Faculty of Kinesiology & Recreation Management, University of Manitoba, Winnipeg, Manitoba R3E 0W3, Canada; Spinal Cord Research Center, Department of Physiology, University of Manitoba, Winnipeg, Manitoba R3E 0W3, Canada.
Neuroscience. 2013;255:45-54. doi: 10.1016/j.neuroscience.2013.09.038. Epub 2013 Sep 27.
Electrophysiological properties of lumbar α-motoneurons change after chronic increases and decreases in hindlimb neuromuscular activity. Although modeling of these changes suggests that motoneurons probably alter gene expression in these situations, there is no evidence that this is the case. In this study, we measured the content of several mRNAs in lumbar motoneurons, harvested using laser capture microdissection, from rats previously subjected to normal cage activity, voluntary wheel exercise for 16weeks, and forced treadmill training for 7days and 16weeks. As a result of the prolonged daily treadmill training, but not the voluntary wheel training, significant increases occurred in muscle peroxisome proliferator-activated receptor gamma, coactivator 1 alpha (PGC-1α) mRNA, and in muscle PGC-1α and cytochrome oxidase proteins, in soleus and plantaris muscles. Significant changes in mRNA contents (decreases) were evident for the receptors 5-hydroxytryptamine (serotonin) receptor 1A (5HT1a), GABA A receptor, subunit alpha 2 (GABAAα2), and for the potassium conductance calcium-activated channel protein (SK2) in the motoneurons from 16-week-trained rats, and for glutamate receptor, metabotropic 1 (mGluR1) in the voluntary wheel-trained rats. Motoneurons from 16-week treadmill-trained rats also did not demonstrate the decreases in several mRNAs that were evident after 7days of treadmill exercise, suggesting an adaptation of motoneurons to acute stress. The mRNA changes following prolonged daily treadmill training are consistent with a reduction in inhibitory influences onto motoneurons, and a transition toward motoneurons that innervate slower contracting muscle fibers. These results demonstrate that the previously reported physiological changes in motoneurons with altered activity are accompanied by changes in gene expression.
慢性增加和减少后肢神经肌肉活动会改变腰α运动神经元的电生理特性。虽然这些变化的建模表明运动神经元在这些情况下可能会改变基因表达，但目前尚无证据表明这是事实。在这项研究中，我们使用激光捕获显微解剖术从以前接受过正常笼内活动、16 周自愿轮式运动和 7 天和 16 周强制跑步机训练的大鼠中测量了腰运动神经元中的几种 mRNA 的含量。由于长时间的日常跑步机训练，但不是自愿轮式训练，导致比目鱼肌和跖肌中的肌肉过氧化物酶体增殖物激活受体γ、共激活因子 1α（PGC-1α）mRNA 以及肌肉 PGC-1α 和细胞色素氧化酶蛋白显著增加。16 周训练大鼠的运动神经元中 5-羟色胺（血清素）受体 1A（5HT1a）、GABA A 受体亚单位α2（GABAAα2）和钾电流钙激活通道蛋白（SK2）的 mRNA 含量（减少）发生了显著变化，而自愿轮式训练大鼠的谷氨酸受体代谢型 1（mGluR1）也发生了变化。16 周跑步机训练大鼠的运动神经元也没有显示出 7 天跑步机运动后明显减少的几种 mRNA，这表明运动神经元适应了急性应激。长期每日跑步机训练后的 mRNA 变化与抑制性影响到运动神经元的减少以及向支配较慢收缩肌纤维的运动神经元的转变一致。这些结果表明，先前报道的活动改变的运动神经元的生理变化伴随着基因表达的变化。
