Borke R C, Curtis M, Ginsberg C
Department of Anatomy and Cell Biology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814.
J Neurocytol. 1993 Mar;22(3):141-53. doi: 10.1007/BF01246353.
This study examined changes in choline acetyltransferase and calcitonin gene-related peptide immunoreactivity in hypoglossal motoneurons of rats at 1, 3, 7, 20 and 50 days after three types of nerve injury: crush, transection and resection. Peripheral reinnervation was assayed by retrograde labelling of the motoneurons after injections of the exogenous protein, horseradish peroxidase, into the tongue. Maximal reduction in choline acetyltransferase immunostaining occurred at seven days after nerve damage and the amount of the decrease was related to the nature of the injury. The recovery of choline acetyltransferase to normal levels was related to the timing of reinnervation after nerve crush, but not after transection or resection injuries. In contrast to these findings, a rapid increase in calcitonin gene-related peptide immunoreactivity preceded the decrease in choline acetyltransferase levels. A striking increase in calcitonin gene-related peptide immunoreactivity was observed at one day postoperative and was maximal at three days postoperatively for all injuries. Later changes in calcitonin gene-related peptide levels were dependent on the type injury. Increased calcitonin gene-related peptide staining persisted to 20 days after nerve crush. After nerve transection or resection, calcitonin gene-related peptide immunoreactivity decreased to basal levels at seven days postoperatively. This declination was followed by a second rise in calcitonin gene-related peptide immunolabeling at 20 days for nerve transection or 50 days after resection. Nearly complete reinnervation was established by 20 days after nerve crush. At 50 days after transection, less than half the number of normally-labelled neurons contained horseradish peroxidase. At this time only 1% of those whose axons had been resected were labelled. These observations suggest that different mechanisms regulate the responses of choline acetyltransferase and calcitonin gene-related peptide to nerve injury. The present results indicate that choline acetyltransferase levels in motoneurons can not be used to predict either the likelihood of or the timing of reinnervation after nerve transection or resection. However, our results strengthen the premise that an increased of calcitonin gene-related peptide immunoreactivity serves as a reliable index for predicting nerve regeneration/reinnervation after cranial nerve injury.
本研究检测了三种神经损伤（挤压、横断和切除）后1、3、7、20和50天大鼠舌下运动神经元中胆碱乙酰转移酶和降钙素基因相关肽免疫反应性的变化。通过将外源性蛋白质辣根过氧化物酶注射到舌内后对运动神经元进行逆行标记来检测外周神经再支配情况。胆碱乙酰转移酶免疫染色的最大减少发生在神经损伤后7天，减少量与损伤性质有关。神经挤压后胆碱乙酰转移酶恢复到正常水平与再支配时间有关，但横断或切除损伤后则无关。与这些发现相反，降钙素基因相关肽免疫反应性在胆碱乙酰转移酶水平降低之前迅速增加。术后1天观察到降钙素基因相关肽免疫反应性显著增加，所有损伤在术后3天达到最大值。降钙素基因相关肽水平的后期变化取决于损伤类型。神经挤压后降钙素基因相关肽染色增加持续到20天。神经横断或切除后，降钙素基因相关肽免疫反应性在术后7天降至基础水平。这种下降之后，神经横断后20天或切除后50天降钙素基因相关肽免疫标记出现第二次升高。神经挤压后20天几乎建立了完全的神经再支配。横断后50天，正常标记的神经元中含有辣根过氧化物酶的数量不到一半。此时，轴突被切除的神经元中只有1%被标记。这些观察结果表明，不同的机制调节胆碱乙酰转移酶和降钙素基因相关肽对神经损伤的反应。目前的结果表明，运动神经元中的胆碱乙酰转移酶水平不能用于预测神经横断或切除后再支配的可能性或时间。然而，我们的结果强化了这样一个前提，即降钙素基因相关肽免疫反应性的增加是预测颅神经损伤后神经再生/再支配的可靠指标。
