Characterization of a novel Ca2+‐activated Cl channel activator.

Abstract

Nelumbinis Semen is a traditional medicine that has been used for hundreds of years in East‐Asia. Nelumbinis Semen is used to treat insomnia, anxiety and women's post‐menstrual‐pause depression. In this study, the signal transduction mechanism of Nelumbinis Semen was investigated in Xenopus oocytes using two‐electrode voltage‐clamp technique. Nelumbinis Semen produced a large outward current at membrane potentials more positive than −20 mV when it was applied to the exterior of oocytes, but not when injected intracellularly. The effect of Nelumbinis Semen was concentration‐dependent and reversible. The effect of Nelumbinis Semen was completely blocked by bath application of the Ca2+‐activated Cl− channel blocker niflumic acid and by intracellular injection of the calcium chelator BAPTA or the IP3 receptor antagonist heparin. Moreover, the effect was partially blocked by bath‐applied U‐73122, a phospholipase C (PLC) inhibitor and by intracellularly injected GTPγS, a non‐hydrolyzable GTP analogue. Whereas, it was not altered by pertussin toxin (PTX) pretreatment. These results indicate that interaction of Nelumbinis Semen with membrane component at the extracellular side leads to Ca2+‐activated Cl channel opening and this process involves PLC activation, the release of Ca2+ from the IP3‐sensitive intracellular store and PTX‐insensitive G protein activation.This work was supported by the Korea Science and Engineering Foundation (KOSEF) grant funded by the Korea government(MEST) (No. 2009‐0063466).