PURPOSE:To evaluate whether the BOLD signal from skeletal muscle can be modulated by exercise and ingestion of vasoactive substances. MATERIALS AND METHODS:The right calf muscles of healthy adult volunteers were imaged using a GE 1.5-Tesla scanner and a gradient-echo sequence with spiral readout. Time-varying changes in the BOLD signal were induced through cyclic phases of normoxia (90 seconds of 20.8% O2) and hyperoxia (45 seconds of 100% O2 at 22 L/minute). Superimposed on this paradigm were pre- and post-exercise regimes, with and without ingestion of caffeine (100 mg) or antihistamine (4 mg chlorpheniramine). The numbers of voxels within slow-twitch (soleus) and fast-twitch (gastrocnemius) muscles that significantly responded to the paradigms were scored and compared using the AFNI software (NIMH). RESULTS:Cycling-inspired O2 produced a corresponding BOLD modulation that increased in magnitude with exercise. Chlorpheniramine significantly (P<0.01) prevented the overall increase in exercise-induced soleus muscle BOLD signal, while caffeine accentuated the increase (P<0.05) in the gastrocnemius relative to control (no vasomodulator) conditions. CONCLUSION:BOLD signal changes with exercise can be modulated by standard doses of chlorpheniramine (antihistamine) and caffeine. We suggest that chlorpheniramine may act detrimentally on slow-twitch muscle contractility, while caffeine appears to improve fast-twitch muscle function.

译文

目的:评估骨骼肌的BOLD信号是否可以通过运动和摄入血管活性物质来调节。
材料与方法:使用GE 1.5-Tesla扫描仪和带有螺旋读数的梯度回波序列对健康成人志愿者的右小腿肌肉成像。 BOLD信号的时变变化是通过常氧(90秒的20.8%O2)和高氧(45秒的100%O2在45 L下以22 L / min)的循环阶段引起的。在运动前和运动后的治疗方案中均叠加了这种模式,可以摄入或不摄入咖啡因(100毫克)或抗组胺药(4毫克氯苯那敏)。使用AFNI软件(NIMH)对慢肌(比目鱼肌)和快肌(腓肠肌)中对范例有明显反应的体素数进行评分和比较。
结果:受自行车启发的氧气产生了相应的BOLD调节,随着运动强度的增加。氯苯那敏显着(P <0.01)阻止了运动引起的比目鱼肌BOLD信号的总体增加,而咖啡因则使腓肠肌相对于对照(无血管调节剂)的情况增加(P <0.05)。
结论:运动后大胆信号的变化可通过标准剂量的扑尔敏(抗组胺剂)和咖啡因来调节。我们建议氯苯那敏可能对慢抽搐的肌肉收缩有害,而咖啡因似乎可以改善快抽搐的肌肉功能。

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