Dendro-dendritic synaptic circuit (Shepherd Brayton 1979)

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A NEURON simulation has been created to model the passive spread of an EPSP from a mitral cell synapse on a granule cell spine. The EPSP was shown to propagate subthreshold through the dendritic shaft into an adjacent spine with significant amplitude (figure 2B).
1 . Shepherd GM, Brayton RK (1979) Computer simulation of a dendrodendritic synaptic circuit for self- and lateral-inhibition in the olfactory bulb. Brain Res 175:377-82 [PubMed]
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Model Information (Click on a link to find other models with that property)
Model Type: Dendrite;
Brain Region(s)/Organism:
Cell Type(s):
Gap Junctions:
Simulation Environment: NEURON;
Model Concept(s): Influence of Dendritic Geometry; Olfaction;
Implementer(s): Morse, Tom [Tom.Morse at];
begintemplate Spine
  public neck, head, ps, syntimes
  // neck and head are the NEURON sections of the spine
  // ps: a psection (print section) proc that prints
  // the spine head, neck, and neck's parent mechanisms
  // with the psection() command in those accessed sections.
  // syntimes: is a proc that sets time of activation of
  // of ampa and nmda point processes
  public Ra, Rm, C, g_pas
  // passive properties
  // note that g_pas is set to 1/Rm

  public insert_Grunditz
  // insert_Grunditz sets active conductances to same as Grunditz 2008

  public syntimes, set_syntimes, clear_syntimes
  // a vector of synaptic stimulation times, and two methods to add and clear

  public nc1, nc2
  // made public to make it easier to send events.

  external spine_list, spinehead_list, spineneck_list  // SectionList's of head' and neck's, and just heads, and just necks
  objref nc1, nil, nc2, fih
  objref synAmpa, synNmda, syntimes, loadqueue
  objref fih
  objref secref
  create neck, head

// init creates the morphology of the spine
  proc init() {

    if ((numarg()==6) || (numarg()==2)) {
    create neck, head
    neck { spine_list.append() spineneck_list.append() }
    head { spine_list.append() spinehead_list.append() }
    neck {L=0.43 diam=0.2 } // default to Harris et al. 1992 table 4, mushroom
    head {L=1.07 diam=0.61}
    if (numarg()==6) {
     neck {L=$3 diam=$4 }
     head {L=$5 diam=$6}
    } else if (numarg()!=2) {
     print "Error: number of arguments to Spine init() was ",numarg()," and should have been 2 or 6"
     print "Usage:"
     print "create dend // a dendrite process (shaft, cylinder, frustrum, etc.)"
     print "objref tmpSectionRef"
     print "dend tmpSectionRef=new SectionRef()"
     print "objref spineref"
     print "spineref=new Spine(tmpSectionRef, x_dend_location, neck_length=.43, neck_diameter=.2, \ "
     print "head_length=1.07, head_diam=0.61)"
     print "// if 2 arguments passed then mushroom spine dimensions from Harris et al. 1992 table 4 params"
     print "// Above variables listed with their default values"
     print "// - in actuality just pass numbers, not variables and equal signs!"
    secref.sec connect neck(0),$2
    neck connect head(0), 1
    // neck.diam=0.0394  // note this is overriding the default of 0.2 from Harris
                      // and may be overwritten if a neck diameter is passed for
                      // the initialization of this object.    

    // insert_excitatory()
proc insert_excitatory() {
    // copied from fig4.hoc accession num 116769 Grunditz et al. 2008
    start point of AMPA and NMDA                   
    objref synAmpa  
    head synAmpa = new ampa(0.5)  
    objref nc1, nil  
    nc1 = new NetCon(nil, synAmpa)  
    nc1.weight = 240
    nc1.delay = 0

    objref synNmda  
    head synNmda = new nmda (0.5)  
    objref nc2, nil  
    nc2 = new NetCon(nil, synNmda)  
    nc2.weight = 110
    nc2.delay = 0

    objref syntimes  
    syntimes = new Vector(1)  
    syntimes.x[0] = 3.2 // tmm changed from 20

proc set_passive_prop() {

    // copied from iniparameter.hoc modeldb accession num 116769
    // Grunditz et al. 2008
    initialize basic parameters                    
// not used:    celsius = 30        /* temperature */
// not used:    v_init=-65
    global_ra=150.00 	/* internal resistivity in ohm-cm */
    Cm=0.75             /* specific membrane capacitance in uF/cm^2 */
    Rm=40000            /* specific membrane resistivity in ohm-cm^2 */ 
    Vleak=-65           /* leak reversal -65mV */
// not used:    Vrest=-65           /* resting potential -64.6 mV*/
// not used:    spinelimit=100      /* distance beyond which to modify for spines */
    spinefactor=2.0     /* factor by which to change passive properties */
    // sometimes a spinefactor is used to increase the effective
    // membrane for the case where spines are not explicitly
    // represented.  Here, as in Grunditz, spinefactor increases the
    // effective membrane area (by being multiplied into the
    // conductances and capacitance) in addition to the spine being
    // explicitly represented.

// not used:    isegfactor=100
// not used:    isegfrac=0.8

procedure to insert and initialize channels    
    forall {insert pas  g_pas=1/(Rm)  Ra=global_ra  e_pas=Vleak 
    head {
      insert pas e_pas=Vleak  g_pas=spinefactor/Rm  Ra=global_ra  cm=spinefactor*Cm
    neck {
      insert pas e_pas=Vleak  g_pas=spinefactor/Rm  Ra=global_ra  cm=spinefactor*Cm 

proc insert_Grunditz() {
  // Grunditz et al. 2005 conductances are inserted into the spine
    head {
      insert car
      insert cadiffus
      insert canmda
    neck {
      insert cadiffus
    // add cadiffus to parent dendrite if not already included:
    // $o1.sec { if (ismembrane("cacum")) {
    //              uninsert cacum
    //           }
    //           if (!ismembrane("cadiffus")) {
    // 	         insert cadiffus
    //           }

proc set_syntimes() {

proc clear_syntimes() {

fih = new FInitializeHandler("loadqueue()")
proc loadqueue() { local ii
  for ii=0,syntimes.size()-1 {
  proc ps() {
    print "*** The spine sections:"
    neck psection()
    head psection()
    print "*** has parent section:"
    secref.sec psection()
endtemplate Spine