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Title: THE ROLE OF NEUROPEPTIDE Y AND INTERACTION WITH LEPTIN IN REGULATING FEED INTAKE AND LUTEINIZING HORMONE AND GROWTH HORMONE SECRETION IN THE PIG

Author
item Barb, Claude
item Kraeling, Robert
item RAMPACEK, GEORGE - UNIVERSITY OF GEORGIA
item Hausman, Gary

Submitted to: Reproduction
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/9/2006
Publication Date: 6/20/2006
Citation: Barb, C.R., Kraeling, R.R., Rampacek, G.B., Hausman, G.J. 2006. The role of neuropeptide y and interaction with leptin in regulating feed intake and luteinizing hormone and growth hormone secretion in the pig. Reproduction. 131:1127-1135.

Interpretive Summary: Inadequate nutrition is characterized by low blood levels of pituitary hormones, such as luteinizing hormone (LH), necessary for stimulation of the reproductive system and growth hormone (GH), necessary for growth. A lack of these hormones results in delayed puberty, irregular heat cycles and failure of animals to breed and poor growth. The brain peptide, neuropeptide Y(NPY), produced by the brain in response to changes in body weight or energy, stimulates feed intake, and suppresses LH secretion in rodents. NPY may serve as a signal linking the body's energy regulating system with the reproductive and growth system. This is the first report to demonstrate that administration of NPY suppressed LH and stimulated GH secretion, feed intake and suppressed GH response to GH releasing hormone (GHRH, brain hormone that stimulates GH secretion)) from pig pituitary cells in culture. Therefore, understanding the NPY- LH/GH and appetite interactions is necessary in order to develop new methods to improve reproductive efficiency and growth in the pig.

Technical Abstract: In experiment I (EXP), prepuberal gilts received intracerebroventricular (ICV) neuropeptide Y(NPY) injections. Blood was collected 3h before and 4h after ICV inj. of .9% saline (S; n=8), 10 ug (n=9), 50 ug (n=7) or 100 ug (n=7) of NPY in S. EXP II, prepuberal gilts recived ICV injections of 150 µl 0.9% S (n = 4)), or 50 µg of leptin (n = 4), 100 µg NPY (n = 4) or 100 µg NPY + 50 µg leptin (n = 4) in 150 µl of S. Blood samples were collected every 15 min for 4 h before and 4 h after ICV injections and feed intake measured. EXP III, pituitary cells in culture were challenged with 1 nM, 10 nM, or 100 nM, gonadotropin releasing hormone (GnRH), 100 pm, 10 nM or1 uM growth hormone releasing hormone (GHRH) or 1 nM, 10 nM, 100 nM, or 1 uM, NPY individually or in combinations with 1nM and 10 nM GnRH or 10nM and 1 uM GHRH. LH and GH were measured at 4 h. In EXP I, the 50 ug and 100 ug dose of NPY suppressed LH and increased GH secretion. In EXP II, NPY blocked the leptin-induced suppression of feed intake, suppressed LH secretion but failed to effect GH secretion. In EXP III, 1 uM and 100 n M NPY increased basal GH secretion. Addition of 1, and 10 nM NPY in combination with 10 nM GHRH suppressed GHRH-stimulated GH secretion. NPY failed to effect LH secretion. These results indicate that NPY modulated LH, GH secretion and feed intake at the brain and directly modulates GH secretion from the pituitary gland.