Bilateral lesions of pontine Kölliker-Fuse nuclei provoke apnea instead of apneusis in anesthetized adult rats.

The Kölliker-Fuse nucleus (KF) has been traditionally dubbed the "pneumotaxic center". Here, we report that lesions of KF nuclei of bilateral pons caused apnea (complete cessation of phrenic discharge) instead of apneusis in urethane-anesthetized, vagotomized, paralyzed and ventilated adult rats. After bilateral lesions of KF nuclei with the neuroexcitotoxin kainic acid, phrenic discharge disappeared and no spontaneous recovery of phrenic discharge was observed for up to 3 hours. During the apnea, hypoxia or hypercapnia provoked transient rhythmic phrenic discharge. The present finding showed that the KF nucleus not only directly participates in inspiratory to expiratory phase switching, but also provides a vital excitatory drive that is requisite for the generation of inspiratory activity.