Fig. 3.

Dendritic spines and the cytoskeleton. Immunofluorescence staining with phalloidin, a marker of endogenous F-actin in cortical neurons, reveals enrichment of actin in dendrites and dendritic spines. Schematic drawing of how extracellular signals can act via specific receptors and act via small GTPases to regulate actin dynamics and/or receptor trafficking. The dynamic actin cytoskeleton confers much of the structure of the dendritic spines, and alterations in synaptic expression of glutamate receptors (e.g., AMPA receptors) are thought to play a major role in modulating synaptic function.