Studies On The Action Mechanisms Of CelangulinⅣ, Ⅴ And Interaction Of Their Mixture

Celangulin IV and celangulin V isolated from the root bark of the plant Celastnis angulatus are the major active ingredients of this botanical insecticide. Studies on the effects of celangulin IV , celangulin Vand their mixture on insect nerve-muscular junction glutamate potential and nerve cell voltage-gated sodium channel (VGSC) have been carried out for the Ph. D. Dissertation. The main results are as fellows.1. The toxicity interaction of the different ratio mixture of celangulin IV and V has been examined by means of the leaf disk method against armyworm (Mythimna separata ) larvae. The bioassay results showed that the insecticidal efficacy of celangulin V against armyworm larvae was synergied by celangulin IV, but celangulin V has no synergistic effects on the narcotic efficacy of celangulin IV. On the basis of the results, "interaction ratio" which might be used to evaluate the toxicity interaction of the mixture of several insecticides with different symptom guideline was put forward.2. The intracellar microelectrode recording was carried out on the ventral longitudinal body-wall muscle fibers of the third-instar larvae of Drosophila melanogaster. The results indicated that celangulin IV could decreased the spontaneous firing frequency. But, when the neuromuscular preparation was treated with celangulin V, the frequency of spontaneous potentials increased, then decreased. In the same time, the distinctly repetitive burst discharging of spontaneous firing was recorded in some preparation. The effects of celangulin IV and V on neuromuscular excitatory junction potentials (EJPs) of Drosophila larvae were gradually restrained and finally blocked. The blocking time had some relativity with the concentration of celangulin IV and V. The results also indicated that the effects of the mixture of celangulin IV and V on EJPs of Drosophila larvae, inwhich celangulin IV had high ratio of the mixture, were as same as that of celangulin IV. The blocking time of EJPs was delayed by the mixture of celangulin IV and V in which celangulin V had high ratio of the mixture. In conclusion, celangulin IV and V could have different effects on glutamate potential of insect synapses.3. The effects of celangulin IV and V on inward sodium channel current (Ina) in cultured nerve cell of cotton bollom (Helicoverpa armigerd) were investigated by patch champ technique. Celangulin IV reduced TTX-sensitive inward sodium current in a concentration and time dependent manner. In other words, the sodium peak current was reduced immediately in high concentration (10~5 and 10~6mol/L), and decreased slowly in middle concentration (10"7mol/L) . But in low concentration (10~8mol/L), the peak current was increased in the beginning, and then reduced. The results also showed that celangulin IV had no effects on activated voltage, but the peak voltage shifted to positive potential which depending on the concentration of celangulin IV. After celangulin V treated, the TTX-sensitive inward sodium channel current was concentration-depentant increased distinctly in some extent. The peak time was shorted and the inactivation time constant was decreased. Celangulin V had no effects on activated voltage, but the peak voltage shifted to positive potential in lower concentration of celangulin V.4. The study of different ratio mixture of celangulin IV and V on inward sodium channel current (lua) in cultured nerve cell of cotton bollom demonstrated that their effects corresponded with the concentration rate of each. When the concentration rate of celangulin IV in the mixture was high, VGSC was blocked and inward sodium current was reduced. When the concentration rate of celangulin V in the mixture was high, VGSC was activated and inward sodium current was increased. It is assumed that celangulin IV and V could have a same binding site of VGSC and they might be competed to bind the binding site each other. The competition is an antagonist on VGSC 0...