快眼动睡眠促进记忆巩固的神经和分子机制

The aim of the present project is to determine the neural and molecular mechanism by which REMS facilitates memory consolidation. Numerous studies have shown that rapid eye movement sleep (REMS) plays important roles in memory consolidation. Learning experience can increase the amounts of REMS and the density of pontine waves during REMS, whereas REMS deprivation (RSD) impairs memory, including hippocampus-dependent memory. During REMS, the basal forebrain cholinergic neurons are highly active. The increased release of acetyle cholin is thought to play important role in memory consolidation. Acetyl choline is known to stimulate the phosphorylation of extracellular signal-regulated kinase (ERK) through M1 receptors and increase brain-derived neurotrophic factors (BDNF), both of which play important roles in memory processing. The pontine waves during REMS are generated in a group of glutamatergic neurons in the sub-ceruleus. These neurons project to the hippocampus monosynaptically. The pontine waves also facilitate memory consolidation and stimulate molecules involved in synaptic plasticity such as cAMP, and BDNF. ERK activation is required for different forms of long-term memory. ERK activation also lead to a series of molecular changes (including increased BDNF production) related to memory and synaptic plasticity. RSD decreases ERK in the hippocampus. We hypothesize that the basal forebrain cholinergic neurons and pontine wave generator may facilitate memory consolidation and increase BDNF through activating ERK in the hippocampus during REMS. We will perform three sets of studies to test our hypothesis. First, we will determine the mechanisms for REMS- and learning-induced ERK activation by stimulating or inhibiting cholinerigic M1 receptors in the hippocampus. Second, we will determine the effects of pontine waves on ERK activation during REMS. Third, we will determine whether inhibiting ERK activation can block learning- and pontine waves-induced molecular changes in the hippocampus, and impair hippocampus-dependent spatial memory. These studies will be performed in rats using behavioral, neurophysiological and biochemical means. The successful completion will reveal novel mechanisms for memory consolidation during REMS by establishing cause and effect relationship between neuronal activities, molecular alterations and behavior. Such studies will provide further insight into the mechanisms for memory and functions of sleep, two of the fundamental questions which must be answered by neuroscience.

快眼动睡眠（REMS）在记忆巩固化过程中起重要作用。学习训练可以增加REMS，增强REMS过程中脑桥波的密度。而REMS剥夺（RSD）则可以妨碍记忆，包括海马依赖性的记忆。基底前脑胆碱能神经元在记忆的巩固化过程中起重要作用并在REMS过程中高度活跃。REMS中的脑桥波也可以促进记忆并刺激海马内一些参与记忆的分子活动。本课题旨在研究REMS促进记忆巩固化的神经和分子机制。细胞外信号调节的蛋白激酶（ERK）的激活是记忆和突触可塑性改变过程中的一个关键环节。我们提出，REMS可以通过基底前脑胆碱能神经元和脑桥波激活海马ERK而引起其它分子水平的改变并促进记忆的巩固化。我们将研究： 1）REMS通过激活海马内胆碱能M1受体促进空间记忆巩固化和ERK激活的机制；2）REMS通过脑桥波促进空间记忆和激活海马ERK的机制；3）REMS通过脑桥波激活ERK从而引起海马内分子改变的机制。

学习后睡眠剥夺（SD）包括快眼动睡眠（REMS）剥夺（RSD）夺妨碍记忆的巩固化，但其中的机制仍不十分明了。本项目的目的是研究RSD影响空间记忆的机制。由于REMS伴随着脑内胆碱能系统的激活（后者参与记忆的巩固化过程），我们提出如下假说，RSD可能通过降低脑内胆碱能活动来妨碍空间记忆，而增强脑内胆碱能活动则可能逆转这种作用。.第一，我们发展了一种自动RSD方法。在成年雄性Sprague-Dawley大鼠埋藏脑电和肌电电极，将其保持在１２：１２小时明暗周期中。在睡眠剥夺箱内连续两天记录RSD组（6只大鼠）和对照组（6只大鼠）大鼠的脑电和肌电信号。第一天作为基准对照。第二天RSD从灯亮开始延续８小时。每当计算机程序检测到RSD大鼠的REMS时，物理刺激就施加于RSD大鼠直至其觉醒。同样数量的刺激也施加于对照动组，但集中在每２小时的最后１２分钟。实验结果显示在RSD期间，RSD组的REMS减少了92%，non-REMS（NREMS）减少15%；而对照组的REMS和NREMS都没有显著改变。 第二，我们研究了RSD和胆碱能M1受体激动剂McN-A-343对大鼠在水迷宫中空间记忆的影响。埋藏脑电／肌电电极和脑室内插管的成年雄性大鼠分为4组（每组８只大鼠）：对照+盐水组，RSD+盐水组，对照+McN-A-343组和RSD+ McN-A-343组。大鼠在水迷宫内接受１２次训练（每日４次）去寻找水下站台。每日训练后大鼠接受脑室内盐水或McN-A-343（50微克/5微升）注射。注射后RSD开始，持续８小时。第四天，大鼠在水迷宫内接受空间记忆检测。对照－盐水组在学习和记忆检测中表现最佳。RSD+盐水组的学习曲线最差，在空间记忆检测中表现在随机的水平。McN-A-343处理在对照组轻微地妨碍空间学习和记忆，但却明显改善RSD大鼠的学习和记忆。.第三，我们检测了上述大鼠脑组织中细胞外信号调节蛋白激酶（ＥＲＫ）及其磷酸化的水平。ＥＲＫ的磷酸化在突触可塑性和记忆巩固化中起关键作用。乙酰胆碱也通过M1受体激活ＥＲＫ。我们的初步结果显示，与对照+盐水组相比，RSD+盐水组大鼠皮层和海马的ＥＲＫ磷酸化水平降低，而McN-A-343则逆转了RSD的这种作用。.我们的研究表明，RSD对空间记忆的影响是部分由于降低脑内胆碱能活动而导致的，而增强脑内胆碱能M1受体活动则可以部分地逆转这种作用。