Fictive lung ventilation in the isolated brainstem preparation of the aquatic frog, Xenopus laevis.

Aquatic pipid frogs, unlike other anurans, never show sole buccal ventilation cycle, and exhale air from the lung before aspirating air into the buccal cavity. To study the mechanism that pipid frogs lack the buccal cycle, respiratory motor activities were recorded from the isolated brainstem-spinal cord preparation of Xenopus laevis. Brainstem preparations of Xenopus exhibited the intermittent burst complex (lung bursts) similar to the lung ventilation cycle in vivo. Lung bursts spontaneously occurred in the cranial nerve V, IX and X, and in the hypoglossal and third spinal nerves. Small bursts with regular cycle similar to buccal oscillation in ranid frogs, were observed in the cranial nerve V and X but not in the hypoglossal and the third spinal nerve. These results suggest that Xenopus is capable of oscillating buccal rhythm within the brainstem.