Antidepressants. Current concepts of mode of action

Two approaches have been followed in attempting to elucidate the mechanisms of action of antidepressants. The first involves studies on the chronic effects of antidepressants and ECT on neurotransmitter receptor function in the rat brain. Such studies suggest that antidepressants decrease alpha 2 and beta-adrenoceptor function, increase alpha 1 receptor function, reduce 5-HT1A and dopamine autoreceptor function and increase GABA B function; changes also occur in 5-HT2 receptor function with antidepressants decreasing while ECT increases the activity of these receptors. The second approach involves studying platelets, lymphocytes and amine metabolites in the body fluids of depressed patients before and following effective treatment. Results of these studies suggest that while alpha-adrenoreceptors are largely unchanged, beta-receptors are increased and 5-HT2 receptors decreased in the depressed patient but normalise following effective treatment irrespective of the type of treatment. Such findings emphasize the importance of receptor adaptations in evaluating the mode of action of antidepressant treatments.