Reserpine-induced hypothermia: participation of beta 1 and beta 2 adrenergic receptors.

In mice, reserpine-induced hypothermia is partly antagonized by clenbuterol, a beta-adrenergic agonist specific for beta 2 receptors, and completely antagonized by dobutamine, a beta-adrenergic agonist specific for beta 1 receptors. In addition, the effects of dobutamine and of clenbuterol are impaired by betaxolol (1 and 4 mg/kg) and unchanged by ICI 118,551 (1 and 4 mg/kg) beta-blocking drugs respectively selective for beta 1 and beta 2 receptors. These results indicate that reserpine-induced hypothermia depends on the beta 1 receptors and lend support to an indirect effect of clenbuterol. After a chronic treatment, clenbuterol-induced antagonism of reserpine hypothermia is facilitated. This facilitation is impaired by ICI 118,551 and by betaxolol but, in this last case, with high doses only. So the facilitation involves beta 2 adrenergic receptors and implies an increase in the sensitivity of beta 1 receptors.