Sodium inactivation mechanism modulates QX-314 block of sodium channels in squid axons

Biophys J. 1978 Nov;24(2):569-74. doi: 10.1016/S0006-3495(78)85403-4.


Blocking action of Na channels by QX-314, a quaternary derivative of lidocaine, was studied in internally perfused and voltage-clamped axons of squid. In axons with intact Na inactivation, QX-314 exhibited both a frequency- and a voltage-dependent block of Na channels. Repetitive pulsing to more positive potentials enhanced the degree of block. Both frequency- and voltage-dependent blocks disappeared in axons in which Na inactivation had been destroyed by either pronase or N-bromoacetamide treatment. These results support the notion that Na inactivation not only modulates the frequency-dependent block but also involves the voltage-dependent binding reaction between QX-314 and Na channels.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Axons / drug effects
  • Axons / physiology*
  • Decapodiformes
  • Electric Conductivity
  • Ion Channels / drug effects*
  • Ion Channels / physiology
  • Lidocaine / analogs & derivatives*
  • Lidocaine / pharmacology
  • Membrane Potentials / drug effects
  • Pronase / pharmacology
  • Sodium / metabolism


  • Ion Channels
  • QX-314
  • Lidocaine
  • Sodium
  • Pronase