Involvement of Potassium Channels, Nitric Oxide Synthase, and Guanylate Cyclase in the Spasmolytic Effect of Simaba ferruginea A.St.-Hil on Rat Isolated Ileum

Background and Aim Simaba ferruginea A.St.-Hil. Popularly known as “calunga,” is a typical Brazilian cerrado plant whose rhizomes are popular for treating diarrhea. Aims The aim of this study was to evaluate the spasmolytic activity and the antidiarrheal effect of the ethanolic extract obtained from S. ferruginea (Sf-EtOH). Methods Ileal segments (1–2 cm) from male Wistar rats were mounted in isolated organ baths and connected to a force transducer, and then to an amplifier which was connected to a computer (AVS Projetos/São Paulo-SP). After stabilization for 60 min, under tension (1 gf), two submaximal contractions were induced with KCl 40 mM or carbachol 10 −6 M on ileal segments. During the third tonic and sustained contraction, Sf-EtOH was added in cumulative concentrations to the organ bath. Incubations with L-NAME (10 −4 M), ODQ (10 −5 M), TEA + (5 or 1 mM), glibenclamide (10 −5 M), or apamine (100 nM) were prepared ( n = 5), separately and used to verify the involvement of the nitric oxide synthase, guanylate cyclase, and potassium channels in the relaxing effect. The results were expressed as mean ± standard error of the mean and were statistically evaluated using one-way ANOVA followed by Bonferroni test, when necessary * p