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111 lines
2.1 KiB
111 lines
2.1 KiB
TITLE Slow Ca-dependent potassium current |
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: Ca++ dependent K+ current IC responsible for slow AHP |
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: Differential equations |
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: Model based on a first order kinetic scheme |
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: <closed> + n cai <-> <open> (alpha,beta) |
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: Following this model, the activation fct will be half-activated at |
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: a concentration of Cai = (beta/alpha)^(1/n) = cac (parameter) |
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: The mod file is here written for the case n=2 (2 binding sites) |
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: --------------------------------------------- |
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: This current models the "slow" IK[Ca] (IAHP): |
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: - potassium current |
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: - activated by intracellular calcium |
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: - NOT voltage dependent |
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: A minimal value for the time constant has been added |
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: Ref: Destexhe et al., J. Neurophysiology 72: 803-818, 1994. |
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: Modifications by Arthur Houweling for use in MyFirstNEURON |
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INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)} |
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NEURON { |
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THREADSAFE |
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SUFFIX kpksk |
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USEION k READ ek WRITE ik |
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USEION ca READ cai |
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RANGE m_inf, tau_m, gbar, gk |
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GLOBAL beta, cac |
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RANGE ik |
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} |
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UNITS { |
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(mA) = (milliamp) |
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(mV) = (millivolt) |
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(molar) = (1/liter) |
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(mM) = (millimolar) |
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} |
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PARAMETER { |
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v (mV) |
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celsius (degC) |
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dt (ms) |
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ek (mV) |
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cai (mM) |
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gbar = .01 (mho/cm2) |
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beta = 0.002 (1/ms) : backward rate constant |
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cac = 0.010 (mM) : middle point of activation fct |
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taumin = 0.1 (ms) : minimal value of the time cst |
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} |
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STATE { |
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m |
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} |
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ASSIGNED { |
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ik (mA/cm2) |
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gk (mho/cm2) |
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m_inf |
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tau_m (ms) |
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tadj () |
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} |
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BREAKPOINT { |
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SOLVE states :METHOD euler |
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gk = gbar * m*m |
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ik = gk * (v - ek) |
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} |
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:DERIVATIVE states { |
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: evaluate_fct(v,cai) |
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: m'= (m_inf-m) / tau_m |
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:} |
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PROCEDURE states() { |
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evaluate_fct(v,cai) |
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m= m + (1-exp(-dt/tau_m))*(m_inf-m) |
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} |
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INITIAL { |
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: activation kinetics are assumed to be at 22 deg. C |
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: Q10 is assumed to be 3 |
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tadj = 3 ^ ((celsius-22.0)/10 (degC)) |
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evaluate_fct(v,cai) |
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m = m_inf |
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} |
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PROCEDURE evaluate_fct(v(mV),cai(mM)) { LOCAL car |
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car = (cai/cac)^2 |
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m_inf = car / ( 1 + car ) |
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tau_m = 1 / beta / (1 + car) / tadj |
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if(tau_m < taumin) { tau_m = taumin } : min value of time cst |
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}
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