AJP - Gastrointestinal and Liver Physiology, Vol 256, Issue 5 862-G867, Copyright © 1989 by American Physiological Society
Mechanics and neuropeptide responses of feline pylorus and gastric muscle in vitro
A. Merlo and S. Cohen
Department of Medicine, Temple University School of Medicine, Philadelphia, Pennsylvania 19140.
Mechanical properties and neuropeptide responses were compared for feline
pyloric and gastric muscle under isometric conditions in vitro. Total
tension in antral circular muscle (0.699 +/- 0.003 kg/cm2) was less than in
corpus circular (1.597 +/- 0.007 kg/cm2) or longitudinal muscle from the
lesser and greater curvatures (1.256 +/- 0.009 and 1.253 +/- 0.007 kg/cm2,
n greater than or equal to 55, P less than 0.05). The components of tension
at optimal length were similar for all gastric muscles (P greater than
0.1). The pylorus maintained less total tension (0.335 +/- 0.003 kg/cm2)
and a greater component of resting tension (75.6%) than gastric muscle (P
less than 0.01). Substance P, cholecystokinin-8 (CCK-8), and neurotensin
varied in potency and efficacy in circular muscle of the antrum, corpus,
and inferior portion of the pyloric ring. Longitudinal muscle and the
superior portion of pylorus responded poorly if at all to neuropeptides.
Substance P- but not CCK-8- or neurotensin-induced contractions of gastric
muscle were reduced by tetrodotoxin (TTX) and atropine (P less than 0.05).
Substance P-induced pyloric contractions were TTX sensitive (P less than
0.05) but were unaffected by atropine. We concluded that 1) length-tension
properties of gastric muscle are similar and distinct from the pylorus and
that 2) neuropeptide efficacy varies regionally within the feline stomach
and within the pylorus.
