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110 lines
3.0 KiB
110 lines
3.0 KiB
2 years ago
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TITLE klt.mod The low threshold conductance of cochlear nucleus neurons
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COMMENT
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NEURON implementation of Jason Rothman's measurements of VCN conductances.
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This file implements the low threshold potassium current found in several brainstem
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nuclei of the auditory system, including the spherical and globular bushy cells
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(Manis and Marx, 1991; Rothman and Manis, 2003a,b) and octopus cells (Bal and
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Oertel, 2000) of the ventral cochlear nucleus, principal cells of the medial
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nucleus of the trapzoid body (Brew and Forsythe, 1995, Wang and Kaczmarek,
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1997) and neurons of the medial superior olive. The current is likely mediated by
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heteromultimers of Kv1.1 and Kv1.2 potassium channel subunits. The specific
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implementation is described in Rothman and Manis, J. Neurophysiol. 2003, in the
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appendix. Measurements were made from isolated neurons from adult guinea pig,
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under reasonably stringent voltage clamp conditions. The measured current is
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sensitive to the mamba snake toxin dendrotoxin-I.
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Similar conductrances are found in the homologous neurons of the avian auditory
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system (Reyes and Rubel; Zhang and Trussell; Rathouz and Trussell), and the
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conductance described here, in the absence of more detailed kinetic measurements
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, is probably suitable for use in modeling that system.
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Original implementation by Paul B. Manis, April (JHU) and Sept, (UNC)1999.
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File split implementation, February 28, 2004.
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Contact: pmanis@med.unc.edu
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ENDCOMMENT
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UNITS {
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(mA) = (milliamp)
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(mV) = (millivolt)
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(nA) = (nanoamp)
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}
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NEURON {
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THREADSAFE
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SUFFIX klt
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USEION k READ ek WRITE ik
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RANGE gbar, gklt, ik, q10g
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GLOBAL winf, zinf, wtau, ztau
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}
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INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}
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PARAMETER {
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v (mV)
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dt (ms)
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gbar = 0.01592 (mho/cm2) <0,1e9>
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zss = 0.5 <0,1> : steady state inactivation of glt
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q10tau = 3.0
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q10g = 2.0
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}
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STATE {
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w z
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}
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ASSIGNED {
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celsius (degC) : model is defined on measurements made at room temp in Baltimore
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ik (mA/cm2)
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ek (mV)
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gklt (mho/cm2)
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winf zinf
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wtau (ms) ztau (ms)
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qg () : computed q10 for gnabar based on q10g
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q10 ()
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}
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LOCAL wexp, zexp
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BREAKPOINT {
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SOLVE states METHOD cnexp
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gklt = qg*gbar*(w^4)*z
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ik = gklt*(v - ek)
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}
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INITIAL {
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qg = q10g^((celsius-22)/10 (degC))
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q10 = q10tau^((celsius - 22)/10 (degC)) : if you don't like room temp, it can be changed!
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rates(v)
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w = winf
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z = zinf
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}
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DERIVATIVE states { :Computes state variables m, h, and n
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rates(v) : at the current v and dt.
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w' = (winf - w)/wtau
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z' = (zinf - z)/ztau
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}
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PROCEDURE rates(v (mV)) { :Computes rate and other constants at current v.
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:Call once from HOC to initialize inf at resting v.
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winf = (1 / (1 + exp(-(v + 48) / 6 (mV))))^0.25
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zinf = zss + ((1-zss) / (1 + exp((v + 71) / 10 (mV))))
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wtau = (100 (ms)/ (6*exp((v+60) / 6 (mV)) + 16*exp(-(v+60) / 45 (mV)))) + 1.5
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wtau = wtau/q10
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ztau = (1000 (ms)/ (exp((v+60) / 20 (mV)) + exp(-(v+60) / 8 (mV)))) + 50
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ztau = ztau/q10
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}
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