Svensson M, Aldskogius H
Department of Anatomy, Karolinska Institutet, Stockholm, Sweden.
Exp Neurol. 1993 Mar;120(1):123-31. doi: 10.1006/exnr.1993.1046.
The purpose of the present study was to examine the possible role of reactive microglia in the removal of presynaptic terminals following motor axon injury. Quantitative electron microscopy was used to examine synaptic numbers and total relative synaptic coverage on hypoglossal neuronal perikarya following hypoglossal nerve transection in the rat with or without pharmacological blockade of the axotomy-induced microglial cell proliferation. In a previous study we have shown that the axotomy-induced microglial cell proliferation is selectively inhibited by continuous infusion of cytosine-arabinoside (ARA-C) into the ventricular system of the adult rat brain. Adopting this procedure in the present study resulted in an almost complete elimination of reactive microglia. There was a statistically significant decrease in the number of synapses and the relative synaptic coverage in untreated as well as ARA-C-treated animals 4 and 7 days after nerve transection. Immunocytochemical labeling of terminals in the hypoglossal nucleus using antibodies to synaptophysin showed a reduction in immunoreactivity around hypoglossal nerve cell bodies ipsilateral to nerve transection in both groups of animals. These results indicate that reactive microglia are not responsible for detachment of presynaptic terminals following motor axon injury.
本研究的目的是探讨反应性小胶质细胞在运动轴突损伤后清除突触前终末过程中可能发挥的作用。运用定量电子显微镜技术，对大鼠舌下神经横断后，在有或没有药物阻断轴突切断诱导的小胶质细胞增殖的情况下，舌下神经元胞体上的突触数量和总相对突触覆盖率进行检测。在先前的一项研究中我们已经表明，通过向成年大鼠脑室内持续注入阿糖胞苷（ARA-C），可选择性抑制轴突切断诱导的小胶质细胞增殖。在本研究中采用该方法导致反应性小胶质细胞几乎完全清除。在神经横断后4天和7天，未处理组以及ARA-C处理组动物的突触数量和相对突触覆盖率均出现统计学上的显著下降。使用抗突触素抗体对舌下神经核内的终末进行免疫细胞化学标记显示，两组动物中，神经横断同侧舌下神经细胞体周围的免疫反应性均降低。这些结果表明，反应性小胶质细胞并非运动轴突损伤后突触前终末脱离的原因。
