Purinergic transmission in the rostral but not caudal medullary raphe contributes to the hypercapnia-induced ventilatory response in unanesthetized rats

► The medullary raphe (MR) is an important site for central chemoreception. ► ATP signalling has been implicated in CO2/pH sensitivity. ► We have examined the role of P2X receptors in the MR on CO2 respiratory responses. ► PPADS into the rostral, but not caudal MR, decreased the ventilatory response to CO2. ► P2X receptors in the rostral MR play an excitatory role in hypercapnic chemoreflex.