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ih.mod
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ih.mod
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COMMENTih.modHyperpolarization-activated channel; mixed cation current; Hodgkin-Huxley style kinetics. Based on results from Magee, 1998. (J. Neurosci. 18(19):7613-7624. 1 October, 1998.Authors: Tim Mickus, Bill Kath, Nelson Spruston: Northwestern University, 2000.Modification of original Iq model by Nelson Spruston, used in Stuart & Spruston, 1998.That file was originally modified from one provided by Michele Migliore.Modified 8/16/02 to work with CVODE (one day, I hope) - NelsonENDCOMMENTTITLE H currentINDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}NEURON { THREADSAFE SUFFIX h NONSPECIFIC_CURRENT Ih RANGE Ih, gbar GLOBAL inf,tau}PARAMETER { gbar=8.0 (pS/um2) : maximum conductance : ranges from 8-10 pS/um2 in dend, 1-2 pS/um2 in soma (Magee, 1998, p. 7615) erevh=-13 (mV) : this value from Magee, table 1 higher Na+ (nelson used -35) vhalf=-81 (mV) : this value from Magee, table 1 higher Na+ (nelson used -88) a0=0.00057 (/ms) : this is essentially a scale factor for the time constant zeta=7 (1) ab=0.4 (1) qten=4.5 (1) : Magee value 4.5 activation, 4.7 deactivation v (mV) dt (ms) temp = 33 (degC) : reference temperature from Magee 1998 gas = 8.315 (J/degC) : universal gas constant (joules/mol/K) farad = 9.648e4 (coul) : Faraday's constant (coulombs/mol)}UNITS { (mA) = (milliamp) (mV) = (millivolt) (mM) = (milli/liter) (S) = (siemens) (pS) = (picosiemens) (um) = (micron) (J) = (joules)}ASSIGNED { Ih (mA/cm2) inf tau (ms) celsius (degC) : actual temperature for simulation, defined in Neuron, usually about 35}STATE { hh}INITIAL { rate(v) hh=inf}FUNCTION alpha(v(mV)) (1/ms) { alpha = a0*exp((0.001)*(-ab)*zeta*(v-vhalf)*farad/(gas*(273.16+celsius))) }FUNCTION beta(v(mV)) (1/ms) { beta = a0*exp((0.001)*(1-ab)*zeta*(v-vhalf)*farad/(gas*(273.16+celsius)))}BREAKPOINT { SOLVE state METHOD cnexp Ih = (0.0001)*gbar*hh*(v-erevh)}DERIVATIVE state { rate(v) hh' = (inf-hh)/tau}PROCEDURE rate(v (mV)) { : callable from hoc LOCAL a, b, q10 q10 = qten^((celsius-temp)/10(degC)) a = q10*alpha(v) b = q10*beta(v) inf = a/(a+b) tau = 1/(a+b) if (tau<2) {tau=2}}