Lesions of the dorsal spinal cord decrease the duration of contact defensive immobility (animal hypnosis) in the...

Rabbits received either bilateral dorsal or unilateral dorsolateral spinal cord lesions. The duration and incidence of contact defensive immobility (CDI; animal hypnosis) were tested in these rabbits and in intact controls. Neither of the spinal cord lesions affected the number of CDI inductions, but rabbits with lesions of the dorsal spinal cord exhibited significantly shorter durations of CDI than either of the other groups which did not differ from each other. These results are interpreted to indicate that the somesthetic systems that ascend in the dorsal spinal cord are important for the maintenance, but not the initiation, of CDI.