Rapid changes in central beta-adrenergic receptors after chronic intravenous infusion of antidepressants

The effects of intravenous infusion of desipramine (1, 3, 10, and 60 mg/kg/24 hr), amitriptyline, zimelidine, iprindole (3, 10, 30, 60, and 100 mg/kg/24 hr each), imipramine (10, 30, and 100 mg/kg/24 hr), or U-48,753E (1, 3, 10, and 30 mg/kg/24 hr) on the density of central beta-adrenergic receptors were investigated in Sprague-Dawley rats. A comparative study with oral desipramine (3 mg/kg/24 hr) for 74 hrs was also carried out. Desipramine, amitriptyline, zimelidine, iprindole, imipramine, and U-48,753E reduced the density of beta-adrenergic receptors in the cerebral cortex, and the effect seems to be dose-dependent. In the oral study, desipramine failed to down-regulate beta-adrenergic receptors. These results indicate that down-regulation of beta-adrenergic receptors can be rapidly achieved by intravenous infusion of drugs.