Objective: To evaluate current hypothesis regarding the pathophysiology of obsessive–compulsive disorder (OCD) by studying the serotonin receptor binding in patients with OCD using single photon emission computerized tomography (SPECT).
Method: We studied nine patients (four men and five women, age range 21–56 years) fulfilling the DMS-III-R criteria for OCD using SPECT and the serotonin transporter (SERT) tracer 123I-β-CIT. SERT binding potential (BP2) was determined by Logan plot derived from seven scans obtained during 10–400 min.
Results: The binding of 123I-β-CIT in midbrain-pons was reduced in OCD patients when compared with controls (BP2 0.97 ± 0.07 vs. 0.84 ± 0.12, P = 0.011). There was no correlation between BP2 and any of the clinical variables (age at onset, disease duration, and Yale-Brown Obsessive–Compulsive Scale score).
Conclusion: This study suggests a reduced serotonergic input into the fronto-subcortical circuits in OCD, thereby diminishing the inhibitory regulation of serotonin on these circuits.