NUCLEUS-SPECIFIC AND CELL-SPECIFIC EXPRESSION OF NMDA AND NON-NMDA RECEPTOR SUBUNITS IN MONKEY THALAMUS

Subcortical and corticothalamic inputs excite thalamic neurons via a d iversity of glutamate receptor subtypes. Differential expression of al pha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA), kainat e, and N-methyl-D-aspartate (NMDA) receptor subunits (GluR1-4; GluR5-7 ; NR1, NR2A-D) on a nucleus- and cell type-specific basis was examined by quantitative in situ hybridization histochemistry and by immunocyt ochemical staining for receptor subunits and colocalized gamma-aminobu tyric acid (GABA) or calcium binding proteins. Levels of NMDA subunit expression, except NR2C, are higher than for the most highly expressed AMPA (GluR1,3,4) and kainate (GluR6) receptor subunits. Expression of NR2C, GluR2, GluR5, and GluR7 is extremely low. Major differences dis tinguish the reticular nucleus and the dorsal thalamus and, within the dorsal thalamus, the intralaminar and other nuclei. In the reticular nucleus, GluR4 is by far the most prominent, and NMDA receptors are at comparatively low levels. In the dorsal thalamus, NMDA receptors pred ominate. Anterior intralaminar nuclei are more enriched in GluR4 and G luR6 subunits than other nuclei, whereas posterior intralaminar nuclei are enriched in GluR1 and differ among themselves in relative NMDA re ceptor subunit expression. GABAergic intrinsic neurons of the dorsal t halamus express much higher levels of GluR1 and GluR6 receptor subunit s than do parvalbumin- or calbindin-immunoreactive relay cells and low or absent NMDA receptors. Relay cells are dominated by NMDA receptors , along with GluR3 and GluR6 subunits not expressed by GABA cells. Hig h levels of NR2B are found in astrocytes. Differences in NMDA and non- NMDA receptor profiles will affect functional properties of the thalam ic GABAergic and relay cells. J. Comp. Neurol. 397:371-393, 1998. (C) 1998 Wiley-Liss, Inc.