title: Behavioral evidence for an opiate pituitary mechanism subserving conditioned analgesia.
abstract: The effect of a naloxone or a dexamethasone pretreatment on the conditioned analgesia resulting from the exposure of rats to an experimental chamber repeatedly paired with a grid shock was investigated. Shock induced disruption of bar pressing activity was taken as a behavioral measure of pain responsiveness. It was found that a 6, but not a 3, mg/kg dose of naloxone i.p. is hyperalgesic in unconditioned rats and effectively antagonizes conditioned analgesia. Dexamethasone (up to a dose of 2 + 1 mg/kg i.p. 23 and 1 h prior) did not alter the pain responsiveness of unconditioned rats, but caused a dose dependent suppression of conditioned analgesia. These results are discussed in terms of an opiate pituitary mechanism subserving conditioned analgesia.
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000502:physiology; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D003216:Conditioning, Operant / Q000502:physiology*; D003907:Dexamethasone / Q000494:pharmacology; D004597:Electroshock; D004723:Endorphins / Q000502:physiology; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology*; D010902:Pituitary Gland / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000187:drug effects / Q000502:physiology*
chemical_list: D004723:Endorphins; D011957:Receptors, Opioid; D009270:Naloxone; D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone