State Key Lab for Brain and Cognitive Sciences, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China 100101.
Mol Brain. 2012 Aug 1;5:26. doi: 10.1186/1756-6606-5-26.
Action potentials at the neurons and graded signals at the synapses are primary codes in the brain. In terms of their functional interaction, the studies were focused on the influence of presynaptic spike patterns on synaptic activities. How the synapse dynamics quantitatively regulates the encoding of postsynaptic digital spikes remains unclear. We investigated this question at unitary glutamatergic synapses on cortical GABAergic neurons, especially the quantitative influences of release probability on synapse dynamics and neuronal encoding. Glutamate release probability and synaptic strength are proportionally upregulated by presynaptic sequential spikes. The upregulation of release probability and the efficiency of probability-driven synaptic facilitation are strengthened by elevating presynaptic spike frequency and Ca2+. The upregulation of release probability improves spike capacity and timing precision at postsynaptic neuron. These results suggest that the upregulation of presynaptic glutamate release facilitates a conversion of synaptic analogue signals into digital spikes in postsynaptic neurons, i.e., a functional compatibility between presynaptic and postsynaptic partners.
动作电位在神经元和突触的分级信号是大脑中的主要代码。就其功能相互作用而言，研究集中在突触前尖峰模式对突触活动的影响上。突触动力学如何定量调节突触后数字尖峰的编码仍不清楚。我们在皮质 GABA 能神经元的单位谷氨酸能突触上研究了这个问题，特别是释放概率对突触动力学和神经元编码的定量影响。谷氨酸释放概率和突触强度与突触前顺序尖峰成比例上调。通过提高突触前尖峰频率和 Ca2+，可以增强释放概率的上调和概率驱动的突触易化的效率。释放概率的上调提高了突触后神经元的尖峰容量和时间精度。这些结果表明，突触前谷氨酸释放的上调有助于将突触模拟信号转换为突触后神经元中的数字尖峰，即在突触前和突触后伙伴之间存在功能兼容性。
