Neuromuscular effects of fractions isolated from the venom of the Thailand cobra, Naja naja siamensis

P. Teerapong, A. L. Harvey, T. Barkas

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2 Citations (Scopus)

Abstract

Four fractions (α, β, γ and δ) were isolated from the venom of the Thailand cobra, Naja naja siamensis by ion-exchange chromatography. Each fraction was tested for activity on the isolated chick biventer cervicis nerve-muscle preparation. Fractions α, β and γ inhibited neuromuscular transmission by blocking acetylcholine receptors, but had no direct action on muscle contractility. Fraction α produced neuromuscular blockade in about 30 min when added at a concentration of 1 μg/ml, and was about 100 times more potent than fractions β and γ. The blockade of indirect stimulation was apparently irreversible, although the responses to acetylcholine and carbachol recovered to about 50% after 4 hr. Fraction δ produced contracture of the muscle followed by blockade of responses to both direct and indirect stimulation. The effects of fraction δ could be inhibited by raising the calcium concentration of the bathing solution; on return to normal calcium concentration the effects of fraction δ also returned. It is concluded that fractions α, β and γ are postjunctional "neurotoxins" and that fraction δ contains a "cardiotoxin" which may act by displacing calcium from membranes.

Original languageEnglish
Pages (from-to)551-560
Number of pages10
JournalToxicon
Volume16
Issue number6
DOIs
Publication statusPublished - 1 Jan 1978

Keywords

  • acetylcholine
  • alpha bungarotoxin
  • carbachol
  • cholinergic receptor
  • neostigmine
  • snake venom
  • tubocurarine chloride
  • animal experiment
  • chicken
  • muscle
  • neuromuscular synapse
  • neuromuscular transmission
  • peripheral nervous system
  • reptile

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