TITLE Axon Node channels : : Based on axon model from McIntyre2004 : : Fast Na+, Persistant Na+, Slow K+, and Leakage currents : responsible for nodal action potential : Iterative equations H-H notation rest = -75 mV INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)} NEURON { SUFFIX axnode75 NONSPECIFIC_CURRENT ina NONSPECIFIC_CURRENT inap NONSPECIFIC_CURRENT ik NONSPECIFIC_CURRENT il RANGE gnapbar, gnabar, gkbar, gl, ena, ek, el RANGE mp_inf, m_inf, h_inf, s_inf RANGE tau_mp, tau_m, tau_h, tau_s } UNITS { (mA) = (milliamp) (mV) = (millivolt) } PARAMETER { gnapbar = 0.01 (mho/cm2) gnabar = 3.0 (mho/cm2) gkbar = 0.08 (mho/cm2) gl = 0.007 (mho/cm2) ena = 55.0 (mV) ek = -85.0 (mV) el = -85.0 (mV) celsius (degC) dt (ms) v (mV) vshift=5 vtraub=-80 ampA = 0.01 ampB = 27 ampC = 10.2 bmpA = 0.00025 bmpB = 34 bmpC = 10 amA = 1.86 amB = 21.4 amC = 10.3 bmA = 0.086 bmB = 25.7 bmC = 9.16 ahA = 0.062 ahB = 114.0 ahC = 11.0 bhA = 2.3 bhB = 31.8 bhC = 13.4 asA = 0.3 asB = -27 asC = -5 bsA = 0.03 bsB = 10 bsC = -1 } STATE { mp m h s } ASSIGNED { inap (mA/cm2) ina (mA/cm2) ik (mA/cm2) il (mA/cm2) mp_inf m_inf h_inf s_inf tau_mp tau_m tau_h tau_s q10_1 q10_2 q10_3 } BREAKPOINT { SOLVE states METHOD cnexp inap = gnapbar * mp*mp*mp * (v - ena) ina = gnabar * m*m*m*h * (v - ena) ik = gkbar * s * (v - ek) il = gl * (v - el) } DERIVATIVE states { : exact Hodgkin-Huxley equations evaluate_fct(v) mp'= (mp_inf - mp) / tau_mp m' = (m_inf - m) / tau_m h' = (h_inf - h) / tau_h s' = (s_inf - s) / tau_s } UNITSOFF INITIAL { :Q10 adjustment q10_1 = 2.2 ^ ((celsius-20)/ 10 ) q10_2 = 2.9 ^ ((celsius-20)/ 10 ) q10_3 = 3.0 ^ ((celsius-36)/ 10 ) evaluate_fct(v) mp = mp_inf m = m_inf h = h_inf s = s_inf } PROCEDURE evaluate_fct(v(mV)) { LOCAL a,b,v2 v2 = v - vshift a = q10_1*vtrap1(v2) b = q10_1*vtrap2(v2) tau_mp = 1 / (a + b) mp_inf = a / (a + b) a = q10_1*vtrap6(v2) b = q10_1*vtrap7(v2) tau_m = 1 / (a + b) m_inf = a / (a + b) a = q10_2*vtrap8(v2) b = q10_2*bhA / (1 + Exp(-(v2+bhB)/bhC)) tau_h = 1 / (a + b) h_inf = a / (a + b) a = q10_3*asA / (Exp((v2-vtraub+asB)/asC) + 1) b = q10_3*bsA / (Exp((v2-vtraub+bsB)/bsC) + 1) tau_s = 1 / (a + b) s_inf = a / (a + b) } FUNCTION vtrap(x) { if (x < -50) { vtrap = 0 }else{ vtrap = bsA / (Exp((x+bsB)/bsC) + 1) } } FUNCTION vtrap1(x) { if (fabs((x+ampB)/ampC) < 1e-6) { vtrap1 = ampA*ampC }else{ vtrap1 = (ampA*(x+ampB)) / (1 - Exp(-(x+ampB)/ampC)) } } FUNCTION vtrap2(x) { if (fabs((x+bmpB)/bmpC) < 1e-6) { vtrap2 = bmpA*bmpC : Ted Carnevale bug fix removed minus sign }else{ vtrap2 = (bmpA*(-(x+bmpB))) / (1 - Exp((x+bmpB)/bmpC)) } } FUNCTION vtrap6(x) { if (fabs((x+amB)/amC) < 1e-6) { vtrap6 = amA*amC }else{ vtrap6 = (amA*(x+amB)) / (1 - Exp(-(x+amB)/amC)) } } FUNCTION vtrap7(x) { if (fabs((x+bmB)/bmC) < 1e-6) { vtrap7 = bmA*bmC : Ted Carnevale bug fix removed minus sign }else{ vtrap7 = (bmA*(-(x+bmB))) / (1 - Exp((x+bmB)/bmC)) } } FUNCTION vtrap8(x) { if (fabs((x+ahB)/ahC) < 1e-6) { vtrap8 = ahA*ahC : Ted Carnevale bug fix removed minus sign }else{ vtrap8 = (ahA*(-(x+ahB))) / (1 - Exp((x+ahB)/ahC)) } } FUNCTION Exp(x) { if (x < -100) { Exp = 0 }else{ Exp = exp(x) } } UNITSON