Stimulation of beta-adrenoceptors with isoprenaline inhibits small intestinal activity fronts and induces a postprandial-like motility pattern in humans.

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AIMS: To investigate the effects of beta-adrenoceptor stimulation, using the agonist isoprenaline and the antagonist propranolol, on migrating motor complexes in the upper intestine of 16 healthy human volunteers. METHODS: Fasting motility was monitored using a tube with water perfused side holes connected to a pneumohydraulic system. Continuous eight hour recordings were obtained from each volunteer after a 12 hour fasting period. In all experiments, saline was given as control for the first four hour period and beta-adrenergic agents for the next four hours. In separate control studies, saline was given for the whole eight hour period. RESULTS: Isoprenaline (2.5 micrograms/kg/min) reduced the number of activity fronts (phase III) of migrating motor complexes from 3 (2-4) in controls to 1 (0-2) during isoprenaline infusion (p < 0.01). Also, phase II-like activity replaced the regular motility pattern (p < 0.01). By contrast, propranolol (25 micrograms/kg/min) did not induce any significant changes in phase III compared with controls. Saline alone had no effect on motor activity. CONCLUSIONS: Isoprenaline inhibited activity fronts in the human proximal small intestine and induced a postprandial-like motility pattern, whereas propranolol did not affect motor patterns. Stimulation of beta-adrenoceptors is of importance in the control of motor activity of the human small intestine, especially under stressful conditions with high adrenergic activity.

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