STATIC AND DYNAMIC CAROTID CHEMORECEPTOR RESPONSES

尽管已知鸟类和哺乳动物的颈动脉小体化学感受器 在结构上相似，并在控制 通风--单单元禽类的刺激反应特性 颈动脉化学感受器的文献记载很少。拟议的研究将 用单单位神经建立功能上的异同 录音技术。家禽颈动脉的静态和动态反应 将定义化学感受器对其适当的刺激，以及它们的 对已知影响哺乳动物颈动脉小体的物质的反应--例如。 寡霉素、KCN和去甲肾上腺素--表征。鸟类的花纹 颈动脉小体放电将用峰间间期进行量化 直方图。 稳定的pH、二氧化碳和二氧化碳水平的独立和交互影响 禽颈动脉化学感受器上的PO2将由单个单位测定 刺激-反应曲线。受体对低二氧化碳-低氧刺激的反应 将特别引起人们的兴趣，因为鸟类对低氧的耐受性很强 与哺乳动物相比，部分原因可能是更强的低氧驱动力 鸟。与潮气呼吸有关的动脉二氧化碳分压振荡影响颈动脉 哺乳动物的化学感受器放电模式。由于动脉血二氧化碳分压 据预测，鸟类的振荡会更大，相关性将是 在鸟类颈动脉化学感受器放电模式和 用血管内pH电极测量动脉血二氧化碳分压振荡。 颈动脉化学感受器的动态反应可能有帮助的假设 通过检测运动诱导的变化将呼吸机与新陈代谢结合起来 将测试动脉二氧化碳分压振荡。动态受体反应将 在施加各种形状的动脉二氧化碳分压振荡时被量化 和频率，使用人工单向肺通气。 鸟肺的单向通风提供了一种强有力的工具 控制动脉气体张力，允许采用系统分析方法 受体频率响应的研究。正弦PCO2振荡 将被用来确定鸟类颈动脉的频率响应 化学感受器，以及具有不同上下斜率的斜坡振荡，但是 恒定的周期和幅度，将被用来确定速率的影响 受体放电时二氧化碳含量的变化。类似的实验将会是 对哺乳动物来说更难。这项研究的结果将扩大我们的 了解家禽颈动脉小体化学感受器反应，并用于指导 对颈动脉小体的进一步研究。

Although avian and mammalian carotid body chemoreceptors are known to be structurally similar, and to serve similar functions in the control of ventilation, the stimulus-response characteristics of single unit avian carotid chemoreceptors are poorly documented. The proposed study will establish functional similarities and differences using single unit neural recording techniques. Static and dynamic responses of avian carotid chemoreceptors to their adequate stimuli will be defined, and their responses to substances known to affect mammalian carotid bodies--eg. oligomycin, KCN, and norepinephrine--characterized. The pattern of avian carotid body discharge will be quantitated with interspike interval histograms. The independent and interactive effects of steady levels of pH, PCO2, and PO2 on avian carotid chemoreceptors will be determined from single unit stimulus-response curves. Receptor responses to hypocapnic-hypoxic stimuli will be of special interest because the superior hypoxic tolerance of birds compared to mammals may be partly due to a stronger hypoxic drive in birds. Arterial PCO2 oscillations linked to tidal breathing affect carotid chemoreceptor discharge patterns in mammals. Since arterial PCO2 oscillations are predicted to be even larger in birds, correlations will be made between avian carotid chemoreceptor discharge pattern, and the arterial PCO2 oscillations measured wiith an intravascular pH electrode. The hypothesis that dynamic responses of carotid chemoreceptors may help couple ventilation to metabolism by detecting exercise-induced changes in arterial PCO2 oscillations will be tested. Dynamic receptor responses will be quantitated while forcing arterial PCO2 oscillations of varying shape and frequency, using artificial, unidirectional pulmonary ventilation. Unidirectional ventilation of the avian lung offers a powerful tool for controlling arterial gas tensions, allowing a systems analysis approach to the study of receptor frequency response. Sinusoidal PCO2 oscillations will be used to determine the frequency response of avian carotid chemoreceptors, and ramp oscillations with varying up and down slopes, but constant period and amplitude, will be used to determine the effect of rate of PCO2 change on receptor discharge. Similar experiments would be much more difficult in mammals. The results of this study will broaden our knowledge of avian carotid body chemoreceptor responses, and serve to guide further studies of carotid bodies in general.