Distribution of oxygen partial pressure in the carotid body region and in the carotid body (rabbit).

In the specific tissue of the rabbit carotid body as well as in the connective tissue surrounding the organ, pO2 distribution was measured with membrane-covered needle electrodes (tip diameter 1-2 microns). The histograms resulting from measurements in the specific tissue were shifted to low pO2 values as compared to other tissues. The oxygen blowing test, i.e. exposure of the carotid body to humidified 100% oxygen was employed to decide upon the site of measurement: pO2 increased when the electrode measured in the surrounding tissue (type 1 response); pO2 remained stable or slightly decreased when the electrode sampled in the specific carotid body tissue (type 2 response). After the experiment, the electrode track was reconstructed from histological serial sections and the type of reaction was related to the type of tissue. Low pO2 values were found to prevail in the specific carotid body tissue, which leads to the conclusion that the amount of low pO2 values determines the degree of chemoreceptor activity.