ABSTRACT
This chapter surveys the role of 5-HT in the regulation of intestinal absorption and secretion of fluid and electrolytes, and of the mechanisms of action involved in these processes. It discusses role of 5-HT in the secretory responses to enterotoxins and laxative-induced fluid secretion, opiate withdrawal secretion, and fluid secretion induced by intestinal anaphylaxis. The intestinal secretory effects of hyperserotoninemia were studied further in conscious dogs with chronically cannulated, exteriorized proximal jejunal segments. The basal absorptive state was significantly changed to a secretory state when 5-HT was infused (30 µg/kg/min, i.v.). Also in the small intestine of the rat in vivo, d,l-verapamil inhibited the secretory response to close intraarterial infusion of 5-HT, but not the response to vasoactive intestinal polypeptide, a cAMP-dependent secretagogue. 5-HT reverses net absorption of water and electrolytes into net secretion in the small intestine of man and animals and in the colon of some species.
