A. Schematic anatomical representation of medullary brainstem nuclei of the respiratory central pattern generator in relation to the position of the transections 1.5 and 2mm caudal to obex. pre-BötC, pre-Bötzinger complex; rVRG, rostral ventral respiratory group; cVRG, caudal ventral respiratory group; NRA, nucleus retroambiguus; NTS, nucleus of the solitary tract; AP, area postrema, XII, hypoglossal nucleus; PN; phrenic motoneurons. B. Photograph illustrating the anatomical location of the transections in a perfused brainstem preparation.