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110 lines
2.2 KiB
110 lines
2.2 KiB
2 years ago
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TITLE CaPCalyx.mod The presynaptic calcium current at the MNTB calyx of Held
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COMMENT
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NEURON implementation of Calcium current from Borst and Sakmann, 1998.
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Equations are basic HH; parameters are taken from Figure 8 legend in that paper.
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Original implementation by Paul B. Manis, October 2007
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Contact: pmanis@med.unc.edu
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Modified 2/2014: Use Derivative block format.
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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 CaPCalyx
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USEION ca READ eca WRITE ica
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RANGE gbar, gcap, ica
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GLOBAL minf, taum, alpha, beta
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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 = 22 (degC) : model is defined on measurements made at 23-24 deg in Germany
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celsius (degC)
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dt (ms)
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: eca = 43.9 (mV)
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eca (mV)
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gbar = 0.01 (mho/cm2) <0,1e9> : target is 48.9 nS total
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alpha (1/ms)
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beta (1/ms)
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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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ica (mA/cm2)
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gcap (mho/cm2)
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minf (1)
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taum (ms)
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}
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LOCAL mexp
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BREAKPOINT {
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SOLVE states METHOD cnexp
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gcap = gbar*m*m
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ica = gcap*(v - eca)
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}
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UNITSOFF
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INITIAL {
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trates(v)
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m = minf
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}
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DERIVATIVE states { : Computes state variables m
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rates(v) : at the current v and dt.
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m' = (minf - m)/taum
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:m = m + mexp*(minf-m)
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:VERBATIM
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: return 0;
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:ENDVERBATIM
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}
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LOCAL q10
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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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q10 = 3^((celsius - 24)/10) : if you don't like room temp, it can be changed!
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minf = (1 / (1 + exp(-(v + 23.2) / 9.1)))
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alpha = 1.78*exp(v/23.3)
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beta = 0.140*exp(-v/15.0)
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taum = 1/(alpha + beta)
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}
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PROCEDURE trates(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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LOCAL minc
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TABLE minf, mexp
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DEPEND dt, celsius FROM -150 TO 150 WITH 300
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rates(v) : not consistently executed from here if usetable_hh == 1
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: so don't expect the tau values to be tracking along with
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: the inf values in hoc
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minc = -dt * q10
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mexp = 1 - exp(minc/taum)
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}
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UNITSON
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