Changes in α1‐adrenoceptor coupling to Ca2+ channels during development in rat heart

Abstract
It has been reported in the literature that α1,-adrenoceptor activation in adult rat heart does not cause an increase in Ca2+ current but involves a decrease in I t. This may explain in part the positive inotropic effect of α1-adrenoceptor activation. In this study, the effect of phenylephrine, an α-adrenergic agonist, on L-type Ca2+ channel current was compared in young and neonatal rat myocytes. In the presence of propranolol, phenylephrine increased the Ca+ current (reversed by prazosin) in neonatal but not in young rat myocytes suggesting that the coupling of the α1-adrenoceptor to Ca2+ channels may switch during development.