Administration of sulpiride to anovulatory mares in winter: effects on prolactin and gonadotropin concentrations, ovarian activity, ovulation and hair shedding.
Sixteen seasonally anovulatory mares were randomly allotted to two groups and injected daily with either sulpiride (1 mg/kg body weight) or vehicle from 14 January to 14 February. Sulpiride administration increased daily plasma prolactin concentrations (P < 0.05), although the prolactin response during the 6 h following sulpiride injections decreased markedly from the 1st to the 6th day of treatment (treatment by day, P < 0.0001). Plasma concentrations of LH and FSH were not affected by treatment (P > 0.1). Injection of GnRH and TRH on 15 February showed that the response of plasma prolactin to secretagogue was increased in sulpiride-treated mares (P < 0.005), while there was no effect (P > 0.1) of sulpiride treatment on the response of LH or FSH. Both treatment groups had similar changes in numbers of follicles 10-19 and > or = 20 mm during the experiment (P > 0.1). Similarly, the mean change in maximal follicular size was not affected by treatment (P > 0.9). No mare ovulated during the study, and plasma progesterone concentrations were similar in both groups (P > 0.1), always at levels < 1 ng/ml. Hairshedding increased with time in all mares (P < 0.001) and was increased by sulpiride injections (P = 0.09). It was concluded that sulpiride administration to seasonally anovulatory mares under the conditions of our experiment increased daily plasma prolactin levels but did not stimulate gonadotropin secretion or ovarian activity.
Donadeu
F X
FX
Department of Animal Science, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge 70803, USA.
Thompson
D L
DL
D000818:Animals; D000858:Anovulation; D018492:Dopamine Antagonists / Q000008:administration & dosage*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage; D006062:Gonadotropins / Q000097:blood; D006197:Hair / Q000187:drug effects / Q000502:physiology; D006736:Horses / Q000502:physiology*; D007700:Kinetics; D007986:Luteinizing Hormone / Q000097:blood; D006080:Ovarian Follicle / Q000033:anatomy & histology; D010053:Ovary / Q000000981:diagnostic imaging / Q000187:drug effects / Q000502:physiology; D010060:Ovulation / Q000187:drug effects*; D010919:Placebos; D011374:Progesterone / Q000097:blood; D011388:Prolactin / Q000097:blood*; D012621:Seasons; D013469:Sulpiride / Q000008:administration & dosage*; D013973:Thyrotropin-Releasing Hormone / Q000008:administration & dosage; D014463:Ultrasonography
D018492:Dopamine Antagonists; D006062:Gonadotropins; D010919:Placebos; D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D013973:Thyrotropin-Releasing Hormone; D013469:Sulpiride; D011388:Prolactin; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone