Neuroimmune regulation of colonic secretion in guinea pigs

The role of submucosal neurons in anaphylactic-like responses in colonic epithelium from immunized guinea pigs was examined 6-8 wk after inoculation with 2 x 10(3) infective Trichinella spiralis larvae. Serosal addition of T. spiralis antigen (20 micrograms/ml) to muscle-stripped segments of colon set up in flux chambers evoked a maximum increase in short-circuit current within 5 min in immune, but not nonimmune, guinea pigs. Quercetin, a membrane-stabilizing drug, and pyrilamine, a histamine H1 receptor antagonist, attenuated epithelial responses evoked by T. spiralis antigen. Antigen-induced epithelial responses were reduced by neural blockade with tetrodotoxin and by the muscarinic receptor antagonist atropine but not by blockade of nicotinic receptors with mecamylamine. Antigenic challenge of colonic mucosa from immune guinea pigs enhanced the secretory responses to endogenously released neurotransmitters evoked by electrical field stimulation and substance P. In the presence of antigen, the tetrodotoxin-insensitive component of the carbachol response was enhanced and was reversed by quercetin but not pyrilamine. The results suggest that submucosal cholinergic nerves play a role in mediating the rapid epithelial responses evoked by worm antigen in the colonic mucosa of T. spiralis-immune guinea pigs. Interaction of immunological mediators with neurotransmitters in the submucosal plexus augments the secretory mucosal response triggered by T. spiralis in immunized hosts.