[The effect of microinjections of morphine and tramadol into the locus coeruleus on the nociceptive responses of the spinal cord neurons and on shifts in the arterial pressure].

Morphine and tramadol produces selective inhibition of the spinal noxious-evoked activity, but does not change blood pressure reactions. Antinociception was reversed by this structure injection of the naloxone. These data suggest that locus coeruleus realized the pain-relief effect of the opiate drugs.