Nmda and Ampa/Ka Receptors Are Involved in the C-Fos Expression Following Mustard Oil Activation of C-Fibres

Abstract

To examine whether mustard oil application to the skin activated c-Fos via glutamate receptors, a competitive NMDA receptor antagonist, 3-(2-carboxpiperazin-4-yl)propyl-l-phospionic acid (CPP), a selective AMPA/KA receptor antagonist, 6-cyano-2,3-dihydroxy-7-nitroquinoxaline (CNQX), or both, were used intrathecally 10 min prior to noxious stimulation. Application of mustard oil to left hind foot of the vehicle-injected animals produced c-Fos expression mainly in superficial laminae (laminae I-II) of the dorsal horn on the side ipsilateral to the stimulation. CPP significantly reduced the number of c-Fos-positive nuclei in superficial laminae. But significant reduction of c-Fos expression by CNQX was seen in deeper laminae (laminae III-X). Administration of both CPP and CNQX extensively reduced the number of c-Fos-positive cells in both superficial and deeper laminae. However, they did not greatly change the number of c-Fos-positive cells in lamina I. This experiment revealed that NMDA and AMPA/KA receptors contribute to the mustard oil-induced c-Fos expression in the spinal cord. These data also suggest that other neurotransmitter receptors might be involved in the activation produced by algesic chemical activation of C-fibre primary afferents. (C) 2004 Elsevier B.V. All rights reserved.