代償性に活動量増大を起こしたラット横隔膜の疲労耐性

概要

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The purpose of this study was to evaluate the alterations in muscle contractility and neuromuscular transmission in the rat diaphragm under conditions of increased activity. We used a model of unilateral denervation in the rat diaphragm muscle to induce compensatory activation on the contralateral side. The activity of compensatory activated diaphragm was increased by 〜40% following 2 weeks of contralateral denervation. Muscle fatigue induced by repetitive stimulation as well as the contribution of neuromuscular transmission failure (NF) to fatigue were measured in vitro. Fatigue resistance was measured as the relative drop in force production during isometric contractions induced by direct muscle stimulation at 40Hz (330ms trains every sec) over 2 min. Fatigue resistance was significantly increased in the compensatory activated diaphragm (33.7±7.4%), compared to control (26.1±5.1%). NF was measured by comparing decrement in muscle force during muscle vs.nerve stimulation at 40 or 75Hz. The contribution of NF to muscle faitgue was significantly decreased in the compensatory activated diaphragm (61.3±7.5% at 40Hz, 69.4±9.9% at 75Hz) compared to control (74.1±6.3% at 40Hz, 80.0±3.9% at 75Hz). We conclude that fatigue resistance is considerably improved in compensatory activated diaphragm due to both maintained muscle contractility as well as improved neuromuscular transmission.
日本運動生理学会の論文
2000-01-31