TITLE P-type calcium channel
COMMENT
NEURON implementation of a P-type calcium channel
Kinetical scheme: Hodgkin-Huxley (m), no inactivation
Modified from Khaliq et al., J. Neurosci. 23(2003)4899
Laboratory for Neuronal Circuit Dynamics
RIKEN Brain Science Institute, Wako City, Japan
http://www.neurodynamics.brain.riken.jp
Reference: Akemann and Knoepfel, J.Neurosci. 26 (2006) 4602
Date of Implementation: May 2005
Contact: akemann@brain.riken.jp
ENDCOMMENT
NEURON {
SUFFIX pcCaP
USEION ca READ cai, cao WRITE ica
RANGE pcabar, ica, ghk_value
GLOBAL minf, taum
GLOBAL monovalConc, monovalPerm
}
UNITS {
(mV) = (millivolt)
(mA) = (milliamp)
(nA) = (nanoamp)
(pA) = (picoamp)
(S) = (siemens)
(nS) = (nanosiemens)
(pS) = (picosiemens)
(um) = (micron)
(molar) = (1/liter)
(mM) = (millimolar)
}
CONSTANT {
q10 = 2.2
F = 9.6485e4 (coulombs)
R = 8.3145 (joule/kelvin)
cv = 19 (mV)
ck = 5.5 (mV)
}
PARAMETER {
v (mV)
celsius (degC)
cai (mM)
cao (mM)
pcabar = 6e-5 (cm/s)
monovalConc = 140 (mM)
monovalPerm = 0
}
ASSIGNED {
qt
ica (mA/cm2)
minf
taum (ms)
T (kelvin)
E (volt)
zeta
ghk_value
}
STATE { m }
INITIAL {
qt = q10^((celsius-22 (degC))/10 (degC))
T = kelvinfkt( celsius )
rates(v)
m = minf
}
BREAKPOINT {
SOLVE states METHOD cnexp
ica = (1e3) * pcabar * m * ghk(v, cai, cao, 2)
ghk_value = ghk(v, cai, cao, 2)
}
DERIVATIVE states {
rates(v)
m' = (minf-m)/taum
}
FUNCTION ghk( v (mV), ci (mM), co (mM), z ) (coulombs/cm3) {
E = (1e-3) * v
zeta = (z*F*E)/(R*T)
: ci = ci + (monovalPerm) * (monovalConc) :Monovalent permeability
if ( fabs(1-exp(-zeta)) < 1e-6 ) {
ghk = (1e-6) * (z*F) * (ci - co*exp(-zeta)) * (1 + zeta/2)
} else {
ghk = (1e-6) * (z*zeta*F) * (ci - co*exp(-zeta)) / (1-exp(-zeta))
}
}
PROCEDURE rates( v (mV) ) {
minf = 1 / ( 1 + exp(-(v+cv)/ck) )
taum = (1e3) * taumfkt(v)/qt
}
FUNCTION taumfkt( v (mV) ) (s) {
UNITSOFF
if ( v > -50 ) {
taumfkt = 0.000191 + 0.00376 * exp(-((v+41.9)/27.8)^2)
} else {
taumfkt = 0.00026367 + 0.1278 * exp(0.10327*v)
}
UNITSON
}
FUNCTION kelvinfkt( t (degC) ) (kelvin) {
UNITSOFF
kelvinfkt = 273.19 + t
UNITSON
}