title: High doses of L-naloxone but neither D-naloxone nor beta-funaltrexamine prevent hyperthermia-induced seizures in rat pups.
abstract: The effects of the non-specific opiate antagonist L-naloxone and the inactive isomer D-naloxone, as well as the specific mu receptor antagonist beta-funaltrexamine, have been examined on hyperthermia-induced seizures in unrestrained 15 days old rats. Saline-injected animals exposed to an ambient temperature of 40 degrees C showed a gradual increase in body temperature reaching a maximum of 42 +/- 0.1 degrees C at 50 min exposure. At this time all the pups had seizures and died. Similar results were obtained when the animals were pretreated with different doses of D-naloxone and beta-funaltrexamine. Rats pretreated with L-naloxone also showed an increase in rectal temperature; but the temperature was lower than in saline-injected animals. Only high doses of L-naloxone prevented seizures and deaths. These data indicate that endogenous opioid peptides may play a role in seizures induced by hyperthermia and that receptors other than mu receptors could be involved in hyperthermia-induced seizures.
mesh_terms: D000818:Animals; D001831:Body Temperature / Q000187:drug effects; D006979:Hyperthermia, Induced; D009270:Naloxone / Q000494:pharmacology*; D009271:Naltrexone / Q000031:analogs & derivatives* / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012640:Seizures / Q000209:etiology / Q000517:prevention & control*; D013237:Stereoisomerism
chemical_list: D009292:Narcotic Antagonists; D009270:Naloxone; D009271:Naltrexone; C024524:beta-funaltrexamine