(A) Left panels: images of individual neurons in organotypic hippocampal slices expressing mCherry with or without LIMK1 shRNA. Magnified images of individual dendrites were acquired at the indicated times prior to and following uncaging of MNI-Glutamate on the head of the indicated spine (white circles). Scale bars: low magnification, 20 μm, magnified, 2 μm. (B) Time course of normalized spine-head volume (mean ± SEM) of stimulated and neighboring spines (control: 24 stimulated spines, 72 neighbors, 6 neurons; LIMK1 shRNA: 28 stimulated spines, 84 neighbors, 6 neurons). Average normalized spine volume (15–25 min post-uncaging) was plotted and used for statistical comparison (*: p < 0.05, Mann–Whitney U test, details in main text). (C, D) Images and time courses plotted as in A, B for neurons expressing mCherry (Control; 21 stimulated spines, 63 neighbors, 6 neurons) or mCherry, LIMK1 shRNA and shr-wt-LIMK1-GFP (LIMK1-shRNA + WT rescue; 27 stimulated spines, 81 neighbors, 8 neurons). (E, F) Images and time courses plotted as in A, B for neurons expressing mCherry (control; 23 stimulated spines, 69 neighbors, 6 neurons) or mCherry, LIMK1 shRNA and shr-CCSS-LIMK1-GFP (LIMK1-shRNA+ CCSS rescue; 28 stimulated spines, 84 neighbors, 8 neurons).