Use Dependence of Presynaptic Tenacity
Use Dependence of Presynaptic Tenacity
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DOI：
10.1523/jneurosci.3384-11.2011
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发表时间：
2011-11-16
影响因子：
5.3
通讯作者：
Ziv, Noam E.
中科院分区：
文献类型：
--
作者：
Fisher-Lavie, Arava;Zeidan, Adel;Ziv, Noam E.
最近的研究表明，突触小泡（SV）在附近的突触之间以非常显着的速率持续交换。这些动态以及缺乏将突触小泡限制在特定突触的明显障碍似乎挑战了突触在长时间尺度内维持恒定数量的突触小泡的能力。此外，与突触前活动相关的突触小泡的广泛动员可能会加剧这一挑战。在这里，我们检查了大鼠海马神经元的单个突触前神经元维持其突触小泡含量的能力，以及这种能力受连续活动影响的程度。我们发现属于同一轴突的各个突触小泡的含量在几个小时内逐渐发生变化，并且这些变化的发生与活动无关。 1 小时的间歇刺激加速了囊泡池大小的变化。然而有趣的是，刺激停止后，囊泡池大小变化率逐渐与基础变化率趋同。在相似的时间尺度上，活跃区（AZ）表现出显着的重塑；然而，与突触小泡不同，AZ 重塑不受此处使用的刺激范例的影响。这些发现表明，增强的活动水平可以增加附近突触之间的突触小泡重新分布，但也强调了恢复 SV 含量特定设定点的力量的存在，并支持活性区在保留此类设定点方面的作用。然而，这些发现也表明，AZ 大小和 SV 内容设定点都不是特别稳定，这对突触前特化的长期坚韧提出了质疑。
Recent studies indicate that synaptic vesicles (SVs) are continuously interchanged among nearby synapses at very significant rates. These dynamics and the lack of obvious barriers confining synaptic vesicles to specific synapses would seem to challenge the ability of synapses to maintain a constant amount of synaptic vesicles over prolonged time scales. Moreover, the extensive mobilization of synaptic vesicles associated with presynaptic activity might be expected to intensify this challenge. Here we examined the ability of individual presynaptic boutons of rat hippocampal neurons to maintain their synaptic vesicle content, and the degree to which this ability is affected by continuous activity. We found that the synaptic vesicle content of individual boutons belonging to the same axons gradually changed over several hours, and that these changes occurred independently of activity. Intermittent stimulation for 1 h accelerated rates of vesicle pool size change. Interestingly, however, following stimulation cessation, vesicle pool size change rates gradually converged with basal change rates. Over similar time scales, active zones (AZs) exhibited substantial remodeling; yet, unlike synaptic vesicles, AZ remodeling was not affected by the stimulation paradigms used here. These findings indicate that enhanced activity levels can increase synaptic vesicle redistribution among nearby synapses, but also highlight the presence of forces that act to restore particular set points in terms of SV contents, and support a role for active zones in preserving such set points. These findings also indicate, however, that neither AZ size nor SV content set points are particularly stable, questioning the long-term tenacity of presynaptic specializations.