Super-resolution 2-photon microscopy reveals that the morphology of each dendritic spine correlates with diffusive but not synaptic properties

The structure of dendritic spines suggess a specialized function in compartmentalizing synaptic signals near active synapses. Indeed theoretical and experimental analyses indicate that the diffusive resistance of the spine neck is sufficient to effectively compartmentalize some signaling moleucles in a spine for the duration fo their actuated lifetime. Here we describe the application of 2-photon microsocpy combined with stimulated emission depltetion (STED-2P) to the biophysical study of the relationshop between synaptic signals and spien morphology, demonstrating the utilty of combuing STED-2P with modern optical and electrophysiological techniques. Morphological determinants of fluorescence recovery time were identified and evalated withing the context of a simple compartemental model describing diffusive transfer between spine potentials and calcium transients evoked by 2-photon glutamate uncaging were also investigated.