Vestibular, central and gastral triggering of emesis. A study on individual susceptibility in rats.

Using kaolin intake as a behavioral index of emesis in rats, we examined the relationship between susceptibility to motion sickness and to emesis induced by apomorphine or copper sulfate. Rats showed a wide variation in susceptibility to motion sickness. Significant positive correlations were found between susceptibility to motion sickness and to emesis induced by intraperitoneal administration of apomorphine and by oral administration of copper sulfate. Motion, apomorphine and copper sulfate induce emesis through different receptors, so these findings suggest that the sensitivity of a common locus of emesis, presumably the emetic center in the brain stem, is one determinant of individual differences in susceptibility to motion sickness.