Effects of KIR current inactivation in NAc Medium Spiny Neurons (Steephen and Manchanda 2009)

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Accession:121060
"Inward rectifying potassium (KIR) currents in medium spiny (MS) neurons of nucleus accumbens inactivate significantly in ~40% of the neurons but not in the rest, which may lead to differences in input processing by these two groups. Using a 189-compartment computational model of the MS neuron, we investigate the influence of this property using injected current as well as spatiotemporally distributed synaptic inputs. Our study demonstrates that KIR current inactivation facilitates depolarization, firing frequency and firing onset in these neurons. ..."
Reference:
1 . Steephen JE, Manchanda R (2009) Differences in biophysical properties of nucleus accumbens medium spiny neurons emerging from inactivation of inward rectifying potassium currents. J Comput Neurosci 27:453-70 [PubMed]
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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: Basal ganglia;
Cell Type(s): Nucleus accumbens spiny projection neuron;
Channel(s): I Na,p; I L high threshold; I T low threshold; I p,q; I A; I h; I K,Ca; I CAN; I A, slow; I Krp; I R;
Gap Junctions:
Receptor(s): AMPA; NMDA; Gaba;
Gene(s): Cav1.3 CACNA1D; Cav1.2 CACNA1C; IRK;
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Action Potential Initiation; Ion Channel Kinetics; Action Potentials; Synaptic Integration; Delay;
Implementer(s): Steephen, John Eric [johneric at iitb.ac.in];
Search NeuronDB for information about:  AMPA; NMDA; Gaba; I Na,p; I L high threshold; I T low threshold; I p,q; I A; I h; I K,Ca; I CAN; I A, slow; I Krp; I R;
TITLE NaP channel

UNITS {
        (mV) = (millivolt)
	(mA) = (milliamp)      
	(S)  = (siemens)
}
NEURON {
        SUFFIX NaP
        USEION na READ ena WRITE ina
        RANGE  gmax, ina
}
 
PARAMETER {
	gmax   =   1.3802e-7 (S/cm2)	: 4e-5 in soma; 1.3802e-7 in dends

	mvhalf = -52.6		(mV)	: Magistretti 1999, Fig 4
	mslope = -4.6		(mV)	: Magistretti 1999, Fig 4

	hvhalf = -48.8		(mV)	: Magistretti 1999, Fig 4
	hslope = 10.0		(mV)	: Magistretti 1999, Fig 4
}
 
STATE { m h }
 
ASSIGNED {
	ena		(mV)
        v 		(mV)
        ina		(mA/cm2)
        g		(S/cm2)

        minf
	hinf	

	mtau	(ms)			: Traub 2003, Table A2
   }
 
BREAKPOINT {
        SOLVE state METHOD cnexp
        g = gmax * m * h  
        ina = g * ( v - ena )
:        VERBATIM
:        	printf("Ena is %g\n", ena);
:        ENDVERBATIM
}
 

 
INITIAL {
	rates(v)
	m = minf
	h = hinf
}

FUNCTION_TABLE tabhtau (v(mV)) (ms)		: Magistretti 1999, Fig 8A

DERIVATIVE state { 
        rates(v)
        m' = (minf - m) / mtau
        h' = (hinf - h) / tabhtau(v)    
}
 
PROCEDURE rates(v (mV)) {  
	TABLE minf, hinf, mtau
		FROM -120 TO 40 WITH 160

		minf = 1 / (1 + exp( (v - mvhalf) / mslope))
		hinf = 1 / (1 + exp( (v - hvhalf) / hslope))
		
		UNITSOFF
		if (v < -40) {			: Traub 2003, Table A2
			mtau = 0.025 + 0.14 * exp( (v + 40 ) / 10)
		} else {
			mtau = 0.02 + 0.145 * exp( (-v - 40) / 10)
		}
		UNITSON
}