Effect of administration of an alpha 2-adrenergic agonist, xylazine, on pulsatile gonadotrophin secretion in anoestrous horse mares.

The research article reports on a study conducted to investigate the effects of a specific drug, xylazine, on the secretion of gonadotrophins in horse mares during non-breeding periods. The study suggests that administration of xylazine increases the frequency of gonadotrophin release.

Experiment Overview

• The research is divided into two parts. In the first preliminary experiment, the influence of xylazine, an alpha 2-adrenergic receptor agonist, on horse mares was observed. This involved sedating four horse mares using repeated injections of xylazine.
• In the second experiment, the impact of xylazine-induced sedation on the release of gonadotrophins during varying periods was studied. This experiment was conducted on four mares sampled on different occasions before and after an increase in daylight.

Key Findings

• In the initial experiment, research showed that on the day of xylazine treatment, one to two Luteinizing Hormone (LH) pulses were observed in the treated mares, while only one out of eight untreated mares exhibited a LH pulse in the same twelve-hour period.
• In the second experiment, xylazine treatment showed increased Follicle-Stimulating Hormone (FSH) and LH pulse frequency. The greater effect of the treatment was evident after an increase in day length – all four mares exhibited increased frequency of FSH pulse with the drug treatment.
• It was also seen that after 27 days of increased daylight, the indigenous FSH pulse frequency was higher than before, and this did not further increase with the introduction of xylazine.

Interpretation and Conclusion

• The findings suggest that the non-breeding (anestrous) phase in horse mares, which is typically associated with reduced gonadotrophin secretion, may be influenced by neural mechanisms and can be manipulated using certain drugs such as xylazine.
• Therefore, xylazine could potentially be used to influence breeding cycles or fertility treatments in horse mares due to its impact on increasing gonadotrophin pulse frequency.