Figure 3.

Repetitive magnetic stimulation in vitro induces postsynaptic structural plasticity in CA1 stratum radiatum. A, B, Samples of nonstimulated age- and time-matched control (left column) and stimulated (right column) slice cultures fixed at 3 h pms stained for synaptophysin (A; n = 6) and F-actin (B; n = 11). The mean fluorescence intensity was analyzed in the stratum radiatum (rad) of area CA1. A significant increase in F-actin, but not in synaptophysin fluorescence intensity (fluo. intens.) was observed. Scale bar, 150 μm. C–E, Time-lapse imaging of identified individual spines of side branches of apical dendrites of GFP-expressing CA1 pyramidal neurons in the stratum radiatum (C) revealed no significant changes in spine density (D), but changes in spine size following rMS (E; n = 10 control vs n = 13 rMS segments; from 10 control and 13 rMS-treated cultures, respectively). Spines with a small initial size demonstrated a significant increase in size following rMS (E). Note that data presented in E demonstrate spine sizes from identified individual spines repeatedly measured pms at given time points, corrected for spontaneous fluctuations in mean spine size of the respective spine groups (small, <0.45 μm²; medium, 0.45 μm² ≤ x < 0.65 μm²; large, ≥0.65 μm²) in the control group. The asterisks in C indicate a spine in control cultures that does not change in size; the arrowheads point at a small spine that transiently increases in size after rMS. Scale bar: C, 1 μm.