Usage of the fruit and bark of a Melia-family plant as a digestive tract-parasiticide and agricultural insecticide was recorded about two thousant years ago in ancient China. Toosendanin (TSN), a triterpenoid, is an effectual ingredient extracted from the plant. Studies have demonstrated that TSN selectively affects neurotransmitter release, effectively antagonizes botulism, induces cell differentiation and apoptosis and inhibits proliferation of various human cancer cells, inhibits feeding and dovelopment in insects and modifies K⁺- and Ca²⁺-channel activity. The research data to demonstrate that TSN inhibits K⁺-channel and facilitates L-type Ca²⁺-channel are summarized, and the mechanism of action of TSN is discussed.