Interactions of xylazine and acepromazine with oxytocin and the effects of these interactions on intrauterine pressure in normal mares and mares with delayed uterine clearance.

This research paper investigates the impacts of the sedative drugs xylazine and acepromazine on intrauterine pressure in mares, with a focus on effects when mated with oxytocin. The study reveals that xylazine, an alpha2 agonist, resulted in prolonged increased intrauterine pressure, while acepromazine, an alpha1 antagonist, decreased the number of contractions in mares with delayed uterine clearance.

Research Approach

• The research was conducted on four normal mares and four mares with delayed uterine clearance.
• An 8-F catheter with three distinct pressure sensors was used to measure intrauterine pressure for 100 minutes during the oestrus of each mare.
• The mares were initially given either xylazine, acepromazine or saline intravenously (i.v.) after 10 minutes of baseline recording. Oxytocin was then given i.v. after another 30 minutes and pressure was recorded for an additional 60 minutes.
• The team focused on the changes in pressure, including the number of uterine contractions, the onset and duration of the first contraction, and the time when intrauterine pressure changed from the baseline value.
• Statistical analysis was carried out using the mixed procedure of Statistical Analysis System, with Analysis of Variance (ANOVA) used to detect effects and interactions of the treatment.

Findings

• Xylazine was found to cause tetanic (sustained muscle) contractions in all mares.
• When xylazine was administered to mares with delayed uterine clearance in advance of oxytocin, there was a noticeable increase in intrauterine pressure duration compared to that in normal mares.
• Acepromazine administration had no effect on oxytocin-induced contraction patterns in normal mares. In mares with delayed uterine clearance, however, there was a decrease in the number of contractions.
• Mares with delayed uterine clearance showed an enhanced response to alpha-agonists and -antagonists when given before oxytocin. The researchers suggest that this could be attributed to denervation supersensitivity, a heightened response to neurotransmitters following nerve damage.

Implications

• The results show that xylazine is preferable to acepromazine for sedation of mares after mating as it increases the duration of uterine contraction.
• The study provides insightful data for managing reproductive issues in mares. The effects of these drugs on contractions and intrauterine pressure can aid in making informed decisions about their usage for reproductive treatments.