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Dopaminergic regulation of gonadotrophin secretion in seasonally anoestrous mares.
Abstract: We have previously demonstrated that daily administration of the dopamine D2 antagonist, sulpiride, during seasonal anoestrus, effectively advances the mean time of onset of the breeding season in mares. The purpose of this study was to examine the effect of sulpiride administration on pulsatile FSH and LH secretion in seasonally anoestrous mares, follicular development, time of first ovulation and the fertility at the first ovulation. Fourteen anoestrous mares were selected based on progesterone concentrations < 1 ng ml-1 for 3 weeks and largest follicle diameter < 20 mm. Starting 30 January, eight seasonally anoestrous mares were treated daily with sulpiride until the first ovulation of the year, and six untreated control mares were maintained under the same environmental conditions. Ovarian activity was monitored and plasma samples were collected every other day. On days 1, 11 and 21 of treatment, plasma samples were collected every 15 min for 11 h in six treated and six control mares. Mares were bred during the first oestrus. Mean time of first ovulation was significantly advanced in sulpiride-treated mares compared with control mares. Pregnancy rate 18 days after ovulation was similar between groups. Mean FSH pulse frequency on the first day of treatment and mean plasma FSH concentrations on day 11 of treatment were significantly higher in sulpiride-treated mares compared with control mares. No significant difference was observed between groups for parameters of LH pulsatile secretion. The results of this study suggest that dopamine inhibits FSH pulsatile secretion in seasonally anoestrous mares.
Publication Date: 1996-09-01 PubMed ID: 8958828DOI: 10.1530/jrf.0.1080055Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
Summary
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The research investigates how the administration of a dopamine D2 antagonist, sulpiride, impacts the start of the breeding season, hormone secretion, and fertility in mares that are seasonally anoestrous. The results reveal that sulpiride could effectively advance the breeding season and increase FSH hormone secretion, with no noted effects on LH secretion or changes in fertility.
Study Purpose and Methodology
- The main objective of this research was to analyse the impact of administering the dopamine D2 antagonist, sulpiride, on follicle-stimulating hormone (FSH) and luteinizing hormone (LH) secretion in seasonally anoestrous mares. Other factors studied were follicular development, time of first ovulation, and fertility following first ovulation. These mares go through a period of reduced sexual receptivity and fertility – seasonal anoestrus.
- 14 anoestrous mares were chosen, judged by low progesterone levels and small follicle diameters. Starting from 30 January, eight of these mares were given sulpiride regularly until their first ovulation of the year. The remaining six mares served as untreated controls. All mares experienced the same environmental conditions.
- Researchers monitored ovarian activity and collected plasma samples every second day. Additionally, plasma samples were taken every 15 minutes for 11 hours on certain days of treatment. The mares were bred during their first oestrus.
Key Findings
- Sulpiride treatment significantly moved the first ovulation time earlier in treated mares compared to the control group.
- There was no significant difference in pregnancy rates between the sulpiride-treated and control mares 18 days after ovulation.
- On the first treatment day, the average frequency of FSH pulses and mean plasma FSH levels on day 11 were significantly higher in sulpiride-treated mares compared to their untreated counterparts.
- There was no discernable difference between the two groups in the parameters of LH pulsatile secretion.
Conclusion
- The study’s results highlight that dopamine may suppress FSH pulsatile secretion in mares during periods of seasonal anoestrus.
- The administration of sulpiride could effectively advance the breeding period and increase FSH hormone secretion in mares during their seasonally anoestrous phase. However, there were no noted effects on LH secretion or changes to fertility rates.
Cite This Article
APA
Besognet B, Hansen BS, Daels PF.
(1996).
Dopaminergic regulation of gonadotrophin secretion in seasonally anoestrous mares.
J Reprod Fertil, 108(1), 55-61.
https://doi.org/10.1530/jrf.0.1080055 Publication
Researcher Affiliations
- Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
MeSH Terms
- Anestrus / physiology
- Animals
- Female
- Fertility / drug effects
- Follicle Stimulating Hormone / blood
- Follicle Stimulating Hormone / metabolism
- Gonadotropins, Pituitary / blood
- Gonadotropins, Pituitary / metabolism
- Horses / physiology
- Luteinizing Hormone / blood
- Luteinizing Hormone / metabolism
- Ovarian Follicle / physiology
- Ovulation / drug effects
- Receptors, Dopamine D2 / drug effects
- Secretory Rate / drug effects
- Sulpiride / pharmacology
- Time Factors
Citations
This article has been cited 2 times.- Kim S, Jung H, Murphy BA, Yoon M. Efficiency of Equilume light mask on the resumption of early estrous cyclicity and ovulation in Thoroughbred mares. J Anim Sci Technol 2022 Jan;64(1):1-9.
- Satué K, Fazio E, Rubio MD, Cravana C, Medica P. Intrafollicular and Systemic Dopamine, Noradrenaline and Adrenaline Concentrations in Cycling Mares. Animals (Basel) 2020 Oct 16;10(10).
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