Neuronal Hyperactivity Sustains the Basal Dendrites of Immature Dentate Granule Cells: Time-Lapse Confocal Analysis Using Hippocampal Slice Cultures
Neuronal Hyperactivity Sustains the Basal Dendrites of Immature Dentate Granule Cells: Time-Lapse Confocal Analysis Using Hippocampal Slice Cultures
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DOI：
10.1002/hipo.20529
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发表时间：
2009-01-01
期刊：
影响因子：
3.5
通讯作者：
Koyama, Ryuta
中科院分区：
文献类型：
--
作者：
Nakahara, Soichiro;Tamura, Makoto;Koyama, Ryuta
树突的形态发生是建立正确的神经回路的一个重要过程。在癫痫海马中，成熟的齿状颗粒细胞（GC）具有基底树突（BD），这是异常的，并被认为有助于癫痫发作的进展。然而，有一个直接的时间推移的证据表明，神经元过度活跃调节GC的树突发育缺乏。在本研究中，我们对从出生后6天（P6）大鼠制备的海马切片培养物中GC的树枝状形态发生进行了延时共聚焦分析。在体外培养第5天电穿孔膜靶向的绿色荧光蛋白，我们发现大多数Prox 1阳性和钙结合蛋白阴性的未成熟GC在第7天具有几个BD和富含丝状伪足的顶端树突。在7 ~ 9 DIV时，BD逐渐消失，14 DIV时全部消失。然而，当GABA（A）受体拮抗剂印防己毒素长期应用于诱导培养物中的癫痫条件时，大多数BD未能从7至9 DIV缩回。这些作用被共同应用河豚毒素，钠通道阻滞剂，从而使我们相信，神经元过度活跃有助于维持BD。此外，在印防己毒素处理的培养物中，即使在14 DIV后，大多数GC也持续表现出几个BD。与此相反，无论是逐步修剪的丝状伪足，也没有分支动态的顶端树突在培养期间受到印防己毒素。这些结果首次为我们提供了直接证据，表明神经元过度活跃有助于预先存在的BD的稳定性。(C)2008 Wiley-Liss，Inc.
Dendritic morphogenesis is an essential process for the establishment of proper neural circuitry. In the epileptic hippocampus, mature dentate granule cells (GCs) possess basal dendrites (BDs), which is abnormal and is assumed to contribute to seizure progression. However, there is a lack of direct time-lapse evidence showing that neuronal hyperactivity regulates the dendritic development of GCs. in the present study, we carried out time-lapse confocal analysis of the dendritic morphogenesis of GCs in hippocampal slice cultures that were prepared from postnatal 6-day-old (P6) rats. By electroporating membrane-targeted green fluorescent protein at 5 days in vitro (DIV), we found that most of the Prox1-positive and calbindin-negative immature GCs possessed several BDs and filopodia-rich apical dendrites at 7 DIV. BDs were gradually eliminated from 7 to 9 DIV, and they completely vanished at 14 DIV in all the GCs examined. However, most BDs failed to retract from 7 to 9 DIV, when the GABA(A) receptor antagonist picrotoxin was chronically applied to induce epileptic conditions in the cultures. These effects were blocked by coapplying tetrodotoxin, a sodium channel blocker, thus convincing us that neuronal hyperactivity contributes to the maintenance of BDs. Further, in the picrotoxin-treated cultures, most of the GCs persistently exhibited several BDs even after 14 DIV. In contrast, neither the progressive pruning of the filopodia nor the branch dynamics of the apical dendrites during the culture periods was affected by picrotoxin. These results, for the first time, provide us with direct evidence that neuronal hyperactivity contributes to the stability of pre-existing BDs. (C) 2008 Wiley-Liss, Inc.