Activity of Chemoreceptor Fibers in the Sinus Nerve and Tissue PO2 in the Carotid Body of the Cat
ACKER, LÜBBERS and PURVES (1) found that tissue pO2 (pTO2) in the carotid body of the cat is related to arterial oxygen pressure (paO2) in a nearly linear function. In accordance with these results BISCOE et al. (3) described a close correlation between changes of the paO2 and the activity of chemoreceptor units in the carotid body. In our own experiments, however, especially in few fiber preparations this close relation was often missing. In parallel with a stepwise lowering of the paO2 from normoxic to hypoxic values of about 20 mmHg we observed a time course of receptor activity which frequently differed from the response found during the following reincrease in the paO2 up to normal levels. As a whole, our experiments led to assume that the relation between the paO2, the pO2 in tissue and the chemoreceptor activity was altered, if the experimental variations of the paO2 exceeded the physiological range either to hypoxic or to hyperoxic values. To test this hypothesis, simultaneous measurements of the paO2, of pO2 in tissue of the carotid body and recordings of the discharge rate in few fiber preparations of the sinus nerve were performed in anaesthetized, relaxed and artificially ventilated cats. These experiments have been carried out together with KELLER, CASPERS and LÜBBERS and will be reported elsewhere. In the following the relationship between the activity of nerve fibers and the tissue pO2 will be especially discussed.
KeywordsCarotid Body Frequency Curve Severe Hypoxia Fiber Preparation Arterial Oxygen Pressure
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