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Electrophysiological and mechanical effects of calcitonin gene‐related peptide on guinea‐pig atria
Author(s) -
Ohmura Tsuyoshi,
Nishio Matomo,
Kigoshi Shigeru,
Muramatsu Ikunobu
Publication year - 1990
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1990.tb12046.x
Subject(s) - chronotropic , calcitonin gene related peptide , medicine , electrophysiology , endocrinology , chemistry , tetrodotoxin , guinea pig , calcium , inotrope , depolarization , membrane potential , adenosine , pacemaker potential , calcitonin , neuropeptide , biology , receptor , heart rate , biochemistry , blood pressure
1 The effects of calcitonin gene‐related peptide (CGRP) on mechanical and electrophysiological responses were studied in the guinea‐pig atrial muscle preparations and in single cells. 2 CGRP (>10 −9 m ) enhanced the twitch contraction in a concentration‐dependent manner in electrically driven left atria and increased heart rate in spontaneously beating right atria. The positive inotropic and chronotropic effects of CGRP were not inhibited by propranolol but were attenuated by reduction of the calcium concentration in the bathing medium. 3 In single left atrial cells, CGRP slightly hyperpolarized the resting potential but did not affect the other action potential parameters significantly. 4 Under whole‐cell voltage‐clamp conditions, CGRP increased the calcium inward current. The peptide also increased the steady inward current elicited by hyperpolarization and the late outward current by depolarization. 5 These results suggest that CGRP may produce the positive inotropic and presumably chronotropic effects by increasing calcium inward current. CGRP also increases the potassium permeability. Such effects on ionic currents may not produce any apparent change in the action potential conformation, due to their opposite directional actions and relatively weak potencies.