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Biochemical and Electrophysiological Demonstrations of the Actions of β‐Bungarotoxin on Synapses in Brain
Author(s) -
Halliwell J. V.,
Tse C. K.,
Spokes J. W.,
Othman I.,
Dolly J. O.
Publication year - 1982
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1982.tb03979.x
Subject(s) - tetrodotoxin , neurotransmission , phospholipase a2 , neurotoxin , acetylcholine , chemistry , phospholipase , toxin , biophysics , biochemistry , electrophysiology , phospholipase a , neuroscience , blockade , biology , pharmacology , enzyme , receptor
Homogeneous β ‐bungarotoxin interacts irreversibly with rat olfactory cortex and produces permanent inhibition of neurotransmission (half‐time of blockade for 230 n M toxin is 25 min). Binding occurs in the absence of divalent cations, but the rate of synaptic blockade is increased by Ca 2+ , which activates the intrinsic phospholipase A 2 activity of the toxin. Other observable actions of the toxin, seen with rat cerebrocortical synaptosomes, are an increase in the release of acetylcholine, glutamate and γ ‐aminobutyrate and impairment of transmitter uptake, which are all insensitive to tetrodotoxin. Inactivation of the toxin's phospholipase activity by chemical modification with p ‐bromophenacyl bromide diminishes the observed concomitant efflux of the neurotransmitters and lactate dehydrogenase. Collectively, the results support the idea that the toxin binds specifically and irreversibly to component(s) on nerve terminals and this together with the resultant phospholipolysis leads eventually to synaptic blockade. Such a proposal would account for the unique toxicity of the protein relative to phospholipase A 2 enzymes.