By Hudson McNerney

Faculty Mentor: Dr. Parrish Waters

Abstract

THE EFFECT OF SOCIAL ISOLATION ON OREXIN PRODUCTION AND HEDONIC DRIVE IN FEMALE MICE. Hudson McNerney, Dr. R. Parrish Waters, Dept. of Biol., University of Mary Washington. Social stress is a primary instigator of psychological disorders in humans. While social stress results from social dominance relationship (i.e., being subordinate), social isolation is an intense psychosocial stressor for social organisms (including mice and humans) that can have profound effects on physiological and neurobiological systems. One of these negative effects is a loss of feelings of reward, or anhedonia. Rewarding feeling in response to positive stimuli, or ‘hedonic drive’ is largely controlled by orexins. Two neuropeptides, orexin A and orexin B, are produced in the lateral hypothalamus, and can be disturbed by intense or chronic stress. The aim of this work was to investigate the relationship between the behavioral alterations and orexin production induced by chronic social isolation stress in adult female mice. Socially isolated (SI) mice showed reduced appetitive behavior towards palatable food in the conditioned place preference (CPP) test compared to group-housed (GH) mice. SI mice exhibited a reduced plasma corticosterone level of 1.63 ng/ml compared to the GH mice with a corticosterone level of 6.14 ng/ml (p<0.01). Finally, SI mice exhibited a decreased orexin production level compared to GH mice (374.59 pg/ml & 643.92 pg/ml, respectively. p<0.01). Altogether, these results suggest that decreased hedonic behavior induced by social isolation stress correlates with decreased corticosterone and reduction of orexin in the perifornical area of the lateral hypothalamus of female mice. Author contact: Hmcnerne@mail.umw.edu