The effects of agonists and antagonists, specific for the different adrenoceptor subtypes on the automaticity of cultured ventricular cells from postnatal @entity35 , were studied. Chronotropic responses were assessed by recording monophasic action potentials using intracellular microelectrodes. Contraction was assessed by an electro-optical procedure. @entity3044 , @entity3045 , @entity2647 , and @entity7202 increased the spontaneous rate in a dose-dependent manner, but the stimulatory potencies of alpha-adrenoceptor agonists were weaker than those of the beta-alternates. The frequency response to @entity3044 was inhibited by @entity2165 but not by @entity24971 . @entity2165 was also more effective than @entity24971 in antagonizing the rate acceleration by @entity3045 . The chronotropic effects of @entity2647 and @entity7202 were inhibited by @entity3159 . In contrast, neither @entity1338 nor @entity3160 displayed any chronotropic action. These findings suggest that the postjunctional adrenoceptors present in the sarcolemma of the isolated cardiac muscle cells, which mediate automaticity responses to @entity2661 , are of beta 1, beta 2, and alpha 1 types, the physiological contribution of the beta 1-adrenoceptors being predominant. Applicability of these conclusions to the in situ myocardiocytes is discussed with respect to the level of functional differentiation achieved by the @entity35 myocardial cells in culture.

Characterization of postjunctional adrenoceptor subtypes in isolated XXXX myocardial cells in culture.

@entity7202 :: ('MESH:D008729', 'Chemical') :: ['methoxamine'] @entity3160 :: ('MESH:D015016', 'Chemical') :: ['yohimbine'] @entity1338 :: ('MESH:D003000', 'Chemical') :: ['clonidine'] @entity3045 :: ('MESH:D000420', 'Chemical') :: ['salbutamol'] @entity3159 :: ('MESH:D011224', 'Chemical') :: ['prazosin'] @entity3044 :: ('MESH:D007545', 'Chemical') :: ['(-)-isoproterenol', '(-)-Isoproterenol'] @entity24971 :: ('MESH:D002078', 'Chemical') :: ['butoxamine'] @entity2647 :: ('MESH:D010656', 'Chemical') :: ['phenylephrine', '(-)-phenylephrine'] @entity35 :: ('10116', 'Species') :: ['rat'] @entity2661 :: ('MESH:D002395', 'Chemical') :: ['catecholamines'] @entity2165 :: ('MESH:D001262', 'Chemical') :: ['atenolol', 'Atenolol']
@entity35 :: (10116,Species) :: ['rat']
