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 (B_max) was significantly decreased in OCD patients compared to normal controls, but there was no difference in the affinity for ³H-imipramine (K_d). The affinity for 5-HT uptake (K_m) was also decreased in the OCD patients but the maximum velocity of 5-HT uptake sites (V_max) 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 K_m of 5-HT uptake (p = 0.094), whereas the Global Scale, Checking Subscale, and Doubting Conscientiousness Subscale of MOCI were negatively correlated with the K_d 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.