Figure 5. Relaxation of the 5-hydroxytryptamine-preconstricted bronchial segments to increasing concentrations of halothane: control, after epithelial rubbing, after pretreatment with N^G-nitro-L-arginine (L-NNA), or after pretreatment with indomethacin. Halothane-mediated bronchodilation was significantly attenuated after epithelial rubbing (P < 0.01) or after pretreatment with L-NNA (P <0.05) or indomethacin (P < 0.001). Attenuation after L-NNA was significantly less than after indomethacin (P < 0.01). #P < 0.05 versus control. *P < 0.05 between L-NNA pretreatment and indomethacin pretreatment. (One minimum alveolar concentration of halothane in rats was considered 0.88%. [17])