Philanthotoxins: A review of the diversity of actions on synaptic transmission

The venom of the wasp Philanthus triangulum causes paralysis in insects. Although the wasp stings its natural prey (the worker of the honeybee) in the direction of the thoracic ganglia, the venom affects synaptic transmission in both the insect CNS and the neuromuscular system. The venom contains two agonists, O-acetylcholine and glutamate, and three antagonists of low molecular wight ( beta -, gamma - and delta -philanthotoxin). the beta - and delta -toxins have been purified and chemically characterised (mol. wt 243 and 435, respectively). It is suggested that the efficacy of the venom of this wasp arises from a synergistic action of the agonists and antagonists. In the insect CNS, the channel block by the delta -toxin may be facilitated by channel opening because of a high concentration of O-acetylcholine, while in the skeletal muscle of insects, the channel block by the delta -toxin may be facilitated by the inhibition of re-uptake of glutamate.