Skibo G G, Davies H A, Rusakov D A, Stewart M G, Schachner M
Department of Biology, Open University, Milton Keynes, U.K.
Neuroscience. 1998 Jan;82(1):1-5. doi: 10.1016/s0306-4522(97)00382-5.
An area of the chick striatum, the lobus parolfactorius plays an important role in one-trial passive avoidance learning tasks. In the present study we report evidence that 5-6 h post-training, a significantly higher proportion of synaptic active zones in this area contain labelled epitopes of the neural cell adhesion molecule, with the greatest occurrence of labels at the edges of active zone profiles (in both control and trained groups). This suggests that there is a period after training when expression of the neural cell adhesion molecule in synaptic membranes almost doubles, and that events at active zone edges may play a specific role in mechanisms of synaptic adhesion. Cellular mechanisms of long-term memory formation are believed to include alterations in neural circuitry at the synaptic level. The involvement of the neural cell adhesion molecule (NCAM) in functional synaptic modifications has been demonstrated using a number of physiological models. Performance of rats in the Morris water maze, a spatial learning paradigm which requires the hippocampus, is impaired by either intraventricular injection of NCAM antibodies, or injection into the hippocampus of an enzyme which increases homophilic adhesion of the molecule, due to the removal of polysialic acid residuals from extracellular NCAM domains. In addition, intraventricular injections of anti-NCAM antibodies 6-8 h post-training were shown to impair memory for a one-trial passive avoidance task in the rat. An avoidance training model in the one-day-old chick indicates a similar time window, 5-6 h post-training during which memory for the task can be impaired by intraventricular injection of NCAM antibodies. In the hyperstriatum ventrale, a chick forebrain area involved in the passive avoidance task. subtle changes in the distribution pattern, but not density of NCAM molecules in synaptic membranes were revealed 5-6 h post-training. However, on the basis of studies of synaptic morphometry, a region of striatum, the lobus parolfactorius (LPO), appears to play a more important role in longer term memory storage for the task.
鸡纹状体的一个区域，即嗅觉旁叶，在单次被动回避学习任务中起重要作用。在本研究中，我们报告了这样的证据：训练后5 - 6小时，该区域中突触活性区含有神经细胞黏附分子标记表位的比例显著更高，标记在活性区轮廓边缘出现的频率最高（在对照组和训练组中均如此）。这表明训练后存在一个时期，突触膜中神经细胞黏附分子的表达几乎翻倍，并且活性区边缘的事件可能在突触黏附机制中起特定作用。长期记忆形成的细胞机制被认为包括突触水平神经回路的改变。使用多种生理模型已经证明神经细胞黏附分子（NCAM）参与功能性突触修饰。在需要海马体参与的空间学习范式——莫里斯水迷宫中，大鼠的表现会因脑室内注射NCAM抗体或向海马体注射一种酶（该酶会增加分子的同源黏附，因为它会去除细胞外NCAM结构域中的多唾液酸残基）而受损。此外，训练后6 - 8小时脑室内注射抗NCAM抗体被证明会损害大鼠单次被动回避任务的记忆。一日龄雏鸡的回避训练模型表明存在类似的时间窗口，即训练后5 - 6小时，在此期间脑室内注射NCAM抗体可损害该任务的记忆。在腹侧上纹状体，一个参与被动回避任务的雏鸡前脑区域，训练后5 - 6小时，突触膜中NCAM分子的分布模式而非密度出现了细微变化。然而，基于突触形态学研究，纹状体的一个区域，即嗅觉旁叶（LPO），似乎在该任务的长期记忆存储中发挥更重要的作用。
