Selective antagonist [3H]SR141716A binding to cannabinoid CB1 receptors is increased in the anterior cingulate cortex in schizophrenia

Previous studies suggest that long-term cannabis use causes cognitive impairment, including lack of motivation and impaired attention, conditions that also resemble core negative symptoms of schizophrenia. The anterior cingulate cortex (ACC) plays an important role in normal cognition, particularly in relation to motivation and attention. This could suggest that changes in the cannabinoid (CB) system might be present in the ACC of patients suffering schizophrenia. The present study examined the distribution and density of CB1 cannabinoid receptors in the left ACC taken postmortem from patients with schizophrenia (n=10) and matched control subjects (n=9). Radioligand binding of 3H]SR141716A, an antagonist that specifically targets CB1 receptors of the endogenous cannabinoid system, was examined on ACC sections using quantitative autoradiography. CB1 receptors had a homogeneous distribution among the layers of ACC. A significant 64% increase in 3H]SR141716A specific binding to CB1 receptors was found in the schizophrenia group as compared to the control group (mean+/-S.E.M.: 46.15+/-6.22 versus 28.02+/-4.20 fmol/mg estimated tissue equivalents; p=0.03). The present results support the suggestion that changes in the endogenous cannabinoid system in the ACC may be involved in the pathology of schizophrenia particularly in relation to negative symptoms.