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 amplitude of gastric phasic contractions in the anaesthetized rat using a volumetric model. The amplitude of the phasic contractions was reduced significantly by atropine, hexamethonium or bilateral cervical vagotomy indicating that cholinergic neural activity involving both muscarinic and nicotinic receptors and intact vagal nerve function are integral 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 contractions suggesting that adrenergic neurones are not tonically active in the 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 clonidine 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 inhibitory control of phasic activity by VIP-ergic stimulation and by adrenergic neurones via alpha-receptor stimulation.