Date of Award

5-11-2015

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Neuroscience Institute

First Advisor

Walter Wilczynski

Second Advisor

Laura Carruth

Third Advisor

Kim Huhman

Fourth Advisor

Geert de Vries

Abstract

Arginine vasotocin (AVT; or its mammalian homologue arginine vasopressin) is a potent regulator of social behavior in many species. Examining its behavioral and endocrinological effects in different species can provide insight into its general mechanisms in regulating social behavior and physiology. These experiments were aimed at gaining insights into the role of AVT and its interactions with other steroid hormones in the regulation of social behavior including aggression and courtship as well as the effect of aggressive behavior itself on AVT expressing cells in the brains, using the green anole lizard as the research subject. Little is known about the role of AVT in reptilian behavior. First, the effect of exogenous AVT on social behavior (mirror and paired aggression, courtship) and circulating steroids was assessed. I found that AVT increased corticosterone (CORT) in all animals and tended to reduce aggressive behavior as has been reported for other territorial species. AVT did not perceptibly alter male courtship but did increase the display behavior of untreated females paired with treated males. Next, endocrine and behavioral effects of different AVT doses were considered as well as the impact of AVT on steroid hormones in single housed animal. I found that high doses of AVT increased CORT more in aggressing than courting animals although no effects on behavior were observed. I also found that AVT stimulates CORT release in animals without a behavior challenge. Then, I examined the influence of AVT on aggressive behavior in animals with a CORT-synthesis inhibitor to establish a non-stress hormone dependent role for AVT. AVT tended to reduce aggressive behavior even in the presence of a CORT-synthesis inhibitor. Next, AVT immunoreactive cell counts were compared in animals with varying numbers of exposures to an aggression inducing versus neutral stimulus. I found that AVT immunoreactive cell number in the preoptic area (POA) increased in animals with five aggressive exposures. Findings from this dissertation suggest a possible role for AVT in the regulation of aggressive behavior and highlight the importance of considering the glucocorticoid response when considering AVT effects.

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