Excitotoxic loss of dopaminergic cells in PD (Muddapu et al 2019)

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Accession:244384
"... A couple of the proposed mechanisms, however, show potential for the development of a novel line of PD (Parkinson's disease) therapeutics. One of these mechanisms is the peculiar metabolic vulnerability of SNc (Substantia Nigra pars compacta) cells compared to other dopaminergic clusters; the other is the SubThalamic Nucleus (STN)-induced excitotoxicity in SNc. To investigate the latter hypothesis computationally, we developed a spiking neuron network-model of SNc-STN-GPe system. In the model, prolonged stimulation of SNc cells by an overactive STN leads to an increase in ‘stress’ variable; when the stress in a SNc neuron exceeds a stress threshold, the neuron dies. The model shows that the interaction between SNc and STN involves a positive-feedback due to which, an initial loss of SNc cells that crosses a threshold causes a runaway-effect, leading to an inexorable loss of SNc cells, strongly resembling the process of neurodegeneration. The model further suggests a link between the two aforementioned mechanisms of SNc cell loss. Our simulation results show that the excitotoxic cause of SNc cell loss might initiate by weak-excitotoxicity mediated by energy deficit, followed by strong-excitotoxicity, mediated by a disinhibited STN. A variety of conventional therapies were simulated to test their efficacy in slowing down SNc cell loss. Among them, glutamate inhibition, dopamine restoration, subthalamotomy and deep brain stimulation showed superior neuroprotective-effects in the proposed model."
Reference:
1 . Muddapu VR, Mandali A, Chakravarthy VS, Ramaswamy S (2019) A Computational Model of Loss of Dopaminergic Cells in Parkinson's Disease Due to Glutamate-Induced Excitotoxicity. Front Neural Circuits 13:11 [PubMed]
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Model Information (Click on a link to find other models with that property)
Model Type: Realistic Network;
Brain Region(s)/Organism: Basal ganglia; Subthalamic Nucleus;
Cell Type(s): Abstract Izhikevich neuron;
Channel(s):
Gap Junctions:
Receptor(s): AMPA; Gaba; NMDA;
Gene(s):
Transmitter(s): Dopamine; Glutamate; Gaba;
Simulation Environment: MATLAB;
Model Concept(s): Deep brain stimulation; Parkinson's;
Implementer(s): Muddapu, Vignayanandam R. [vignan.0009 at gmail.com]; Chakravarthy, Srinivasa V. [schakra at iitm.ac.in];
Search NeuronDB for information about:  AMPA; NMDA; Gaba; Dopamine; Gaba; Glutamate;
function [temptime2]=sub_sampling_firings(linear_S,Nneur,Ttime,dt)

%% Subsampling of spike time data

% Arguments
%linear_S: Spike times (linear_S=[times,number ID])
%Nneur: Number of neurons
%Ttime: Simulation time
%dt: TIme step of simulation

% Output
%temptime2: Subsampled input data

%%
%Created on 2016
%@author: Vignayanandam R. Muddapu (CNS@IIT-Madras)

%%
Ntime=(Ttime)*dt;
temptime2=[];
test2=zeros(Nneur,Ntime);
for neur=1:Nneur
    test1=zeros(1,Ttime);
    temptime=linear_S((linear_S(:,2)==neur));
    
    % To remove values beyond No. of iteration
    if sum(temptime>Ttime)
        inde= temptime>Ttime;
        temptime(inde)=[];
    end
    
    % To remove values with decimal points
    temptime=round(temptime);
    test1(temptime)=ones(size(temptime));
    
    start=1;stop=1/dt;%1/dt=200 for 0.005
    for te=1:Ntime
        
        if(sum(test1(start:stop))>0)
            test2(te)=1;
        else
            test2(te)=0;
        end
        start=start+(1/dt);stop=stop+(1/dt);
    end
    inds=find(test2==1);
    temptime2=[temptime2; inds,neur+0*inds];

end