Figure 2.

The rate of leptin appearance in the brain is normal in leptin resistant mice. Mice with implanted cOFM probes (see methods) were fed either chow or HFD for 20 days before leptin transport into the brain was assessed (A). Prior to the intraperitoneal injection of recombinant leptin, mixed tail blood was collected to determine baseline plasma leptin levels (B). Leptin concentrations were then determined in either plasma (C) or interstitial fluid collected from the brain (E) at indicated time-points. Corresponding area under the curves (AUCs) were calculated (D,F). Data are means ± SEM and n = 10 for all groups. Data in panel B, D and E were analyzed with a two-tailed Student's t-test; data in panel C and E were analyzed by two-way repeated measures analysis of variance and a Holm-Sidak post-hoc test was performed for the variable ‘time’. *p < 0.05, ***p < 0.001 compared to 0 min ^#p < 0.05 compared to chow.