// Maurice Petroccine, SUNY Albany (mpetroccione@albany.edu)
// Last updated on 11/19/2021
// This code applies a single (AMPA) input to the dendrite of a ball and stick model and records the peak amplitude and t50 of the EPSC recorded from the soma.
// A simulation is run for each segment of the dendrite while systematically varying the weight and tau of the AMPA input.
// Time step: 0.025 ms
// Window duration: 400 ms
// to run type go("FileNameGoesHere") where you substitute what you want to name the file for FileNameGoesHere
// File will appear in the same folder as the hoc file after it is done (make sure simulation is finished before opening)
// Necessary files needed to run:
load_file ("nrngui.hoc")
model_type = 1 // choose whether the model should be WT (1) or KO (2)
num_g_step = 20 // the number of steps over which the input weight will be incremented
num_d_step = 50 // the number of steps over which to move the input along the dendrite (= to nseg)
wAMPA = 0.1 // the initial weight of the AMPA input
dt = 0.025 // time step of simulation
strdef preface, dirstr
preface = "."
sprint(dirstr, "%s/all_tau_vecs.hoc", preface) // opens all_tau_vecs.hoc
xopen(dirstr)
/***** TOPOLOGY *****/
create soma, dend // creates soma and a dendrite
connect dend(0), soma(1)
access dend // sets access to the dendrite
soma {
L = 15 // um, length of the soma
diam = 15 // um, diameter of the soma
nseg = 1
}
dend {
L = xxx // um, length of the dendrite
diam = 1.75 // um, starting diameter of the dendrite
nseg = 51 // # of segments
diam(0:1) = 1.75:0.5 // tapers the diameter from 1.75 um at the at soma to 0.5 um at the tip
}
/***** BIOPHYSICS *****/
forall {
Ra = 100 // MOhm, axial resistance
cm = 1 // uF/cm2
}
soma { // inserts conductances in the soma
insert caL // experimental data obtained using Cs+ based internal solution, therefore all K+ conductances were removed
insert caL13
pcaLbar_caL13 = 4.25e-7
insert car
insert cat
insert naf
gnabar_naf = 0.16 // sodium conductances
hshift_naf = 0
insert nap
gnabar_nap = 0.0005
insert caldyn // inserts calcium dynamics in the soma
insert cadyn
celsius = 23 // experimental data obtained at room temperature
}
dend { // inserts conductances in the dendrite - see soma for more info
insert naf
gnabar_naf = 0.0195
insert nap
gnabar_nap = 1.38e-7
insert caL
insert caL13
pcaLbar_caL13 = 4.25e-7
insert car
insert cat
insert caldyn
insert cadyn
ena = 60
}
celsius = 23 // recordings took place at room temperature
cao = 1.2 // mM,
ena = 60 // mV, sodium reversal potential
v_init = -70 // mV, initial voltage
cai0_ca_ion = 0.001 // mM, modifided, [Ca2+] in external solution
cao0_ca_ion = 1.2 // mM, Churchill 1998
cali0_cal_ion = 0.001 // mM, Churchill 1998
calo0_cal_ion = 1.2 // mM, modifided, [Ca2+] in external solution
CAINF = 1e-5 // mM, steady state intracell ca conc.
TAUR = 43 // ms, time const of ca diffusion - Jackson 2003
CA_DRIVE = 10000
CA_PUMP = 0.02
proc set_cainf() { NEW_CAINF = $1 //Ca2+ concentrations and dynamics, from Mattioni
nCA_INF = NEW_CAINF
forall if (ismembrane("cadyn")) {cainf_cadyn = NEW_CAINF}
forall if (ismembrane("caldyn")) {cainf_caldyn = NEW_CAINF}
}
proc set_taur() { NEW_TAUR = $1
nCA_TAUR = NEW_TAUR
forall if (ismembrane("cadyn")) {taur_cadyn = NEW_TAUR}
forall if (ismembrane("caldyn")) {taur_caldyn = NEW_TAUR}
}
proc set_cadrive() { NEW_DRIVE = $1
nCA_DRIVE = NEW_DRIVE
forall if (ismembrane("cadyn")) {drive_cadyn = NEW_DRIVE}
forall if (ismembrane("caldyn")) {drive_caldyn = NEW_DRIVE}
}
proc set_pump() { NEW_PUMP = $1
nCA_PUMP = NEW_PUMP
forall if (ismembrane("cadyn")) {pump_cadyn = NEW_PUMP}
forall if (ismembrane("caldyn")) {pump_caldyn = NEW_PUMP}
}
// Instrumentation
objref voltage_clamp // define volatage clamp
soma voltage_clamp = new Voltage_Clamp(0.5) // place voltage clamp in the soma
{voltage_clamp.dur1 = 1000 // ms, clamp duration
voltage_clamp.amp1= -70 // mV, holding potential
voltage_clamp.rs= 0.001 // Mohm???, series resistance of voltage clamp
}
// Graphical display
objref g // create a new graph that displays the voltage at the soma
g = new Graph()
addplot(g,0)
g.exec_menu("Keep Lines")
g.size(0,50,-80,40)
g.addvar("soma.v(0.5)", 1, 1, 0.6, 0.9, 2)
g.addvar("dend.v(0.7)", 2, 1, 0.6, 0.9, 2)
g.addvar("dend.v(0.1)", 3, 1, 0.6, 0.9, 2)
objref g2 // creates a new graph that plots the holding current
g2 = new Graph()
addplot(g2,1)
g2.exec_menu("Keep Lines")
g2.size(0,1000,-80,40)
g2.addvar("voltage_clamp.i")
//g2.addexpr("c1.i")
//Sim control
objref recI // Creates vector object, records I at the soma
recI = new Vector()
recI.record(&voltage_clamp.i)
objref iMin, tMin, iChange, it50, t50 // creates vectors to track:
t50 = new Vector (101,0) // t50
it50 = new Vector (101,0) // holding current at the time of the t50
iMin = new Vector(101,0) // peak epsc amplitude (includes holding current)
tMin = new Vector(101,0) // the time of the epsc peak
iChange = new Vector(101,0) // the difference between the holding current and the peak epsc amplitude
objref diststep
diststep = new Vector(40000)
diststep.indgen(0,0.025)
objref distdrop // creates a new graph - later used to plot V vs Dist
distdrop = new Graph()
distdrop.size(0,200,-1,0) // SCALE OF GRAPH IS WRONG ****FIX******
distdrop.exec_menu("Keep Lines") // Look into plotting families of lines or vectors. Also how to label
objref test [num_g_step] // creates test
objref minI [num_g_step] // creates minI
objref tfil // creates a new file for storing the output data
tfil = new File()
strdef tmpstr
strdef gstepname
strdef taustepname
objref syn_ampa, syn_nmda, syn_ampa2, syn_nmda2, ns2, nc, nc3, nc4, nc2, ns
ns = new NetStim(0.5) // creates a netstim to trigger an input that starts at 10 ms
ns.interval = 1
ns.start = 10
ns.noise = 0
ns.number = 1
dend syn_ampa = new AMPA(0.1) // inserts a input (AMPA synapse) into the dendrite
nc3 = new NetCon(ns, syn_ampa) // a netcon linking the AMPA input to the netstim
nc3.weight = 2
nc3.delay = 0
objref avgI, tmp //
avgI = new Vector() // discard whatever is already in avg
tmp = new Vector()
proc initialize() { // Sets model to initial state (time, voltage)
t = 0
finitialize(v_init)
cai0_ca_ion = 0.001 // mM, Churchill 1998
cao0_ca_ion = 1.2 // mM, Churchill 1998 - gives eca = 100 mV
cali0_cal_ion = 0.001 // mM, Churchill 1998
calo0_cal_ion = 1.2
CAINF = 1e-5 // mM, steady state intracell ca conc.
TAUR = 43 // ms, time const of ca diffusion - Jackson 2003
CA_DRIVE = 10000
CA_PUMP = 0.02
fcurrent()
}
proc integrate() { // fadvance should be moving the sim forward,
//g.begin() // g.plot(t) updates the graph in real time
while (t<tstop) {
fadvance()
//g.plot(t)
g2.plot(t)
}
//g.flush()
g2.flush()
}
proc go() { // the run command - note: does not work without have the access set to the dendrite
sprint(tmpstr, "%s.dat", $s1) // creates a string for the output file name
tfil.wopen(tmpstr) // opens that file
for z = 0,(num_g_step-1) { // runs simulations for the num_g_steps
test[z] = new Vector()
minI[z] = new Vector()
tstop = 400+ z*10 // simulation stops after 400 ms (10 ms additionally added on per loop)
tau_d_AMPA = 35.5 * ((z*0.05)+0.05) // each loop tau for AMPA is incremented by 5% of it's initial value
nc3 = new NetCon(ns, syn_ampa)
nc3.weight = 0.1*wAMPA // 0.28 is WT, 0.235 for TBOA-WT, 0.2 for KO, Tau_d_AMPA is 35.5 for WT and 17 for KO
nc3.delay = 140 // sets delay for input to be 140 msec (to allow voltage clamp to stabilize at -70 mV)
changel() //
test[z].append(t50.x[z]) // appends t50 to test vector at position z
minI[z].append(iMin.x[z]) // append iMin to minI vector at position z
print z // This prints an update every 100 loops - comment out to run faster simulations
j = 0 // resets j
}
xytofile(test[w], tmpstr) // writes test vector to the output file
tfil.close() // closes the file.
}
proc changel() { // procedure for moving the stimulation point down the dendrite, input location is based on counter "j"
for i = 0,(num_d_step-1) { // NEURON doesn't accept point processes at location "1" - this for loop places the the input in the most distal segment if j=1
if (j>=1){
j=0.999
}
syn_ampa.loc(j+0.00001) // sets dendritic input location based on the loop
tmp.record(&voltage_clamp.i) // record the current applied by voltage_clamp to a temporary file (tmp)
initialize() // initialize the individual simulation
integrate() // run the individual simulation
j=j+(1/num_d_step) // moves the axon based on the number of distance steps
if (i==0) {
avgI.copy(tmp) // copy tmp to avg // when the first simulation is run copy tmp to avgI
}else {
avgI.add(tmp) // for subsequent runs add tmp to avgI element by element
}
if (i== num_d_step-1) {
avgI.div(num_d_step) // ####on the last set of simluations run for each distance-loop, divide to get the average current response
iMin.x[z] = avgI.x[5000] // ???
avgI.sub(iMin.x[z]) // subtract the holding current from the overall current injected by voltage_clamp
avgI.line(distdrop,diststep) // plots current-response to graph
iMin.x[z] = avgI.min(100,12000) // sets iMin for this loop to the peak current amplitude between point 100 and 12000
avgI.div(iMin.x[z]) // normalizes to peak
tMin.x[z] = avgI.max_ind() // makes note of data point where the peak occurs
avgI.remove(0,tMin.x[z]) // removes all points before the peak of the epsc
it50.x[z] = avgI.indwhere("<=", 0.5) // it50 for this loop is set to the first value where the the decays to 50% or less
t50.x[z] = it50.x[z]*0.025 // it50 is scaled by tstep to give the time in ms, which is recorded as the t50
avgI.resize(0) // resizes avgI to 0 to clear all values for next loop
}
}
}
proc xytofile() { local b //Procedure to write the t50 and peak amplitude of the epsc to two separate
w=0
print "writing to ", $s2 // notifies when writing to file
for w=0,num_g_step-1 { // writes the gstep and wAMPA at the beginning of the file
if (w==0){gsteplabel(wAMPA)
tfil.printf("\n%s\n", taustepname)
}
for b=0,$o1.size()-1
tfil.printf("%g\n", test[w].x[b])
}
for w=0,num_g_step-1 {
if (w==0){gsteplabel(wAMPA)
tfil.printf("\nAmplitude\n", taustepname) // prints the peak amplitude of the epsc to the file
for b=0,$o1.size()-1
}
tfil.printf("%g\n", minI[w].x[b])
}
}
proc gsteplabel (){ // writes the tau d in the first line of the file
sprint(taustepname, "The t50 for tau_d =\t%g", $1)
}