Fig. 3

Response to leptin and to the change of food from OC to the HFD in the rats fed OC or HFD. After 104 days fed on the HFD, the anorexigenic effect of leptin was tested by injecting 20 μg of leptin or 5 μl of saline into a lateral cerebral ventricle of in the OC (n = 8, respectively) and the HFD (n = 8, respectively) rats (a food intake, b body weight change). The HFD rats were tested again after their food was returned to the OC for 10 days (HFD + OC group). Only OC rats showed leptin sensitivity and HFD rats and HDF + OC rats were insensitive to leptin. Values are mean ± SEM. *P < 0.05, between leptin and saline injection. Changes in food intake after food was switched from ordinary chow (OC) to the high-fat diet (HFD) in leptin-resistant and leptin-responsive rats (c). Rats were made leptin-resistant by HFD feeding for 104 days; these rats were then fed OC for 10 days, then HFD was returned on day −1 (n = 8). The leptin-resistant and leptin-sensitive rats showed similar patterns of food intake responses to the HFD. Values are mean ± SEM. *P < 0.05, between −1 and 1 day values in both leptin-resistant and leptin-sensitive rats