Figure 3.

Stability of the astrocytic contact perimeter. A) Four serial sections of a synapse showing points along which the perimeter of the synaptic cleft was measured. Asterisks mark points with an astrocytic process contact with the synaptic cleft and circles mark points without astrocytic contact. scale=250nm B) Complete point-to-point reconstruction of the entire perimeter of the synaptic cleft in (A). The asterisks indicate contact with an astrocyte, and the black line between them is the length of the perimeter in contact with astrocyte. C) Length of PSD perimeter covered by astrocyte at spines with and without a spine apparatus (SA; *p<0.001). D) Fraction of synapse perimeter covered by astrocyte (*p<0.002). E) Length of astrocyte-free PSD perimeter at synapses without (white bars) and with astrocytic contacts (black bars). Synapses with and without a spine apparatus were different from each other (*p<0.0001; bars not shown for clarity). F) Astrocyte-covered PSD perimeter versus PSD area (R²=0.02) at SA-free (triangles) and SA synapses (circles). G) PSD area by training group, SA, and astrocytic contact (*p<0.00001, CI versus naive). SA synapses with astrocytic contact are larger in the TC (p<0.003) and naïve (p<0.00001) groups than those without (bars not shown for clarity). H) Length of astrocyte-free asymmetric synapse perimeter per length of dendrite (*p<0.02).