AVP and motion sickness: In the present study, we found that the AVP levels in the PVN were elevated after rotatory stimulus, especially in rats susceptible to motion sickness, which was consistent with other studies showing that vestibular stimulus increased the AVP-expressing cells in the PVN [18], which is likely the source of AVP secreted into blood during the development of motion sickness [7–9] or after motion sickness-inductive rotatory stimulation [39, 40].