AJP - Heart and Circulatory Physiology, Vol 257, Issue 4 1082-H1087, Copyright © 1989 by American Physiological Society
Contractile effects of cardiac neuropeptides in isolated canine atrial and ventricular muscles
D. F. Rigel, I. L. Grupp, A. Balasubramaniam and G. Grupp
Department of Pharmacology, University of Cincinnati College of Medicine, Ohio 45267-0575.
Contractile effects of the cardiac neuropeptides vasoactive intestinal
polypeptide (VIP), peptide histidine isoleucine (PHI), neuropeptide Y
(NPY), calcitonin gene-related peptide (CGRP), and neurotensin (NT) were
compared with those of l-isoproterenol (ISO) in isolated canine atrial and
ventricular trabeculae muscles stimulated to contract at 1 Hz. In
ventricular muscles, ISO, VIP, and PHI augmented developed isometric force
by approximately 100%. VIP and PHI were three times and 1/10, respectively,
as potent as ISO. VIP also exhibited positive inotropic effects in atrial
trabeculae. The contractile responses to VIP were unchanged after
beta-adrenergic blockade with nadolol at a concentration (10 microM) that
shifted the ISO dose-response curve two to three orders of magnitude to the
right. In atrial and ventricular trabeculae, NPY (1 microM) attenuated
contractile force by 36 +/- 8 and 30 +/- 4%, respectively. Each peptide
also caused comparable increases or decreases in the rate of development of
force and the rate of relaxation. CGRP and NT caused no significant changes
in developed force in either atrial or ventricular muscles in
concentrations up to 1 microM. Our results indicate a potential positive
inotropic action of endogenous VIP and PHI and a cardiodepressant effect of
endogenous NPY in the canine heart.
