Specific contribution of lumbar spinal mechanisms to persistent nociceptive responses in the formalin test.
To determine whether a lumbar spinal mechanism mediates the late phase of the nociceptive response in the formalin test, we compared the effects of intrathecal (i.t.) lidocaine given pre- or post-formalin at the lumbar or thoracic level. Pre- but not post-formalin administration of lidocaine to the lumbar level significantly attenuated late phase nociceptive responses. In contrast, neither pre- nor post-formalin administration of lidocaine to the mid-thoracic level altered nociceptive responses. In rats chronically spinalized at the mid-thoracic level, nociceptive responses to formalin were observed which were blocked by i.t. pre-treatment with lidocaine at the lumbar level. These results suggest that a specific lumbar spinal mechanism is involved in the initiation of persistent nociception in the formalin test.
Coderre
T J
TJ
Pain Mechanisms Laboratory, Clinical Research Institute of Montreal, Quebec, Canada.
Yashpal
K
K
Henry
J L
JL
D000775:Anesthesia, Spinal; D000818:Animals; D003655:Decerebrate State / Q000503:physiopathology*; D005557:Formaldehyde; D008012:Lidocaine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D008161:Lumbosacral Region; D008297:Male; D009619:Nociceptors / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000502:physiology*
D005557:Formaldehyde; D008012:Lidocaine