Benzodiazepine system is involved in hyperalgesia in rats induced by the exposure to extremely low frequency magnetic fields.
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.
Jeong
Ji Hoon
JH
Department of Pharmacology, College of Pharmacy, Chung Ang University, Seoul 156-756, Korea.
Choi
Kyung Bum
KB
Moon
Nam Ju
NJ
Park
Eon Sub
ES
Sohn
Uy Dong
UD
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*
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