TITLE high threshold calcium current (L-current) COMMENT ********************************************* reference: McCormick & Huguenard (1992) J.Neurophysiology 68(4), 1384-1400 found in: hippocampal pyramidal cells ********************************************* Assembled for MyFirstNEURON by Arthur Houweling ENDCOMMENT INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)} NEURON { SUFFIX iL USEION ca READ cai,cao WRITE ica RANGE pcabar, m_inf, tau_m, ica } UNITS { (mA) = (milliamp) (mV) = (millivolt) (mM) = (milli/liter) FARADAY = 96480 (coul) R = 8.314 (volt-coul/degC) } PARAMETER { v (mV) celsius (degC) dt (ms) cai (mM) cao (mM) pcabar= 0.000276 (cm/s) } STATE { m } ASSIGNED { ica (mA/cm2) tau_m (ms) m_inf tadj } BREAKPOINT { SOLVE states :METHOD euler ica = pcabar * m*m * ghk(v,cai,cao,2) } :DERIVATIVE states { : rates(v) : : m'= (m_inf-m) / tau_m :} PROCEDURE states() { rates(v) m= m + (1-exp(-dt/tau_m))*(m_inf-m) } UNITSOFF INITIAL { tadj = 3^((celsius-23.5)/10) rates(v) m = m_inf } FUNCTION ghk( v(mV), ci(mM), co(mM), z) (millicoul/cm3) { LOCAL e, w w = v * (.001) * z*FARADAY / (R*(celsius+273.16)) if (fabs(w)>1e-4) { e = w / (exp(w)-1) } else : denominator is small -> Taylor series { e = 1-w/2 } ghk = - (.001) * z*FARADAY * (co-ci*exp(w)) * e } UNITSOFF PROCEDURE rates(v(mV)) { LOCAL a,b a = 1.6 / (1+ exp(-0.072*(v-5))) b = 0.02 * vtrap( -(v-1.31), 5.36) tau_m = 1/(a+b) / tadj m_inf = 1/(1+exp((v+10)/-10)) } FUNCTION vtrap(x,c) { : Traps for 0 in denominator of rate equations if (fabs(x/c) < 1e-6) { vtrap = c + x/2 } else { vtrap = x / (1-exp(-x/c)) } } UNITSON