title: Benzodiazepine system is involved in hyperalgesia in rats induced by the exposure to extremely low frequency magnetic fields.
abstract: Many reports demonstrate that extremely low frequency magnetic fields (ELF MFs, 60 Hz) may be involved in hyperalgesia. In a previous investigation, we suggested that MFs may produce hyperalgesia and such a response may be regulated by the benzodiazepine system. In order to further confirm this effect of MFs, we used diazepam and/or flumazenil with MFs exposure. When testing the pain threshold of rats using hot plate tests, MFs or diazepam (0.5 microg, i.c.v.; a benzodiazepine receptor agonist) induced hyperalgesic effects with the reduction of latency. These effects were blocked by a pretreatment of flumazenil (1.5 mg/kg, i.p.; a benzodiazepine receptor antagonist). When the rats were exposed simultaneously to MFs and diazepam, the latency tended to decrease without statistical significance. The induction of hyperalgesia by co-exposure to MFs and diazepam was also blocked by flumazenil. However, the pretreatment of GABA receptor antagonists such as bicuculline (0.1 microg, i.c.v.; a GABA(A) antagonist) or phaclofen (10 microg, i.c.v.; a GABA(B) antagonist) did not antagonize the hyperalgesic effect of MFs. These results suggest that the benzodiazepine system may be involved in MFs-induced hyperalgesia.
authors.affiliation: Department of Pharmacology, College of Pharmacy, Chung Ang University, Seoul 156-756, Korea.
authors.forename: Ji Hoon
authors.initials: JH
authors.lastname: Jeong
authors.forename: Kyung Bum
authors.initials: KB
authors.lastname: Choi
authors.forename: Nam Ju
authors.initials: NJ
authors.lastname: Moon
authors.forename: Eon Sub
authors.initials: ES
authors.lastname: Park
authors.forename: Uy Dong
authors.initials: UD
authors.lastname: Sohn
mesh_terms: D000818:Animals; D014151:Anti-Anxiety Agents / Q000008:administration & dosage / Q000494:pharmacology; D001418:Baclofen / Q000031:analogs & derivatives* / Q000494:pharmacology; D001640:Bicuculline / Q000494:pharmacology; D003975:Diazepam / Q000008:administration & dosage / Q000494:pharmacology; D004574:Electromagnetic Fields / Q000009:adverse effects*; D005442:Flumazenil / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D018757:GABA Modulators / Q000494:pharmacology; D058787:GABA-A Receptor Antagonists; D058788:GABA-B Receptor Antagonists; D006358:Hot Temperature; D006930:Hyperalgesia / Q000503:physiopathology*; D007276:Injections, Intraventricular; D008297:Male; D010147:Pain Measurement / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000187:drug effects; D011963:Receptors, GABA-A / Q000502:physiology*
chemical_list: D014151:Anti-Anxiety Agents; D018756:GABA Antagonists; D018757:GABA Modulators; D058787:GABA-A Receptor Antagonists; D058788:GABA-B Receptor Antagonists; D011963:Receptors, GABA-A; C052329:phaclofen; D005442:Flumazenil; D001418:Baclofen; D003975:Diazepam; D001640:Bicuculline