Naloxone excites nociceptive units in the lumbar dorsal horn of the spinal cat

Intravenous doses of 0.05–0.15 mg/kg of naloxone caused an increase in the spontaneous discharge rate of single dorsal horn units in lumbar spinal segments 5–7 in the spinal cat. This effect was seen with all of 21 units responding to noxious cutaneous stimulation. In contrast, the 7 units classified as non-nociceptive cutaneous were all unaffected by naloxone, even at doses of 0.4 mg/kg. Of two proprioceptive units, one was excited by …