Induction of ovulation in anestrous mares with pulsatile administration of gonadotropin-releasing hormone.
Four seasonally anestrous mares (Standardbred), housed under a nonstimulatory photoperiod of 8 hours light:16 hours dark, were administered gonadotropin-releasing hormone (GnRH) in a pulsatile pattern (50 or 250 micrograms of GnRH/hour) for 8 to 18 days during February and March 1985. Treatment with GnRH, irrespective of dose or month, induced an increase in serum luteinizing hormone from a mean pretreatment value typical of anestrus (0.58 +/- 0.02 ng/ml +/- SE) to 10.84 +/- 1.27 ng/ml on day 8 of GnRH treatment. Ovulation in the 4 mares occurred 8.8 +/- 0.7 days after the initiation of pulsatile GnRH administration. In each instance, ovulation was followed by a functional corpus luteum, as indicated by a luteal phase (defined as the number of days on which serum levels of progesterone were greater than 1.0 ng/ml) which lasted 14.5 +/- 0.6 days. These results indicate that infusion of GnRH in a pulsatile pattern is effective in inducing follicular development and ovulation in anestrous mares in the absence of a stimulatory photoperiod.
D000780:Anestrus / Q000187:drug effects*; D000818:Animals; D004971:Estrus / Q000187:drug effects*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D006736:Horses / Q000502:physiology*; D007986:Luteinizing Hormone / Q000097:blood; D010062:Ovulation Induction / Q000662:veterinary*; D011374:Progesterone / Q000097:blood
D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D007986:Luteinizing Hormone