Project Type


Publication Date


Department or Program

Biological Sciences


College of Arts and Sciences

Faculty Mentor #1

Waters, Parrish


Orexin, also referred to as hypocretin, is a peptide produced in the hypothalamus that regulates many physiological and behavioral processes, including sleep, wakefulness, metabolism, thermoregulation, and reward (Chieffi et al., 2017). The multiple mechanisms of orexin stem from the neural circuit or nucleus where it is synthesized or released. Orexin produced in the perifornical and dorsomedial hypothalamus projects to the amygdala, and is most heavily associated with arousal and wakefulness, whereas orexin produced in the lateral hypothalamus (LH) projects to the mesolimbic pathway and is associated with hedonic behavior, as it influences the Ventral Tegmental Area (VTA) and the Nucleus Accumbens (Harris and Aston-Jones, 2006). Orexin influences affective disorders, including anxiety, sleep disorders, and drug addiction. In the last couple of decades, researchers have also identified a critical link between orexin and drug-seeking behavior. While a link between addictive behavior and orexin has been established (James et al., 2017), the role of orexin in modulating more naturalistic behaviors, such as physical exercise, has not yet been explored. Twenty three pair-housed outbred male mice were split into either the control or experimental group who had access to a running wheel under standard environmental conditions for a period of seven weeks. A sucrose preference test of hedonic drive was performed, as well as the conditioned place preference test of hedonic drive using female urine-soaked bedding as a rewarding non-caloric stimulus. Following behavioral testing, mice were sacrificed and the lateral hypothalamus and nucleus accumbens were isolated for RNA extraction in preparation for Taqman qPCR; blood plasma samples were also analyzed in a corticosterone ELISA assay. While there were no significant differences among control and experimental groups in behavioral testing, the physiological data we procure in the last week of classes could dictate whether voluntary physical exercise modulates hypothalamic orexin concentrations in CD1 mice.

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Biology Commons