TITLE R-type calcium current (Cav2.3)
COMMENT
neuromodulation is added as functions:
modulation = 1 + damod*(maxMod-1)*level
where:
damod [0]: is a switch for turning modulation on or off {1/0}
maxMod [1]: is the maximum modulation for this specific channel (read from the param file)
e.g. 10% increase would correspond to a factor of 1.1 (100% +10%) {0-inf}
level [0]: is an additional parameter for scaling modulation.
Can be used simulate non static modulation by gradually changing the value from 0 to 1 {0-1}
[] == default values
{} == ranges
ENDCOMMENT
UNITS {
(mV) = (millivolt)
(mA) = (milliamp)
(S) = (siemens)
(molar) = (1/liter)
(mM) = (millimolar)
FARADAY = (faraday) (coulomb)
R = (k-mole) (joule/degC)
}
NEURON {
SUFFIX car
USEION ca READ cai, cao WRITE ica VALENCE 2
RANGE pbar, ica
RANGE damod, maxMod, level, max2, lev2
}
PARAMETER {
pbar = 0.0 (cm/s)
:q = 1 : room temperature 22 C
q = 3 : body temperature 35 C
damod = 0
maxMod = 1
level = 0
max2 = 1
lev2 = 0
}
ASSIGNED {
v (mV)
ica (mA/cm2)
eca (mV)
celsius (degC)
cai (mM)
cao (mM)
minf
mtau (ms)
hinf
htau (ms)
}
STATE { m h }
BREAKPOINT {
SOLVE states METHOD cnexp
ica = pbar*m*m*m*h*ghk(v, cai, cao) *modulation()
}
INITIAL {
rates()
m = minf
h = hinf
}
DERIVATIVE states {
rates()
m' = (minf-m)/mtau*q
h' = (hinf-h)/htau*q
}
PROCEDURE rates() {
UNITSOFF
minf = 1/(1+exp((v-(-29))/(-9.6)))
mtau = 5.1*3
hinf = 1/(1+exp((v-(-33.3))/17))
htau = 22+80/(1+exp((v-(-19))/5))
UNITSON
}
FUNCTION ghk(v (mV), ci (mM), co (mM)) (.001 coul/cm3) {
LOCAL z, eci, eco
z = (1e-3)*2*FARADAY*v/(R*(celsius+273.15))
if(z == 0) {
z = z+1e-6
}
eco = co*(z)/(exp(z)-1)
eci = ci*(-z)/(exp(-z)-1)
ghk = (1e-3)*2*FARADAY*(eci-eco)
}
FUNCTION modulation() {
: returns modulation factor
modulation = 1 + damod * ( (maxMod-1)*level + (max2-1)*lev2 )
if (modulation < 0) {
modulation = 0
}
}
COMMENT
Original data by Foehring et al (2000) [1] for dissociated MSNs from
P28-P42 Sprague-Dawley rat brain. Unspecified recording temperature. The
liquid junction potential was around 8 mV and was not corrected. Kinetics
of m3h type was fitted. Inactivation time constants were measured in
neurons from endopiriform nucleus of P7-P21 Hartley guinea pigs [2]
at room temperature 22 C.
Original NEURON model by Wolf (2005) [3] modified by Alexander Kozlov
. Activation curve fitted to m3 kinetics [4],
activation time constant scaled up as well. Smooth fit of inactivation
time constant from [2,3].
[1] Foehring RC, Mermelstein PG, Song WJ, Ulrich S, Surmeier DJ
(2000) Unique properties of R-type calcium currents in neocortical and
neostriatal neurons. J Neurophysiol 84(5):2225-36.
[2] Brevi S, de Curtis M, Magistretti J (2001) Pharmacological and
biophysical characterization of voltage-gated calcium currents in the
endopiriform nucleus of the guinea pig. J Neurophysiol 85(5):2076-87.
[3] Wolf JA, Moyer JT, Lazarewicz MT, Contreras D, Benoit-Marand M,
O'Donnell P, Finkel LH (2005) NMDA/AMPA ratio impacts state transitions
and entrainment to oscillations in a computational model of the nucleus
accumbens medium spiny projection neuron. J Neurosci 25(40):9080-95.
[4] Evans RC, Maniar YM, Blackwell KT (2013) Dynamic modulation of
spike timing-dependent calcium influx during corticostriatal upstates. J
Neurophysiol 110(7):1631-45.
ENDCOMMENT