Αlpha1B -adrenoceptor-mediated positive inotropic and positive chronotropic actions in the mouse atrium

European Journal of Pharmacology
Shuangyi ZhangTakio Kitazawa

Abstract

Modulation of cardiac contractility by α-adrenoceptor is well known in several mammals. Mice are useful experimental animals, but α-adrenoceptor-mediated responses have been examined only in the ventricles. To determine function of α-adrenoceptors in the atrium, effects of α-adrenoceptor agonists on spontaneous contraction and electrical-field stimulation (EFS)-induced contraction were examined. In addition, expression of α1A, α1B, α1D and β1-adrenoceptor mRNAs were examined. In the right atrium, noradrenaline and phenylephrine caused positive inotropic and positive chronotropic actions. However, methoxamine, clonidine and xylazine caused positive inotropic actions, but contractile frequency was decreased at high concentrations. Phenylephrine-induced positive inotropic and chronotropic actions were partially decreased by propranolol, and both actions remained in the presence of propranolol were inhibited by phentolamine or prazosin. A low concentration of silodosin (<100 nM) did not but a high concentration (1 μM) decreased the phenylephrine-induced chronotropic actions. Negative chronotropic actions of clonidine and xylazine were insensitive to propranolol and phentolamine. The EFS-induced contraction of the left atrium was po...Continue Reading

Citations

Sep 29, 2020·Bulletin of Experimental Biology and Medicine·I I KhabibrakhmanovT L Zefirov
Sep 17, 2019·Cellular Signalling·Anne NiemeyerMarie-Cecile Kienitz
Dec 5, 2020·International Journal of Endocrinology·Abril Carbajal-GarcíaLuis M Montaño

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