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Type: Artigo de periódico
Title: Increased spontaneous activity and reduced inotropic response to catecholamines in ventricular myocytes from footshock-stressed rats
Author: Penna, LB
Bassani, RA
Abstract: Exposure to stressors has been shown to change atrial responsiveness to catecholamines, but it is not clear yet how it affects the ventricular myocardium, which plays a major role in the catecholamine-stimulated increase in cardiac output. Adult male rats were submitted to restraint (RST) or footshock (FS) sessions for 3 days. Reactivity to agonists of the beta-adrenergic pathway was analyzed in left ventricular myocytes isolated from stressed and control rats (CTR). Whereas no significant changes were detected after RST, enhancement of catecholamine-induced spontaneous activity, accompanied by decrease in inotropic maximal response, was observed in myocytes from FS rats. Changes were reversed by beta(1)-, but not by alpha(1)- or beta(2)-adrenoceptor (AR) blockade. Similar alterations were seen in response to forskolin. However, responsiveness to 3-isobutyl-1-methylxanthine and CaCl(2) was comparable in control and FS groups. A significant negative correlation was observed between the maximally stimulated spontaneous activity rate and contraction amplitude. Results indicate that: (a) enhanced automatism during adrenergic stimulation of myocytes from FS rats is mediated by beta(1)-ARs and seems to involve post-receptor mechanisms, probably decreased cAMP degradation; (b) the exaggerated spontaneous activity, which may contribute to generation of catecholaminergic arrhythmias, might limit the development of the inotropic response.
Subject: beta-Adrenoceptors
footshock stress
inotropic response
restraint stress
ventricular myocardium
Country: Inglaterra
Editor: Taylor & Francis Ltd
Rights: fechado
Date Issue: 2010
Appears in Collections:Unicamp - Artigos e Outros Documentos

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