Difference in the Motile Reactivity of Jejunum, Cecum, and Right Ventral Colon to Xylazine and Medetomidine in Conscious Horses

Abstract

We investigated effects of xylazine and medetomidine on contractive motility in different regions of the intestine in conscious horses, to provide some insight into elucidation of the regional difference in the painrelieving effect of α₂-adrenergic agonists. We used 6 healthy adult male thoroughbread horses. Horses were intravenously given one of two calmatine-anodines, xylazine (1.0 mg/kg) and medetomidine (0.0075 mg/kg). The jejunum, cecum, and right ventral colon were examined for contractive motility. Both xylazine and medetomidine inhibited contractive motility for relatively similar durations, the effect of medetomidine was more potent than that of xylazine. After the horses were treated with both drugs, the contractive motility of the cecum and colon was inhibited for a longer duration and the inhibition was more intense than the corresponding duration and intensity of inhibition of the jejunum. These results suggest that the cecum and colon of the horse is more sensitive than the jejunum to α₂-adrenergic agonists.