Neocort. pyramidal cells subthreshold somatic voltage controls spike propagation (Munro Kopell 2012)

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Accession:136309
There is suggestive evidence that pyramidal cell axons in neocortex may be coupled by gap junctions into an ``axonal plexus" capable of generating Very Fast Oscillations (VFOs) with frequencies exceeding 80 Hz. It is not obvious, however, how a pyramidal cell in such a network could control its output when action potentials are free to propagate from the axons of other pyramidal cells into its own axon. We address this problem by means of simulations based on 3D reconstructions of pyramidal cells from rat somatosensory cortex. We show that somatic depolarization enables propagation via gap junctions into the initial segment and main axon, while somatic hyperpolarization disables it. We show further that somatic voltage cannot effectively control action potential propagation through gap junctions on minor collaterals; action potentials may therefore propagate freely from such collaterals regardless of somatic voltage. In previous work, VFOs are all but abolished during the hyperpolarization phase of slow-oscillations induced by anesthesia in vivo. This finding constrains the density of gap junctions on collaterals in our model and suggests that axonal sprouting due to cortical lesions may result in abnormally high gap junction density on collaterals, leading in turn to excessive VFO activity and hence to epilepsy via kindling.
Reference:
1 . Munro E, Kopell N (2012) Subthreshold somatic voltage in neocortical pyramidal cells can control whether spikes propagate from the axonal plexus to axon terminals: a model study. J Neurophysiol 107:2833-52 [PubMed]
Model Information (Click on a link to find other models with that property)
Model Type: Realistic Network; Neuron or other electrically excitable cell; Axon;
Brain Region(s)/Organism: Neocortex;
Cell Type(s): Neocortex L5/6 pyramidal GLU cell; Neocortex U1 L2/6 pyramidal intratelencephalic GLU cell;
Channel(s): I Na,t; I K; I Sodium; I Potassium;
Gap Junctions: Gap junctions;
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON; MATLAB;
Model Concept(s): Oscillations; Detailed Neuronal Models; Axonal Action Potentials; Epilepsy;
Implementer(s): Munro, Erin [ecmun at math.bu.edu];
Search NeuronDB for information about:  Neocortex L5/6 pyramidal GLU cell; Neocortex U1 L2/6 pyramidal intratelencephalic GLU cell; I Na,t; I K; I Sodium; I Potassium;
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Munro_Kopell_corticalcontrol
NEURON
cell_geoms
run_files
readme.txt
extrema.mod
gap.mod
k2_Traub.mod *
ka_Traub.mod *
kdr_Jonas.mod
kdr_Traub.mod
kdr_Yu.mod
naf_Jonas.mod
naf_Traub.mod
naf_Yu.mod
pas_basket.mod
pas_chand.mod
030625DS2.hoc
axon_templates.hoc
C040896A-P3.hoc
C040896A-P3axgeom.hoc
C230797B-P4.hoc
C270999B-P2axgeom.hoc
C280199C-P1.hoc
C290500C-P1axgeom.hoc
cell_templates.hoc
expcell_templates.hoc
gap_junction.hoc
gj_propagation_test.ses
junction_stats.hoc
kinetics.hoc
kinetics_wholecell.hoc
mosinit.hoc
propagation_test.ses
PropagationSearch.hoc
simulation_base.hoc
vs-arg_cutoff.hoc
vs-arg_cutoff_Jonas.hoc
vs-expcell_gj.hoc
vs-expcell_gj_gL.hoc
vs-expcell_gj_Jonas.hoc
vs-expcell_gjCC.hoc
vs-expcell_gjISgNa.hoc
vs-expcell_gjsISgNa.hoc
vs-generic_cutoff.hoc
vs-generic_cutoff_Jonas.hoc
                            
proc insertwhole_Traub(){
    forall {
        insert pas
        e_pas = -70
        cm = 0.9
    }
    forsec "axon" {
        g_pas = 1/1000
        Ra =   100.0
        insert nafTraub
        ena = 50
        gbar_nafTraub =   0.45
        insert kdrTraub
        ek = -95
        gbar_kdrTraub =   0.45
    }
    forsec "soma" {
        g_pas = 1/50000
        Ra = 250
    }
    forsec "dendrite" {
        g_pas = 1/50000
        Ra = 250
    }
    tstop = 20
}

proc uninsertwhole_Traub(){
    forall {
        uninsert pas
        uninsert nafTraub
        uninsert kdrTraub
    }
}

proc insertwhole_modTraub(){local needISchild localobj sref
    forall {
        insert pas
        e_pas = -70
        cm = 0.9
    }
    forsec "axon" {
        g_pas = 1/1000
        Ra =   100.0
        insert nafTraub
        gbar_nafTraub =   0.2
        ena = 50
        insert kdrTraub
        gbar_kdrTraub =   0.2
        ek = -95
    }
    this.axon[IS]{
	      needISchild=1
        for(x){
            if(x*L<40){
                gbar_nafTraub(x) =   0.45
                gbar_kdrTraub(x) =   0.45
            }else{
		            needISchild=0
	          }
        }
	      if(needISchild){
	          print "need to insert higher g_Na into IS child"
	      }
        insert pasChand
    }
    if(needISchild){
	      axon[ISchild]{
	          for(x){
		            if(this.axon[IS].L + x*L<40){
		                gbar_nafTraub(x) = 0.45
		                gbar_kdrTraub(x) = 0.45
		            }
	          }
	      }
        insert pasChand
    }
    forsec "soma" {
        g_pas = 2e-3 // higher conductance makes up for currents not being modeled
        //1/50000
        Ra = 250
        /*insert nafTraub
        gbar_nafTraub = 0.2
        insert kdrTraub
        gbar_kdrTraub = 0.2*/
    }
    forsec "dendrite" {
        g_pas = 1/50000
        Ra = 250
    }
    soma{
        insert pasBasket
        sref = new SectionRef()
    }
    for(i=0;i<=sref.nchild-1;i=i+1){
        sref.child[i]{
            insert pasBasket
        }
    }
    tstop = 20
}

proc resetwhole_modTraub(){local needISchild,gna,ISgna
    // call after insert_modTraub to adjust g_na in axons
    gna = $1
    
    if(numarg()>1){
        ISgna = $2
    }else{
        ISgna = 0.45
    }
    
    forsec "axon" {
        gbar_nafTraub = gna
        gbar_kdrTraub = gna
    }
    axon[IS]{
        needISChild = 1
        for(x){
            if(x*L<40){
                gbar_nafTraub(x) = ISgna
                gbar_kdrTraub(x) = ISgna
            }else{
                needISchild = 0
            }
        }
    }
    print "needISchild = ", needISchild
    if(needISchild){
	      axon[ISchild]{
	          for(x){
		            if(axon[IS].L + x*L<40){
		                gbar_nafTraub(x) = ISgna
		                gbar_kdrTraub(x) = ISgna
		            }
	          }
	      }
    }    
}

proc insertwhole_Jonas(){local needISchild localobj sref
    forall {
	      insert pas
	      g_pas =   1/36000
	      e_pas = -85
	      Ra =   163
	      cm = 1
    }
    forsec "axon" {
	      insert nafJonas
	      ena = 60
	      insert kdrJonas
	      ek = -85
        
	      gbar_nafJonas =   0.03
	      gbar_kdrJonas =  0.03
    }
    this.axon[IS]{
	      needISchild=1
        for(x){
            if(x*L<40){
                gbar_nafJonas(x) =   0.096
                gbar_kdrJonas(x) =   0.096
            }else{
		            needISchild=0
	          }
        }
	      if(needISchild){
	          print "need to insert higher g_Na into IS child"
	      }
        insert pasChand
    }
    if(needISchild){
	      axon[ISchild]{
	          for(x){
		            if(this.axon[IS].L + x*L<40){
		                gbar_nafTraub(x) = 0.096
		                gbar_kdrTraub(x) = 0.096
		            }
	          }
	      }
        insert pasChand
    }
    /*forsec "soma" {
	      gbar_nafJonas =   0.027
	      gbar_kdrJonas =  0.027
    }
    forsec "dendrite" {
	      gbar_nafJonas =   0.027
	      gbar_kdrJonas =  0.027
    }*/
    soma{
        insert pasBasket
        sref = new SectionRef()
    }
    for(i=0;i<=sref.nchild-1;i=i+1){
        sref.child[i]{
            insert pasBasket
        }
    }
    tstop = 70
    print "tstop = ", tstop
}

proc uninsertwhole_Jonas(){
  forall {
    uninsert pas
    uninsert nafJonas
    uninsert kdrJonas
  }
}

proc resetwhole_Jonas(){local needISchild,gna,ISgna
    // call after insert_modTraub to adjust g_na in axons
    gna = $1
    
    if(numarg()>1){
        ISgna = $2
    }else{
        ISgna = 0.096
    }
    
    forsec "axon" {
        gbar_nafJonas = gna
        gbar_kdrJonas = gna
    }
    axon[IS]{
        needISChild = 1
        for(x){
            if(x*L<40){
                gbar_nafJonas(x) = ISgna
                gbar_kdrJonas(x) = ISgna
            }else{
                needISchild = 0
            }
        }
    }
    print "needISchild = ", needISchild
    if(needISchild){
	      axon[ISchild]{
	          for(x){
		            if(axon[IS].L + x*L<40){
		                gbar_nafJonas(x) = ISgna
		                gbar_kdrJonas(x) = ISgna
		            }
	          }
	      }
    }    
}


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