CN bushy, stellate neurons (Rothman, Manis 2003)

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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: 2 April 2004 Paul B Manis, Ph.D.
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:
Simulation Environment: NEURON;
Model Concept(s): Temporal Pattern Generation; Action Potentials; Audition;
Implementer(s): Manis, Paul B [PManis at];
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


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

This file implements the transient potassium current found in ventral cochlear
nucleus "Type I" cells, which are largely "stellate" or "multipolar" cells  (Manis and
Marx, 1991; Rothman and Manis, 2003a,b; Manis et al, 1996). The current is likely
 mediated by Kv4.2 potassium channel subunits, but this has not been directly
demonstrated. The specific implementation is described in Rothman and Manis, J.
Neurophysiol. 2003, in the appendix. Measurements were made from isolated 
neurons from adult guinea pig, under reasonably stringent voltage clamp conditions.
 The measured current is sensitive to 4-aminopyridine. 
Original implementation by Paul B. Manis, April (JHU) and Sept, (UNC)1999.

File split implementaiton, April 1, 2004.



        (mA) = (milliamp)
        (mV) = (millivolt)
        (nA) = (nanoamp)

        SUFFIX ka
        USEION k READ ek WRITE ik
        RANGE gkabar, gka, ik
        GLOBAL ainf, binf, cinf, atau, btau, ctau


        v (mV)
        celsius = 22 (degC)  : model is defined on measurements made at room temp in Baltimore
        dt (ms)
        ek = -77 (mV)
        gkabar = 0.00477 (mho/cm2) <0,1e9>

        a b c

    ik (mA/cm2) 
    gka (mho/cm2)
    ainf binf cinf
    atau (ms) btau (ms) ctau (ms)

LOCAL aexp, bexp, cexp

	SOLVE states
	gka = gkabar*(a^4)*b*c
    ik = gka*(v - ek)



    a = ainf
    b = binf
    c = cinf

PROCEDURE states() {  :Computes state variables m, h, and n
	trates(v)      :             at the current v and dt.
	a = a + aexp*(ainf-a)
	b = b + bexp*(binf-b)
	c = c + cexp*(cinf-c)
	return 0;


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!

    ainf = (1 / (1 + exp(-1*(v + 31) / 6)))^0.25
    binf = 1 / (1 + exp((v + 66) / 7))^0.5
    cinf = 1 / (1 + exp((v + 66) / 7))^0.5

    atau =  (100 / (7*exp((v+60) / 14) + 29*exp(-(v+60) / 24))) + 0.1
    btau =  (1000 / (14*exp((v+60) / 27) + 29*exp(-(v+60) / 24))) + 1
    ctau = (90 / (1 + exp((-66-v) / 17))) + 10

PROCEDURE trates(v) {  :Computes rate and other constants at current v.
                      :Call once from HOC to initialize inf at resting v.
	LOCAL tinc
	TABLE ainf, aexp, binf, bexp, cinf, cexp
	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
	aexp = 1 - exp(tinc/atau)
	bexp = 1 - exp(tinc/btau)
	cexp = 1 - exp(tinc/ctau)

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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