MK-801 reduces non-noxious stimulus-evoked Fos-like immunoreactivity in the spinal cord of rats with chronic constriction nerve injury

We investigated the role of N-methyl-D-aspartate (NMDA) receptors on non-no xious stimulus-induced pain by examining the effect of MK-801, a non-compet itive NMDA receptor antagonist, on Fos-like immunoreactivity (FLI) in the s pinal dorsal horn by non-noxious stimulation to rats with chronic constrict ion injury (CCI) of the sciatic nerve. In CCI rats that did not receive the non-noxious stimulus, FLI was significantly increased in laminae V/VI of t he dorsal horn at the 7th and 14th days after surgery relative to sham rats . When CCI rats received non-noxious stimuli, rubbing the plantar of the hi nd paw, FLI in laminae I/II at the 14th day was significantly increased rel ative to CCI rats that did not receive the stimulation. In sham rats, the s ame stimulus significantly decreased FLI in laminae III/IV and V/VI at the 7th and 14th day. When MK-801 was administered intraperitoneally prior to n on-noxious stimulation in CCI rats at the 14th day after surgery, the stimu lus-induced FLI in laminae I/II in CCI rats was significantly reduced. This study indicates that NMDA receptor is involved in upregulating FLI in resp onse to non-noxious stimulation of CCI rats. (C) 2001 Elsevier Science B.V. All rights reserved.