Analgesic effect of vitamin E in neuropathic pain

[Guest guest]

Pain. 2006 Mar 6

Analgesic effect of vitamin E is mediated by reducing central

sensitization in neuropathic pain.

Kim HK, Kim JH, Gao X, Zhou JL, Lee I, Chung K, Chung JM.

Department of Neuroscience and Cell Biology, University of Texas

Medical Branch, Galveston, TX 77555-1069, USA.

Recent studies suggest that reactive oxygen species (ROS) are

critically involved in neuropathic pain. Although vitamin E is a well-

known antioxidant, its efficacy on chronic pain is not known. This

study investigated the efficacy and mechanisms of vitamin E analgesia

in a rat model of neuropathic pain produced by spinal nerve ligation.

The effects of vitamin E were investigated using behavioral testing,

electrophysiological recording of dorsal horn neurons, and

determinations of phosphorylated NMDA receptor subunit 1 (pNR1)

levels in the spinal dorsal horn. Results showed that a systemic

single injection of a high dose or repetitive daily injections of low

doses of vitamin E significantly reduced neuropathic pain behaviors.

Vitamin E was also effective in producing analgesia by intrathecal

injection, suggesting the importance of spinal mechanisms. In spinal

dorsal horn neurons, vitamin E reduced evoked responses to mechanical

stimuli as well as the sizes of their receptive fields. In addition,

levels of pNR1 in neuropathic rats were also reduced by vitamin E

injection. These data suggest that vitamin E produces analgesia in

neuropathic rats that is, at least in part, mediated by reducing

central sensitization which, in turn, is induced by peripheral nerve

injury.