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DG adult-born granule cell: nonlinear a5-GABAARs control AP firing (Lodge et al, 2021)

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Accession:267106
GABA can depolarize immature neurons close to the action potential (AP) threshold in development and adult neurogenesis. Nevertheless, GABAergic synapses effectively inhibit AP firing in newborn granule cells of the adult hippocampus as early as 2 weeks post mitosis. Parvalbumin and dendrite-targeting somatostatin interneurons activate a5-subunit containing GABAA receptors (a5-GABAARs) in young neurons, which show a voltage dependent conductance profile with increasing conductance around the AP threshold. The present computational models show that the depolarized GABA reversal potential promotes NMDA receptor activation. However, the voltage-dependent conductance of a5-GABAARs in young neurons is crucial for inhibition of AP firing to generate balanced and sparse firing activity.
Reference:
1 . Lodge M, Hernandez MC, Schulz JM, Bischofberger J (2021) Sparsification of AP firing in adult-born hippocampal granule cells via voltage-dependent a5-GABAA receptors Cell Reports [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: Dentate gyrus;
Cell Type(s): Dentate gyrus granule GLU cell;
Channel(s): I K; I Krp; I Na,t;
Gap Junctions:
Receptor(s): AMPA; GabaA; NMDA;
Gene(s):
Transmitter(s): Gaba; Glutamate;
Simulation Environment: NEURON;
Model Concept(s): Action Potentials; Detailed Neuronal Models; Development; Neurogenesis; Pattern Separation; Synaptic Integration;
Implementer(s): Schulz, Jan M [j.schulz at unibas.ch]; Bischofberger, Josef;
Search NeuronDB for information about:  Dentate gyrus granule GLU cell; GabaA; AMPA; NMDA; I Na,t; I K; I Krp; Gaba; Glutamate;
//******   membrane properties ************************************
// Passive parameters from Heigele et al. 2016, Nature Neuroscience 19:263-70
//
celsius = 35
global_ra=200.00		            //Ohm cm 
spine_fact= 1.5                     // to compensate for addional membrane area by spines
Cm= 1                               // specific membrane capacitance in uF/cm^2 
Vleak=-80                           // mV
Vrest=-80	        
Rin_target = 0.1735                 // GOhm
Rin = Rin_target*spine_fact

proc PassiveMembrane(){				
 Gin 	= 1/Rin  				    // Gin: 5.0 nS  
 Decay	= 25	                    // membrane tau: 25 ms
 Cap 	= Decay * Gin	            // Capacitance: 125 pF
 Rm	= 1000 * Decay 		            // Rmem: 25000 Ohm cm^2
}

PassiveMembrane()

ndend=6
load_file("GC-Ball.hoc")

forall {
    insert pas	
    e_pas=Vleak
    Ra=global_ra 
    v_init = -80    
    }
    
forsec "dendrite"{          
    g_pas=spine_fact/Rm   
    cm=Cm*spine_fact
    }


// specific membrane reistivity and capacitance for absence of spines 
forsec "soma"{    
    g_pas=1/Rm
    cm=Cm
    }
    
forsec "axon"{     
    g_pas=1/Rm
    cm=Cm
    }
    
forsec "AIS"{      
    g_pas=1/Rm
    cm=Cm
    }

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