Respiratory effects of pneumotaxic center lesions and subsequent vagotomy in chronic cats.

Ventilation was monitored in awake and anesthetized cats breathing air or CO2 mixtures, both before and after lesions in the pneumotaxic center region and after subsequent bilateral vagotomy. Cats with pontile lesions had, relative to intact state, a prolonged inspiratory duration and an increase in tidal volume and expiration duration. The changes seen on the spirogram differed quantitatively according to the region of the pneumotaxic system which was destroyed. After subsequent bilateral vagotomy, respiratory phases and tidal volume were greatly increased. These results indicate that the pneumotaxic center would control the sensitivity of Breuer-Hering reflex and that the inspiratory activity is released by the successive suppression of the two inspiratory-inhibitory mechanisms, i.e., the pneumotaxic center and the vagal pulmonary afferents.