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 μ-opioid receptor antagonist β-funaltrexamine (20 mg kg-1) and δ-opioid receptor antagonist naltrindole (0.5 mg kg-1), but the κ-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 μg 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 μ and (to a lesser extent) δ-opioid receptors.
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging