The Changes in mGluR2 and mGluR7 Expression in Rat Medial Vestibular Nucleus and Flocculus Following Unilateral Labyrinthectomy

Wen Zhou,Su-Lin Zhang,Wei-Jia Kong,Yang-Ming Leng,Bo Liu,Liu-Qing Zhou,Ren-Hong Zhou

doi:10.3390/ijms141122857

Abstract

It is known that the medial vestibular nucleus (MVN) and the cerebellar flocculus are the key areas, which contribute to the behavioral recovery (“vestibular compensation”) after unilateral labyrinthectomy (UL). In these areas, how the genetic activities of the metabotropic glutamate receptors mGluR2 and mGluR7 performance after UL is unknown. With the means of quantitative real-time PCR, Western blotting, and immunohistochemistry, we analyzed the expression of mGluR2 and mGluR7 in the bilateral MVN and the flocculus of rats in different stages after UL (the 1st, 3rd, and 7th day). Our results show that in the MVN, the mRNA, and protein expressions of mGluR7 were ipsilaterally decreased at the 1st day following UL. However, in the MVN, no change was observed in the mRNA and protein expressions of mGluR2. On the other hand, the mRNA and protein expression of mGluR2 were enhanced in the ipsilateral flocculus at the 1st day following UL, while in the flocculus no change was shown in mGluR7 mRNA and protein expressions. Our results suggest that mGluR2 and mGluR7 may contribute to the early rebalancing of spontaneous resting activity in the MVN.

Highlights

Vestibular compensation is a process of the plasticity of central nervous system (CNS).Traditionally, unilateral labyrinthectomy (UL) has been used as a model for investigating the post-lesional plasticity of vestibular nuclei complex in adult animals [1]
The manifestation due to acute labyrinthine dysfunction such as head tilting toward the operated side, limb extending on the intact side (Figure 1A), body spinning (Figure 1a–f), and circling walk (Figure 1g–p) were observed in all rats at the 1st day after UL
Our results have demonstrated that mGluR7 was down-regulated in the ipsilateral medial vestibular nucleus (MVN) at the 1st day after UL; the mGluR2 was up-regulated in the ipsilateral flocculus at the 1st day after UL

Summary

Introduction

Vestibular compensation is a process of the plasticity of central nervous system (CNS).Traditionally, unilateral labyrinthectomy (UL) has been used as a model for investigating the post-lesional plasticity of vestibular nuclei complex in adult animals [1]. The consequent asymmetry of the resting discharge between the intact and deafferented vestibular nucleus complex (VNC) is thought to induce the severe oculo-motor and postural symptoms shortly following UL [2,3,4,5]. These symptoms rapidly disappear when vestibular compensation (VC). Most current theories of VC assume that the initial drastic asymmetry in the resting discharge of medial vestibular nucleus (MVN) neurons is due to a large imbalance in the reciprocal commissural inhibitory system that links the MVN of the two sides and recovery of resting activity in the deafferented ipsi-lesional MVN neurons partly by counteracting this increased commissural inhibition after UL [7,8,9]. It has been reported that the cerebellum is involved in the neuronal recovery during

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