a-adrenergic receptor responsiveness and baroreflex control of muscle blood flow:human and animal studies

[目的]：在动物和人类的研究中，评估血管平滑肌的α-肾上腺素能反应性对运动过程中肌肉血流压力反射控制的影响。[人类研究]：1)测量方法的建立：肌肉血管电导的测定：我们从前臂血管电导的变化来确定a-肾上腺素能反应性，以响应如此少量的苯肾上腺素注入臂动脉以至全身动脉压不增加。压力反射敏感性的测定：我们根据心率或肌肉交感神经活动对动脉压自发变化的反应以及心率或麝香的变化来确定压力感受器反射的敏感性：正中静脉注射苯肾上腺素或硝普钠对交感神经活动的影响。DOE测量在体位性心动过速综合征患者中的应用：我们在POTS患者中检测到心脏搏动体积…耐力训练的效果：我们发现，在耐力训练后，健康青年男性的外周α-肾上腺素能反应性降低，压力反射敏感性增加。[小鼠研究]：我们评估了加压素V1a受体缺陷小鼠对急性低血容量的压力反射敏感性，并证实心脏压力反射敏感性在小鼠心脏压力反射敏感性降低，而对照组小鼠的压力反射敏感性增加。[结论]这些结果提示耐力训练后外周α-肾上腺素能反应性降低，并伴随压力反射敏感性增加的代偿适应。加压素V1a受体可能参与了这一机制。然而，由于我们发现PARS患者对直立姿势的心脏反应降低并没有引起压力反射敏感性的增加，压力反射敏感性的增强可能是由外周血管的α-肾上腺素能反应性降低引起的。较少

[Purpose]:To assess the effects of a-adrenergic responsiveness in the vascular smooth mum/a on baroreflex control of muscle blood flow during exercise in animal and human studies.[Human studies]:1) Establishment of measurements:Determination of muscular vascular conductance: We determined the a-adrenergic responsiveness from change in forearm vascular conductance in response to such a small amount of phenylephrine injected into the brachial artery that systemic arterial pressure did not increase.Determination of baroreflex sensitivity: We determined baroreflex sensitivity from change in heart rate or muscle sympathetic nervous activity in response to spontaneous change in arterial pressure and also from change in heart rate or musk:, sympathetic nervous activity in response to a bolus injection of phenylephrine or sodium nitroprusside into the median vein.Application of doe measurements to PUTS (postural tachycardia syndrome) patients:We Sound in POTS patients that cardiac stroke volum … More e was lower during rest and exercise than in control subjects while peripheral a-adrenergic responsiveness was preserved.Effects of endurance training:We found that peripheral a-adrenergic responsiveness decreased and baroreflex sensitivity increased after endurance training in young healthy men.[Mouse studies]:We assessed baroreflex sensitivity response to acute hypovolemia in a mouse deficient of vasopressin V1a receptor and bind that cardiac baroreflex sensitivity decreased in the mouse while that increased in a control mouse.[Conclusions]These results suggest that peripheral a-adrenergic responsiveness decreased after endurance training which was accompanied by compensatory adaptation of an increase in baroreflex sensitivity. Vasopressin V1a receptors might be involved in this mechanism. However since we found that the reduced cardiac response to an upright posture in pars patients did not evoke an increase in baroreflex sensitivity, the enhanced baroreflex sensitivity might lie specifically caused by reduced a-adrenergic responsiveness in the peripheral vessels. Less