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Provedor de dados:  BJMBR
País:  Brazil
Título:  The left ventricular contractility of the rat heart is modulated by changes in flow and a1-adrenoceptor stimulation
Autores:  Vassallo,P.F.
Data:  1998-10-01
Ano:  1998
Palavras-chave:  Myocardial performance
Coronary perfusion pressure
Coronary flow
Resumo:  Myocardial contractility depends on several mechanisms such as coronary perfusion pressure (CPP) and flow as well as on <FONT FACE="Symbol">a</font>1-adrenoceptor stimulation. Both effects occur during the sympathetic stimulation mediated by norepinephrine. Norepinephrine increases force development in the heart and produces vasoconstriction increasing arterial pressure and, in turn, CPP. The contribution of each of these factors to the increase in myocardial performance needs to be clarified. Thus, in the present study we used two protocols: in the first we measured mean arterial pressure, left ventricular pressure and rate of rise of left ventricular pressure development in anesthetized rats (N = 10) submitted to phenylephrine (PE) stimulation before and after propranolol plus atropine treatment. These observations showed that in vivo <FONT FACE="Symbol">a</font>1-adrenergic stimulation increases left ventricular-developed pressure (P&lt;0.05) together with arterial blood pressure (P&lt;0.05). In the second protocol, we measured left ventricular isovolumic systolic pressure (ISP) and CPP in Langendorff constant flow-perfused hearts. The hearts (N = 7) were perfused with increasing flow rates under control conditions and PE or PE + nitroprusside (NP). Both CPP and ISP increased (P&lt;0.01) as a function of flow. CPP changes were not affected by drug treatment but ISP increased (P&lt;0.01). The largest ISP increase was obtained with PE + NP treatment (P&lt;0.01). The results suggest that both mechanisms, i.e., direct stimulation of myocardial <FONT FACE="Symbol">a</font>1-adrenoceptors and increased flow, increased cardiac performance acting simultaneously and synergistically.
Tipo:  Info:eu-repo/semantics/article
Idioma:  Inglês
Editor:  Associação Brasileira de Divulgação Científica
Relação:  10.1590/S0100-879X1998001000019
Formato:  text/html
Fonte:  Brazilian Journal of Medical and Biological Research v.31 n.10 1998
Direitos:  info:eu-repo/semantics/openAccess

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