Dendritic spine geometry is critical for AMPA receptor expression in hippocampal CA1 pyramidal neurons

Dendritic spines serve as preferential sites of excitatory synaptic connect ions and are pleomorphic. To address the structure-function relationship of the dendritic spines, we used two-photon uncaging of glutamate to allow ma pping of functional glutamate receptors at the level of the single synapse. Our analyses of the spines of CA1 pyramidal neurons reveal that AMPA (alph a -amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid)-type glutamate recep tors are abundant (up to 150/spine) in mushroom spines but sparsely distrib uted in thin spines and filopodia. The latter may be serving as the structu ral substrates of the silent synapses that have been proposed to play roles in development and plasticity of synaptic transmission. Our data indicate that distribution of functional AMPA receptors is tightly correlated with s pine geometry and that receptor activity is independently regulated at the level of single spines.