Recurrent discharge in a reduced model of cat spinal motoneuron (Balbi et al, 2013)

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Accession:151443
Following a distal stimulation of a motor fibre, only a fraction of spinal motoneurons are able to produce a re-excitation of the initial segment leading to an orthodromically conducted action potential, known as recurrent discharge. In order to show the reciprocal interplay of the axonal initial segment and the soma leading to recurrent discharge in detail, a reduced model of a cat spinal motoneuron was developed.
Reference:
1 . Balbi P, Martinoia S, Colombo R, Massobrio P (2014) Modelling recurrent discharge in the spinal a-motoneuron: reappraisal of the F wave. Clin Neurophysiol 125:427-9 [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 ACh cell;
Channel(s): I Na,p; I Na,t; I K; I K,Ca;
Gap Junctions:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Recurrent Discharge;
Implementer(s): Balbi, Pietro [piero.balbi at fsm.it];
Search NeuronDB for information about:  Spinal cord lumbar motor neuron alpha ACh cell; I Na,p; I Na,t; I K; I K,Ca;
TITLE Naf_So.mod   fast sodium channel
 
COMMENT
This is the original Hodgkin-Huxley treatment for the set of sodium channel found
in the squid giant axon membrane.
Some parameters have been changed to correspond to McIntyre and Grill (2002) "Extracellular
stimulation of central neurons"
Author: Balbi
ENDCOMMENT
 
UNITS {
        (mA) = (milliamp)
        (mV) = (millivolt)
		(S) = (siemens)
}
 
NEURON {
        SUFFIX Naf_So
        USEION na READ ena WRITE ina
        RANGE gnamax, gna
        RANGE minf, hinf, mtau, htau
}
 
PARAMETER {
        gnamax = .1 (S/cm2)   <0,1e9>
}
 
STATE {
        m h
}
 
ASSIGNED {
        v (mV)
        ena (mV)

		gna (S/cm2)
        ina (mA/cm2)
        minf hinf
		mtau (ms) htau (ms)
}
 
BREAKPOINT {
        SOLVE states METHOD cnexp
        gna = gnamax*m*m*m*h
		ina = gna*(v - ena)
} 
 
INITIAL {
	rates(v)
	m = minf
	h = hinf
}

DERIVATIVE states {
        rates(v)
        m' = (minf-m)/mtau
        h' = (hinf-h)/htau
}
 
PROCEDURE rates(v(mV)) {  
		:Call once from HOC to initialize inf at resting v.
        LOCAL  alpha, beta, sum

UNITSOFF
                :"m" sodium activation system
        alpha = .4 * vtrap(-66 - v, 5)
        beta =  .4 * vtrap(v + 32, 5)
        sum = alpha + beta
		mtau = 1/sum
        minf = alpha/sum
                :"h" sodium inactivation system
		htau = 30/(exp((60+v)/15)+exp(-(60+v)/16))
        hinf = 1/(1+exp((65+v)/7))
}
 
FUNCTION vtrap(x,y) {  :Traps for 0 in denominator of rate eqns.
        if (fabs(x/y) < 1e-6) {
                vtrap = y*(1 - x/y/2)
        }else{
                vtrap = x/(exp(x/y) - 1)
        }
}
 
UNITSON

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