Simple nervous system approach to the mechanisms of associative learning

本研究旨在从生理学和分子生物学的角度阐明学习和记忆的机制。首先，在嗅觉-味觉联合调节后，在分离的麸制剂中，在前脑（蛞蝓的嗅觉中心）进行生理记录，光学记录的膜电位显示，前脑中的一群神经元选择性地对倾斜的气味做出反应。通过mRNA差异显示法，我们发现了一个在嗅觉-味觉联想条件作用后特异性表达升高的基因，并确定了其序列。该基因编码121个氨基酸，命名为LAPS18。为了阐明其功能，我们测定了该基因的表达模式。处理后12-48 h，与对照组相比，LAPS18蛋白的表达量显著增加。这表明LAPS18蛋白与学习的后期事件有关。免疫组织化学分析表明，LAPS18蛋白存在于整个大脑前庭，并在条件反射后定位于大脑前庭的神经层，表明其定位发生了条件反射特异性变化。通过corUoca1激光扫描显微镜，发现LAPS18蛋白定位于神经末梢，特别是细胞接触区域。这些结果表明LAPS18蛋白是一种在神经末梢分泌并调节突触连接的细胞外基质蛋白。在多种脊椎动物中均发现了LAPS18的同源基因。因此，LAPS18被认为在学习和记忆中起着重要的作用。

This work was aimed at clarifying the mechanisms of leaning and memory using physiological and molecular biological methods. First, physiological recordings were made in the procerebrum, which is the olfactory center of the slug, in isolated bran preparations after odor-taste associative conditioning Optical recording of the membrane potential revealed that a cluster of neurons in the procerebrum depolarizes selectively in response to leaned odors.By the mRNA differential display method, we found a gene whose expression elevated specifically after odor-taste associative conditioning, and its sequence has been determined. This gene encoded 121 amino acids, and named LAPS18. To clarify its function, the expression pattern of this gene was determined. The expression of the LAPS18 protein was significantly increased 12-48 h after conditioning compared to the control group. This suggests that the LAPS18 protein is related to the late phase events of learning. Immunohistochemical analysis indicated that LAPS18 protein was present in the entire procerebrum, and localized to the neuropil layers of the procerebrum after conditioning, indicating a conditioning-specific changes in localization. By corUoca1 laser scanning microscopy, the LAPS18 protein was found to be localized to the nerve terminals, especially regions of cell contact. These results suggest that the LAPS18 protein is an extrace11ular matrix protein secreted at nerve terminals and modulate the synaptic connections. The homologue genes of LAPS18 were found in various Vertebrate species. Therefore, LAPS18 was thought to play essential roles in learning and memory.