Figure 3.

Effects of inhibitors of carbon monoxide (CO) and hydrogen sulfide synthesis on relaxations of the internal anal sphincter. Relaxations to electrical field stimulation (EFS) were examined after removal of the contractile components of responses with guanethidine (10 μM), atropine (1 μM), and α,β-mATP (10 μM). Responses were obtained at (A) 5 Hz and (B) 10 Hz in the absence and presence of the HO inhibitor zinc protoporphyrin IX (ZnPPX; 10 μM) and/or inhibitors of the hydrogen sulfide (H₂S) synthesizing enzymes, propargylglycine (PAG; 1 mM), and aminooxyacetic acid (AOAA; 30 μM). Mean responses (± SEM, n = 5–10) are expressed as a percentage of the control pre-drug response to EFS. **P < 0.01, ***P < 0.001 compared to control values in the absence of inhibitors of CO and H₂S synthesis.