Submyelin Potassium accumulation in Subthalamic neuron (STN) axons (Bellinger et al. 2008)

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Accession:121253
"To better understand the direct effects of DBS (Deep brain stimulation) on central neurons, a computational model of a myelinated axon has been constructed which includes the effects of K+ accumulation within the peri-axonal space. Using best estimates of anatomic and electrogenic model parameters for in vivo STN axons, the model predicts a functional block along the axon due to K+ accumulation in the submyelin space. ... These results suggest that therapeutic DBS of the STN likely results in a functional block for many STN axons, although a subset of STN axons may also be activated at the stimulating frequency. "
Reference:
1 . Bellinger SC, Miyazawa G, Steinmetz PN (2008) Submyelin potassium accumulation may functionally block subsets of local axons during deep brain stimulation: a modeling study. J Neural Eng 5:263-74 [PubMed]
Model Information (Click on a link to find other models with that property)
Model Type: Axon;
Brain Region(s)/Organism:
Cell Type(s): Subthalamus nucleus projection neuron;
Channel(s): I Na,p; I K; I Sodium; I_Ks; Na/K pump;
Gap Junctions:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Axonal Action Potentials; Action Potentials; Deep brain stimulation; Sodium pump; Depolarization block;
Implementer(s): Bellinger, Steven [Steve.Bellinger at asu.edu];
Search NeuronDB for information about:  I Na,p; I K; I Sodium; I_Ks; Na/K pump;
TITLE Motor Axon Node channels

: fast k in juxtaparanodal region model, based on:
:
: McIntyre CC, Grill WM, Sherman DL, and Thakor NV. 2004. Cellular effects of deep brain : stimulation: model-based analysis of activation and inhibition. J Neurophysiol 91: 1457-1469.


NEURON {
	SUFFIX fastK	
	USEION k READ ek WRITE ik
	NONSPECIFIC_CURRENT iflut
	RANGE gkfbar, gflut, eflut
	RANGE n_inf
	RANGE tau_n
}


UNITS {
	(mA) = (milliamp)
	(mV) = (millivolt)
}

PARAMETER {
	gkfbar = 0.04	(mho/cm2)
	gflut (mho/cm2)
	eflut=-70	(mV)
}

STATE {	n }

ASSIGNED {
	v (mV)
	ek (mV)
	ik      (mA/cm2)
	iflut   (mA/cm2)
	n_inf
	tau_n (ms)
}

BREAKPOINT {
	SOLVE states METHOD cnexp
	ik = gkfbar*n*n*n*n*(v - ek)
	iflut = gflut*(v-eflut)
}

DERIVATIVE states { 
        evaluate_fct(v)
	n'= (n_inf - n) / tau_n
}

UNITSOFF

INITIAL {
	evaluate_fct(v)
	n = n_inf
}

PROCEDURE evaluate_fct(v(mV)) { LOCAL a,b

	a = vtrap(v)
	b = vtrap0(v)
	tau_n = 1 / (a + b)
	n_inf = a / (a + b)

}

FUNCTION vtrap(x) {
	if (fabs((x+83.2)/1.1) < 1e-6) {
		vtrap = 0.0462*1.1
	}else{
		vtrap = (0.0462*(x+83.2)) / (1 - exp(-(x+83.2)/1.1))
	}
}

FUNCTION vtrap0(x) {
	if (fabs((x+66)/10.5) < 1e-6) {
		vtrap0 = 0.0824*10.5
	}else{
		vtrap0 = (0.0824*(-(x+66))) / (1 - exp((x+66)/10.5))
	}
}

UNITSON

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