Increase of evoked release of acetylcholine at the neuromuscular junction by a fraction from the venom of the Eastern green mamba snake (Dendroaspis angusticeps)

A. L. Harvey, P. W. Gage

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

The effects of a fraction (DA3) isolated from the venom of the Eastern green mamba, Dendroaspis angusticeps, were tested in the toad sartorius muscle-sciatic nerve preparation using intracellular recording techniques. In magnesium-paralysed preparations, DA3 (0·5μg/ml and above) caused a slow, progressive increase in the quantal content of the endplate potential (e.p.p.); the largest increase measuring 40 times the control value. DA3 also altered the spontaneous release of acetylcholine, firstly reducing the frequency of miniature e.p.p.s (m.e.p.p.s) to 20-50% of control and then increasing the frequency to about four times control. In the presence of the toxin, very large spontaneous e.p.p.s were seen. Such potentials could be 10 times the amplitude of control m.e.p.p.s although their time course was similar to that of control m.e.p.p.s. In the absence of external Ca2+ ions and in the presence of 1 mM EGTA, DA3 still produced the biphasic change in m.e.p.p. frequency and the appearance of large spontaneous e.p.p.s. We conclude that DA3 increases the amount of acetylcholine released by each nerve stimulation, possibly by inducing the clumping of synaptic vesicles.

LanguageEnglish
Pages373-381
Number of pages9
JournalToxicon
Volume19
Issue number3
DOIs
Publication statusPublished - 1 Jan 1981

Fingerprint

Elapidae
Snakes
Neuromuscular Junction
Venoms
Acetylcholine
Synaptic Vesicles
Egtazic Acid
Sciatic Nerve
Anura
Magnesium
Ions
Muscles
Muscle

Keywords

  • acetylcholine
  • egtazic acid
  • calcium
  • magnesium
  • snake venom
  • animal experiment
  • endplate potential
  • in vitro study
  • neuromuscular synapse
  • peripheral nervous system
  • sartorius muscle
  • sciatic nerve

Cite this

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title = "Increase of evoked release of acetylcholine at the neuromuscular junction by a fraction from the venom of the Eastern green mamba snake (Dendroaspis angusticeps)",
abstract = "The effects of a fraction (DA3) isolated from the venom of the Eastern green mamba, Dendroaspis angusticeps, were tested in the toad sartorius muscle-sciatic nerve preparation using intracellular recording techniques. In magnesium-paralysed preparations, DA3 (0·5μg/ml and above) caused a slow, progressive increase in the quantal content of the endplate potential (e.p.p.); the largest increase measuring 40 times the control value. DA3 also altered the spontaneous release of acetylcholine, firstly reducing the frequency of miniature e.p.p.s (m.e.p.p.s) to 20-50{\%} of control and then increasing the frequency to about four times control. In the presence of the toxin, very large spontaneous e.p.p.s were seen. Such potentials could be 10 times the amplitude of control m.e.p.p.s although their time course was similar to that of control m.e.p.p.s. In the absence of external Ca2+ ions and in the presence of 1 mM EGTA, DA3 still produced the biphasic change in m.e.p.p. frequency and the appearance of large spontaneous e.p.p.s. We conclude that DA3 increases the amount of acetylcholine released by each nerve stimulation, possibly by inducing the clumping of synaptic vesicles.",
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N2 - The effects of a fraction (DA3) isolated from the venom of the Eastern green mamba, Dendroaspis angusticeps, were tested in the toad sartorius muscle-sciatic nerve preparation using intracellular recording techniques. In magnesium-paralysed preparations, DA3 (0·5μg/ml and above) caused a slow, progressive increase in the quantal content of the endplate potential (e.p.p.); the largest increase measuring 40 times the control value. DA3 also altered the spontaneous release of acetylcholine, firstly reducing the frequency of miniature e.p.p.s (m.e.p.p.s) to 20-50% of control and then increasing the frequency to about four times control. In the presence of the toxin, very large spontaneous e.p.p.s were seen. Such potentials could be 10 times the amplitude of control m.e.p.p.s although their time course was similar to that of control m.e.p.p.s. In the absence of external Ca2+ ions and in the presence of 1 mM EGTA, DA3 still produced the biphasic change in m.e.p.p. frequency and the appearance of large spontaneous e.p.p.s. We conclude that DA3 increases the amount of acetylcholine released by each nerve stimulation, possibly by inducing the clumping of synaptic vesicles.

AB - The effects of a fraction (DA3) isolated from the venom of the Eastern green mamba, Dendroaspis angusticeps, were tested in the toad sartorius muscle-sciatic nerve preparation using intracellular recording techniques. In magnesium-paralysed preparations, DA3 (0·5μg/ml and above) caused a slow, progressive increase in the quantal content of the endplate potential (e.p.p.); the largest increase measuring 40 times the control value. DA3 also altered the spontaneous release of acetylcholine, firstly reducing the frequency of miniature e.p.p.s (m.e.p.p.s) to 20-50% of control and then increasing the frequency to about four times control. In the presence of the toxin, very large spontaneous e.p.p.s were seen. Such potentials could be 10 times the amplitude of control m.e.p.p.s although their time course was similar to that of control m.e.p.p.s. In the absence of external Ca2+ ions and in the presence of 1 mM EGTA, DA3 still produced the biphasic change in m.e.p.p. frequency and the appearance of large spontaneous e.p.p.s. We conclude that DA3 increases the amount of acetylcholine released by each nerve stimulation, possibly by inducing the clumping of synaptic vesicles.

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