Polyamine FTX-3.3 and polyamine amide sFTX-3.3 inhibit presynaptic calcium currents and acetylcholine release at mouse motor nerve terminals

M. Fatehi, E.G. Rowan, A.L. Harvey, E. Moya, I.S. Blagbrough

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6 Citations (Scopus)


FTX-3.3 is the proposed structure of a calcium-channel blocking toxin that has been isolated from the funnel web spider (Agelenopsis aperta). The effects of FTX-3.3 and one of its analogues, sFTX-3.3, on acetylcholine release, on presynaptic currents at mouse motor nerve terminals and on whole-cell sodium currents in SK.N.SH cells (a human neuroblastoma cell line) have been studied. FTX-3.3 (10-30 microM) and sFTX-3.3 (100-300 microM) reversibly reduced release of acetylcholine by approximately 70-90% and 40-60%, respectively. FTX-3.3 (10 microM) blocked the fast component of presynaptic calcium currents by approximately 60%. sFTX-3.3 (100 microM) reduced the duration of the slow component of presynaptic calcium currents by about 50% of the control and also reduced presynaptic sodium current by approximately 20% of the control. sFTX-3.3 (100 microM) reduced whole-cell sodium current recorded from SK.N.SH cells by approximately 15%, whereas FTX-3.3, even at 200 microM, did not affect this current. Since the only difference in chemical structures of these toxins is that sFTX-3.3 has an amide function which is absent in FTX-3.3, the amide function may be responsible for the reduced potency and selectivity of sFTX-3.3. This study also provides further support for the existence of P-type calcium channels at mouse motor nerve terminals.
Original languageEnglish
Pages (from-to)185-94
Number of pages10
Issue number2
Publication statusPublished - Feb 1997


  • acetylcholine
  • animals
  • brain neoplasms
  • calcium channel blockers
  • cholinergic antagonists
  • electrophysiology
  • humans
  • membrane potentials
  • mice
  • motor endplate
  • neuroblastoma
  • patch-clamp techniques
  • polyamines
  • presynaptic peceptors
  • sodium channels
  • synaptic transmission
  • tumor cells

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