RhoA signaling is necessary for stable expression of LTP. (A) Western blots from vehicle (veh)- or adenosine (Ado)-treated slices probed with antisera for total RhoA, Cdc42, or Rac1 (left) or (in the same samples) processed by pull-down assay (middle) using GST-Rhotekin (for RhoA)– or GST-PAK (for Cdc42 and Rac1)–binding domains. (B) Group mean (±SEM) band OD measures from pull-downs (Active) or total protein measures for the indicated GTPases are expressed as adenosine treatment/control (*, P < 0.05; **, P < 0.01 vs. vehicle). (C) Western blot and plots of band densities show pPAK and pCofilin levels in slices treated with 0.1 µM of the ROCK inhibitor H1152 for 30 min or vehicle; H1152 selectively suppressed pCofilin ir (mean ± SEM; ***, P < 0.001 vs. vehicle). (D, left) Slices were treated with H1152 for 30 min before TBS and harvested 7 min after TBS for immunofluorescence; numbers of pCofilin⁺ PSDs in the zone of physiological recording are shown (*, P < 0.05 vs. vehicle/control; #, P < 0.05 vs. H1152 alone). (right) Object counts, presented as the mean (±SEM) difference between TBS + treatment and treatment alone groups (TBSΔ; *, P < 0.05), show that H1152 blocks the TBS effect. (E) Images show in situ F-actin labeling in slices receiving TBS alone or TBS + ROCK inhibitor. Group mean (±SEM) numbers of phalloidin-labeled spines/100 µm³ for TBS- and control-stimulated (con) slices in the absence (ACSF) or presence of H1152 are shown (*, P < 0.05 vs. control; #, P < 0.05 vs. ACSF-TBS). (F) Slices were treated with H1152 (solid horizontal line) for 50 min before TBS (arrow). H1152-treated slices (closed circles) showed normal initial potentiation compared with vehicle controls, but LTP failed to stabilize. (top) Baseline (left) and 60-min post-TBS (right) fEPSP traces. Vertical bar, 1 mV; horizontal bar, 10 ms. (B and F) Dashed lines indicate baseline levels. Bar, 5 µm.