 lx) by a white lamp (100 W) suspended 2 m above the arena. Locomotor activity was measured by the total distance traveled (cm). Immediately after the OF test, the SI test was carried out to analyze social behavior using a procedure modified from Whatson et al. (1974, 1976), McFarlane et al. (2008), and Cox and Rissman (2011). The test was conducted in the same arenas previously used for the OF test at a different location within the same testing room, so that animals were all habituated to the testing room. Here, we assessed changes in the social behavior of adult California mice that have been reared by both parents, in comparison to those subjected to PD, by examining the behavior of PD mice when paired with a CT or with another PD animal. The test lasted for 20 min in order to evaluate persistent changes in social behavior. On the first session, same-sex unfamiliar conspecifics were match-paired according to rearing condition (PD–PD or CT–CT). On the second session, same-sex unfamiliar conspecifics were mix-paired (PD–CT). Each animal was paired with a CT and a PD in a fixed order, and there was a very short delay between the first and second SI test. No animals met more than once. The frequency and duration of several components of social behavior for each animal from match and mixed pairings were encoded and analyzed offline. These included social investigation, which consisted of sniffing, trailing (following the partner), mounting or crawling under or over the partner, and defensive (targeting the back or flanks) or offensive (targeting the snout) aggression. The time (latency) until the dyad first contacted each other was also measured. Avoidance (evading the partner) and passive contact or side-by-side sitting (remaining close to each other but without actively investigating the partner), as well as auto-grooming, were additionally recorded (McFarlane et al. 2008; Cox and Rissman 2011). As the SI test has also been used to evaluate social anxiety, as well as anxiogenic sequelae of chemical agents or genetic manipulations (Cassano et al. 2010), it is conceivable that PD-induced social impairments observed in this test could result from a potentiation of anxiety-like states and/or secondary to motor activity impairment. We therefore also examined anxiety-like reactivity from thigmotactic behavior measured by the frequency and total duration of central zone (30 × 30 cm) visits in the OF test (Choleris et al. 2001).

Behavioral Sensitization

As DA is implicated in the adverse consequences of psychostimulant exposure on pair bonding and social behavior, and that drug reward and social behavior may recruit overlapping DA pathways (McGregor et al. 2008; Liu, et al. 2010), we ascertained whether changes in mPFC DAergic neurotransmission would translate into an enhanced long-term sensitization to the locomotor-activating effects of amphetamine. Robust sensitizing response to the locomotor-activating effects of amphetamine that is independent of age and environmental context has been demonstrated in Peromyscus mice (Tanimura et al. 2009). Therefore, d-amphetamine sulfate (Sigma Aldrich, UK) was administered intraperitoneally (1.5 mg/kg) to CT and PD males and females, daily at 2 PM for 7 days, to induce the development of locomotor sensitization. This dose is the minimal dose to optimally induce rapid-onset sensitization in both mice (Harrison and Nobrega 2009) and rats (Bhardwaj et al. 2006). Immediately following each amphetamine injection, each animal was placed in an OF arena (40 × 40 × 15 cm) to which the animals were adequately habituated (previously used for basal locomotor testing and SI test). Locomotor activity (distance traveled, cm) was recorded for 5 min, the enhancement of which was indicative of behavioral sensitization to the psychostimulant's effects. The daily progression of amphetamine-induced locomotor activation was also monitored. The effects of amphetamine in these animals were compared with CT and PD animals receiving once daily injections of saline. The experiments were carried out from 2PM–7PM.

Immunohistochemical Detection of GLU, 5-HT, and DA Fibers

Antibody staining was used to visualize, for the first time in this species, GLUergic, 5-HTergic, and DAergic innervations of prelimbic and cingulate cortices. Four adult California mice (2 males and 2 females) were deeply anesthetized with sodium pentobarbital (80 mg/kg, i.p.) and perfused through the heart with 100 mL of phosphate-buffered saline (PBS: 0.9% NaCl in 50 mM PB, pH 7.4) followed by 200 mL of fixative solution (4% paraformaldehyde in 0.1 mM phosphate buffer, PB, pH 7.4). The brain was removed, postfixed in 4% PFA (1 h, 4°C), and washed in PBS. Coronal forebrain sections (50 μm thick) were cut with a vibratome and processed free-floating as follows. Primary antibodies were monoclonal mouse anti-tyrosine hydroxylase (TH, for DA; Sigma, St Louis, MO, USA); polyclonal goat anti-serotonin transporter (SERT, for 5-HT; Santa Cruz Biotechnology, Santa Cruz, CA, USA); and rabbit antivesicular GLU transporter 2 (VGLUT2, for GLU; Synaptic Systems, Göttingen, Germany). The specificity of these commercially available antibodies has already been described in full (TH: Haycock 1993; SERT: Huang and Pickel 2002; VGLUT2: Takamori et al. 2001). Secondary antibodies used for light microscopic immunocytochemistry were biotinylated goat anti-mouse, donkey anti-goat, and goat anti-rabbit IgGs (Jackson Immunoresearch, West Grove, PA, USA), to be revealed with the 3,3-diaminobenzidine (DAB) or VIP substrate kits from Vector Labs (Burlingame, CA, USA). Species-specific IgGs conjugated to Alexa Fluor-488 or 594 (Invitrogen Corporation, Grand Island, NY, USA) were used for double immunofluorescence and confocal microscopy.

For single immunoperoxidase labeling and light microscopy, all incubations were at room temperature (RT). Sections were immersed 20 min in 3% hydrogen peroxide (H2O2), rinsed in PBS, and preincubated for 2 h in a blocking solution (BS) of PBS containing 5% normal goat serum, 5% normal donkey serum (Vector Labs), 0.5% gelatin, and 0.3% Triton X-100. Sections were then washed in PBS, incubated overnight with either anti-TH, anti-VGLUT2 (1:1000 in BS), or anti-SERT (1:700 in BS) antibody, rinsed in PBS, incubated 2 h with species-specific biotinylated IgGs (1:1000 in BS), and incubated for 1 h in a 1:1000 dilution of horseradish peroxidase-conjugated streptavidin (Jackson). After washes in PBS, labeling was revealed 1–2 min with the DAB (SERT) or VIP (TH, VGLUT2) peroxidase substrate kit. The reaction was stopped in distilled water, the sections rinsed in PBS, air-dried on gelatin-coated slides, dehydrated in ethanol, cleared in toluene, and mounted with DPX (Fluka, Sigma-Aldrich, Oakville, ON, Canada). The prefrontal cortex (PFC) was carefully examined at low (×1.6 objective) and high (×6.3 objective) magnification under a Leitz Diaplan microscope couple to an Olympus DP21 color digital camera and software (Olympus Corporation, Tokyo, Japan).

For double immunofluorescent labelings and confocal microscopy, all sections were preincubated 2 h in BS as above. For double GLU/DA immunofluorescence, sections were incubated overnight with both anti-VGLUT2 and -TH primary antibodies (1:1000 in BS). After washes in PBS, sections were further incubated for 3 h (light protected) with a mix of species-specific Alexa Fluor 488 (VGLUT2) and Alexa Fluor 594 (TH) conjugated IgGs (1:200 in BS). For double GLU/5-HT immunofluorescence, sections were incubated overnight with the anti-SERT primary antibody (1:700 in BS). Subsequent incubations and washes were light protected. After washes in PBS, sections were then incubated for 3 h with Alexa Fluor 594 conjugated anti-goat IgGs (1:200 in BS). After washes in PBS, sections were further incubated overnight with the anti-VGLUT2 antibody (1:1000 in BS), and then 3 h with Alexa Fluor 488-conjugated anti-rabbit IgGs (1:200 in BS) following washes in PBS. For both double labeling experiments, after rinses in 0.1 M PB and distilled water, sections were mounted in Vectashield medium for fluorescence (Vector) and observed with a Leica TCS-SP1 confocal microscope using sequential laser analysis (×100 magnification). Images of 1024 × 1024 pixels were produced with the Leica confocal software (v2.65) and adjusted for framing and contrast with the Adobe Photoshop software.

In Vivo Electrophysiology and Microiontophoresis

We aimed at determining whether PD could significantly influence DA, 5-HT, and GLU neurotransmission in the mPFC. To do so, we assessed the response of mPFC pyramidal neurons to these neurotransmitters, indicating the sensitivity and function of their attendant receptors. Electrophysiological experiments were conducted between PND 70 and 105, with animals weighing 30–40 g. The electrophysiological procedures were previously described in Bambico et al. (2010a, 2010b) and Gobbi et al. (2001). Briefly, animals were anesthetized (1.2 g/kg urethane, intraperitoneal). Additional doses were delivered during the procedure to maintain full anesthetic state. Animals were fixed to a stereotaxic frame (David Kopf Instruments, Tujunga, CA, USA), the scalp overlying the rostral medial skull was removed, and a burr hole was drilled through the skull around the area of bregma + 2.3 mm. A glass multibarrel recording pipette (Protech International, Inc., TX, USA) was then lowered into the mPFC (0.5–2.5 mm from the brain's surface) to record pyramidal neurons in the dorsomedial (cingulate and prelimbic) region. These neurons were identified based on their steady response to standard short pulses of NMDA (5 nA) and by large amplitudes (0.5–1.2 mV), long durations (0.8–1.2 ms), and single-action potential patterns alternating with complex spike discharges (Barthó et al. 2004; Gobbi and Janiri 2006; Labonte et al. 2009). Since there is no published stereotaxic atlas of the Peromyscus brain, which is considerably larger than that of Mus musculus, stereotaxic coordinates were approximated by integration of coordinates from the mouse (Paxinos and Franklin 2007) and the rat (Paxinos and Watson 2007) stereotaxic atlases. The location of the last recording was verified histologically in each animal by Pontamine sky blue microinjections. The recording barrel was filled with Potamine sky blue, and adjusted to a signal impedance of 0.5–4 MΩ by breaking the tip. A 2 M NaCl solution acted as an automatic balance and was leaked against a 50 MΩ impedance. Drug barrels were filled as follows: DA (50 mM in 200 mM NaCl, pH 4–5) was ejected against an impedance of 150 MΩ, retained with a −5 nA current, and ejected as a cation. NMDA (50 mM in 200 mM NaCl, pH 8) was ejected against an impedance of 125 MΩ, retained with a 10 nA current, and ejected as an anion. 5-HT (50 mM in 165 mM NaCl, pH 4) was ejected against an impedance of 150 MΩ, retained with a −5 nA current, and ejected as a cation. When a neuron displaying a stable firing activity was encountered, the spontaneous firing rate was recorded for at least 5 min, and the first minute was excluded from analysis to avoid artifacts. Each drug was then ejected for at least 30 s, and then withdrawn to re-establish the baseline. Upon drug current withdrawal, the firing rate normally reverts to baseline. Drug-induced changes in firing rate (percentage increase/decrease from predrug baseline activity) was calculated as the difference between the mean firing rate during the ejection phase and the baseline mean firing rate (at least 30 min prior to ejection) divided by the baseline mean firing rate. Neuronal responses were sampled across 4–6 drug currents. All electrophysiological recordings were conducted from 2 to 10 PM. Forty-eight animals (33 males + 15 females) underwent electrophysiological procedures. Spontaneous basal pyramidal firing rate data were obtained from all of these animals (4–7 electrode descents per animal = 307 neurons recorded from males and 196 neurons from females). Some animals representing each group (6–8 animals per group) were used for iontophoretic drug applications. Six to 19 neurons were recorded per group. Two to three transmitters (1 drug current response each) were tested per neuron. As animals' ages were from PND 70 to PND 105, a correlational analysis between firing rate and age of animals was done, as well as maximal excitatory/inhibitory response to drugs and age, without reaching any significant correlations. We therefore did not proceed running covariate analyses. Moreover, extensive studies in our laboratory suggest that monoaminergic firing activity within this age range is not significantly influenced by age in mice (Gobbi et al. 2001; Bambico et al. 2010a).

Statistical Analysis

Data are presented as mean ± standard error of the mean (SEM). All data were analyzed using Sigma Plot version 11 (Systat Software, Inc., San Jose, CA, USA) and SPSS version 17 (SPSS, Inc., Chicago, IL, USA) softwares. Following tests for assumptions of data distribution normality (Shapiro–Wilk and Kolmogorov–Smirnov tests) and for variance homogeneity, datasets were accordingly submitted to one-way or two-way analyses of variance (ANOVAs) with pairing scheme (match-paired vs. mix-paired) and rearing condition (PD vs. CT) as between-group factors, when assumptions were satisfied. Otherwise, the nonparametric counterpart of these tests were carried out. Electrophysiological data were submitted to Student's t-test or Mann–Whitney U-test for between-group comparisons or to one-way or two-way mixed-design ANOVA (rearing condition × current) when accounting for repeated microiontophoretic current ejections. Tukey's honestly significant difference test was used for multiple post hoc comparisons. Probability value of P ≤ 0.05 was considered statistically significant.

Results

PD Impairs Dyadic Social Interactions in Both Sexes

Figure 2 shows that among males, a dramatic reduction of social investigation was observed only when a PD male was matched with another PD male (P < 0.01), but not when matched with a CT male (two-way ANOVA: pairing, F1,64 = 6.574, P = 0.013; rearing, F1,64 = 16.240, P < 0.001; interaction, F1,64 = 10.570, P = 0.002; Fig. 2A). The first mutual contact of PD–PD pairs had significantly longer latencies in comparison to CT–CT or CT–PD pairs (P < 0.05) (Kruskal–Wallis, followed by Mann–Whitney U-test, P = 0.011; Fig. 2C). In females, however, a reduction of the total time spent in social investigation was measured in all PD animals, regardless of whether they were paired with another PD female (PD–PD) or a non-deprived control (PD–CT) (two-way ANOVA: pairing, F1,74 = 0.376, P = 0.542; rearing, F1,74 = 176.188, P < 0.001; interaction, F1,74 = 1.358, P = 0.258; Fig. 2B). Furthermore, the latency to the first mutual contact was prolonged in both CT–PD and PD–PD female pairs in comparison to CT–CT pairs, although achieving significance in PD–PD pairs only (P < 0.05) (Kruskal–Wallis, df = 2, P = 0.028; Fig. 2D).

Figure 2.

Paternal deprivation (PD) led to marked impairments in several aspects of adult social behavior, as measured in the social interaction (SI) test. Father-deprived (PD) male and female mice showed significant reductions in the time spent investigating another PD mouse (sniffing, trailing, and crawling-over; stacked bars: black, gray, and white, respectively) (A and B). Female PD mice also exhibited this reduction in social investigation (B) when interacting with non-deprived (control, CT) mice. The latency to first contact was also significantly increased in PD–PD pairs of both sexes (C and D); female CT–PD pairs showed a slight (nonsignificant) increase in the latency to first contact. There was no change in the time spent actively avoiding contact across parings and between sexes (E and F) but passive contact was increased in females and in PD males (G and H). Bars represent mean duration (in seconds) ± standard error of mean (SEM). Male CT (paired with male PD), n = 21; male PD (paired with male CT), n = 18; male CT (paired with male CT), n = 21; male PD (paired with male PD), n = 8; Female CT (paired with female PD), n = 25; female PD (paired with female CT), n = 28; female CT (paired with female CT), n = 15; female PD (paired with female PD), n = 10. *P < 0.05, **P < 0.01.

Figure 2.

Paternal deprivation (PD) led to marked impairments in several aspects of adult social behavior, as measured in the social interaction (SI) test. Father-deprived (PD) male and female mice showed significant reductions in the time spent investigating another PD mouse (sniffing, trailing, and crawling-over; stacked bars: black, gray, and white, respectively) (A and B). Female PD mice also exhibited this reduction in social investigation (B) when interacting with non-deprived (control, CT) mice. The latency to first contact was also significantly increased in PD–PD pairs of both sexes (C and D); female CT–PD pairs showed a slight (nonsignificant) increase in the latency to first contact. There was no change in the time spent actively avoiding contact across parings and between sexes (E and F) but passive contact was increased in females and in PD males (G and H). Bars represent mean duration (in seconds) ± standard error of mean (SEM). Male CT (paired with male PD), n = 21; male PD (paired with male CT), n = 18; male CT (paired with male CT), n = 21; male PD (paired with male PD), n = 8; Female CT (paired with female PD), n = 25; female PD (paired with female CT), n = 28; female CT (paired with female CT), n = 15; female PD (paired with female PD), n = 10. *P < 0.05, **P < 0.01.

The reductions in the duration of social investigation observed in all affected animals were not due to increased avoidance or active movement away from the partner (Fig. 2E,F). Rather, passive contact with the partner (physical proximity devoid of any active, investigational behavior) was particularly increased in males (Fig. 2G,H) (PD–PD vs. CT–CT or vs. PD–CT, P < 0.001; two-way ANOVA: pairing, F1,64 = 7.842, P = 007; rearing, F1,64 = 19.997, P < 0.001; treatment, F1,64 = 19.042, P < 0.001) and females (PD–PD vs. CT–CT or vs. PD–CT, P < 0.05; two-way ANOVA: pairing F1,74 = 0.619, P = 0.434; rearing, F1,74 = 116.821, P < 0.001; interaction, F1,74 = 1.008, P = 0.319).

PD Increases Aggressive Behavior in PD Female Dyads

Assessment of offensive and defensive behaviors in antagonistic encounters revealed that PD females in a matched PD–PD pair exhibited dramatically longer duration episodes (P < 0.001) of aggressive behavior than any other pairs (Fig. 3; two-way ANOVA: pairing, F1,74 = 3.584, P = 0.062; rearing, F1,74 = 11.399, P = 0.001; interaction, F1,74 = 6.893, P = 0.011).

Figure 3.

Paternal deprivation (PD) influenced aggressive behavior in a sex-dependent manner. PD significantly increased episodes of aggressive behavior only in female PD mice partnered with another female PD mouse (B). There was no difference observed in male mice (A). Bars represent mean duration (in seconds) ± standard error of mean (SEM). Male CT (paired with male PD), n = 21; male PD (paired with male CT), n = 18; male CT (paired with male CT), n = 21; male PD (paired with male PD), n = 8; Female CT (paired with female PD), n = 25; female PD (paired with female CT), n = 28; female CT (paired with female CT), n = 15; female PD (paired with female PD), n = 10. **P < 0.01.

Figure 3.

Paternal deprivation (PD) influenced aggressive behavior in a sex-dependent manner. PD significantly increased episodes of aggressive behavior only in female PD mice partnered with another female PD mouse (B). There was no difference observed in male mice (A). Bars represent mean duration (in seconds) ± standard error of mean (SEM). Male CT (paired with male PD), n = 21; male PD (paired with male CT), n = 18; male CT (paired with male CT), n = 21; male PD (paired with male PD), n = 8; Female CT (paired with female PD), n = 25; female PD (paired with female CT), n = 28; female CT (paired with female CT), n = 15; female PD (paired with female PD), n = 10. **P < 0.01.

PD does not Affect Anxiety-Like Thigmotaxis and Locomotor Activity in the Open Field, but Induces Sensitization to the Locomotor-Activating Effect of Amphetamine in Females

Contrary to the hypothesis that social behavioral impairments in the SI test may be confounded by anxiety-like reactivity, we found no significant effects of PD in the anxiety-like thigmotactic behavior and locomotor or ambulatory activity (distance traveled) in the OF test (Fig. 4A,B). At best, there was a trend toward a lower locomotor activity in PD males compared with CT males (Tukey's test, P = 0.068; Fig. 4A) and an attenuation of the central zone duration (thigmotaxis) in PD compared with CT mice (two-way ANOVA: rearing, F1,40 = 3.66, P < 0.063; Fig. 4B). However, when PD was associated with psychostimulant amphetamine treatment (Fig. 4C,D), a significant enhancement of ambulatory activity was observed only in females most detectable on the seventh day of locomotor testing (P = 0.029), indicating a sensitized response of the DA system in a sex-specific manner (Fig. 4D).

Figure 4.

Basal locomotor activity (distance traveled in cm) and in thigmotaxis (total duration spent in the central zone) were not affected by PD. However, the distance that male father-deprived (PD) mice traveled was slightly less than that traveled by male nondeprived mice (control, CT) (P = 0.068). (A). Male and female PD mice also showed slight, nonsignificant attenuations in the total time of central zone visits (slight thigmotaxis, B). Male CT, n = 17; Female CT, n = 11; Male PD, n = 7; Female PD, n = 9. In testing for differences in the sensitized response to a psychostimulant, amphetamine was injected daily for 7 days. Immediately after the seventh treatment, locomotor activity (distance traveled in cm) in the OF was increased in comparison to control condition (saline injection) (C and D); paternal deprivation (PD) enhanced this locomotor-activating effect of amphetamine only in females (D). Bars represent mean distance traveled (cm) or mean duration (in seconds) ± standard error of mean (SEM), n = 6–8. *P < 0.05, **P < 0.01.

Figure 4.

Basal locomotor activity (distance traveled in cm) and in thigmotaxis (total duration spent in the central zone) were not affected by PD. However, the distance that male father-deprived (PD) mice traveled was slightly less than that traveled by male nondeprived mice (control, CT) (P = 0.068). (A). Male and female PD mice also showed slight, nonsignificant attenuations in the total time of central zone visits (slight thigmotaxis, B). Male CT, n = 17; Female CT, n = 11; Male PD, n = 7; Female PD, n = 9. In testing for differences in the sensitized response to a psychostimulant, amphetamine was injected daily for 7 days. Immediately after the seventh treatment, locomotor activity (distance traveled in cm) in the OF was increased in comparison to control condition (saline injection) (C and D); paternal deprivation (PD) enhanced this locomotor-activating effect of amphetamine only in females (D). Bars represent mean distance traveled (cm) or mean duration (in seconds) ± standard error of mean (SEM), n = 6–8. *P < 0.05, **P < 0.01.

GLU, DA, and 5-HT Fibers Coexist in the California Mouse mPFC

Following single immunoperoxidase labeling for photon microscopy and double immunofluorescence for confocal microscopy, the 3 transmitter systems (GLU, DA, and 5-HT) were detected in the California mouse forebrain (Fig. 5). As illustrated in Figure 5A (left), we demonstrate that VGLUT2 immunoreactivity is strong throughout the forebrain and denser in neocortical layers III–VIa, a distribution also observed in the mPFC (Fig. 5A, middle). At high magnification, VGLUT2 immunofluorescence appears punctate, which is characteristic of axon terminal labeling (Fig. 5A, right). TH immunoreactivity appeared particularly strong in the striatum, the major target of mesencephalic DAergic projections, and much more diffuse in the cerebral cortex (Fig. 5B, left). Despite being present in all cortical layers, TH-positive fibers appeared denser in neocortical layer VI, particularly in the mPFC (Fig. 5B, middle). As detected following anti-SERT immunohistochemistry, 5-HT fibers were found throughout the forebrain (Fig. 5C, left), particularly in the neocortex where they formed a denser network within layer IV. In the mPFC, however, SERT-positive axons were uniformly distributed (Fig. 5C, middle). At high magnification, both DA and 5-HT fibers (Fig. 5B,C, right) appeared as varicose axons intermingled with GLUergic nerve endings. Noteworthy is the fact that no co-localization was observed between the three markers in the mPFC.

Figure 5.

Immunohistochemical detection of GLU, DA, and 5-HT innervations in the California mouse forebrain and mPFC. Single immunohistochemical labelings (left panels) revealed with DAB (brown precipitate) or VIP (purple precipitate) demonstrate the coexistence of VLUGT2-positive (A), TH-positive (B) and SERT-positive (C) nerve fibers in the California mouse forebrain. Whereas 5-HT innervation (SERT+) appeared diffuse in the mPFC (C, middle), GLUergic (VGLUT2+) fibers were denser in cortical layers III-Via (A), and DAergic (TH+) fibers denser in layer VI (B). As illustrated for layer V of the mPFC (PrL) following double immunolabeling at the confocal level (A,B,C, right panels), GLU (green), DA (red), and 5-HT (red) axons appeared intermingled and not overlapping.

Figure 5.

Immunohistochemical detection of GLU, DA, and 5-HT innervations in the California mouse forebrain and mPFC. Single immunohistochemical labelings (left panels) revealed with DAB (brown precipitate) or VIP (purple precipitate) demonstrate the coexistence of VLUGT2-positive (A), TH-positive (B) and SERT-positive (C) nerve fibers in the California mouse forebrain. Whereas 5-HT innervation (SERT+) appeared diffuse in the mPFC (C, middle), GLUergic (VGLUT2+) fibers were denser in cortical layers III-Via (A), and DAergic (TH+) fibers denser in layer VI (B). As illustrated for layer V of the mPFC (PrL) following double immunolabeling at the confocal level (A,B,C, right panels), GLU (green), DA (red), and 5-HT (red) axons appeared intermingled and not overlapping.

PD-Induced Behavioral Impairments are Associated with Altered Glutamatergic Transmission in the mPFC

The basal discharge activity of mPFC (cingulate and prelimbic) pyramidal neurons is illustrated in Figure 6 (left). The recorded neurons were subdivided into low-spiking (firing rates < 20 Hz) and high-spiking (firing rates > 20 Hz) according to previously established criteria (Barthó et al. 2004; Gobbi and Janiri 2006). The high-spiking group corresponds to putative interneurons; the low-spiking group corresponds to putative pyramidal neurons (Swadlow 2003; Barthó et al. 2004; Gobbi and Janiri 2006) that were further tested in the microiontophoresis experiments. In male PD mice, when compared with CTs, no significant alterations in basal firing rates of both low-spiking and high-spiking neurons were found (Fig. 6). However, low-spiking pyramidal neurons from PD females showed significantly lower firing rates than in CT females (t = 329, P = 0.008).

Figure 6.

Effect of paternal deprivation (PD) on the basal firing activity of medial prefrontal cortex (mPFC) pyramidal neurons. Right panel: Graph showing the distribution of basal neuronal firing rates of recorded mPFC pyramidal neurons obtained from PD and control (CT) males (triangle) and females (circle). Neurons were segregated based on firing rate as low-spiking (20 Hz, below dotted line) and high-spiking (above dotted line). Only PD females had significantly lower mean low-spiking rates in comparison to female CTs. Left panel: Stereotactic location of recorded pyramidal neurons in the dorsomedial mPFC of CT males (unshaded triangles), PD males (shaded triangles), CT females (unshaded circles), and PD females (shaded circles). Cg1, cingulate area 1; PrL, prelimbic; IL, infralimbic; MO, medial orbital; DP, dorsal peduncular cortex. Bottom numbers represent plate coordinates in mm anterior to bregma (Paxinos and Franklin 2007). Male CT, n = 196; Male PD, n = 111; Female CT, n = 81; Female PD, n = 115. **P < 0.01.

Figure 6.

Effect of paternal deprivation (PD) on the basal firing activity of medial prefrontal cortex (mPFC) pyramidal neurons. Right panel: Graph showing the distribution of basal neuronal firing rates of recorded mPFC pyramidal neurons obtained from PD and control (CT) males (triangle) and females (circle). Neurons were segregated based on firing rate as low-spiking (20 Hz, below dotted line) and high-spiking (above dotted line). Only PD females had significantly lower mean low-spiking rates in comparison to female CTs. Left panel: Stereotactic location of recorded pyramidal neurons in the dorsomedial mPFC of CT males (unshaded triangles), PD males (shaded triangles), CT females (unshaded circles), and PD females (shaded circles). Cg1, cingulate area 1; PrL, prelimbic; IL, infralimbic; MO, medial orbital; DP, dorsal peduncular cortex. Bottom numbers represent plate coordinates in mm anterior to bregma (Paxinos and Franklin 2007). Male CT, n = 196; Male PD, n = 111; Female CT, n = 81; Female PD, n = 115. **P < 0.01.

In order to assess the functional integrity of GLU neurotransmission in the mPFC, we evaluated the sensitivity of pyramidal neurons to NMDA that was administered microiontophoretically (Gobbi and Janiri 2006). Under control conditions, the responses to increasing microiontophoretic infusion of NMDA were higher in female than in males (Fig. 7, upper panel). However, in comparison to their respective CTs, the excitatory response of mPFC pyramidal neurons to increasing NMDA currents was significantly enhanced in both PD males (two-way ANOVA: rearing F1,100 = 9.680, P = 0.002; current, F3,100 = 0.595, P = 0.620; interaction, F3,100 = 0.453, P = 0.982) and PD females (two-way ANOVA: rearing F1,36 = 18.661, P < 0.001; current, F3,36 = 7.234, P < 0.001; interaction, F3,36 = 0.066, P = 0.977) (Fig. 7, lower panel).

Figure 7.

Effect of paternal deprivation (PD) on the postsynaptic receptor-mediated excitatory response to N-methyl-d-aspartate of mPFC pyramidal neurons. Upper left inset: Stereotactic location of the recording sites in the mPFC (cingulate and prelimbic regions, layers V–VI; 0.25–0.75 mm lateral to midline, boxed area) and a representation of the complex spike waveform of pyramidal neurons (black bar = 10 ms duration, scaled). Top panels: Line graphs showing between-group difference (father-deprived, PD: black circles; nondeprived controls, CT: white squares) in the response of mPFC pyramidal neurons (ordinate, percent increase in excitatory response) to increasing microiontophoretic currents of NMDA (abscissa), with PD increasing excitatory response in both males (left) and females (right). Bottom panels: Representative integrated firing rate histograms showing the activity of mPFC pyramidal neurons (ordinate, spikes/10 s) plotted against time (abscissa). The response to microiontophoretic currents (values on top of horizontal bars) of NMDA is significantly increased by PD in both males (PD compared with CT) and females (PD compared with CT). N = 6–22/current data point. **P < 0.01.

Figure 7.

Effect of paternal deprivation (PD) on the postsynaptic receptor-mediated excitatory response to N-methyl-d-aspartate of mPFC pyramidal neurons. Upper left inset: Stereotactic location of the recording sites in the mPFC (cingulate and prelimbic regions, layers V–VI; 0.25–0.75 mm lateral to midline, boxed area) and a representation of the complex spike waveform of pyramidal neurons (black bar = 10 ms duration, scaled). Top panels: Line graphs showing between-group difference (father-deprived, PD: black circles; nondeprived controls, CT: white squares) in the response of mPFC pyramidal neurons (ordinate, percent increase in excitatory response) to increasing microiontophoretic currents of NMDA (abscissa), with PD increasing excitatory response in both males (left) and females (right). Bottom panels: Representative integrated firing rate histograms showing the activity of mPFC pyramidal neurons (ordinate, spikes/10 s) plotted against time (abscissa). The response to microiontophoretic currents (values on top of horizontal bars) of NMDA is significantly increased by PD in both males (PD compared with CT) and females (PD compared with CT). N = 6–22/current data point. **P < 0.01.

PD does not Affect Serotonergic Neurotransmission in the mPFC

In order to further explore the neurobiological substrates of the above-described behavioral deficits, we investigated whether 5-HT transmission in the mPFC was altered by PD. Microiontophoretic application of 5-HT in the mPFC mostly produces inhibitory neuronal responses that rely on 5-HT1A receptor activation (Labonte et al. 2009). We assessed the inhibitory responses of 5-HT and found neither between-group (CT vs. PD) nor sex differences (Fig. 8), suggesting that PD-induced behavioral impairments do not depend on 5-HT transmission in the mPFC.

Figure 8.

Effect of paternal deprivation (PD) on the postsynaptic receptor-mediated excitatory response to serotonin (5-HT) of mPFC pyramidal neurons. Upper left inset: Stereotactic location of the recording sites in the mPFC (cingulate and prelimbic regions, layers V–VI; 0.25–0.75 mm lateral to midline, boxed area) and a representation of the complex spike waveform of pyramidal neurons (black bar = 10 ms duration, scaled). Top panels: Line graphs showing an absence of between-group difference (father-deprived, PD: black circles; nondeprived controls, CT: white squares) in the response of mPFC pyramidal neurons (ordinate, percent increase in excitatory response) to increasing microiontophoretic currents of 5-HT (abscissa), observed in both males (left) and females (right). Bottom panels: Representative integrated firing rate histograms showing the activity of mPFC pyramidal neurons (ordinate, spikes/10 s) plotted against time (abscissa). The response to microiontophoretic currents (values on top of horizontal bars) of NMDA was not changed by PD in both males (PD compared with CT) and females (PD compared with CT). N = 4–8/current data point.

Figure 8.

Effect of paternal deprivation (PD) on the postsynaptic receptor-mediated excitatory response to serotonin (5-HT) of mPFC pyramidal neurons. Upper left inset: Stereotactic location of the recording sites in the mPFC (cingulate and prelimbic regions, layers V–VI; 0.25–0.75 mm lateral to midline, boxed area) and a representation of the complex spike waveform of pyramidal neurons (black bar = 10 ms duration, scaled). Top panels: Line graphs showing an absence of between-group difference (father-deprived, PD: black circles; nondeprived controls, CT: white squares) in the response of mPFC pyramidal neurons (ordinate, percent increase in excitatory response) to increasing microiontophoretic currents of 5-HT (abscissa), observed in both males (left) and females (right). Bottom panels: Representative integrated firing rate histograms showing the activity of mPFC pyramidal neurons (ordinate, spikes/10 s) plotted against time (abscissa). The response to microiontophoretic currents (values on top of horizontal bars) of NMDA was not changed by PD in both males (PD compared with CT) and females (PD compared with CT). N = 4–8/current data point.

PD-Induced Behavioral Deficits are Associated with Abnormal Synaptic Processing of Dopamine in the mPFC

In males, low DA currents (5–30 nA) slightly decreased baseline mPFC pyramidal activity, but with no significant difference between CT and PD males (Fig. 9). In females, however, microiontophoretic ejections of DA produced a current-dependent increase in pyramidal activity. Most interestingly, significantly lower excitatory responses were recorded in mPFC neurons of PD females compared with CT females (two-way ANOVA: rearing, F1,42 = 6.825, P = 0.012; current, F3,42 = 4.272, P = 0.01; interaction, F3,42 = 0.849, P = 0.475; Fig. 9).

Figure 9.

Effect of paternal deprivation (PD) on the postsynaptic receptor-mediated excitatory response to dopamine (DA) in mPFC pyramidal neurons. Upper left inset: Stereotactic location of the recording sites in the mPFC (cingulate and prelimbic regions, layers V–VI; 0.25–0.75 mm lateral to midline, boxed area) and a representation of the complex spike waveform of pyramidal neurons (black bar = 10 ms duration, scaled). Top panels: Line graphs showing between-group difference (significant attenuation after PD) in the response of mPFC pyramidal neurons to increasing microiontophoretic currents of DA occurring in females (right) but not in males (left). Bottom panels: Representative integrated firing rate histograms showing the significantly blunted response of mPFC pyramidal neurons to microiontophoretic currents of DA in PD females (compared with CT) but not in males. N = 4–21/current data point **P < 0.01.

Figure 9.

Effect of paternal deprivation (PD) on the postsynaptic receptor-mediated excitatory response to dopamine (DA) in mPFC pyramidal neurons. Upper left inset: Stereotactic location of the recording sites in the mPFC (cingulate and prelimbic regions, layers V–VI; 0.25–0.75 mm lateral to midline, boxed area) and a representation of the complex spike waveform of pyramidal neurons (black bar = 10 ms duration, scaled). Top panels: Line graphs showing between-group difference (significant attenuation after PD) in the response of mPFC pyramidal neurons to increasing microiontophoretic currents of DA occurring in females (right) but not in males (left). Bottom panels: Representative integrated firing rate histograms showing the significantly blunted response of mPFC pyramidal neurons to microiontophoretic currents of DA in PD females (compared with CT) but not in males. N = 4–21/current data point **P < 0.01.

Discussion

In the present study, we demonstrate that PD in California mice, particularly during critical developmental periods, leads to impaired social and behavioral functions in adults. PD-induced behavioral impairments were more pronounced in females and were associated with modifications in DA and GLU neurotransmission in the mPFC, an area long propounded as essential to normal psycho-affective and social development.

PD particularly increased initial mutual contact latencies and aggressive episodes in females. Social investigation was also impaired, as indicated by significant reductions in body sniffing, trailing, and crawling-over. Our data suggest that these social impairments were neither a result of alterations in impulse control nor from increased anxiety, because anxiety-like behaviors and locomotor activation in the OF test were unaffected by PD. Social deficits were also unlikely to have resulted from a dysfunctional switching to evasive behavior because PD failed to influence active social avoidance, while dramatically increasing passive contact. PD animals, notably females, were also sensitized to the locomotor-activating effects of amphetamine, suggesting that DA neurotransmission might contribute to impairments in social behavior in female PD mice. These data are of particular interest since, in contrast, repeated maternal separation, which mimics early-life deprivation, has shown controversial and equivocal outcomes on different measures of stress, cognition, social behavior, and hypothalamic–pituitary–adrenal axis regulation (Millstein and Holmes 2007; Hulshof et al. 2011).

An interesting facet of our data is that, under the testing conditions adopted (same-sex dyad; neutral, nonhome cage environment), the observed social impairments were more profound in females. PD females exhibited most behavioral abnormalities in the SI test regardless of their pairing with another PD or CT female. In contrast, PD males showed reduced social investigation and increased passive contact only when matched with another PD mouse. These observations appear to be consistent with those observed among human patients with social cognitive and personality disorders (such as antisocial personality disorder), whereby symptoms may be maintained by mutually reinforcing SIs (Russell and Hersov 1983). We also observed dramatically greater episodes of aggressive behavior in match-paired PD–PD females than in other pairings, suggesting that females are more sensitive to PD. It has been reported that paternal behaviors occurring later during the preweaning stage, such as pup retrieving and grabbing but not huddling and grooming, positively correlate with aggressiveness (Bester-Meredith et al. 1999; Bester-Meredith and Marler 2001, 2003; Frazier et al. 2006). The fact that the observed increase in offensive behavior was exhibited only by PD–PD matched females suggests that these behaviors were most likely aggressive rather than play-fighting. In keeping with these findings, Trainor et al. (2010, 2011, 2013) showed that, under a significant stress load, female California mice unlike their male counterparts show a decrease in SI and an increase in aggressive behavior. On the other hand, Frazier et al. (2006) found that experimentally increasing paternal retrieval behavior leads to increased territorial aggression, with shorter attack latencies in both male and female offsprings in the resident-intruder paradigm. However, this effect was within a normal range of variation and was not observed in a neutral environment. Decreased paternal grooming also led to enhanced levels of corticosterone.

It is also conceivable that PD-induced female aggression and social deficits are exacerbated by a lack of social play stimulation in the absence of the father. Social play, including play-fighting (boxing/wresting and pinning), which peaks before early puberty, contributes to the development of adult social competence in rodents (Bell et al. 2009, 2010). Although, both the father and the mother may participate in social play (Wilson and Kleiman 1974), fathers exhibit greater propensities for it than mothers, as demonstrated in rodents (Guerra et al. 1999; Becker et al. 2005) and primates (Redican and Mitchell 1973). Parental absence or low parental licking and grooming experience results in altered play behavior throughout the weaning period, but appears to drive male rodent offsprings to compensate in social play by increasing initiations and thus solicit more playful interactions (Becker et al. 2005; Parent and Meaney 2008).

Some effects observed in offsprings may not necessarily be directly related to the absence of the father, but indirectly to the stress imposed on the mother by the father's absence (Gubernick and Alberts 1987; Gubernick and Teferi 2000). Our data do not rule out this possibility. We note, however, that from the delivery to the weaning of pups we did not observe any alteration in the mothers' overt behavior that might be consistent with stress-induced effects (data not published, behavior was observed daily for 30 min, comparing gross behavior in single mothers vs. coupled mothers). These effects may therefore occur under conditions of low resource availability and high-foraging demand, which have been shown to affect parenting strategies and offspring development (Bredy et al. 2007). Remarkably, as mentioned before, California mouse females do not typically compensate for mate (father) absence with increased maternal care (Dudley 1974; Bester-Meredith and Marler 2003), suggesting that the impact of altered maternal behavior over PD animals is minimal.

Overall, the observed PD-induced behavioral deficits are consistent with epidemiological studies in children raised without a father, highlighting an increased risk for deviant behavior and criminal activity, substance abuse, impoverished educational performance and mental illness. Accordingly, the direct engagement of the father with the child, including playful interaction, has been found to reliably predict later positive childhood outcomes, intellectual and linguistic competence, or decreases in adolescent delinquency even after accounting for the mother's contributions (Coley and Medeiros 2007; Sarkadi et al. 2008; Cabrera et al. 2009; Lamb 2010). A positive father–child interaction in early life or during adolescence has been documented to influence children's prosocial development, predicting later popularity, social skills, peer relationship competence, and spousal relationship adjustment (Gottman et al. 1997; Lieberman et al. 1999; Rah and Parke 2008; Lamb 2010). The notion that females, compared with males, are more profoundly affected by low paternal care has also been supported by a stronger association with adult antisocial personality traits (Reti et al. 2002).

Our anatomical investigations revealed dense innervations of GLUergic, 5-HTergic, and DAergic fibers in the prelimbic and cingulate regions of the mPFC. 5-HTergic fibers are uniformly dense throughout the mPFC, while DAergic fibers are most dense in layer VI. This suggests that the activity of mPFC pyramidal neurons is greatly regulated by GLU, DA, and 5-HT transmission via their postsynaptic cognate receptors expressed on these neurons. A significant perturbation in the signaling of these transmitters is a parsimonious explanation for the observed aberrations in the sensitivity of these receptors examined here. Indeed, our electrophysiological findings suggest that impairments in social behavior and potentiation of aggressive behavior are underpinned by modifications in the function of both DA and GLU, but not of 5-HT, synapses in the mPFC. The lack of effect on 5-HT is consistent with the lack of effect on anxiety-like behaviors, in which 5-HT plays a major modulatory role. On the other hand, cortical DAergic and GLUergic systems are engaged in a close functional crosstalk, and evidence for a role of DA on social behavior and aggression has accumulated over the years (Baskerville and Douglas 2010). As DA and NMDA receptors also exert organizational functions in brain development, aberrations of these transmitter systems at any critical time point, following early-life stress and/or parental neglect, could persistently perturb their integrity in adulthood and consequently their behavioral response to social stimuli (Frederick and Stanwood 2009; Baskerville and Douglas 2010).

PD-induced reductions in mPFC pyramidal response to DA, which were evident in females, occurred in parallel with significant deficits in social behavior and increases in aggressive behavior, and more notably with an enhanced sensitization to amphetamine. The concordance of these behavioral and neurobiological abnormalities supports the fact that the mPFC may serve as a central junction where DA signals conveying stress adaptation, social motivation and reward are simultaneously processed, and that disruption of one pathway may disturb the others (Aragona et al. 2007). The decreased basal and DA-evoked pyramidal excitability in PD females points to a functionally hypoactive mPFC that may be argued to undermine both prefrontal facilitation of prosocial behavior and inhibitory control over drug-seeking behavior. Such hypoactive mPFC may have been brought about by a desensitization/downregulation of pyramidal D1 receptors and/or upregulation of pyramidal D2 receptors, thus disturbing the balance of D1 and D2 activity that exert opposite effects on neural excitability (Tseng and O'Donnell 2004). Indeed, pharmacological activation of D1 receptors in the PFC, but not in the striatum, enhances social cognition (Di Cara et al. 2007; Loiseau and Millan 2009), while intra-mPFC infusion of D1 antagonists increases nucleus accumbens-dependent stress response (Doherty and Gratton 1992). Likewise, early social isolation, as well as psychostimulant challenge, have been found to increase 1) D2 receptor expression in mPFC (Han et al. 2012), 2) D2 intracellular activation with greater effects in females (Sun et al. 2010), and 3) impairments in D2 function as observed in PFC of psychostimulant-sensitized rats (Kroener and Lavin 2010). In studies employing the social defeat paradigm, in vivo electrophysiological recordings revealed an increased discharge activity in DAergic neurons of the ventral tegmental area from stress-vulnerable animals, an effect also associated with a socially withdrawn phenotype (Krishnan et al. 2007; Cao et al. 2010). Interestingly, PFC DAergic transmission between male and female CTs is clearly different, and that PD in females decreases DA receptor sensitivity to the level of male CTs. This difference between males and females might be explained by sex-dependent variations in D1 and D2 receptor density in the mPFC, as suggested by D1-like receptor binding being greater in females than in males in the mPFC of monogamous prairie voles, while D2-like receptor binding being greater in males (Smeltzer et al. 2006).

Finally, we noted that the excitatory response of mPFC neurons to NMDA was significantly enhanced in PD animals. This response profile likely reflects a compromised integrity of pyramidal neuronal synapses because the basal firing rate of the low-firing subpopulation of mPFC pyramidal neurons were significantly reduced in females, which appeared particularly vulnerable to PD in the SI test. Indeed, sensitized GLUergic activity or upregulation of NMDA receptor subunits in the mPFC are induced after glucocorticoid administration, following chronic stress (Martin and Wellman 2011) or by acute or chronic psychostimulant exposure (Russo et al. 2010). Changes in NMDA receptors also correlate with synaptic remodeling and dendritic atrophy in the mPFC of stressed animals (Martin and Wellman 2011). The hypothesis that neuroplastic changes may result from PD is additionally supported by findings of significant reductions in apical spine length and number of pyramidal neurons in the PFC of Octodon degus, another monogamous murid species (Ovtscharoff et al. 2006; Helmeke et al. 2009). The sex-dependent impact of PD on mPFC behavioral and neurophysiological integrity seems to diverge from recent findings regarding the lack of sexual dimorphism in the PFC of monogamous rodents (Kingsbury et al. 2012), although dimorphism in chemoarchitecture cannot be ruled out. As such, California mice may be far from displaying sex differences in emotional reactivity and in response to stress (Kingsbury et al. 2012). However, some monogamous species like the prairie vole do exhibit sexually dimorphic structural, hodological, or functional features of the PFC (Kingsbury et al. 2012), as may be the case with California mice. Indeed, female California mice relative to males exhibit glucocorticoid hyper-responsiveness (Trainor et al. 2010, 2011, 2013). This could be attributed to extrahypothalamic structures modulating the neuroendocrine response to stress. Indeed, along with the hippocampus, the prelimbic and cingulate mPFC are known to inhibit the hypothalamic–pituitary adrenal axis and negatively regulate corticosterone release (Radley et al. 2006), and that this brain stress axis is particularly sensitive in female California mice, an area that could be a subject of further investigation.

In summary, our results emphasize the importance of the father during critical neurodevelopmental periods, and that father absence induces impairments in social behavior that persist into adulthood, deficits which are associated with sex-dependent dysregulation of neurotransmission in the mPFC.

Funding

This work was supported by salaries from the Fonds de la Recherche en Santé du Québec (FRSQ) (G.G., F.R.B.) and fellowships and fund from the McGill University Health Center, McGill University Faculty of Medicine (G.G., F.R.B.).

Notes

A special thanks to Dr Michael Meaney who offered the California mouse colony to us, and Dr Guy Debonnel for his encouragement and scientific support. We extend our gratitude to Dr Sergio Dominguez-Lopez and Ms Rebecca Howell for their assistance during the immunohistochemical experiment, and to Dr Jose N. Nobrega and Mr Jean-Philippe Garant for their valuable feedback and suggestions for the manuscript. Conflict of Interest: None declared.

References

Aragona
BJ
Detwiler
JM
Wang
Z
.
2007
.
Amphetamine reward in the monogamous prairie vole
.
Neurosci Lett
 .
418
(2)
:
190
194
.
Bambico
FR
Cassano
T
Dominguez-Lopez
S
Katz
N
Walker
CD
Piomelli
D
Gobbi
G
.
2010a
.
Genetic deletion of fatty acid amide hydrolase alters emotional behavior and serotonergic transmission in the dorsal raphe, prefrontal cortex, and hippocampus
.
Neuropsychopharmacology
 .
35
(10)
:
2083
2100
.
Bambico
FR
Nguyen
NT
Katz
N
Gobbi
G
.
2010b
.
Chronic exposure to cannabinoids during adolescence but not during adulthood impair emotional behaviour and monoaminergic neurotransmission
.
Neurobiol Dis
 .
37
(3)
:
641
655
.
Barthó
P
Hirase
H
Monconduit
L
Zugaro
M
Harris
KD
Buzsáki
G
.
2004
.
Characterization of neocortical principal cells and interneurons by network interactions and extracellular features
.
J Neurophysiol
 .
92
(1)
:
600
608
.
Baskerville
TA
Douglas
AJ
.
2010
.
Dopamine and oxytocin interactions underlying behaviors: potential contributions to behavioral disorders
.
CNS Neurosci Ther
 .
16
(3)
:
e92
e123
.
Becker
K
Helmeke
C
Nowak
C
Bredy
TW
Braun
K
.
2005
.
Fathers shape social behavior and synaptic composition in the limbic system of their offspring
.
Society for Neuroscience
,
Washington
, DC, Online, Abstract Viewer/Itinerary Planner, Program #420.12
.
Bell
HC
McCaffrey
DR
Forgie
ML
Kolb
B
Pellis
SM
.
2009
.
The role of the medial prefrontal cortex in the play fighting of rats
.
Behav Neurosci
 .
123
(6)
:
1158
1168
.
Bell
HC
Pellis
SM
Kolb
B
.
2010
.
Juvenile peer play experience and the development of the orbitofrontal and medial prefrontal cortices
.
Behav Brain Res
 .
207
(1)
:
7
13
.
Bester-Meredith
JK
Marler
CA
.
2003
.
The association between male offspring aggression and paternal and maternal behavior of Peromyscus mice
.
Ethology
 .
109
:
797
808
.
Bester-Meredith
JK
Marler
CA
.
2001
.
Vasopressin and aggression in cross-fostered California mice (Peromyscus californicus) and white-footed mice (Peromyscus leucopus)
.
Horm Behav
 .
40
(1)
:
51
64
.
Bester-Meredith
JK
Young
LJ
Marler
CA
.
1999
.
Species differences in paternal behavior and aggression in peromyscus and their associations with vasopressin immunoreactivity and receptors
.
Horm Behav
 .
36
(1)
:
25
38
.
Bhardwaj
SK
Cassidy
CM
Srivastava
SK
.
2006
.
Changes in syntaxin-1B mRNA in the nucleus accumbens of amphetamine-sensitized rats
.
Int J Neuropsychopharmacol
 .
9
:
751
759
.
Bowlby
J
.
1978
.
Attachment theory and its therapeutic implications
.
Adolesc Psychiatry
 .
6
:
5
33
.
Bredy
TW
Brown
RE
Meaney
MJ
.
2007
.
Effect of resource availability on biparental care, and offspring neural and behavioral development in the California mouse (Peromyscus californicus)
.
Eur J Neurosci
 .
25
(2)
:
567
575
.
Bredy
TW
Lee
AW
Meaney
MJ
Brown
RE
.
2004
.
Effect of neonatal handling and paternal care on offspring cognitive development in the monogamous California mouse (Peromyscus californicus)
.
Horm Behav
 .
46
(1)
:
30
38
.
Cabrera
NJ
Shannon
J
Mitchell
S
West
J
.
2009
.
Mexican American mothers and fathers' prenatal attitudes and father prenatal involvement: links to mother-infant interaction and father engagement
.
Sex Roles
 .
60
(7–8)
:
510
526
.
Cao
JL
Covington
HE
3rd
Friedman
AK
Wilkinson
MB
Walsh
JJ
Cooper
DC
Nestler
EJ
Han
MH
.
2010
.
Mesolimbic dopamine neurons in the brain reward circuit mediate susceptibility to social defeat and antidepressant action
.
J Neurosci
 .
30
(49)
:
16453
16458
.
Cassano
T
Gaetani
S
Macheda
T
Laconca
L
Romano
A
Morgese
MG
Cimmino
CS
Chiarotti
F
Bambico
FR
Gobbi
G
et al
2010
.
Evaluation of the emotional phenotype and serotonergic neurotransmission of fatty acid amide hydrolase-deficient mice
.
Psychopharmacology (Berl)
 .
214
(2)
:
465
476
.
Choleris
E
Thomas
AW
Kavaliers
M
Prato
FS
.
2001
.
A detailed ethological analysis of the mouse open field test: effects of diazepam, chlordiazepoxide and an extremely low frequency pulsed magnetic field
.
Neurosci Biobehav Rev
 .
25
(3)
:
235
260
.
Coley
RL
Medeiros
BL
.
2007
.
Reciprocal longitudinal relations between nonresident father involvement and adolescent delinquency
.
Child Dev
 .
78
(1)
:
132
147
.
Cox
KH
Rissman
EF
.
2011
.
Sex differences in juvenile mouse social behavior are influenced by sex chromosomes and social context
.
Genes Brain Behav
 .
10
(4)
:
465
472
.
de Jong
TR
Korosi
A
Harris
BN
Perea-Rodriguez
JP
Saltzman
W
.
2012
.
Individual variation in paternal responses of virgin male California mice (Peromyscus californicus): behavioral and physiological correlates
.
Physiol Biochem Zool
 .
85
(6)
:
740
751
.
Di Cara
B
Panayi
F
Gobert
A
Dekeyne
A
Sicard
D
De Groote
L
Millan
MJ
.
2007
.
Activation of dopamine D1 receptors enhances cholinergic transmission and social cognition: a parallel dialysis and behavioural study in rats
.
Int J Neuropsychopharmacol
 .
10
(3)
:
383
399
.
Doherty
MD
Gratton
A
.
1992
.
High-speed chronoamperometric measurements of mesolimbic and nigrostriatal dopamine release associated with repeated daily stress
.
Brain Res
 .
586
:
295
302
.
D'Souza
DN
Harlan
RE
Garcia
MM
.
2003
.
Modulation of glutamate receptor expression by gonadal steroid hormones in the rat striatum
.
Brain Res Bull
 .
59
(4)
:
289
292
.
D'Souza
DN
Harlan
RE
Garcia
MM
.
1999
.
Sexual dimorphism in the response to N-methyl-D-aspartate receptor antagonists and morphine on behavior and c-Fos induction in the rat brain
.
Neuroscience
 .
93
(4)
:
1539
1547
.
Dudley
D
.
1974
.
Paternal behavior in the California mouse, Peromyscus californicus
.
Behav Biol
 .
11
(2)
:
247
252
.
Frazier
CR
Trainor
BC
Cravens
CJ
Whitney
TK
Marler
CA
.
2006
.
Paternal behavior influences development of aggression and vasopressin expression in male California mouse offspring
.
Horm Behav
 .
50
(5)
:
699
707
.
Frederick
AL
Stanwood
GD
.
2009
.
Drugs, biogenic amine targets and the developing brain
.
Dev Neurosci
 .
31
(102)
:
7
22
.
Gobbi
G
Janiri
L
.
2006
.
Sodium- and magnesium-valproate in vivo modulate glutamatergic and GABAergic synapses in the medial prefrontal cortex
.
Psychopharmacology (Berl)
 .
185
(2)
:
255
262
.
Gobbi
G
Murphy
DL
Lesch
KP
Blier
P
.
2001
.
Modifications of the serotonergic system in mice lacking serotonin transporters: an in vivo electrophysiological study
.
J Pharmacol Exp Ther
 .
296
(3)
:
987
995
.
Gottman
JM
Katz
LF
Hooven
C
.
1997
.
Meta-emotion: how families communicate emotionally
 .
Mahwah, NJ
:
Lawrence Erlbaum Associates
.
Grossmann
K
Grossmann
KE
Fremmer-Bombik
E
Kindler
H
Scheuerer-Englisch
H
Zimmermann
P
.
2002
.
The uniqueness of the child-father attachment relationship: fathers' sensitive and challenging play as the pivotal variable in a 16-year longitudinal study
.
Soc Dev
 .
11
:
307
331
.
Gubernick
DJ
Alberts
JR
.
1987
.
The biparental care system of the California mouse, Peromyscus californicus
.
J Comp Psychol
 .
101
(2)
:
169
177
.
Gubernick
DJ
Teferi
T
.
2000
.
Adaptive significance of male parental care in a monogamous mammal
.
Proc Biol Sci
 .
267
(1439)
:
147
150
.
Guerra
RF
Takase
E
de O Nunes
C
.
1999
.
Play fighting of juvenile golden hamsters (Mesocricetus auratus): effects of two types of social deprivation and days of testing
.
Behav Processes
 .
47
(3)
:
139
151
.
Han
X
Li
N
Xue
X
Shao
F
Wang
W
.
2012
.
Early social isolation disrupts latent inhibition and increases dopamine D2 receptor expression in the medial prefrontal cortex and nucleus accumbens of adult rats
.
Brain Res
 .
1447
:
38
43
.
Harrison
SJ
Nobrega
JN
.
2009
.
Differential susceptibility to ethanol and amphetamine sensitization in dopamine D3 receptor-deficient mice
.
Psychopharmacology (Berl)
 .
204
(1)
:
49
59
.
Haycock
JW
.
1993
.
Multiple forms of tyrosine hydroxylase in human neuroblastoma cells: quantitation with isoform-specific antibodies
.
J Neurochem
 .
60
:
493
502
.
Helmeke
C
Ovtscharoff
W
Jr
Poeggel
G
Braun
K
.
2001
.
Juvenile emotional experience alters synaptic inputs on pyramidal neurons in the anterior cingulate cortex
.
Cereb Cortex
 .
11
(8)
:
717
727
.
Helmeke
C
Seidel
K
Poeggel
G
Bredy
TW
Abraham
A
Braun
K
.
2009
.
Paternal deprivation during infancy results in dendrite- and time-specific changes of dendritic development and spine formation in the orbitofrontal cortex of the biparental rodent Octodon degus
.
Neuroscience
 .
163
(3)
:
790
798
.
Hönack
D
Löscher
W
.
1993
.
Sex differences in NMDA receptor mediated responses in rats
.
Brain Res
 .
620
(1)
:
167
170
.
Huang
J
Pickel
VM
.
2002
.
Serotonin transporters (SERTs) within the rat nucleus of the solitary tract: subcellular distribution and relation to 5HT2A receptors
.
J Neurocytol
 .
31
(8–9)
:
667
679
.
Hulshof
HJ
Novati
A
Sgoifo
A
Luiten
PG
den Boer
JA
Meerlo
P
.
2011
.
Maternal separation decreases adult hippocampal cell proliferation and impairs cognitive performance but has little effect on stress sensitivity and anxiety in adult Wistar rats
.
Behav Brain Res
 .
216
(2)
:
552
560
.
Insel
TR
.
2003
.
Is social attachment an addictive disorder?
Physiol Behav
 .
79
(3)
:
351
357
.
Jablonska
B
Lindberg
L
.
2007
.
Risk behaviours, victimisation and mental distress among adolescents in different family structures
.
Soc Psychiatry Psychiatr Epidemiol
 .
42
(8)
:
656
663
.
Jia
R
Tai
F
An
S
Zhang
X
Broders
H
.
2009
.
Effects of neonatal paternal deprivation or early deprivation on anxiety and social behaviors of the adults in mandarin voles
.
Behav Processes
 .
82
(3)
:
271
278
.
Kaffman
A
Meaney
MJ
.
2007
.
Neurodevelopmental sequelae of postnatal maternal care in rodents: clinical and research implications of molecular insights
.
J Child Psychol Psychiatry
 .
48
(3–4)
:
224
244
.
Kingsbury
MA
Gleason
ED
Ophir
AG
Phelps
SM
Young
LJ
Marler
CA
.
2012
.
Monogamous and promiscuous rodent species exhibit discrete variation in the size of the medial prefrontal cortex
.
Brain Behav Evol
 .
80
(1)
:
4
14
.
Kirkpatrick
B
Kakoyannis
A
.
2004
.
Sexual dimorphism and the NMDA receptor in alloparental behavior in juvenile prairie voles (Microtus ochrogaster)
.
Behav Neurosci
 .
118
(3)
:
584
589
.
Kleiman
DG
Malcolm
JR
.
1981
.
The evolution of male parental investment in mammals
.
Q Rev Biol
 .
52
:
39
68
.
Krishnan
V
Han
MH
Graham
DL
Berton
O
Renthal
W
Russo
SJ
Laplant
Q
Graham
A
Lutter
M
Lagace
DC
et al
2007
.
Molecular adaptations underlying susceptibility and resistance to social defeat in brain reward regions
.
Cell
 .
131
(2)
:
391
404
.
Kroener
S
Lavin
A
.
2010
.
Altered dopamine modulation of inhibition in the prefrontal cortex of cocaine-sensitized rats
.
Neuropsychopharmacology
 .
35
(11)
:
2292
2304
.
Labonte
B
Bambico
FR
Gobbi
G
.
2009
.
Potentiation of excitatory serotonergic responses by MK-801 in the medial prefrontal cortex
.
Naunyn-Schmiedeberg's Arch Pharmacol
 .
380
(5)
:
383
397
.
Lamb
ME
.
2010
.
The role of the father in child development
 .
5th ed. Hoboken, NJ: Wiley
.
Lambert
KG
Franssen
CL
Hampton
JE
Rzucidlo
AM
Hyer
MM
True
M
Kaufman
C
Bardi
M
.
2013
.
Modeling paternal attentiveness: distressed pups evoke differential neurobiological and behavioral responses in paternal and nonpaternal mice
.
Neuroscience
 .
234
:
1
12
.
Lieberman
M
Doyle
AB
Markiewicz
D
.
1999
.
Developmental patterns in security of attachment to mother and father in late childhood and early adolescence: associations with peer relations
.
Child Dev
 .
70
(1)
:
202
213
.
Liu
Y
Aragona
BJ
Young
KA
Dietz
DM
Kabbaj
M
Mazei-Robison
M
Nestler
EJ
Wang
Z
.
2010
.
Nucleus accumbens dopamine mediates amphetamine-induced impairment of social bonding in a monogamous rodent species
.
Proc Natl Acad Sci USA
 .
107
(3)
:
1217
1222
.
Loiseau
F
Millan
MJ
.
2009
.
Blockade of dopamine D(3) receptors in frontal cortex, but not in sub-cortical structures, enhances social recognition in rats: similar actions of D(1) receptor agonists, but not of D(2) antagonists
.
Eur Neuropsychopharmacol
 .
19
(1)
:
23
33
.
Martin
KP
Wellman
CL
.
2011
.
NMDA receptor blockade alters stress-induced dendritic remodeling in medial prefrontal cortex
.
Cereb Cortex
 .
21
(10)
:
2366
2373
.
McCabe
T
Blanchard
B
.
1950
.
Three species of Peromyscus
 .
Santa Barbara, CA
:
Rood Association
.
McFarlane
HG
Kusek
GK
Yang
M
Phoenix
JL
Bolivar
VJ
Crawley
JN
.
2008
.
Autism-like behavioral phenotypes in BTBR T+tf/J mice
.
Genes, Brain Behav
 .
7
(2)
:
152
163
.
McGregor
IS
Callaghan
PD
Hunt
GE
.
2008
.
From ultrasocial to antisocial: a role for oxytocin in the acute reinforcing effects and long-term adverse consequences of drug use?
Br J Pharmacol
 .
154
(2)
:
358
368
.
Millstein
RA
Holmes
A
.
2007
.
Effects of repeated maternal separation on anxiety- and depression-related phenotypes in different mouse strains
.
Neurosci Biobehav Rev
 .
31
(1)
:
3
17
.
Murray
J
Farrington
DP
Sekol
I
.
2012
.
Children's antisocial behavior, mental health, drug use, and educational performance after parental incarceration: a systematic review and meta-analysis
.
Psychol Bull
 .
138
(2)
:
175
210
.
Ovtscharoff
W
Jr
Helmeke
C
Braun
K
.
2006
.
Lack of paternal care affects synaptic development in the anterior cingulate cortex
.
Brain Res
 .
1116
(1)
:
58
63
.
Parent
CI
Meaney
MJ
.
2008
.
The influence of natural variations in maternal care on play fighting in the rat
.
Dev Psychobiol
 .
50
(8)
:
767
776
.
Paxinos
G
Franklin
KBJ
.
2007
.
The mouse brain in stereotaxic coordinates
 .
3rd ed
.
San Diego
:
Academic Press
.
Paxinos
G
Watson
C
.
2007
.
The rat brain in stereotaxic coordinates
 .
6th ed
.
San Diego
:
Academic Press
.
Pinkernelle
J
Abraham
A
Seidel
K
Braun
K
.
2009
.
Paternal deprivation induces dendritic and synaptic changes and hemispheric asymmetry of pyramidal neurons in the somatosensory cortex
.
Dev Neurobiol
 .
69
(10)
:
663
673
.
Radley
JJ
Arias
CM
Sawchenko
PE
.
2006
.
Regional differentiation of the medial prefrontal cortex in regulating adaptive responses to acute emotional stress
.
J Neurosci
 .
26
(50)
:
12967
12976
.
Rah
Y
Parke
RD
.
2008
.
Pathways between parent-child interactions and peer acceptance: the role of children's social information processing
.
Soc Dev
 .
17
:
341
357
.
Redican
WK
Mitchell
G
.
1973
.
A longitudinal study of paternal behavior in adult male rhesus monkeys: I. observations on the first dyad
.
Dev Psychol
 .
8
(1)
:
135
136
.
Reti
IM
Samuels
JF
Eaton
WW
Bienvenu
OJ
3rd
Costa
PT
Jr
Nestadt
G
.
2002
.
Adult antisocial personality traits are associated with experiences of low parental care and maternal overprotection
.
Acta Psychiatr Scand
 .
106
(2)
:
126
133
.
Ribble
D
.
1992
.
Lifetime reproductive success and its correlates in the monogamous rodent, Peromyscus californicus
.
J Anim Ecol
 .
61
:
457
468
.
Ribble
DO
Salvioni
M
.
1990
.
Social organization and nest cooccupancy in Peromyscus californicus, a monogamous rodent
.
Behav Ecol Sociobiol
 .
26
:
9
15
.
Russell
GFM
Hersov
LA
.
1983
.
The neuroses and personality disorders
 .
Cambridge
(
NY
):
Cambridge University Press
.
Russo
SJ
Dietz
DM
Dumitriu
D
Morrison
JH
Malenka
RC
Nestler
EJ
.
2010
.
The addicted synapse: mechanisms of synaptic and structural plasticity in nucleus accumbens
.
Trends Neurosci
 .
33
(6)
:
267
276
.
Sarkadi
A
Kristiansson
R
Oberklaid
F
Bremberg
S
.
2008
.
Fathers' involvement and children's developmental outcomes: a systematic review of longitudinal studies
.
Acta Paediatr
 .
97
(2)
:
153
158
.
Schradin
C
Pillay
N
.
2005
.
The influence of the father on offspring development in the striped mouse
.
Behav Ecol
 .
16
:
450
455
.
Smeltzer
MD
Curtis
JT
Aragona
BJ
Wang
Z
.
2006
.
Dopamine, oxytocin, and vasopressin receptor binding in the medial prefrontal cortex of monogamous and promiscuous voles
.
Neurosci Lett
 .
394
(2)
:
146
151
.
Sun
WL
Festa
ED
Jenab
S
Quinones-Jenab
V
.
2010
.
Sex differences in dopamine D2-like receptor-mediated G-protein activation in the medial prefrontal cortex after cocaine
.
Ethn Dis
 .
20
:
(1 Suppl 1)
:
S1-88
S1-91
.
Swadlow
HA
.
2003
.
Fast-spike interneurons and feedforward inhibition in awake sensory neocortex
.
Cereb Cortex
 .
13
:
25
32
.
Takamori
S
Rhee
JS
Rosenmund
C
Jahn
R
.
2001
.
Identification of differentiation-associated brain-specific phosphate transporter as a second vesicular glutamate transporter (VGLUT2)
.
J Neurosci
 .
21
:
RC182
.
Tanimura
Y
Ogoegbunam
FC
Lewis
MH
.
2009
.
Amphetamine-induced sensitization and spontaneous stereotypy in deer mice
.
Pharmacol Biochem Behav
 .
92
(4)
:
670
675
.
Trainor
BC
Pride
MC
Villalon Landeros
R
Knoblauch
NW
Takahashi
EY
Silva
AL
Crean
KK
.
2011
.
Sex differences in social interaction behavior following social defeat stress in the monogamous California mouse (Peromyscus californicus)
.
PLoS One
 .
6
:
e17405
.
Trainor
BC
Takahashi
EY
Campi
KL
Florez
SA
Greenberg
GD
Laman-Maharg
A
Laredo
SA
Orr
VN
Silva
AL
Steinman
MQ
.
2013
.
Sex differences in stress-induced social withdrawal: independence from adult gonadal hormones and inhibition of female phenotype by corncob bedding
.
Horm Behav
 .
63
(3)
:
543
550
.
Trainor
BC
Takahashi
EY
Silva
AL
Crean
KK
Hostetler
V
.
2010
.
Sex differences in hormonal responses to social conflict in the monogamous California mouse
.
Horm Behav
 .
58
:
506
512
.
Tseng
KY
O'Donnell
P
.
2004
.
Dopamine-glutamate interactions controlling prefrontal cortical pyramidal cell excitability involve multiple signaling mechanisms
.
J Neurosci
 .
24
(22)
:
5131
5139
.
Tyrka
AR
Wier
L
Price
LH
Ross
N
Anderson
GM
Wilkinson
CW
Carpenter
LL
.
2008
.
Childhood parental loss and adult hypothalamic-pituitary-adrenal function
.
Biol Psychiatry
 .
63
(12)
:
1147
1154
.
Waytz
A
Zaki
J
Mitchell
JP
.
2012
.
Response of dorsomedial prefrontal cortex predicts altruistic behavior
.
J Neurosci
 .
32
(22)
:
7646
7650
.
Whatson
TS
Smart
JL
Dobbing
J
.
1974
.
Social interactions among adult male rats after early undernutrition
.
Br J Nutr
 .
32
(2)
:
413
419
.
Whatson
TS
Smart
JL
Dobbing
J
.
1976
.
Undernutrition in early life: lasting effects on activity and social behavior of male and female rats
.
Dev Psychobiol
 .
9
(6)
:
529
538
.
Wilson
SC
Kleiman
DG
.
1974
.
Eliciting play—a comparative study
.
Am Zool
 .
14
:
341
370
.
Wolff
J
Sherman
PW
.
2007
.
Rodent societies: an ecological & evolutionary perspective
 .
Chicago
:
University of Chicago Press
.
Yogman
M
.
1981
.
Games fathers and mothers play with their infants
.
Infant Ment Health J
 .
2
:
241
248
.
Ziabreva
I
Poeggel
G
Schnabel
R
Braun
K
.
2003
.
Separation-induced receptor changes in the hippocampus and amygdala of Octodon degus: influence of maternal vocalizations
.
J Neurosci
 .
23
(12)
:
5329
5336
.