Abnormalities in the anterior cingulate cortex have been reported in patients with
schizophrenia, and have been implicated in the pathophysiology of this disorder. In the present study, we have examined
antipsychotic-sensitive binding sites in the left anterior cingulate cortex of
schizophrenia patients and controls. Using quantitative autoradiography and [(3)H]
spiperone as a
ligand, both saturation and competition experiments were performed in post-mortem brain tissue obtained from six
schizophrenia and six control cases. Saturation experiments revealed that the maximum number of [(3)H]
spiperone binding sites was significantly reduced by 31% in the
schizophrenia group as compared to the control group (65.3+/-5.6 fmol/mg tissue versus 94.2+/-7.3 fmol/mg tissue). Increased dissociation constant was also observed in the
schizophrenia group (2.2+/-0.4 nM versus 1.3+/-0.2 nM), but was not statistically significant (P=0.07). Competition experiments were performed in order to examine the pharmacological profile of [(3)H]
spiperone binding, and revealed that: (i) displacement of [(3)H]
spiperone binding by
clozapine and
mianserin was significantly reduced in the
schizophrenia group as compared to the control group (-26% and -16% respectively); (ii) the order of displacement potency of the drugs tested was:
haloperidol>
mianserin>
butaclamol approximately
risperidone>
clozapine>2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene. Our results suggest a reduction of
antipsychotic-sensitive binding sites in the anterior cingulate cortex of patients with
schizophrenia. Such abnormality could lead to an imbalance in
neurotransmitter regulation in the anterior cingulate cortex which may contribute to the emergence of some symptoms of
schizophrenia.