Electrically-coupled Retzius neurons (Vazquez et al. 2009)

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Accession:120910
"Dendritic electrical coupling increases the number of effective synaptic inputs onto neurons by allowing the direct spread of synaptic potentials from one neuron to another. Here we studied the summation of excitatory postsynaptic potentials (EPSPs) produced locally and arriving from the coupled neuron (transjunctional) in pairs of electrically-coupled Retzius neurons of the leech. We combined paired recordings of EPSPs, the production of artificial EPSPs (APSPs) in neuron pairs with different coupling coefficients and simulations of EPSPs produced in the coupled dendrites. ..."
Reference:
1 . Vazquez Y, Mendez B, Trueta C, De-Miguel FF (2009) Summation of excitatory postsynaptic potentials in electrically-coupled neurones. Neuroscience 163:202-12 [PubMed]
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Model Information (Click on a link to find other models with that property)
Model Type: Realistic Network; Neuron or other electrically excitable cell;
Brain Region(s)/Organism: Leech;
Cell Type(s): Leech Retzius neuron;
Channel(s): I Na,t; I A; I K; I K,Ca; I Calcium;
Gap Junctions: Gap junctions;
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Synaptic Integration;
Implementer(s):
Search NeuronDB for information about:  I Na,t; I A; I K; I K,Ca; I Calcium;
TITLE cachdend.mod    
   
UNITS {  
        (mA) = (milliamp)  
        (mV) = (millivolt)  
}  
   
NEURON {  
        SUFFIX cachdend  
        USEION ca READ eca WRITE ica  
        RANGE gcabar 
        GLOBAL minf, mexp  
}  
   
INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}  
   
PARAMETER {  
        v (mV)  
        celsius  (degC)  
        dt (ms)  
        gcabar = 4e-04 (mho/cm2)  
        eca = 125 (mV)  
}  
   
STATE {  
        m   
}  
   
ASSIGNED {  
        ica (mA/cm2)  
        minf mexp  
}  
   
BREAKPOINT {  
        SOLVE states  
        ica = gcabar*m*(v - eca)  
}  
   
UNITSOFF  
   
INITIAL {  
     rates(v)  
     m = minf  
}  
PROCEDURE states() {  :Computes state variable m  
        rates(v)      :             at the current v and dt.  
        m = m + mexp*(minf-m)  
}  
   
PROCEDURE rates(v) {:Computes rate and o  
         : ther constants at current v.  
         : Call once from HOC to   
         : initialize inf at resting v.  
     LOCAL  q10, tinc, alpha, beta, sum  
     TABLE minf, mexp DEPEND dt, celsius FROM -100 TO 100 WITH 200 

        q10 = 3^((celsius - 20)/10)  
        tinc = -dt * q10  
                :"m" calcium activation system  
        alpha = 1.5 * vtrap(-(v-20),5)  
        beta =  1.5 * exp(-(v+25)/10)  
        sum = alpha + beta  
        minf = alpha/sum  
        mexp = 1 - exp(tinc*sum)  
}  
   
FUNCTION vtrap(x,y) {  :Traps for 0 in denominator of rate eqns.  
        if (fabs(x/y) < 1e-6) {  
                vtrap = y*(1 - x/y/2)  
        }else{  
                vtrap = x/(exp(x/y) - 1)  
        }  
}  
   
UNITSON