Oxytocin (OXT), a neuropeptide synthesized in the paraventricular nucleus (PVN) of the hypothalamus, functions to increase the precedence of social stimuli and promote the development of a wide range of social behaviors. However, whether OXT has a predicting role in social reward has yet to be examined. In this study, we developed a genetically encoded, scalable OXT sensor named OXTR-iTango2 and applied this technique to define the role of OXT in learned social behaviors. OXTR-iTango2 enables the combination of light- and ligand- dependent gene expression both in vitro and in vivo neural systems. In order to study the predictive role of OXT during expected socially rewarding experiences, we first conditioned animals to a social environment, and then selectively labeled OXT-sensitive ventral tegmental area dopamine (VTA-DA) neurons when animals encountered a conditioned stimulus that stood to predict a familiar social reward. Recurrent exposure to the same social stimulus normally lowered the degree of social interaction, but this reduced interaction was not observed when OXT-sensitive DA neurons were optogenetically inhibited. Thus, our findings support the notion that OXT plays a role beyond promoting social interactions, leading for a new proposed hypothesis that OXT mediation also leads to active avoidance of mundane social interactions. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2020. / FAU Electronic Theses and Dissertations Collection

Exogenous oxytocin aids in the transcervical passage of an AI pipette into the uterus of ewes, and it may be an effective adjunct to sheep AI procedures. Experiments were conducted to evaluate the effects of oxytocin on variables that may affect fertility. The results of this study indicate clearly that oxytocin dilates the cervix in ewes (Exp. 1) without affecting the movement of sperm to the oviducts (Exp. 3) or fertilization rate (Exp. 9). Oxytocin probably binds to uterine and cervical receptors (Exp. 6) and stimulates uterine tetany (Exp. 2) and prostaglandin release (Exp. 5). Because of the irregular arrangement of smooth muscle in the sheep cervix (Exp. 4), uterine tetany may physically dilate the cervix. Also, prostaglandin synthesis, primarily PGF2, may be involved in a chemical softening of the cervix. Most likely, a combination of uterine contractions and cervical softening allow dilation and transcervical passage of an AI pipette. Although oxytocin does not affect sperm transport (Exp. 3) or fertilization (Exp. 9), fertility after transcervical AI is decreased (Exp. 8). Cervical manipulation seems to decrease fertility, but the mechanism is unclear. Therefore, a greater understanding of the physiology of the sheep cervix is necessary before oxytocin-induced cervical dilation can be implemented with nonsurgical AI procedures in sheep. / Ph. D.

The present study was designed to measure levels of oxytocic activity in the blood of cows before, during, and after physical stimulation to the teats and udder. It was also designed to determine the relationship between these levels and intramammary pressure. Knowledge in both these areas has been lacking up to the present. Some information in these areas was obtained as a result of this study. It was found that a wide variation existed in the levels of oxytocic activity between cows. In most cows, a bulk of oxytocic activity was detected in the interval of one to four minutes after stimulation began. The activity rapidly declined to low levels, with some exceptions, between the third and fourth minute post-stimulation. This information indicates that no specific changes need to be made in the present milking procedures. / Master of Science

The 1980's heralded the discovery and identification of extra-pituitary sources of the neurohypophysial hormone oxytocin in non-neural tissues of several animal species. The presence, location and biosynthesis of significant amounts of oxytocin in the ovarian corpus luteum was followed by the immunocytochemical demonstration of an oxytocin-like peptide in the testicular interstitial cells. Leydig cells, which comprise up to 80% of the testicular intertubular cell population, are known to synthesize testosterone in situ. Indirect evidence indicated that an oxytocin-like peptide was also present in Leydig cells. The question arose whether this peptide was synthesized de novo by Leydig cells or was taken up and stored by the cells following biosynthesis at some other intra- and/or extra-gonadal source(s). Since luteinizing hormone (LH) and ascorbate are known to augment the production of oxytocin in ovarian granulosa cells, varying concentrations of these two stimulants were used to monitor the biosynthesis of oxytocin from isolated Leydig cells in culture. / Ph. D.