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 Ca2+ channels in NG108-15 cells by whole-cell patch-clamp recording. Obtained data showed that toosendanin concentration dependently increased the high-voltage-activated (HVA) Ca2+ current with an EC50 of 5.13 muM in differentiated NG108-15 cells. The enhancement effect was still observed when the cells were pretreated with 5 muM omega-conotoxin MVIIC. However, when the cells were preincubated with 5 muM nifedipine or 10 muM verapamil-containing solution, the effect was absent. In undifferentiated NG108-15 cells, which only express T-type Ca2+ channels, toosendanin did not affect Ca2+ currents. These results show that toosendanin increases Ca2+ influx in NG108-15 cells via L-type Ca2+ channels. (C) 2004 Elsevier Ireland Ltd and The Japan Neuroscience Society. All rights reserved.