Platelet Cytosolic Calcium Responses to Serotonin in Depressed Patients and Controls: Relationship to Symptomatology and Medication

Background: Serotonin produces an exaggerated rise in platelet cytosolic calcium (Δ[Ca++]i) in patients with mood disorders. Studies on patients with bipolar disorder consistently demonstrate calcium abnormalities. By comparison, data on patients with major depression are more variable. Methods: To determine causes of variability, we utilized Fura-2 loaded platelets to compare changes in platelet intracellular calcium levels (Δ[Ca++]i) following serotonin stimulation in 24 patients with major depression and in 20 controls. We also sought relationships between the Δ[Ca++]i responses and scores on clinical depression and anxiety scales. Results: We found positive correlations between Δ[Ca++]i responses and the clinical scales across all subjects. Furthermore, depressed patients with high anxiety had significantly increased Δ[Ca++]i responses compared to depressed patients with low anxiety. In addition, patients receiving selective-serotonin reuptake inhibitors (SSRIs) demonstrated reduced Δ[Ca++]i responses compared to patients not on SSRIs. Conclusions: Since elevations in [Ca++]i mediate platelet aggregation and secretion cascades, the enhanced responsivity observed in depressed, and in particular anxious, depressed patients may contribute to their increased risk for vascular disease.