Computer simulations of neuron-glia interactions mediated by ion flux (Somjen et al. 2008)

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Accession:113446
"... To examine the effect of glial K+ uptake, we used a model neuron equipped with Na+, K+, Ca2+ and Cl− conductances, ion pumps and ion exchangers, surrounded by interstitial space and glia. The glial membrane was either “passive”, incorporating only leak channels and an ion exchange pump, or it had rectifying K+ channels. We computed ion fluxes, concentration changes and osmotic volume changes. ... We conclude that voltage gated K+ currents can boost the effectiveness of the glial “potassium buffer” and that this buffer function is important even at moderate or low levels of excitation, but especially so in pathological states."
Reference:
1 . Somjen GG, Kager H, Wadman WJ (2008) Computer simulations of neuron-glia interactions mediated by ion flux. J Comput Neurosci 25:349-65 [PubMed]
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Model Information (Click on a link to find other models with that property)
Model Type: Neuron or other electrically excitable cell; Electrogenic pump; Glia;
Brain Region(s)/Organism:
Cell Type(s): Astrocyte;
Channel(s): I Na,p; I Na,t; I T low threshold; I A; I K; I K,Ca; Na/Ca exchanger; Na/K pump;
Gap Junctions:
Receptor(s): NMDA;
Gene(s):
Transmitter(s): Ions;
Simulation Environment: NEURON;
Model Concept(s): Epilepsy; Calcium dynamics; Sodium pump;
Implementer(s):
Search NeuronDB for information about:  NMDA; I Na,p; I Na,t; I T low threshold; I A; I K; I K,Ca; Na/Ca exchanger; Na/K pump; Ions;
COMMENT
hzclamp is een aanpassing op:

	Periodic SEClamp
	Based on $NEURONHOME/src/nrnoc/svclmp.mod
	3/27/2000

Alleen is dit een periodieke currentclamp met een trillingstijd 
van 2*dt. Per dt verandert de te injecteren stroom van 0*amp.i
naar 2*amp.i zodat de total geinjecteerde stroom niet verschilt
van de reguliere current clamp, 1*amp.i.

Wij gebruikten de hzclamp om de invloed van de currentclamp en de 
celrespons op het extracellulaire veld te scheiden. waarschijnlijk
werkt deze stimulator in 'CVODE'-mode, m.a.w. de variabele tijdstap
integrator maar is in deze mode nog niet getest.

veel succes, 
Hans Kager, 20-6-2000

netto geen stroom injectie, geen problemen meer met electroneutraliteit


SEClamp:
Although this model appears to work properly, we cannot guarantee 
the absence of bugs, subtle or otherwise.  It is provided as a 
convenience to NEURON users who may wish to try or modify it for 
their own applications.
--Ted Carnevale

ENDCOMMENT

NEURON {
	POINT_PROCESS Hzclampna
	USEION na WRITE ina
	RANGE del, dur, amp, freq, width, ina, telpulse, stand
}

UNITS {
	(nA) = (nanoamp)
	(uS) = (micromho)
}

PARAMETER {
	del (ms)
	dur (ms)	<0,1e9>
	amp (nA)
	dt (ms)
	freq	(1/s)
	width	(ms)
}

ASSIGNED {
	ina (nA)
	i_amp (nA)
	telpulse
	:stand
	notify
}

INITIAL {
	i_amp = 0
	stand = 0
	telpulse = 0
	notify=del
}

BREAKPOINT {
	SOLVE state METHOD after_cvode
	at_time(notify)
	ina = i_amp
}

STATE { stand }

PROCEDURE state() {
	if (t <= del + dur && t >= del) {
	  if (telpulse/(freq/1000) < t-del && t-del <= telpulse/(freq/1000)+width ) {
	    notify = del + telpulse/(freq/1000)+width
	    i_amp=amp
	    stand=1 
	  } else if (stand == 1 ) {
	    stand = 0
	    telpulse = telpulse + 1
	    i_amp = 0
	    notify = del + telpulse/(freq/1000)
	  } else {
	    i_amp = 0
	  }
	}else{
	  i_amp = 0
	}
}