Relationship between the distribution of the paired-like homeobox gene (Phox2b) expressing cells and blood vessels in the parafacial region of the ventral medulla of neonatal rats

► Phox2b-ir neurons in the ventral medulla may play a role in central chemoreception. ► We found that these Phox2b-ir neurons were located around capillary blood vessels. ► These neurons included CO2-sensitive parafacial preinspiratory neurons. ► Location of Phox2b-ir neurons may fit their physiological role of sensing blood CO2.