AMPA-selective glutamate receptor subunits and their relation to glutamate- 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 thalamus, a major relay for nociceptive information. In this study, immunoreactivity for the four subunits (GluR1-4) of alpha-amino-3-hydroxy-5-methyl-4-isoxasoleproprionate (AMPA) receptors was examined by a preembedding immunohistochemical method in order to evaluate the presence of this glutamate receptor subtype in the nucleus submedius. Combining the preembedding method with a postembedding immunogold technique, we found that AMPA receptor-like immunoreactivity was present postsynaptically to glutamatergic terminals but not to terminals containing gamma-aminobutyric acid (GABA). These findings suggest a role for AMPA receptors in excitatory synaptic transmission in the nucleus submedius of the rat thalamus.