UI - 000082

AU - Lombard MC

AU - Besson JM

TI - Electrophysiological evidence for a tonic activity of the spinal cord intrinsic opioid systems in a chronic pain model

AB - The aim of this electrophysiological investigation was to evaluate the activity of the spinal endogenous

opioid systems in a chronic pain model, the arthritic rat. The activity of nociceptive non-specific dorsal horn

neurons (n = 23) were recorded in 23 spinal unanesthetized decerebrated rats. Naloxone (1 mg/kg i.v.)

induced a highly significant increase in the spontaneous firing rate of these neurons. This observation is in

favor of a tonic activity of spinal opioid endogenous systems in such a disease. In addition, the same dose of

naloxone facilitates the transmission of noxious messages at the spinal level as revealed by the large

enhancement of the responses of these neurons to C-fiber stimulation. These results are in good agreement

with behavioral data showing that such a relatively high dose of naloxone induced well-reproducible

hyperalgesia and with some biochemical observations showing an increase of levels and biosynthesis of

endogenous opioids in the spinal cord of the arthritic rat

SO - Brain Research 1989;477:48-5