For each of polypeptides secreted by the enteric nervous system in the alimentary tract A–E, select the most appropriate effect on the gut from the list below

A. Option 2 Relaxation of sphincters. Vasoactive intestinal polypeptide (VIP) also causes vasodilatation by relaxing vascular smooth muscle.

B. Option 5 Inhibition of gastric emptying. Besides its main action of stimulating the gall bladder to contract, cholecystokinin (CCK) decreases the rate of emptying of the stomach.

C. Option 4 Inhibition of gut motility. Somatostatin, the growth hormone-inhibiting hormone, originally isolated in the hypothalamus, is secreted by D cells in the intestinal mucosa. It inhibits the release of several gut hormones including motilin and so inhibits gut motility.

D. Option 3 Increase in small intestinal motility. Substance P, a polypeptide found in intestinal mucosal endocrine cells, acts locally to increase gut motility.

E. Option 1 Release of gastrin. Gastrin-releasing polypeptide (GRP) is released by the postganglionic vagal fibres that innervate the G cells in the lateral walls of the glands in the pyloric antrum. Activity in these nerves causes release of the gastrin granules in the G cells.