川楝素对粘虫幼虫拒食作用的电生理学研究

ELECTROPHYSIOLOGICAL STUDY OF THE ANTIFEEDANT ACTION OF TOOSENDANIN TO THE ARMYWORM LARVAE

1×10^(-4)g/ml川楝素溶液能诱发记录到粘虫(Mythimna separata)幼虫下颚瘤状体栓锥感器的传入发放。其发放频率有一个逐步发展的过程,并可引起几个感受器细胞的爆发性发放。若用1×10^(-4)g/ml川楝素溶液处理栓锥感器,则经过一段时间后,能抑制粘虫幼虫侧栓锥感器对10mmol/L蔗糖和中栓锥感器对50mmol/L肌醇的诱发反应。用二硫苏糖醇及川楝素的混合液处理上述感器,则能解除川楝素的抑制效应。对川楝素作为拒食剂对昆虫化学感受器的可能作用方式作了初步探讨。对其拒食效应与活乐木醛作了比较。

Preliminary behavioural experiments on armyworm larvae (Mythimna separata Walker) have shown that toosendanin, a triterpenoid from the chinaberry tree Melia toasendan S. et Z., is a strong antifeedant. In this paper the effect of toosendanin on the lateral and medial maxillary sensilla styloconica of the armyworm larvae was investigated with electrophysiological method. Glass capillaries of about 30 jim tip diameter were used as stimulatory----recording electrodes. Isolated maxillae of the last instar Larvae were user). The senssillum exposed to 1×10-4 g/ml toosendanin produced'a very weak response at first, after a latent period of several seconds ii mticascd ui uiscliaigcs, and at about I minute it produced a transient bursting discharges in several receptor ceils, and then gradually calmed down. During the one hour observation the above sequence repeated at about every 10 mimiies, Aftt-r 5 treatments (each H minutes) with 1×10-4g/ml toosendanin, the response of the lateral srnsilla to 10 mM suerose reduced to about 1/5~1/8 of its orginal level. After stopping treatment with toosendanin, i could gradually recover to about 80 per cent in 40 minutes After 4 treatments, the response of the medial sensilla to 50 mM inositol dropped to 1/2-1/3 of its initial level, but no sign of recovery was seen during the ensuing 40 minutes;. The inhibitory effect of toosendanin was completely abolished by treatments with a mixture of equal volume of 2×10-4 g/ml toosendanin and 1 mM dithiothreitol.The experiment results showed that toosendanin as an .uitifetndant conformed to a mode of action very similar to that of warburganal. A comparison between this two substances is discussed.