High intensity magnetic stimulation over the lumbosacral spine evokes antinociception in rats

• Published in: Clinical neurophysiology 2002-07, Vol.113 (7), p.1006-1012
• Main Authors: Lin, Vernon W.-H, Hsiao, Ian, Kingery, Wade S
• Format: Article
• Language: English
• Subjects: Adrenergic alpha-Antagonists - pharmacology; Analgesia; Animals; Biological and medical sciences; Electromagnetic Fields; Fundamental and applied biological sciences. Psychology; Hot Temperature; Imidazoles - pharmacology; Lumbosacral Region; Magnetic stimulation; Male; Naloxone - pharmacology; Narcotic Antagonists - pharmacology; Nerve Fibers; Opioid; Pain Measurement; Pain Threshold - drug effects; Pain Threshold - physiology; Physical Stimulation; Rats; Rats, Sprague-Dawley; Somesthesis and somesthetic pathways (proprioception, exteroception, nociception); interoception; electrolocation. Sensory receptors; Spinal cord; Spinal Nerves - physiology; Spine - physiology; Vertebrates: nervous system and sense organs
• ISSN: 1388-2457; 1872-8952
• DOI: 10.1016/S1388-2457(02)00122-0

Objectives: 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 α 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.