Localization of NMDA and AMPA receptors in rat barrel field

The aim of this study was to asses the distribution of N- methyl- d -aspartate (NMDA) and α -amino-3-hydroxy- S -methyl-4-isoxazole propionic acid (AMPA) receptors in the barrel field of rat primary somatosensory (SI) cortex using light-microscopic in vitro autoradiography. NMDA receptors were labeled with the competitive antagonist [ 3 H]CGP39653 or with [ 3 H]glycine in the presence of strychnine, and AMPA receptors with [ 3 H]AMPA. In the SI cortex high densities of the NMDA receptor occurred in the supragranular layers and in layer Va. In layer IV high NMDA receptor densities were specifically confined to the barrel hollows. The AMPA binding sites showed less intralaminar variation and no apparent density differences between the barrel hollows and sides in layer IV. It can be concluded that the distribution of NMDA (but not AMPA) receptors in the rat barrel field shows a strong coincidence with the zone of termination of the specific sensory afferents from the ventral posterior nucleus of the dorsal thalamus.