PULSE ADMINISTRATION OF ESTRADIOL-17β CANCELS SEX DIFFERENCE IN BEHAVIORAL ESTROGEN SENSITIVITY

No sex differences were found in the capability of estradiol-17β (E₂) to induce female sexual behaviors in adult gonadectomized rats when it was administered oy a pulsatile schedule and followed by progesterone. Administration of E₂ in constant-release implants resulted in a clear behavioral sex difference, with females snowing higher levels than males. The ovaries of proestrous females were shown to secrete E₂ in a pulsatile manner and the schedule of E₂ administration which cancelled the behavioral sex difference produced pulses of serum E2 of an amplitude which was within the physiological range. Thus, the sex difference in behavioral E₂ sensitivity is dependent upon the manner of E₂ administration and if a physiological schedule of E₂ administration is employed the sex difference is cancelled.