Buccal rhythmogenesis and CO sensitivity in Lithobates catesbeianus tadpole brainstems across metamorphosis.

Bullfrog tadpoles ventilate both the buccal cavity and lung. In isolated brainstems, the midbrain/pons influences CO responsiveness and timing of lung ventilatory bursting, depending on larval development. However, little is known about midbrain/pons influences on buccal burst patterns. As such, we investigated how removal of this region affects buccal burst shape and CO responsiveness across development. We measured facial nerve activity in brainstems isolated from tadpoles during early and late developmental stages, under normal and elevated levels of CO. Brainstems were either left intact or transected by removing the midbrain/pons. In late stage preparations, buccal burst pattern differed between intact and reduced preparations, and bursts were responsive to elevated CO in these reduced preparations. These results suggest the midbrain/pons affects tadpole buccal burst pattern and CO responsiveness, perhaps similar to its influences on lung ventilation.