Extremely low frequency magnetic field induces hyperalgesia in mice modulated by nitric oxide synthesis.
We investigated an effect of extremely low frequency magnetic field (ELF-MF, 60 Hz) on hyperalgesia using hot plate test. The level of nitric oxide (NO) and the expression of nitric oxide synthase (NOS) were measured to determine if ELF-MF is engaged in NO mediated pain mechanism. Additionally, the involvement of Ca2+-dependent NO pathway in ELF-MF induced hyperalgesia was evaluated by blocking Ca2+ sources with NMDA receptor antagonist and Ca2+ channel blocker. The exposure of mice to ELF-MF lowered pain threshold and elevated NO synthesis in brain and spinal cord. An NOS inhibitor blocked these effects of ELF-MF with attenuating the reduction of pain threshold and the rise of NO level in brain and spine by the exposure of ELF-MF. The hyperalgesic effects of ELF-MF were also blocked by a Ca2+ channel blocker, nimodipine, but not by a NMDA receptor antagonist, MK-801. The expression of Ca2+ -dependent nNOS and eNOS and Ca2+ -independent iNOS were not changed by ELF-MF. These results indicated that the exposure of ELF-MF might cause Ca2+ -dependent NOS activation, which then induces hyperalgesia with the increase in NO synthesis. In conclusion, ELF-MF may produce hyperalgesia by modulating NO synthesis via Ca2+ -dependent NOS.
Jeong
Ji Hoon
JH
Department of Pharmacology, School of Medicine, Chung-Ang University, Seoul 156-756, Republic of Korea.
Kum
Chan
C
Choi
Hee Jung
HJ
Park
Eon Sub
ES
Sohn
Uy Dong
UD
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000502:physiology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D004195:Disease Models, Animal; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004574:Electromagnetic Fields / Q000009:adverse effects*; D006358:Hot Temperature; D006930:Hyperalgesia / Q000209:etiology*; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology
D002121:Calcium Channel Blockers; D009569:Nitric Oxide; D016291:Dizocilpine Maleate; D019001:Nitric Oxide Synthase