Modulation of the gating of the transient outward potassium current of rat isolated cerebellar granule neurons by lanthanum.
The effects of the trivalent cation, lanthanum (La3+) on voltage-dependent K+ conductances were studied in rat isolated cerebellar granule neurons under whole-cell voltage-clamp conditions. La3+ at low micromolar concentrations caused a pronounced enhancement in the outward current evoked by depolarising steps from -50 mV, with the apparent recruitment of an inactivating component. The steady-state inactivation curve for the transient outward current, evoked by depolarising steps from -140 mV, was shifted by approximately 40 mV in the depolarising direction by 10 microM La3+, with a slight increase in the slope factor. The kinetics of activation and inactivation were slowed in the presence of La3+. A shift of 10 mV in the depolarising direction was seen for the activation curve of the delayed rectifier current in the presence of 10 microM La3+. These results indicate that La3+ has a potent effect on the gating characteristics of voltage-activated K+ currents. This effect cannot be explained by surface charge considerations.
Watkins
C S
CS
Department of Pharmacology, Royal Free Hospital School of Medicine, London, UK.
Mathie
A
A
D000818:Animals; D002469:Cell Separation; D002531:Cerebellum / Q000166:cytology / Q000502:physiology*; D004553:Electric Conductivity; D005260:Female; D015640:Ion Channel Gating / Q000187:drug effects*; D007811:Lanthanum / Q000494:pharmacology*; D008297:Male; D009474:Neurons / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology*; D051381:Rats
D015221:Potassium Channels; D007811:Lanthanum