Substance P enteric neurons mediate non-colinergic transmission to the circular muscle of the guinea-pig intestine

Abstract

The sites of action and possible roles of substance P in contracting the circular muscle of the guinea-pig ileum were studied using two analogues of substance P that act as antagonists of some of its actions. These are d-Arg1, d-Pro2, d-Trp7,9, Leu11-substance P and d-Pro2, d-Trp7,9-substance P, referred to by the single letter amino acid codes for the substituting amino acids as (RPWWL)-SP and (PWW)-SP, respectively. Records of circular muscle activity were taken from strips of intestine free of mucosa and submucosa and from rings with all layers of intestine intact. Substance P was equally effective in contracting the circular muscle strips as it was in contracting the longitudinal muscle...