Mammalian and avian species differ in some appetite-related aspects including how and which neurotransmitters and hormones regulate appetite. The objective of this research was to determine how two satiety-inducing neuropeptides regulate feeding behavior in avian models. Neuropeptide FF (NPFF) was intracerebroventricularly (ICV) injected into Japanese quail and decreased food intake at a dose of 32 nmol. NPFF-injected quail had increased expression levels of hypothalamic melanocortin subtype 3 receptor and decreased expression levels of neuropeptide Y receptor subtype 1 mRNAs compared to vehicle-injected controls. In a second study, gastrin was ICV injected into broiler chicks and decreased food intake at a dose of 500 ng (0.12 nmol). There was increased c-Fos immunoreactivity in the lateral hypothalamus (LH), paraventricular nucleus (PVN), arcuate nucleus, nucleus of the solitary tract, and area postrema at 1 h post-injection. Although a variety of genes were measured in those activated nuclei, there were only differences in melanin-concentrating hormone mRNA in the LH and corticotropin-releasing factor (CRF) mRNA in the PVN, suggesting that CRF signaling was involved in the hypothalamic response to gastrin. However, co-injection of gastrin and astressin, a CRF receptor antagonist did not affect gastrin-induced suppression of food intake, implying that the CRF receptors may not be directly associated with gastrin-induced satiety. Identifying the molecular pathways that mediate the effects of anorexigenic neuropeptides in birds will lead to the development of novel treatment options for appetite-related diseases and increased understanding of factors that affect production efficiency in commercial poultry and survival/resource allocation in wild birds. / Master of Science / Compulsive eating behavior associated with obesity, and anorexia nervosa, are appetite-related disorders for which no effective pharmacological treatment options exist. From an agricultural perspective, understanding what drives eating behavior is important for informing management decisions that affect animal health and welfare. From an evolutionary point of view, understanding the neural mechanisms of appetite in different species is important because of the necessity of appetite for survival. This thesis research focused on elucidating the central mechanisms associated with the actions of two neuropeptides that inhibit food intake. In the first experiment, we explored the mechanisms underlying the appetite suppressive effects of neuropeptide FF (NPFF), a neuropeptide known for its morphine-modulating properties, and found that it decreased food intake in Japanese quail, a bird that is more representative of a bird in the wild than the chicken. NPFF affected the gene expression of several appetite-related factors in the hypothalamus, a region of the brain that regulates appetite, providing insights on the associated molecular pathways. In the next study, we examined the effect of gastrin, a digestive hormone known for its role in regulating gastric acid secretion, in broiler chicks. Broiler chickens are meat-type chickens genetically selected for growth and meat production. Gastrin significantly decreased food intake in broiler chicks, and this was associated with changes in the gene expression of melanin-concentrating hormone and corticotropin-releasing factor in the lateral hypothalamus and paraventricular nucleus of the hypothalamus, respectively. Overall, we were able to provide novel insights regarding the hypothalamic mechanisms that regulate the inhibition of food consumption. These findings may lead to the development of a novel appetite suppressant or stimulant to adjust food consumption in individuals with eating disorders and chickens during specific stages of growth.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/83786 |
| Date | 26 June 2018 |
| Creators | Logan, Amanda Lynn |
| Contributors | Animal and Poultry Sciences, Cline, Mark A., Denbow, D. Michael, Gilbert, Elizabeth R., Liu, Dongmin |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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