Extrinsic nervous control of the ileo-cecal sphincter in the cat

The influence on the ileo-cecal sphincter (ICS) of electrical efferent stimulation of the splanchnic, lumbar colonic and vagal nerves and of intestinal distension was studied in anesthetized cats. A new flow-recording technique was designed. Reponses in the ICS to stimulation were recorded as changes in the transsphincteric flow. The response in the ICS was compared to the responses in the intestine proximal and distal to the sphincter. Sympathomimetic amines and autonomic blocking drugs were used in order to elucidate the autonomic mechanism by which the responses to stimulation were mediated. On the basis of the observations made the following conclusions were drawn: 1. Both the splanchnic and the lumbar colonic nerves exert a contractile influence on the ICS. The effect is mediated via excitatory adrenergic alpha-receptors. 2. The ICS contains inhibitory adrenergic beta-receptors. 3. Activation of the vagal nerves causes a decrease of the transsphincteric flow which is at least partly due to a direct nervous effect on the sphincteric muscle. A cholinergic mechanism is suggested. 4. Intestinal distension elicits contraction of the ICS. This excitatory intestino-ileo-cecal sphincteric reflex is a spinal reflex and mediated via adrenergic fibres within the sympathetic nervous system acting on alpha-receptors.