The effect of chronic treatment with antidepressant drugs on salbutamol-induced hypoactivity in rats.

Several lines of evidence (binding studies, reduced responsiveness of brain adenylate cyclase to noradrenergic stimulation, electrophysiological data) indicate that chronic treatment with antidepressant drugs induces subsensitivity of central beta-adrenergic receptors. We studied the effect of acute (single dose) and chronic (14 days, twice daily) treatment with imipramine, desmethylimipramine, amitriptyline, fluvoxamine and citalopram (10 mg/kg, orally) on salbutamol-induced suppression of exploratory activity in rats. This effect of salbutamol was antagonized by chronic, but not acute treatment with antidepressants. Chronic treatment with antidepressants as a rule did not significantly affect exploratory activity. Our results may be regarded as functional evidence at the behavioural level for the subsensitivity of beta-adrenergic receptors.