Serotonin uptake and imipramine binding in the blood platelets of obsessive-compulsive disorder patients

14C-Serotonin (5-HT) uptake and 3H-imipramine binding (IB) were studied in the blood platelets of 20 obsessive-compulsive disorder (OCD) patients, 53 normal controls (5-HT uptake) and 32 normal controls (IB binding). The maximum number of binding sites (Bmax) was significantly decreased in OCD patients compared to normal controls, but there was no difference in the affinity for 3H-imipramine (Kd). The affinity for 5-HT uptake (Km) was also decreased in the OCD patients but the maximum velocity of 5-HT uptake sites (Vmax) was not significantly different in OCD patients and normal volunteers. There were trends for the Slowness Subscale of the Maudsley Obsessional-Compulsive Inventory (MOCI) to be positively correlated with the Km of 5-HT uptake (p = 0.094), whereas the Global Scale, Checking Subscale, and Doubting Conscientiousness Subscale of MOCI were negatively correlated with the Kd of IB (p = 0.066, p = 0.08, and p = 0.062, respectively). The results provide further evidence for the dysfunction of the serotonergic system in OCD.