Hydrogen sulfide facilitates carotid sinus baroreflex in anesthetized rats

Aim: To study effects of hydrogen sulfide (H2S) on the carotid sinus baroreflex (CSB). Methods: The functional curve of the carotid sinus baroreflex was measured by recording changes in arterial pressure in anesthetized male rats with perfused carotid sinus. Results: H2S (derived from sodium hydrosulfide) at concentrations of 25, 50, and 100 mu mol/L facilitated the CSB, shifting the functional curve of the baroreflex downward and to the left. There was a marked increase in peak slope (PS) and reflex decrease in blood pressure (RD). Effects were concentration-dependent. Pretreatment with glibenclamide (20 mu mol/L), a K-ATP channel blocker, abolished the above effects of H2S on CSB. Pretreatment with Bay K8644 (an agonist of calcium channels; 500 mu mol/L) eliminated the effect of H2S on CSB. An inhibitor of cystathionine gamma-lyase (CSE), DL-propargylglycine (PPG; 200 mu mol/L), inhibited CSB in male rats and shifted the functional curve of the baroreflex upward and to the right. Conclusion: These data suggest that exogenous H2S exerts a facilitatory role on isolated CSB through opening K-ATP channels and further closing the calcium channels in vascular smooth muscle. Endogenous H2S may activate the activity of the CSB in vivo.