Toosendanin, a triterpenoid derivative, increases Ca2+ current in NG108-15 cells via L-type channels

Toosendanin, a triterpenoid derivative extracted from Melia toosendan Sieb et Zucc, was demonstrated to be a selective presynaptic blocker and an effective antibotulismic agent in previous studies. Here, we observed its effects on Ca(2+) channels in NG108-15 cells by whole-cell patch-clamp recording. Obtained data showed that toosendanin concentration dependently increased the high-voltage-activated (HVA) Ca(2+) current with an EC(50) of 5.13 microM in differentiated NG108-15 cells. The enhancement effect was still observed when the cells were pretreated with 5 microM omega-conotoxin MVIIC. However, when the cells were preincubated with 5 microM nifedipine or 10 microM verapamil-containing solution, the effect was absent. In undifferentiated NG108-15 cells, which only express T-type Ca(2+) channels, toosendanin did not affect Ca(2+) currents. These results show that toosendanin increases Ca(2+) influx in NG108-15 cells via L-type Ca(2+) channels.