Expression of CB1 cannabinoid receptor in the anterior cingulate cortex in schizophrenia, bipolar disorder, and major depression

The human endogenous cannabinoid system is an appealing target in the investigation of psychiatric disorders. In schizophrenia, endocannabinoids and their receptors are involved in the pathology of the disease. Previous studies reported an increased radioligand binding to cannabinoid receptors 1 (CB1) in schizophrenia, both in the dorsolateral prefrontal cortex and in the anterior cingulate cortex (ACC). We analyzed the expression of the CB1 receptors in the ACC at the protein level using immunohistochemistry. In a quantitative postmortem study, 60 patients suffering from schizophrenia, bipolar disorder, major depression and controls were included. Numerical densities of neurons and glial cells immunopositive for CB1 receptors were evaluated. No evidence of an increased or decreased density of CB1 receptor immunopositive cells in schizophrenia or bipolar disorder was found. In major depression, CB1 receptor immunopositive glial cells in the grey matter were decreased. Furthermore, our data show that different medications have an impact on the expression of CB1 receptors in the ACC.