Platelet serotonin uptake dynamic changes in depression: effects of long-term imipramine treatment and clinical...

The characteristics of the serotonin uptake mechanism were measured in blood platelets of depressed patients before treatment and after 3 weeks and 2 months of imipramine therapy. The results were then compared with data from normal volunteers. In the unmedicated, depressed patients, platelets showed two affinity components of serotonin uptake. Both affinity states differed, in opposite directions, from the platelet serotonin uptake in normal volunteers. In the latter, a two-state model was more difficult to establish. Successful imipramine treatment progressively normalized the platelet serotonin uptake changes seen in unmedicated patients. Those changes allowed the membrane to deal with a wider than normal range of extracellular serotonin concentration; they might reflect neuronal compensatory changes resulting from altered extraneuronal serotonin concentrations and leading, directly or via presynaptic receptors, to balancing them. Imipramine treatment assists the adaptive process and accelerates the clinical recovery.