Changes in Fos and Jun expression in the rat brainstem in the process of vestibular compensation.

By means of immunohistochemical technique, we examined the changes in Fos and Jun expression after unilateral labyrinthectomy (UL) in the rat brainstem. We observed Fos-like immunoreactivity (-LIR) in the ipsilateral medial vestibular nucleus (ipsi-MVe), the contralateral prepositus hypoglossal nucleus (contra-PrH) and the contralateral inferior olive beta subnucleus (contra-IOb) 1 h after UL. Then, Fos expression in the contra-PrH and the contra-IOb disappeared 3 days after surgery. However, we still found the residual expression in the ipsi-MVe, which disappeared within 7 days. On the other hand, no Jun-LIR was detected in the vestibular or vestibular-related nuclei before or after the operation. Fos expression in the MVe, PrH and IOb was induced immediately after UL. Then, the Fos expression disappeared in accordance with the development of the vestibular compensation. These findings suggest that the transient Fos expression in the vestibular and vestibular related nuclei is a trigger of vestibular compensation.