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 sodium potassium pump
:  from Lindblad et al Am J Physiol 1996 275:H1666

: Original model has been modified to assume constant nai

NEURON {
	SUFFIX NaKpump
	USEION k READ ko WRITE ik
	USEION na WRITE ina
	RANGE ik, ina , INaKmax, ink, Kmko, Kmnai
	GLOBAL dummy : prevent vectorization for use with CVODE
}

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

PARAMETER {
	INaKmax = 2.45e-3 (mA/cm2) <0,1e6>
	Kmnai = 27.9 (mM)    <0,1e6>
	Kmko = 5.3 (mM)    <0,1e6>
	nai = 10 (mM)
}

ASSIGNED {
	celsius (degC)
	v (mV)
	ko (mM)
	ik (mA/cm2)
	ina (mA/cm2)
	ink (mA/cm2)
	dummy
}

BREAKPOINT { LOCAL q10 , fnk 
	
	q10 = 3^((celsius - 37)/10 (degC))
	
	fnk = (v + 150)/(v + 200)
				
	ink= q10*INaKmax*fnk/((1 + (Kmnai/nai)^1.5)*(1 + Kmko/ko))
	ina = 3*ink
	ik = -2*ink
}

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