The effect of sodium channel blocker, mexiletine, on spinal cord nociceptive transmission in monoarthritic rats

The purpose of this study was to investigate the analgesic effect of mexiletine on the deep dorsal horn neuron of spinal cord in monoarthritic rats. Twently-four Sprague-Dawley rats (250 similar to 300 g., male) were received CFA 0.05 ml into the left ankle joint for induction of monoarthritis. Group A received mexiletine 20 mg/kg administration and group B received meloxicam 4 mg/kg administration daily for 2 weeks with orogastric tube. We checked joint circumference and neurobehavioral analysis for the mechanical allodynia and thermal hyperalgesia at 2(nd), 5(th), and 14(th) day after each drug administration. Electrophysiologic study was performed at 14th day by direct nerve recording method. The joint circumference was significantly decreased in group B. and the threshold of mechanical allodynia were increased in both group, but not significant. The mean impulses were significant decreased in both group compared with control group.