Transmitter release and presynaptic Ca2+ currents blocked by the spider toxin omega-Aga-IVA

Neuroreport. 1993 Dec 13;5(3):333-6. doi: 10.1097/00001756-199312000-00039.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylcholine / metabolism
  • Animals
  • Calcium Channel Blockers / pharmacology*
  • Calcium Channels / drug effects
  • Calcium Channels / metabolism*
  • Electric Stimulation
  • Evoked Potentials / drug effects
  • Male
  • Mice
  • Motor Endplate / drug effects
  • Muscle Contraction / drug effects
  • Neurotransmitter Agents / metabolism*
  • Phrenic Nerve / physiology
  • Presynaptic Terminals / drug effects
  • Presynaptic Terminals / metabolism*
  • Respiratory Muscles / drug effects
  • Respiratory Muscles / physiology
  • Spider Venoms / pharmacology*
  • omega-Agatoxin IVA


  • Calcium Channel Blockers
  • Calcium Channels
  • Neurotransmitter Agents
  • Spider Venoms
  • omega-Agatoxin IVA
  • Acetylcholine