title: Repeated naloxone treatments and exposures to weak 60-Hz magnetic fields have 'analgesic' effects in snails.
abstract: Results of studies with rodents have shown that animals repeatedly injected with the opioid antagonist, naloxone, acquire a hypoalgesic response to thermal nociceptive stimuli. The present study revealed a similar response in the terrestrial pulmonate snail, Cepaea nemoralis. Snails receiving daily injections of naloxone followed by measurements of thermal nociceptive sensitivity also developed hypoalgesia. Daily brief (30-min) exposures to a weak 60-Hz magnetic field (1.0 gauss or 0.1 mT), which acutely antagonize opioid-mediated nociception and antinociception in a manner comparable to that of naloxone, also led to the expression of a hypoalgesic responses. This suggests that opioid antagonist-induced thermal hypoalgesia may be a basic feature of opioid systems. This naloxone- and magnetic field-induced 'analgesia' is consistent with either a facilitation of aversive thermal conditioning and or antagonism of the excitatory, hyperalgesic effects of low levels of endogenous opioids.
authors.affiliation: Bioelectromagnetics Western and Neuroscience Program, University of Western Ontario, London, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Kavaliers
authors.forename: K P
authors.initials: KP
authors.lastname: Ossenkopp
mesh_terms: D000698:Analgesia; D000818:Animals; D004558:Electric Stimulation; D004574:Electromagnetic Fields; D006358:Hot Temperature; D009270:Naloxone / Q000008:administration & dosage* / Q000494:pharmacology; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology; D011930:Reaction Time; D012908:Snails / Q000502:physiology*
chemical_list: D009270:Naloxone