Localization of ionotropic glutamate receptors in peripheral axons of human skin

Recent observations suggest that glutamate is important in sensory transduction in the periphery, contributing to peripheral sensitization of nociceptors and the hyperalgesia that accompanies inflammation. This study examined the presence of ionotropic glutamate receptors N-methyl-D-aspartate (NMDA), alpha-amino-3-hydroxy-5-methylisoxazolone-4-propionic acid (AMPA) and kainate (KA) in normal human hairy skin (n=6) using immunohistochemistry at the electron microscopic level. Analysis of labeled axons at the dermal-epidermal junction demonstrated that 26. 9+/-2, 19.5+/-3 and 18.5+/-1% of the axons analyzed were labeled for subunits of the NMDA, AMPA or KA receptors, respectively. An occasional Schwann cell process was labeled for either NMDA or KA receptors. The findings support the hypothesis that glutamate and its ionotropic receptors may play a role in the periphery in sensory processing in humans.