FIGURE 7.

The effect of peppermint oil on neural-mediated inhibitory responses under non-adrenergic non-cholinergic (NANC) conditions in the circular muscle. Representative mechanical recordings show the relaxation (during the electrical field stimulation) and the off-contraction (rebound after the electrical field stimulation) in control (CTRL) conditions (left) and in the presence of peppermint oil 1,000 μg/mL (right) (A). Graphs show the effect of peppermint oil on electrical field stimulationtrains of increasing voltage (8, 10, and 20 V) on the relaxation and the off-contraction (B). Two-way ANOVA (voltage x treatment) was performed to assess the response of peppermint oil compared to the control in the on-relaxation (treatment p > 0.05) and the off-contraction (treatment p < 0.0256). Tukey’s post hoc test was done to compare the effect of peppermint oil with control in the off-contraction, *p < 0.05, **p < 0.01. The relaxation was normalized (i.e., 100%) to the basal AUC before electrical field stimulation. The off-contraction was normalized (i.e. 100%) to the maximum response obtained with a stimulus of 20 V in control conditions. The reduction of the off-contraction (%) was calculated through a linear regression where Y represents the Off-response reduction and X is the slope of the linear regression. The IC₅₀ of this effect was about 100 μg/mL. Data were expressed as mean ± SEM.