Sex, Fat and the Tilt of the Earth: effects of sex and season on the feeding response to centrally administered leptin in sheep.

Whilst there have been many studies in various species examining the effect s of leptin on food intake, there is a paucity of data comparing responsive ness in the two sexes. We have, therefore, addressed this issue in sheep. B ecause this species shows seasonal variation in voluntary food intake (VFI) , we also considered the possibility that there might be seasonal variation in the responsivity to leptin. Centrally administered leptin was relativel y ineffective as a satiety factor in either sex during Autumn. In Spring, l eptin had a profound inhibitory effect on VFI in the females, but only a sl ight effect in males. These data indicate that responsiveness to leptin dep ends on sex and also on season in animals that are substantially affected b y photoperiod.