CELLULAR AND SYNAPTIC LOCALIZATION OF NMDA AND NON-NMDA RECEPTOR SUBUNITS IN NEOCORTEX - ORGANIZATIONAL FEATURES RELATED TO CORTICAL CIRCUITRY, FUNCTION AND DISEASE

Excitatory amino acid (EAA) receptors are an important component of ne ocortical circuitry as a result of their role as the principal mediato rs of excitatory synaptic activity, as well as their involvement in us e-dependent modifications of synaptic efficacy, excitotoxicity and cel l death. The diversity in the effects generated by EAA-receptor activa tion can be attributed to multiple receptor subtypes, each of which is composed of multimeric assemblies of functionally distinct receptor s ubunits. The use of subunit-specific antibodies and molecular probes n ow makes it feasible to localize individual receptor subunits anatomic ally with a high level of cellular and synaptic resolution. Initial st udies of the distribution of immunocytochemically localized EAA-recept or subunits suggest that particular subunit combinations exhibit a dif ferential cellular, laminar and regional distribution in the neocortex . While such patterns might indicate that the functional heterogeneity of EAA-receptor-linked circuits, and the cell types in which they ope rate, are based Partly on differential subunit parcellation, a definit ive integration of these anatomical details into current schemes of co rtical circuitry and organization awaits many further studies. Ideally , such studies should link a high level of molecular precision regardi ng subunit localization with synaptic details of identified connection s and neurochemical features of neocortical cells.