TITLE T-calcium channel : T-type calcium channel UNITS { (mA) = (milliamp) (mV) = (millivolt) FARADAY = 96520 (coul) R = 8.3134 (joule/degC) KTOMV = .0853 (mV/degC) } PARAMETER { v (mV) celsius = 6.3 (degC) gcatbar=.003 (mho/cm2) cai (mM) cao (mM) } NEURON { SUFFIX cat3 USEION ca READ cai,cao WRITE ica RANGE gcatbar,cai } STATE { m h } ASSIGNED { ica (mA/cm2) gcat (mho/cm2) } INITIAL { m = minf(v) h = hinf(v) } BREAKPOINT { SOLVE states METHOD cnexp gcat = gcatbar*m*m*h ica = gcat*ghk(v,cai,cao) } DERIVATIVE states { : exact when v held constant m' = (minf(v) - m)/m_tau(v) h' = (hinf(v) - h)/h_tau(v) } FUNCTION ghk(v(mV), ci(mM), co(mM)) (mV) { LOCAL nu,f f = KTF(celsius)/2 nu = v/f ghk=-f*(1. - (ci/co)*exp(nu))*efun(nu) } FUNCTION KTF(celsius (DegC)) (mV) { KTF = ((25./293.15)*(celsius + 273.15)) } FUNCTION efun(z) { if (fabs(z) < 1e-4) { efun = 1 - z/2 }else{ efun = z/(exp(z) - 1) } } FUNCTION hinf(v(mV)) { LOCAL a,b TABLE FROM -150 TO 150 WITH 200 a = 1.e-6*exp(-v/16.26) b = 1/(exp((-v+29.79)/10.)+1.) hinf = a/(a+b) } FUNCTION minf(v(mV)) { LOCAL a,b TABLE FROM -150 TO 150 WITH 200 a = 0.2*(-1.0*v+19.26)/(exp((-1.0*v+19.26)/10.0)-1.0) b = 0.009*exp(-v/22.03) minf = a/(a+b) } FUNCTION m_tau(v(mV)) (ms) { LOCAL a,b TABLE FROM -150 TO 150 WITH 200 a = 0.2*(-1.0*v+19.26)/(exp((-1.0*v+19.26)/10.0)-1.0) b = 0.009*exp(-v/22.03) m_tau = 1/(a+b) } FUNCTION h_tau(v(mV)) (ms) { LOCAL a,b TABLE FROM -150 TO 150 WITH 200 a = 1.e-6*exp(-v/16.26) b = 1/(exp((-v+29.79)/10.)+1.) h_tau = 1/(a+b) }