The role of neuropeptide Y and interaction with leptin in regulating feed intake and luteinizing hormone and growth hormone secretion in the pig

Two experiments (EXP) were conducted in ovariectomized prepubertal gilts to test the hypothesis that neuropeptide Y (NPY) stimulates appetite and modulates LH and GH secretion, and that leptin modifies such acute effects of NPY on feeding behavior and LH and GH secretion. In EXP I, gilts received intracerebroventricular (ICV) injections of 0.9% saline (saline; n=6), or 10 mu g (n= 7), 50 mu g (n=5) or 100 mu g (n=7) NPY in saline and blood samples were collected. In EXP II, gilts received ICV injections of S (n=4), or 50 mu g leptin (n=4), or 100 mu g NPY (n=4) or 100 mu g NPY +50 mu g leptin (n=4) in saline, and feed intake was measured at 4, 20 and 44 h after feed presentation and blood samples collected. In EXP I, NPY suppressed LH secretion and the 100 mu g dose stimulated GH secretion. In EXP II, NPY reversed the inhibitory effect of leptin on feed intake and suppressed LH secretion, but serum GH concentrations were unaffected. These results support the hypothesis that NPY modulates feed intake, and LH and GH secretion and may serve as a neural link between metabolic state and the reproductive and growth axis in the pig.