鸡小脑向海马结构直接与间接投射的比较

The neural circuit involved in the functions of emotional and memory is an important content of modern neuroscience. Contemporary neuroscience point of view that the cerebellum is not only a structure of the brain to regulate body movement, but also involve in many brain high-level functions， such as memory, cognition, and emotion regulation.It has been proven that indirect projection from cerebellum to the hippocampus is exist in the mammals. However, no direct projection was reported. Our preliminary work has proven the existence of a direct projection from the cerebellar cortex to the hippocampus in the chicken. On the basis of the original work, the present project will use neural tracing methods, electron microscopy, electrolytic brain lesion, immunohistochemistry to perform further study of the direct cerebello-hippocampus projetions in chickens on the path, ultrastructure of the synapse, neurotransmitters and function of the nerve pathway. By the way, we will further explore the posibility of the indirect projection from the deep cerebellar nuclei to the hippocampus. So that we can compare the details of the structure and function of the direct projection to that of indirect projection and offer a simple animal model to research neural circuits involving the emotions and memories.

"情绪与记忆的神经环路"是现代神经科学的重要研究内容。当代神经科学观点认为小脑不单是一个调控运动机能的脑结构，而且参与许多高级脑功能，如记忆、认知、情绪调节等。在哺乳类已经证明小脑向海马有间接的投射，然而尚无直接投射的报道。本项目组前期工作已经初步证实在鸡存在直接的小脑皮层向海马的直接投射。本项目即是在原有工作基础上采用神经示踪、电镜、电损毁、免疫组化等方法进一步研究鸡这一投射的路径、终止部位、超微结构、神经递质以及功能，并进一步探索小脑深核有无到海马的间接投射，通过与直接投射的比较，揭示直接投射通路的具体构造和功能，为研究"情绪与记忆的神经环路"提供更为简洁的动物模型。

本项目在前期研究的基础上，进一步采用顺行示踪、溃变电镜和HRP逆行顺行追踪法证明鸡小脑皮质向海马结构的直接投射的具体部位以及与间接投射通路在投射部位、突触结构等方面的差异和关系。结果表明，在HRP逆行示踪所获知的蒲氏细胞投射到海马结构的结果并未被顺行溃变法在超微结构水平所证实，即损毁小脑蒲氏细胞，没有在海马结构发现暗型溃变终末，初步说明不存在小脑蒲氏细胞到海马结构的直接投射。关于间接投射途径，采用HRP发现投向海马结构的丘脑中继核是浅小细胞核和圆下核，在鸡脑横切面上看它们与小脑深核投射到丘脑的靶区丘脑腹中间区（VIA）在位置上不重叠，存在大约1-2mm的距离，提示由蒲氏细胞向海马结构投射的三级神经元通路不存在，可能存在多于三级神经元的神经通路。由于未能证实直接投射的确切靶区，本项目未能进行直接投射和间接投射在路径上的差异比较。.在HRP注射海马的实验中初步发现海马结构可投射到中脑红核。但是我们未能排除HRP被海马结构内的过路纤维所吸收的可能，如能排除这种可能，证实海马结构直接投射到红核将具有重要学术价值，是为本项目后续计划之一。