Legendre D I, Vietje B P, Wells J
Department of Anatomy and Neurobiology, University of Vermont, Burlington.
J Neurotrauma. 1994 Jun;11(3):333-44. doi: 10.1089/neu.1994.11.333.
The present experiments determined whether traumatic lesions of the dentate gyrus granule cells had a different effect on the afferents in the molecular layer (ML) than nontraumatic lesions. Nontraumatic lesions of the granule cells induced by colchicine, ibotenic acid, x-radiation, and adrenalectomy have been reported to reduce both the acetylcholinesterase (AChE)-positive fibers and entorhinal afferents in the ML. After the nontraumatic granule cell lesions, the laminar distribution of the entorhinal afferents was maintained in the ML, whereas the AChE laminar pattern was lost. In the present study, dentate granule cells were traumatically lesioned by a fluid injection into the infragranular cleavage plane (IGCP) of the dentate gyrus. The traumatic lesion resulted in an altered distribution of the afferents in the ML. The perforant path fibers, shown by injection of wheat germ agglutinin horseradish peroxidase into the entorhinal cortex, occupied a greater proportion of the ML in lesioned animals than in control animals. The normal laminar pattern of AChE-positive afferents was not present after the granule cell lesion. There was an initial increase in AChE-positive fibers in the ML that lasted several weeks but eventually returned to near normal levels. The altered distribution of afferents could in part be due to uneven shrinkage of the molecular layer and/or sprouting of the afferents. Granule cell suspension transplants into the IGCP also traumatically lesioned the host granule cells but immediately replaced the damaged host granule cells with immature granule cells. The distribution of afferents was similar to that found in lesioned-only animals. The traumatic lesion induced MAP2 immunoreactivity in the anisomorphic reactive astrocytes of the ML. At the longer survival times, MAP2 was not seen in either the astrocytes of the ML or in the isomorphic reactive astrocytes in CA3.
本实验确定了齿状回颗粒细胞的创伤性损伤对分子层（ML）传入纤维的影响是否与非创伤性损伤不同。据报道，秋水仙碱、鹅膏蕈氨酸、X射线辐射和肾上腺切除术诱导的颗粒细胞非创伤性损伤会减少ML中乙酰胆碱酯酶（AChE）阳性纤维和内嗅传入纤维。非创伤性颗粒细胞损伤后，ML中内嗅传入纤维的分层分布得以维持，而AChE的分层模式则消失。在本研究中，通过向齿状回颗粒下裂平面（IGCP）注射液体对齿状颗粒细胞造成创伤性损伤。创伤性损伤导致ML中传入纤维的分布发生改变。通过将小麦胚芽凝集素辣根过氧化物酶注入内嗅皮质显示，穿通通路纤维在损伤动物的ML中所占比例比对照动物更大。颗粒细胞损伤后，AChE阳性传入纤维的正常分层模式不存在。ML中AChE阳性纤维最初会增加，持续数周，但最终会恢复到接近正常水平。传入纤维分布的改变部分可能是由于分子层不均匀收缩和/或传入纤维的发芽。将颗粒细胞悬液移植到IGCP也会对宿主颗粒细胞造成创伤性损伤，但会立即用未成熟颗粒细胞取代受损的宿主颗粒细胞。传入纤维的分布与仅损伤动物中的分布相似。创伤性损伤在ML的异形反应性星形胶质细胞中诱导了MAP2免疫反应性。在更长的存活时间里，ML的星形胶质细胞或CA3的同形反应性星形胶质细胞中均未观察到MAP2。
