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. 2018 Jul 25;99(2):275–282.e3. doi: 10.1016/j.neuron.2018.06.015

Figure 1.

Figure 1

Presynaptic Active Zone Size Scales with Dendrite Diameter and Distance from Cell Bodies

(A) SBFSEM low-magnification image showing experimental design: 3 areas (red, proximal; purple, medial; blue, distal) at increasing distances from the pyramidal cell layer in the stratum oriens region of the CA1; S.O., stratum oriens; S.P., stratum pyramidale. Scale bar, 50 μm.

(B) SBFSEM single section images (left panels), with corresponding 3D reconstructions (right panels), showing presynaptic (yellow) and postsynaptic (green) structures with PSDs (red) and AZs (light blue) highlighted. Top left panel shows a spine head (star) connected through the narrower spine neck to the main dendritic shaft (asterisk). Scale bars, 0.5 μm.

(C) Two dendrites (thin dendrite left, thick dendrite right) reconstructed in 3D with spine heads in purple and boutons in green. Scale bar, 1 μm.

(D–G) Data from a postnatal day 22 animal. (D) Cumulative fraction plot: dendrites reconstructed in the proximal area have larger diameters than distal and medial area dendrites; n = 35 dendrites, p < 0.001 ANOVA; proximal-distal adjusted p < 0.001; proximal-medial adjusted p < 0.01, Tukey’s multiple comparison test. (E) Cumulative fraction plot of AZ sizes, which are a larger in the proximal group; n = 604 AZs, p < 0.0001 Kruskal-Wallis test; proximal-medial adjusted p < 0.0001, proximal-distal adjusted p = 0.0001 Dunn’s multiple comparison test. (F) Smaller AZs tend to be found on thinner dendritic processes, n = 556 AZs, Spearman’s correlation; colors indicate area in which the dendrites were reconstructed. (G) Average AZ size (per dendrite) positively correlates with dendrite diameter, n = 35 dendrites, Spearman’s correlation.

(H–K) Data from a postnatal day 100 animal. (H) Proximal dendrites are thicker than distal dendrites, cumulative fraction plot n = 26 dendrites, p < 0.05 unpaired t test with Welch’s correction. (I) Cumulative fraction plot of AZ sizes, which are a larger in the proximal group; n = 505 AZs, p < 0.0001 Kolmogorov-Smirnov test. (J) Smaller AZs tend to be found on thinner dendritic processes, n = 505 AZs, Spearman’s correlation; colors indicate area in which the dendrites were reconstructed. (K) Average AZ size (per dendrite) positively correlates with dendrite diameter, n = 26 dendrites, Spearman’s correlation. See also Figure S1. Data are represented as mean ± SEM.