Fig. 3

Histidine-containing dipeptides, except homocarnosine, are enriched in olfactory bulb. Homocarnosine is highly enriched in the cerebellum. Other regions do not have significant amounts of these dipeptides. Bar graphs are mean ± SD metabolite concentration. Asterisks (*) indicates statistical significance between the regions estimated by Welch’s two-sample t-test. (*: p ≤ 0.05, **: p ≤ 0.01, ***: p ≤ 0.001, ****: p ≤ 0.0001). OB, olfactory bulb; FCX, frontal cortex; HC, hippocampus; CBL, cerebellum