Crutcher K A, Marfurt C F
Department of Anatomy, University of Utah School of Medicine, Salt Lake City.
J Neurosci. 1988 Jul;8(7):2289-302. doi: 10.1523/JNEUROSCI.08-07-02289.1988.
Damage to septohippocampal neurons in the adult rat results in sprouting of sympathetic axons into the denervated hippocampal formation. However, the distribution of sympathohippocampal fibers has only been assessed with light microscopic techniques, and it is not known if the sprouted fibers leave the blood vessels, along which they migrate into the hippocampal formation, to enter the hippocampal neuropil and, if they do, whether they form synaptic contacts with central neurons. Using the tetramethylbenzidine technique to visualize anterogradely transported wheat germ agglutinin-horseradish peroxidase conjugate, we identified sprouted sympathetic fibers in the hippocampal formation at both the light and electron microscopic level in albino rats receiving medial septal lesions. The majority of labeled fibers were observed within the regions immediately above and below the granule cell layer. Although most of the labeled sprouts were observed in association with intraparenchymal blood vessels, where they were usually apposed to the basal lamina, approximately a third of the labeled profiles were present within the neuropil with no obvious vascular relationships. Most of the profiles were identified as unmyelinated axons or vesicle-filled varicosities. Many of the latter structures contained small dense-cored vesicles, but in our sample none of the labeled profiles were observed to form membrane specializations with adjacent structures, and many were partly surrounded by presumed astrocytic processes. These results document the invasion of the CNS by sprouting axons of peripheral origin indicating that axonal elongation from uninjured neurons can occur within the mature mammalian CNS under certain circumstances. In addition, the presence of significant numbers of sympathetic fibers within the hippocampal neuropil indicates that they may be in a strategic position to influence hippocampal function.
成年大鼠中隔海马神经元受损会导致交感神经轴突发芽并长入去神经支配的海马结构。然而，交感海马纤维的分布仅通过光学显微镜技术进行了评估，目前尚不清楚发芽的纤维是否离开它们沿其迁移进入海马结构的血管，进入海马神经毡，以及如果它们这样做了，它们是否与中枢神经元形成突触联系。使用四甲基联苯胺技术来可视化顺行运输的小麦胚芽凝集素 - 辣根过氧化物酶复合物，我们在接受内侧中隔损伤的白化大鼠的海马结构中，在光学显微镜和电子显微镜水平上都鉴定出了发芽的交感纤维。大多数标记纤维出现在颗粒细胞层上方和下方的区域内。虽然大多数标记的芽与实质内血管相关，它们通常与基膜相邻，但大约三分之一的标记轮廓存在于神经毡内，没有明显的血管关系。大多数轮廓被鉴定为无髓轴突或充满囊泡的曲张体。许多后者结构含有小的致密核心囊泡，但在我们的样本中，没有观察到任何标记轮廓与相邻结构形成膜特化，并且许多部分被推测的星形胶质细胞过程包围。这些结果证明了外周起源的发芽轴突对中枢神经系统的侵入，表明在某些情况下，未受损神经元的轴突伸长可以在成熟的哺乳动物中枢神经系统内发生。此外，海马神经毡内存在大量交感纤维表明它们可能处于影响海马功能的关键位置。
