Temporary spinalization reverses the inhibitory effect of cyclazocine on the nociceptive response of rabbit spinal dorsal horn lamina V-type neurons.

Cyclazocine (0.5 mg/kg i.v.) inhibited the activity of lamina V-type neurons of the rabbit spinal dorsal horn induced by intra-arterial injection of bradykinin. This inhibition was reversed during temporary spinalization by cold block. Thus, cyclazocine probably depresses nociceptive transmission in the spinal dorsal horn by facilitating descending inhibitory systems which originate from supraspinal structures.