Differential sympathetic reflex control in excerise

描述(申请人提供)：在人类和动物的运动中，运动加压反射被广泛认为在控制交感神经流出到血管系统中起着重要的机械作用。这种反射被认为是由收缩骨骼肌引起的，由两种类型的刺激引起，即机械刺激和新陈代谢刺激。运动加压反射弧的感觉臂由III族和IV族纤维组成，统称为细纤维肌肉传入。I类和II类纤维不参与这种反射的诱发。尽管运动升压反射在运动过程中升高动脉血压的作用已经得到证实，但其对交感神经流出到特定内脏和躯体结构的控制存在争议。尤其是代谢物受体在反射性地激活交感神经流出到皮肤血管系统中所起的作用。此外，细纤维机械受体和代谢物受体在激活交感神经流出到骨骼肌和肾脏中所起的具体作用尚不清楚。 本实验将确定阻断细纤维肌力感受器和代谢物感受器对支配后肢毛皮血管、后肢骨骼肌血管和肾脏的单纤维交感节后传出纤维反应的影响。来自去大脑未麻醉猫的小腿三头肌的机械感受器输入将通过延髓动脉注射Gd来阻止，Gd是一种阻断机械通道的药物。动脉注射PPADS，一种嘌呤能2受体拮抗剂，将阻断来自这些肌肉的代谢物受体的输入。传出放电的交感性质将通过以下方式确定：1)显示传出神经被施加于胸或腰交感神经链的电脉冲所激活；显示自发和诱发的活动都被六甲基溴铵神经节阻断所阻止；表明肾脏、肌肉和皮肤交感神经放电的活动受到动脉压力感受器的控制。这些实验将提供有关细纤维肌肉机械感受器和代谢物感受器在控制运动中交感神经流出中所起作用的新信息。

DESCRIPTION (provided by applicant): The exercise pressor reflex is widely believed to play an important rote in controlling the sympathetic outflow to the vasculature during exercise in both humans and animals. The reflex is believed to arise from contracting skeletal muscles and is evoked by two types of stimuli, namely mechanical and metabolic. The sensory arm of the exercise pressor reflex arc is comprised of group III and IV fibers, which together haw been termed thin fiber muscle afferents.. Group I and II fibers do not participate in evoking this reflex. Although the role played the exercise pressor reflex in increasing arterial blood pressure during exercis, is well established, its control of the sympathetic outflow to specific visceral and somatic structures controversial. This is especially the case for the role played by metaboreceptors in reflexly activating the sympathetic outflow to the vasculature of the skin. In addition, the specific roles played by thin fiber mechanoreceptors and metaboreceptors in activating the sympathetic outflow to the skeletal muscles and the kidney are unknown. The experiments proposed in this application will determine the effect of blocking the contractioninduced input from thin fiber muscle mechanoreceptors and metaboreceptors on the responses of single fiber sympathetic postganglionic efferent fibers innervating the vasculature of hind limb hairy skin, the vasculature of hind limb skeletal muscle and the kidney. Mechanoreceptor input arising from the triceps surae muscles of decerebrate unanesthetized cats will be prevented by popliteal arterial injections of gadolinium, an agent which blocks mechanogated channels. Metaboreceptor input from these muscles will be blocked by popliteal arterial injections of PPADS, a purinergic 2 receptor antagonist. The sympathetic nature of the efferent discharge will be identified by: 1.) showing that the efferents are activated by an electrical pulse applied to the thoracic or lumbar sympathetic chain; 2.) showing that both spontaneous and evoked activity is prevented by ganglionic blockade with hexamethonium; and 3.) showing that the activity of the renal, muscle and to a lesser extent, skin sympathetic discharge is under control of the arterial baroreceptors. The proposed experiments will provide new information about the role played by thin fiber muscle mechanoreceptors and metaboreceptors in controlling the sympathetic outflow during exercise.