Rapid, activity-independent turnover of vesicular transmitter content at a mixed glycine/GABA synapse.
Rapid, activity-independent turnover of vesicular transmitter content at a mixed glycine/GABA synapse.
复制标题
DOI：
10.1523/jneurosci.5555-12.2013
复制
发表时间：
2013-03-13
期刊：
影响因子：
--
通讯作者：
Trussell LO
中科院分区：
文献类型：
--
作者：
Apostolides PF;Trussell LO
通过充满递质的突触前囊泡的融合释放神经递质是神经元传递信息的主要方式。然而，很少有人知道的分子机制，供应神经递质注定为囊泡填充，突触前神经末梢内的内源性递质浓度或胞吐后囊泡再填充的动力学。我们通过记录小鼠耳蜗背核的甘氨酸/GABA共释放中间神经元（车轮细胞）的突触耦合对来解决这些问题。我们发现，质膜转运蛋白GlyT 2和细胞内酶谷氨酸脱羧酶供应的大部分甘氨酸和GABA，分别。GlyT 2或谷氨酸脱羧酶的药理学阻断导致传输的快速和完全下降，而通过细胞内谷氨酸释放增加GABA合成在一分钟内显著增强GABA释放。令人惊讶的是，这些影响是独立的胞吐作用，表明预填充囊泡重新平衡后，细胞溶质递质的急性变化。滴定与突触后反应的胞质递质表明，内源性，非囊泡甘氨酸/GABA的神经末梢水平为5至7毫米，囊泡运输机制不饱和的基础条件下。因此，胞质递质水平动态地以不依赖于释放的方式设置抑制性突触的强度。
The release of neurotransmitter via the fusion of transmitter-filled, presynaptic vesicles is the primary means by which neurons relay information. However, little is known regarding the molecular mechanisms that supply neurotransmitter destined for vesicle filling, the endogenous transmitter concentrations inside presynaptic nerve terminals or the dynamics of vesicle refilling after exocytosis. We addressed these issues by recording from synaptically-coupled pairs of glycine/GABA co-releasing interneurons (cartwheel cells) of the mouse dorsal cochlear nucleus. We find that the plasma membrane transporter GlyT2 and the intracellular enzyme glutamate decarboxylase supply the majority of glycine and GABA, respectively. Pharmacological block of GlyT2 or glutamate decarboxylase led to rapid and complete rundown of transmission, whereas increasing GABA synthesis via intracellular glutamate uncaging dramatically potentiated GABA release within one minute. These effects were surprisingly independent of exocytosis, indicating that pre-filled vesicles re-equilibrated upon acute changes in cytosolic transmitter. Titration of cytosolic transmitter with postsynaptic responses indicated that endogenous, non-vesicular glycine/GABA levels in nerve terminals are 5 to 7 mM, and that vesicular transport mechanisms are not saturated under basal conditions. Thus, cytosolic transmitter levels dynamically set the strength of inhibitory synapses in a release-independent manner.