• Ming Jiang, Wei Zhang, Chongxue Cheng, Zhengliang Ma, and Xiaoping Gu.
• Department of Anesthesiology, Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing 210008, Jiangsu Province, PR China.
• Pharmacol. Biochem. Behav. 2015 Jul 1; 134: 35-41.

AimsRemifentanil is a short-acting and highly selective mu opiate agonist that is used in many clinical surgical situations for intraoperative pain relief. Under certain conditions, remifentanil can produce "paradoxical" hyperalgesia. This study aims to investigate mechanisms of actions mediating this "paradoxical" effect.MethodsSprague-Dawley rats were divided into 6 groups including control and treatment groups. The paw withdrawal mechanical threshold and the paw withdrawal thermal latency of the rats were tested. The changes of rat behaviors were measured at 24h before intrathecal injection and at 2h, 6h, 24h, and 48h after operation. According to the changes in behavioral indicators of pain, the specimens of all groups were collected at 2h, 6h, 24h, and 48h after the operation. The level of calcium/calmodulin-dependent protein kinase II (CaMKII) phosphorylation in the spinal dorsal horn was analyzed by Western blotting.ResultsIntraoperative infusion of remifentanil induced postoperative hyperalgesia in the rats. Intrathecal KN93 injection increased nociceptive thresholds of paw withdrawal mechanical threshold and paw withdrawal thermal latency in a dose-dependent manner. Western blotting results showed that CaMKII phosphorylation in the spinal dorsal horn was increased significantly by remifentanil. Inhibition of CaMKII phosphorylation relieved the hyperalgesia pain state.ConclusionsIntrathecal injection of KN93 attenuates postoperative hyperalgesia induced by intraoperative infusion of remifentanil in rats through inhibiting spinal CaMKII phosphorylation.Copyright © 2015. Published by Elsevier Inc.

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