Abstract: As the key structure of excitability in biological systems, the voltage-gated sodium channel is targeted by a series of neurotoxins derived from plants. Celangulin Ⅳ and Ⅴ isolated 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. Their effects on inward sodium channel current in nerve cells of cotton bollworm Helicoverpa armigera were investigated in vitro by using patch clamp technique. The results indicated that celangulin Ⅳ reduced tetrodotoxin (TTX)-sensitive inward sodium current in a concentration dependent manner. The sodium peak current was reduced immediately in high concentration  (10 and 1 μmol/L), and decreased slowly in middle concentration （0.1 μmol/L）. In low concentration（0.01 μmol/L）,  however, the peak current was increased in the beginning, and then reduced. Moreover, it had no effect on activated voltage, but the peak voltage shifted to positive potential which was dependent on the concentration of celangulin Ⅳ. After treatment with celangulin Ⅴ, the TTX-sensitive inward sodium channel current was increased distinctly in a concentration dependant manner. It had no effect on activated voltage, but the peak voltage shifted to positive potential in lower concentration (0.1 and 0.01 μmol/L) of celangulin Ⅴ. Due to their chemical structure difference, celangulin Ⅳ and Ⅴ could result in qualitatively divergent kinetics of sodium channels at a shared binding site, so their physiological effects are different.

Key words: Helicoverpa armigera, botanical insecticide, celangulins, voltage-gated sodium channel, patch clamp of whole cell