Phosphorylation-dependent differences in the activation properties of distal and proximal dendritic Na+ channels in rat CA1 hippocampal neurons.
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.
Gasparini
Sonia
S
Neuroscience Center, Louisiana State University Health Science Center, New Orleans 70112, USA. sgaspa1@lsuhsc.edu
Magee
Jeffrey C
JC
D000465:Algorithms; D000818:Animals; D001369:Axons / Q000502:physiology; D003712:Dendrites / Q000502:physiology*; D004594:Electrophysiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology / Q000502:physiology*; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors; D051381:Rats; D017207:Rats, Sprague-Dawley; D015222:Sodium Channels / Q000502:physiology*; D019311:Staurosporine / Q000494:pharmacology
D004791:Enzyme Inhibitors; D047428:Protein Kinase Inhibitors; D015222:Sodium Channels; D019311:Staurosporine