Rodents present anticipatory thirst activity that precedes their inactive phase, which is attributable to circadian mechanisms in thirst regulation. The subfornical organ (SFO) is a sensory circumventricular organ with important roles in osmoregulation and thirst. The SFO expresses core circadian clock genes rhythmically, suggesting its involvement in circadian control of thirst and fluid balance. Nevertheless, daily changes in the expression of other genes implicated in thirst and non-fluid balance related functions within the SFO has not yet been extensively investigated. This study assesses potential daily variation in molecular programs by examining gene expression in the SFO using both in vivo and ex vivo methods. Specifically, gene expression is compared at four time points across 24h to investigate potential daily variations. Moreover, at the beginning of the active phase, the impact of a 5h water restriction on SFO gene expression is examined to understand how hydration levels influence its pattern. RNAscope in situ hybridization is used to visualise spatial distribution of clock gene expression as well as transcripts associated with drinking behaviour over 24h. The robustness of the circadian clock within the SFO is further investigated using a bioluminescent gene reporter, enabling the real-time monitoring of the molecular clock over a week, in isolation from the primary circadian clock in the suprachiasmatic nucleus which synchronizes peripheral clocks. Overall, this study aims to provide an analysis of daily variation in the expression of specific gene targets in the SFO, enabling a better understanding of how the brain co-ordinates thirst and drinking behaviour over the 24h cycle.
Daily patterning of gene expression in the subfornical organ and its modulation by thirst
Veneri, I. (Author). 18 Mar 2025
Student thesis: Master's Thesis › Master of Science by Research (MScR)