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 nadend.mod   squid sodium channels
 
UNITS {
        (mA) = (milliamp)
        (mV) = (millivolt)
}
 
NEURON {
        SUFFIX nadend
        USEION na READ ena WRITE ina
        RANGE gnabar
        GLOBAL minf, hinf, mexp, hexp
}
 
INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}
 
PARAMETER {
        v (mV)
        celsius (degC)
        dt (ms)
 	gnabar = 0.1250(mho/cm2) 
}
 
STATE {
        m h c
}
 
ASSIGNED {
	ena (mV) 
	ina (mA/cm2)
        minf hinf mexp hexp  
}
 
BREAKPOINT {
        SOLVE states
        ina = gnabar*m*m*m*m*h*(v - ena)
}
 
UNITSOFF
 
INITIAL {
     rates(v)
     m = minf
     h = hinf
}

PROCEDURE states() {  :Computes state variables m, h
        rates(v)      :             at the current v and dt.
        m = m + mexp*(minf-m)
        h = h + hexp*(hinf-h)
}
 
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, hinf, hexp   
	DEPEND dt, celsius

FROM -100 TO 100 WITH 200
        q10 = 2.3^((celsius - 20)/10)
        tinc = -dt * q10
                :"m" sodium activation system
        alpha = .03 * vtrap(-(v+28),15)
        beta =  2.7 * exp(-(v+53)/18)
        sum = alpha + beta
        minf = alpha/sum
        mexp = 1 - exp(tinc*sum)
                :"h" sodium inactivation system
        alpha = .045 * exp(-(v+58)/18)
        beta = 0.72 / (exp(-(v+23)/14) + 1)
        sum = alpha + beta
        hinf = alpha/sum
        hexp = 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