期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：4
页码：1220-1225
DOI：10.1073/pnas.1412996112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceThe activity dynamics of cortical circuits are directly determined by the composing cells and their connections. Inhibitory interneurons are important regulators of neuronal network function. However, how the functional properties of their output synapses relate to the spatial dimension of the network is unknown. Here, we show that perisoma-inhibiting fast-spiking interneurons differentially inhibit close and distant principal cells: inhibitory strength declines and signal duration increases with distance between the presynaptic interneurons and the postsynaptic principal cell. This feature of cortical GABAergic inhibitory signaling supports the interneuron's potential to synchronize large principal cell populations at gamma (>30 Hz) frequencies, a prerequisite for the encoding and storing of information in neuronal networks. GABAergic perisoma-inhibiting fast-spiking interneurons (PIIs) effectively control the activity of large neuron populations by their wide axonal arborizations. It is generally assumed that the output of one PII to its target cells is strong and rapid. Here, we show that, unexpectedly, both strength and time course of PII-mediated perisomatic inhibition change with distance between synaptically connected partners in the rodent hippocampus. Synaptic signals become weaker due to lower contact numbers and decay more slowly with distance, very likely resulting from changes in GABAA receptor subunit composition. When distance-dependent synaptic inhibition is introduced to a rhythmically active neuronal network model, randomly driven principal cell assemblies are strongly synchronized by the PIIs, leading to higher precision in principal cell spike times than in a network with uniform synaptic inhibition.
