Co-localization of NMDA receptors and AMPA receptors in neurons of the vestibular nuclei of rats

We are interested in studying the co-localization of NMDA glutamate recepto r subunits (NR1, NR2A/B) and AMPA glutamate receptor subunits (GluR1, GluR2 , GluR2/3 and GluR4) in individual neurons of the rat vestibular nuclei. Im munoreactivity for NR1, NR2A/B, GluR1, GluR2, GluR2/3 and GluR4 was found i n the somata and dendrites of neurons in the four major subdivisions (super ior, medial, lateral, and spinal vestibular nuclei) and in two minor groups (groups x and y) of the vestibular nuclei. Double immunofluorescence showe d that all the NR1-containing neurons exhibited NR2A/B immunoreactivity, in dicating that native NMDA receptors are composed of NR1 and NR2A/B in a het ero-oligomeric configuration. Go-expression of NMDA receptor subunits and A MPA receptor subunits was demonstrated by double labeling of NR1/GluR1, NR1 /GluR2/3, NR1/GluR4 and NR2A/B/GluR2 in individual vestibular nuclear neuro ns. All NR1-containing neurons expressed GluR2/3 immunoreactivity, and all NR2A/B-containing neurons expressed GluR2 immunoreactivity. However, only a bout 52% of NR1-immunoreactive neurons exhibited GluR1 immunoreactivity and 46% of NR1-containing neurons showed GluR4 immunoreactivity. The present d ata reveal that NMDA receptors are co-localized with variants of AMPA recep tors in a large proportion of vestibular nuclear neurons. These results sug gest that cross-modulation between NMDA receptors and AMPA receptors may oc cur in individual neurons of the vestibular nuclei during glutamate-mediate d excitatory neurotransmission and may in turn contribute to synaptic plast icity within the vestibular nuclei. (C) 2000 Elsevier Science BN. All right s reserved.