Membrane potential changes in dendritic spines during APs and synaptic input (Palmer & Stuart 2009)

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Accession:120798
" ... Finally, we used simulations of our experimental observations in morphologically realistic models to estimate spine neck resistance. These simulations indicated that spine neck resistance ranges up to ~500 M Ohm. Spine neck resistances of this magnitude reduce somatic EPSPs by ~15%, indicating that the spine neck is unlikely to act as a physical device to significantly modify synaptic strength."
Reference:
1 . Palmer LM, Stuart GJ (2009) Membrane potential changes in dendritic spines during action potentials and synaptic input. J Neurosci 29:6897-903 [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): Active Dendrites; Influence of Dendritic Geometry; Synaptic Integration;
Implementer(s): Morse, Tom [Tom.Morse at Yale.edu]; Stuart, Greg J. [greg.stuart at anu.edu.au];
: this model is built-in to neuron with suffix syn_g

COMMENT
synaptic current with exponential rise and decay conductance defined by
        i = g * (v - e)      i(nanoamps), g(micromhos);
        where
         g = 0 for t < onset and
         g=amp*((1-exp(-(t-onset)/tau0))-(1-exp(-(t-onset)/tau1)))
          for t > onset
ENDCOMMENT
					       
INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}

NEURON {
	POINT_PROCESS syn_g
	RANGE onset, tau0, tau1, gmax, e, i
	NONSPECIFIC_CURRENT i
}
UNITS {
	(nA) = (nanoamp)
	(mV) = (millivolt)
	(umho) = (micromho)
}

PARAMETER {
	onset=0  (ms)
	tau0=0.3 (ms)
	tau1=3.0 (ms)
	gmax=0	 (umho)
	e=0	 (mV)
	v	 (mV)
}

ASSIGNED { i (nA)  g (umho) }

LOCAL   a[2]
LOCAL   tpeak
LOCAL   adjust
LOCAL   amp

BREAKPOINT {
        g = cond(t)
	i = g*(v - e)
}

FUNCTION cond(x) {
	tpeak=tau0*tau1*log(tau0/tau1)/(tau0-tau1)
	adjust=1/((1-exp(-tpeak/tau0))-(1-exp(-tpeak/tau1)))
	amp=adjust*gmax
	if (x < onset) {
		cond = 0
	}else{
		a[0]=1-exp(-(x-onset)/tau0)
		a[1]=1-exp(-(x-onset)/tau1)
		cond = amp*(a[0]-a[1])
	}
}

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