Role of central hydrogen sulfide on ventilatory and cardiovascular responses to hypoxia in spontaneous hypertensive rats.

Central hydrogen sulfide (H2S) has been reported to act as a gaseous neuromodulator involved in the ventilatory and cardiovascular control of normotensive rats, whereas no information is available in spontaneously hypertensive rats (SHR). We recorded minute ventilation (VE), mean arterial pressure (MAP) and heart rate (HR) before and after blocking of enzyme Cystathionine β-synthase (CBS) producing H2S in neural tissue by microinjection of aminooxyacetate (inhibitor of CBS) into the fourth ventricle of Wistar normotensive rats (WNR) and SHR followed by 30min of normoxia (21% inspired O2) or hypoxia (10% inspired O2) exposure. Microinjection of AOA or saline (1μL) did not change VE, MAP and HR during normoxia in both WNR and SHR. In WNR, hypoxia caused an increase in VE, HR and a decrease in MAP and these responses were unaltered by AOA. In SHR, hypoxia produced a higher increase of VE, and decrease in MAP and HR when compared to WNR, and these responses were all blunted by AOA. In conclusion, endogenous H2S plays important modulatory roles on hypoxia-induced ventilatory and cardiovascular responses, inhibiting the cardiovascular and stimulating the respiratory systems in SHR.