Spike frequency adaptation in spinal sensory neurones (Melnick et al 2004)

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Accession:62284
Using tight-seal recordings from rat spinal cord slices, intracellular labelling and computer simulation, we analysed the mechanisms of spike frequency adaptation in substantia gelatinosa (SG) neurones. Adapting-firing neurones (AFNs) generated short bursts of spikes during sustained depolarization and were mostly found in lateral SG. ... Ca2 + -dependent conductances do not contribute to adapting firing. Transient KA current was small and completely inactivated at resting potential suggesting that adapting firing was mainly generated by voltage-gated Na+ and delayed-rectifier K+ (KDR ) currents. ... Computer simulation has further revealed that down-regulation of Na+ conductance represents an effective mechanism for the induction of firing adaptation. It is suggested that the cell-specific regulation of Na+ channel expression can be an important factor underlying the diversity of firing patterns in SG neurones. See paper for more and details.
Reference:
1 . Melnick IV, Santos SF, Safronov BV (2004) Mechanism of spike frequency adaptation in substantia gelatinosa neurones of rat. J Physiol 559:383-95 [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):
Channel(s):
Gap Junctions:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Short-term Synaptic Plasticity; Spike Frequency Adaptation;
Implementer(s): Safronov, Boris [safronov at ibmc.up.pt];
TITLE HH k channel channel
: Hodgkin - Huxley k channel

: The model used in Safronov et al. 2000 
:
: 5/17/2017  Revised by N.T. Carnevale for the sake of conceptual clarity
: and to facilitate attributed reuse.
: In this version, the reference temperature is 23 deg C
: and the value assigned to celsius is the actual operating temperature
: in degrees celsius.

NEURON {
	SUFFIX B_A
	USEION k READ ek WRITE ik
	RANGE gkbar, ik
	GLOBAL inf
}

UNITS {
	(mA) = (milliamp)
	(mV) = (millivolt)
}

INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}
PARAMETER {
	v (mV)
	dt (ms)
	gkbar=0 (mho/cm2) <0,1e9>
	ek = -84 (mV)
:	celsius = 6.3 (degC)
	celsius = 23 (degC) : actual operating temperature

}
STATE {
	n h
}
ASSIGNED {
	ik (mA/cm2)
	inf[2]
	
}
LOCAL	fac[2]

INITIAL {
	rate(v*1(/mV))
	n = inf[0]
	h = inf[1]
}

BREAKPOINT {
	SOLVE states
	ik = gkbar*n*n*n*n*h*(v - ek)
}

PROCEDURE states() {	: exact when v held constant
	rate(v*1(/mV))
	n = n + fac[0]*(inf[0] - n)
	h = h + fac[1]*(inf[1] - h)
	VERBATIM
	return 0;
	ENDVERBATIM
}

UNITSOFF
FUNCTION alp(v(mV),i) { LOCAL a,b,c,q10 :rest=-70 order n,h
	v = v
:	q10 = 3^((celsius - 6.3)/10)
	q10 = 3^((celsius - 23)/10) : actual reference temperature
	if (i==0) {
		alp = q10 * .032*expM1(-v - 64 - 0 , 6)
	}else if (i==1){
		alp = q10 * 0.05/(exp((v + 86 + 0)/10)+1)
	}
}

FUNCTION bet(v,i) { LOCAL a,b,c,q10 :rest=-70 order n,h
	v = v
:	q10 = 3^((celsius - 6.3)/10)
	q10 = 3^((celsius - 23)/10) : actual reference temperature
	if (i==0) {
		bet = q10*0.203*exp((-v - 40 - 0)/24)
	}else if (i==1){
		bet = q10 * 0.05/(exp((-v - 86 - 0)/10)+1)
	}
}

FUNCTION expM1(x,y) {
        if (fabs(x/y) < 1e-6) {
                expM1 = y*(1 - x/y/2)
        }else{
                expM1 = x/(exp(x/y) - 1)
        }
}


PROCEDURE rate(v) {LOCAL a, b, tau :rest = -70
	TABLE inf, fac DEPEND dt, celsius FROM -160 TO 100 WITH 200
	FROM i=0 TO 1 {
		a=alp(v,i)  b=bet(v,i)
		tau = 1/(a+b)
		inf[i] = a/(a+b)
		fac[i] = (1 - exp(-dt/tau))
	}
}
UNITSON

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