东莨菪碱对大鼠空间参考记忆和工作记忆的不同影响

观察东莨菪碱对空间参考记忆和空间工作记忆的编码、保持和提取过程的作用。应用Morris水迷宫实验测定大鼠的空间参考记忆和空间工作记忆，分别在训练的不同阶段腹腔注射东莨菪碱（1mg/kg）和相同容量的生理盐水，比较各东莨菪碱组和生理盐水组之间游泳潜伏期、路径长度、轨迹和游泳速度的差异。结果发现：与注射生理盐水相比，在训练前和探测实验前注射东莨菪碱的大鼠在探测实验中对目标象限不表现出空间偏爱，说明东莨菪碱干扰参考记忆的信息编码和提取过程；而在训练结束后注射东莨菪碱的大鼠探测实验的结果与生理盐水组相比没有显著差异，说明东莨菪碱对参考记忆的保持过程没有影响。在工作记忆实验中，无论第一次测试前、第一次测试后和第2次测试前注射东莨菪碱，均造成大鼠游泳潜伏期延长，说明东莨菪碱干扰工作记忆的编码、保持和提取过程。研究提示M受体在空间工作记忆和参考记忆中发挥不同作用

Scopolamine Has Different Influences on Spatial Reference Memory and Spatial Working Memory in Rats

Despite of many years of intensive studies, the role of cholinergic system in spatial reference memory and spatial working memory remains controversial. It was found that scopolamine, an antagonist to cholinergic muscarinic receptor, impaired the encoding and retrieval process of spatial memory. It was also found that the spatial working memory was more sensitive to muscarinic receptor antagonists than spatial reference memory. In this study, the effects of scopolamine on the acquisition, retention and retrieval processes of spatial reference memory and spatial working memory were observed and compared using the Morris water maze (MWM) task. Experiment 1 were performed on 46 adult rats, which were divided randomly into 6 groups and trained in a reference memory version of the MWM with two blocks of four trials per day for three consecutive days. Scopolamine was injected (1 mg/kg, i.p.) 20 min prior to the day’s first trial in group 1, immediately after the day’s last trial in group 2, or 20 min prior to the probe trial in group 3. The remaining 3 groups were injected with saline for control. Experiment 2 were performed on 42 adult rats, which were divided randomly into 6 groups and trained in a working memory version of the MWM task to find a new target position (trial 1). Retrieval (trial 2) was tested 75 min later. Similar to experiment 1, scopolamine was injected (1 mg/kg, i.p.) 20 min prior to trial 1 in group 1, immediately after trial 1 in group 2, or 20 min prior to trial 2 in group 3. The remaining 3 groups were injected with saline for control. The swimming latency, length, strategy and velocity were recorded. For experiment 1, animals in group 1 and group 3 showed deteriorated learning curves and no spatial bias to the goal quadrant was observed, indicating that scopolamine interfered encoding and retrieval process of the spatial reference memory. Animals in group 2 showed no significant difference from the saline control, indicating that scopolamine has no effects on the retention of spatial reference memory. For experiment 2, animals in all the three groups showed significant prolongation of swimming latency, indicating that the scopolamine impaired encoding, retention, and retrieval of the spatial working memory. In conclusion, the present study demonstrated that the muscarinic receptors played differential roles in spatial working memory and spatial reference memory.