Effects of amygdala or hippocampus lesion on hypergravity-induced motion sickness in rats

We examined the effects of amygdala lesion (AL) or hippacampal lesion (HL) on hypergravity-induced motion sickness in rats. Rats do not vomit, but the behavior known as pica, the eating of non-nutritive substances such as kao lin, can be used as an index of motion sickness. In the present study, hype rgravity-induced kaolin intake and apomorphine-induced kaolin intake were m easured before and after brain lesions. After AL, hypergravity-induced kaol in intake and the ratio of the hypergravity- to apomorphine-induced kaolin intakes were decreased. These results indicate that AL suppressed motion si ckness more than pica behavior itself, suggesting that the amygdala plays a n important role in the development of motion sickness in rats. Conversely, after HL, hypergravity-induced kaolin intake was increased, as was the rat io of the hypergravity- to apomorphine-induced kaolin intakes. These result s indicate that HL aggravates motion sickness induced by hypegravity in rat s, suggesting that the hippocampus counteracts motion sickness.