Date of Graduation

5-2017

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Poultry Science (PhD)

Degree Level

Graduate

Department

Poultry Science

Advisor

Wayne J. Kuenzel

Committee Member

Walter G. Bottje

Second Committee Member

Suresh K. Thallapuranam

Third Committee Member

Sami Dridi

Fourth Committee Member

Byung-Whi Kong

Abstract

It is well known that arginine vasotocin (AVT) in birds is involved in physiological homeostasis such as cardiovascular, osmotic regulation as well as reproductive functions. Pertinent to these physiological functions, AVT immunoreactive (-ir) neurons in the hypothalamus have been found associated with hemorrhage, dehydration, oviposition and other physiological regulation. Evidence, however, suggests that AVT also plays significant roles in modulating behavior, memory, stress, and food intake. This dissertation research addresses the latter two neuroendocrine functions of AVT in detail within the chicken brain. First, the functional role of AVT-ir neurons in conjunction with corticotropin releasing hormone (CRH)-ir neurons in the neuroendocrine regulation of stress is elucidated in meat type chickens. The results from research showed that a distinct type of AVT neurons (parvocellular - small sized) in the paraventricular nucleus (PVN) of the hypothalamus is activated in response to acute and chronic stress. Furthermore, in order to facilitate the neuroendocrine regulation of stress in chickens, expression of AVT in the PVN occurs in the latter phase of the stress period compared to earlier activity of CRH when birds are exposed to a stressor. Second, the neuromodulatory role of AVT to activate CRH neurons via vasotocin receptors (V1aR) within the avian brain is addressed. The results suggests that AVT could augment stress response by modulating CRH neuronal activity in a septal nucleus called the nucleus of the hippocampal commissure (NHpC). Third, the functional role of AVT via the V1aR in food intake regulation is characterized. Results show the association of AVT neurons (magnocellular – large sized), in the preoptic and hypothalamic brain structures, and CRH neurons, in the NHpC, following food intake in chickens. Hence, neuroendocrine regulations of AVT neurons in distinct brain structures in the stress response and food intake in chickens are characterized by this dissertation research.

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