Melatonin and Cortisol values in plasma were measured hourly over 24 hours in six depressed patients and six normal volunteers before treatment and after one and three weeks of treatment with desipramine. The normal volunteers were further tested one week after withdrawal of desipramine. The mydriatic effects of tyramine and phenylephrine eye drops were also recorded in the normal volunteers.
In neither group of subjects did desipramine treatment reduce melatonin secretion, suggesting that functionally significant down-regulation of beta andrenoceptors was not caused by this treatment. Melatonin secretion was significantly increased after three weeks of treatment in depressed patients. This increase was not found in normal subjects.