1-O-acetylgeopyxin A inhibits calcium influx via voltage-gated calcium channels in sensory neurons. a Differential interference contrast (DIC) and pseudocolored fluorescent images of DRG neurons treated with vehicle (1% DMSO), visualized for Fura2-AM before and after stimulations with KCl (40 and 90 mM) during Ca2+ imaging. Scale bar is 50 μm. b Average responses of sensory neurons incubated overnight with vehicle (control) or 20 μM of geopyxin A, 1-O-acetylmethylgeopyxin A, methylgeopyxin A, 1-O-acetylgeopyxin A and geopyxin C in response to 40 and 90 mM KCl (to trigger opening of low- and high voltage activated calcium channels) (n = 81 to 204 neurons from 3 separate rats). Incubation with 20 μM 1-O-acetylmethylgeopyxin A or methylgeopyxin A killed the cells. Asterisk indicate statistical significance compared with cells treated with vehicle (*P < 0.05, one-way ANOVA with Dunnett’s post hoc test). c chemical structure of 1-O-acetylgeopyxin A. Experimenter was blinded to the treatment condition. Unless otherwise noted, all data is mean ± S.E.M.