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142 lines
3.4 KiB
142 lines
3.4 KiB
TITLE NMDA receptor--one of the two input stimulation of our model |
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: This mechanism is taken from the Neuron data base "exp2syn.mod" |
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: The original comment are below between "COMMENT" and "ENDCOMMENT". |
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: |
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: Our modifications: |
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: 1.We added a single receptor conductance factor: "g_max=0.000045 (uS)". |
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: An event of weight 1 generates a peak conductance of 1*g_max. |
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: The weight is equal to the number of ampa receptors open at peak conductance |
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: |
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: 2.The NMDA receptors are simulated using a slow rise time constant |
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: and a double-expontial decay time constant |
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: The kinetic rate constants and channel conductance are taken from Franks KM, Bartol TM and Sejnowski TJ |
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: A Monte Carlo model reveals independent signaling at central glutamatergic synapses |
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: J Biophys (2002) 83(5):2333-48 |
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: and Spruston N, Jonas P and Sakmann B |
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: Dendritic glutamate receptor channels in rat hippocampal CA3 and CA1 neurons |
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: J Physiol (1995) 482(2): 325-352 |
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: correctd for physiological tempterature with Q10 from Hestrin S, Sah P and Nicoll RA |
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: Mechanisms generating the time course of dual component excitatory synaptic currents |
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: recorded in hippocampal slices |
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: Neuron (1990) 5: 247-253 |
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: |
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: Written by Lei Tian on 04/12/06 |
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COMMENT |
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Two state kinetic scheme synapse described by rise time tau1, |
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and decay time constant tau2. The normalized peak condunductance is 1. |
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Decay time MUST be greater than rise time. |
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The solution of A->G->bath with rate constants 1/tau1 and 1/tau2 is |
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A = a*exp(-t/tau1) and |
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G = a*tau2/(tau2-tau1)*(-exp(-t/tau1) + exp(-t/tau2)) |
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where tau1 < tau2 |
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If tau2-tau1 -> 0 then we have a alphasynapse. |
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and if tau1 -> 0 then we have just single exponential decay. |
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The factor is evaluated in the |
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initial block such that an event of weight 1 generates a |
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peak conductance of 1. |
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Because the solution is a sum of exponentials, the |
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coupled equations can be solved as a pair of independent equations |
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by the more efficient cnexp method. |
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ENDCOMMENT |
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NEURON { |
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THREADSAFE |
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POINT_PROCESS nmda |
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RANGE tau1, tau2, tau3, e, i, g_max, g, A, B, C ,k |
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NONSPECIFIC_CURRENT i |
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GLOBAL total,i2,g2 |
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: EXTERNAL Area_canmda |
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} |
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UNITS { |
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(nA) = (nanoamp) |
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(mA) = (milliamp) |
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(mV) = (millivolt) |
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(uS) = (microsiemens) |
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} |
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PARAMETER { |
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tau1 = 3.18 (ms) <1e-9,1e9> :rise time constant |
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tau2 = 57.14 (ms) <1e-9,1e9> :decay time constant |
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tau3 = 2000 (ms) <1e-9,1e9> :decay time constant |
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g_max= 0.000045 (uS) : single channel conductance |
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e = 0 (mV) |
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mg = 1 (mM) |
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Area (cm2) |
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k = 1e-06 (mA/nA) |
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Area_canmda = 1 |
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} |
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ASSIGNED { |
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v (mV) |
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i (nA) |
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factor |
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total (uS) |
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g (uS) |
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g2 (uS) : plot 'g' and 'i' in "nmda.mod". |
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i2 (mA/cm2) : global variables read in "canmda.mod" as 'inmda' and 'gnmda' to give us |
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} |
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STATE { |
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A (uS) |
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B (uS) |
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C (uS) |
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} |
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INITIAL { |
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LOCAL t_peak |
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total = 0 |
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if (tau1/tau2 > .9999) { |
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tau1 = .9999*tau2 |
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} |
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A = 0 |
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B = 0 |
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C = 0 |
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factor=0.8279 :from matlab to make the peak of the conductance curve shape to be 1*weight (then multiply with g_max) |
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factor = 1/factor |
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Area = Area_canmda |
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} |
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BREAKPOINT { |
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SOLVE state METHOD cnexp |
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g = g_max*(B*0.8+C*0.2-A) |
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i = g*(v - e)*1/(1+(exp(0.08(/mV) * -v)*(mg / 0.69))) |
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g2=g :global variable can be read in 'canmda.mod' |
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i2=i*k/Area :to get a current in 'mA/cm2' and send it to 'canmda.mod' |
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} |
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DERIVATIVE state { |
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A' = -A/tau1 |
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B' = -B/tau2 |
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C' = -C/tau3 |
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} |
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NET_RECEIVE(weight (uS)) { |
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state_discontinuity(A, weight*factor) |
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state_discontinuity(B, weight*factor) |
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state_discontinuity(C, weight*factor) |
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total = total+weight |
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} |
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