Transmitter release and presynaptic Ca2+ currents blocked by the spider toxin omega-Aga-IVA.
Mammalian neuromuscular transmission is resistant to L and N type calcium channel blockers but very sensitive to a low molecular weight funnel web spider venom toxin, FTX, which selectively blocks P type calcium channels. To further characterize the calcium channels involved in neuromuscular transmission we studied the effect of omega Agatoxin (omega-Aga-IVA) a polypeptide P type channel blocker from the same spider venom. We show that omega-Aga-IVA is a potent and irreversible inhibitor of the presynaptic Ca2+ currents and of acetylcholine release induced by electrical stimulation or by K+ depolarization. This provides further evidences that transmitter release at the mammalian neuromuscular junction is mediated by P type Ca2+ channels.
Protti
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Institute of Cell Biology, Faculty of Medicine, University of Buenos Aires, Argentina.
Uchitel
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D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000187:drug effects; D008297:Male; D051379:Mice; D009045:Motor Endplate / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects; D018377:Neurotransmitter Agents / Q000378:metabolism*; D010791:Phrenic Nerve / Q000502:physiology; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism*; D012132:Respiratory Muscles / Q000187:drug effects / Q000502:physiology; D013111:Spider Venoms / Q000494:pharmacology*; D020867:omega-Agatoxin IVA
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D018377:Neurotransmitter Agents; D013111:Spider Venoms; D020867:omega-Agatoxin IVA; D000109:Acetylcholine