Hydrogen sulfide (H2S) is considered to be a new gaseous molecular alongside with NO and CO. It is produced mainly by cystathionine β-synthase (CBS) in brain. Lots of evidences indicate that H2S performs a wide range of physiological and pathological functions. However, the central cardiovascular effects of H2S are not fully identified. In present study, we tested the hypothesis that H2S in CNS may inhibit NADPH oxidase and decrease the production of reactive oxygen species (ROS), thus mediate central cardiovascular effects. Experiments were completed in Wistar-Kyoto (WKY,250g-300g) rats and spontaneous hypertensive rats (SHR, 250-300g). We used immunohistochemistry method to observe the expression of CBS in rostral ventrolateral medulla (RVLM) of both SHR rats and WKY rats. Artifcial cerebrospinal fluid, NaHS ( the H2S donor),or Apocynin (an inhibiter of NADPH oxidase) was given through a cannula implanted into the lateral cerebral ventricle, and mean arterial blood pressure(MAP)and heart rate (HR) were recorded. Lucigenin-enhanced chemiluminescence was used to estimate the level of ROS and the activity of NADPH oxidase in RVLM of rats in each group. One-way ANOVA was used for data stastistics. The following observations were made:1) Expressions of CBS of RVLM were increased in WKY rats compared with SHR rats(P<0.05, n=5). 2) Intracerebroventricular (ICV) infusion NaHS (4nmol/10μl ),or Apocynin (100nmol/10μl )significantly decreased MAP and HR in SHR rats.(P<0.05 both, n=6). 3) The level of ROS and the activity of NADPH oxidase in RVLM of SHR control group was higher than the level in WKY control group(P<0.05, n=8), and after infusion with NaHS (4nmol/10μl) or Apocynin (100nmol/ 10μl ) , the level of ROS and activity of NADPH oxidase was decreased in SHR rats compared with that in SHR controls(P<0.05, n=8). The results of present study suggest that H2S in central nervous system could decrease blood pressure and heart rate in SHR rats by inhibiting the activity of NADPH oxidase in the RVLM in SHR. Key words: Hydrogen sulfide; ROS; SHR; NADPH oxidase; RVLM