Blanco C E, Zhan W Z, Fang Y H, Sieck G C
Department of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, California 90033.
J Appl Physiol (1985). 2001 Mar;90(3):850-6. doi: 10.1152/jappl.2001.90.3.850.
The effect of chronic exogenous testosterone (T) treatment on neuromuscular transmission in the diaphragm (Dia) muscle of adult male rats was determined. The contribution of neuromuscular transmission failure (NTF) to Dia fatigue was evaluated by superimposing intermittent direct muscle stimulation on repetitive nerve stimulation of isometric contraction in vitro. T treatment significantly reduced the contribution of NTF to Dia fatigue by approximately 20% (P < 0.001). Fiber type-specific effects on NTF were determined by measuring Dia fiber glycogen levels subsequent to repetitive nerve or muscle stimulation. T treatment had no effect on glycogen depletion in Dia type I and IIa fibers regardless of stimulation route. In the control group, type IIx fibers demonstrated significantly less glycogen depletion after nerve stimulation compared with direct muscle stimulation (P < 0.05), suggesting the presence of NTF. In contrast, T treatment increased glycogen depletion of type IIx fibers during nerve stimulation to levels similar to those after direct muscle stimulation. These data indicate that testosterone treatment substantially improves neuromuscular transmission in the Dia.
确定了慢性外源性睾酮（T）治疗对成年雄性大鼠膈肌（Dia）神经肌肉传递的影响。通过在体外等长收缩的重复神经刺激上叠加间歇性直接肌肉刺激，评估神经肌肉传递失败（NTF）对Dia疲劳的影响。T治疗使NTF对Dia疲劳的影响显著降低了约20%（P<0.001）。通过在重复神经或肌肉刺激后测量Dia纤维糖原水平，确定了对NTF的纤维类型特异性影响。无论刺激途径如何，T治疗对Dia I型和IIa型纤维的糖原消耗均无影响。在对照组中，与直接肌肉刺激相比，IIx型纤维在神经刺激后糖原消耗显著减少（P<0.05），表明存在NTF。相反，T治疗使神经刺激期间IIx型纤维的糖原消耗增加至与直接肌肉刺激后相似的水平。这些数据表明，睾酮治疗可显著改善Dia的神经肌肉传递。
