Peterson G M
Department of Anatomy and Cell Biology, East Carolina University School of Medicine, Greenville, North Carolina 27858-4354.
Hippocampus. 1994 Dec;4(6):635-48. doi: 10.1002/hipo.450040603.
Virtually all of the afferents to the hippocampal formation undergo collateral sprouting after removal of adjacent afferent systems. However, the central noradrenergic (NA) afferents, which demonstrate a remarkable propensity for regeneration and sprouting in other regions of the brain, have not been found to sprout in the denervated hippocampal formation. The present study was designed to determine if the pattern of innervation by NA fibers in the dentate gyrus of adult rats can be altered by interruption of the other major afferents. The innervation pattern of NA fibers was examined in the dentate gyrus 4 weeks after removal of the ipsilateral and/or contralateral entorhinal afferents and/or transection of the fimbria-fornix and supracallosal stria. The noradrenergic identity of the fibers was indicated by immunoreactivity for dopamine beta hydroxylase (DBH) and peripheral sympathetic fibers were demonstrated by immunoreactivity for nerve growth factor receptor (NGFr), which did not stain cholinergic fibers in this application. In control brains, the noradrenergic innervation of the dentate molecular layer was light and uniform across the width of the layer. Transection of the perforant path (ipsilateral entorhinal afferents) or ventral hippocampal commissure (contralateral entorhinal afferents) resulted in a significant increase in innervation density in the outer half of the molecular layer, and the combination of these two lesions produced the greatest increase. In those brains with transection of the ipsilateral and contralateral entorhinal afferents, the denervated dentate gyrus had a nearly twofold increase in density of DBH-immunoreactive fibers within the outer half of the molecular layer. These fibers tended to course parallel to the pial surface rather that perpendicular as in control sections. Transection of the fimbria-fornix alone had no affect on the innervation pattern of DBH-ir fibers in the molecular layer. When the fimbria-fornix was transected in combination with both of the other lesions, an overall increase in innervation density occurred, but there was no further increase in the difference between the inner and outer halves of the molecular layer. No NGFr-immunoreactive fibers were observed in the molecular layer in any of the brains, indicating that the DBH-immunoreactive fibers in this region were not of peripheral origin. It is concluded that removal of the ipsi- and contralateral entorhinal afferents to the dentate gyrus results in the sprouting of central NA fibers in the outer half of the molecular layer.
实际上，在去除相邻传入系统后，海马结构的几乎所有传入纤维都会发生侧支发芽。然而，中枢去甲肾上腺素能（NA）传入纤维在大脑其他区域表现出显著的再生和发芽倾向，但在去神经支配的海马结构中尚未发现其发芽。本研究旨在确定成年大鼠齿状回中NA纤维的支配模式是否会因其他主要传入纤维的中断而改变。在去除同侧和/或对侧内嗅传入纤维和/或切断穹窿-海马伞和胼胝体上缘纤维4周后，检查齿状回中NA纤维的支配模式。通过多巴胺β羟化酶（DBH）免疫反应性表明纤维的去甲肾上腺素能特性，通过神经生长因子受体（NGFr）免疫反应性显示外周交感神经纤维，在此应用中该受体不标记胆碱能纤维。在对照脑中，齿状分子层的去甲肾上腺素能支配较轻且在层宽上均匀分布。切断穿通通路（同侧内嗅传入纤维）或腹侧海马连合（对侧内嗅传入纤维）导致分子层外半部分的支配密度显著增加，这两种损伤的联合作用产生的增加最大。在那些同侧和对侧内嗅传入纤维均被切断的脑中，去神经支配的齿状回分子层外半部分DBH免疫反应性纤维的密度增加了近两倍。这些纤维倾向于与软脑膜表面平行走行，而不像对照切片中那样垂直走行。单独切断穹窿-海马伞对分子层中DBH免疫反应性纤维的支配模式没有影响。当穹窿-海马伞与其他两种损伤联合切断时，支配密度总体增加，但分子层内半部分和外半部分之间的差异没有进一步增加。在任何脑中的分子层均未观察到NGFr免疫反应性纤维，表明该区域的DBH免疫反应性纤维不是外周起源的。结论是，去除齿状回的同侧和对侧内嗅传入纤维会导致分子层外半部分的中枢NA纤维发芽。
