N-methyl-D-aspartate (NMDA) and non-NMDA glutamate receptor antagonists differentially suppress dorsal horn neuron responses to mechanical stimuli in rats with peripheral nerve injury

Abstract

The effects of iontophoretically ejected glutamate receptor antagonists on mechanically evoked responsiveness were examined on wide dynamic range (WDR) dorsal horn neurons in anesthetized rats that received a unilateral ligation of the L5 and L6 spinal nerves 10-15 days previously. Both brush- and pinch-evoked responses of dorsal horn neurons on the nerve-injured side were enhanced. N-Methyl-D-aspartate (NMDA) receptor antagonist, 2-amino-5-phosphonopentanoic acid (AP5), preferentially suppressed the enhanced pinch-evoked response, whereas (RS)-a-amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA) receptor selective antagonist, 6-nitro-7-sulphamoylbenzo(f)quinoxaline-2,3-dione (NBQX), preferentially attenuated the enhanced brush-evoked response. The results indicate that the enhanced responses to noxious and non-noxious peripheral inputs induced in WDR dorsal horn neurons following the nerve injury are mediated by activation of NMDA and AMPA receptors, respectively.