Ventilation and carotid chemoreceptor discharge during venous CO 2 loading via the gut

Abstract

A simple method of loading CO 2 into the venous blood of anaesthetized or decerebrate cats is described. Heated humidified gas of high CO 2 content is passed retrogradely through the gut. This increases CO 2 elimination from the lungs by 1.8 to 3.6 fold, minute ventilation by 1.5 to 2.7 fold and cardiac output by 1.1 to 1.6 fold. This method of venous CO 2 loading allows the recording of afferent nerve impulses. We show that it has little effect on the mean discharge frequency of carotid body chemoreceptors when end-tidal gases are held constant, but that it enhances greatly the amplitude of the respiratory oscillation of their discharge.