Figure 1. Ontogeny of GLP-1 projections into the PVH.

Maximum intensity projections of confocal images through the PVH of WT (A–E) and Lep^ob/ob (F–J) mice illustrate the density of GLP-1 immunoreactive fibers (green) present at postnatal ages P6, P10, P16, P24, and P60. In WT mice, GLP-1 fibers first reach the PVH at P6 and continue to increase in density over time, reaching maturity by 2 months of age. In Lep^ob/ob mice, a significant increase in GLP-1 fiber density emerged at P16 and was maintained into adulthood. Boxes indicate location of ROIs used for quantitative analysis. Student's t-test was used to test for significant differences between genotypes at each age examined. Asterisk denotes p-values<0.05. Abbreviations: 3V, third ventricle; mpd, dorsal zone of the medial parvicellular compartment of the PVH; pml, lateral zone of the posterior magnocellular compartment of the PVH. Error bars indicate mean ± SEM; circles represent individual values; N = 5 for each group. Scale bar is 50 μm.