Some membrane property changes following axotomy in A delta-type DRG cellsare related to cold allodynia in rat

NUMEROUS studies have suggested that changes in electrophysiological proper ties of primary sensory neurons after axonal injury contribute to the gener ation of neuropathic pain. Presently, however, it is unclear which of the c hanges is important. To address this issue, we performed behavioral and ele ctrophysiological experiments in a double-blind fashion; we made intracellu lar recordings in the St dorsal root ganglia excised from rats exhibiting : cold allodynia behavior after chronic S-1 spinal nerve transaction (allodyn ia-positive group) and om rats lacking such behavior after the same nerve i njury (allodynia-negative group) or sham injury (sham group). In this study , we sought which of the membrane property changes produced by the spinal n erve injury in each of C-, A delta- and A alpha/beta-cell populations was u nique to the allodynia-positive group. Analyses of our data revealed that o nly some changes in A delta-cells (e.g. the decrease in resting membrane po tential and in the threshold of central process) were more pronounced in or unique to the allodynia-positive group. We concluded that certain membrane property changes in the somata and dorsal root axons of AG-cells might be important in the generation of cold allodynia. NeuroReport 10:1493-1499 (C) 1999 Lippincott Williams & Wilkins.