Expression of glutamate (AMPA type) and γ-aminobutyric acid (GABA)A receptors in the rat caudal trigeminal spinal nucleus

Abstract The localization of GABA A receptor γ1 and γ2 subunits and the AMPA-type glutamate receptor subunits GluR1 and GluR2/3 were identified in the caudal trigeminal spinal tract nucleus (TNC) by immunohistochemistry using specific antibodies. The receptor species on the projecting neurons to the thalamus in TNC were also examined. A retrograde tracer, Fluoro-gold (FG), was injected into the thalamus, and the sections were simultaneously labeled with the antibodies. Injection of FG into the ventral posteromedial nucleus of the thalamus resulted in labeling of scattered neurons contralaterally in the TNC. Most of the neurons labeled by retrograde tracing also showed γ1- and γ2-like immunoreactivity, while many of the neurons containing FG lacked GluR1- and GluR2/3-like immuno-reactivity. These findings show that neurons projecting to the thalamus from the TNC receive GABAergic input via GABA A receptors containing γ1 and γ2 subunits, while many neurons expressing the AMPA-type receptor did not project to the thalamus.