CA1 pyramidal neuron: dendritic Ca2+ inhibition (Muellner et al. 2015)

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Accession:206244
In our experimental study, we combined paired patch-clamp recordings and two-photon Ca2+ imaging to quantify inhibition exerted by individual GABAergic contacts on hippocampal pyramidal cell dendrites. We observed that Ca2+ transients from back-propagating action potentials were significantly reduced during simultaneous activation of individual nearby GABAergic synapses. To simulate dendritic Ca2+ inhibition by individual GABAergic synapses, we employed a multi-compartmental CA1 pyramidal cell model with detailed morphology, voltage-gated channel distributions, and calcium dynamics, based with modifications on the model of Poirazi et al., 2003, modelDB accession # 20212.
Reference:
1 . Müllner FE, Wierenga CJ, Bonhoeffer T (2015) Precision of Inhibition: Dendritic Inhibition by Individual GABAergic Synapses on Hippocampal Pyramidal Cells Is Confined in Space and Time. Neuron 87:576-89 [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: Hippocampus;
Cell Type(s): Hippocampus CA1 pyramidal GLU cell;
Channel(s): I Calcium; I Sodium; I Potassium; I h;
Gap Junctions:
Receptor(s):
Gene(s):
Transmitter(s): Gaba;
Simulation Environment: NEURON;
Model Concept(s): Action Potentials; Dendritic Action Potentials; Active Dendrites; Calcium dynamics;
Implementer(s): Muellner, Fiona E [fiona.muellner at gmail.com];
Search NeuronDB for information about:  Hippocampus CA1 pyramidal GLU cell; I h; I Sodium; I Calcium; I Potassium; Gaba;
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CA1_multi
mechanism
previously used
ampa.mod *
cad.mod
cagk.mod *
cal.mod *
calH.mod *
cat.mod
cldif.mod
d3.mod *
gabaA_Cl.mod
h.mod *
hha_old.mod *
hha2.mod *
kadist.mod *
kaprox.mod *
kca.mod *
km.mod *
nap.mod *
nmda.mod *
                            
TITLE Slow Ca-dependent potassium current
                            :
                            :   Ca++ dependent K+ current IC responsible for slow AHP
                            :   Differential equations
                            :
                            :   Model based on a first order kinetic scheme
                            :
                            :       + n cai <->     (alpha,beta)
                            :
                            :   Following this model, the activation fct will be half-activated at 
                            :   a concentration of Cai = (beta/alpha)^(1/n) = cac (parameter)
                            :
                            :   The mod file is here written for the case n=2 (2 binding sites)
                            :   ---------------------------------------------
                            :
                            :   This current models the "slow" IK[Ca] (IAHP): 
                            :      - potassium current
                            :      - activated by intracellular calcium
                            :      - NOT voltage dependent
                            :
                            :   A minimal value for the time constant has been added
                            :
                            :   Ref: Destexhe et al., J. Neurophysiology 72: 803-818, 1994.
                            :   See also: http://www.cnl.salk.edu/~alain , http://cns.fmed.ulaval.ca
                            :   modifications by Yiota Poirazi 2001 (poirazi@LNC.usc.edu)
			    :   taumin = 0.5 ms instead of 0.1 ms	

                            INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}

                            NEURON {
                                    SUFFIX kca
                                    USEION k READ ek WRITE ik
                                    USEION ca READ cai
                                    RANGE gk, gbar, m_inf, tau_m
                                    GLOBAL beta, cac
                            }


                            UNITS {
                                    (mA) = (milliamp)
                                    (mV) = (millivolt)
                                    (molar) = (1/liter)
                                    (mM) = (millimolar)
                            }


                            PARAMETER {
                                    v               (mV)
                                    celsius = 36    (degC)
                                    ek      = -80   (mV)
                                    cai     = 2.4e-5 (mM)           : initial [Ca]i
                                    gbar    = 0.01   (mho/cm2)
                                    beta    = 0.03   (1/ms)          : backward rate constant
                                    cac     = 0.025  (mM)            : middle point of activation fct
       				    taumin  = 0.5    (ms)            : minimal value of the time cst
                                    gk
                                  }


                            STATE {m}        : activation variable to be solved in the DEs       

                            ASSIGNED {       : parameters needed to solve DE 
                                    ik      (mA/cm2)
                                    m_inf
                                    tau_m   (ms)
                                    tadj
                            }
                            BREAKPOINT { 
                                    SOLVE states METHOD derivimplicit
                                    gk = gbar*m*m*m     : maximum channel conductance
                                    ik = gk*(v - ek)    : potassium current induced by this channel
                            }

                            DERIVATIVE states { 
                                    evaluate_fct(v,cai)
                                    m' = (m_inf - m) / tau_m
                            }

                            UNITSOFF
                            INITIAL {
                            :
                            :  activation kinetics are assumed to be at 22 deg. C
                            :  Q10 is assumed to be 3
                            :
                                    tadj = 3 ^ ((celsius-22.0)/10) : temperature-dependent adjastment factor
                                    evaluate_fct(v,cai)
                                    m = m_inf
                            }

                            PROCEDURE evaluate_fct(v(mV),cai(mM)) {  LOCAL car
                                    car = (cai/cac)^2
                                    m_inf = car / ( 1 + car )      : activation steady state value
                                    tau_m =  1 / beta / (1 + car) / tadj
                                    if(tau_m < taumin) { tau_m = taumin }   : activation min value of time cst
                            }
                            UNITSON

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