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Phosphorylation‐dependent differences in the activation properties of distal and proximal dendritic Na + channels in rat CA1 hippocampal neurons
Author(s) -
Gasparini Sonia,
Magee Jeffrey C.
Publication year - 2002
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2002.020503
Subject(s) - hippocampal formation , staurosporine , chemistry , biophysics , membrane potential , electrophysiology , phosphorylation , neuroscience , biology , protein kinase a , biochemistry
At distal dendritic locations, the threshold for action potential generation is higher and the amplitude of back‐propagating spikes is decreased. To study whether these characteristics depend upon Na + channels, their voltage‐dependent properties at proximal and distal dendritic locations were compared in CA1 hippocampal neurons. Distal Na + channels activated at more hyperpolarized voltages than proximal (half‐activation voltages were −20.4 ± 2.4 mV vs. −12.0 ± 1.7 mV for distal and proximal patches, respectively, n = 16 , P < 0.01 ), while inactivation curves were not significantly different. The resting membrane potential of distal regions also appeared to be slightly but consistently more hyperpolarized than their proximal counterpart. Staurosporine, a non‐selective protein kinase inhibitor, shifted the activation curves for both proximal and distal Na + channels to the left so that they overlapped and also caused the resting potentials to be comparable. Staurosporine affected neither the inactivation kinetics of Na + currents nor the reversal potential for Na + . These results suggest that the difference in the voltage dependence of activation of distal and proximal Na + channels can be attributed to a different phosphorylation state at the two locations.