Cardiac activity of calcitonin gene-related peptide in amphibian species (Rana tigrina, Triturus sp).
1. Calcitonin gene-related peptide (CGRP) produced dose-related positive chronotropic and inotropic responses in isolated atria of a newt, Triturus sp. and a frog, Rana tigrina. It was apparent that CGRP was stimulatory on the heart of the amphibian species. 2. In the frog, these dose-related responses were attenuated in the presence of a CGRP antagonist (hCGRP 3 x 10(-8) M). This was indicative of the presence of cardiac CGRP receptors. 3. In the presence of beta-adrenergic (propranolol 10(-6) M) and calcium channel (verapamil 10(-8) M, but not nifedipine 10(-8) M) blocker, the basal AR in the frog were decreased. AR induced by CGRP were increased however. 4. The maximal AR and AT responses of the isolated atria to CGRP were not affected by the presence of propranolol. 5. In the presence of calcium channel blockers (verapamil and nifedipine), the maximal AT response was attenuated. These changes suggest the cardiac effects of CGRP are related to calcium mobilization.
Department of Biology, Chinese University of Hong Kong.
K W
KW
Chiu
Y C
YC
Lee
Y M
YM
Yau
P K
PK
Pang
D000818:Animals; D016275:Atrial Function / Q000187:drug effects; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology* / Q000502:physiology; D002316:Cardiotonic Agents / Q000494:pharmacology*; D006325:Heart Atria / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D011433:Propranolol / Q000494:pharmacology; D011898:Ranidae / Q000502:physiology*; D014319:Triturus / Q000502:physiology*; D014700:Verapamil / Q000494:pharmacology
D002316:Cardiotonic Agents; D011433:Propranolol; D014700:Verapamil; D015740:Calcitonin Gene-Related Peptide