FIGURE 1.

Mitragynine and 7‐OH mitragynine depress respiration in awake mice. (a–c) Mitragynine (10–90 mg·kg⁻¹) but not 3 mg·kg⁻¹ significantly depressed minute volume (MV) when compared with effects of vehicle alone. There was no significant difference in the degree of depression induced by mitragynine over a similar dose range (10–90 mg·kg⁻¹). (d–f) 7‐OH mitragynine significantly depressed mouse MV at all doses in a dose‐dependent manner. (g–i) Morphine significantly depressed mouse MV at all doses in a dose‐dependent manner similar to 7‐OH mitragynine. N = 6 for all groups. All drugs administered by oral gavage dosing. In (c), (f) and (i), * P < 0.05, significantly different; ns, not significantly different, as indicated; one‐way ANOVA (Kruskal–Wallis) with Dunn's multiple comparison. See Table S1 for full test statistics