Recorded conductance exceeding gbar value
Posted: Tue Jul 05, 2016 8:55 pm
I am playing with a potassium channel model I found on ModelDB (Gurkiewicz & Korngreen, 2007) with the end goal of building a calcium channel from scratch. Right now I'm trying to understand how to properly implement markov models by playing with the values of this model. I have coded a voltage step experiment (-80mv to +60mV in 20mV steps) and have 3 recording vectors:
reci.record(&soma.ik(0.5))
recg.record(&soma.g_k_3st(0.5))
rect.record(&t)
Where k_3st is the mechanism name that has been inserted into the soma. The model kinetics are as follows where I'm providing values for gbar as well as all the a and z variables in the hoc file.
I've noticed that at the highest voltage step of +60mV the max conductance value that occurs in the recording is 19.9258 however I've set the value for gbar in the hoc file as 19.8. I don't understand how this can occur when g = gbar*o and the max value of o is 1.
reci.record(&soma.ik(0.5))
recg.record(&soma.g_k_3st(0.5))
rect.record(&t)
Where k_3st is the mechanism name that has been inserted into the soma. The model kinetics are as follows where I'm providing values for gbar as well as all the a and z variables in the hoc file.
Code: Select all
STATE { c2 c1 o }
BREAKPOINT {
SOLVE states METHOD sparse
g = gbar*o
ik = (1e-4)*g*(v - ek)
}
INITIAL { SOLVE states STEADYSTATE sparse}
KINETIC states {
rates(v)
~c1 <-> o (k12,k21)
~c2 <-> c1 (k23,k32)
CONSERVE c2+c1+o=1
}
PROCEDURE rates(v(millivolt)) {
k12 = a12*exp(z12*v)
k21 = a21*exp(-z21*v)
k23 = a23*exp(z23*v)
k32 = a32*exp(-z32*v)
}