Abstract

The disruption of daily rhythms in physiology is a widespread concern in modern society and affects individuals across the entire population. Repeated rhythm disruption has detrimental effects on health and is known to be a risk factor for the development of mental conditions, including alcohol abuse and mood disorders. This results in an intricate clinical picture, as affective disorders are often comorbid with pathological alcohol consumption. Furthermore, affective behavior may also induce alcohol consumption or relapse, and both factors can affect daily rhythms in physiology, which may exacerbate the conditions ultimately. While there is accumulating evidence on the negative consequences of circadian disruption in males, knowledge in females is limited. This project aims to bridge this gap by investigating the association between circadian desynchronization and alcohol consumption, focusing on behavior and physiology in female rats.
To model environmentally-induced circadian disruption, we exposed female rats to either a short-day light cycle or repeated shifts of the light/dark cycle and investigated alcohol drinking behavior, mood-related behavioral changes, and physiology to study the effect of chronodisruption. Moreover, we analyzed changes in gene expression in brain regions associated with the reward system following circadian disruption and alcohol consumption to understand the underlying mechanism of displayed behaviors.
The results demonstrate that exposure to aberrant light conditions disrupts the circadian system and impairs physiological processes such as the estrous cycle. Strikingly, the sole effects of the light conditions on mood-related behavior and alcohol consumption were minor, despite changes in gene expression in the brain regions related to reward processing. However, chronodisrupted females displayed changes in mood-related behavior under alcohol abstinence, indicating that the combined impact of circadian desynchrony and stressors like abstinence are risk factors in the development of mental conditions, that may affect drinking behavior or relapse subsequently.
The outcomes of this thesis expand our understanding of the effects of chronodisruption in females and establish a foundation to further explore the complex relationship between circadian disruption, alcohol consumption, and their effects on mental health. This knowledge can guide future studies and interventions targeting mood disorders and alcohol misuse in females, especially in the context of shiftwork.