Subthreshold inact. of K channels modulates APs in bitufted interneurons (Korngreen et al 2005)

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Accession:83523
... 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 (Kf ) and a slow suprathreshold-inactivating K+ conductance (Ks ). 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 Kf was the primary modulator of AP shape, whereas during trains of APs the shape was governed to a larger degree by Ks resulting in the generation of smaller and broader APs. ... 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 Kf . We speculate that this signal may modulate retrograde GABA release and consequently depression of synaptic efficacy of excitatory input from neighbouring pyramidal neurones.
Reference:
1 . Korngreen A, Kaiser KM, Zilberter Y (2005) Subthreshold inactivation of voltage-gated K+ channels modulates action potentials in neocortical bitufted interneurones from rats. J Physiol 562:421-37 [PubMed]
Model Information (Click on a link to find other models with that property)
Model Type: Channel/Receptor;
Brain Region(s)/Organism:
Cell Type(s): Neocortex bitufted interneuron;
Channel(s): I K;
Gap Junctions:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Ion Channel Kinetics; Action Potentials;
Implementer(s): Korngreen, Alon [alon.korngreen at gmail.com];
Search NeuronDB for information about:  I K;
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korngreenEtAl2005
readme.txt
kfast.mod
kv.mod
mosinit.hoc
                            
This is the readme for the model associated with the paper

Korngreen A, Kaiser KM, Zilberter Y (2005) Subthreshold inactivation
of voltage-gated K+ channels modulates action potentials in
neocortical bitufted interneurones from rats. J Physiol 562:421-37

Abstract:

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 (Kf) and a slow
suprathreshold-inactivating K+ conductance (Ks). 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 Kf was the primary modulator of AP
shape, whereas during trains of APs the shape was governed to a larger
degree by Ks 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
Kf. We speculate that this signal may modulate retrograde GABA release
and consequently depression of synaptic efficacy of excitatory input
from neighbouring pyramidal neurones.

The mod files for Kf and Ks are supplied here by Dr Alon Korngreen.

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