Endocrine and ovarian responses to combined estradiol benzoate-sulpiride in seasonally anovulatory mares treated with kisspeptin.

Abstract

The objective of this experiment was to determine if incorporation of kisspeptin-10 (Kp10) into treatment with estradiol benzoate (EB) and sulpiride to induce early cyclicity would result in greater endocrine responses and a greater number of mares responding with either follicle(s) >&#xa0;30&#xa0;mm or ovulation within 25 days of treatment. Eighteen anestrous mares were blocked by breed, body condition, and age before random assignment to treatment or control. All mares received 50&#xa0;mg EB before receiving osmotic minipumps containing either saline (n&#xa0;=&#xa0;9) or Kp10 (50&#xa0;&#x3bc;g/hour; n&#xa0;=&#xa0;9) one day later. The next day, all mares received 3&#xa0;g sulpiride. Serial blood sampling occurred after pump placement and continued daily for 25 days. Transrectal ultrasounds were performed regularly to monitor ovarian activity. Data were analyzed by Student's t-test or ANOVA with repeated measures. Seven Kp10-treated mares responded compared to only 4 saline-treated mares. Mean days from sulpiride treatment to ovarian response was less in Kp10-treated mares (13.7&#xa0;&#xb1;&#xa0;1.1 d, P&#xa0;&#x2264;&#xa0;0.01) compared to saline-treated mares (35.9&#xa0;&#xb1;&#xa0;7.8 d). Plasma prolactin increased (P&#xa0;<&#xa0;0.001) in response to sulpiride in all mares; however, prolactin was higher (P&#xa0;<&#xa0;0.05) in Kp10-treated mares. Plasma LH increased in all mares beginning 5 days after sulpiride but was greater (P&#xa0;<&#xa0;0.0001) in Kp10-treated mares. Plasma FSH concentrations did not differ between groups. In conclusion, incorporation of Kp10 potentiated the prolactin and LH responses to EB-sulpiride and resulted in more mares responding with early ovarian activity.