Figure 4.

TBS fails to activate Rac1 in Fmr1-KO hippocampal spines. A, Photomicrographs show immunoreactivity for Rac1-GTP (green) and cofilin (red; spine marker), and merged image, in CA1 str. radiatum of a WT, control hippocampal slice. As shown, activated Rac1 is localized to a subpopulation of cofilin-labeled spines. Scale bar, 5 μm. B, Quantitative analysis shows the effect of TBS on Rac1-GTP⁺ spines in the two genotypes (levels normalized to respective genotype low-frequency stimulation controls; n = 9–11 slices/group). As shown, TBS increased the number of Rac1-GTP⁺ spines in slices from WT but not Fmr1-KO mice. **p < 0.001, one-tailed Student's t test; planned comparison.