Participation of the adrenergic receptors in the regulation of large bowel motor activity in sheep.

In sheep with long-standing fistulae of the caecum, proximal loop of the colon and rumen the motor activity of these parts of the intestine was studied using the balloon method. Slow isoprenaline infusion caused first inhibition of caecal contractions, followed by gradually decreasing intensity of contractions of the colon and rumen. This inhibitory effect of isoprenaline was eliminated by propranolol. Intravenous infusion of phenylephrine failed to inhibit the colonic motor activity. A small dose of atropine, similarly as isoprenaline, caused an irregular inhibition of the contractions of the caecum, colon and rumen. In sheep, in contrast to other animal species, the effects inhibiting large intestine motility are mediated only by the beta-adrenergic receptors. The inhibitory effect of the beta-adrenergic receptors was strongest in the caecum.