Effect of Epinephrine, Norepinephrine and(or) GnRH on Serum LH in Prepuberal Beef Heifers

Summary

Forty prepuberal Simmental × Brahman-Hereford heifers were utilized to determine the effects of epinephrine (E), norepinephrine (NE), gonadotropin releasing hormone (GnRH) or combinations of GnRH + E and GnRH + NE on serum luteinizing hormone (LH) concentrations. Animals were assigned randomly to one of five treatments with four replicates/treatment. Treatments consisted of I) 100 µg GnRH at time 0 (n = 8); II) 50 mg NE at time −15 and 0 (n = 8); III) 50 mg E at time −15 and 0 (n = 8); IV) 100 µg GnRH at time 0, plus 50 mg NE at time −15 and 0 (n = 8) and V) 100 µg GnRH at time 0, plus 50 mg E at time −15 and 0 (n = 8). All treatment compounds were administered im in 2 ml physiological saline and blood samples were collected via tail vessel puncture at −30, −15, 0, 15, 30, 45, 60, 90, 120, 180, 240, 300 and 360 min from GnRH injection. Treatment with NE or E alone had no effect (P>.10) on serum LH during the sampling period. The initial LH release to GnRH was altered (P<.05) by concomitant treatment with NE (treatment IV) or E (treatment V). Magnitude of the LH release was reduced (P<.01) by treatment V. Area under the LH surge was reduced (P<.05) by treatment IV (NE) and V (E).

Epinephrine, Norepinephrine, Adrenal, Stress, Luteinizing Hormone, Heifer

© American Society of Animal Science 1983