Effects of vagotomy on the excitability of the respiratory center to blood CO2.

The role of the vagus nerve concerning the reflex control of respiration has been more clarified with the elaboration of Pitts et al.(1), and a new account for the repetitive discharge of the respiratory center was attempted by these investigators. However, as the total pulmonary ventilation after vagotomy does not, as a rule, undergo any marked change though the animals would breathe slowly and deeply, the influences of the vagus nerve on the excitability of the respiratory center to blood CO2 seem to be almost out of considerations with the present physiologists participating in the studies of respiration. As regards the disturbance of the acid base balance of the blood after vagotomy, some investigators have already been reported, but the results obtained are far from being in agreement with each other: Konno (2) reported the shift to alkaline side of the blood H, while Liu and Kruger (3) the shift to acid side. Ihara (4) observed no change. On the other hand, Niscolosi (5) and others (6, 7) observed decrease of the total blood CO2after vagotomy, but Cokkalis and Nissen (8) reported the reverse results. Scott (9) and Meltzer and Steuber (10) showed that the effects of vagotomy on the alveolar PCO2were very inconsistent. From these diverse experimental results, no decisive information could be drawn concerning the changes of the acid base balance of the blood after vagotomy. In our laboratory, a glasselectrode assembly suitable for continuous recording of PH, with an accuracy of•}0.01PH, of the circulating arterial blood was devised. The present study attempted to elucidate by using this glasselectrode the effect of vagotomy on the acid base balance of the arterial blood and the part of the vagus nerve in the regulation of the excitability of the respiratory center to blood CO2.