Fig. 4.

Effect of chronic icv leptin infusion on food intake, body weight, and hypothalamic PTP1B mRNA expression. Two separate experiments were conducted to assess and replicate the effects of icv leptin infusion on hypothalamic PTP1B mRNA expression. In the first (A–C), rats bearing icv cannulas were infused with leptin (3 μg/day) or saline for 14 days. Daily food intake (A) and body weight (B) were assessed throughout the study, and on days 4 and 14 of infusion, as well as on day 19 (5 days following the cessation of infusion), subgroups of animals (6–8 rats/group) were killed, and levels of PTP1B mRNA expression were determined via real-time PCR. Leptin infusion significantly decreased both food intake and body weight compared with saline-infused controls (P < 0.01). Leptin infusion also increased levels of hypothalamic PTP1B mRNA on day 14 (P = 0.02) but had no effect on PTP1B mRNA either on days 4 or 19 (P > 0.05). A second experiment (D–F) was conducted as above, except rats were infused with leptin (3 μg/day) or saline for 10 days (5 rats/group) and killed on day 10, and levels of PTP1B mRNA in the mediobasal hypothalamus were determined via real-time PCR. Again chronic icv leptin infusion significantly suppressed food intake and body weight (P = 0.003), and PTP1B mRNA levels were significantly higher in leptin-infused rats compared with controls (P = 0.01).