Epithelial and mucosal preparations from canine colon: responses to substance P.

The hypothesis that substance P (SP) elicits both direct and indirect responses on the canine proximal colon was tested using two different in vitro preparations. The mucosa contained the muscularis mucosa and the attendant submucosal plexuses whereas the epithelium, being devoid of both, was functionally "nerve-free." Dose-dependent stimulation was noted on both preparations, increases in peak current (microamperes per squared centimeter) as …