Effects of an isolated toxin from Australian Tiger snake (Notechis scutatus scutatus) venom at the mammalian neuromuscular junction

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Abstract
1 The acute effects of a purified toxin from Australian Tiger snake (Notechis scutatus scutatus) venom have been investigated at the mammalian neuromuscular junction. 2 The toxin was injected into the tail vein of mice. Death was due to respiratory paralysis. 3 The resting membrane potential, and action potential of muscle fibres in muscles from in vivo intoxicated animals were normal. 4 The frequency of miniature end plate potentials (m.e.p.p.s) from intoxicated nerve-muscle preparations was reduced, although m.e.p.p. amplitude was unaltered. 5 Nerve stimulation resulted in end plate potentials (e.p.p.s) of quantal amplitude; only rarely was the e.p.p. large enough to give rise to an action potential. 6 High (20 mm) K+ did not increase m.e.p.p. frequency in intoxicated preparations. 7 The toxin was largely ineffective in vitro. 8 The similarities and differences between this toxin, β-bungarotoxin and botulinum toxin are discussed.