Effects of Pb2+ on delayed-rectifier potassium channels in acutely isolated
hippocampal neurons.
Michael Madeja, Ulrich Muáhoff, Norbert Binding, Ute Witting and Erwin-Josef
Speckmann.
From.
APStracts 4:137N, 1997.
ABSTRACT
The effects of Pb2+ on delayed-rectifier potassium currents were studied in
acutely isolated hippocampal neurons (CA1 neurons, CA3 neurons, granule cells)
from the guinea pig using the patch-clamp technique in the whole-cell
configuration. Pb2+ in micromolar concentrations de~creased the potassium
currents in a voltage-dependent manner which appeared as a shift of the
current-voltage relation to positive potentials. The effect was reversible
after washing. The concentration-responsiveness measured in CA1 neurons
revealed an IC50 value of 30 æmol/l at a potential of -30 mV. The half-maximal
shift of the current-voltage relation was reached at 33 æmol/l and the maximal
obtainable shift was 13.4 mV. For the different types of hippocampal neurons,
the shift of the current-voltage relation was distinct and was 7.9 mV in CA1
neurons, 13.7 mV in CA3 neurons and 14.2 mV in granule cells with 50 æmol/l
Pb2+. These here descri~bed effects of Pb2+ on the potassium currents in
hippocampal neurons and the differences be~tween the types of hippocampal
neurons are in correspondence with the known properties and distributions of
cloned potassium channels found in the hippocampus. As a whole, our results
demonstrate that Pb2+ in micromolar concentration is a voltage-dependent,
reversible blocker of delayed-rectifier potassium currents of hippocampal
neurons. This effect has to be taken into consideration as a possible
contributing mechanism for the neurological symptoms of enhanced brain
activity seen during Pb2+ intoxication.
Received 3 July 1997; accepted in final form 3 July 1997.
APS Manuscript Number J755-6.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 27 August 1997