[The ventilatory sensitivity of decerebrate vagotomized cats to CO2 after blockade of the trigeminal nerves]. / Ventiliatornaia chuvstvitel'nost' detserebrirovannykh vagotomirovannykh koshek k CO2 posle blokady troinichnykh nervov.

The dependence of the lung ventilation per minute (VI) on the CO2 partial pressure in the terminal portion of expired air (PET, CO2) was studied prior to and after the blockade of trigeminal nerves in decerebrated vagotomized cats. The thermal blockade entailed a 5.5 mm Hg shift of the regression curve to the left. The point of crossing of the curve with the pCO2 axis shifted from 22.6 to 17.1 mm Hg. The curve inclination changed insignificantly. Prior to and after the blockade, a positive correlation existed between VI and respiratory volumes, the connection between VI and the respiration rate being absent. Tonic afferents of trigeminal nerves seem to reduce the responsiveness of respiratory mechanism to chemoreceptor afferent input, decreasing ventilatory responses to CO2.

[Effect of nasal breathing and blockade of the trigeminal nerves on the CO2 concentration in alveolar air in decerebrated cats]. / Vliianie nosovogo dykhaniia i blokady troinichnykh nervov na kontsentratsiiu CO2 v alveoliarnom vozdukhe u detserebrirovannykh koshek.

In 14 decerebrated and vagotomized cats, the changes of end tidal CO2 fraction (FET. CO2) and lung ventilation after thermal blockade of the trigeminal nerves, were determined. The values of the lung ventilation and FET,CO2 were compared for breathing through the tracheotomy tube and through the nose. After the trigeminal nerves blockade, FET,CO2 was diminished whereas the lung ventilation increased; the diminution of FET,CO2 was a consequence of the lung ventilation increase. The changes were more evident with nasal rather than tracheal breathing because of cessation of not only tonic afferent impulsation but the impulsation from "flow" receptors in the nose as well. After the onset of nasal breathing the intensity of inhibitory influence of the "flow" receptors was temporarily diminished. Afferent impulses in the trigeminal nerves move the CO2 tension set point to a lower level by depressing the responses of central respiratory mechanism to the chemoreceptor signals.