Axon arbors and synaptic connections of a vulnerable population of interneurons in the dentate gyrus in vivo
Axon arbors and synaptic connections of a vulnerable population of interneurons in the dentate gyrus in vivo
复制标题
DOI：
10.1002/cne.10183
复制
发表时间：
2002-04-15
影响因子：
2.5
通讯作者：
Zhang, GF
中科院分区：
文献类型：
--
作者：
Buckmaster, PS;Yamawaki, R;Zhang, GF
齿状回门部的主要GABA能神经元类。由刺状生长抑素能中间神经元组成。我们在沙土鼠体内观察了用生物细胞素标记的有刺的肺门中间神经元的轴突投射和突触连接。轴突长度152~497 mm/个神经元。60%~85%的轴突集中在齿状回分子层的外三分之二。轴索的间隔跨度超过海马体总长度的48-82%，远远超过颗粒细胞轴突的间隔跨度，后者的完整轴突跨度超过15%-29%。在分子层的外1/3处，一个长达216微米的带刺的肺门间神经元轴突片段被三维重建，平均每5.1微米形成1个突触。在重建的节段形成的42个对称(抑制性)突触中，88%的突触带有推测为颗粒细胞的刺状树突，67%的突触带有树突棘，树突棘也接受来自未标记轴突终末的不对称(兴奋)接触。包埋后的GABA免疫细胞化学显示，分子层外1/3处的GABA能突触中有55%有棘突。因此，在外部分子层，刺状的肺门中间神经元形成突触接触，这些突触的位置似乎是为了在从内嗅觉皮质到颗粒细胞树突棘的兴奋性突触输入位置附近施加抑制控制。这些发现证明了单个中间神经元的深远而高度特异的连接，并表明像在颞叶癫痫中所发生的那样，肺门棘中间神经元的丢失可能导致海马区的过度兴奋。(C)2002年Wiley-Liss，Inc.
The predominant gamma-aminobutyric acid (GABA)ergic neuron class in the hilus of the dentate gyrus. consists of spiny somatostatinergic interneurons. We examined the axon projections and synaptic connections made by spiny hilar interneurons labeled with biocytin in gerbils in vivo. Axon length was 152-497 mm/neuron. Sixty to 85% of the axon concentrated in the outer two thirds of the molecular layer of the dentate gyrus. The septotemporal span of the axon arbor extended over 48-82% of the total hippocampal length, which far exceeds the septotemporal span of axons of granule cells whose complete axon arbors extended over 15-29%. A three-dimensionally reconstructed 216-mum-long spiny hilar interneuron axon segment in the outer third of the molecular layer formed an average of 1 synapse every 5.1 mum. Of the 42 symmetric (inhibitory) synapses formed by the reconstructed segment, 88% were with spiny dendrites of presumed granule cells, and 67% were with dendritic spines that also receive an asymmetric (excitatory) contact from an unlabeled axon terminal. Postembedding GABA-immunocytochemistry revealed that 55% of the GABAergic synapses in the outer third of the molecular layer were with spines. Therefore, in the outer molecular layer, spiny hilar interneurons form synaptic contacts that appear to be positioned to exert inhibitory control near sites of excitatory synaptic input from the entorhinal cortex to granule cell dendritic spines. These findings demonstrate far-reaching, yet highly specific, connectivity of individual interneurons and suggest that the loss of spiny hilar interneurons, as occurs in temporal lobe epilepsy, may contribute to hyperexcitability in the hippocampus. (C) 2002 Wiley-Liss, Inc.