TITLE minimal model of NMDA receptors : PRETTY MUCH AS IN MATHILDE'S VERSION INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)} NEURON { SUFFIX NMDAKIT NONSPECIFIC_CURRENT i USEION ca READ cai WRITE ica RANGE onset,period, nbre, tau0, tau1, e, B, cao, gmax, g GLOBAL Erev, mg, temp, F, R } UNITS { (mA) = (milliamp) (mV) = (millivolt) (S) = (siemens) (mM) = (milli/liter) (celsius) = (degC) } PARAMETER { onset = 10 (ms) period = 50 (ms) nbre=20 tau0 = 2.0 (ms) tau1 = 26.0 (ms) cao = 1.5 (mM) : Ca concentration outside the cell cai (mM) : Ca concentration inside Erev = 0 (mV) : reversal potential gmax (S/cm2) : max conductance (100 pS single syn) mg = 1 (mM) : external magnesium concentration Px=4.6925 (cm3 mV/coulomb) :determined empirically such as 10% of the current is Ca2+ current at -40mV F = 96.49 (kilocoulomb) R = 8.314 (joule/degC) temp = 37 (degC) } ASSIGNED { ica (mA/cm2) : calcium current v (mV) : postsynaptic voltage i (mA/cm2) : potassium and sodium current = g*(v - Erev) g (S/cm2) : conductance of ca B : magnesium block } LOCAL a[2] LOCAL tpeak LOCAL adjust LOCAL amp BREAKPOINT { B = mgblock(v) : B is the block by magnesium at this voltage g = cond(t,onset) if (nbre>1) { FROM j=1 TO (nbre-1) { g=g+cond(t,onset+j*period) } } g=g*B ica = (0.001) * g * (0.051(cm3/coulomb)*v+Px) * (4.0*v*F*F / (R * (temp+273) )) * (-cao*exptable(-2*v*F/(R* (temp+273) )) + cai) / (1.0 - exptable(-2.0*v*F/(R* (temp+273) ))) i = g*(v - Erev) - ica } FUNCTION myexp(x) { if (x < -100) { myexp = 0 }else{ myexp = exp(x) } } FUNCTION cond(x (ms), onset1 (ms)) (S/cm2) { tpeak=tau0*tau1*log(tau0/tau1)/(tau0-tau1) adjust=1/((1-myexp(-tpeak/tau0))-(1-myexp(-tpeak/tau1))) amp=adjust*gmax if (x < onset1) { cond = 0 }else{ a[0]=1-myexp(-(x-onset1)/tau0) a[1]=1-myexp(-(x-onset1)/tau1) cond = amp*(a[0]-a[1]) } } FUNCTION exptable(x) { TABLE FROM -10 TO 10 WITH 2000 if ((x > -10) && (x < 10)) { exptable = exp(x) } else { exptable = 0. } } FUNCTION mgblock(v(mV)) { TABLE DEPEND mg FROM -140 TO 80 WITH 1000 : from Jahr & Stevens mgblock = 1 / (1 + exp(0.062 (/mV) * -v) * (mg / 3.57 (mM))) }