• Min Dai, Toshinobu Sumida, Megumi Tagami, Yasuo Ide, Masaki Nagase, Hiroshi Sekiyama, and Kazuo Hanaoka.
• Department of Anesthesiology and Pain Relief Center, The University of Tokyo, 7-3-1 Hongo, Bunkyou-ku, Tokyo 113-8655, Japan.
• J Anesth. 2002 Jan 1; 16 (3): 211-5.

PurposeThe purpose of this study was to assess the effect of local spinal cord cooling on spinal dorsal-horn neuronal activity, with special emphasis on the role of endogenous opioid.MethodsDecerebrate, spinal-cord-transected cats ( n= 30) were subjected to local spinal-cord irrigation, using 0.9 N saline solution (15 degrees C; n= 15, and 35 degrees C; n= 15) for 90 min. The extracellular, single-cell activity of spinal dorsal-horn neurons responding to noxious stimulation was recorded. Sixty-one minutes after induction of local spinal-cord irrigation, naloxone (0.1 mg.kg(-1)) was administered intravenously. Local spinal-cord blood flow was measured using the hydrogen clearance technique.ResultsLocal spinal cord cooling produced significant suppression of both spontaneous and evoked activity (33.1 +/- 7.7% and 31.4 +/- 5.5%, respectively; mean +/- SE). Naloxone reversed this suppression immediately. Local spinal-cord blood flow was significantly reduced during spinal-cord cooling, but naloxone did not change local spinal-cord blood flow.ConclusionThe results demonstrate that endogenous opioids may play an important role in dorsal-horn neuronal suppression induced by local spinal-cord cooling.

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