NEURONAL AND GLIAL LOCALIZATION OF NMDA RECEPTORS IN THE CEREBRAL-CORTEX

The crucial role of glutamate receptors of the N-methyl-D-aspartate (N MDA) type in many fundamental cortical functions has been firmly estab lished, as has its involvement in several neuropsychiatric diseases, b ut until recently, very Little was known of the anatomical localizatio n of NMDA receptors in the cerebral cortex of mammals. The recent appl ication of molecular biological techniques to the study of NMDA recept ors has allowed the production of specific tools, the use of which has much increased our understanding of the localization of NMDA receptor s in the cerebral cortex. In particular, immunocytochemical studies on the distribution of cortical NMDA receptors have: 1. Demonstrated the preferential localization of NMDA receptors in dendritic spines, in l ine with previous work; 2. Disclosed a thus far unknown fraction of pr esynaptic NMDA receptors on both excitatory and inhibitory axon termin als; and 3. Shown that cortical astrocytes express NMDA receptors. The se studies indicate that the effects of cortical NMDA receptor activat ion are not caused exclusively by the opening of NMDA channels on neur onal postsynaptic membranes, as previously assumed, and that the activ ation of presynaptic and glial NMDA receptors can contribute significa ntly to these effects.