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]
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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
                            
COMMENT

kv.mod

ENDCOMMENT

INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}

NEURON {
	SUFFIX kv
	USEION k READ ek WRITE ik
	RANGE n, h, gk, gbar
	RANGE ninf, ntau, hinf, htau
	GLOBAL q10, temp, vmin, vmax, v05, za, v05h,zh, Tscale
}

UNITS {
	(mA) = (milliamp)
	(mV) = (millivolt)
	(pS) = (picosiemens)
	(um) = (micron)
} 

PARAMETER {
	gbar = 0   	(pS/um2)	
	v 		(mV)
								
	v05 = -15 (mV)
	za = 11 (mV)

	v05h = -18 (mV)
	zh = -11 (mV)
	
	dt		(ms)
	celsius		(degC)
	temp = 33	(degC)		: original temp 	
	q10  = 2.3				: temperature sensitivity

	Tscale = 10	(degC)
	vmin = -120	(mV)
	vmax = 100	(mV)
} 


ASSIGNED {
	ik 		(mA/cm2)
	ek		(mV)
	gk   		(pS/um2)
	ninf
	hinf
	ntau (ms)	
	htau (ms)
}
 

STATE { n h }

INITIAL { 
	rates(v)
	n = ninf
	h = hinf	
}

BREAKPOINT {
      SOLVE states METHOD cnexp
	gk=gbar*n*h
	ik = (1e-4)*gk*(v - ek)
} 


DERIVATIVE states {    
        rates(v)      
        n' = (ninf - n)/ntau
        h' =  (hinf - h)/htau
}

PROCEDURE rates(vm) {  	  
	  LOCAL qt

          qt=q10^((celsius-temp)/Tscale)
	  ninf = 1/(1 + exp(-(vm - v05)/za))
          ntau = (0.31+1492/((vm+23.5)^2+565)) :/qt

	  hinf = 1/(1 + exp(-(vm - v05h)/zh))
	  htau=300
}