Platelet intracellular calcium in patients with recurrent affective disorders.

Forty-four subjects with a history of a major recurrent affective disorder in remission and who were either on no medication or taking a single dose of psychotropic medication were conscripted together with matched controls. The fluorescent indicator fura 2 was used to measure intracellular calcium in platelets and estimations were made of total serum and ionised calcium as well as of whole blood serotonin. Intracellular calcium was measured in the resting state as well as after stimulation with thrombin, platelet activating factor and serotonin. No significant differences were found between the 17 subjects with a diagnosis of bipolar disorder or the 27 subjects with recurrent unipolar depression and their matched controls. Intracellular calcium measures were significantly higher in the lithium treated group after stimulation with 5HT, whereas the subjects taking tricyclic antidepressants did not differ significantly from their controls on any measure. Serum calcium was found to be significantly higher in those subjects taking lithium. These findings suggest that the measurement of intracellular calcium is not a useful trait marker in affective disorders. Lithium appears to enhance the 5HT induced rise of intracellular calcium.