Selective alterations in ionotropic glutamate receptors in the anterior cingulate cortex in schizophrenia

The anterior cingulate cortex is a brain area of potential importance to our understanding of the pathophysiology of schizophrenia. Previous studies suggest abnormalities in the glutamatergic neurotransmission in the anterior cingulate cortex in schizophrenia patients. In the present study we used quantitative autoradiography to investigate the binding of [3H]MK801, [3H]L-alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA), and [3H]kainate, which respectively label the N-methyl-D-aspartate (NMDA), AMPA, and kainate receptors of the ionotropic glutamate receptor family, in the left anterior cingulate cortex of 10 schizophrenia patients and 10 controls, matched for age, gender, and postmortem interval.AMPA receptor densities were higher in cortical layer II, whereas NMDA receptor densities were higher in cortical layers II-III in the anterior cingulate cortex of both control and schizophrenia group. In contrast, kainate receptors displayed the highest density in cortical layer V. [3H]AMPA binding was significantly increased by 25% in layer II in the schizophrenia group as compared with the control group. Similarly, a significant 17% increase of [3H]MK801 binding was observed in layers II-III in the schizophrenia group. No statistically significant difference was observed for [3H] kainate binding between the schizophrenia and control groups. These results suggest that ionotropic glutamate receptors are differentially altered in the anterior cingulate region in schizophrenia. The increase in [3H]AMPA and [3H]MK801 binding in the superficial layers suggests a postsynaptic compensation for impaired glutamatergic neurotransmission in the anterior cingulate cortex in schizophrenia. The findings add to a growing body of literature that supports a dysfunction of excitatory activity in the anterior cingulate cortex in schizophrenia.