Parallel activation of field CA2 and dentate gyrus by synaptically elicited perforant path volleys
Parallel activation of field CA2 and dentate gyrus by synaptically elicited perforant path volleys
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DOI：
10.1002/hipo.20011
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发表时间：
2004-01-01
期刊：
影响因子：
3.5
通讯作者：
Gessi, T
中科院分区：
文献类型：
--
作者：
Bartesaghi, R;Gessi, T
以往的研究表明，背侧Psalterium(PSD)向内嗅皮层(ENT)的抽动激活了投射到齿状回的第II层穿通神经元。在第二层神经元放电之后，依次激活齿状回(DG)、CA3区、CA1区。本研究的目的是确定在这个实验模型中，CA2这个被忽视的部分是否被穿透路径抽射直接和/或间接地被反复的海马投射所激活。在麻醉豚鼠耳鼻喉区、DG区、CA2区、CA1区和CA3区记录了单次电击刺激PSD诱发的场电位。使用电流源密度分析来定位输入/S到场CA2。结果表明，在CA2视野中，早期群体尖峰叠加在慢波(早期反应)上，而较晚较小的群体尖峰叠加在慢波(晚反应)上。在CA2反应早期的CSD分析表明，在腔隙分子层有一个电流汇，随后有一个汇从放射层移动到锥体层，这表明这一反应代表了CA2锥体神经元的激活和放电，它是由通向该区域的通路纤维介导的。晚期反应的CSD分析显示，在CA2中层放射层有一个电流汇，随后有一个汇从内层放射层移动到锥体层，这表明这种反应是由CA3区的Schaffer侧支介导的。在CA3中没有出现早期的种群高峰。然而，在CA3的腔隙分子层诱发了一个小幅度的早期电流下沉，这表明存在由穿通径纤维介导的突触电流。这些结果提供了有关穿通通路系统的新信息，表明背侧Psalterium向内嗅皮层发出刺激的穿通通路神经元，引起颗粒细胞和CA2锥体神经元的平行放电和去极化，但不引起CA3锥体神经元的放电。因此，CA2野可以与DG-CA3-CA1系统并行地介导ENT信号到海马和海马外结构的直接传输，并且可以在后者被破坏的情况下提供安全因素。(C)2004年Wiley-Liss公司
Previous studies showed that dorsal psalterium (PSD) volleys to the entorhinal cortex (ENT) activated in layer II perforant path neurons projecting to the dentate gyrus. The discharge of layer II neurons was followed by the sequential activation of the dentate gyrus (DG), field CA3, field CA1. The aim of the present study was to ascertain whether in this experimental model field, CA2, a largely ignored sector, is activated either directly by perforant path volleys and/or indirectly by recurrent hippocampal projections. Field potentials evoked by single-shock PSD stimulation were recorded in anesthetized guinea pigs from ENT, DG, fields CA2, CA1, and CA3. Current source-density (CSD) analysis was used to localize the input/s to field CA2. The results showed the presence in field CA2 of an early population spike superimposed on a slow wave (early response) and of a late and smaller population spike, superimposed on a slow wave (late response). CSD analysis during the early CA2 response showed a current sink in stratum lacunosum-moleculare, followed by a sink moving from stratum radiatum to stratum pyramidale, suggesting that this response represented the activation and discharge of CA2 pyramidal neurons, mediated by perforant path fibers to this field. CSD analysis during the late response showed a current sink in middle stratum radiatum of CA2 followed by a sink moving from inner stratum radiatum to stratum pyramidale, suggesting that this response was mediated by Schaffer collaterals from field CA3. No early population spike was evoked in CA3. However, an early current sink of small magnitude was evoked in stratum lacunosum-moleculare of CA3, suggesting the presence of synaptic currents mediated by perforant path fibers to this field. The results provide novel information about the perforant path system, by showing that dorsal psalterium volleys to the entorhinal cortex activate perforant path neurons that evoke the parallel discharge of granule cells and CA2 pyramidal neurons and depolarization, but no discharge of CA3 pyramidal neurons. Consequently, field CA2 may mediate the direct transfer of ENT signals to hippocampal and extrahippocampal structures in parallel with the DG-CA3-CA1 system and may provide a security factor in situations in which the latter is disrupted. (C) 2004 Wiley-Liss, Inc.