Cardiovascular Effects of Caffeine in Rabbits Involve Beta-1 Adrenergic Receptor Activation

Background: Mechanistic studies indicate that adenosine receptor antagonism may not account for the mechanism of caffeine's cardiovascular action in chronic caffeine users. We, thus, aimed at examining the possible role of catecholamine mechanism in caffeine's cardiovascular action during habitual use. Materials and Methods: Adult male New Zealand rabbits were divided into three groups ( n = 5). Group I rabbits were untreated and served as control whereas groups II and III rabbits were administered with 2 and 6 mg/kg caffeine, respectively, for 28 days. After anesthesia arterial pressure, electrocardiogram and heart rate were recorded. Blood and cardiac tissue samples were collected for analysis. Results: After 28 days of caffeine treatment, cardiovascular parameters were significantly altered. There were increases in catecholamine level, beta-1 receptor expression, adenylate cyclase 9 immuno-reactivity, and cardiac cyclic adenosine monophosphate concentrations. Conclusion: This study demonstrates that caffeine's cardiovascular action in rabbits involves the activation of the beta-1 adrenergic pathway.