Sodium inactivation mechanism modulates QX-314 block of sodium channels in squid axons.
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.
D000818:Animals; D001369:Axons / Q000187:drug effects / Q000502:physiology*; D049832:Decapodiformes; D004553:Electric Conductivity; D007473:Ion Channels / Q000187:drug effects* / Q000502:physiology; D008012:Lidocaine / Q000031:analogs & derivatives* / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D011402:Pronase / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism
D007473:Ion Channels; C012647:QX-314; D008012:Lidocaine; D012964:Sodium; D011402:Pronase