Gonadotropin releasing hormone (GnRH) affects precopulatory behavior in testosterone-treated geldings.
Twelve pony geldings with (n = 6) and without (n = 6) testosterone replacement (200 micrograms/kg testosterone propionate in oil, SC every 48 hours) received either gonadotropin releasing hormone (GnRH; 25 micrograms SC every 3 hours) or control treatment. Sexual behavior was recorded during 4-minute exposure to an estrous mare, 3 times weekly for 2 weeks before treatment, 3 weeks during treatment, and 3 weeks after treatment had been discontinued. The group receiving testosterone and GnRH (n = 3) exhibited significantly greater flehmen response frequency and attention duration and significantly lower vocalization frequency and erection duration than the group receiving only testosterone (n = 3). GnRH had no apparent effect on sexual behavior in geldings without testosterone replacement (n = 3). These results support an hypothesis of testosterone-dependent, CNS-mediated effects of GnRH on precopulatory behavior in the stallion.
McDonnell
S M
SM
Hofmann Research Center for Reproductive Studies, University of Pennsylvania School of Veterinary Medicine, Kennett Square, PA 19348.
Diehl
N K
NK
Garcia
M C
MC
Kenney
R M
RM
D000818:Animals; D003307:Copulation / Q000502:physiology*; D006736:Horses; D008297:Male; D009919:Orchiectomy; D010410:Penile Erection; D010906:Pituitary Hormone-Releasing Hormones / Q000502:physiology*; D012726:Sexual Behavior, Animal / Q000502:physiology; D013739:Testosterone / Q000502:physiology*
D010906:Pituitary Hormone-Releasing Hormones; D013739:Testosterone