An in situ hybridization and immunofluorescence study of glycinergic receptors and gephyrin in the vestibular nuclei of the intact and unilaterally labyrinthectomized rat.

We investigated whether the expression of glycinergic receptor (GLYR) subunits of gephyrin and of their mRNAs in the medial vestibular nuclei are affected following unilateral labyrinthectomy. Specific radioactive oligonucleotide probes recognizing the sequences encoding alpha1-3 and ss subunits of GLYR and the anchoring protein gephyrin were used to probe sections of vestibular nuclei. Signals in these in situ hybridization experiments were detected with film or by emulsion photography. Animals were killed at various times following the lesion: 5 h, 1, 3, 8, 30 and 60 days. Specific monoclonal GLYR and gephyrin antibodies were also used to determine GLYR and gephyrin immunoreactivity in control and operated rats (5 h, 1, 3 and 8 days post-lesion). In normal animals, several brainstem regions including the lateral, medial, superior and inferior vestibular nuclei contained mRNAs for gephyrin and the alpha1 and beta subunits of GLYR, and expressed the GLYR and gephyrin polypeptides. In unilaterally labyrinthectomized rats, no asymmetry was detected on autoradiographs between the two medial vestibular nuclei with any of the oligonucleotide probes used, or at any time following the lesion. No difference in the immunofluorescence staining was observed between the intact and deafferented medial vestibular nuclei of lesioned animals or between the vestibular nuclei of lesioned and controls rats. Thus, deafferentation of the vestibular nuclei did not affect the expression of gephyrin, of the various GLYR subunits, or of their mRNAs in the deafferented and intact medial vestibular nuclei. It is therefore unlikely that GLYR and gephyrin modulation contribute significantly to the recovery of the resting discharge of the deafferented medial vestibular neurons and consequently to the restoration of a normal posture and eye position.