Central administration of leptin to ovariectomized ewes inhibits food intake without affecting the secretion of hormones from the pituitary gland: Evidence for a dissociation of effects on appetite and neuroendocrine function

Abstract

We have studied the effect of leptin on food intake and neuroendocrine function in ovariectomized ewes. Groups (n = 5) received intracerebroventricular infusions of either vehicle or leptin (20μ g/h) for 3 days and were blood sampled over 6 h on days −1, 2, and for 3 h on day 3 relative to the onset of the infusion. The animals were then killed to measure hypothalamic neuropeptide Y expression by in situ hybridization. Plasma samples were assayed for metabolic parameters and pituitary hormones. Food intake was reduced by leptin, but did not change in controls. Leptin treatment elevated plasma lactate and nonesterified fatty acids, but did not affect glucose or insulin levels, indicating a st..