Figure 2. Spatiotemporal maturation of adult-born GC mossy fiber axon terminals in adult and aged mice. A, Examples of large complex MFBs labeled by immunohistochemistry with an antibody against GFP. B, Example of a lollipop bouton. Note short thin collateral and small bulbous terminal. C, Example of an immunolabeled en passant swelling in newborn mossy fiber axon. Note the small diameter of the swelling and that it is in line with the axon. D, Low-power image of immunolabeled adult-born mossy fibers and boutons in region CA3. E, Neurolucida reconstructions of adult-born mossy fibers and boutons taken from image in D. F, Spatial density of labeled MFBs in stratum lucidum at 8W post-TM administration in adult (3 M; n = 400), midlife (6 M; n = 252), and aged (12 M and 15 M; n = 249 and n = 261, respectively) animals. G, Axonal density measures of MFBs at various times post-TM administration in adult and aged animals (3 M: n = 135, 12 M: n = 146, 18 M: n = 128). H, Interbouton spacing measures of MFBs at various times post-TM administration in adult and aged animals (3 M: n = 135, 12 M: n = 146, 18 M: n = 128). I, Axonal density measures of en passant swellings at various times post-TM administration in adult and aged animals (3 M: n = 110, 12 M: n = 116, 18 M: n = 90). J, Axonal density measures of mossy fiber lollipop boutons at various times post-TM administration in adult and aged animals (3 M: n = 25, 12 M: n = 30, 18 M: n = 38). CA3, cornu ammons region 3; DGgc, dentate gyrus GCL; sr, stratum radiatum; sl, stratum lucidum; sp, stratum pyramidale; so, stratum oriens. Scale bars = 5 μm (A), 10 μm (B, C), 500 μm (E); *p < 0.05, **p < 0.01, ***p < 0.005, two-way ANOVA followed by Student’s t test. All values are mean ± SEM.