Comparison of various motion stimuli on motion sickness and acquisition of adaptation in Suncus Murinus

Effects of various types of motion stimuli were compared to investigate optimum method to elicit motion sickness and adaptation in Suncus murinus (suncus). Three different direction of shaking in the horizontal plane, back and forth, right and left and revolving, induced emetic response to the similar extent. However, vertical shaking was far less effective in inducing motion sickness. Mild and severe horizontal shaking (15 min per day) was continued for 14 days and emetic response to standard motion stimulus was compared before and after the training. The severe daily acceleration strongly depressed the susceptibility to motion stimulus. The mild acceleration which was not emetic stimulus in itself also remarkably attenuated the vomiting response to standard motion stimulus. These results indicate that 1) the emetic responsiveness of the suncus does not depend on the modes of shaking as long as the direction is in the horizontal plane, 2) the suncus is relatively refractory to the vertical linear acceleration and 3) the adaptation to motion stimulus does not develop on the latest peripheral steps of the vomiting reflex pathways.