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

【目的】：通过动物和人体实验，评估血管平滑肌a-肾上腺素能反应对运动时肌肉血流压力反射控制的影响。【人体研究】：1)测量方法的建立：肌肉血管电导的测定：我们通过前臂血管电导的变化来测定a-肾上腺素能反应性，这是对肱动脉注射少量苯肾上腺素的反应，全身动脉压没有增加。血压反射敏感性的测定：我们通过心率或肌肉交感神经活动的变化对动脉压的自发变化的反应来测定血压反射敏感性，也通过心率或麝香的变化，对正中静脉注射苯肾上腺素或硝普钠的反应，交感神经活动。doe测量在体位性心动过速综合征（PUTS）患者中的应用：我们发现POTS患者在休息和运动期间的心搏容量比对照组低，但周围a-肾上腺素能反应性保持不变。耐力训练的影响：我们发现年轻健康男性在耐力训练后外周a-肾上腺素能反应性降低，压力反射敏感性增加。【小鼠研究】：我们评估了抗利尿激素V1a受体缺乏小鼠对急性低血容量的压力反射敏感性反应，并发现小鼠的心脏压力反射敏感性下降，而对照组小鼠的心脏压力反射敏感性增加。[结论]耐力训练后外周a-肾上腺素能反应性下降，并伴有压力反射敏感性增加的代偿性适应。抗利尿激素V1a受体可能参与了这一机制。然而，由于我们发现parpa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周围血管a-肾上腺素能反应性降低引起的。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