Serotonin-induced platelet intracellular Ca2+ responses in untreated depressed patients and imipramine responders in remission

Background: Intracellular Ca2+ metabolism in platelets has been investigate d as a peripheral marker of affective disorders. Methods: We investigated the intracellular free Ca2+ concentration in plate lets in both untreated depressed patients with no medications and patients in remission who were treated by imipramine (IMI) (IMI responders) using a Ca2+-sensitive fluorescent probe fura-2. Results: The increases in intracellular free Ca2+ concentration in platelet s induced by stimulation with serotonin (5-HT) ([Ca2+]Delta) were significa ntly higher in both the untreated patients and the IMI responders compared with healthy controls; however, there were no significant differences in th e basal Ca2+ levels in the platelets ([Ca2+]B) among the three groups. On t he other hand, in the; IMI responders, we observed positive correlations be tween the duration of the remission and [Ca2+]B, but not [Ca2+]Delta. Conclusions: Our present data suggest that the enhancement of 5-HT2A-induce d Ca2+ responses persisted after remission in depressed patients, and that the: duration of the remission is a factor varying the intracellular basal Ca2+ levels. (C) 1999 Society of Biological Psychiatry.