OBJECTIVETo measure the content of arginine vasopressin (AVP) and V1b receptor expression in the brain areas in rats of both genders and after rotatory stimulation and thereby, to identify the involvement of AVP in the mechanisms of motion sickness.

METHODSSD rats were rotated about a horizontal axis for 30 min, the content of AVP and the expression of V1b receptors in some brain areas were then measured with radioimmunological analysis and immunofluorescent method respectively.

RESULTSWe proved that: (1) In female rats, the content of AVP in each area we measured in rotation group did not show any significant change compared with that in control group (P > 0.05). In male rats, the AVP content of control group in each area was higher than that of female rats, but reduced by rotatory stimulation in forebrain, diencephalon and pontine (P < 0.05 or 0.01), however, the changes in the cerebellum and medulla of rotation group were not significant (P > 0.05). (2) The positive cell number of V1b receptor expression in the supraoptic nucleus of female rats in rotation group was lower, but higher in the vestibular nucleus and area postrema than that in control group (P < 0.05 or 0.01). In male rats, the V1b receptor positive cell number in the supraoptic nucleus and vestibular nucleus of rotation group did not show significant change compared with that of control group (P > 0.05), but a slight increase in the medulla of rotation group rats was observed (P < 0.05).

CONCLUSIONThe gender difference in the susceptibility of motion sickness is potentially associated with the discrepancies in AVP content in the forebrain, diencephalon and pontine, in the expression of AVP-V1 receptors in the vestibular nucleus and area postrema, and in responses to rotatory stimulation, and that the vestibular nucleus and area postrema may be the areas targeted by AVP V1 receptor antagonist for antimotion sickness.