title: Repeated 2 Hz peripheral electrical stimulations suppress morphine-induced CPP and improve spatial memory ability in rats.
abstract: Our previous studies have shown that 2 Hz peripheral electrical stimulation (PES) can suppress morphine-induced conditioned place preference (CPP) in the rat, although the mechanisms remain unclear. Since CPP involves the mechanism of learning and memory, it is rational to ask whether the suppressive effect of repeated 2 Hz PES on morphine-induced CPP is due to an impairment of the function of spatial learning and memory. Rats were trained with 4 mg/kg morphine, i.p. for 4 days to establish the CPP. Twenty-four hours after the CPP testing, they were given PES at 2 Hz once a day for 1, 3 or 5 days, followed by another CPP testing. The results showed that (1) the morphine-induced CPP was significantly inhibited by 3 or 5 consecutive sessions, but not by single session of 2 Hz PES. (2) A test of spatial leaning and memory ability using the Morris water maze task revealed that 2 Hz PES per se exhibited a promoting, rather than a deteriorating effect on the ability of spatial memory. (3) 2 Hz PES by itself produced a moderate yet significant CPP. The results imply that (a) a low frequency PES can produce a rewarding effect as revealed by the CPP testing, which may account, at least in part, for its suppressive effect on morphine induced CPP, (b) the suppressive effect of PES on morphine induced CPP is not due to a deteriorating effect on the ability of spatial memory.
authors.affiliation: Neuroscience Research Institute, Peking University Health Science Center, 38 Xueyuan Road, Beijing 100083, PR China.
authors.forename: Ji-Huan
authors.initials: JH
authors.lastname: Chen
authors.forename: Jing
authors.initials: J
authors.lastname: Liang
authors.forename: Gui-Bin
authors.initials: GB
authors.lastname: Wang
authors.forename: Ji-Sheng
authors.initials: JS
authors.lastname: Han
authors.forename: Cai-Lian
authors.initials: CL
authors.lastname: Cui
mesh_terms: D000818:Animals; D001921:Brain / Q000187:drug effects / Q000503:physiopathology; D003213:Conditioning, Psychological / Q000187:drug effects* / Q000502:physiology; D004195:Disease Models, Animal; D015671:Electroacupuncture; D008297:Male; D018782:Maze Learning / Q000187:drug effects* / Q000502:physiology; D008569:Memory Disorders / Q000139:chemically induced / Q000503:physiopathology / Q000628:therapy*; D009020:Morphine / Q000009:adverse effects; D009021:Morphine Dependence / Q000503:physiopathology / Q000628:therapy*; D009294:Narcotics / Q000009:adverse effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D020127:Recovery of Function / Q000502:physiology; D012201:Reward; D013375:Substance Withdrawal Syndrome / Q000503:physiopathology / Q000517:prevention & control / Q000628:therapy*; D016896:Treatment Outcome
chemical_list: D009294:Narcotics; D009020:Morphine