AJP - Gastrointestinal and Liver Physiology, Vol 255, Issue 6 787-G793, Copyright © 1988 by American Physiological Society
Neuropeptide responses and mechanics of the proximal and distal feline colon in vitro
A. Merlo and S. Cohen
Department of Medicine, Temple University School of Medicine, Philadelphia, Pennsylvania 19140.
Mechanical properties and responses to neuropeptides were compared for
proximal and distal feline colonic muscle. Proximal longitudinal (PL),
proximal circular (PC), distal longitudinal (DL), and distal circular (DC)
muscles were studied in vitro under isometric conditions. Total tension in
DL [1.636 +/- 0.009 (SE) kg/cm2] was greater than in DC (0.699 +/- 0.004
kg/cm2) or PC (0.710 +/- 0.005 kg/cm2, P less than 0.05). Longitudinal
muscle developed proportionately more active tension than circular muscle
at each region (80.9% in DL vs. 54.1% in DC and 77.1% in PL vs. 52.3% in
PC, P less than 0.01). Neuropeptides varied in potency and efficacy.
Cholecystokinin octapeptide (CCK-8) was the most potent and efficacious in
PL and substance P was the most efficacious in PC muscle (P less than
0.05). Substance P was more efficacious whereas CCK-8 and neurotensin were
less efficacious in PC than PL muscle (P less than 0.01). DL muscle did not
respond to CCK-8. DC muscle did not respond to CCK-8 or neurotensin.
Isometric contractions to each neuropeptide were insensitive to
tetrodotoxin. We conclude that 1) mechanical properties of circular and
longitudinal colonic muscle differ and 2) responses to neuropeptides depend
on anatomic region and intrinsic properties.
