ERG current in repolarizing plateau potentials in dopamine neurons (Canavier et al 2007)

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Accession:100603
"Blocking the small-conductance (SK) calcium-activated potassium channel promotes burst firing in dopamine neurons both in vivo and in vitro. ... We focus on the underlying plateau potential oscillation generated in the presence of both apamin and TTX, so that action potentials are not considered. We find that although the plateau potentials are mediated by a voltage-gated Ca2+ current, they do not depend on the accumulation of cytosolic Ca2+, then use a computational model to test the hypothesis that the slowly voltage-activated ether-a-go-go–related gene (ERG) potassium current repolarizes the plateaus. The model, which includes a material balance on calcium, is able to reproduce the time course of both membrane potential and somatic calcium concentration, and can also mimic the induction of plateau potentials by the calcium chelator BAPTA." See paper for more.
Reference:
1 . Canavier CC, Oprisan SA, Callaway JC, Ji H, Shepard PD (2007) Computational model predicts a role for ERG current in repolarizing plateau potentials in dopamine neurons: implications for modulation of neuronal activity. J Neurophysiol 98:3006-22 [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): Substantia nigra pars compacta DA cell;
Channel(s): I L high threshold; I h; I K,Ca; I Calcium; I_HERG;
Gap Junctions:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: C or C++ program; FORTRAN;
Model Concept(s): Ion Channel Kinetics; Oscillations; Calcium dynamics;
Implementer(s): Canavier, CC;
Search NeuronDB for information about:  Substantia nigra pars compacta DA cell; I L high threshold; I h; I K,Ca; I Calcium; I_HERG;
#define ALPHA 0.0 /* Factor for pump electrogeneity */
#define VAR 1 /* make ERG tau variable*/
#define RED 0 /* makes IH instantaneous*/
#define IN 1 /* switch to turn inactivation on*/
#define N 6 /* 6 */
#define C 8
#define CM 0.0158 /* 0.0158 pF */
#define RADIUS 15.0 /* uM */
#define FF 0.025 /* 0.015 0.025 0.00025 */
#define V_SET -38  /* mV */
#define V 0  /* mV */
#define CA 3  /* mM */
#define D_CAL 2 
#define D_ERG 1 
#define D_H 4 
#define F_ERG 5 
#define I_CAL 0  
#define I_KSK 1 
#define I_ERG 2
#define I_H 3 
#define I_L 4
#define I_CAB 5 
#define I_CAP 6 
#define I_CLAMP 7 
#define I_STIM 0.000 /* range -0.025 to 0.034 0.021 -0.0168 50 pA for 7a*/
#define I_CAP_MAX  0.5    /* nA*/
#define E_CA  50.0
#define E_K  -85.0
#define E_H  -29.0
#define E_L  -65.5 /* -66 -54.00flag */
#define G_CLAMP  0.0 /* 1.0 */
#define G_CAL 0.0023 /*0.0023 uS*/
#define G_KSK 0.000 /*0.001 0.0015*/
#define G_ERG 0.015 /* 0.015 uS flag */
#define G_H   0.008 /* 0.008 uS*/
#define G_L   0.0055 /*0.0055 uS flag*/
#define G_CAB    0.0002  
#define K_CAP    0.000500 /*mM*/
#define K_SK    0.000190 /*mM*/
#define V_HALF_D_CAL -45.0
#define V_SLOPE_D_CAL 7.0
#define TAU_HALF_D_CAL -70.0
#define TAU_SLOPE_D_CAL 25.0
#define TAU1_D_CAL 0.3
#define TAU2_D_CAL 18.0
#define V_HALF_D_ERG -35.0 /* -50 mV */
#define V_SLOPE_D_ERG 5.0 /* 5.0 */
#define V_HALF_F_ERG -70.0 /* -70 mV*/
#define V_SLOPE_F_ERG -20.0
#define AI0 0.1 /* 0.1 */
#define AI1 0.02 
#define BI0 0.003 /* 0.003*/
#define BI1 -0.03
#define AA0 0.00225  /* 0.00225 0.012*/
#define AA1 0.12  /* 0.12 0.15 */  
#define BA0 0.4e-4 /* 0.4e-4*/
#define BA1 -0.05
#define TAU1_D_ERG 4000.0 /* 5000.0 flag */
#define TAU1_F_ERG 15.0 /* 15 */
#define V_HALF_D_H -77.6   /* -77.624*/
#define V_SLOPE_D_H -17.317/* -17.317 */
#define TAU_HALF_D_H -22.686
#define TAU_SLOPE_D_H 29.597  
#define TAU1_D_H 26.21
#define TAU2_D_H 3136.0

#define VHOLD -80.0
#define P1_V  -40.0
#define P2_V -60.0
#define P3_V -60.0
#define P1_ON 0.1
#define P1_OFF 50000.0
#define P2_OFF 50000.0
#define P3_OFF 50000.0

/* INTEGRATION PARAMETERS */

/* these only apply to C code */
#define LWORK 199 /* N(4*N + 8)+7*/
#define LIWORK 25 /*3*N+7*/
#define LRCONT 28 /*4*N+4*/
#define DURATION 5
#define TIMEON 0
#define TIMEOFF 0
#define PERIOD  250
#define ENDTIME 10000
#define START_TIME  0

#define PI  3.1416
#define FARADAY  96520 
#define R  8.3134 
#define celsius 10.00 
#define T celsius + 273
#define PRINT  0
#define DEBUG 0
#define PULSEON 300000
#define PULSEOFF 300000


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