[Contractile activity of duodenum, jejunum, and ileum at psychogenic stress in rabbits before and after muscarinic or nicotinic cholinoceptor blockade]

Abstract

In chronic experiments on rabbits, myoelectric activity (contractile activity index) in distal part of the duodenum, proximal and distal parts of the jejunum and proximal part of the ileum was studied under psychogenic stress caused by rigid fastening rabbit to a table in supine position. In duodenum, the stressor impact rendered stimulating, and in an ileum--inhibitory influence on their motility. In a jejunum the inhibition with the subsequent stimulation was observed, the latter being more expressed in a proximal part of the intestine. The proximo-distal gradient of exitatory and inhibitory influences of the psychogenic stress on contractile activity of the small bowel was revealed: in distal direction, inhibitory influences strengthen and stimulatory ones weaken. The muscarinic receptor blockade abolished increase of the duodenal and jejunal contractile activity obsereved in the control. The nicotinic cholinoceptor blockade abolished increase of the duodenal contractile activity in the 1-st phase of the stressor response and did not exclude an increase of the duodenal contractile activity in the 2-nd phase of the response. Muscarinic or nicotinic blockade did not influence the manifestation of the inhibitory reaction of proximal part of the ileum. In the period after release of the animal, the duodenal and jejunal contractile activity exeeded its initial level. This exeeding did not preserve after muscarinic cholinoceptor blockade but did preserve after nicotinic one in duodenum and proximal jejunum. The received data allow to conclude, that produced by the stress increase of the contractile activity of the distal part of duodenum, proximal and distal parts of jejunum produced by the stress, as well as exceeding the initial contractile activity level in the period after release of an animal, are mediated by cholinergic effector neurones of the enteric nervous system.