Davenport P W, Dalziel D J, Webb B, Bellah J R, Vierck C J
Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville 32610.
J Appl Physiol (1985). 1991 Mar;70(3):1284-9. doi: 10.1152/jappl.1991.70.3.1284.
The physiological mechanisms mediating the detection of mechanical loads are unknown. This is, in part, due to the lack of an animal model of load detection that could be used to investigate specific sensory systems. We used American Foxhounds with tracheal stomata to behaviorally condition the detection of inspiratory occlusion and graded resistive loads. The resistive loads were presented with a loading manifold connected to the inspiratory port of a non-rebreathing valve. The dogs signaled detection of the load by lifting their front paw off a lever. Inspiratory occlusion was used as the initial training stimulus, and the dogs could reliably respond within the first or second inspiratory effort to 100% of the occlusion presentations after 13 trials. Graded resistances that spanned the 50% detection threshold were then presented. The detection threshold resistances (delta R50) were 0.96 and 1.70 cmH2O.l-1.s. Ratios of delta R50 to background resistance were 0.15 and 0.30. The near-threshold resistive loads did not significantly change expired PCO2 or breathing patterns. These results demonstrate that dogs can be conditioned to reliably and specifically signal the detection of graded inspiratory mechanical loads. Inspiration through the tracheal stoma excludes afferents in the upper extrathoracic trachea, larynx, pharynx, nasal passages, and mouth from mediating load detection in these dogs. It is unknown which remaining afferents (vagal or respiratory muscle) are responsible for load detection.
介导机械负荷检测的生理机制尚不清楚。部分原因是缺乏可用于研究特定感觉系统的负荷检测动物模型。我们使用带有气管造口的美国猎狐犬，对吸气阻塞和分级阻力负荷的检测进行行为训练。阻力负荷通过连接到非重复呼吸阀吸气口的加载歧管呈现。狗通过将前爪从杠杆上抬起发出检测到负荷的信号。吸气阻塞用作初始训练刺激，经过13次试验后，狗能够在第一次或第二次吸气时对100%的阻塞呈现可靠地做出反应。然后呈现跨越50%检测阈值的分级阻力。检测阈值阻力（δR50）分别为0.96和1.70 cmH2O·l-1·s。δR50与背景阻力的比值分别为0.15和0.30。接近阈值的阻力负荷并未显著改变呼出的PCO2或呼吸模式。这些结果表明，狗可以被训练可靠且特异性地发出分级吸气机械负荷检测的信号。通过气管造口吸气排除了胸外上段气管、喉、咽、鼻腔和口腔中的传入神经介导这些狗的负荷检测。尚不清楚其余哪些传入神经（迷走神经或呼吸肌传入神经）负责负荷检测。
