药物成瘾被认为是药物长期作用于脑而产生的一种慢性复吸性脑疾病，长期反复的药物（如吗啡）滥用会导致一系列严重后果，如药物依赖、药物耐受、强迫性药物寻求等。本实验利用条件化位置偏好（conditioned place preference，CPP）模型来检测大鼠对吗啡依赖和心理渴求等过程；采用双声刺激听觉诱发电位来研究大鼠在慢性吗啡给予、戒断以及再给药过程中海马感觉门控（N40）的动态变化。吗啡组大鼠注射吗啡（10mg／kg，i．p．）12d，经历第一次戒断12d，再次注射吗啡（2．5mg／kg，i．P．）1d，之后经历第二次戒断2d；对照组大鼠注射同体积生理盐水，其余实验条件与吗啡组相同。CPP实验表明，这种药物给予方法促使大鼠对吗啡产生药物依赖和心理渴求。双声刺激诱发电位实验表明，吗啡组大鼠在吗啡给予期间海马感觉门控受到损伤；第一次戒断期的第1～2天海马感觉门控能力减弱，第3天增强，第4～12天逐渐恢复到正常水平；再次给予吗啡后海马感觉门控能力与对照组相比显著降低，并且随后2d的戒断期内海马感觉门控能力也一直保持较低水平，表明再次给药使大鼠海马感觉门控对吗啡更加敏感化。结果提示，长期反复的吗啡给予及再给药干扰了海马的感觉门控能力，吗啡成瘾对大脑可能产生长期影响。
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.
