Evaluation of Cardiac Responses to Adrenaline and Propranolol in Experimental Models

Abstract

The present study was undertaken to evaluate the cardiac effects of adrenaline, a β-adrenergic agonist, and propranolol, a non-selective β-adrenergic antagonist, using an isolated heart preparation. The primary objective was to investigate changes in heart rate and contractile force and to determine the nature of interaction between these drugs. Adrenaline was administered in graded concentrations, producing a dose-dependent increase in heart rate and contraction amplitude, indicating positive chronotropic and inotropic effects. Propranolol administration resulted in a significant reduction in cardiac activity, demonstrating effective β-receptor blockade. When adrenaline was administered in the presence of propranolol, the responses were markedly reduced, and a rightward shift in the dose-response curve was observed without a decrease in maximum response (Emax), confirming competitive antagonism. The findings of this study highlight the role of β-adrenergic receptors in cardiac regulation and support the therapeutic significance of β-blockers in managing cardiovascular disorders.