The anorectic effect of oestradiol does not involve changes in plasma and cerebrospinal fluid leptin concentrations in the rat

Oestradiol is a potent anorectic agent that reduces both food intake and bo dy weight. Since leptin is known to reduce food intake, we first analysed i f the anorectic effect of oestradiol is driven by an increased leptin conce ntration in either cerebrospinal fluid or plasma. Oestradiol also reduces b ody weight and fat mass. Accordingly, a decrease in plasma leptin concentra tion can also be expected after an oestradiol-driven reduction in fat mass. To test this hypothesis was the second aim of this study. Female Wistar ra ts received oestradiol chronically during 14 days. During the first week of treatment there was a reduction in food intake, body weight and fat mass t hat returned to initial values during the second week, but no changes in ob mRNA levels were found in white adipose tissue depots. There was no effect of treatment or tit ne on plasma and cerebrospinal fluid leptin concentrat ions. Therefore, the anorectic effect of oestradiol is not driven by an inc rease in leptin concentration either in plasma or in cerebrospinal fluid, a nd the reduction in fat mass that oestradiol produces is not followed by a reduction leptin concentration.