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...