STATIC AND DYNAMIC CAROTID CHEMORECEPTOR RESPONSES

尽管已知鸟类和哺乳动物颈动脉体化学感受器 结构相似，并在控制中发挥类似的功能， 通气，单单位鸡的刺激反应特性 颈动脉化学感受器的文献很少。 拟定的研究将 使用单单位神经元建立功能相似性和差异性 记录技术。 鸟类颈动脉的静态和动态响应 化学感受器的适当刺激将被定义，和他们的 对已知影响哺乳动物颈动脉体的物质的反应--例如， 寡霉素KCN和去甲肾上腺素 鸟类的模式 颈动脉体放电将用峰间期定量 直方图 稳定水平的pH值、PCO 2和CO2浓度的独立和交互作用， 禽颈动脉化学感受器上的PO 2将从单个单位测定 刺激-反应曲线 低碳酸-低氧刺激的受体反应 因为鸟类的上级低氧耐受性 与哺乳动物相比，部分原因可能是由于更强的缺氧驱动力， 鸟 与潮气呼吸相关的动脉PCO 2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PCO 2 预测鸟类的振荡甚至更大，相关性将是 鸟类颈动脉化学感受器放电模式之间， 用血管内pH电极测量动脉PCO 2振荡。 假设颈动脉化学感受器的动态反应可能有助于 通过检测运动引起的代谢变化， 将测试动脉PCO 2振荡。 动态受体反应将 在迫使动脉PCO 2振荡变化形状的同时进行定量 和频率，使用人工单向肺通气。 禽肺的单向通气提供了一个强有力的工具， 控制动脉气体张力，允许系统分析方法， 对感受器频率反应的研究。 正弦PCO 2振荡 将用于确定鸟类颈动脉的频率响应 化学感受器，和斜坡振荡与不同的上升和下降斜率，但 恒定的周期和振幅，将用于确定速率的影响 PCO_2变化对感受器放电的影响。 类似的实验会很多 在哺乳动物中更难。 这项研究的结果将扩大我们的 鸟类颈动脉体化学感受器反应的知识，并用于指导 对颈动脉体的进一步研究。

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.