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138 lines
4.3 KiB
138 lines
4.3 KiB
TITLE nacn.mod A sodium conductance for a ventral cochlear nucleus neuron model |
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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 a modified version of the average brain sodium current |
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used in the Rothman and Manis 2003 models. |
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The model differs from the one used in Rothman et al, (1993) in that the steep |
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voltage dependence of recovery from inactivation in that model is missing. This |
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may affect the refractory period. To use the other model, use jsrnaf.mod instead. |
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Original implementation by Paul B. Manis, April 1999 (JHU) and Sept 1999 (UNC-CH). |
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File split implementation, April 1, 2004. |
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Version nacncoop implements a cooperative sodium channel model built on the kinetics |
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of the original nacn model (R&M2003c). The motivation is to make a sodium channel with |
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faster activation kinetics, by introducing cooperativity between a subset of channels. |
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The model is based on concepts and implementation similar to Oz et al. |
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J.Comp. Neurosci. 39: 63, 2015, and Huang et al., PloSOne 7:e37729, 2012. |
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The cooperative channels are modeled with the same kinetics as the non-cooperative |
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channels, but are treated as a separate subset (fraction: p). The cooperativity is |
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introduced by shifting the voltage "seen" by the channels by KJ*m^3*h, which moves |
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the channels to a faster regime (essentially, they experience a depolarized membrane |
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potential that depends on their current gating state, relative to the main population |
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of channels). |
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A subpopulation of Na channels (p [0..1]) experiences a small voltage-dependent shift |
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in the gating kinetics. The shift is determined by KJ |
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This version does not have all the temperature scaling. Does not pass modlunit. |
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Should work at 22C, appears to work at other temperatures ok. |
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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 nacncoop |
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USEION na READ ena WRITE ina |
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RANGE gbar, gna, ina, p, KJ |
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RANGE vsna : voltage shift parameter |
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GLOBAL hinf, minf, htau, mtau, hinf2, minf2, htau2, mtau2 |
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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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celsius (degC) : 22 (degC) model is defined at room temp in Baltimore |
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dt (ms) |
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ena (mV) |
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gbar = 0.07958 (mho/cm2) <0,1e9> |
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q10 = 3.0 : q10 for rates |
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p = 0.0 (): fraction of cooperative channels (0-1) |
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KJ = 0 (mV) : coupling strength between cooperative channels (0-1000mV is usable range) |
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: setting either KJ = 0 or p = 0 will remove cooperativity. |
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vsna = 0 (mV) |
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} |
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STATE { |
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m h m2 h2 |
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} |
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ASSIGNED { |
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ina (mA/cm2) |
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gna (mho/cm2) |
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vNa (mV) : shifted V for cooperative behavior |
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minf hinf minf2 hinf2 |
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mtau (ms) htau (ms) mtau2 (ms) htau2 (ms) |
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} |
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LOCAL mexp, hexp, mexp2, hexp2 |
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BREAKPOINT { |
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SOLVE states METHOD cnexp |
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gna = gbar*(p*(m2^3*h2) + (1.-p)*(m^3)*h) |
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ina = gna*(v - ena) |
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} |
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UNITSOFF |
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INITIAL { |
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rates(v) |
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m = minf |
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h = hinf |
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m2 = minf2 |
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h2 = hinf2 |
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vNa = v + vsna + KJ*m^3*h |
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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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m' = (minf - m)/mtau |
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h' = (hinf - h)/htau |
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m2' = (minf2 - m2)/mtau2 |
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h2' = (hinf2 - h2)/htau2 |
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vNa = v + vsna + KJ*m^3*h : note addition of vsna shift here so that we do not add it in rates |
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} |
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LOCAL qt |
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PROCEDURE rates(v) { :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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qt = q10^((celsius - 22)/10) : if you don't like room temp, it can be changed! |
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: average sodium channel |
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minf = 1 / (1+exp(-(v + 38 + vsna) / 7)) |
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hinf = 1 / (1+exp((v + 65 + vsna) / 6)) |
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mtau = (10 / (5*exp((v + 60 + vsna) / 18) + 36*exp(-(v + 60+vsna) / 25))) + 0.04 |
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mtau = mtau/qt |
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htau = (100 / (7*exp((v + 60 + vsna) / 11) + 10*exp(-(v + 60 + vsna) / 25))) + 0.6 |
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htau = htau/qt |
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: cooperative group of channels |
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minf2 = 1 / (1+exp(-(vNa + 38) / 7)) |
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hinf2 = 1 / (1+exp((vNa + 65) / 6)) |
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mtau2 = (10 / (5*exp((vNa+60) / 18) + 36*exp(-(vNa+60) / 25))) + 0.04 |
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mtau2 = mtau2/qt |
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htau2 = (100 / (7*exp((vNa+60) / 11) + 10*exp(-(vNa+60) / 25))) + 0.6 |
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htau2 = htau2/qt |
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} |
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UNITSON
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