title: Effect of light/dark cycle alteration on morphine-induced conditioned place preference.
abstract: The influence of acute and chronic light/dark cycle alteration on morphine-induced conditioned place preference was evaluated in mice. In chronic experiments, morphine (1-10 and 2.5-10 mg/kg) induced conditioned place preference in animals maintained on 12/12 and 6/18 light/dark cycles, respectively. In mice maintained on 18/6 light/dark cycle, however, morphine produced conditioned place preference only by the dose of 10 mg/kg. This latter effect was abolished by chronic daily administration of melatonin (10, 20 mg/kg). Moreover, our data showed that both abrupt increase and decrease in photoperiod on the day before testing reduced the ability of morphine to produce place conditioning. A single melatonin (10 mg/kg) injection reversed the attenuating effect of a 6-h delay in the dark cycle on morphine conditioned place preference.
authors.affiliation: Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran. dehpour@medscape.com
authors.forename: Pouya
authors.initials: P
authors.lastname: Tahsili-Fahadan
authors.forename: Noushin
authors.initials: N
authors.lastname: Yahyavi-Firouz-Abadi
authors.forename: Mohammad Hossein
authors.initials: MH
authors.lastname: Ghahremani
authors.forename: Ahmad Reza
authors.initials: AR
authors.lastname: Dehpour
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D002940:Circadian Rhythm / Q000187:drug effects / Q000502:physiology*; D003216:Conditioning, Operant / Q000187:drug effects / Q000502:physiology*; D003624:Darkness; D008027:Light; D008297:Male; D008550:Melatonin / Q000494:pharmacology; D051379:Mice; D009020:Morphine / Q000494:pharmacology*; D009294:Narcotics / Q000494:pharmacology*; D017440:Photoperiod; D012201:Reward
chemical_list: D000975:Antioxidants; D009294:Narcotics; D009020:Morphine; D008550:Melatonin