[Effect of neurotoxins on mediator release from the motor nerve endings of the Drosophila melanogaster larva]

Abstract

Spontaneous miniature junctional potentials and induced by motor nerve stimulation junctional potentials were recorded in muscle fibres of the third instar Drosophila larvae. Presynaptically active neurotoxins isolated from the snake venoms (beta-bungarotoxin 4.5 x 10(-7) M, notexin and notechis-II-51 X 10(-7) M, Crotoxin 9 x 10(-8) M, phospholipase from the venom of cobra 4 x 10(-6) M did not induce any changes in transmitter release during 60--120 min of contact with Drosophila preparation, although these concentrations exceed those used in frog or mice preparations. On the contrary, bee venom phospholipase (1.25 x 10(-7) M) turned out to be even more active than in frog or mice junctions. A similar sequence of three phases of the presynaptic blocking effect was found: initial decrease followed by a period of increase and finally -- depression of both spontaneous and evoked release. Bee venom phospholipase was ineffective in Ca2+-free solution but its irreversible binding to nerve endings took place evidently in spite of Ca lack.