Increased immunoreactive labeling of the spinal N-methyl-D-aspartate R1 receptors after dorsal root ganglionectomy in the rats

The N-methyl-D-aspartate (NMDA) receptor plays an important role in the dev elopment of the autotomy after dorsal root ganglionectomy (DRG n). In this study, we further investigated the expression of the NM DAR1 in the spinal cord of the rats after right DRGn by immunohistochemical analyses. Computer ized densitometric analysis of the NMDAR1 immunoreactivity was done and the integrated optical density (IOD) of the superficial laminae of the dorsal horn of the spinal cord was measured. The immunoreactive labeling of the NM DAR1 was increased in the cervical spinal cord ipsilateral to the DRGn from day 5 to 14 after DRGn. The ratio of the right/left IOD of the rats receiv ing DRGn was significantly higher than the rats in the sham-operated group and the control group IP ( 0.05). The expression of the NMDAR1 increased gr adually to reach the peak at day 7 after DRGn (mean right/left IOD ratio = 1.52), then decreased thereafter. The increased expression of the NMDAR1 at day 7 was suppressed by MK-801 (NMDA receptor antagonist) administered imm ediately after DRGn, but not by normal saline or 1,2,3,4-tetrahydro-6-nitro -2,3-dioxo-benzo[f] quinoxaline-7-sulfonamide (NBQX, non-NMDA receptor anta gonist). The results indicated that the expression of the NMDAR1 in the sup erficial laminae of the dorsal horn of the spinal cord was increased after DRGn and the time course was compatible with the onset and development of t he autotomy induced by DRGn. (C) 2000 Elsevier Science Ireland Ltd. All rig hts reserved.