The effect of intravenous infusion of gonadotrophin inhibitory hormone (GnIH) on luteinising hormone (LH) secretion in male sheep

Research output: Other contribution to conferencePoster

Abstract

In the ewe, GnIH acts to inhibit the synthesis and secretion of the gonadotrophins from the anterior pituitary via regulation of gonadotrophin releasing hormone secretion and directly at the pituitary gland. The situation in rams has not been investigated. We tested the hypothesis that intravenous administration of GnIH will decrease LH secretion in the merino ram.
In an initial study, intact rams (n=8) were infused with either GnIH or saline in a cross over design. Blood samples were collected every 10 minutes during a 4 hour pre-infusion period, during the infusion (1mg GnIH in 2ml saline over 2 hours, following a bolus 1mg priming dose of GnIH) and during a 3 hour post infusion period. In a second study, 9 rams were castrated 3 weeks prior to GnIH infusion and the experiment run as previously, except that two different sources of GnIH were used and the dose of GnIH increased by infusing 1mg over 1 hour. Each animal received each treatment (GnIH1, GnIH2 and saline) in random order at 3 days intervals. In both studies, no significant differences were seen between treatments, these results demonstrated that in both intact and castrated rams, GnIH may not be a potent inhibitor for LH secretion in the male sheep. Seasonal and nutritional factors may have had a part to play in this study, and should be considered.
This study suggests GnIH may play a small role in regulating LH secretion in rams however further investigation is needed in the mechanisms of this role in the testosterone negative feedback system.
Original languageEnglish
Publication statusPublished - 16 Aug 2014

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