Reserpine-induced changes in cardiac adrenergic receptors.

Using radioligand binding techniques, the effect of reserpine pretreatment on ventricular adrenergic receptors from guinea pig was studied. [3H]Prazosin and [3H]dihydroalprenolol were used to label alpha 1- and beta-adrenergic receptors, respectively. Administration of 2.5 mg/kg reserpine for 2 days caused a significant increase in the number of beta-adrenergic receptors with no effect on their affinity to respective ligands. Similar reserpine pretreatment did not affect either density or affinity of alpha 1-adrenergic receptors for ligands. The results may explain the previous report from our laboratory in which an identical reserpine pretreatment selectively enhanced the inotropic responsiveness of the working guinea pig heart to isoproterenol.