Effect of spinal cord lesions on convulsive activity induced by intrathecal morphine

Non-specific convulsive behavior induced by intrathecal (IT) morphine microinjection appears to be tonically modulated by centrifugal pathways originating within the brain since the frequency of IT morphine-induced hindlimb seizures and myoclonic twitches are both increased following spinal transection. These effects on convulsant activity are dissociable by selective neural lesions. Bilateral dorsolateral funiculus lesions potentiate seizure activity whereas ventral funiculus lesions and, to a lesser extent, interruption of cerebral cortical influences enhance myoclonic twitch activity. These initial studies indicate that distinct supraspinal centers differentially modulate myoclonic and seizure activity and suggest that an understanding of these systems may have clinical implications for the control of convulsant activity.