Figure 4.

Complex motor-cognitive challenge as inducer of ‘functional hypoxia’ in the hippocampus. (a) Experimental design: mice with no prior training were given free access to complex running wheels (CRW) for five complete days and received tamoxifen injections every other day (three in total). Normoxia mice obtained the same treatment but were kept in standard cages. All mice were perfused on day eight and brains collected for histology. (b) Representative hippocampus images from eight-week-old female CRW-exposed and normoxia mice; scale bar 100 µm. (c) Quantifications of tdTomato+/Ctip2+ neurons in CA1, CA3, and dentate gyrus revealed an increase upon exposure to CRW in both genders, with normoxia and CRW values considerably more pronounced in females. (d) Experimental design of the fear conditioning (FC) pilot experiment (24-week-old females). (e) Quantification of tdT+/Ctip2+ neurons in hippocampal CA1, CA3, and dentate gyrus regions of sham and FC mice indicate no noteworthy difference. This is likely due to the FC stimulus being too short-lived to evoke functional hypoxia. Unpaired Student’s t-test (two-tailed, Welch’s corrections); n numbers given in graphs; error bars indicate standard error of mean (SEM).