Tonic descending inhibition in the stingray's spinal cord.

Reflexes elicited by peripheral nerve stimulation were compared in decerebrated stingrays with the spinal cord intact, after a lesion of the dorsal spinal cord and after spinal transection. Reflexes elicited in decerebrated stingrays are tonically inhibited. Lesions of the dorsal spinal cord release this tonic descending inhibiton. The tonic descending inhibitory system in stingrays is comparable to that of mammals.