LIGHT AND ELECTRON-MICROSCOPE DISTRIBUTION OF THE NMDA RECEPTOR SUBUNIT NMDAR1 IN THE RAT NERVOUS-SYSTEM USING A SELECTIVE ANTIPEPTIDE ANTIBODY

NMDA receptors play key roles in synaptic plasticity and neuronal deve lopment, and may be involved in learning, memory, and compensation fol lowing injury. A polyclonal antibody that recognizes four of seven spl ice variants of NMDAR1 was made using a C-terminus peptide (30 amino a cid residues). NMDAR1 is the major NMDA receptor subunit, found in mos t or all NMDA receptor complexes. On immunoblots, this antibody labele d a single major band migrating at M(r) = 120,000. The antibody did no t cross-react with extracts from transfected cells expressing other gl utamate receptor subunits, nor did it label non-neuronal tissues. Immu nostained vibratome sections of rat tissue showed labeling in many neu rons in most structures in the brain, as well as in the cervical spina l cord, dorsal root and vestibular ganglia, and in pineal and pituitar y glands. Staining was moderate to dense in the olfactory bulb, neocor tex, striatum, some thalamic and hypothalamic nuclei, the colliculi, a nd many reticular, sensory, and motor neurons of the brainstem and spi nal cord. The densest stained cells included the pyramidal and hilar n eurons of the CA3 region of the hippocampus, Purkinje cells of the cer ebellum, supraoptic and magnocellular paraventricular neurons of the h ypothalamus, inferior olive, red nucleus, lateral reticular nucleus, p eripheral dorsal cochlear nucleus, and motor nuclei of the lower brain stem and spinal cord. Ultrastructural localization of immunostaining w as examined in the hippocampus, cerebral cortex, and cerebellar cortex . The major staining was in postsynaptic densities apposed by unstaine d presynaptic terminals with round or mainly round vesicles, and in as sociated dendrites. The pattern of staining matched that of previous i n situ hybridization but differed somewhat from that of binding studie s, implying that multiple types of NMDA receptors exist. Comparison wi th previous studies of localization of other glutamate receptor types revealed that NMDAR1 may colocalize with these other types in many neu rons throughout the nervous system.