Release probability-dependent scaling of the postsynaptic responses at single hippocampal GABAergic synapses.
Release probability-dependent scaling of the postsynaptic responses at single hippocampal GABAergic synapses.
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单个海马GABA能突触的突触后反应的释放概率依赖性尺度。
DOI：
10.1523/jneurosci.3106-06.2006
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发表时间：
2006-11-29
期刊：
影响因子：
--
通讯作者：
Nusser Z
中科院分区：
文献类型：
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作者：
Biró AA;Holderith NB;Nusser Z
动作电位到达后释放的神经递质量影响突触后反应的强度和各试验间的可变性。研究突触神经递质浓度对释放概率（Pr）依赖性的研究大多集中在谷氨酸突触上。在这里，我们询问了单泡或多泡释放是否以海马gaba能突触的传递为特征。我们使用多重概率泛函数分析来推导大麻素受体和胆囊收缩素（CCK）表达的中间神经元和CA3锥体细胞之间抑制性连接的量子参数。记录后，在光镜水平下对细胞进行可视化和重建，并通过电子显微镜（EM）测定介导IPSCs的钮扣数量。每个cck免疫阳性钮扣的活性区（AZs）数量由三维EM重建确定，从而可以计算每对AZs的总数。我们的研究结果显示，功能确定的释放位点数量（17.4±3.2）与结构确定的AZs数量（3.7±0.9）相差约5倍。通道模型预测，突触后反应的五倍增强需要突触峰值GABA浓度增加五到七倍。单一IPSCs的动力学分析表明，突触GABA浓度的增加很可能归因于多泡释放。突触中短暂的GABA浓度变化加上极低的突触后受体占用率，使得单海马GABA能突触接触产生的突触后反应具有pr依赖性。
The amount of neurotransmitter released after the arrival of an action potential affects the strength and the trial-to-trial variability of postsynaptic responses. Most studies examining the dependence of synaptic neurotransmitter concentration on the release probability (Pr) have focused on glutamatergic synapses. Here we asked whether univesicular or multivesicular release characterizes transmission at hippocampal GABAergic synapses. We used multiple probability functional analysis to derive quantal parameters at inhibitory connections between cannabinoid receptor- and cholecystokinin (CCK)-expressing interneurons and CA3 pyramidal cells. After the recordings, the cells were visualized and reconstructed at the light-microscopic level, and the number of boutons mediating the IPSCs was determined using electron microscopy (EM). The number of active zones (AZs) per CCK-immunopositive bouton was determined from three-dimensional EM reconstructions, thus allowing the calculation of the total number of AZs for each pair. Our results reveal an approximate fivefold discrepancy between the numbers of functionally determined release sites (17.4 ± 3.2) and structurally identified AZs (3.7 ± 0.9). Channel modeling predicts that a fivefold to sevenfold increase in the peak synaptic GABA concentration is required for the fivefold enhancement of the postsynaptic responses. Kinetic analysis of the unitary IPSCs indicates that the increase in synaptic GABA concentration is most likely attributable to multivesicular release. This change in the synaptic GABA concentration transient together with extremely low postsynaptic receptor occupancy permits a Pr-dependent scaling of the postsynaptic response generated at a single hippocampal GABAergic synaptic contact.