Treatment response in depressed patients with enhanced Ca mobilization stimulated by serotonin.

Serotonin (5-HT)-stimulated intraplatelet calcium (Ca) mobilization has been shown to be enhanced in nonmedicated depressive patients by many studies. However, there has not been any longitudinal follow-up study of this parameter. We examined the relationship between treatment response and pretreatment value of the 5-HT-induced Ca response. The 5-HT(10 microM)-induced intraplatelet Ca mobilization was measured in 98 nonmedicated depressive patients (24 bipolar disorders, 51 melancholic major depressive disorders, and 23 non-melancholic major depressive disorders). These patients were followed up prospectively for a further period of five years. The depressed patients with enhanced Ca response to 5-HT in bipolar disorders exhibited a good response to mood stabilizers but those with major depressive disorders showed a poor response to antidepressants. These findings suggest the possibility that the 5-HT-induced intraplatelet Ca response may be a good predictor of treatment response in depressed patients. Longer longitudinal follow-up studies are needed in larger samples to examine if this parameter may be a specific biological marker for unipolar-bipolar dichotomy.