Adrenergic regulation of ileocecal sphincter function in the cat

Abstract

Abstract The neural control of the ileocecal sphincter (ICS) is poorly understood. The purpose of this study is to evaluate: (a) ICS and blood pressure responses to alpha- and beta-adrenergic agonists and antagonists; and (b) the ICS response to direct stimulation or section of the greater splanchnic nerves. In the anesthetized cat, the ICS is 1.36 ± 0.05 cm (mean ± SEM) in length and maintains a basal pressure of 23.5 ± 1.5 mm Hg. Phenylephrine gave a dose-dependent increase in ICS pressure with a maximal response of 16.0 ± 2.0 mm Hg. Isoproterenol gave a maximum reduction in ICS pressure of 51.2 ± 3.4%. Phentolamine decreased ICS pressure by 61.3 ± 2.8%, but propranolol had no effect. Section of the greater splanchnic nerve had no effect on basal ICS pressure. Electrical stimulation of the cut peripheral end of the nerve produced a maximal increase in sphincter pressure of 16.0 ± 1.5 mm Hg at 10 V, 10 Hz. This response was antagonized by phentolamine, but not by propranolol or atropine. Stimulation of the central end of the splanchnic nerve had no effect on ICS pressure. Adrenergic drugs and splanchnic stimulation did not affect ileal or colonic motility. These studies indicate that: (a) the ICS is a high pressure zone that shows an excitatory response to peripheral splanchnic nerve stimulation and alpha-adrenergic agonists; (b) beta-adrenergic stimulation inhibits ICS pressure, but plays no apparent role in the response to splanchnic stimulation; and (c) the ICS responds differently than the adjacent ileum or colon.