: iC fast Ca2+/V-dependent K+ channel NEURON { SUFFIX iCin USEION k READ ki, ko WRITE ik USEION ca READ cai RANGE ik, gk, gkcbar } UNITS { (mM) = (milli/liter) (mA) = (milliamp) (mV) = (millivolt) } INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)} PARAMETER { v (mV) dt (ms) cai (mM) gkcbar= 0.0022 (mho/cm2) } STATE { c } ASSIGNED { ik (mA/cm2) cinf ctau (ms) gk (mho/cm2) ek (mV) ki (mM) ko (mM) } INITIAL { rate() c = cinf } BREAKPOINT { SOLVE states METHOD cnexp gk = gkcbar*c*c ek = 25 * log(ko/ki) ik = gk*(v-ek) } DERIVATIVE states { rate() c' = (cinf-c)/ctau } UNITSOFF FUNCTION calf(v (mV), cai (mM)) (/ms) { LOCAL vs, va vs=v+40*log10(1000*cai) :1000*cai va=vs+18 if (fabs(va)<1e-04){ va=va+0.0001 } calf = (-0.00642*vs-0.1152)/(-1+exp(-va/12)) } FUNCTION cbet(v (mV), cai (mM))(/ms) { LOCAL vs, vb vs=v+40*log10(cai*1000) vb=vs+152 if (fabs(vb)<1e-04){ vb=vb+0.0001 } cbet = 1.7*exp(-vb/30) } UNITSON PROCEDURE rate() {LOCAL csum, ca, cb ca=calf(v, cai) cb=cbet(v, cai) csum = ca+cb cinf = ca/csum if ((1/csum)>1.1) { ctau = 1 / csum} else { ctau = 1.1 } }