Fig. 1

Level of the transverse section used for the optical recordings (e.g., Fig. 2) and Phox2b immunoreactive cells in the most rostral medulla. a Phox2b immunoreactivity (Alexa Fluor 546). An arrow denotes a Phox2b cell cluster in the ventral parafacial region. b A NeuroTrace (435/455 blue fluorescence, Invitrogen) for Nissl staining. c A merged view of a and b. d A ventral view of a brainstem-spinal cord preparation. The preparation was cut at the level of the dotted line. AICA anterior inferior cerebellar artery, FN facial nucleus, pFRG parafacial respiratory group, preBötC pre-Bötzinger complex, VII–XII cranial nerves, C4 the fourth cervical ventral root, D dorsal, M medial. At the level of the most rostral medulla, close to the rostral end of the facial nucleus, Phox2b-ir cells formed one of the highest density clusters in the limited region ventrolateral to the facial nucleus. The cell density of the cluster was high enough to be clearly recognized, even in the Nissl-stained preparations (b)