[Orientotoxin--a new presynaptic neurotoxin from the venom of the giant hornet Vespa orientalis].

Orientotoxin, a novel presynaptically acting neurotoxin from the venom of giant hornet Vespa orientalis, has been isolated by gel filtration and ion exchange chromatography and characterized. The toxin has a molecular mass of 18,000. Highly purified preparations of orientotoxin possessed clearly manifested lysophospholipase activity and can block both induced and spontaneous release of neurotransmitter from the presynaptic nerve membrane.