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Differences between the effects of saxitoxin (paralytic shellfish poison) and tetrodotoxin on the frog neuromuscular junction
Author(s) -
EVANS M. H.
Publication year - 1969
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1969.tb07999.x
Subject(s) - saxitoxin , tetrodotoxin , sartorius muscle , neuromuscular junction , curare , anatomy , paralytic shellfish poisoning , chemistry , biophysics , neuroscience , biology , anesthesia , medicine , toxin , fishery , biochemistry , fish <actinopterygii> , shellfish , aquatic animal
1 End‐plate potentials (e.p.p.) have been recorded from the neuromuscular junctions of frog sartorius and extensor longus dig. IV muscles, using intracellular micropipettes. Either curare or MgCl 2 were present in the Ringer solution, to keep the e.p.p. amplitude below the threshold for a muscle action potential and contraction. 2 It has been shown that saxitoxin (paralytic shellfish poison) usually caused a progressive reduction in the amplitude of the e.p.p. Occasionally, when it was applied in the presence of MgCl 2 , the e.p.p. disappeared abruptly. 3 Tetrodotoxin usually caused the e.p.p. to disappear abruptly. Occasionally, when applied in the presence of curare, the e.p.p. declined progressively for a short time before disappearing abruptly. 4 It is concluded that at the frog neuromuscular junction the preferential site of action of saxitoxin is at the nerve terminals, but tetrodotoxin preferentially blocks nerve conduction at a site proximal to the junction. 5 It is suggested that this preparation would be a convenient and reliable test object for distinguishing saxitoxin from tetrodotoxin.