Monoamine-related markers of depression: changes following treatment.

Changes in adrenoceptor and serotonin receptor activities, and platelet serotonin uptake, in a group of moderately depressed patients before and during treatment have been monitored. alpha 2 and beta-adrenoceptor densities on platelets and lymphocytes were markedly higher before treatment commenced and decreased to approximately control values following clinical response to drug treatment; patients not responding to such treatment failed to show any attenuation of the receptor hypersensitivity. Responders and non-responders showed differing receptor affinity for the ligands at the conclusion of the treatment period. Platelet serotonin receptor activity and uptake were lower before the start of treatment than in those patients who responded to therapy. There was no difference between plasma free and bound tryptophan concentrations of patients and controls, either before or during treatment. The observed changes in receptor function may correlate with changes in the clinical status of depressed patients.