Effects of ethosuximide, a T-type Ca2+ channel blocker, on dorsal horn neuronal responses in rats

Plasticity in transmission and modulatory systems are implicated in mechani sms of neuropathic pain. Studies demonstrate the importance of high voltage -activated Ca2+ channels in pain transmission, but the role of low voltage- activated, T-type Ca2+ channels in nociception has not been investigated. T he Kim and Chung rodent model of neuropathy [Pain 50 (1992) 355] was used t o induce mechanical and cold allodynia in the ipsilateral hindpaw. In vivo electrophysiological techniques were used to record the response of dorsal horn neurones to innocuous and noxious electrical and natural (mechanical a nd thermal) stimuli after spinal nerve ligation. Spinal ethosuximide (5-105 5 mug) exerted dose-related inhibitions of both the electrically and low- a nd high-intensity mechanical and thermal evoked neuronal responses and its profile remained unaltered after neuropathy. Measures of spinal cord hypere xcitability were most susceptible to ethosuximide. This study, for the firs t time, indicates a possible role for low voltage-activated Ca2+ channels i n sensory transmission. (C) 2001 Elsevier Science B.V. All rights reserved.