Interaction of tetraethylammonium ion derivatives with the potassium channels of giant axons.
A number of compounds related to TEA(+) (tetraethylammoniumion) were injected into squid axons and their effects on g(K) (the potassium conductance) were determined. In most of these ions a quaternary nitrogen is surrounded by three ethyl groups and a fourth group that is very hydrophobic. Several of the ions cause inactivation of g(K), a type of ionic gating that is not normally seen in squid axon; i.e., after depolarization g(K) increases and then spontaneously decreases to a small fraction of its peak value even though the depolarization is maintained. Observations on the mechanism of this gating show that (a) QA (quaternary ammonium) ions only enter K(+) channels that have open activation gates (the normal permeability gates). (b) The activation gates of QA-occluded channels do not close readily. (c) Hyperpolarization helps to clear QA ions from the channels. (d) Raising the external K(+) concentration also helps to clear QA ions from the channels. Observations (c) and (d) strongly suggest that K(+) ions traverse the membrane by way of pores, and they cannot be explained by the usual type of carrier model. The data suggest that a K(+) pore has two distinct parts: a wide inner mouth that can accept a hydrated K(+) ion or a TEA(+)-like ion, and a narrower portion that can accept a dehydrated or partially dehydrated K(+) ion, but not TEA(+).
D000818:Animals; D001369:Axons / Q000187:drug effects / Q000502:physiology*; D002463:Cell Membrane Permeability; D066298:In Vitro Techniques; D007474:Ion Exchange; D007477:Ions; D008564:Membrane Potentials; D008954:Models, Biological; D008974:Mollusca; D011188:Potassium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology*
D007477:Ions; D013757:Tetraethylammonium Compounds; D011188:Potassium