Abstract： Objective To observe changes in the expressions of vasopressin receptor 2 (V2R) and aquaporin 2 (AQP2) induced by rotary stimulation in the inner ear of rats with different susceptibilities to motion sickness, and to investigate involvement of the inner ear AVP -V2R-AQP2 signaling pathway in motion sickness.Methods The study was made by using the rat motion sickness model .The degree of conditioned taste aversion (CTA) and pica (kaolin intake) served as indices of susceptibility to motion sickness in rats . The levels of V2R and AQP2 in the inner ears and their changes in the expression after rotary stimulation were detected with Real-time PCR and Western-blot.Results At the basic state, the expression of AQP2 in the susceptible group was higher than that in the insusceptible group , however, the expression of V2R in the susceptible group was lower than that in the insusceptible group .Following rotary stimulation, the expression of AQP2 was increased significantly while the expression of V 2R was decreased instead.Injection of V2R antagonist OPC 31260 significantly inhibited motion sickness induced by rotary stimulation , and the amount of AQP2 expression was decreased considerably .Conclusions Research results revealed that the inner ear AVP -V2R-AQP2 signaling pathway might be involved in the development of motion sickness and the inhibition of the signaling pathway by V2R antagonist could reduce susceptibility of motion sickness .