: \$Id: netcon.inc,v 1.10 2004/07/28 20:41:24 billl Exp \$ COMMENT USAGE: for most receptors ***************************************************************************** NEURON { POINT_PROCESS NAME } PARAMETER { Cdur = 1.08 (ms) : transmitter duration (rising phase) Alpha = 1 (/ms mM) : forward (binding) rate Beta = 0.02 (/ms) : backward (unbinding) rate Erev = -80 (mV) : reversal potential } INCLUDE "netsyn.inc" ***************************************************************************** USAGE: for NMDA receptor ***************************************************************************** NEURON{ POINT_PROCESS NMDA RANGE B } PARAMETER { mg = 1. (mM) : external magnesium concentration Cdur = 1. (ms) : transmitter duration (rising phase) Alpha = 4. (/ms mM) : forward (binding) rate Beta = 0.0067 (/ms) : backward (unbinding) rate 1/150 Erev = 0. (mV) : reversal potential } ASSIGNED { B } INCLUDE "netcon.inc" : EXTRA BREAKPOINT MUST BE BELOW THE INCLUDE BREAKPOINT { rates(v) g = g * B : but don't really need to readjust conductance i = i * B : i = g*(v - Erev) } PROCEDURE rates(v(mV)) { TABLE B DEPEND mg FROM -100 TO 80 WITH 180 B = 1 / (1 + Exp1(0.062 (/mV) * -v) * (mg / 3.57 (mM))) } ***************************************************************************** ENDCOMMENT INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)} NEURON { RANGE g, Erev NONSPECIFIC_CURRENT i GLOBAL Cdur, Alpha, Beta, Rinf, Rtau } UNITS { (nA) = (nanoamp) (mV) = (millivolt) (umho) = (micromho) (mM) = (milli/liter) } ASSIGNED { v (mV) : postsynaptic voltage i (nA) : current = g*(v - Erev) g (umho) : conductance Rinf : steady state channels open Rtau (ms) : time constant of channel binding synon } STATE {Ron Roff} INITIAL { Rinf = Alpha / (Alpha + Beta) Rtau = 1 / (Alpha + Beta) synon = 0 } BREAKPOINT { SOLVE release METHOD cnexp g = (Ron + Roff)*1(umho) i = g*(v - Erev) } DERIVATIVE release { Ron' = (synon*Rinf - Ron)/Rtau Roff' = -Beta*Roff } : following supports both saturation from single input and : summation from multiple inputs : if spike occurs during CDur then new off time is t + CDur : ie. transmitter concatenates but does not summate : Note: automatic initialization of all reference args to 0 except first NET_RECEIVE(weight, on, nspike, r0, t0 (ms)) { : flag is an implicit argument of NET_RECEIVE and normally 0 if (t>0) { : bug fix so that init doesn't send a false event if (flag == 0) { : a spike, so turn on if not already in a Cdur pulse nspike = nspike + 1 if (!on) { r0 = r0*Exp1(-Beta*(t - t0)) t0 = t on = 1 synon = synon + weight Ron = Ron + r0 Roff = Roff - r0 } : come again in Cdur with flag = current value of nspike net_send(Cdur, nspike) } if (flag == nspike) { : if this associated with last spike then turn off r0 = weight*Rinf + (r0 - weight*Rinf)*Exp1(-(t - t0)/Rtau) t0 = t synon = synon - weight Ron = Ron - r0 Roff = Roff + r0 on = 0 } } } FUNCTION Exp1(x) { if (x < -100) { Exp1 = 0 } else if (x > 100) { Exp1 = exp(100) } else{ Exp1 = exp(x) } }