Central Administration of Neuropeptide Y (NPY) and Vasotocin 4 Receptor (VT4R/V1aR) Antagonists on Food Intake and a Stress Response in Chicks

The objective of this study was to determine the central effect of the VT4R antagonists (SR-49059 and H-5350 (Manning compound)) on corticosterone (CORT) levels during stress and food intake. A 22-gauge stainless steel guide cannula was surgically implanted into the lateral ventricle of the birds. A preliminary study was done to test the antagonists and their role on food intake. Birds were injected with saline, NPY (4μg), NPY (4μg)+SR-49059 (250ng), or NPY (4μg)+Manning compound (250ng). Birds injected with saline had the lowest 1h food intake (17.7g±1.6). Birds injected with NPY+saline had a significantly higher intake (27.1g± 1.0), which was enhanced when birds were injected with NPY+SR-49059 (44.6g±2.6) or with NPY+ Manning (35.9±2.8) compound. These findings were followed up with an acute immobilization stress study. Before immobilization, birds were injected with saline, SR-49059 (250ng), or Manning compound (250ng). Acute stress included wrapping the birds in a harness and leaving them in an unfamiliar cage for 30 minutes. The treatments included no stress, stress, stress+SR-49059, stress+Manning compound. Sample size ranged from 5 to 8 birds per treatment. Blood samples were collected and plasma quantified for CORT by RIA. Results showed that the two antagonists + stress significantly lowered CORT levels when compared to the stress group (p<0.05). A third study was conducted to determine the role of the antagonists alone on food intake. The antagonists increased food intake compared to the control (saline) birds, but did not increase food intake more than birds injected with the antagonist+NPY (p<0.05). In summary, there appears to be an interaction between NPY induced food intake and the vasotocinergic system on the feeding response in birds. The two antagonists have a greater than additive effect on food intake when given with NPY. Acknowledgments I owe many thanks to my advisors, Dr. Wayne J. Kuenzel and Dr. Seong W. Kang for supporting me throughout my study. They have provided me with knowledge, training, and encouragement, and were always willing to help when needed at the farm. My colleagues, Gurueswar and Aman, have continually given up their time to help me with my data collection. I would not have been able to complete my work without them. Lastly, I would like to thank my family and friends who have helped me and encouraged me along the way, and God for allowing me this opportunity. Dedication I would like to dedicate this thesis to my parents. They are the strongest, hardest working people I know. They have always been my heroes and the most influential people in my life. Table of