Endocrine And Ovarian Responses To Combined Estradiol Benzoate-Sulpiride In Anestrous Mares Treated With Kisspeptin.

Abstract The objective of this study was to determine if incorporation of kisspeptin 10 (Kp10) into an estradiol benzoate (EB)-sulpiride treatment would result in greater endocrine responses, and a greater number of mares ovulating within 28 days of treatment compared to EB-sulpiride alone. Eighteen anestrous mares were blocked by horse type (light horse and pony crosses), body condition, and age, then randomly assigned to treatment or control. On day 0, all mares received 50 mg EB. On day 1, mini osmotic pumps containing saline (n = 9) or Kp10 (50 mg/hour; n = 9) were inserted subcutaneously in the neck and remained for 7 days. Serial blood sampling occurred for 24 hours after pump placement. On day 2, all mares received 3 g sulpiride. Serial blood sampling continued for 36 hours and daily for 28 days. Transrectal ultrasounds were performed regularly for detection of ovulation. Plasma was assayed for prolactin, luteinizing hormone (LH) and progesterone. Data were analyzed by ANOVA with repeated measures. Plasma prolactin increased (P < .001) in response to sulpiride in all mares and remained stimulated for 7 days. Prolactin responses tended to be greater (P = .09) in Kp10- treated mares compared to controls. No differences were detected in plasma LH during the first 24 hours after pump placement; however, LH increased in all mares beginning 5 days after sulpiride and were greater (P < .05) in Kp10-mares from day 7 to day 21. Eleven of 18 (61%) mares ovulated within 18 days of sulpiride treatment; however, no differences in ovulation dates were detected between Kp10 treated- and control- mares. No differences were detected in plasma progesterone during the first 5 days post ovulation. In conclusion, incorporation of Kp10 potentiated the prolactin and LH responses to EB-sulpiride, but did not further advance first ovulation in treated-mares.