title: Rewarding effects of ethanol combined with low doses of morphine through dopamine D1 receptors.
abstract: This study investigated whether ethanol combined with low doses of morphine produces rewarding effects in rats. Ethanol (0.075-1.2 g/kg, intraperitoneal [i.p.]) alone did not induce place preference. A moderate dose (1 mg/kg, s.c.), but not a low dose (0.1 mg/kg), of morphine induced a significant place preference. The combination of ethanol (0.075-0.6 g/kg, i.p.) and 0.1 mg/kg of morphine, as well as low doses of morphine (0.03-0.1 mg/kg, subcutaneous [s.c.]) combined with ethanol (0.3 g/kg, i.p.), induced a significant place preference. The combined effect of ethanol and morphine was significantly attenuated by naloxone (0.3 mg/kg, s.c.), naltrindole (1.0 mg/kg, s.c.), or long-term administration of the dopamine D1 receptor antagonist SCH23390 (1.0 mg/kg/day, s.c.). These results suggest that the rewarding effect induced by ethanol and a low dose of morphine is mediated by activation of the central opioidergic and dopaminergic systems through dopamine D1 receptors.
authors.affiliation: Section of Pharmaceutical Services, Nippon Medical School Hospital, Nippon Medical School, Tokyo, Japan.
authors.forename: Yuya
authors.initials: Y
authors.lastname: Ise
authors.forename: Tomohisa
authors.initials: T
authors.lastname: Mori
authors.forename: Shirou
authors.initials: S
authors.lastname: Katayama
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nagase
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Suzuki
mesh_terms: D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D001552:Benzazepines / Q000008:administration & dosage / Q000494:pharmacology; D002492:Central Nervous System Depressants / Q000008:administration & dosage / Q000494:pharmacology; D003213:Conditioning, Psychological / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D000431:Ethanol / Q000008:administration & dosage / Q000494:pharmacology*; D007274:Injections, Intraperitoneal; D007279:Injections, Subcutaneous; D008297:Male; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D009270:Naloxone / Q000008:administration & dosage / Q000494:pharmacology; D009271:Naltrexone / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000008:administration & dosage / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017447:Receptors, Dopamine D1 / Q000037:antagonists & inhibitors / Q000502:physiology*; D012201:Reward
chemical_list: D000701:Analgesics, Opioid; D001552:Benzazepines; D002492:Central Nervous System Depressants; D009292:Narcotic Antagonists; D017447:Receptors, Dopamine D1; C534628:SCH 23390; D009270:Naloxone; D000431:Ethanol; D009271:Naltrexone; D009020:Morphine; C055382:naltrindole