カイコの味覚細胞のDDT感受性

概要

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Afferent impulses from the contact chemoreceptors were observed following the direct contact application of DDT to the tip of the chemosensory hairs on the maxilla of silkworm larva. No chemosensory neurons were activated directly by DDT itself. Pretreatment with relatively low concentration of DDT increased the frequency of impulse discharges evoked by chemical stimulation, indicating increased sensitivity to the chemical. At the concentrations of DDT higher than a certain critical level, trains of impulses which are characteristic of nervous symptoms of DDT poisoning appeared in place of single spikes after a certain latent peroid (about 2 min.). At much higher concentrations, the amplitude of the train of impulses extremely decreased and finally the response disappeared. In rare cases increased negative after-potential was recorded. A small difference in susceptibility to DDT was observed among the maxillary chemoreceptors. The chemoreceptors were more susceptible to DDT at lower temperatures than higher temperatures. When an appearance of trains of impulses in the inositol receptor was taken as a criterion of the symptom of DDT poisoning, there was a small difference in susceptibility to DDT among about 30 silkworm strains tested. However, no correlation was found between the susceptibility of the receptor shown by ED_50 and the torelance of whole-larvae shown by LD_50 per body weight which was obtained in the topical application test.
1967-09-25