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;
 :Current Clamp

 NEURON {
 	POINT_PROCESS trainIClamp
 	RANGE del, PW, train, amp, freq, i, conv, pulsecount, onoff
 	ELECTRODE_CURRENT i
 }

 UNITS { (na) = (nanoamp) }

 PARAMETER{
 	del (ms)
 	PW (ms)
 	train (ms)
 	amp (na)
 	freq (1/s)
 	conv = 1000 (ms/s)
 	pulsecount (s/s)
 	onoff (s/s)
 	}

 ASSIGNED {
 	i (na)		
 }

 INITIAL  { LOCAL j,k
 	pulsecount = 0
 	onoff = 0
        k =  (train/conv)/freq
 	i = 0
 	FROM j = 0 TO k  {
 		at_time (del + (j*(conv/freq)))
		at_time (del + PW + (j*(conv/freq)))
 		}
 		at_time (del + train)
 }

 BREAKPOINT {
	if (t < del + train && t > del) {
	if (t > del + (pulsecount*(conv/freq)) && t < del + (pulsecount*(conv/freq)) + PW)  {
		i = amp
		onoff = 1
	} else {
	if (onoff == 0) {
		i = 0
		} else {
		i = 0
		pulsecount = pulsecount + 1
		onoff = 0
		}
	}
	} else {
		i = 0
		pulsecount = 0
		onoff = 0
		}
 		
 }

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