母体七氟醚暴露致子代情绪障碍：突触粘附分子β-neurexin/neuroligin 1的作用及机制

There is an increasing concern on the neurotoxicity of currently used general anesthetics, which are neurotoxic to the developing brain and subsequently lead to late-onset cognitive impairments. However, their effects on mood development remain unknown. Our previous study has shown that mid-trimester general anesthetic exposure to pregnant rats induces mood disorders, together with cognitive impairments in offspring rats, which is associated with abnormal dendritic dysplasia and expression of NMDA receptor (NMDAR) subunits and PSD-95 in the hippocampus and medial prefrontal cortex (mPFC), however the underlying mechanisms remain unknown. Recent evidence highlights the importance of a trans-synaptic interaction between postsynaptic neuroligin 1 (NL 1) and presynaptic β-neurexin (β-NX), which binds each other extracellularly to promote adhesion between dendrites and axons to further enhance postsynaptic differentiation and clustering of receptors in dendrites. The disturbance in neuroligin and neurexin genes is associated with the neurodevelopmental disorder. Accordingly, we propose that general anesthetics, e.g. sevoflurane, disrupt NMDAR, reversely mediate β-NX/NL 1-PSD95, induce synaptic dysplasia, and lead to late-onset mood disorders. In this project, we will use behavioral tests, electron microscopy and confocal laser methods, to determine the effects of maternal sevoflurane exposure on NMDAR and β-NX/NL 1 expression, morphological synaptic changes, and long-term emotional developments. We aim to prove the role that NMDAR reversely mediatesβ-NX/NL 1-PSD95 trans-synaptic signals in the general anesthetic-induced neurotoxicity. This work will provide a theoretical basis for the prevention of neurotoxicity induced by general anesthetics.

全麻药大脑发育期暴露可致远期认知损害，但其对情绪的影响未知。我们前期研究表明孕中期母体全麻药暴露致子代成年后情绪障碍，海马和前额皮质神经元树突发育不良，N-甲基-D天冬氨酸受体（NMDAR）亚基及突触后致密蛋白（PSD95）表达紊乱，但机制不明。最新研究表明，β-neurexin/neuroligin 1（β-NX/NL 1）与PSD95-NMDAR形成的跨突触信号，介导树突发育、突触分化；其异常可致精神疾病。据此我们推测：全麻药扰乱NMDAR，反向调节β-NX/NL 1-PSD95致突触发育异常是其神经毒性的重要机制。本项目拟采用行为学、电镜、激光共聚焦等方法，观察母体七氟醚暴露对子代远期情绪及神经发育期NMDAR亚基、β-NX、NL 1、突触结构的影响，证实NMDAR调节β-NX/NL 1-PSD95跨突触信号在七氟醚致子代情绪障碍中的作用，为全麻药毒性防治提供重要理论依据。

背景：全麻药对发育中的大脑的神经毒性作用是医学界和公众非常关注的问题。迄今为止，既往的临床前研究主要集中于全身麻醉暴露后神经元死亡。在我们采用孕鼠七氟醚暴露后，研究其后代情感障碍及潜在的机制。.方法：妊娠14.5天，处于神经细胞切线迁移的高峰期，临床剂量七氟醚吸入3小时，采用行为学试验、细胞超微结构分析、免疫组织化学和电生理学方法，对青少年和成年前期的大鼠进行研究。.结果：青少年和成年前期的子代均存在空间学习障碍和焦虑、抑郁样情绪障碍。小清蛋白阳性（PV+）中间神经元、GABA囊泡转运体（VGAT）和GABA合成酶GAD67表达增加，而谷氨酸转运体1（VGLUT1）囊泡的表达下降。此外，还发现前额叶皮层（mPFC）锥体神经元出现超微结构（树突、树突棘和突触）的异常。且膜片钳记录显示mPFC锥体神经元抑制性突触后电流（eIPSCs）和兴奋性突触后电流（eEPSCs）的失衡，明显向抑制方向变化。进一步的研究发现突触后膜NMDA受体亚基NR1、NR2A、NR2B及突触粘附分子NL1/NL2、β-neurexin表达的发育时间趋势延迟。.结论：本研究首次证实七氟醚宫内暴露可引起子代mPFC区中间能神经元发育障碍，兴奋性/抑制性神经传递的失衡，最终导致皮层神经元及其回路的异常和行为障碍。我们推测突触后膜受体及突触粘附分子的时空性改变可能是突触兴奋性/抑制性神经传递失衡的重要机制。