Fly lobular plate VS cell (Borst and Haag 1996, et al. 1997, et al. 1999)

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Accession:116956
In a series of papers the authors conducted experiments to develop understanding and models of fly visual system HS, CS, and VS neurons. This model recreates the VS neurons from those papers with enough success to merit approval by Borst although some discrepancies remain (see readme).
Reference:
1 . Borst A, Haag J (1996) The intrinsic electrophysiological characteristics of fly lobula plate tangential cells: I. Passive membrane properties. J Comput Neurosci 3:313-36 [PubMed]
2 . Haag J, Theunissen F, Borst A (1997) The intrinsic electrophysiological characteristics of fly lobula plate tangential cells: II. Active membrane properties. J Comput Neurosci 4:349-69 [PubMed]
3 . Haag J, Vermeulen A, Borst A (1999) The intrinsic electrophysiological characteristics of fly lobula plate tangential cells: III. Visual response properties. J Comput Neurosci 7:213-34 [PubMed]
Citations  Citation Browser
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: Drosophila;
Cell Type(s): Fly lobular plate vertical system cell;
Channel(s): I Na,t; I K; I_K,Na;
Gap Junctions:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Reliability; Vision;
Implementer(s): Carnevale, Ted [Ted.Carnevale at Yale.edu]; Torben-Nielsen, Ben [btorbennielsen at gmail.com];
Search NeuronDB for information about:  I Na,t; I K; I_K,Na;
COMMENT
Na dependent K channel for the fly lobular plate VS cell. This channel has a sigmoidal dependence on 
the actual Na current present.
Based on the paper:
Haag, Theunissen and Borst (1997) "The intrinsic electrophysiological characteristics of fly lobular plate tangential cells: II Active memberane properties".
J. Comp. Neurosc. 4:349-369

Author B. Torben-Nielsen @ TENU/OIST. 2009-01-13 (with help from T. Carnevale)
ENDCOMMENT

NEURON {
	SUFFIX emdkna
	USEION k READ ek WRITE ik
	USEION na READ ina
	RANGE gk, gbar, i
	RANGE ninf, ntau : would be OK for these to be GLOBAL
	GLOBAL slope,taumax
}

UNITS { : units that are not in the units database should be declared here
  (mV) = (millivolt)
  (mA) = (milliamp)
  (uA) = (microamp)
  (S) = (siemens)
}

PARAMETER {
	ek = -20 (mV) : this value will have no effect
	gbar = 0.002 (S/cm2) 	
	: midV from the paper can be left out because it is 0
	slope = 7 (uA/cm2)
	taumax = 3 (ms)
	ntau = 3 (ms) : constant
}

ASSIGNED {
	v (mV) : must declare v
	i 	(mA/cm2)
	ik 	(mA/cm2)
	gk		(S/cm2)
	ninf
	ina (mA/cm2) : for a density mechanism, ionic currents are in (mA/cm2)
}

STATE { n }

INITIAL { 
	rates(ina)
	n = ninf
}

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

DERIVATIVE states {  
	rates(ina)
	n' = (ninf - n)/ntau
}

PROCEDURE rates(ina (mA/cm2)) {
	ninf = 1 / ( 1 + exp( -ina/((1e-3)*slope) ) )  : (1e-3) converts uA/cm2 to mA/cm2
}