Axonal subthreshold voltage signaling along hippocampal mossy fiber (Kamiya 2022)

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Subthreshold depolarization of soma passively propagates into the axons for a substantial distance and thereby caused enhancement of the transmitter release from the axon terminals of hippocampal mossy fibers. Here we developed the granule cell-mossy fiber model implemented with axonal sodium potassium and calcium channels and explored the mechanisms underlying analog modulation of the action potential-evoked transmitter release by subthreshold voltage signaling along the axons. Action potential-induced calcium entry to the terminals was reduced, while subthreshold depolarization itself caused small calcium entry.
1 . Kamiya H (2022) Modeling analysis of subthreshold voltage signaling along hippocampal mossy fiber axons Front Cell Neurosci
Model Information (Click on a link to find other models with that property)
Model Type: Axon;
Brain Region(s)/Organism: Hippocampus;
Cell Type(s): Dentate gyrus granule GLU cell;
Channel(s): I Calcium; I Sodium; I K;
Gap Junctions:
Receptor(s): AMPA; GabaA;
Transmitter(s): Glutamate; Gaba;
Simulation Environment: NEURON;
Model Concept(s): Action Potentials; Axonal Action Potentials; Analog coding; Subthreshold signaling;
Implementer(s): Kamiya, Haruyuki [kamiya at];
Search NeuronDB for information about:  Dentate gyrus granule GLU cell; GabaA; AMPA; I K; I Sodium; I Calcium; Gaba; Glutamate;
TITLE: mfbhh.mod    Sodium and potassium channels of mossy fiber boutons

  This is the Hodgkin-Huxley treatment for the set of sodium, potassium, 
  and leakage channels found in the hippocampal mossy fiber boutons.
  ("Presynaptic action potential amplification by voltage-gated Na+ channels in 
  hippocampal mossy fiber boutons" Neuron 45:405-417 (2005).)
  Global activation & inactivation shift; make vShift (Donnan) global by 12 mV.  
  "Engel & Jonas model (2005)" reconstructed by Kamiya 
        (mA) = (milliamp)
        (mV) = (millivolt)
	    (S) = (siemens)
? interface
        SUFFIX mfbhh
        USEION na READ ena WRITE ina
        USEION k READ ek WRITE ik
        RANGE gnabar, gkbar, gl, el, gna, gk
        GLOBAL minf, hinf, ninf, rinf, mtau, htau, ntau, rtau
	THREADSAFE : assigned GLOBALs will be per thread
        gnabar = 0.05 (S/cm2)
        gkbar = 0.036 (S/cm2)
        gl = .0001 (S/cm2)
        el = -81 (mV)
        m h n r
        v (mV)
        celsius (degC)
        ena (mV)
        ek (mV)

	    gna (S/cm2)
	    gk (S/cm2)
        ina (mA/cm2)
        ik (mA/cm2)
        il (mA/cm2)
        minf hinf ninf rinf
	mtau (ms) htau (ms) ntau (ms) rtau (ms)
? currents
        SOLVE states METHOD cnexp
    gna = gnabar*m*m*m*h
	ina = gna*(v - ena)
    gk = gkbar*n*n*n*n*r
	ik = gk*(v - ek)      
    il = gl*(v - el)
	m = minf
	h = hinf
	n = ninf
    r = rinf

? states
DERIVATIVE states {  
        m' = (minf-m)/mtau
        h' = (hinf-h)/htau
        n' = (ninf-n)/ntau
        r' = (rinf-r)/rtau
:LOCAL q10

? rates
PROCEDURE rates(v(mV)) {  :Computes rate and other constants at current v.
                      :Call once from HOC to initialize inf at resting v.
        LOCAL  alpha, beta, sum, q10
        TABLE minf, mtau, hinf, htau, ninf, ntau, rinf, rtau DEPEND celsius FROM -100 TO 100 WITH 200

        q10 = 3^((celsius - 23)/10)
	 :"m" sodium activation system
        alpha = 93.8285*vtrap(-(v-12-105.023),17.7094)
        beta =  0.168396*exp(-(v-12)/23.2707)
        sum = alpha + beta
	    mtau = 1/(q10*sum)
        minf = alpha/sum
     :"h" sodium inactivation system
        alpha = 0.000354*exp(-(v-12)/18.706)
        beta = 6.62694/(exp(-(v-12+17.6769)/13.3097)+1)
        sum = alpha + beta
	    htau = 1/(q10*sum)
        hinf = alpha/sum
     :"n" potassium activation system
        alpha = .01*vtrap(-(v+55),10) 
        beta = .125*exp(-(v+65)/80)
	    sum = alpha + beta
        ntau = 1/(q10*sum)
        ninf = alpha/sum
     :"r" potassium inactivation system
        alpha = 0.0000256077*exp(-v/45.4217)
        beta = 0.0330402/(exp(-(v+45.6599)/2.30235)+1)  :Recombinant Kv1.4
        sum = alpha + beta
	    rtau = 1/(q10*sum)
        rinf = alpha/sum
FUNCTION vtrap(x,y) {  :Traps for 0 in denominator of rate eqns.
        if (fabs(x/y) < 1e-6) {
                vtrap = y*(1 - x/y/2)
                vtrap = x/(exp(x/y) - 1)

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