[Suppressive effect of carbon dioxide on excitation of the cold receptors of the nasal cavity of the cat].

The impulse activity of afferent fibers was studied in n. ethmoidalis. While the room air was being sucked in through the nasal cavity to choanes, marked excitation of cold receptors of the nasal cavity walls occurred. In the air current from the choanes to the nostrils, the activity of the receptors was depressed. Insufflation through the nasal cavity of the mixtures of CO2 (1, 3, 6%) with air also depressed the activity of cold receptors. The degree of the depression depended on the concentration of CO2. The cold receptors of nasal cavity like the lung stretch receptors, have the features of chemoreceptors. Their activity is depressed with physiological concentrations of CO2 in the air.