TITLE potassium Kv3.1 membrane channel for STh
COMMENT
Potassium Kv3.1 membrane channel for STh. Based on derived kinetics
from Wigmore & Lacey 2000. Their primary experiments were performed
at 32degC
How the q10 works: There is a q10 for the rates (alpha and beta's)
called Q10 and a Q10 for the maximum conductance called gmaxQ10. The
q10s should have been measured at specific temperatures temp1 and
temp2 (that are 10degC apart). Ideally, as Q10 is temperature
dependant, we should know these two temperatures. We are going to
follow the more formal Arrhenius derived Q10 approach. The
temperature at which this channel's kinetics were recorded is tempb
(base temperature). What we then need to calculate is the desired
rate scale for now working at temperature celsius (rate_k). This is
given by the empirical Arrhenius equation, using the Q10.
ENDCOMMENT
UNITS {
(mV) = (millivolt)
(mA) = (milliamp)
}
INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}
NEURON {
SUFFIX Kv31
USEION k READ ki,ek WRITE ik
RANGE gk
GLOBAL activate_Q10,Q10,gmaxQ10,rate_k,gmax_k,temp1,temp2,tempb
}
PARAMETER {
v (mV)
dt (ms)
gk = 0.015 (mho/cm2)
ek
ki
celsius
activate_Q10 = 1
Q10 = 1.700025939e+00
gmaxQ10 = 1.700025939e+00
temp1 = 20.0 (degC)
temp2 = 30.0 (degC)
tempb = 32.0 (degC)
}
STATE {
p
}
ASSIGNED {
ik (mA/cm2)
pinf
ptau (ms)
rate_k
gmax_k
}
BREAKPOINT {
SOLVE states METHOD cnexp
ik = (gk*gmax_k)*p*(vek)
}
UNITSOFF
INITIAL {
LOCAL ktemp,ktempb,ktemp1,ktemp2
if (activate_Q10>0) {
ktemp = celsius+273.0
ktempb = tempb+273.0
ktemp1 = temp1+273.0
ktemp2 = temp2+273.0
rate_k = exp( log(Q10)*((1/ktempb)(1/ktemp))/((1/ktemp1)(1/ktemp2)) )
gmax_k = exp( log(gmaxQ10)*((1/ktempb)(1/ktemp))/((1/ktemp1)(1/ktemp2)) )
}else{
rate_k = 1.0
gmax_k = 1.0
}
settables(v)
p = pinf
}
DERIVATIVE states {
settables(v)
p' = (pinfp)/ptau
}
PROCEDURE settables(v) {:Computes rate and other constants at current v.
:Call once from HOC to initialize inf at resting v.
:Voltage shift (for temp effects) of 5.08
TABLE pinf, ptau DEPEND celsius FROM 100 TO 100 WITH 400
pinf = 1.0/(1.0+exp((v + 0.083699749)/ 9.0))
ptau = ((7.3/(exp((v + 32.9163003)/14.0)+exp((v + 2.91630025)/16.0)))+1) / rate_k
}
UNITSON
