Selective inhibition of nociceptive flexion reflex discharge by the kappa agonist bremazocine.

ABSTRACT

In unanaesthetized decerebrate spinal cats, bremazocine (0.012-0.2 mg/kg, i.v.) selectively inhibited the late C-fibre reflex discharge, recorded in sectioned lumbo-sacral ventral root filaments, after supramaximal electrical stimulation of the ipsilateral sural or common peroneal nerve. This action was naloxone-reversible. The results suggest that activation of kappa opioid receptors in the spinal cord inhibits the integration of nociceptive, but not locomotor, flexion reflexes.