Efferent pathways in the reflex control of gastric emptying in rats

Previous studies have established that acid, hypertonic, or protein-rich liquid test meals delay gastric emptying by reflex pathways involving the extrinsic innervation of the gut. To characterize the efferent pathways involved in these reflexes, we have studied the emptying of liquid test meals in control rats and in rats after celiac ganglionectomy, pyloroplasty, and treatment with guanethidine or 6-hydroxydopamine, and in rats with circulating vasoactive intestinal polypeptide (VIP) antibodies. The results suggest that the action of hypertonic solutions on gastric emptying requires an intact celiac ganglion, that acid requires an intact pylorus, and that the action of protein-rich meals is suppressed by VIP antibodies. Sympathetic adrenergic neurons do not apparently mediate the gastric emptying of any of these solutions. The results suggest that there are at least three different reflexes by which the different components of a mixed meal might control gastric emptying. The results are also consistent with the idea that vagovagal reflexes mediate the action of protein-rich solutions on gastric emptying in rats.