Sympathetic nervous control of cat ileocecal sphincter.

A perfusion method was designed in order to investigate that effects of stimulation of the splanchnic and lumbar colonic nerves on the ileocecal sphincter (ICS) of the cat. Splanchnic and lumbar colonic nerve stimulation at physiological frequencies, i.e., below 10-12 impulses/s, elicited a contraction of the sphincter concomitant with an inhibition of the motility of the adjacent parts of the small and large intestines. It is concluded that the splanchinc and lumbar colonic nerves contract the ICS by a direct effect on the sphincter and not via a contraction of the intestine surrounding the sphincter. Guanethidine and phenoxybenzamine but not propranolol blocked the contraction of the ICS. It is suggested that the splanchnic and lumbar colonic nerves control the sphincter via an alpha-adrenergic mechanism. Inhibitory fibers within the splanchnic or lumbar colonic nerves to the ICS were not found. The excitatory in the ICS elicited by adrenaline, nor-adrenaline, or phyenylephrine infusion was completely blocked by phenoxybenzamine. Propranolol did not block the effect on ICS of these drugs. On the contrary, an augmented response could be shown, indicating unmasking of an excitatory alpha-receptor response by blockade of inhibitory beta-receptors. Further support for these inhibitory beta-receptors was provided by the finding that isoprenaline had a relaxing effect on the sphincteric muscle, an effect that was blocked by propranolol. In order to block the inhibitory effect on the small and large intestine elicited by splanchnic and lumbar colonic nerve stimulation, both phenoxybenzamine and propranolol had to be administered.