TITLE AMPA and NMDA receptor with presynaptic shortterm plasticity
COMMENT
AMPA and NMDA receptor conductance using a dualexponential profile
Based on Jahr and Stevens 1990 equations
ENDCOMMENT
NEURON {
POINT_PROCESS NMDA
RANGE tau_r_NMDA, tau_d_NMDA,n_NMDA,gama_NMDA
RANGE Use
RANGE i, i_NMDA, g_NMDA, e, gmax
NONSPECIFIC_CURRENT i
}
PARAMETER {
n_NMDA = 0.28011 (/mM)
gama_NMDA = 0.062 (/mV)
tau_r_NMDA = 0.3 (ms) : dualexponential conductance profile
tau_d_NMDA = 43 (ms) : IMPORTANT: tau_r < tau_d
Use = 1.0 (1) : Utilization of synaptic efficacy (just initial values! Use, Dep and Fac are overwritten by BlueBuilder assigned values)
e = 0 (mV) : AMPA and NMDA reversal potential
mg = 1 (mM) : initial concentration of mg2+
mggate
:gmax = .001 (uS) :1nS weight conversion factor (from nS to uS)
u0 = 0 :initial value of u, which is the running value of Use
}
COMMENT
The Verbatim block is needed to generate random nos. from a uniform distribution between 0 and 1
for comparison with Pr to decide whether to activate the synapse or not
ENDCOMMENT
ASSIGNED {
v (mV)
i (nA)
i_NMDA (nA)
g_NMDA (uS)
factor_NMDA
}
STATE {
A_NMDA : NMDA state variable to construct the dualexponential profile  decays with conductance tau_r_NMDA
B_NMDA : NMDA state variable to construct the dualexponential profile  decays with conductance tau_d_NMDA
}
INITIAL{
LOCAL tp_NMDA
A_NMDA = 0
B_NMDA = 0
tp_NMDA = (tau_r_NMDA*tau_d_NMDA)/(tau_d_NMDAtau_r_NMDA)*log(tau_d_NMDA/tau_r_NMDA) :time to peak of the conductance
factor_NMDA = exp(tp_NMDA/tau_r_NMDA)+exp(tp_NMDA/tau_d_NMDA) :NMDA Normalization factor  so that when t = tp_NMDA, gsyn = gpeak
factor_NMDA = 1/factor_NMDA
}
BREAKPOINT {
SOLVE state METHOD cnexp
mggate = 1 / (1 + exp(gama_NMDA * (v)) * (n_NMDA)) :mggate kinetics  Jahr & Stevens 1990
g_NMDA = (B_NMDAA_NMDA) * mggate :compute time varying conductance as the difference of state variables B_NMDA and A_NMDA and mggate kinetics
i_NMDA = g_NMDA*(ve) :compute the NMDA driving force based on the time varying conductance, membrane potential, and NMDA reversal
i = i_NMDA
}
DERIVATIVE state{
A_NMDA' = A_NMDA/tau_r_NMDA
B_NMDA' = B_NMDA/tau_d_NMDA
}
NET_RECEIVE (weight, weight_NMDA){
weight_NMDA = weight
A_NMDA = A_NMDA + weight_NMDA*factor_NMDA
B_NMDA = B_NMDA + weight_NMDA*factor_NMDA
}
