Molecular mechanisms of brain-ras hyperactivity upon fluid balance, and sufficiency of angiotensin production from the subfornical organ to affect fluid balance

has been approved by the Examining Committee for the thesis requirement for the Doctor of Philosophy degree in Pharmacology at the May 2015 graduation. ii ACKNOWLEDGMENTS I would like to acknowledge my mentor, Dr. Curt Sigmund, for given the opportunity to develop myself as a scientist, and for supplying me with the appropriate guidance. I would like to acknowledge, Dr. Justin Grobe, for also guiding me on my path of training. I would also like to acknowledge the University of Iowa Medical Scientist Training Program for believing in me to become a physician-scientist. Finally, I would like to acknowledge my parents, Laura and Paul Coble, for their unbound love and support. iii ABSTRACT Fluid balance is critical for cells to maintain at homeostasis as disturbances in it can disrupt cell function and consequently the physiology of an organism. Fluid loss for an organism can be classified as either intra-or extracellular, and it appears that different mechanisms have developed to restore homeostasis after intra-or extracellular dehydration. The renin-angiotensin system (RAS) has been shown to be an important mediator of extracellular dehydration induced fluid intake. Various lines of evidence have demonstrated the importance of the subfornical organ (SFO) to mediate fluid intake, especially due to the RAS, and we have shown that production and action of angiotensin (ANG) at the SFO is necessary for fluid intake due to ANG within the brain. PKC, specifically PKC-α, is demonstrated here to be a necessary and sufficient effector in the SFO to mediate brain ANG polydipsia. Production of ANG from the SFO is also shown to be sufficient to increase fluid intake through the angiotensin-II type 1 (AT 1 R) receptor and PKC. While production of ANG from the SFO is sufficient to increase fluid intake it is not sufficient to increase blood pressure or sodium appetite. Thus, production and action of ANG to activate PKC-α is both necessary and sufficient to increase fluid intake, and the fluid and pressor phenotypes of brain ANG through the SFO can be separated. vi LIST OF TABLES Table 3.1: Serum chemistry of littermate control (n=5) and sRA Red (n=6) 32-days after ICV injection of AdCRE…………………………………………………. 62 Table 3.2: Metabolism as measured by indirect calorimetry in littermate control (n=6) and sRA Red mice (n=6) 68-days after ICV injection of Figure 1.1: The core of the SFO is highly vascularized and lacks a BBB. It mainly affects sympathetic nerve activity …