FIG. 1.

Example of recordings obtained in two rats showing the effect of intravenous H₂S infusion for 5 min on F_AH₂S (proportional to CgH₂S) at a dose producing no effect on breathing (4 μmol/min, upper panel) and at a level producing an apnea (8 μmol/min, lower panel). In the latter, the rat was mechanically ventilated. F_AH₂S, which was determined based on minute ventilation, F_EH₂S, and PaCO₂ (see the Materials and Methods section for determination) increased as a function of the levels of H₂S infused. Note the lack of a cardiovascular effect at the lowest infusion rate whereas at the highest level, F_AH₂S continues to rise until blood pressure starts to drop. Interruptions in the BP trace correspond to periods of blood sampling.