Table 2.

Serum leptin levels in young and aged rats on a chow diet after 7-day saline or leptin infusion

Dose (mg/day)	Young Rats	Aged Rats
Control	6.91±1.12	13.25±2.00
0.03	10.10±0.47
0.05	14.05±0.86*	19.56±1.34
0.07	19.75±1.38*
0.1	20.16±1.08*	25.38±2.86†
0.5	22.23±2.15*	24.62±2.26†

Values are means ± SE in ng/ml; n = 7–9 rats/group. Young rats: P < 0.0001 for the difference with leptin infusion.

^*P < 0.01 for the increase in serum leptin levels compared with controls. Aged rats: P = 0.0008 for the difference with leptin infusion.

^†P < 0.01 for the increase in serum leptin levels compared with control values by post hoc analysis.