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Attenuated carotid body hypoxic sensitivity after prolonged hypoxic exposure
K Tatsumi1, C K Pickett, J V Weil
1Cardiovascular Pulmonary Research Laboratory, University of Colorado Health Sciences Center, Denver 80262.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|February 1, 1991
Summary
Chronic hypoxia decreases the hypoxic ventilatory response (HVR) by reducing peripheral chemoreceptor sensitivity. This study in cats shows reduced carotid sinus nerve activity, indicating peripheral mechanisms contribute to HVR desensitization.
Area of Science:
- Physiology
- Respiratory Physiology
- Neuroscience
Background:
- Prolonged hypoxia exposure typically reduces the hypoxic ventilatory response (HVR).
- The specific contributions of peripheral and central mechanisms to this hypoxic desensitization are not fully understood.
Purpose of the Study:
- To investigate whether chronic hypoxia diminishes the sensitivity of peripheral chemoreceptors.
- To determine the role of peripheral chemoreceptor function in the overall decrease of HVR during sustained hypoxia.
Main Methods:
- Ventilatory and carotid sinus nerve (CSN) responses to isocapnic hypoxia were measured in cats.
- Cats were exposed to simulated high altitude (5,500 m) for 3-4 weeks.
- Hypoxic ventilatory response (HVR) and carotid body response to hypoxia were assessed.
Main Results:
- Chronic hypoxia exposure significantly decreased HVR in both awake and anesthetized cats.
- Sustained hypoxia led to a reduction in end-tidal CO2 tension (PETCO2).
- Even under eucapnic conditions, HVR remained depressed after hypoxic exposure, and carotid body response to hypoxia was significantly lower compared to controls.
Conclusions:
- The sensitivity of peripheral chemoreceptors, specifically the carotid bodies, decreases with prolonged exposure to hypoxia.
- Peripheral mechanisms play a significant role in the desensitization of the hypoxic ventilatory response observed during chronic hypoxia.