Possible mechanism of stimulation of gastrin secretion by exogenous serotonin in rats

Abstract

The effect of 6-hydroxydopamine, propranolol, phentolamine, alpha-methyl-tyrosine and alpha-methyl-tyrosine plus propranolol on serotonin-stimulated gastrin secretion in rats has been examined.Gastrin secretion in response to administration of serotonin alone (10 mg/kg i.p.) was significantly reduced in rats pretreated with 6-hydroxydopamine or with propranolol.These results suggest that the effect of exogenous serotonin on gastrin secretion can be described as sympathomimetic and indirect.The serotonin-stimulated gastrin secretion was significantly enhanced by previous administration of phentolamine.Pretreatment with alpha-methyl-tyrosine also elevated serotonin-stimulated gastrin secretion, indicating that in the presence of diminished concentrations of the catecholamines, the influence of exogenous serotonin on secretion by G cells is increased.This enhancement in the serum gastrin levels was also reduced to a significant extent by simultaneous administration of propranolol, which suggested the activation of G-cell beta-adrenergic receptors after serotonin administration.