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]
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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 low threshold potassium current found in several brainstem
 nuclei of the auditory system, including the spherical and globular bushy cells
  (Manis and Marx, 1991; Rothman and Manis, 2003a,b) and octopus cells (Bal and
  Oertel, 2000) of the ventral cochlear nucleus, principal cells of the medial 
  nucleus of the trapzoid body (Brew and Forsythe, 1995, Wang and Kaczmarek, 
  1997) and neurons of the medial superior olive. The current is likely mediated by 
  heteromultimers of Kv1.1 and Kv1.2 potassium channel subunits. 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 the mamba snake toxin dendrotoxin-I.

Similar conductrances are found in the homologous neurons of the avian auditory 
system (Reyes and Rubel; Zhang and Trussell; Rathouz and Trussell), and the 
conductance described here, in the absence of more detailed kinetic measurements
, is probably suitable for use in modeling that system.

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

File split implementation, February 28, 2004.



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

        SUFFIX klt
        USEION k READ ek WRITE ik
        RANGE gkltbar, gklt, ik
        GLOBAL winf, zinf, wtau, ztau


        v (mV)
        celsius = 22 (degC)  : model is defined on measurements made at room temp in Baltimore
        dt (ms)
        ek = -77 (mV)
        gkltbar = 0.01592 (mho/cm2) <0,1e9>
        zss = 0.5   <0,1>   : steady state inactivation of glt

        w z

    ik (mA/cm2) 
    gklt (mho/cm2)
    winf zinf
    wtau (ms) ztau (ms)

LOCAL wexp, zexp

	SOLVE states
	gklt = gkltbar*(w^4)*z
    ik = gklt*(v - ek)



    w = winf
    z = zinf

PROCEDURE states() {  :Computes state variables m, h, and n
	trates(v)      :             at the current v and dt.
	w = w + wexp*(winf-w)
	z = z + zexp*(zinf-z)
	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!

    winf = (1 / (1 + exp(-(v + 48) / 6)))^0.25
    zinf = zss + ((1-zss) / (1 + exp((v + 71) / 10)))

    wtau =  (100 / (6*exp((v+60) / 6) + 16*exp(-(v+60) / 45))) + 1.5
    ztau =  (1000 / (exp((v+60) / 20) + exp(-(v+60) / 8))) + 50

PROCEDURE trates(v) {  :Computes rate and other constants at current v.
                      :Call once from HOC to initialize inf at resting v.
	LOCAL tinc
	TABLE winf, wexp, zinf, zexp
	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
	wexp = 1 - exp(tinc/wtau)
	zexp = 1 - exp(tinc/ztau)

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)