/* Na channel * fills tables with values for alpha and beta and then * uses tweakalpha to alter the values to A and B * values for alpha and beta are taken from: * J. Neurophysiology 82: 2476-2389, 1999 * on page 2478 * * the functions below convert to physiological units to do the * calulations and convert back to SI units for the output */ /* alpha for the type X gate (activation) */ function NaChanAlphaX(voltage) float voltage = {voltage} * 1e3 /* convert to mV */ float num = {3020 - {40 * {voltage}}} float denom = {{exp {{-75.5 + {voltage}} / {-13.5}}} - 1} /* convert sec to msec */ float act = {{num} / {denom}} * 1e3 return act end /* beta for the type X gate (activation) */ function NaChanBetaX(voltage) float voltage = {voltage} * 1e3 /* convert to mV */ //echo NaBetaXVoltage: {voltage} float num = 1.2262 float denom = {exp {{voltage} / 42.248}} /* convert sec to msec */ float act = {{num} / {denom}} * 1e3 return act end /* alpha for the type Y gate (inactivation) */ function NaChanAlphaY(voltage) float voltage = voltage * 1e3 /* convert to mV */ float num = 0.0035 float denom = {exp {{voltage} / 24.186}} /* convert sec to msec */ float act = {{num} / {denom}} * 1e3 return act end function NaChanBetaY(voltage) float voltage = voltage * 1e3 float num = {-{0.8712 + {0.017 * {voltage}}}} float denom = {{exp {{51.25 + voltage} / -5.2}} - 1} /* convert sec to msec */ float act = {{num} / {denom}} * 1e3 return act end function make_Na_channel float Erev = 0.045 /* reversal potential of sodium */ str path = "Na_channel" float xmin = -0.1 /* minimum voltage we will see in the simulation */ float xmax = 0.05 /* maximum voltage we will see in the simulation */ float step = 0.005 /* use a 5mV step size */ int xdivs = 30 /* the number of divisions between -0.1 and 0.05 */ int c = 0 float y create tabchannel {path} /* make the table for the activation with a range of -100mV - +50mV * with an entry for ever 5mV */ call {path} TABCREATE X {xdivs} {xmin} {xmax} call {path} TABCREATE Y {xdivs} {xmin} {xmax} /* set the tau and m_inf for the activation and inactivation */ for(c = 0; c < {xdivs} + 1; c = c + 1) setfield {path} X_A->table[{c}] {NaChanAlphaX {{c * {step}} + xmin}} setfield {path} X_B->table[{c}] {NaChanBetaX {{c * {step}} + xmin}} setfield {path} Y_A->table[{c}] {NaChanAlphaY {{c * {step}} + xmin}} setfield {path} Y_B->table[{c}] {NaChanBetaY {{c * {step}} + xmin}} end /* for testing */ //for(c = 0; c < 30; c = c + 1) // showfield {path} X_A->table[{c}] // showfield {path} X_B->table[{c}] // showfield {path} Y_A->table[{c}] // showfield {path} Y_B->table[{c}] // end //for(c = 0; c < 30; c = c + 1) // y = {call Na_channel CALC_ALPHA X {c}} // return y // end setfield {path} Ek {Erev} Xpower 3 Ypower 1 /* fill the tables with the values of A and B * calculated from alpha and beta */ tweakalpha {path} X tweakalpha {path} Y call {path} TABFILL X 3000 0 call {path} TABFILL Y 3000 0 setfield {path} X_A->calc_mode 0 X_B->calc_mode 0 setfield {path} Y_A->calc_mode 0 Y_B->calc_mode 0 end