Johnson H, Mossberg K, Arvidsson U, Piehl F, Hökfelt T, Ulfhake B
Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
J Comp Neurol. 1995 Aug 14;359(1):69-89. doi: 10.1002/cne.903590106.
Sprague-Dawley rats develop progressive motor dysfunctions during the third year of life. We use this as a model to examine possible neuronal mechanism(s) that may cause motor impairments occuring during aging. In this study we have used indirect immunofluorescence histochemistry (IF) and in situ hybridization histochemistry (ISH) to study quantitatively and qualitatively the staining pattern and mRNA expression of calcitonin gene-related peptide (alpha-CGRP), growth-associated protein 43 (GAP-43), and acidic fibroblast growth factor (aFGF) in spinal lumbar motoneurons of young adult (2-3 months) and aged (30 months) Sprague-Dawley rats. In addition, mRNAs encoding choline acetyltransferase (ChAT), beta-CGRP, and cholecystokinin (CCK) were analyzed. All aged rats used in this study disclosed symptoms of hindlimb incapacity, ranging from mild weight-bearing insufficiency to paralysis of the hind limbs. The symptoms were confined to the musculature of the hindlimb and hip regions. Only a small number (approximately 15%) of the large motoneurons that innervate the hindlimb muscles were lost in those aged rats that had clinical symptoms of hindlimb motor incapacities. The remaining motoneurons expressed ChAT mRNA at levels similar to those of young adult rats. The vast majority of these motoneurons showed increased mRNA levels for alpha-CGRP and GAP-43. Aged motoneurons contained more CGRP like immunoreactivity (LI), but the number of immunoreactive neurons was smaller than in adult rats. GAP-43-LI could be detected in motoneurons in aged, but not in adult, rats. GAP-43-LI was always colocalized with CGRP-LI in aged motoneurons. Studies of individual aged rats revealed that the increase of GAP-43 mRNA-positive cell bodies occurred in cases with the most severe clinical symptoms, whereas the increase in alpha-CGRP was even evident in rats with mild symptoms. No alterations in content of aFGF-LI or aFGF mRNA could be detected in the aged rat, and the content of CCK and beta-CGRP mRNAs was also normal. The usefulness of this rat model for studies of neuromuscular aging and possible functional roles for GAP-43 and CGRP in plastic and regenerative processes during aging are discussed.
斯普拉格-道利大鼠在生命的第三年会出现进行性运动功能障碍。我们将此作为模型来研究可能导致衰老过程中出现运动障碍的神经元机制。在本研究中，我们使用间接免疫荧光组织化学（IF）和原位杂交组织化学（ISH），对年轻成年（2 - 3个月）和老年（30个月）斯普拉格-道利大鼠腰段脊髓运动神经元中降钙素基因相关肽（α-CGRP）、生长相关蛋白43（GAP-43）和酸性成纤维细胞生长因子（aFGF）的染色模式和mRNA表达进行定量和定性研究。此外，还分析了编码胆碱乙酰转移酶（ChAT）、β-CGRP和胆囊收缩素（CCK）的mRNA。本研究中使用的所有老年大鼠均表现出后肢功能不全的症状，范围从轻度负重不足到后肢瘫痪。症状局限于后肢和臀部区域的肌肉组织。在有后肢运动功能不全临床症状的老年大鼠中，支配后肢肌肉的大型运动神经元仅有少量（约15%）丢失。其余运动神经元表达的ChAT mRNA水平与年轻成年大鼠相似。这些运动神经元中的绝大多数显示α-CGRP和GAP-43的mRNA水平升高。老年运动神经元含有更多的CGRP样免疫反应性（LI），但免疫反应性神经元的数量比成年大鼠少。在老年大鼠的运动神经元中可检测到GAP-43-LI，而成年大鼠中未检测到。在老年运动神经元中，GAP-43-LI总是与CGRP-LI共定位。对个体老年大鼠的研究表明，GAP-43 mRNA阳性细胞体的增加发生在临床症状最严重的病例中，而α-CGRP的增加在症状较轻的大鼠中甚至也很明显。在老年大鼠中未检测到aFGF-LI或aFGF mRNA含量的变化，CCK和β-CGRP mRNA的含量也正常。讨论了该大鼠模型在神经肌肉衰老研究中的实用性以及GAP-43和CGRP在衰老过程中的可塑性和再生过程中可能的功能作用。
