突触重塑是指通过突触形成和消除来重组大脑现有通路的过程,是实现大脑通路布线精细化的必要步骤,在早期发育过程十分普遍,从形态学的数据估算,从运动神经元或脑皮层投射出的突触连接均有约50%在发育过程中消除。神经网络正常的功能依赖于正确的神经回路,而不恰当的突触连接会导致神经系统疾病。突触重塑现象广泛存在,但我们对其分子机理了解甚少。我们借助于简单无脊椎模式动物线虫,研究其发育过程中的突触重塑现象。在发育阶段L1期,DD的背侧分支即树突接受神经元DA和DB释放的乙酰胆碱,其腹侧分支即轴突释放GABA,能松弛腹侧肌肉。在L1期的末期,DD神经元位于腹侧的GABA突触消失,在背侧产生新的突触释放GABA并调节背部肌肉。这样,DD神经元在没有明显形态变化的情况下,经历了一个完全的树突-轴突极性的反转。它们不再接受从DA和DB在背支的输入,开始接收来自VA和VB神经元对其腹支上的递质传递。这一突触重塑使成熟运动回路的建立成为可能。这个重塑以一种确切的、可预见的方式发生,这给我们提供了一个遗传学模式,来探究突触连接可塑性的细胞和分子机制。
图一:DD神经元在L1早期于背侧分支接受乙酰胆碱递质(DA/DB)并从腹侧分支释放GABA。在L1末期发生突触重塑:在背侧分支产生新的突触释放GABA,其腹侧分支接受从神经元VA/VB释放的乙酰胆碱。
1. 国家自然科学基金面上项目(31171197):线虫DD运动神经元突触重塑的分子机制,齐瀛川,2012.01-2015.12,65万元。
论文专著
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