[Mechanisms of inhibition of the contractile activity in the ileo-caecal zone in rabbits under psychogenic stress].

In experiments on unanaesthetized rabbits, myoelectric activity (contractile activity index) of distal ileum, caecum, and proximal colon in two sites was studied under stress induced by fastening a rabbit to the table in supine position. The stress caused sharp decrease (up to complete disappearance) of the contractile activity in all studied compartments of the ileocaecal intestine with partial or complete restoration after release of the animal. Nonselective blockade of pre- and postsynaptic alpha-adrenoceptor with dihydroergotoxin abolished the initial component of the specified inhibitory response. The latter was caused by "adrenergic inhibition" as a result of action of catecholamines circulating in blood on inhibitory smooth muscle alpha-adrenoceptor. Against the background of muscarinic cholinoceptor blockade, the stressor inhibition of ileocaecal contractile activity observed in control experiments was completely preserved. The periods of supression of ileoceacal contractile activity under stress resistant to blockade of alpha-, beta-adrenoceptor and muscarinic cholinoceptor, are caused by the mechanism of "nonadrenergic noncholinergic inhibition", which is realized at the expence of activation of the enteric inhibitory neurones.