Effects of meta-chlorophenylpiperazine on cerebral blood flow in obsessive–compulsive disorder and controls

Background: A number of studies have shown that the serotonin receptor agonist meta-chlorophenylpiperazine (mCPP) can exacerbate symptoms in patients with obsessive–compulsive disorder (OCD). The aim of the present study was to study the effect of this compound on regional cerebral blood flow (rCBF) in patients and controls. Methods: Seven OCD patients and 8 healthy controls were randomly allocated to a double-blind challenge study with mCPP (0.5 mg/kg orally). rCBF was measured by 99m-Tc-hexamethyl-propyleneamineoxime single photon emission computed tomography. Results: mCPP did not induce OCD symptoms in patients, but caused a significant decrease in rCBF in OCD patients, but not in controls. The decrease was seen in the reference regions cerebellum and whole brain, and in the frontal cortex, caudate nucleus, putamen, and thalamus. Conclusions: The effect of mCPP on the reference regions in patients posed methodological problems in the normalization methods. A possible role of the cerebellum in OCD is discussed.