Participation of cholinergic mechanisms in the realization of the effect of bombesin on the migrating myoelectrical complex.

The experiments were carried out on dogs with chronically implanted bipolar ball-shaped silver electrodes in the antral part of the stomach and duodenum. The effect of bombesin (injected intravenously in a dose of 200 ng/kg) on the migrating myoelectrical complex (MMC) was examined after pretreatment with hexamethonium (10 mg/kg) or atropin (100 micrograms/kg), or alpha-antagonists (phentolamine, 2 mg/kg) and beta-antagonists (propranolol, 2 mg/kg) of the adrenergic receptors. Introduced during the second MMC phase, bombesin caused inhibition of the spike activity, accompanied by an increase of the slow potential frequency. Prolonged intensified spike activity occurred 5-10 min later. Early brief appearance of spike potentials was observed after bombesin in the presence of hexamethonium, which was not manifested on the background of atropin. After hexamethonium or atropin, however, the phase of the late activation of the spike activity did not occur and there was no change in the effect of bombesin on the frequency of the slow potential. The alpha- and beta-antagonists of the adrenergic receptors do not change the effect of bombesin on the electrical activity of the stomach and the intestines.