Calcium channel involvement in magnetic field inhibition of morphine-induced analgesia.
An exposure for 60 min to a weak 0.5 Hz rotating magnetic field significantly reduced the day-time analgesic effects of morphine in male mice. The dihydropyridine (DHP) calcium channel antagonists diltiazem and nifedipine and the non-DHP antagonist verapamil, as well as the inorganic calcium channel blockers, La3+ and Co2+, differentially reduced, while the DHP calcium channel agonist, BAY K 8644, enhanced the inhibitory effects of the magnetic stimuli. In a similar manner, though to a lesser degree, the calcium channel antagonists and agonist, increased and decreased, respectively, the inhibitory effects of intracerebroventricular administrations of Ca2+ on morphine-induced analgesia. The calcium channel antagonists and agonists had no significant effects on naloxone-mediated reductions of morphine-induced analgesia. These results suggest that exposure to magnetic stimuli affects the functioning of calcium channels and the distribution of calcium ions, thereby, altering the effects of opiates.
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D007473:Ion Channels / Q000502:physiology*; D008280:Magnetics; D051379:Mice; D009020:Morphine / Q000494:pharmacology*; D010146:Pain / Q000503:physiopathology*
D002120:Calcium Channel Agonists; D002121:Calcium Channel Blockers; D007473:Ion Channels; D009020:Morphine; D002118:Calcium