The effect of different toxins from scorpion venom on neuromuscular transmission and nerve action potentials in the crayfish

Abstract

1. The action of four different toxins from the venom of the scorpion Androctonus australis which have been previously purified and specified according to their fly larvae and isopod paralysis (insect and crustacean toxin) and mice lethality (mammal toxin I and II) have been tested on a nerve muscle preparation and on the giant axons of the crayfish Astacus leptodactylus. 2. With the exception of insect toxin all toxins (crustacean toxin, mammal toxin I and II) were active in the nerve muscle preparation. Crustacean toxin was 125, mammal toxin I 20–30 and mammal toxin II about 5 times more effective than crude venom. 3. The sequence of action in the nerve muscle preparation produced by the active toxins was: increase in ejp-amplitudes, evoked repetitive activity, spontaneous repetitive activity, partial block of the excitability of the axon. 4. At threshold concentrations no postsynaptic effects of the toxins were present. 5. In the giant axons crustacean toxin and mammal toxin I, but neither mammal toxin II nor insect toxin, caused great prolongations of the action potentials as well as oscillations in their plateau phases. 6. Concerning the specificity of the toxins only insect toxin can be regarded as selective.