Effects of the Herbal Medicines on Voltage‑Dependent K+ 2 Channels

Objective: The aim of this study was to evaluate whether herbal medicines, such as the fruit of Schisandra chinensis (SCF), Atractylodes macrocephala Koidzumi (AMK), Poria cocos Wolf (PCW), Citrus unshiu peel (CUP), Magnolia officinalis Bark (M. officinalis), Alisma canaliculatum (A. canaliculatum), Rehmanniae Radix (RR), and Corni fructus (C. fructus), modulate Kv2 channels and cause insulin secretion. Materials and Methods: We used the whole‑cell patch‑clamp technique to analyze the effect of these herbal medicines on Kv channels. In addition, human embryonic kidney 293 cells overexpressing Kv2.1 and Kv2.2 channels were used to confirm the role of Kv2 channels. Results: SCF, AMK, PCW, CUP, M. officinalis, A. canaliculatum, and RR inhibited Kv2.1 channel currents in a concentration‑dependent manner (100–500 μg/mL). However, C. fructus had no effects on Kv2.1 channel currents. In addition, SCF, AMK, M. officinalis, and A. canaliculatum inhibited Kv2.2 channel currents in a concentration‑dependent manner, but PCW, CUP, and RR had no effects on Kv2.2 channel currents. Furthermore, RR, CUP, and PCW increased insulin secretion. Conclusion: These findings suggested that the herbal medicines, RR, CUP, and PCW, are potential novel agents for the prevention and treatment of diabetes.