Platelet ³H-imipramine binding sites in obsessive-compulsive behavior

Several studies indicate a serotonergic dysfunction in patients with obsessive-compulsive disorder (OCD). We examined serotonergic function in OCD by determining platelet ³H-impiramine binding sites in patients with OCD during a drug-free baseline period as well as normal control volunteers. The maximum number of binding sites (B_max) and apparent dissociation constant (K_d) was determined using ³H-imipramine (IMI) as the binding ligand. We observed that the mean ³H-IMI binding B_max (fmol/mg protein) determined in 24 patients with OCD was not significantly different from that in 23 normal control subjects. There were no significant differences in the K_d between patients with OCD and normal control subjects. Our results are thus similar to those reported by Insel et al (1985) and Black et al (1990), who observed no significant differences in platelet ³H-IMI binding between OCD patients and controls; but different from those reported by Weizmann et al (1986), who observed decreased ³H-IMI N_max in OCD patients. The discrepancy in the results in not clear, but may be related to several factors. Our results thus indicate that any abnormality in serotonergic function present in patients with OCD is not related to imipramine binding sites in the platelets. However, the possibility that there may be an abnormal platelet serotonin uptake or other serotonergic function in OCD cannot be ruled out.