title: A comparison between spontaneous electroencephalographic activities induced by morphine and morphine-related environment in rats.
abstract: Previous studies demonstrated that drug cues could elicit drug-like or withdrawal-like effect, both subjectively and physiologically. However, few studies have compared the central activities induced by a drug-related environment and the drug itself. The aim of this study was to observe and compare electroencephalographic (EEG) changes induced by acute morphine administration and by the morphine-related environment. EEG activities were recorded via twelve skull electrodes scattered on the left and right cortex in conscious, freely moving rats, either after acute morphine administration or after successful training of conditioned place preference. Acute administration of morphine (0.1, 0.5, 1, 5, 10, 20 mg/kg, i.p.) produced an increase in absolute EEG power in the delta, theta, alpha1, alpha2, beta1, and beta2 bands, as well as a decrease in the gamma band. Topographic mapping revealed a maximal increase in the lateral leads in the theta band and a maximal change in the centro-frontal region in the remaining bands. After place conditioning training, the morphine-related environment induced a diffuse decrease in absolute power in the delta, theta, alpha1, alpha2, beta1, and beta2 bands, which was opposite to the changes induced by acute morphine administration. In addition, the changes in relative power induced by the two situations also diverged. These results indicate that the central mechanisms underlying the motivation of morphine-induced place preference may be somehow different from those underlying the reward effects produced by acute morphine administration.
authors.affiliation: Neuroscience Research Institute, Peking University, Health Science Center, 38 Xueyuan Road, Haidian District, Beijing 10083, P.R. China.
authors.forename: Yan-Fang
authors.initials: YF
authors.lastname: Zuo
authors.forename: Jin-Yan
authors.initials: JY
authors.lastname: Wang
authors.forename: Ji-Huan
authors.initials: JH
authors.lastname: Chen
authors.forename: Zhi-Mei
authors.initials: ZM
authors.lastname: Qiao
authors.forename: Ji-Sheng
authors.initials: JS
authors.lastname: Han
authors.forename: Cai-Lian
authors.initials: CL
authors.lastname: Cui
authors.forename: Fei
authors.initials: F
authors.lastname: Luo
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000187:drug effects / Q000502:physiology; D003216:Conditioning, Operant / Q000187:drug effects*; D003463:Cues; D004305:Dose-Response Relationship, Drug; D004569:Electroencephalography / Q000187:drug effects*; D008297:Male; D009020:Morphine / Q000008:administration & dosage*; D009294:Narcotics / Q000008:administration & dosage*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013057:Spectrum Analysis; D013997:Time Factors
chemical_list: D009294:Narcotics; D009020:Morphine