TITLE P calcium current (not inactivate) 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 CaP2 USEION ca READ cai, cao WRITE ica RANGE gcabar, ica, gca, minf, mexp } INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)} PARAMETER { v (mV) celsius = 37 (degC) dt (ms) gcabar = .0045 (mho/cm2) eca = 135 (mV) cai = 0.40e-4 (mM) : adjusted for eca=135mV cao = 2.4 (mM) } STATE { m h } ASSIGNED { ica (mA/cm2) gca minf mexp } BREAKPOINT { SOLVE states gca = gcabar * m ica = gca* (v-eca) } UNITSOFF INITIAL { rates(v) m = minf } PROCEDURE states() { :Computes state variables 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 -100 TO 100 WITH 200 q10 = 3^((celsius - 37)/10) tinc = -dt * q10 :"m" calcium activation system alpha = 8.5/(1+exp((v-8)/(-12.5))) beta = 35/(1+exp((v+74)/14.5)) sum = alpha + beta minf = alpha/sum mexp = 1 - exp(tinc*sum) } UNITSON