Cerebellar purkinje cell: interacting Kv3 and Na currents influence firing (Akemann, Knopfel 2006)

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Accession:80769
Purkinje neurons spontaneously generate action potentials in the absence of synaptic drive and thereby exert a tonic, yet plastic, input to their target cells in the deep cerebellar nuclei. Purkinje neurons express two ionic currents with biophysical properties that are specialized for high-frequency firing: resurgent sodium currents and potassium currents mediated by Kv3.3. Numerical simulations indicated that Kv3.3 increases the spontaneous firing rate via cooperation with resurgent sodium currents. We conclude that the rate of spontaneous action potential firing of Purkinje neurons is controlled by the interaction of Kv3.3 potassium currents and resurgent sodium currents. See paper for more and details.
Reference:
1 . Akemann W, Knöpfel T (2006) Interaction of Kv3 potassium channels and resurgent sodium current influences the rate of spontaneous firing of Purkinje neurons. J Neurosci 26:4602-12 [PubMed]
Model Information (Click on a link to find other models with that property)
Model Type: Neuron or other electrically excitable cell;
Brain Region(s)/Organism:
Cell Type(s): Cerebellum Purkinje GABA cell;
Channel(s): I Na,t; I A; I K; I h; I K,Ca; I Calcium;
Gap Junctions:
Receptor(s):
Gene(s): Kv1.1 KCNA1; Kv4.3 KCND3; Kv3.3 KCNC3; HCN1;
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Ion Channel Kinetics; Oscillations; Action Potentials; Calcium dynamics;
Implementer(s): Akemann, Walther [akemann at brain.riken.jp];
Search NeuronDB for information about:  Cerebellum Purkinje GABA cell; I Na,t; I A; I K; I h; I K,Ca; I Calcium;
TITLE Voltage-gated low threshold potassium current from Kv1 subunits

COMMENT

NEURON implementation of a potassium channel from Kv1.1 subunits
Kinetical scheme: Hodgkin-Huxley m^4, no inactivation

Kinetic data taken from: Zerr et al., J.Neurosci. 18 (1998) 2842
Vhalf = -28.8 +/- 2.3 mV; k = 8.1 +/- 0.9 mV

The voltage dependency of the rate constants was approximated by:

alpha = ca * exp(-(v+cva)/cka)
beta = cb * exp(-(v+cvb)/ckb)

Parameters ca, cva, cka, cb, cvb, ckb
are defined in the CONSTANT block.

Laboratory for Neuronal Circuit Dynamics
RIKEN Brain Science Institute, Wako City, Japan
http://www.neurodynamics.brain.riken.jp

Reference: Akemann and Knoepfel, J.Neurosci. 26 (2006) 4602
Date of Implementation: April 2005
Contact: akemann@brain.riken.jp

ENDCOMMENT


NEURON {
	SUFFIX Kv1
	USEION k READ ek WRITE ik
	RANGE gk, gbar, ik
	GLOBAL ninf, taun
}

UNITS {
	(mV) = (millivolt)
	(mA) = (milliamp)
	(nA) = (nanoamp)
	(pA) = (picoamp)
	(S)  = (siemens)
	(nS) = (nanosiemens)
	(pS) = (picosiemens)
	(um) = (micron)
	(molar) = (1/liter)
	(mM) = (millimolar)		
}

CONSTANT {
	q10 = 3

	ca = 0.12889 (1/ms)
	cva = 45 (mV)
	cka = -33.90877 (mV)

	cb = 0.12889 (1/ms)
      cvb = 45 (mV)
	ckb = 12.42101 (mV)         
}

PARAMETER {
	v (mV)
	celsius (degC)
	
	gbar = 0.011 (mho/cm2)   <0,1e9>
}


ASSIGNED {
 	ik (mA/cm2) 
	ek (mV)
	gk  (mho/cm2)
	ninf
	taun (ms)
	alphan (1/ms)
	betan (1/ms)
	qt
}

STATE { n }

INITIAL {
	qt = q10^((celsius-22 (degC))/10 (degC))
	rates(v)
	n = ninf
}

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

DERIVATIVE states {
	rates(v)
	n' = (ninf-n)/taun 
}

PROCEDURE rates(v (mV)) {
	alphan = alphanfkt(v)
	betan = betanfkt(v)
	ninf = alphan/(alphan+betan) 
	taun = 1/(qt*(alphan + betan))       
}

FUNCTION alphanfkt(v (mV)) (1/ms) {
	alphanfkt = ca * exp(-(v+cva)/cka) 
}

FUNCTION betanfkt(v (mV)) (1/ms) {
	betanfkt = cb * exp(-(v+cvb)/ckb)
}





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