Tonic neuron in spinal lamina I: prolongation of subthreshold depol. (Prescott and De Koninck 2005)

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Accession:53569
Model demonstrates mechanism whereby two kinetically distinct inward currents act synergistically to prolong subthreshold depolarization. The important currents are a persistent Na current (with fast kinetics) and a persistent Ca current (with slower kinetics). Model also includes a slow K current and transient Ca current, in addition to standard HH currents. Model parameters are set to values used in Fig. 8A. Simulation shows prolonged depolarizations in response to two brief stimuli.
Reference:
1 . Prescott SA, De Koninck Y (2005) Integration time in a subset of spinal lamina I neurons is lengthened by sodium and calcium currents acting synergistically to prolong subthreshold depolarization. J Neurosci 25:4743-54 [PubMed]
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:
Cell Type(s): Spinal cord lamina I neuron;
Channel(s): I Na,p; I K,Ca; I Calcium;
Gap Junctions:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Action Potential Initiation; Nociception; Delay; Calcium dynamics;
Implementer(s): Prescott, Steven [steve.prescott at sickkids.ca]];
Search NeuronDB for information about:  I Na,p; I K,Ca; I Calcium;
Files displayed below are from the implementation
TITLE slow K current

COMMENT
12/1/2005 NTC Made compatible with adaptive integration
Unused stuff removed
ENDCOMMENT

: modified by Steven Prescott based on current described below
: Prescott and De Koninck. 2005. J Neurosci 25: 4743-4754
: Slow potassium current in spinal lamina I neurons
: produces slow component of biphasic AHP between spikes
:
: original current described below...
: Fast Na+ and K+ currents responsible for action potentials
: Iterative equations
:
: Equations modified by Traub, for Hippocampal Pyramidal cells, in:
: Traub & Miles, Neuronal Networks of the Hippocampus, Cambridge, 1991
:
: range variable vtraub adjust threshold
:
: Written by Alain Destexhe, Salk Institute, Aug 1992
:
: Modifications by Arthur Houweling for use in MyFirstNEURON

NEURON {
	SUFFIX Ks
	USEION k READ ek WRITE ik
	RANGE gkbar, vtraub, rate_change
	RANGE n_inf
	RANGE tau_n
	RANGE ik 
}


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

PARAMETER {
	gkbar		= .0003 	(mho/cm2)
	ek				(mV)
	celsius			(degC)
	v               		(mV)
	vtraub	= -55		(mV)	: adjusts threshold
	rate_change = 0.1			: slows kinetics when <1
}

STATE {
	n
}

ASSIGNED {
	ik	(mA/cm2)
	n_inf
	tau_n (ms)
	tadj
}


BREAKPOINT {
	SOLVE states METHOD cnexp
	ik  = gkbar * n * (v - ek)
}

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

UNITSOFF
INITIAL {
:
:  Q10 was assumed to be 3
:
	tadj = 3.0 ^ ((celsius-36)/ 10 )
	evaluate_fct(v)
	n= n_inf
}

PROCEDURE evaluate_fct(v(mV)) { LOCAL a,b,v2

	v2 = v - vtraub : convert to traub convention

	a = 0.032 * (15-v2) / ( exp((15-v2)/5) - 1)
	b = 0.5 * exp((10-v2)/40)
	tau_n = 1 / (a + b) / (tadj*rate_change)
	n_inf = a / (a + b)
}

UNITSON

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