Einsiedel L J, Luff A R
Department of Physiology, Monash University, Clayton, Victoria, Australia.
J Appl Physiol (1985). 1994 Jun;76(6):2663-71. doi: 10.1152/jappl.1994.76.6.2663.
The aim of the study was to determine whether increased motoneuron activity induced by treadmill walking would alter the extent of motoneuron sprouting in the partially denervated rat medial gastrocnemius muscle. An extensive partial denervation was effected by unilateral section of the L5 ventral root, and it is very likely that all units remaining in the medial gastrocnemius were used in treadmill walking. Rats were trained for 1.5 h/day and after 14 days were walking at least 1 km/day. Motor unit characteristics were determined 24 days after the partial denervation and were compared with units from partially denervated control (PDC) animals and with units from normal (control) animals. In PDC rats, force developed by slow, fast fatigue-resistant, and fast intermediate-fatigable motor units increased substantially compared with control animals; that of fast-fatigable units did not increase. In partially denervated exercised animals, force developed by slow and fast-fatigue-resistant units showed no further increase, but fast-intermediate- and fast-fatigable units showed significant increases compared with those in PDC animals. The changes in force were closely paralleled by changes in innervation ratios. We concluded that neuronal activity is an important factor in determining the rate of motoneuron sprouting.
本研究的目的是确定跑步机行走诱导的运动神经元活动增加是否会改变部分失神经支配的大鼠内侧腓肠肌中运动神经元的芽生程度。通过单侧切断L5腹根实现广泛的部分失神经支配，并且很可能内侧腓肠肌中剩余的所有运动单位都用于跑步机行走。大鼠每天训练1.5小时，14天后每天至少行走1公里。在部分失神经支配24天后测定运动单位特征，并与部分失神经支配对照（PDC）动物的运动单位以及正常（对照）动物的运动单位进行比较。在PDC大鼠中，慢肌、快速抗疲劳肌和快速中间易疲劳运动单位产生的力量与对照动物相比大幅增加；快速易疲劳单位产生的力量没有增加。在部分失神经支配的运动动物中，慢肌和快速抗疲劳单位产生的力量没有进一步增加，但快速中间易疲劳和快速易疲劳单位产生的力量与PDC动物相比显著增加。力量的变化与神经支配比的变化密切平行。我们得出结论，神经元活动是决定运动神经元芽生速率的一个重要因素。
