The mechanism of action of beta-bungarotoxin at the presynaptic plasma membrane.
The beta-bungarotoxin-induced depolarization of the synaptosomal plasma membrane monitored by the efflux of 86Rb+ is potentiated by raising the albumin in the incubation, is Ca2+-dependent and is due neither to inhibition of the (Na+ + K+)-dependent ATPase nor to activation of the voltage-dependent Na+ channel. Occupancy of the beta-bungarotoxin-binding site by dendrotoxin inhibits partially the action of beta-bungarotoxin. The efflux of 86Rb+ is parallelled by a release of lactate dehydrogenase from the synaptosome, and the two processes are maximal with 2 nM-toxin. Digitonin induces a release of 86Rb+ and lactate dehydrogenase closely similar to that seen with beta-bungarotoxin. It is concluded that the toxicity of beta-bungarotoxin for mammalian nerve terminals can be largely accounted for by specific site-directed phospholipase A2-induced permeabilization of the plasma membrane.
D000818:Animals; D002038:Bungarotoxins / Q000494:pharmacology*; D002413:Cations, Divalent / Q000494:pharmacology; D004072:Digitonin / Q000494:pharmacology; D004546:Elapid Venoms / Q000494:pharmacology; D006168:Guinea Pigs; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D010042:Ouabain / Q000494:pharmacology; D012709:Serum Albumin / Q000494:pharmacology; D013570:Synaptic Membranes / Q000187:drug effects / Q000378:metabolism*
D002038:Bungarotoxins; D002413:Cations, Divalent; D004546:Elapid Venoms; D012709:Serum Albumin; D010042:Ouabain; C020273:dendrotoxin; D007770:L-Lactate Dehydrogenase; D004072:Digitonin