CN bushy, stellate neurons (Rothman, Manis 2003)

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Accession:37857
Using kinetic data from three different K+ currents in acutely isolated neurons, a single electrical compartment model representing the soma of a ventral cochlear nucleus (VCN) neuron was created. The K+ currents include a fast transient current (IA), a slow-inactivating low-threshold current (ILT), and a noninactivating high-threshold current (IHT). The model also includes a fast-inactivating Na+ current, a hyperpolarization-activated cation current (Ih), and 1-50 auditory nerve synapses. With this model, the role IA, ILT, and IHT play in shaping the discharge patterns of VCN cells is explored. Simulation results indicate these currents have specific roles in shaping the firing patterns of stellate and bushy CN cells. (see readme.txt and the papers, esp 2003c, for details). Any questions regarding these implementations should be directed to: pmanis@med.unc.edu 2 April 2004 Paul B Manis, Ph.D.
References:
1 . Rothman JS, Manis PB (2003) The roles potassium currents play in regulating the electrical activity of ventral cochlear nucleus neurons. J Neurophysiol 89:3097-113 [PubMed]
2 . Rothman JS, Manis PB (2003) Kinetic analyses of three distinct potassium conductances in ventral cochlear nucleus neurons. J Neurophysiol 89:3083-96 [PubMed]
3 . Rothman JS, Manis PB (2003) Differential expression of three distinct potassium currents in the ventral cochlear nucleus. J Neurophysiol 89:3070-82 [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): Cochlear nucleus bushy GLU cell; CN stellate cell;
Channel(s): I Na,p; I Na,t; I L high threshold; I A; I K; I K,leak; I Sodium; I Potassium;
Gap Junctions:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Temporal Pattern Generation; Action Potentials; Audition;
Implementer(s): Manis, Paul B [PManis at med.unc.edu];
Search NeuronDB for information about:  Cochlear nucleus bushy GLU cell; I Na,p; I Na,t; I L high threshold; I A; I K; I K,leak; I Sodium; I Potassium;
TITLE klt.mod  The low threshold conductance of cochlear nucleus neurons

COMMENT

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

This file implements the average brain sodium current used in the Rothman model.
In the absence of direct measurements in the VCN, this is a fair assumption.
The model differs from the one used in Rothman et al, (1993) in that the steep
voltage dependence of recovery from inactivation in that model is missing. This
may affect the refractory period. To use the other model, use najsr.mod instead.

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

File split implementaiton, April 1, 2004.

Contact: pmanis@med.unc.edu

ENDCOMMENT

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

NEURON {
        SUFFIX na
        USEION na READ ena WRITE ina
        RANGE gnabar, gna, ina
        GLOBAL hinf, minf, htau, mtau
}

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

PARAMETER {
        v (mV)
        celsius = 22 (degC)  : model is defined on measurements made at room temp in Baltimore
        dt (ms)
        ena (mV)
        gnabar =  0.07958 (mho/cm2) <0,1e9>
}

STATE {
        m h
}

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

LOCAL mexp, hexp

BREAKPOINT {
	SOLVE states
    
    gna = gnabar*(m^3)*h
    ina = gna*(v - ena)

}

UNITSOFF

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

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)
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.

	q10 = 3^((celsius - 22)/10) : if you don't like room temp, it can be changed!

: average sodium channel
    minf = 1 / (1+exp(-(v + 38) / 7))
    hinf = 1 / (1+exp((v + 65) / 6))

    mtau =  (10 / (5*exp((v+60) / 18) + 36*exp(-(v+60) / 25))) + 0.04
    htau =  (100 / (7*exp((v+60) / 11) + 10*exp(-(v+60) / 25))) + 0.6
}

PROCEDURE trates(v) {  :Computes rate and other constants at current v.
                      :Call once from HOC to initialize inf at resting v.
	LOCAL tinc
	TABLE minf, mexp, hinf, hexp
	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

	tinc = -dt * q10
	mexp = 1 - exp(tinc/mtau)
	hexp = 1 - exp(tinc/htau)
	}

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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