Superior paraolivary nucleus neuron (Kopp-Scheinpflug et al. 2011)

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Accession:139657
This is a model of neurons in the brainstem superior paraolivary nucleus (SPN), which produce very salient offset firing during sound stimulation. Rebound offset firing is triggered by IPSPs coming from the medial nucleus of the trapezoid body (MNTB). This model shows that AP firing can emerge from inhibition through integration of large IPSPs, driven by an extremely negative chloride reversal potential, combined with a large hyperpolarization- activated non-specific cationic current (IH), with a secondary contribution from a T-type calcium conductance (ITCa). As a result, tiny gaps in sound stimuli of just 3-4ms can elicit reliable APs that signal such brief offsets.
Reference:
1 . Kopp-Scheinpflug C, Tozer AJ, Robinson SW, Tempel BL, Hennig MH, Forsythe ID (2011) The sound of silence: ionic mechanisms encoding sound termination. Neuron 71:911-25 [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): Superior paraolivary nucleus neuron;
Channel(s): I T low threshold; I h;
Gap Junctions:
Receptor(s): Glycine;
Gene(s): HCN Cnga1;
Transmitter(s): Glycine;
Simulation Environment: NEURON;
Model Concept(s): Action Potential Initiation; Action Potentials; Rebound firing;
Implementer(s): Hennig, Matthias H [mhhennig at gmail.com];
Search NeuronDB for information about:  Glycine; I T low threshold; I h; Glycine;
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Kopp-Scheinpflug2011
index.html
ht.mod *
lt.mod *
lva.mod
mhh_Gfluct.mod
netstims.mod *
sjg_ih.mod
sjg_na.mod
trigstim.mod *
allgraphs.hoc
conductance_noise.hoc
current_inj.hoc
mosinit.hoc
run_spn_model.hoc
simcontrols.hoc
spn_neuron.hoc
spnmodel1.png
synapses.hoc
                            
TITLE sjg_na.mod  The low threshold conductance of cochlear nucleus neurons

COMMENT

NEURON implementation of Jason Rothman's measurements of VCN conductances.

Original implementation by Paul B. Manis, April (JHU) and Sept, (UNC)1999.

File split implementaiton, April 1, 2004.

Contact: pmanis@med.unc.edu

fit to MNTB data by Sarah J. Griffin, MRC Toxicology Unit, Leicester

ENDCOMMENT

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

NEURON {
        SUFFIX sjg_na
        USEION na WRITE ina
        RANGE gnabar, gna, ina, sjgena
        GLOBAL hinf, minf, htau, mtau, pinf, ptau
}

INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}

PARAMETER {
        v (mV)
        dt (ms)
        sjgena (mV)
        gnabar =  0.07958 (mho/cm2) <0,1e9>
    	fi = 0.8448 <0,1>	: fast inactivating
    	si = 0.0352 <0,1>	: slow inactivation
}

STATE {
        m h p
}

ASSIGNED {
    ina (mA/cm2) 
    gna (mho/cm2)
    minf hinf pinf
    mtau (ms) htau (ms) ptau (ms)
    }

LOCAL mexp, hexp, pexp

BREAKPOINT {
	SOLVE states
    
    gna = gnabar*((m^3* 0.005) + (m^3*h*0.97) + (m^3*p*0.025))
    ina = gna*(v - sjgena)

}

UNITSOFF

INITIAL {
    trates(v)
    m = minf
    h = hinf
    p = pinf
}

PROCEDURE states() {  :Computes state variables m, h, and n
	trates(v)      :             at the current v and dt.
	m = m + mexp*(minf-m)
	h = h + hexp*(hinf-h)
	p = p + pexp*(pinf-p)
VERBATIM
	return 0;
ENDVERBATIM
}

LOCAL q10

PROCEDURE rates(v) {  :Computes rate and other constants at current v.
                      :Call once from HOC to initialize inf at resting v.
		      
		      : Fixed to match jamie's data
    minf = 1 / (1+exp(-(v + 38) / 7))
    hinf = 1/(1+exp((v + 55.4) / 6.3))
    pinf = 1/(1+exp((v + 55.4) / 6.3))


    mtau =  (5 / (5*exp((v+60) / 18) + 36*exp(-(v+60) / 25))) + 0.01
    htau =  (50 / (7*exp((v+60) / 11) + 10*exp(-(v+60) / 25))) + 0.5
    ptau =  (50 / (7*exp((v+60) / 11) + 10*exp(-(v+60) / 25))) + 50

}

PROCEDURE trates(v) {  :Computes rate and other constants at current v.
                      :Call once from HOC to initialize inf at resting v.
	TABLE minf, mexp, hinf, hexp:, pinf, pexp
	DEPEND dt, celsius FROM -150 TO 150 WITH 300

    rates(v)    : not consistently executed from here if usetable_hh == 1
        : so don't expect the tau values to be tracking along with
        : the inf values in hoc

	mexp = 1 - exp(-dt/mtau)
	hexp = 1 - exp(-dt/htau)
	pexp = 1 - exp(-dt/ptau)
	}

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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