Carbon monoxide contributes to the constipating effects of granisetron in rat colon

Figure 2 Effect of in vivo administration of zinc protoporphyrin alone and with granisetron on the time to first defecation. Zinc protoporphyrin (ZnPPIX) (50 μg/kg) did not affect the time to first defecation. Co-administration of ZnPPIX (50 μg/kg) with granisetron (G) (25, 50, 75 μg/kg) abolished the effect of G on its own. Friedman’s test = 10.486, P = 0.033; post-hoc comparisons: ZnPPIX vs vehicle: P = 1; G 25 μg/kg + ZnPPIX vs vehicle: P = 1; G 50 μg/kg + ZnPPIX vs vehicle: P = 1; G 75 μg/kg + ZnPPIX vs vehicle: P = 0.132. Each point represents an individual observation.