Nonrandom local circuits in the dentate gyrus.
Nonrandom local circuits in the dentate gyrus.
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DOI：
10.1523/jneurosci.3612-08.2008
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发表时间：
2008-11-19
期刊：
影响因子：
--
通讯作者：
Strowbridge BW
中科院分区：
文献类型：
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作者：
Larimer P;Strowbridge BW
齿状门在记忆和颞叶癫痫中的潜在作用已被广泛研究。然而，对于该区域两种主要细胞类型（谷氨酸苔藓细胞和门门中间神经元）之间形成的突触，以及涉及这些细胞的局部回路的组织，我们知之甚少。通过对大鼠海马切片的三次和四次同步细胞内记录，我们发现苔藓细胞以高失败率唤起EPSPs到门级神经元。苔藓细胞表现出深刻的突触特异性；87.5%的层间连接位于门端中间神经元上。门门间神经元也表现出突触特异性，并优先抑制苔藓细胞；81%的抑制性门突触位于苔藓细胞上。Hilar ipsp失败率低，被GABAA受体拮抗剂gabazine阻断，在17hz下测试时表现出短期抑制。令人惊讶的是，我们在中间神经元上发现的苔藓细胞突触中，超过一半（57%）是相互兴奋/抑制局部电路基序的一部分。无论是高度的靶细胞特异性，还是结构多突触局部电路基序的显著富集，都不能用非随机抽样或体细胞接近来解释。层间门部突触似乎主要通过整合同步输入和突触前突发放电来发挥作用，从而使门部细胞能够在大的动态范围内响应输入强度。我们发现在脑门部富集的相互苔藓细胞/中间神经元局部电路基序可能产生参与海马记忆操作的稀疏神经表征。
The dentate hilus has been extensively studied in relation to its potential role in memory and in temporal lobe epilepsy. Little is known, however, about the synapses formed between the two major cell types in this region, glutamatergic mossy cells and hilar interneurons, or the organization of local circuits involving these cells. Using triple and quadruple simultaneous intracellular recordings in rat hippocampal slices, we find that mossy cells evoke EPSPs with high failure rates onto hilar neurons. Mossy cells show profound synapse specificity; 87.5% of their intralamellar connections are onto hilar interneurons. Hilar interneurons also show synapse specificity and preferentially inhibit mossy cells; 81% of inhibitory hilar synapses are onto mossy cells. Hilar IPSPs have low failure rates, are blocked by the GABAA receptor antagonist gabazine, and exhibit short-term depression when tested at 17 Hz. Surprisingly, more than half (57%) of the mossy cell synapses we found onto interneurons were part of reciprocal excitatory/inhibitory local circuit motifs. Neither the high degree of target cell specificity, nor the significant enrichment of structured polysynaptic local circuit motifs, could be explained by nonrandom sampling or somatic proximity. Intralamellar hilar synapses appear to function primarily by integrating synchronous inputs and presynaptic burst discharges, allowing hilar cells to respond over a large dynamic range of input strengths. The reciprocal mossy cell/interneuron local circuit motifs we find enriched in the hilus may generate sparse neural representations involved in hippocampal memory operations.