Wenzel H J, Buckmaster P S, Anderson N L, Wenzel M E, Schwartzkroin P A
Department of Neurological Surgery, University of Washington, Seattle 98195-6470, USA.
Hippocampus. 1997;7(5):559-70. doi: 10.1002/(SICI)1098-1063(1997)7:5<559::AID-HIPO11>3.0.CO;2-#.
Electrophysiologically identified and intracellularly biocytin-labeled mossy cells in the dentate hilus of the rat were studied using electron microscopy and postembedding immunogold techniques. Ultrathin sections containing a labeled mossy cell or its axon collaterals were reacted with antisera against the excitatory neurotransmitter glutamate and against the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). From single- and double-immunolabeled preparations, we found that 1) mossy cell axon terminals made asymmetric contacts onto postsynaptic targets in the hilus and stratum moleculare of the dentate gyrus and showed immunoreactivity primarily for glutamate, but never for GABA; 2) in the hilus, glutamate-positive mossy cell axon terminals targeted GABA-positive dendritic shafts of hilar interneurons and GABA-negative dendritic spines; and 3) in the inner molecular layer, the mossy cell axon formed asymmetric synapses with dendritic spines associated with GABA-negative (presumably granule cell) dendrites. The results of this study support the view that excitatory (glutamatergic) mossy cell terminals contact GABAergic interneurons and non-GABAergic neurons in the hilar region and GABA-negative granule cells in the stratum moleculare. This pattern of connectivity is consistent with the hypothesis that mossy cells provide excitatory feedback to granule cells in a dentate gyrus associational network and also activate local hilar inhibitory elements.
利用电子显微镜和包埋后免疫金技术，对大鼠齿状回门区经电生理鉴定并进行细胞内生物素标记的苔藓细胞进行了研究。含有标记苔藓细胞或其轴突侧支的超薄切片与抗兴奋性神经递质谷氨酸和抗抑制性神经递质γ-氨基丁酸（GABA）的抗血清反应。从单免疫标记和双免疫标记标本中，我们发现：1）苔藓细胞轴突终末在齿状回门区和分子层与突触后靶点形成不对称突触，主要显示谷氨酸免疫反应性，而从不显示GABA免疫反应性；2）在门区，谷氨酸阳性的苔藓细胞轴突终末靶向门区内神经元的GABA阳性树突干和GABA阴性树突棘；3）在分子内层，苔藓细胞轴突与与GABA阴性（推测为颗粒细胞）树突相关的树突棘形成不对称突触。本研究结果支持这样一种观点，即兴奋性（谷氨酸能）苔藓细胞终末在门区与GABA能中间神经元和非GABA能神经元以及分子层的GABA阴性颗粒细胞接触。这种连接模式与苔藓细胞在齿状回联合网络中为颗粒细胞提供兴奋性反馈并激活局部门区抑制性元件的假说一致。
