Abstract: Celangulin Ⅳ and Ⅴ from the root bark of Celastrus angulatus are the major active ingredients of the insecticidal plant which can result in reverse nerve poisoning symptoms, i.e., narcosis and excitation, respectively. The insecticidal efficacy of celangulin Ⅴ can be synergied by celangulin Ⅳ, but celangulin Ⅴ has no synergistic effects on the narcotic efficacy of celangulin Ⅳ. By using patch-clamp technique, the interaction of celangulin Ⅳ and Ⅴin different ratio (3∶1, 1∶1, 1∶3) mixtures on tetrodotosin (TTX)-sensitive inward sodium channel current (I_Na) in cultured nerve cell of cotton bollworm (Helicoverpa armigera)was investigated. The results showed that the effects corresponded with the ratio of celangulin Ⅳ and Ⅴ in a mixture. When the ratio of celangulin Ⅳ in a mixture was high, voltage gated sodium channel (VGSC) was blocked and TTX-sensitive I_Na was decreased. When the ratio of celangulin Ⅴ in a mixture was high, VGSC was activated and TTX-sensitive I_Na was increased. Different ratio mixtures of celangulin Ⅳ and Ⅴ showed no effect on activated voltage, except the peak voltage shifted to positive potential 10-20 mV. The results suggest that celangulin Ⅳ and Ⅴ share a binding site of VGSC or they bind to separate sodium channel sites which interact altosterically with each other, and they might antagonistically compete each other  to bind the site on VGSC.

Key words: Botanical insecticides, Helicoverpa armigera, celangulin, voltage-gated sodium channel, whole-cell patch clamp, antagonism