Myotoxic and neurotoxic activity of Bacillus thuringiensis var. israelensis crystal toxin |
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| Authors: | Gur Jai Pal Singh Sarjeet S Gill |
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| Institution: | Division of Toxicology and Physiology, Department of Entomology, University of California, Riverside, California 92521 USA |
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| Abstract: | The mechanism of the entomocidal action of Bacillus thuringiensis var. israelensis (BTI) in Periplaneta americana has been studied. Cockroaches treated with the alkali-solubilized BTI crystal gradually became sluggish and immobile. A physiological examination of poisoned cockroaches indicated that BTI possessed both myotoxic and neurotoxic activity. Following hemocoel or foregut administration of BTI, myotoxic effects were observed within 10–20 min whereas the onset of neurotoxic effects was considerably delayed. The results of this study suggest that the myotoxic action of BTI is probably important for the initial manifestation of its toxicity. The neurotoxic effects of BTI were ascribed to its ability to interfere with transmitter release. BTI exerted a dual action on transmitter release in the cockroach sixth abdominal ganglion. At lower doses (2–4 μg/ml) BTI was found to suppress transmitter release by interfering with calcium uptake. At higher concentrations (12 μg/ml or higher), however, BTI caused blockage of synaptic transmission which was preceded by massive transmitter release. In either case, the synapse blocking action of BTI was probably due to its effects upon presynaptic terminals. Postsynaptic membranes and axons in the ventral nerve cord apparently remained unaffected. |
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| Keywords: | To whom correspondence should be addressed |
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