Induction of reproductive function in anestrous mares using a dopamine antagonist

We investigated the role of dopamine in the regulation of seasonal reproductive activity in mares. Nine seasonal anestrous mares, maintained under a natural photoperiod, were treated daily with a dopamine D2 antagonist, [−]-sulpiride (200 mg/mare, im), beginning February 5 (day of year = 36) until t...

Full description

Saved in:
Bibliographic Details
Published in:Theriogenology 1997-01, Vol.47 (2), p.467-480
Main Authors: Besognet, B., Hansen, B.S., Daels, P.F.
Format: Article
Language:English
Subjects:
CICLO ESTRAL
CYCLE OESTRAL
DOPAMINA
DOPAMINE
ESTROGENOS
FSH
HFS
HORMONAS
HORMONE
horse
JUMENT
OESTROGENE
OVAIRE
OVARIOS
PERIODICIDAD
PERIODICITE
PLASMA SANGUIN
PLASMA SANGUINEO
PROLACTINA
PROLACTINE
seasonality
SECRECION
SECRETION
YEGUA
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:We investigated the role of dopamine in the regulation of seasonal reproductive activity in mares. Nine seasonal anestrous mares, maintained under a natural photoperiod, were treated daily with a dopamine D2 antagonist, [−]-sulpiride (200 mg/mare, im), beginning February 5 (day of year = 36) until the first ovulation of the year or for a maximum of 58. Nine untreated anestrous mares were maintained under the same conditions. The ovaries were examined by ultrasonography twice a week, and blood was collected three times a week for progesterone, LH, FSH and prolactin determinations. Mean day of first ovulation was significantly advanced for [−]-sulpiride-treated mares than control mares (mean day of year ± SEM = 77.3 ± 7.9 and 110.0 ± 6.8, respectively; P < 0.01). Eight mares ovulated during [−]-sulpiride treatment while one mare failed to ovulate. Ovulation occurred 91 d after the start of treatment or on Day 127. All mares continued to have normal estrous cycles after the first ovulation. First cycle length and luteal progesterone concentrations did not differ between [−]-sulpiride-treated and control mares. Plasma prolactin concentrations were significantly increased at 2 and 9 h after [−]-sulpiride administration (P < 0.05), and had returned to basal levels by 24 h. At the time of the LH surge associated with the first ovulation, mean LH and FSH secretion was significantly higher in [−]-sulpiride-treated mares than in control mares (P < 0.05). These results suggest that dopamine plays a role in the control of reproductive seasonality in mares and exerts a tonic inhibition on reproductive activity during the anovulatory season.
ISSN:0093-691X
1879-3231
DOI:10.1016/S0093-691X(97)00005-8