Action of the polyamine beta-philanthotoxin on neuromuscular transmission in insects.
The beta-fraction of the venom of the solitary wasp Philanthus triangulum inhibited glutamate-induced potentials in muscle fibres of the locust in a dose-dependent manner (50% block at 2 micrograms/ml). Single channel behaviour and miniature excitatory postsynaptic currents were not affected. The blocking effect disappeared after treatment of the muscle with the lectin concanavalin A which prevents desensitization of glutamate receptors. Block of potentials induced by iontophoretic application of glutamate was strongly dependent on the frequency of stimulation: no block occurred at stimulus intervals of 30 sec or more. The nature of this inhibition is discussed and proposed to be a delay of recovery from desensitization.
D000818:Animals; D001514:Bee Venoms / Q000494:pharmacology*; D003208:Concanavalin A / Q000494:pharmacology; D005971:Glutamates / Q000502:physiology*; D018698:Glutamic Acid; D006110:Grasshoppers / Q000502:physiology*; D007473:Ion Channels / Q000187:drug effects; D007478:Iontophoresis; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D009451:Neuroeffector Junction / Q000187:drug effects* / Q000502:physiology; D011073:Polyamines; D009435:Synaptic Transmission / Q000187:drug effects; D014862:Wasp Venoms / Q000494:pharmacology*
D001514:Bee Venoms; D005971:Glutamates; D007473:Ion Channels; D011073:Polyamines; D014862:Wasp Venoms; D003208:Concanavalin A; D018698:Glutamic Acid; C048056:beta-philanthotoxin