Figure 8. Vesicle mobilization was also greatest in presynaptic boutons that contained a mitochondrion at 120 min following TBS in adult hippocampus.
(A–B) Representative EMs of presynaptic boutons (green B) from 120 min control (A1 mito, A2 no mito) and TBS (B1 mito, B2 no mito) conditions (red arrows, PSDs in A1, B2, scale bar is 0.5 µm). (C) Overall, the total number of boutons per µm3 was decreased under TBS conditions relative to control (n = 6 vol bricks per condition, see Table 1, F1,8 = 30.8, p<0.001). There were fewer single synaptic boutons (SSB, n = 6, F1,8 = 22.6, p<0.01) and nonsynaptic boutons (NSB, n = 6, F1,8 = 13.9, p<0.01) 2 hr after the onset of TBS, but the multisynaptic boutons were unchanged (MSB, n = 6, F1,8 = 0.22, p=0.65). Proportions of boutons that contained mitochondria (Mito) or were Dm ≤ 3 or Dm > 3 from a mitochondrion under control (D) and TBS (E) conditions were unchanged in the LTP relative to the control condition (n = 518, χ2=2.98, p=0.23). Representative reconstructions of synapses from adult hippocampal area CA1 at the 120 min (PSDs, red, nondocked vesicles, green, and docked vesicles, blue, lower right corner) for boutons (F1) with mitochondria (navy, Mito) and (G1) without mitochondria (No Mito). (F2) Docked vesicles decreased at 120 min after TBS relative to Con in boutons with mitochondria (F1,244 = 27.2, p<0.001), and (G2) to a lesser degree in boutons without mitochondria (F1,207 = 4.72, p<0.05) across synapses of all sizes. (F3) Nondocked vesicles also had a pronounced decrease in the TBS condition relative to Con in boutons with mitochondria (F1,297 = 112.1, p<0.001) and (G3) to a lesser degree in boutons without mitochondria (F1,250 = 35.8, p<0.001).