High intensity magnetic stimulation over the lumbosacral spine evokes antinociception in rats.
OBJECTIVE
High intensity magnetic stimulation (MS) applied over the skin can painlessly depolarize superficial and deep nerves and we aimed to evaluate the effectiveness of MS of spinal nerves in evoking a potent analgesic response.


METHODS
The MS was administered to adult male Sprague-Dawley rats using a Cadwell MES-10 high-speed magnetic stimulator. A Peltier device and von Frey fibers were used to determine heat and mechanical nociceptive responses of the rats.


RESULTS
A brief (5 min) course of MS over the rat's lumbosacral spine produced a long-lasting (30-40 min) and robust (80-90% maximum possible effect) hindpaw antinociceptive effect to both mechanical and heat stimuli. Spinal cord transected rats had intact hindpaw nociceptive withdrawal responses, but transection eliminated MS evoked antinociception, indicating a critical extrasegmental component in the mechanism of MS antinociceptive action. The opiate receptor antagonist naloxone (5 mg/kg, i.p.) completely blocked MS evoked antinociception, demonstrating an opioidergic mechanism for MS antinociception. The alpha(2) adrenoceptor antagonist atipamezole (5 mg/kg, i.p.) slightly reduced the MS antinociceptive response to heat and had no effect on MS antinociception for mechanical stimuli.


CONCLUSIONS
These data indicate that MS can evoke a robust, long-lasting antinociceptive effect, which requires an intact supraspinal pathway and is opioidergic mediated.
Lin
Vernon W-H
VW
Functional Magnetic Stimulation Laboratory, Spinal Cord Injury/Disorder, Health Care Group, VA Long Beach Health Care System, CA 90822, USA. vernon.lin@med.va.gov
Hsiao
Ian
I
Kingery
Wade S
WS
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000698:Analgesia; D000818:Animals; D004574:Electromagnetic Fields; D006358:Hot Temperature; D007093:Imidazoles / Q000494:pharmacology; D008161:Lumbosacral Region; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009412:Nerve Fibers; D010147:Pain Measurement; D017288:Pain Threshold / Q000187:drug effects / Q000502:physiology; D010812:Physical Stimulation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013127:Spinal Nerves / Q000502:physiology; D013131:Spine / Q000502:physiology*
D000317:Adrenergic alpha-Antagonists; D007093:Imidazoles; D009292:Narcotic Antagonists; C050701:atipamezole; D009270:Naloxone