Effects of gonadotropin-releasing hormone infused in a pulsatile or continuous fashion on serum gonadotropin concentrations and ovulation in the mare.

The research conducted a comparison between continuous and pulsatile intravenous infusion of Gonadotropin-releasing hormone (GnRH) on ovulation and blood gonadotropin levels in mares. It demonstrated that the pulsatile administration of GnRH led to an earlier and more substantial increase in blood LH (Luteinizing hormone) levels, and expedited ovulation when compared to the continuous infusion method.

Objective of the Research

• The objective of this study was to observe the effects of a continuous versus pulsatile intravenous infusion of gonadotropin-releasing hormone (GnRH) on serum gonadotropin concentrations and ovulation in mares, both those in heat (cycling mares) and those not in heat (anestrous mares).

Methodology

• The anestrous mares in Experiment One were either untreated, received a continuous GnRH infusion at different dosage levels, or received GnRH through pulsatile infusion.
• In the second experiment, the mares in heat were either untreated, given a continuous GnRH infusion, or a pulsatile infusion.

Findings

• After GnRH infusion, circulating levels of LH increased sooner and more significantly in the group receiving the GnRH through pulsatile infusion, while FSH (Follicle Stimulating Hormone) levels remained similar across all groups.
• The development timeline for the primary ovarian follicle did not differ significantly between GnRH treatment groups. However, mares administered with pulsatile GnRH ovulated around 2.8 days earlier than those given a continuous infusion of the same hormone quantity.
• The control group and the mares given the lowest GnRH dose failed to ovulate or show significant follicular development throughout the study period.
• The concentration of LH on the day of ovulation was found to be lower in the continuous infusion group compared to the pulsatile infusion and control groups.

Conclusion

• The research implies that the mode of GnRH administration can influence the timing and extent of LH release. This conclusion is based on the observation that pulsatile infusion of GnRH provokes a more substantial and more prompt LH response, resulting in an earlier occurrence of ovulation when compared to the continuous infusion method.