D2 dopamine receptor modulation of interneuronal activity (Maurice et al. 2004)

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Accession:98005
"... Using a combination of electrophysiological, molecular, and computational approaches, the studies reported here show that D2 dopamine receptor modulation of Na+ currents underlying autonomous spiking contributes to a slowing of discharge rate, such as that seen in vivo. Four lines of evidence support this conclusion. ... Fourth, simulation of cholinergic interneuron pacemaking revealed that a modest increase in the entry of Na+ channels into the slow-inactivated state was sufficient to account for the slowing of pacemaker discharge. These studies establish a cellular mechanism linking dopamine and the reduction in striatal cholinergic interneuron activity seen in the initial stages of associative learning." See paper for more and details.
Reference:
1 . Maurice N, Mercer J, Chan CS, Hernandez-Lopez S, Held J, Tkatch T, Surmeier DJ (2004) D2 dopamine receptor-mediated modulation of voltage-dependent Na+ channels reduces autonomous activity in striatal cholinergic interneurons. J Neurosci 24:10289-301 [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): Neostriatum interneuron ACh cell;
Channel(s): I Na,t; I K; I h; I K,Ca; I Sodium; I Calcium; I Potassium;
Gap Junctions:
Receptor(s): D2;
Gene(s): D2 DRD2; HCN1; HCN2;
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Activity Patterns; Action Potentials; Parkinson's;
Implementer(s): Held, Joshua [j-held at northwestern.edu];
Search NeuronDB for information about:  Neostriatum interneuron ACh cell; D2; I Na,t; I K; I h; I K,Ca; I Sodium; I Calcium; I Potassium;
: HH P-type Calcium current
: Created 8/13/02 - nwg

: copy by josh for cholinergic interneuron

NEURON {
	SUFFIX cap_ch
	USEION ca READ cai, cao WRITE ica
	RANGE gbar, ica
	GLOBAL minf,mtau
	GLOBAL monovalConc, monovalPerm
}

UNITS {
	(mV) = (millivolt)
	(mA) = (milliamp)
	(mM) = (milli/liter)
	F = 9.6485e4   (coul)
	R = 8.3145 (joule/degC)
}

PARAMETER {
	v (mV)

	gbar = .00005	(cm/s)
	monovalConc = 140     (mM)
	monovalPerm = 0

	cai             (milli/liter)
	cao             (milli/liter)
}

ASSIGNED {
	ica            (mA/cm2)
        minf
	mtau           (ms)
	T              (degC)
	E              (volts)
}

STATE {
	m
}

INITIAL {
	rates(v)
	m = minf
}

BREAKPOINT {
	SOLVE states METHOD cnexp
	ica = (1e3) * gbar * m * ghk(v, cai, cao, 2)
}

DERIVATIVE states {
	rates(v)
	m' = (minf - m)/mtau
}

FUNCTION ghk( v(mV), ci(mM), co(mM), z)  (coul/cm3) { LOCAL Ci
	T = 22 + 273.19  : Kelvin
        E = (1e-3) * v
        Ci = ci + (monovalPerm) * (monovalConc)        : Monovalent permeability
	if (fabs(1-exp(-z*(F*E)/(R*T))) < 1e-6) { : denominator is small -> Taylor series
		ghk = (1e-6) * z * F * (Ci-co*exp(-z*(F*E)/(R*T)))*(1-(z*(F*E)/(R*T)))
	} else {
		ghk = (1e-6) * z^2*(E*F^2)/(R*T)*(Ci-co*exp(-z*(F*E)/(R*T)))/(1-exp(-z*(F*E)/(R*T)))
	}
}

PROCEDURE rates (v (mV)) {
        UNITSOFF
	minf = 1/(1+exp(-(v - (-19)) / 5.5))
	mtau = (mtau_func(v)) * 1e3
        UNITSON
}

FUNCTION mtau_func( v (mV) ) (ms) {
        UNITSOFF
        if (v > -50) {
            mtau_func = .000191 + .00376*exp(-((v-(-41.9))/27.8)^2)
        } else {
            mtau_func = .00026367 + .1278 * exp(.10327*v)
        }
        UNITSON
}

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