Immunocytochemical and stereological analysis of GABAB receptor subunit expression in the rat vestibular nucleus following unilateral vestibular deafferentation

The process of behavioral recovery that occurs following damage to one vestibular labyrinth, vestibular compensation, has been attributed in part to a down-regulation of GABAB receptors in the vestibular nucleus complex (VNC) ipsilateral to the lesion, which could potentially reduce commissural inhibition from the contralateral VNC. In this study, we tested the possibility that this occurs through a decrease in the expression of either the GABAB1 or GABAB2 subunits of the GABAB receptor. We used Western blotting to quantify the expression of these subunits in the VNC at 10 h and 50 h following unilateral vestibular deafferentation (UVD) or sham surgery in rats. We then used immunocytochemistry and stereological counting methods to estimate the number of neurons expressing these subunits in the MVN at 10 h and 2 weeks following UVD or sham surgery. Compared to sham controls, we found no significant changes in either the expression of the two GABAB receptor subunits in the VNC or in the number of MVN neurons expressing these GABAB receptor subunits post-UVD. These results suggest that GABAB receptor expression does not change substantially in the VNC during the process of vestibular compensation.