Leech Mechanosensory Neurons: Synaptic Facilitation by Reflected APs (Baccus 1998)

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Accession:3807
This model by Stephen Baccus explores the phenomena of action potential (AP) propagation at branch boints in axons. APs are sometimes transmitted down the efferent processes and sometimes are reflected back to the axon of AP origin or neither. See the paper for details. The model zip file contains a readme.txt which list introductory steps to follow to run the simulation. Stephen Baccus's email address: baccus@fas.harvard.edu
Reference:
1 . Baccus SA (1998) Synaptic facilitation by reflected action potentials: enhancement of transmission when nerve impulses reverse direction at axon branch points. Proc Natl Acad Sci U S A 95:8345-50 [PubMed]
Model Information (Click on a link to find other models with that property)
Model Type: Neuron or other electrically excitable cell;
Brain Region(s)/Organism:
Cell Type(s): Leech pressure (P) mechanosensory neuron;
Channel(s): I K; I K,Ca; I Sodium; I Calcium; I Potassium;
Gap Junctions:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Action Potential Initiation; Pattern Recognition; Activity Patterns; Spatio-temporal Activity Patterns; Influence of Dendritic Geometry; Detailed Neuronal Models; Synaptic Plasticity; Short-term Synaptic Plasticity; Axonal Action Potentials; Action Potentials; Facilitation; Invertebrate;
Implementer(s): Baccus, Stephen [Baccus at fas.Harvard.edu];
Search NeuronDB for information about:  I K; I K,Ca; I Sodium; I Calcium; I Potassium;
TITLE cach.mod    
   
UNITS {  
        (mA) = (milliamp)  
        (mV) = (millivolt)  
}  
   
NEURON {  
        SUFFIX cach  
        USEION ca READ eca WRITE ica  
        RANGE gcabar 
        GLOBAL minf, mexp  
}  
   
INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}  
   
PARAMETER {  
        v (mV)  
        celsius = 20 (degC)  
        dt (ms)  
        gcabar = 2e-06 (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  
  

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