Pharmacological analysis of inhomogeneous static magnetic field-induced antinociceptive action in the mouse.
The effect of inhomogeneous, 2-754 mT static magnetic field (SMF) on visceral pain elicited by intraperitoneal injection of 0.6% acetic acid (writhing test) was studied in the mouse. Exposure of mice to static magnetic field (permanent NdFeB N50 grade 10 mm x 10 mm cylindrical magnets with alternating poles) during the nociceptive stimulus (0-30 min) resulted in inhibition of pain reaction: the number of writhings decreased from 9 +/- 2, 32 +/- 4 and 30 +/- 3 to 2 +/- 0.03, 15 +/- 1.6, and 14 +/- 1.6, respectively, measured in 0-5th, 6-20th, and 21-30th min following the acetic acid challenge. The pain reaction during the total observation period was reduced by 57% (P < 0.005). The analgesic action induced by SMF was inhibited by subcutaneous administration of naloxone (1 and 0.2 mg kg(-1)), irreversible micro-opioid receptor antagonist beta-funaltrexamine (20 mg kg(-1)) and delta-opioid receptor antagonist naltrindole (0.5 mg kg(-1)), but the kappa-opioid receptor antagonist norbinaltorphimine (20 mg kg(-1)) failed to affect the SMF-induced antinociception. In contrast to the subcutaneous administration, the intracerebroventricularly injected naloxone (10 microg mouse(-1)) did not antagonize the antinociceptive effect of SMF. The results suggest that acute exposure of mice to static magnetic field results in an opioid-mediated analgesic action in the writhing test in the mouse. The antinociceptive effect is likely to be mediated by micro and (to a lesser extent) delta-opioid receptors.
Gyires
Klára
K
Faculty of Medicine, Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary. gyirkla@pharma.sote.hu
Zádori
Zoltán S
ZS
Rácz
Bernadette
B
László
János
J
D019342:Acetic Acid; D000818:Animals; D016880:Anisotropy; D004558:Electric Stimulation / Q000379:methods*; D004574:Electromagnetic Fields; D008297:Male; D051379:Mice; D010146:Pain / Q000139:chemically induced* / Q000503:physiopathology* / Q000517:prevention & control; D017288:Pain Threshold / Q000187:drug effects* / Q000528:radiation effects*
D019342:Acetic Acid