Antidepressant drugs elevate rat pineal and plasma melatonin.

Acute administration in the mid-light phase of a number of antidepressant drugs of different pharmacological profiles elevated pineal and plasma melatonin (measured by radioimmunoassay). Following chronic treatment with the tricyclic antidepressant clomipramine, the elevation was significantly reduced. This may be an effect of reduced beta-adrenergic receptor sensitivity after chronic clomipramine administration, analogous to other findings of reduced beta-adrenergic receptor binding and reduced noradrenaline-sensitive adenylate-cyclase response.