Lead ions close steady-state sodium channels in Helix neurons.
Extracellularly applied Pb2+ (1-150 microM) induced an outward current (IPb) in intracellularly perfused snail neurons. The current-voltage relationship of the Pb(2+)-induced current was linear over the potential range of -100 to -40 mV with negative slope conductance. The Pb-induced current was strongly dependent on the Na+ gradient. The IPb in intra- or extracellular K+- and Cl(-)-free or -rich solutions was almost the same as in control external and internal salines. The negative slope of the I-V curve and the decreased conductivity during Pb2+ application suggested that IPb is owing to the blocking of the resting Na conductance. Data obtained from single-channel measurements also supported this conclusion. Patch-clamp data showed that the steady-state Na channel has a conductance of 14 pS and both closed and open time-distributions displayed single exponential character.
Osipenko
O N
ON
Department of Zoology, Balaton Limnological Research Institute of the Hungarian Academy of Sciences, Tihany.
Györi
J
J
Kiss
T
T
D000818:Animals; D005071:Evoked Potentials / Q000187:drug effects; D006372:Helix, Snails; D066298:In Vitro Techniques; D015640:Ion Channel Gating / Q000187:drug effects*; D007854:Lead / Q000494:pharmacology*; D008564:Membrane Potentials; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D009566:Nitrates / Q000494:pharmacology*; D015222:Sodium Channels / Q000187:drug effects* / Q000502:physiology
D009566:Nitrates; D015222:Sodium Channels; D007854:Lead; C017461:lead nitrate