COMMENT AMPA channel This is an adapted version of Exp2Syn. Adapted by Kevin M Biddell similar to as described by wolf et al 2006 4/21/07 verified 3/29/2012 kevin.biddell@gmail.com Two state kinetic scheme synapse described by rise time tauon, and decay time constant tauoff. The normalized peak condunductance is 1. Decay time MUST be greater than rise time. The solution of A->G->bath with rate constants 1/tauon and 1/tauoff is A = a*exp(-t/tauon) and G = a*tau2/(tauoff-tauon)*(-exp(-t/tauon) + exp(-t/tauoff)) where tauon < tauoff If tauoff-tauon -> 0 then we have a alphasynapse. and if tauon -> 0 then we have just single exponential decay. The factor is evaluated in the initial block such that an event of weight 1 generates a peak conductance of 1. Because the solution is a sum of exponentials, the coupled equations can be solved as a pair of independent equations by the more efficient cnexp method. ENDCOMMENT NEURON { POINT_PROCESS AMPAk RANGE tauon, tauoff, gAmax, gA, Erev, i NONSPECIFIC_CURRENT i GLOBAL total } UNITS { (nA) = (nanoamp) (mV) = (millivolt) (uS) = (microsiemens) (pS) = (picosiemens) } PARAMETER { Erev = 0 (mV) : reversal potential gAmax = 30 (pS) : maximal conductance fit ~5/07 by KMB tauon = 1.1 (ms)<1e-9,1e9> tauoff = 5.75 (ms)<1e-9,1e9> } ASSIGNED { v (mV) i (nA) gA (uS) factor total (uS) } STATE { m (uS) h (uS) } INITIAL { LOCAL tp total = 0 if (tauon/tauoff > .9999) { tauon = .9999*tauoff } m = 0 h = 0 tp = (tauon*tauoff)/(tauoff - tauon) * log(tauoff/tauon) factor = -exp(-tp/tauon) + exp(-tp/tauoff) factor = 1/factor } BREAKPOINT { SOLVE state METHOD cnexp gA = (1e-6)*gAmax*(h-m) : the 1e-6 is to convert pS to microSiemens i = gA*(v - Erev) } DERIVATIVE state { m' = -m/tauon h' = -h/tauoff } NET_RECEIVE(weight (uS)) { state_discontinuity(m, m + weight*factor) state_discontinuity(h, h + weight*factor) total = total+weight }