/*---------------------------------------------------------------------------- VOLTAGE-CLAMP SIMULATIONS OF RE CELLS ===================================== - passive and structural parameters estimated from SimFit - electrode with adjustable series resistance - simulations at 24 degC - special run procedure for calculating the peak current - calcium diffusion - Q10=2.5 ** voltage-clamp in dissociated RE cell with 8 compartment ** For more details, see: Destexhe, A., Contreras, D., Steriade, M., Sejnowski, T.J. and Huguenard, J.R. In vivo, in vitro and computational analysis of dendritic calcium currents in thalamic reticular neurons. J. Neurosci. 16: 169-185, 1996. See also: http://www.cnl.salk.edu/~alain http://cns.fmed.ulaval.ca ----------------------------------------------------------------------------*/ //---------------------------------------------------------------------------- // load and define general graphical procedures //---------------------------------------------------------------------------- // xopen("$(NEURONHOME)/lib/hoc/stdrun.hoc") load_file("nrngui.hoc") objectvar g[20] // max 20 graphs ngraph = 0 proc addgraph() { local ii // define subroutine to add a new graph // addgraph("variable", minvalue, maxvalue) ngraph = ngraph+1 ii = ngraph-1 g[ii] = new Graph() g[ii].size(tstart,tstop,$2,$3) g[ii].xaxis() g[ii].yaxis() g[ii].addvar($s1,1,0) g[ii].save_name("graphList[0].") g[ii].exec_menu("Keep Lines") graphList[0].append(g[ii]) } if(ismenu==0) { nrnmainmenu() // create main menu nrncontrolmenu() // create control menu } //---------------------------------------------------------------------------- // transient time //---------------------------------------------------------------------------- trans = 1000 print " " print ">> Transient time of ",trans," ms" print " " //---------------------------------------------------------------------------- // create multi-compartment geometry and insert currents //---------------------------------------------------------------------------- xopen("cells/reD.geo") // read geometry file corrD = 1 // dendritic surface correction forall { // insert passive current everywhere insert pas g_pas = 5e-5 * corrD // (from simfit) e_pas = -72.843 // (from simfit) cm = 1 * corrD // (from simfit) Ra = 260 // (from simfit) L = L } soma { g_pas = 5e-5 // (from simfit) cm = 1 // (from simfit) } forall { insert it2 // T-current everywhere cai = 2.4e-4 cao = 2 eca = 120 shift_it2 = 0 // no shift of ITs gcabar_it2 = corrD * 0.0002 qm_it2 = 2.5 // low q10 qh_it2 = 2.5 insert cad // calcium diffusion everywhere depth_cad = corrD // NEED TO BE RESCALED kt_cad = 0 // no pump kd_cad = 1e-4 taur_cad = 5 cainf_cad = 2.4e-4 } xopen("locD.oc") // load procedure for localizing T-current localize (0.000045, 0.000045) // initial distribution of T-current //---------------------------------------------------------------------------- // insert electrode in the soma //---------------------------------------------------------------------------- // note load_file command only executed if not executed yet for that file in current session load_file("El.oc") // Electrode with series resistance access soma objectvar El // insert electrode El = new Electrode() electrodes_present=1 // // VOLTAGE-CLAMP MODE // forall { g_pas = 0 } // remove passive current everywhere soma El.vc.loc(0.5) // put electrode in voltage-clamp mode El.vc.dur[0] = trans-20 El.vc.dur[1] = 10 El.vc.dur[2] = 1000 El.vc.amp[0] = -110 El.vc.amp[1] = -110 El.vc.amp[2] = -30 El.vc.rs = 5 // series resistance // 49.79 megohm from simfit //---------------------------------------------------------------------------- // setup simulation parameters //---------------------------------------------------------------------------- Dt = 0.2 npoints = 2000 objectvar Sim // create vector of simulation points Sim = new Vector(npoints) dt = 0.1 // must be submultiple of Dt tstart = trans-100 tstop = trans + npoints * Dt runStopAt = tstop steps_per_ms = 1/Dt celsius = 24 v_init = -70 //---------------------------------------------------------------------------- // procedures for voltage-clamp protocol //---------------------------------------------------------------------------- proc run2() { // new run procedure run() peak_current = Sim.min() print "Peak current = ",peak_current } proc init() { // initialization procedure finitialize(v_init) fcurrent() index = 0 // add definition of an index peak_current = 0 // define peak current } proc step() {local i // advance-one-step (Dt) procedure Plot() if(t >= trans) { Sim.set(index,El.vc.i) // memorize data only after trans index = index + 1 } for i=1,nstep_steprun { advance() } } vmin = -110 // values of protocol vmax = -40 vstep = 5 proc run_vc() { // general procedure for v-clamp for(vhold=vmin; vhold<vmax+vstep; vhold=vhold+vstep) { El.vc.amp[0] = vhold run2() } } proc make_VCpanel() { // make panel xpanel("VC") xpvalue("Start holding potential",&vmin) xpvalue("End holding potential",&vmax) xpvalue("Step potential",&vstep) xbutton("Start protocol","run_vc()") xpanel() } make_VCpanel() //---------------------------------------------------------------------------- // add graphs //---------------------------------------------------------------------------- addgraph("El.vc.i",-0.16,0.0001) addgraph("soma.v(0.5)",-120,0) addgraph("dend1[3].v(0.5)",-120,0) // for dissociated cell //addgraph("dend3[6].v(0.5)",-120,0) // for intact cell