内嗅皮层来源的胆囊收缩素在海马长时程增强中的作用

Our previous studies show that entorhinal cortex enables the plasticity of auditory cortex through cholecystokinin (CCK). Many experiments demonstrate that long-term potentiation (LTP) is the mechanism of brain plasticity and learning & memory. In this project, we will study the relationship between entorhinal CCK and hippocampal LTP. (1) AAV virus will be injected into the entorhinal cortex of CCK-CRE transgenic mice. Then the projections of CCK neurons from entorhinal cortex to hippocampus will be confirmed. (2) On anesthetized rats CCKB antagonist will be injected into the hippocampus to see whether it can block the formation of LTP induced by θ burst stimulation, and CCKB agonist will be injected to see whether it can directly induce LTP. On CCK knock out mice, it will be checked that whether θ burst stimulation can still induce LTP. (3) By using optogenetic technique, it will be examined that whether high frequency laser stimulation on CCK fibers projecting from entorhinal cortex to hippocampus can induce LTP. (4) The performance of CCK knock out mice will be checked in Morris water maze to see whether their learning and memory ability is deteriorated. CCKB antagonist will also be injected into the hippocampus of wildtype mice to see its influence on learning and memory. This study will show the role of CCK from entorhinal cortex on the formation of LTP in hippocampus and it will provide more clues to help us understand the mechanism of learning and memory.

我们之前的研究发现内嗅皮层的神经元通过胆囊收缩素（CCK）控制听皮层的可塑性。另一方面，许多研究表明长时程增强（LTP）是大脑可塑性与动物学习记忆的基础。在本研究中，我们将探索内嗅皮层来源的CCK与海马LTP的关系。（1）在CCK-CRE转基因小鼠上注射病毒确定内嗅皮层CCK神经元对海马区域的投射；（2）在麻醉大鼠上观察CCKB受体拮抗剂能否阻断高频刺激诱发的海马LTP，CCK受体激动剂能否直接诱发海马LTP，在CCK敲除小鼠上观察高频电刺激能否仍然诱发LTP；（3）通过光遗传技术特异的激活内嗅皮层CCK神经元到海马的投射，观察其能否诱发LTP；（4）在CCK敲除小鼠上观察其学习与记忆能力是否受损，在C57小鼠上观察海马注射CCKB受体拮抗剂是否能够降低动物的学习记忆能力。本计划将揭示内嗅皮层投射到海马的CCK与海马LTP之间的关系及其在学习记忆中的作用。

已有的证据显示胆囊收缩素（CCK）参与神经可塑性和记忆的形成。在本项目中，我们发现来源于内嗅皮层的CCK能神经元投射到海马，促使海马CA3区到CA1区的长时程增强形成（LTP）。在CCK敲除转基因小鼠的海马区，Ɵ节律刺激不能诱发LTP，且它们的空间学习记忆能力有缺陷。高频激光特异性的刺激内嗅皮层CCK能神经元在海马的投射能够释放CCK，且能够促使CA3区到CA1区的LTP形成。该LTP的形成主要是由CCK A型受体介导的。通过shRNA下调内嗅皮层CCK表达可以阻断CA3区到CA1区LTP的形成。与之相对的是直接刺激海马CCK能神经元或者Schaffer分支不能形成LTP。我们的结果表明CCK在海马区的神经可塑性调控及空间记忆形成中起到重要作用。