ADRENERGIC, CHOLINERGIC AND VIP-ERGIC INFLUENCE ON GASTRIC PHASIC MOTILITY IN THE RAT

We investigated the effects of adrenergic, cholinergic and vasoactive intestinal polypeptide (VIP)-ergic agonists and antagonists on the amp litude of gastric phasic contractions in the anaesthetized rat using a volumetric model. The amplitude of the phasic contractions was reduce d significantly by atropine, hexamethonium or bilateral cervical vagot omy indicating that cholinergic neural activity involving both muscari nic and nicotinic receptors and intact vagal nerve function are integr al parts of the control of basal gastric phasic motility. In contrast, neither selective alpha(1)-,alpha(2)- or non-selective beta-blockers had any significant influence on the amplitude of the gastric contract ions suggesting that adrenergic neurones are not tonically active in t he maintenance of basal phasic motility in the stomach. The amplitude of the gastric phasic contractions was, however, significantly reduced by the alpha(1)-agonist L-phenylephrine, the alpha(2)-agonist clonidi ne and a close intraarterial injection of VIP (3 mu g kg(-1)) but not be the selective beta(1)-agonist, prenalterol, or the beta(2)-agonist, salbutamol. These data suggest the presence of superimposed inhibitor y control of phasic activity by VIP-ergic stimulation and by adrenergi c neurones via alpha-receptor stimulation.