Motion sickness reflex arc bypasses the area postrema in cats

Motion-induced vomiting was studied in cats exposed to vertical sinusoidal oscillation on a spring-suspended platform. Two groups of five cats each, namely, motion-untested and motion sickness-susceptible, were subjected to chronic ablation of the area postrema. Motion sickness occurred postoperatively in all the previously untested cats, and in four of the five previously susceptible cats. Statistical comparison with normal cats indicated that the operated cats were significantly more susceptible to motion sickness. The manifest loss of susceptibility in one cat with a lesion is attributed to excessive peripostremal damage. It is concluded from these results that the area postrema is not an essential link in the reflex arc of motion-induced vomiting.