Vulnerable neurons have a higher proportion of varicosities that are positive for Syt-1. A, Density plot of Syt-1 intensity [arbitrary units (AU), fluorescence] in all segmented varicosities included for analysis (red line indicate quintiles). B, Quantification of the proportion of varicosities that are positive for Syt-1. Box and whiskers plots, in the style of Tukey, where the median value is indicated, and the lower and upper hinges correspond to the first and third quartiles, Kruskal–Wallis multiple comparison, p-values adjusted with the Bonferroni method, *p < 0.05. Shared control estimation plot: mean difference for comparisons against the shared control, SNc, using Data Analysis with Bootstrap Estimation, with 5000 bootstrap resamples. All confidence intervals are bias-corrected and accelerated. C, Quantification of intervaricose distance (nearest neighbor analysis of segmentations). Box and whiskers plots, in the style of Tukey, where the median value is indicated, and the lower and upper hinges correspond to the first and third quartiles, Kruskal–Wallis multiple comparison, p-values adjusted with the Bonferroni method, *p < 0.05. Shared control estimation plot: mean difference for comparisons against the shared control, SNc, using Data Analysis with Bootstrap Estimation, with 5000 bootstrap resamples. All confidence intervals are bias-corrected and accelerated. D, Mean number of varicosities per unit length of axonal domain. Box and whiskers plots, in the style of Tukey, where the median value is indicated, and the lower and upper hinges correspond to the first and third quartiles, Kruskal–Wallis multiple comparison, p-values adjusted with the Bonferroni method, *p < 0.05. Shared control estimation plot: mean difference for comparisons against the shared control, SNc, using Data Analysis with Bootstrap Estimation, with 5000 bootstrap resamples. All confidence intervals are bias-corrected and accelerated. B to C have a supplementary plot of all data grouped as vulnerable and resilient, where an independent two-group Mann–Whitney U test was performed, and an asterisk denotes p < 0.05. Precise values can be found in the supplementary tables alongside unpaired Gardner–Altman two group estimation plots. Detailed statistical tests and multiple comparisons can be found in Extended Data Table 8-1. LC, locus ceoruleus; DMV, dorsal motor nucleus of the vagus; XII, hypoglossal nucleus; SNc, substantia nigra pars compacta; VTA, ventral tegmental area; R, raphé; STR, striatum.