Melatonin response to clonidine administration in depression: indication of presynaptic α2-adrenoceptor dysfunction

Background: The aim of this study was to investigate α2-adrenoceptor sensitivity in depression, by using melatonin response to clonidine administration as an index of α2-adrenoceptor functioning. Method: 35 depressed subjects and 41 healthy controls were assessed for overnight urinary melatonin pre- and post-administration of oral clonidine. Results: Administration of clonidine significantly reduced melatonin concentrations in depressed patients but not in control subjects. Limitation: A single oral dose (0.15 mg) of clonidine was administered. Conclusions: Further indication is provided for presynaptic α2-adrenoceptor dysfunction in depression with the application of an alternative pharmacological challenge method.