Recent studies have demonstrated that five subtypes (M1-M5) of muscarinic acetylcholine receptor (mAChR) are expressed in the vestibular periphery.However,the exact cellular location of the mAChRs is not clear.In this study,we investigated whether there is the expression of M1-M5 muscarinic receptor mRNA in isolated type Ⅱ vestibular hair cells of guinea pig by using single-cell RT-PCR.In vestibular end-organ,cDNA of the expected size was obtained by RT-PCR.Moreover,mRNA was identified by RT-PCR from individually isolated type Ⅱ vestibular hair cells (single-cell RT-PCR).Sequence analysis confirmed that the products were M1-M5 mAChR.These results demonstrated that M1-M5 mAChR was expressed in the type Ⅱ vestibular hair cells of the guinea pig,which lends further support for the role of M1-M5 mAChR as a mediator of efferent cholinergic signalling pathway in vestibular hair cells.