AMPA-SELECTIVE GLUTAMATE-RECEPTOR SUBUNITS AND THEIR RELATION TO GLUTAMATE-LIKE AND GABA-LIKE IMMUNOREACTIVE TERMINALS IN THE NUCLEUS SUBMEDIUS OF THE RAT

Glutamate plays an important role in supraspinal nociceptive systems. Thus, glutamate is present in the nucleus submedius of the medial thal amus, a major relay for nociceptive information. In this study, immuno reactivity for the four subunits (GluR1-4) of ha-amino-3-hydroxy-5-met hyl-4-isoxasoleproprionate (AMPA) receptors was examined by a preembed ding immunohistochemical method in order to evaluate the presence of t his glutamate receptor subtype in the nucleus submedius. Combining the preembedding method with a postembedding immunogold technique, we fou nd that AMPA receptor-like immunoreactivity was present postsynaptical ly to glutamatergic terminals but not to terminals containing gamma-am inobutyric acid (GABA). These findings suggest a role for AMPA recepto rs in excitatory synaptic transmission in the nucleus submedius of the rat thalamus.