Rikkunshito acts in synergy with forskolin to enhance cAMP levels in PC12 cells. PC12 cells were treated with forskolin alone or in combination with rikkunshito for 30 min. cAMP levels are shown as total amounts for cells plated in individual wells of 24-well plates. Data are presented as the mean ± SEM of triplicate independent experiments. *, p < 0.05 vs. 0% rikkunshito at each forskolin concentration tested, two-tailed Student’s t-test.