Date of Graduation

12-2014

Document Type

Thesis

Degree Name

Master of Science in Cell & Molecular Biology (MS)

Degree Level

Graduate

Department

Biological Sciences

Advisor/Mentor

Wayne J. Kuenzel

Committee Member

Suresh K. Thallapuranam

Second Committee Member

Mack Ivey

Third Committee Member

Andy Mauromoustakos

Fourth Committee Member

Seong Kang

Keywords

Organum vasculosum of lamina terminalis, Subfornical organ, Vasopressin receptor

Abstract

Past studies have shown that the avian vasotocin 4 receptor (VT4R), homologous to the mammalian arginine vasopressin receptor 1a (V1aR/AVPR1A) is involved in immobilization stress. It was not known, however, whether the receptor is also associated with osmotic stress, and if so, what brain regions may be involved. Four treatment groups of chicks were used for the study. One group was subjected to 1h immobilization stress and two groups were administered intraperitoneal injection of 3 M NaCl or 0.15 M NaCl. One additional group served as controls. After 1 h, blood samples were taken for the determination of plasma levels of arginine vasotocin and corticosterone by radioimmunoassay. Chick brains were sampled for immunohistochemistry utilizing an antibody, anti-VT4R, and for real time RT-PCR. Plasma corticosterone (CORT) concentrations were significantly increased in the immobilized group (p < 0.01) and hypertonic saline group (p < 0.01) compared with controls. Plasma arginine vasotocin (AVT) concentrations were significantly increased (p < 0.01) in hypertonic saline birds and immobilized birds compared with controls. Intense staining of the VT4R in the organum vasculosum of the lamina terminalis (OVLT) and subseptal organ (SSO) of both treatment groups showed marked morphological changes compared to controls. AT1AR mRNA, TRPV1 mRNA, and VT4R mRNA levels were increased in SSO in hypertonic saline birds, while these genes were increased in OVLT in acute immobilization stressed birds. The CRH-R1 mRNA genes were decreased in hypertonic saline birds, while increased in acute immobilization stressed birds. These results strongly suggest that physical stress affect the vasotocinergic system in the SSO to regulate the water balance through VT4R, while psychogenic stress causes change in VT4R expressed in the OVLT for the classical activation of the HPA. Taken together, results provide evidence that both osmotic challenge and psychological stress affect the vasotocinergic system via the VT4R in two avian sensory circumventricular organs.

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