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NaP.mod
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NaP.mod
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TITLE Persistent sodium current
COMMENT
from "An Active Membrane Model of the Cerebellar Purkinje Cell
1. Simulation of Current Clamp in Slice"
ENDCOMMENT
UNITS {
(mA) = (milliamp)
(mV) = (millivolt)
}
NEURON {
SUFFIX NaP
USEION na WRITE ina
RANGE gnabar, gna, minf
}
INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}
PARAMETER {
v (mV)
celsius = 37 (degC)
ena = 45 (mV)
gnabar = 0.001 (mho/cm2)
dt
}
STATE {
m
}
ASSIGNED {
ina (mA/cm2)
minf
mexp
gna
}
BREAKPOINT {
SOLVE states
gna = gnabar*m*m*m
ina = gna*(v - ena)
}
UNITSOFF
INITIAL {
rates(v)
m = minf
}
PROCEDURE states() { :Computes states variable m
rates(v) : at the current v and dt.
m = m + mexp*(minf-m)
}
PROCEDURE rates(v) { :Computes rate and other constants at current v.
:Call once from HOC to initialize inf at resting v.
LOCAL q10, tinc, alpha, beta, sum
TABLE minf, mexp DEPEND dt, celsius FROM -400 TO 300 WITH 700
q10 = 3^((celsius - 37)/10)
tinc = -dt * q10
:"m" sodium activation system
alpha = 200/(1+exp((v-18)/(-16)))
beta = 25/(1+exp((v+58)/8))
sum = alpha + beta
minf = alpha/sum
mexp = 1 - exp(tinc*sum)
}
UNITSON