Comparison of the effects of N-methyl-DL-aspartic acid on gonadotropin and prolactin secretion in anestrous mares and mares exhibiting estrous cycles during anestrus.
Abstract: This study investigated the hypothesis that for a subpopulation of horse mares continuation of estrous cycles during the nonbreeding season may be attributed to continued stimulatory glutamatergic activity on GnRH-secreting neurons. The gonadotropin response to the glutamatergic agonist N-methyl-DL-aspartic acid (NMA) was compared in cycling and anestrous mares during the nonbreeding season. It was anticipated that the gonadotropin response to NMA in cycling mares would be attenuated, compared with that of anestrous mares. The experiment used 16 anestrous mares and 15 mares that cycled during the nonbreeding season. The effect of NMA on prolactin secretion was also evaluated. In addition, the seasonal rhythm of prolactin secretion was compared in anestrous and cycling mares during October-April. In cycling mares, the response to NMA was dependent on the stage of the cycle, and a significantly (p < 0.05) larger proportion responded during the luteal phase (6 of 8), compared with the follicular phase (1 of 7 mares). The proportion of anestrous mares that responded to NMA was similar to that of cycling mares during the luteal phase, but larger than during the follicular phase. In anestrous and cycling mares, NMA suppressed prolactin secretion, and in both groups prolactin secretion decreased during the nonbreeding season. Thus, we conclude that differences in reproductive activity in mares during the nonbreeding season are unlikely to reflect a change in glutamatergic activity.
Publication Date: 1997-07-01 PubMed ID: 9209077DOI: 10.1095/biolreprod57.1.36Google Scholar: Lookup
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- Comparative Study
- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research delves into whether continued estrous cycles in non-breeding horse mares are linked to on-going stimulatory glutamatergic activity on GnRH-secreting neurons. The findings hint that differences in reproductive activity in these mares during the nonbreeding season do not necessarily reflect variability in glutamatergic activity.
Objective of the Research
- The research aimed to investigate the claim that stimulatory glutamatergic activity on GnRH-secreting neurons is responsible for some horse mares continuing with their estrous cycles even in nonbreeding seasons.
Research Methodology and Participants
- The team compared the gonadotropin response to N-methyl-DL-aspartic acid (NMA), a glutamatergic agonist, in both cycling and non-cycling (anestrous) mares during the nonbreeding season.
- The research involved 16 non-cycling (anestrous) mares and 15 mares that continued with their estrous cycles during the nonbreeding season.
Experiment Findings
- In mares that continued with their cycles, the effects of NMA were dependent on the stage of their cycle, with a larger proportion responding during the luteal phase compared to the follicular phase.
- The response to NMA amongst the anestrous mares was similar to the response of those in the luteal phase and more than those in the follicular phase.
- NMA suppressed prolactin secretion in both groups of mares, and prolactin secretion in both groups dropped during the nonbreeding season.
Conclusion of the Study
- The research concluded that observable differences in reproductive activity among mares during the nonbreeding season are unlikely to be due to alterations in glutamatergic activity.
Cite This Article
APA
Fitzgerald BP, Davison LA.
(1997).
Comparison of the effects of N-methyl-DL-aspartic acid on gonadotropin and prolactin secretion in anestrous mares and mares exhibiting estrous cycles during anestrus.
Biol Reprod, 57(1), 36-42.
https://doi.org/10.1095/biolreprod57.1.36 Publication
Researcher Affiliations
- Department of Veterinary Science, Maxwell Gluck Equine Research Center, University of Kentucky, Lexington 40546-0099, USA. bfitz@pop.uky.edu
MeSH Terms
- Anestrus / drug effects
- Anestrus / physiology
- Animals
- Estrus / drug effects
- Estrus / physiology
- Excitatory Amino Acid Agonists / pharmacology
- Female
- Follicle Stimulating Hormone / metabolism
- Follicular Phase / drug effects
- Follicular Phase / physiology
- Horses / physiology
- Luteal Phase / drug effects
- Luteal Phase / physiology
- Luteinizing Hormone / metabolism
- N-Methylaspartate / analogs & derivatives
- N-Methylaspartate / pharmacology
- Prolactin / metabolism
- Seasons
Citations
This article has been cited 2 times.- Di Fiore MM, Boni R, Santillo A, Falvo S, Gallo A, Esposito S, Baccari GC. D-Aspartic Acid in Vertebrate Reproduction: Animal Models and Experimental Designs(‡).. Biomolecules 2019 Sep 3;9(9).
- Ferreira SA, Browning DA, Scott CJ, Kuehl DE, Jackson GL. Effect of infusing gamma-aminobutyric acid receptor agonists and antagonists into the medial preoptic area and ventromedial hypothalamus on prolactin secretion in male sheep.. Endocrine 1998 Dec;9(3):303-12.
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