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In the present study, selective β1-adrenergic receptor antagonist CGP20712A and selective β2-adrenergic receptor antagonist ICI 118551 were administered to isolated cardiomyocytes from young (4-6 months), aged (18-20 months), and clonidine-pretreated aged (18-20 months) Sprague-Dawley rats. Cardiomyocyte contraction amplitude was measured to assess cardiomyocyte response to the β-adrenergic receptor agonist, isoprenaline. CGP20712A reduced cardiomyocyte contraction amplitude in young and aged groups and significantly reduced contraction amplitude in cells from young rats. ICI 118551 had no effect on cardiomyocyte contraction amplitude in young rats, but significantly decreased contraction amplitude in the aged groups, in particular in the clonidine-pretreated aged rats. Results demonstrated that reduced central sympathetic tone improved cardiomyocyte contraction in aged rats by improving the response of β2-adrenergic receptor to isoprenaline.