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THE ORIGIN OF THE MUSCLE FASCICULATION CAUSED BY FUNNEL‐WEB SPIDER VENOM
Author(s) -
Gage Peter W,
Spence Ian
Publication year - 1977
Publication title -
australian journal of experimental biology and medical science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.999
H-Index - 104
eISSN - 1440-1711
pISSN - 0004-945X
DOI - 10.1038/icb.1977.44
Subject(s) - fasciculation , tetrodotoxin , chemistry , anatomy , neuromuscular junction , biophysics , venom , medicine , pharmacology , neuroscience , biology , biochemistry
Summary The origin of the fasciculation of skeletal muscle produced by funnel‐web spider venom (FSV) has been examined in mouse phrenic nerve hemi‐diaphragm preparations. FSV from male spiders at concentrations greater than 10 −6 g/ml invariably produced muscle fasciculation which could be prevented by d‐tubocurarine (14μM), tetrodotoxin (0·3 μM) or by increasing the external magnesium concentration or calcium concentration. Diphenylhydantoin (3·6 × 10 −5 M) was able to reduce these fasciculations in some experiments. In curarized preparations, multiple end plate potentials (EPPs) in response to single stimuli and bursts of spontaneous EPPs were seen in the presence of FSV (10 −5 g/ml). Extracellular recordings from phrenic nerves in the presence of FSV (10 −1 g/ml) revealed additional components in compound action potentials elicited by single stimuli, and “spontaneous” electrical activity was observed in unstimulated nerves. This spontaneous activity was abolished by raising the divalent cation concentration in the bathing solution. These results suggest that a primary site of action of FSV is the surface membrane of nerve fibres and that muscle faseiculation arises as a consequence of spontaneous action potentials produced by the venom in motor nerves.