Effects of administration of N-methyl-D,L-aspartate (NMA) on gonadotropin secretion in untreated and steroid-treated ovariectomized mares during the breeding season and in intact and ovariectomized mares during anestrus.
Abstract: The purpose of this experiment was to investigate whether N-methyl-D,L-aspartate stimulated gonadotropin secretion in mares and to determine the response in two experimental paradigms where gonadotropin secretion is low or elevated. In Experiment 1, conducted during the breeding season (summer), eight long-term ovariectomized mares were treated daily for 21 d with progesterone plus estradiol (n = 4) or oil vehicle. Beginning on Day 14, each mare received, in a randomized design on alternate days, an intravenous injection of either 0, 0.5, 1.0, or 5.0 mg/kg NMA. Treatment with NMA was not accompanied by a change in gonadotropin release in vehicle-treated ovariectomized mares. In steroid-treated mares, gonadotropin values were suppressed compared with vehicle controls, but NMA only induced a significant increase in follicle-stimulating hormone (FSH) and only at the highest dose. In Experiment 2, the effect of the administration of NMA was compared in intact anestrous mares (n = 4) and long-term ovariectomized mares (n = 4) during the nonbreeding season. At the highest doses (1.0 and 5.0 mg/kg), NMA induced a significant increase in luteinizing hormone (LH) and FSH in intact mares. In contrast, pretreatment concentrations of LH and FSH were higher in long-term ovariectomized mares and NMA only increased LH, but not FSH, at the highest dose. The results demonstrate that the administration of NMA stimulates the release of LH and FSH in mares. During anestrus, ovarian intact mares appear more responsive than long-term ovariectomized mares. At high doses, NMA may induce differential release of the gonadotropins in long-term ovariectomized mares.
Publication Date: 1996-05-01 PubMed ID: 8738862DOI: 10.1016/0739-7240(96)00016-1Google Scholar: Lookup
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- Comparative Study
- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research investigates the effect of N-methyl-D,L-aspartate (NMA) on the secretion of gonadotropins in mares. It explores whether NMA stimulates the hormone secretion in different conditions related to mare reproductive status and the dosages administered.
Objective and Methodology of the Experiments
- The experiment aimed to understand if N-methyl-D,L-aspartate (NMA) stimulates gonadotropin secretion in mares and to gauge the effect under two paradigms, where gonadotropin secretion is either low or elevated.
- The study was conducted in two parts – Experiment 1 was conducted during the breeding season. It involved eight long-term ovariectomized mares who were treated with progesterone plus estradiol or oil vehicle daily for 21 days. From Day 14, they received intravenous injections of various doses of NMA in a randomized design on alternate days.
- Experiment 2 involved a comparison of the NMA administration effect in intact anestrous mares and long-term ovariectomized mares during the non-breeding season.
Findings of the Experiments
- Experiment 1’s results showed no change in gonadotropin release in ovariectomized mares treated with the NMA vehicle. In steroid-treated mares, gonadotropin values were suppressed compared to vehicle controls, but NMA only triggered a significant increase in follicle-stimulating hormone (FSH) at the highest dose.
- Experiment 2’s results showed that the administration of NMA led to a significant increase in luteinizing hormone (LH) and FSH in intact mares at the highest doses. However, pretreatment concentrations of LH and FSH were higher in long-term ovariectomized mares, and NMA only increased LH but not FSH at the highest dose.
Conclusion from the Research
- The results show that the administration of NMA can stimulate the release of LH and FSH in mares.
- During anestrus, ovarian-intact mares appear to have a more responsive reaction than long-term ovariectomized mares.
- At high doses, NMA could induce a differing release of gonadotropins in long-term ovariectomized mares.
Cite This Article
APA
Fitzgerald BP.
(1996).
Effects of administration of N-methyl-D,L-aspartate (NMA) on gonadotropin secretion in untreated and steroid-treated ovariectomized mares during the breeding season and in intact and ovariectomized mares during anestrus.
Domest Anim Endocrinol, 13(3), 211-218.
https://doi.org/10.1016/0739-7240(96)00016-1 Publication
Researcher Affiliations
- Department of Veterinary Science Maxwell Gluck Equine Research Center, University of Kentucky Lexington, 40546, USA.
MeSH Terms
- Anestrus / blood
- Animals
- Breeding
- Dose-Response Relationship, Drug
- Estradiol / pharmacology
- Female
- Follicle Stimulating Hormone / blood
- Gonadotropins / blood
- Gonadotropins / metabolism
- Horses / blood
- Injections, Intravenous / veterinary
- Luteinizing Hormone / blood
- N-Methylaspartate / administration & dosage
- N-Methylaspartate / pharmacology
- Ovariectomy / veterinary
- Progesterone / pharmacology
- Radioimmunoassay / veterinary
- Random Allocation
- Seasons
- Time Factors
Citations
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