Site of anti-nociceptive action of a new benzomorphan derivative ID-1229.

The site of anti-nociceptive action of a new benzomorphan derivative ID-1229, 2-[3-(p-fluorobenzoyl)-1-propyl]-5 alpha, 9 alpha-dimethyl-2'-hydroxyl-6, 7-benzomorphan was investigated using electrophysiological methods. In rabbits, ID-1229 (0.1-0.5 mg/kg) caused slowing in the EEG, and depressed the evoked potentials recorded from the sensory cortex and the Nucleus ventralis posterolateralis of the thalamus elicited by sciatic stimulation. A small dose (1 mg/kg) of ID-1229 decreased the bradykinin-induced unitary discharges of lamina V neuron of the spinal dorsal horn in intact rabbits but not in spinal rabbits. These results suggest that ID-1229 inhibits the sensory transmission of bradykinin-induced pain at the dorsal horn of the spinal cord, through its facilitatory action on the descending inhibitory system from the supra-spinal structure.