[The ventilatory sensitivity of decerebrate vagotomized cats to CO2 after blockade of the trigeminal nerves].

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.