TITLE H-current that uses Na ions NEURON { SUFFIX h RANGE gbar,vhalf, K, taun, ninf, g USEION na READ ena WRITE ina : NONSPECIFIC_CURRENT i } UNITS { (um) = (micrometer) (mA) = (milliamp) (uA) = (microamp) (mV) = (millivolt) (pmho) = (picomho) (mmho) = (millimho) } PARAMETER { : parameters that can be entered when function is called in cell-setup dt (ms) v (mV) ena = 50 (mV) eh = -10 (mV) K = 8.5 (mV) gbar = 0 (mho/cm2) : initialize conductance to zero :vhalf = -90 (mV) : half potential vhalf = -81 (mV) : half potential } STATE { : the unknown parameters to be solved in the DEs n } ASSIGNED { : parameters needed to solve DE ina (mA/cm2) ninf taun (ms) g } INITIAL { : initialize the following parameter using states() states() n = ninf g = gbar*n ina = g*(v-eh) } BREAKPOINT { SOLVE h METHOD derivimplicit g = gbar*n ina = g*(v-eh) } DERIVATIVE h { states() n' = (ninf - n)/taun } PROCEDURE states() { if (v > -30) { taun = 1 } else { :taun = 2*(1/(exp((v+145)/-17.5)+exp((v+16.8)/16.5)) + 5) :h activation tau taun = 5*(1/(exp((v+145)/-17.5)+exp((v+16.8)/16.5)) + 5) :h activation tau } ninf = 1 - (1 / (1 + exp((vhalf - v)/K))) :steady state value }