Discharge hysteresis in motoneurons (Powers & Heckman 2015)

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Accession:183949
"Motoneuron activity is strongly influenced by the activation of persistent inward currents (PICs) mediated by voltage-gated sodium and calcium channels. ... It has recently been suggested that a number of factors other than PIC can contribute to delta F (firing rate differences between motoneurons) values, including mechanisms underlying spike frequency adaptation and spike threshold accommodation. In the present study, we used a set of compartmental models representing a sample of 20 motoneurons with a range of thresholds to investigate how several different intrinsic motoneuron properties can potentially contribute to variations in F values. ... Our results indicate that, although other factors can contribute, variations in discharge hysteresis and delta F values primarily reflect the contribution of dendritic PICs to motoneuron activation.
Reference:
1 . Powers RK, Heckman CJ (2015) Contribution of intrinsic motoneuron properties to discharge hysteresis and its estimation based on paired motor unit recordings. A simulation study. J Neurophysiol 114:184-198 [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 lumbar motor neuron alpha cell;
Channel(s): I Na,p; I Na,t; I L high threshold; I K; I M; I K,Ca; I_AHP; I Calcium; I Sodium;
Gap Junctions:
Receptor(s):
Gene(s): Kv1.2 KCNA2; Kv1.9 Kv7.1 KCNQ1;
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Spike Frequency Adaptation;
Implementer(s): Powers, Randy [rkpowers at u.washington.edu];
Search NeuronDB for information about:  Spinal cord lumbar motor neuron alpha cell; I Na,p; I Na,t; I L high threshold; I K; I M; I K,Ca; I Sodium; I Calcium; I_AHP;
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Discharge_hysteresis
Model hoc files and output
README.txt
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KCNQ.mod *
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km_hu.mod
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FRMot3dendNaHH.hoc
gramp.ses
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init_3dend_gramp.hoc
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pars2manyhocs.py *
ProxCa.csv
SetConductances2.hoc *
SlowM.csv
standard.csv
twobirampsdel.hoc *
                            
TITLE Potassium Delayed Rectifier Channel
	:This channel is a Voltage Dependent Potassium Channel
	: and will create a current (ik) based on the voltage 
	:Simplied by RKP 3/22/07 to exlude references to different
	: parts of Bob's split dendrite model

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

NEURON {
	SUFFIX kdrRL
	USEION k READ ek WRITE ik
	RANGE ik, g, gMax
	GLOBAL  mVh,mslp, tVh, tslp, tmin,taumax
}

PARAMETER {
	gMax = 0.1 (S/cm2)
	mVh = -25 (mV)
	mslp = 20 (mV)
	tVh = -39 (mV)			
	tslp = 5.5 (mV)			
	tmin = 1.4 (ms)		
	taumax = 11.9(ms)
}			

ASSIGNED {
	v   (mV)
	ek  (mV)
	ik  (mA/cm2)
	g   (S/cm2)
	mtau (ms)
	minf
}

STATE {
	m
}

INITIAL {
	rate(v)
	m = minf
}

BREAKPOINT {
	SOLVE state METHOD cnexp
	g = gMax * m^4
	ik = g*(v - ek)
}

DERIVATIVE state {
	rate(v)
	m' = (minf - m)/mtau
}

PROCEDURE rate(v (mV)) {
	LOCAL b, f TABLE minf,mtau 
	DEPEND mVh,mslp,tVh,tslp,tmin,taumax 
	FROM -100 TO 100 WITH 200

	b = exp((v - tVh)/tslp)
	f = (1 + b)^2
	
	minf = 1/(1+exp(-(v-mVh)/mslp))
	mtau = tmin + taumax*b/f
}

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