St-Pierre D, Gardiner P F
Exp Neurol. 1985 Dec;90(3):635-51. doi: 10.1016/0014-4886(85)90161-x.
The effect of disuse on the functional properties of fast-twitch mammalian muscle is controversial, perhaps because the various disuse models reduce activity to different degrees, and may introduce factors other than reduced activity per se. Our goal was to compare the effects of 14 days of disuse produced by neurally applied tetrodotoxin and joint fixation (knee and ankle) on several morphologic and functional characteristics of the rat gastrocnemius. Joint fixation produced a decrease in muscle wet weight and absolute tetanic tension measured in situ, and a preferential atrophy of slow-twitch fibers. The degree of atrophy was more severe with TTX-disuse and affected all fiber types to the same extent. In further contrast to joint fixation, TTX-disuse caused a preferential loss of myofibrillar protein and a decrease in tetanic tension per unit muscle wet weight. In addition, TTX-disuse resulted in an elevation of twitch:tetanic ratio, a prolonged twitch, and generated a relatively higher proportion of tetanic force at 50 Hz. The normalized maximal rate of tetanic tension development (% Po/ms) was highest in the TTX group. The fatigue index was unaffected by either intervention. The data suggest that complete disuse of mammalian fast-twitch muscle causes atrophy, prolongation of the twitch, and a loss in contractile strength per gram of tissue, and are consistent with qualitative or quantitative changes in the sarcoplasmic reticulum and a decrease in myofibrillar protein concentration with disuse.
废用对哺乳动物快肌功能特性的影响存在争议，可能是因为各种废用模型将活动降低到不同程度，并且可能引入除活动本身降低之外的因素。我们的目标是比较神经应用河豚毒素和关节固定（膝盖和脚踝）产生的14天废用对大鼠腓肠肌几种形态和功能特征的影响。关节固定导致肌肉湿重和原位测量的强直张力绝对值降低，以及慢肌纤维的优先萎缩。河豚毒素导致的废用萎缩程度更严重，并且对所有纤维类型的影响程度相同。与关节固定进一步不同的是，河豚毒素导致的废用导致肌原纤维蛋白优先丢失，并且每单位肌肉湿重的强直张力降低。此外，河豚毒素导致的废用导致收缩：强直比率升高、收缩延长，并且在50Hz时产生相对较高比例的强直力。河豚毒素组中强直张力发展的标准化最大速率（%Po/ms）最高。疲劳指数不受任何一种干预的影响。数据表明，哺乳动物快肌的完全废用会导致萎缩、收缩延长以及每克组织收缩强度的丧失，并且与肌浆网的定性或定量变化以及废用时肌原纤维蛋白浓度的降低一致。
