title: Increased sensitivity to dopamine agonists following a single dose of morphine or levorphanol in mice.
abstract: Acute administration of an opiate has been suggested to result in the development of supersensitive dopamine receptors. This hypothesis was tested in mice by determining the effect of a single administration of morphine or levorphanol on dopamine agonist-induced stereotypic behaviors and [3H]spiroperidol binding. Administration of morphine (1.0 mg/kg s.c.), which itself had no significant effect on spontaneous locomotor activity 3 h following administration, significantly potentiated locomotor activity induced by 1.5 or 4.5 mg/kg of apomorphine (i.p.) administered 3 h later. Morphine (10 mg/kg, s.c.) or levorphanol (0.2 and 2.0 mg/kg, s.c.), but not dextrorphan (up to 20 mg/kg, s.c.), enhanced climbing behavior induced by apomorphine (i.p.) or (-)-N-n-propylnorapomorphine (i.p.; NPA) administered 3 h later. An increase in whole brain and striatal [3H]spiroperidol binding sites was found 3 h after administration of 10 mg/kg of morphine. Concurrent administration of 5 mEq/kg of LiCl (i.p.) or 5 mg/kg of naloxone (i.p.; administered twice) attenuated both the potentiation of the climbing behavior induced by the two dopamine agonists and the increase in [3H]spiroperidol binding sites. These results suggest that a single administration of an opiate can induce the development of supersensitive dopamine receptors that is mediated by an interaction at opioid receptors.
mesh_terms: D000818:Animals; D001058:Apomorphine / Q000031:analogs & derivatives / Q000494:pharmacology*; D001921:Brain / Q000378:metabolism*; D001933:Brain Stem / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism; D002712:Chlorides / Q000494:pharmacology; D003342:Corpus Striatum / Q000378:metabolism; D003917:Dextrorphan / Q000494:pharmacology; D004357:Drug Synergism; D006624:Hippocampus / Q000378:metabolism; D007981:Levorphanol / Q000494:pharmacology; D008094:Lithium / Q000494:pharmacology; D018021:Lithium Chloride; D008297:Male; D051379:Mice; D009020:Morphine / Q000494:pharmacology; D009043:Motor Activity / Q000187:drug effects; D009270:Naloxone / Q000494:pharmacology; D009294:Narcotics / Q000494:pharmacology*; D011954:Receptors, Dopamine / Q000187:drug effects*; D013134:Spiperone / Q000378:metabolism
chemical_list: D002712:Chlorides; D009294:Narcotics; D011954:Receptors, Dopamine; D003917:Dextrorphan; D007981:Levorphanol; D009270:Naloxone; D013134:Spiperone; C009074:N-n-propylnorapomorphine; D009020:Morphine; D008094:Lithium; D018021:Lithium Chloride; D001058:Apomorphine