NMDA and AMPA receptor subunit protein expression in the rat vestibular nucleus following unilateral labyrinthectomy

We examined the expression of the NR1 and NR2A subunits of the N-methyl-D-aspartate (NMDA) receptor, and the GluR2 subunit of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptor, in the ipsilateral and contralateral vestibular nucleus complexes (VNCs) at 10 h and 2 weeks following unilateral vestibular deafferentation (UVD) in rats, in order to directly test the hypothesis that the behavioural recovery following UVD ('vestibular compensation') is associated with an up-regulation of NMDA receptors. We found no significant changes in NR1 or NR2A expression at 10 hs or 2 weeks post-op. compared to sham and anesthetic controls. We did find a significant (p < 0.01 and p < 0.05) increase in GluR2 expression in both VNCs at 10 h but not 2 weeks post-op. compared to sham and anesthetic controls; however, comparison over time post-UVD failed to detect a significant difference, suggesting that it was small and transient at best. These results add further evidence to the conclusion that NMDA receptors do not undergo up-regulation in the ipsilateral VNC during vestibular compensation.