The orbitofrontal cortex （OFC） is particularly important for the neural representation of reward value. Previous studies indicated that electroencephalogram （EEG） activity in the OFC was involved in drug administration and withdrawal. The present study investigated EEG activity in the OFC in rats during the development of food reward and craving. Two environments were used separately for control and food-related EEG recordings. In the food-related environment rats were first trained to eat chocolate peanuts; then they either had no access to this food, but could see and smell it （craving trials）, or had free access to this food （reward trials）. The EEG in the left OFC was recorded during these trials. We showed that, in the food-related environment the EEG activity peaking in the delta band （2-4 Hz） was significantly correlated with the stimulus, increasing during food reward and decreasing during food craving when compared with that in the control environment. Our data suggests that EEG activity in the OFC can be altered by food reward; moreover, delta rhythm in this region could be used as an index monitoring changed signal underlying this reward.
The interaction of morphine and cholinergic system was shown in previous studies. In the present study, we investigated whether morphine would interact with the cholinergic antagonists, scopolamine and atropine in a Y-maze spatial recognition memory. Pre-test treatments of morphine （5, 1.5, 0.5 mg/kg）, scopolamine （1, 0.1 mg/kg）, atropine （0.5, 0.1 mg/kg） were used in the experiments, relatively high or low doses were paired respectively as co-administration measures. The results showed that co-administration of morphine 0.Smg/kg ~ scopolamine 0.1 mg/kg and morphine 0.5 mg/kg ＋ atropine 0.1 mg/kg disturbed the inspective exploratory behavior （percent of arm duration） but not the inquisitive behavior （percent of arm visits） of the spatial memory retrieval, while the drugs didn＇t cause amnesia when single administered of the concerned low doses. Distinct interaction was found between scopolamine and morphine on increasing locomotor activity.
该实验通过采用吗啡诱导的条件位置偏爱(conditioned place preference,CPP)与食物诱导CPP相结合的方法来研究青春期小鼠和成年小鼠的普通学习记忆和成瘾学习记忆之间是否存在差异。结果发现:1)成年小鼠能够建立吗啡诱导CPP,而青春期小鼠不能建立;2)青春期小鼠和成年小鼠都能够建立食物诱导CPP。吗啡诱导CPP的结果提示,青春期小鼠和成年小鼠在成瘾学习记忆上有差异,青春期小鼠的成瘾记忆能力较弱。食物诱导CPP的结果提示,青春期小鼠和成年小鼠在普通学习记忆上没有差异。吗啡诱导CPP和食物诱导CPP的结果比较提示,小鼠的普通学习记忆系统和成瘾学习记忆系统发育进程是不平行的。
