The action of philanthotoxin-343 and photolabile analogues on locust (Schistocerca gregaria) muscle |
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| Authors: | H L Sudan C J Kerry I R Mellor S -K Choi D Huang K Nakanishi P N R Usherwood |
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| Institution: | (1) Present address: Boots Pharmaceuticals Research Department, NG2 3AA Nottingham, UK;(2) Department of Chemistry, Columbia University, 10023 New York, NY, USA;(3) Department of Life Science, University of Nottingham, NG7 2RD University Park, Nottingham, UK |
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| Abstract: | The effects of philanthotoxin-343 (PhTX-343; tyrosyl-butanoyl-spermine) and photolabile analogues of this synthetic toxin
on locust (Schistocerca gregaria) skeletal muscle have been investigated using whole muscle preparations (twitch contractions), single muscle fibres (excitatory
postsynaptic currents (EPSCs)) and muscle membrane patches containing single quisqualate-sensitive glutamate receptors (qGluR).
Analogues containing an azido group attached to either the butanoyl side-chain of PhTX-343 or as a substitute for the hydroxyl
moiety of the tyrosyl residue were about 6 fold more potent antagonists than PhTX-343; those with an azido group located at
the distal end of the toxin molecule were generally 2–3 fold less potent than PhTX-343. When these compounds were tested in
subdued light, they were reversible antagonists of the muscle twitch, EPSC and qGluR. When a muscle was irradiated with U.V.
during application of photolabile toxin combined with either neural stimulation of the muscle orl-glutamate application, antagonism of the twitch, EPSC and qGluR was complete and irreversible. |
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| Keywords: | glutamate receptors locust muscle photolabile philanthotoxins voltage clamp patch clamp |
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