Suppression of analgesia in rats induced by morphine or L-NAME but not both drugs by microTesla, frequency-modulated magnetic fields.
In Experiment I, the nociceptive threshold for a criterion response to thermal stimuli (hot plate) for rats was obtained following injections with one of various dosages of either morphine or the nitric oxide synthase inhibitor, L-NAME. On the bases of these results, rats in Experiment II were injected with either morphine (4 mg/kg), L-NAME (50 mg/kg), both morphine and L-NAME, or saline after baseline measurements for nociception and then exposed to either a 1 microTesla magnetic field or to a sham field for 30 min. The magnetic field, presented once every 4 sec, was a frequency-modulated pattern whose pixel durations, for each of the 837 successive values, were 1 msec. Nociceptive thresholds were measured immediately after the exposure and 30 min later. The results indicated that exposure to this magnetic field abolished the analgesic effects of morphine or L-NAME when injected separately but not when injected together relative to rats that had received these drugs and had been exposed to the sham field.
Dixon
S J
SJ
Behavioral Neuroscience Laboratory, Laurentian University, Sudbury, Ontario P3E 2C6, Canada.
Persinger
M A
MA
D000698:Analgesia; D000701:Analgesics, Opioid / Q000494:pharmacology; D000818:Animals; D004791:Enzyme Inhibitors; D005260:Female; D006358:Hot Temperature; D008280:Magnetics; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology*; D010147:Pain Measurement; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time; D013997:Time Factors
D000701:Analgesics, Opioid; D004791:Enzyme Inhibitors; D009020:Morphine; D019331:NG-Nitroarginine Methyl Ester