Signaling in small subcellular volumes. II. Stochastic and diffusion effects on synaptic network properties
Signaling in small subcellular volumes. II. Stochastic and diffusion effects on synaptic network properties
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DOI：
10.1529/biophysj.104.040501
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发表时间：
2004-08-01
影响因子：
3.4
通讯作者：
Bhalla, US
中科院分区：
文献类型：
--
作者：
Bhalla, US
突触信号网络能够进行复杂的细胞计算。这些能力包括有选择地对不同的输入模式作出反应的能力，以及在长期内维持反应变化的能力。突触体积小，使信号分析复杂化，因为化学环境受到扩散和随机性的强烈影响。本研究基于先前提出的突触信号电路（Bhalla和Iyengar，1999）的更新版本，并分析了三个网络计算特性：双稳态，阈值和模式选择性。模拟表明，尽管存在双稳态可能持续存在的扩散区域，但小体积的化学噪音压倒了双稳态。在确定性的情况下，网络表现出一个尖锐的阈值之间的过渡较低和较高的稳定状态。当考虑随机性时，这种过渡被加宽，并且在较低和较高状态之间单独运行分区。第三个网络属性，模式选择性，在突触体积严重退化。然而，存在其中类似于随机共振的过程操作并放大模式选择性的机制。这些结果意味着，信号条件的简单缩放到毫微微升体积是不可能的，和微环境，如反应复合物的形成，可能是必不可少的可靠的小体积信号。
The synaptic signaling network is capable of sophisticated cellular computations. These include the ability to respond selectively to different patterns of input, and to sustain changes in response over long periods. The small volume of the synapse complicates the analysis of signaling because the chemical environment is strongly affected by diffusion and stochasticity. This study is based on an updated version of a previously proposed synaptic signaling circuit (Bhalla and Iyengar, 1999) and analyzes three network computation properties in small volumes: bistability, thresholding, and pattern selectivity. Simulations show that although there are diffusive regimes in which bistability may persist, chemical noise at small volumes overwhelms bistability. In the deterministic situation, the network exhibits a sharp threshold for transition between lower and upper stable states. This transition is broadened and individual runs partition between lower and upper states, when stochasticity is considered. The third network property, pattern selectivity, is severely degraded at synaptic volumes. However, there are regimes in which a process similar to stochastic resonance operates and amplifies pattern selectivity. These results imply that simple scaling of signaling conditions to femtoliter volumes is unlikely, and microenvironments, such as reaction complex formation, may be essential for reliable small-volume signaling.