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Ribbon Synapse (Sikora et al 2005)

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A model of the ribbon synapse was developed to replicate both pre- and postsynaptic functions of this glutamatergic juncture. The presynaptic portion of the model is rich in anatomical and physiological detail and includes multiple release sites for each ribbon based on anatomical studies of presynaptic terminals, presynaptic voltage at the terminal, the activation of voltage-gated calcium channels and a calcium-dependent release mechanism whose rate varies as a function of the calcium concentration that is monitored at two different sites which control both an ultrafast, docked pool of vesicles and a release ready pool of tethered vesicles. See paper for more and details.
1 . Sikora MA, Gottesman J, Miller RF (2005) A computational model of the ribbon synapse. J Neurosci Methods 145:47-61 [PubMed]
Model Information (Click on a link to find other models with that property)
Model Type: Synapse;
Brain Region(s)/Organism:
Cell Type(s): Retina ganglion GLU cell; Retina bipolar GLU cell;
Channel(s): I L high threshold;
Gap Junctions:
Receptor(s): AMPA; NMDA;
Transmitter(s): Glutamate;
Simulation Environment: NEURON;
Model Concept(s): Intrinsic plasticity; Calcium dynamics;
Implementer(s): Sikora, Michael [Sikora at];
Search NeuronDB for information about:  Retina ganglion GLU cell; Retina bipolar GLU cell; AMPA; NMDA; I L high threshold; Glutamate;
// replace cad with cas in ganglion cell
load_proc ("nrnmainmenu")

create initseg, narrowr, axon,  preSyn, preSyn2

initseg { nseg = int(45/15) diam=1 L=45 }
narrowr { nseg = int(90/15) diam=0.4 L=90 }
axon{ nseg = int(1000/15) diam=1 L=1000 }

connect soma(1),initseg(0)
connect initseg(1),narrowr(0)
connect narrowr(1),axon(0)

insert cas
The [Ca++] is detected at two depths in the presynaptic bipolar cell.
This is implemented by two compartments which are identical
except for the depth at which the calcium shell is set.
objectvar bpclamp, bpclamp2
// Pre synaptic mechanisms (L channel and Voltage Clamp)
insert tsbp
uninsert cas
insert cad
depth_cad = 0.025
gcabar_tsbp =  0.0012
bpclamp = new VClamp(0.5)
insert tsbp
uninsert cas
insert cad
depth_cad = 0.05
gcabar_tsbp =  0.0012
bpclamp2 = new VClamp(0.5)

// Read the voltage file and play through the Voltage Clamps
objref f1, vec, vec2
f1 = new File()
vec = new Vector()
vec2 = new Vector()
vec2 = vec.c[0],0.025)[0],0.025)

forall{ // except the bipolar cells which are uninserted below
insert spike
// dendritic channel densities
gcabar_spike =  0.002
gkbar_spike =   0.012
gabar_spike =   0.036
gkcbar_spike =  0.000001
gnabar_spike =  0.025
insert spike
gcabar_spike =  0.0015
gkbar_spike =   0.018
gabar_spike =   0.054
gkcbar_spike =  0.000065
gnabar_spike =  0.10
initseg {
insert spike
gcabar_spike = 0.0015
gkbar_spike = 0.018
gabar_spike = 0.054
gkcbar_spike = 0.000065
gnabar_spike = 0.125 
narrowr {
insert spike
gcabar_spike = 0.0
gkbar_spike = 0.018
gabar_spike = 0.054
gkcbar_spike = 0.000065
gnabar_spike = 0.1
axon {
insert spike
gcabar_spike = 0.0
gkbar_spike = 0.018
gabar_spike = 0.0
gkcbar_spike = 0.000065
gnabar_spike = 0.07

mod_modulator = 0
insert pas
g_pas= 1/70000

access preSyn
uninsert spike
access preSyn2
uninsert spike

/* Synapses are positioned onto ganglion cell and connected presynaptically to bipolars
   Each synapse has at its disposal the presynaptic [Ca++] at two depths, but at any
   timestep only uses one in determining the rate constant.
objectvar synapse[23]
for i=0, 11{
access dend1[i]
synapse[i] = new ribbon_tiger(0.5)
setpointer synapse[i].preCA1,preSyn.cai(0.5)
setpointer synapse[i].preCA2,preSyn2.cai(0.5)
synapse[i].mg = 0.5
objectvar synapse2[23]
for i=0, 11{
access dend1[i]
synapse2[i] = new ribbon_tiger(0.5)
setpointer synapse2[i].preCA1,preSyn.cai(0.5)
setpointer synapse2[i].preCA2,preSyn2.cai(0.5)
synapse2[i].mg = 0.5

objectvar synapse3[23]
for i=0, 11{
access dend1[i]
synapse3[i] = new ribbon_tiger(0.5)
setpointer synapse3[i].preCA1,preSyn.cai(0.5)
setpointer synapse3[i].preCA2,preSyn2.cai(0.5)
synapse3[i].mg = 0.5

access dend1[19]
synapse[12] = new ribbon_tiger(0.5)
setpointer synapse[12].preCA1,preSyn.cai(0.5)
setpointer synapse[12].preCA2,preSyn2.cai(0.5)
access dend2[0]
synapse[13] = new ribbon_tiger(0.5)
setpointer synapse[13].preCA1,preSyn.cai(0.5)
setpointer synapse[13].preCA2,preSyn2.cai(0.5)
access dend2[1]
synapse[14] = new ribbon_tiger(0.5)
setpointer synapse[14].preCA1,preSyn.cai(0.5)
setpointer synapse[14].preCA2,preSyn2.cai(0.5)
access dend2[10]
synapse[15] = new ribbon_tiger(0.5)
setpointer synapse[15].preCA1,preSyn.cai(0.5)
setpointer synapse[15].preCA2,preSyn2.cai(0.5)
access dend3[0]
synapse[16] = new ribbon_tiger(0.5)
setpointer synapse[16].preCA1,preSyn.cai(0.5)
setpointer synapse[16].preCA2,preSyn2.cai(0.5)
access dend1[22]
synapse[17] = new ribbon_tiger(0.5)
setpointer synapse[17].preCA1,preSyn.cai(0.5)
setpointer synapse[17].preCA2,preSyn2.cai(0.5)
access dend4[0]
synapse[18] = new ribbon_tiger(0.5)
setpointer synapse[18].preCA1,preSyn.cai(0.5)
setpointer synapse[18].preCA2,preSyn2.cai(0.5)
access dend5[0]
synapse[19] = new ribbon_tiger(0.5)
setpointer synapse[19].preCA1,preSyn.cai(0.5)
setpointer synapse[19].preCA2,preSyn2.cai(0.5)
access dend6[0]
synapse[20] = new ribbon_tiger(0.5)
setpointer synapse[20].preCA1,preSyn.cai(0.5)
setpointer synapse[20].preCA2,preSyn2.cai(0.5)
access dend6[1]
synapse[21] = new ribbon_tiger(0.5)
setpointer synapse[21].preCA1,preSyn.cai(0.5)
setpointer synapse[21].preCA2,preSyn2.cai(0.5)
access dend6[2]
synapse[22] = new ribbon_tiger(0.5)
setpointer synapse[22].preCA1,preSyn.cai(0.5)
setpointer synapse[22].preCA2,preSyn2.cai(0.5)

access dend1[19]
synapse2[12] = new ribbon_tiger(0.5)
setpointer synapse2[12].preCA1,preSyn.cai(0.5)
setpointer synapse2[12].preCA2,preSyn2.cai(0.5)
access dend2[0]
synapse2[13] = new ribbon_tiger(0.5)
setpointer synapse2[13].preCA1,preSyn.cai(0.5)
setpointer synapse2[13].preCA2,preSyn2.cai(0.5)
access dend2[1]
synapse2[14] = new ribbon_tiger(0.5)
setpointer synapse2[14].preCA1,preSyn.cai(0.5)
setpointer synapse2[14].preCA2,preSyn2.cai(0.5)
access dend2[10]
synapse2[15] = new ribbon_tiger(0.5)
setpointer synapse2[15].preCA1,preSyn.cai(0.5)
setpointer synapse2[15].preCA2,preSyn2.cai(0.5)
access dend3[0]
synapse2[16] = new ribbon_tiger(0.5)
setpointer synapse2[16].preCA1,preSyn.cai(0.5)
setpointer synapse2[16].preCA2,preSyn2.cai(0.5)
access dend1[22]
synapse2[17] = new ribbon_tiger(0.5)
setpointer synapse2[17].preCA1,preSyn.cai(0.5)
setpointer synapse2[17].preCA2,preSyn2.cai(0.5)
access dend4[0]
synapse2[18] = new ribbon_tiger(0.5)
setpointer synapse2[18].preCA1,preSyn.cai(0.5)
setpointer synapse2[18].preCA2,preSyn2.cai(0.5)
access dend5[0]
synapse2[19] = new ribbon_tiger(0.5)
setpointer synapse2[19].preCA1,preSyn.cai(0.5)
setpointer synapse2[19].preCA2,preSyn2.cai(0.5)
access dend6[0]
synapse2[20] = new ribbon_tiger(0.5)
setpointer synapse2[20].preCA1,preSyn.cai(0.5)
setpointer synapse2[20].preCA2,preSyn2.cai(0.5)
access dend6[1]
synapse2[21] = new ribbon_tiger(0.5)
setpointer synapse2[21].preCA1,preSyn.cai(0.5)
setpointer synapse2[21].preCA2,preSyn2.cai(0.5)
access dend6[2]
synapse2[22] = new ribbon_tiger(0.5)
setpointer synapse2[22].preCA1,preSyn.cai(0.5)
setpointer synapse2[22].preCA2,preSyn2.cai(0.5)

access dend1[19]
synapse3[12] = new ribbon_tiger(0.5)
setpointer synapse3[12].preCA1,preSyn.cai(0.5)
setpointer synapse3[12].preCA2,preSyn2.cai(0.5)
access dend2[0]
synapse3[13] = new ribbon_tiger(0.5)
setpointer synapse3[13].preCA1,preSyn.cai(0.5)
setpointer synapse3[13].preCA2,preSyn2.cai(0.5)
access dend2[1]
synapse3[14] = new ribbon_tiger(0.5)
setpointer synapse3[14].preCA1,preSyn.cai(0.5)
setpointer synapse3[14].preCA2,preSyn2.cai(0.5)
access dend2[10]
synapse3[15] = new ribbon_tiger(0.5)
setpointer synapse3[15].preCA1,preSyn.cai(0.5)
setpointer synapse3[15].preCA2,preSyn2.cai(0.5)
access dend3[0]
synapse3[16] = new ribbon_tiger(0.5)
setpointer synapse3[16].preCA1,preSyn.cai(0.5)
setpointer synapse3[16].preCA2,preSyn2.cai(0.5)
access dend1[22]
synapse3[17] = new ribbon_tiger(0.5)
setpointer synapse3[17].preCA1,preSyn.cai(0.5)
setpointer synapse3[17].preCA2,preSyn2.cai(0.5)
access dend4[0]
synapse3[18] = new ribbon_tiger(0.5)
setpointer synapse3[18].preCA1,preSyn.cai(0.5)
setpointer synapse3[18].preCA2,preSyn2.cai(0.5)
access dend5[0]
synapse3[19] = new ribbon_tiger(0.5)
setpointer synapse3[19].preCA1,preSyn.cai(0.5)
setpointer synapse3[19].preCA2,preSyn2.cai(0.5)
access dend6[0]
synapse3[20] = new ribbon_tiger(0.5)
setpointer synapse3[20].preCA1,preSyn.cai(0.5)
setpointer synapse3[20].preCA2,preSyn2.cai(0.5)
access dend6[1]
synapse3[21] = new ribbon_tiger(0.5)
setpointer synapse3[21].preCA1,preSyn.cai(0.5)
setpointer synapse3[21].preCA2,preSyn2.cai(0.5)
access dend6[2]
synapse3[22] = new ribbon_tiger(0.5)
setpointer synapse3[22].preCA1,preSyn.cai(0.5)
setpointer synapse3[22].preCA2,preSyn2.cai(0.5)

GMAX = 0.00256
GMAXN = 0.00011

proc set_stim(){ // Used by the control panel defined below
for i = 0, 22 {
synapse[i].gmax = GMAX
synapse[i].gmaxN = GMAXN
synapse[i].AbsRefract = ABSR
synapse[i].mg = 0.5
for i= 0, 22 {
synapse2[i].gmax = GMAX
synapse2[i].gmaxN = GMAXN
synapse2[i].AbsRefract = ABSR
synapse2[i].mg = 0.5
for i = 0, 22 {
synapse3[i].gmax = GMAX
synapse3[i].gmaxN = GMAXN
synapse3[i].AbsRefract = ABSR
synapse3[i].mg = 0.5



objectvar vbox,vbox3, tempobj3

proc receptor_panel(){
        vbox3 = new VBox()

        xpanel("Single Release Site")
        xvalue("dAMPA gmax","GMAX",1, "set_stim()")
        xvalue("NMDA gmax","GMAXN",1, "set_stim()")
//        xvalue("Absolute Refractory", "ABSR",1, "set_stim()")

access soma
objectvar soma_clamp
soma_clamp = new VClamp(0.5)


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