Innervation of the muscularis mucosa in the canine stomach and colon.

A preliminary report is presented of studies into the innervation of the canine muscularis mucosa. In vitro experiments have investigated the mechanical response to electrical stimulation and the release of gut peptides known to modulate gastrointestinal function. Exogenous substance P increased tone and amplitude of phasic contractions while neurotensin and vasoactive intestinal polypeptide (VIP) relaxed the muscularis mucosa. Immunoreactive VIP was released into the superfusate during transmural electrical stimulation of the antrum while VIP and substance P were present in superfusate from the colon. The significance of these findings has been discusses briefly.