Document Detail

Subthreshold inactivation of voltage-gated K+ channels modulates action potentials in neocortical bitufted interneurones from rats.
MedLine Citation:
PMID:  15539396     Owner:  NLM     Status:  MEDLINE    
Voltage-gated K+ channels perform many functions in integration of synaptic input and action potential (AP) generation. In this study we show that in bitufted interneurones from layer 2/3 of the somatosensory cortex, the height and width of APs recorded at the soma are sensitive to changes in the resting membrane potential, suggesting subthreshold activity of voltage-gated conductances. Attributes of K+ currents examined in nucleated patches revealed a fast subthreshold-inactivating K+ conductance (K(f)) and a slow suprathreshold-inactivating K+ conductance (K(s)). Simulations of these K+ conductances, incorporated into a Hodgkin-Huxley-type model, suggested that during a single AP or during low frequency trains of APs, subthreshold inactivation of K(f) was the primary modulator of AP shape, whereas during trains of APs the shape was governed to a larger degree by K(s) resulting in the generation of smaller and broader APs. Utilizing the facilitating function of unitary pyramidal-to-bitufted cell synaptic transmission, single back-propagating APs were initiated in a bitufted interneurone by repeated stimulation of a presynaptic pyramidal cell. Ca2+ imaging and dendritic whole-cell recordings revealed that modulation of APs, which also affect the shape of back-propagating APs, resulted in a change in dendritic Ca2+ influx. Compartmental simulation of the back-propagating AP suggested a mechanism for the modulation of the back-propagating AP height and width by subthreshold activation of K(f). We speculate that this signal may modulate retrograde GABA release and consequently depression of synaptic efficacy of excitatory input from neighbouring pyramidal neurones.
Alon Korngreen; Katharina M M Kaiser; Yuri Zilberter
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, Non-U.S. Gov't     Date:  2004-11-11
Journal Detail:
Title:  The Journal of physiology     Volume:  562     ISSN:  0022-3751     ISO Abbreviation:  J. Physiol. (Lond.)     Publication Date:  2005 Jan 
Date Detail:
Created Date:  2005-01-24     Completed Date:  2005-05-16     Revised Date:  2013-06-09    
Medline Journal Info:
Nlm Unique ID:  0266262     Medline TA:  J Physiol     Country:  England    
Other Details:
Languages:  eng     Pagination:  421-37     Citation Subset:  IM    
Abteilung Zellphysiologie, Max-Planck-Institut für Medizinische Forschung, Jahnstrasse 29, D-69120 Heidelberg, Germany.
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MeSH Terms
Action Potentials / drug effects,  physiology*
Computer Simulation
Dendrites / physiology
Diagnostic Imaging
Interneurons / drug effects*,  ultrastructure
Ion Channel Gating / physiology
Neocortex / drug effects,  physiology*,  ultrastructure
Potassium Channels / physiology*,  ultrastructure
Pyramidal Cells / drug effects,  physiology
Somatosensory Cortex / cytology,  drug effects
Reg. No./Substance:
0/Potassium Channels

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