Author:
BRINSKO STEVEN P.,SQUIRES EDWARD L.,PICKETT BILL W.,NETT TERRY M.
Abstract
ABSTRACT: The objective of this study was to determine if prolonged pulsatile administration of homologous gonadotropin‐releasing hormone (GnRH) at therapeutic or 5x therapeutic doses would cause down‐regulation of the stallion's hypothalamic‐pituitary‐testicular axis. Fifteen stallions were randomly assigned to three treatment groups (n = 5/group) and received a 0.5 ml subcutaneous dose of saline (group 1), 50 μg GnRH (group 2), or 250 μg GnRH (group 3) every 2 hours for 75 days. Weekly evaluations of follicle stimulating hormone, luteinizing hormone, and testosterone and monthly evaluations of daily sperm output and spermatozoal motility failed to demonstrate any decreased pituitary or gonadal responsiveness within or among treatment groups (P > 0.1) as a result of treatment with GnRH. Results of this study demonstrate that the hypothalamic‐pituitary‐testicularaxis of the stallion, unlike that of other domestic species, is remarkably refractory to GnRH‐induced down‐regulation.
Subject
Urology,Endocrinology,Reproductive Medicine,Endocrinology, Diabetes and Metabolism
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