Abstract: To investigate the effects of P2X receptor in the nucleus ambiguous (NA) on acute hypoxic ventilation. Methods Experiments were performed on anesthetized, immobilized and artificially ventilated rabbits. The peripheral chemo-reflex to hypoxia was elicited by ventilating the animals with 10％O₂balance 90％N₂. Changes in the peak amplitude and frequency of integrated phrenic nerve discharge were recorded. The ventilatory responses of the peripheral chemoreflex following microinjection within the NA of either P2X receptor agonist adenosine triphosphate (ATP) or antagonist pyridoxal-5′-phosphate-6-azo-phenyl-2, 4-disulfonate (PPADS) were observed. ResultsExcitation of the phrenic never discharge was induced by ventilating the animals with hypoxic mixed gases. Microinjection of ATP in NA increased the frequency of acute hypoxic respiration, whereas microinjection of PPADS partially blocked the respiratory effects of ATP microinjected into NA. ConclusionThe present results suggested that ATP acting via the P2X receptor in the NA may be involved in the respiration control of the acute hypoxic ventilatory response.

Key words: Nucleus ambiguous, P2X receptor, Respiration