Expression of M2/M3 muscarinic receptors in medial vestibular nucleus in guinea pigs with recurrent vertigo

RAO Xiuli; YIN Shihua; HOU Tao; ZHU Ziang; LONG Ji

doi:10.3969/j.issn.1672-2922.2016.05.024

Abstract：Objective To study changes in expression of M2 and M3 muscarinic receptor subtypes in the medial ves-tibular nucleus using a guinea pig model of recurrent vertigo caused labyrinthine fistula. Method Adult guinea pigs (n=88) were randomly divided to receive sham-operation (group A, n=8), unilateral labyrinth lesioning (group B, n=40), or laby-rinthine fistula modeling and pneumatic otoscope treatment (group C, n=40). Guinea pigs in groups B and C were randomly selected to be sacrificed at 1 day, 3 days, 1 week, 2 weeks or 3 weeks post-operatively (n=8 at each time point), while ani-mals in group A were sacrificed at 3 weeks post-operation. Following fixative perfusion, the brain stem was harvested and expression of muscarinic receptors M2 and M3 subtypes in the MVN was examined by immunohistochemistry and com-pared among different groups. Results Muscarinic receptor M2/M3 subtypes decreased in MVN on both sides after opera-tion in animals from groups B and C. Expression was the lowest at day 1, and rose from day 3 to day 7 after operation. Sig-nificant difference was seen between groups A and C at day 7 after operation (P<0.05), but not between groups B and A. At 2 weeks after operation, there was no difference between groups C and A. M2/M3 expression in group C was also weaker than that in group B group before two weeks after operation). There was no side-to-side difference in any groups. Conclu-sion 1. M2 and M3 muscarinic receptor subtypes are expressed in the MVN in guinea pigs, with seemingly less M3 receptor expression than M2 receptor expression. These receptors may promote the normal process in the early stage of vestibular compensation. 2. In addition to the involvement of the cholinergic system, vestibular compensation may also involve other neurotransmitters or chemical substances. 3. The data provide additional evidence supporting the successful modeling of re-current vertigo by labyrinthine fistula.