Magnesium suppresses neuropathic pain responses in rats via a spinal site of action.
We tested the ability of Mg2+ therapy to block the heat-hyperalgesia, mechano-allodynia and mechano-hyperalgesia that are seen in rats with an experimental painful peripheral neuropathy (the CCI model of Bennett and Xie). Systemic Mg2+ (magnesium sulfate, 600 mg/kg, s.c.) significantly reduced heat-hyperalgesia and mechano-allodynia for 2-24 h post-injection, but had no effect on mechano-hyperalgesia. Intrathecal (i.t.) injections of Mg2+ (185-750 micrograms) at the level of the lumbar spinal cord significantly reduced heat-hyperalgesia, but perineural application (750 and 7,000 micrograms) to the site of nerve injury had no effect. Neither s.c. nor i.t. Mg2+ had any effect on the responses from the control, sham-operated side. We conclude that Mg2+ has a spinal site of action. Mg2+ therapy may be of limited use in the treatment of human painful peripheral neuropathy.
Xiao
W H
WH
Neurobiology and Anesthesiology Branch, National Institute of Dental Research, National Institutes of Health, Bethesda, MD 20892-4410.
Bennett
G J
GJ
D000818:Animals; D006358:Hot Temperature; D006930:Hyperalgesia / Q000209:etiology / Q000503:physiopathology; D007278:Injections, Spinal; D007279:Injections, Subcutaneous; D008274:Magnesium / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D010146:Pain / Q000503:physiopathology; D010523:Peripheral Nervous System Diseases / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012678:Sensation Disorders / Q000503:physiopathology; D013116:Spinal Cord / Q000187:drug effects / Q000503:physiopathology*
D008274:Magnesium