Deschenes M R, Kressin K A, Garratt R N, Leathrum C M, Shaffrey E C
Department of Kinesiology & Health Sciences, College of William & Mary, Williamsburg, VA 23187-8795, USA; Program in Neuroscience, College of William & Mary, Williamsburg, VA 23187-8795, USA.
Program in Neuroscience, College of William & Mary, Williamsburg, VA 23187-8795, USA.
Neuroscience. 2016 Mar 1;316:167-77. doi: 10.1016/j.neuroscience.2015.12.004. Epub 2015 Dec 19.
The objective of this study was to determine whether pre- to post-synaptic coupling of the neuromuscular junction (NMJ) could be maintained in the face of significant morphological remodeling brought about by exercise training, and whether aging altered this capacity. Eighteen young adult (8 mo) and eighteen aged (24 mo) Fischer 344 rats were randomly assigned to either endurance trained (treadmill running) or untrained control conditions resulting in four groups (N=9/group). After the 10-week intervention rats were euthanized and hindlimb muscles were surgically removed, quickly frozen at approximate resting length and stored at -85°C. The plantaris and EDL muscles were selected for study as they have different functions (ankle extensor and ankle flexor, respectively) but both are similarly and overwhelmingly comprised of fast-twitch myofibers. NMJs were stained with immunofluorescent procedures and images were collected with confocal microscopy. Each variable of interest was analyzed with a 2-way ANOVA with main effects of age and endurance training; in all cases significance was set at P⩽0.05. Results showed that no main effects of aging were detected in NMJs of either the plantaris or the EDL. Similarly, endurance training failed to alter any synaptic parameters of EDL muscles. The same exercise stimulus in the plantaris however, resulted in significant pre- and post-synaptic remodeling, but without altering pre- to post-synaptic coupling of the NMJs. Myofiber profiles of the same plantaris and EDL muscles were also analyzed. Unlike NMJs, myofibers displayed significant age-related atrophy in both the plantaris and EDL muscles. Overall, these results confirm that despite significant training-induced reconfiguration of NMJs, pre- to post-synaptic coupling remains intact underscoring the importance of maintaining proper apposition of neurotransmitter release and binding sites so that effective nerve to muscle communication is assured.
本研究的目的是确定在运动训练引起显著形态重塑的情况下，神经肌肉接头（NMJ）的突触前到突触后耦合是否能够维持，以及衰老是否会改变这种能力。将18只年轻成年（8个月）和18只老年（24个月）的Fischer 344大鼠随机分为耐力训练组（跑步机跑步）或未训练对照组，从而形成四组（每组N = 9）。经过10周的干预后，对大鼠实施安乐死并手术切除后肢肌肉，以近似静息长度快速冷冻并储存在-85°C。选择比目鱼肌和趾长伸肌进行研究，因为它们具有不同的功能（分别为踝关节伸肌和踝关节屈肌），但两者都同样主要由快肌纤维组成。用免疫荧光程序对神经肌肉接头进行染色，并用共聚焦显微镜收集图像。用双向方差分析对每个感兴趣的变量进行分析，年龄和耐力训练为主要效应因素；在所有情况下，显著性设定为P⩽0.05。结果表明，在比目鱼肌或趾长伸肌的神经肌肉接头中均未检测到衰老的主要效应。同样，耐力训练未能改变趾长伸肌的任何突触参数。然而，同样的运动刺激对比目鱼肌产生了显著的突触前和突触后重塑，但并未改变神经肌肉接头的突触前到突触后耦合。还对比目鱼肌和趾长伸肌相同的肌纤维轮廓进行了分析。与神经肌肉接头不同，肌纤维在比目鱼肌和趾长伸肌中均显示出与年龄相关的显著萎缩。总体而言，这些结果证实，尽管训练导致神经肌肉接头发生显著重构，但突触前到突触后耦合保持完整，这突出了维持神经递质释放和结合位点适当对接的重要性，从而确保有效的神经到肌肉的通信。
