Decreased platelet serotonin uptake in bipolar I patients.

The 5HT transporter complex in platelets is similar to that in the brain and thus widely used in biological psychiatry as a peripheral marker of the 5HT system. Our study aim was to measure 14C-5HT uptake parameters (Vmax and Km) in platelets from 12 patients affected by bipolar disorder, as compared with 12 healthy controls. The uptake assay was performed according to the method of Arora and Meltzer (1981). The results showed that the Vmax was significantly lower in bipolar patients than in healthy controls, with no modification of the Km. These preliminary data would indicate therefore that the mechanism of 5HT transport is altered in platelets of bipolar patients.