GABA(A)R去极化激活VGCCs在七氟烷致新生小鼠远期认知功能障碍中的作用机制

Human studies have shown that infants with long periods of exposure to sevoflurane are at a significantly increased risks of neurocognitive impairments. Our previous studies have demonstrated that sevoflurane can induce Seizure-like EEG and cause cognitive dysfunction in the future on neonatal mice. However,the mechanism of the damage is still not clear. We hypothesize ,based on results acquired from our previous researchs and data from other literatures,that sevoflurane can induce γ-aminobutyric acid (GABA) type A receptor GABA(A)R-mediated depolarization/excitation in immature hypothalamic neurons. The depolarization will be followed by the open of Voltage-Gated Calcium Channels(VGCCs),and excassive Ca2+ infiux can result in intercellolar calcium overload in neurons,which is going to have adverse effects on the proliferation and maturity of cortical profenitor cell,and the growth of axon,resulting in long-term cognitive dysfunction. We will use the NKCC1 gene kuockout mouse model and whole cell patch clamp technique to measure excitatory postsynaptic current of hippocampal slices in vitro, VGCCs and uncaging-evoked inhibitory postsynaptic currents on new axone.The proliferation and maturity of hippocampal neurons in vitro,excitatory EEG and morphological structure of newborn neurons’ axone will be observed respectively by flow cytometry, Cortex EEG monitoring model and immunofluorescent hisochemical staining method.We are trying to expore the mechanism of the neurocognitive impairment caused by sevoflurane is related to GABA(A)R-mediated depolarization/excitation and the activation of VGCCs.

研究显示婴幼儿期长时间接受麻醉后成年期出现认知功能异常的风险显著增加，我们前期的研究提示七氟烷可诱发新生鼠EEG异常，并可导致远期认知功能障碍，但机制尚不明确。根据我们前期的研究及文献推测小鼠新生期七氟烷通过GABA(A)R去极化，激活电压门控钙离子通道(VGCCs)，致细胞内钙离子聚集，激活下游钙依赖性基因表达通路，对神经发育产生影响，从而导致远期认知障碍。本研究拟使用NKCC1基因敲除小鼠，观察七氟烷对兴奋性EEG、远期认知功能及突触电活动的影响，确定其机制是否和GABA(A)R去极化/兴奋有关。膜片钳技术测定海马突触后兴奋性电流、VGCCs电流及新树突电流，观察GABA(A)R是否引起VGCCs激活并影响树突发育。应用细胞生物学观察新生神经元发育及海马神经祖细胞增殖、成熟及凋亡的情况，探讨GABA(A)R去极化/兴奋诱发的VGCCs激活通路是七氟烷致远期认知障碍的主要机制。

研究显示婴幼儿期长时间接受麻醉后成年期出现认知功能异常的风险显著增加，我们前期的研究提示七氟烷可诱发新生鼠EEG异常，并可导致远期认知功能障碍，但机制尚不明确。根据我们前期的研究及文献推测小鼠新生期七氟烷通过GABA(A)R去极化，激活电压门控钙离子通道(VGCCs)，致细胞内钙离子聚集，激活下游钙依赖性基因表达通路，对神经发育产生影响，从而导致远期认知障碍。本研究拟观察七氟烷对兴奋性EEG、远期认知功能及突触电活动的影响，确定其机制是否和GABA(A)R去极化/兴奋有关。膜片钳技术测定神经元VGCCs电流及新树突电流，观察GABA(A)R是否引起VGCCs激活并影响树突发育。应用细胞生物学观察新生神经元发育及海马神经祖细胞增殖、成熟及凋亡的情况，探讨GABA(A)R去极化/兴奋诱发的VGCCs激活通路是七氟烷致远期认知障碍的主要机制。 .本课题研究发现七氟烷通过NKCC1-GABA(A)R-VGCCs通路发挥作用导致新生小鼠产生远期认知功能障碍。七氟烷可导致小鼠海马神经元NKCC1、GABAAR及VGCCs的表达升高，并且导致小鼠海马的炎症反应升高，促进了海马神经元的凋亡，抑制海马DG区神经元的增殖，同时导致小鼠神经元树突棘密度降低，从而导致小鼠远期认知功能障碍的产生。NKCC1的抑制剂布美他尼、GABAAR的抑制剂荷包牡丹碱、VGCCs的抑制剂硝苯地平均可缓解七氟烷造成的远期认知功能障碍。