Objective: To investigate peripheral β-adrenoceptor sensitivity in depression by assessing urinary melatonin pre- and post-administration of atenolol.
Method: Overnight urinary melatonin pre- and post-administration of 100 mg oral atenolol was assessed in 36 depressed subjects and 47 controls.
Results: Baseline melatonin was significantly lower in depressed patients than controls (P=0.004). Melatonin following atenolol administration was strongly reduced in both groups (P < 0.0001). This reduction depends on whether the subject is a high or low (cutoff: 0.25 nmol/l) baseline melatonin excretor (P=0.025) and on whether he is depressed being a low excretor (P=0.048). A negative correlation (P=0.007) was found between melatonin decrease after atenolol and the Montgomery-Asberg Depression Rating Scale score.
Conclusion: Atenolol strongly reduces melatonin in depressed and control subjects; this decrease relates inversely to the severity of depressive symptoms. Furthermore, responsiveness to atenolol differs between low melatonin depressed patients and low excretor controls, alluding to β-adrenoceptor up-regulation in a subtype of depression.