基于中枢胆碱能系统研究七氟烷致认知障碍的海马环路多靶点机制

The mechanism of postoperative cognitive dysfunction（POCD） is still unclear, the reason of the limited therapeutic effect is closely related to the complex mechanism of anesthetics action presently.Hence,it is of great value to study on the mechanism of POCD induced by sevoflurane based on central cholinergic system. Our previous studies found that sevoflurane anesthesia may lead to impairment of learning and memory ability in neonatal rats and aged rats, and cause β-amyloid protein(Aβ) deposition in hippocampus in neonatal period. In view of the close relationship between Aβ and central cholinergic system, we speculate that sevoflurane might cause changes in hippocampal neurons ,inhibit LTP and finally trigger behavioral changes by affecting the central cholinergic system. Thus, this project is to observe the effects of sevoflurane on the functional activities of the hippocampus by functional magnetic resonance imaging(fMRI) and then observe the connections between hippocampal neurons and synapses according to establish sevoflurane inhalational anesthesia model in neonatal rats and in aged rats ; Observe changes of ChAT,Ach,α7nAChR and AChE in hippocampus after confirm the connections between hippocampal neurons and synapses damaged by sevoflurane,and observe changes of Ach and α7nAChR by AChE gene silencing;Lastly, electrophysiological changes of hippocampus will be observed. This study aims to explore the mechanism of multiple targets in hippocampus of sevoflurane anesthesia on POCD in the two vulnerable periods of the central nervous system and to provide basis for the prevention and treatment of POCD.

术后认知功能障碍（POCD）发病机制不明，目前药物疗效有限的原因与麻醉药作用机制复杂关系密切。因此，基于中枢胆碱能系统研究七氟烷致认知功能障碍的机制具有重要价值。课题组前期研究发现七氟烷损害新生期、老龄期大鼠学习记忆能力，引起新生期海马Aβ沉积。鉴于Aβ与中枢胆碱能系统关系密切，我们推测，七氟烷通过作用于中枢胆碱能系统，引起海马神经元改变、抑制LTP等最终引发行为学改变。所以，本项目首先建立新生期和老龄期大鼠吸入七氟烷模型，通过fMRI观察七氟烷对海马脑区功能活动的影响，然后观察海马神经元胞体和突触链接；在明确七氟烷损伤海马神经元和突触链接的基础上，再观察海马ChAT、ACh、α7nAChR、AChE变化，并通过AChE基因沉默技术观察ACh、α7nAChR的变化；最后观察海马电生理改变。本研究旨在探索七氟烷致中枢神经系统两个易损期认知功能障碍的海马多靶点机制，为POCD防治提供理论依据。

项目首先研究了新生大鼠七氟烷麻醉后海马α7nAChR、AChE和ChAT表达的变化、蛋白含量变化，同时观察了大鼠海马Tau蛋白基因的调控作用。然后成功建立了稳定的衰老大鼠“人工脑老化”大鼠模型。这一研究成果为脑科学实验提供了较好的老龄大鼠模型，在此领域应用前景向好。可以有效减少大鼠自然老化周期和自然生长的意外死亡等损耗，节约研究周期，同时缓解了市场购买研究用之老龄大鼠十分困难的局面。最后，项目完成了衰老大鼠的海马MRI、超微结构观察和海马α7nAChR、AChE和ChAT等指标的监测。实验结果初步揭示了吸入七氟烷麻醉大鼠短期内的学习记忆能力减退的机制与中枢胆碱能系统功能紊乱有关，观察到PNU-282987激动α7nAChR学习能力较前有明显改善。该结果的科学意义在于，麻醉后短期内认知功能紊乱的治疗可以此为依据，通过药物激动或保护α7nAChR可保护性预防近期的神经功能紊乱或使紊乱程度减弱。研究结果未发现吸入七氟烷后新生大鼠、衰老大鼠出现永久性的麻醉后认知障碍。本项目研究进展顺利，研究内容已经全部完成。