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."
Palmer LM, Stuart GJ (2009) Membrane potential changes in dendritic spines during action potentials and synaptic input. J Neurosci 29:6897-903 [PubMed]