The biological background for stress-induced depressive states

Physiological and behavioural responses to stress and environmental change are individually variable traits, which manifest phenotypically and are subject to natural selection as correlated trait-clusters (so called coping styles, or personality traits). Comparative research has revealed a range of physiological-behavioural associations which are conserved throughout the vertebrate subphylum. Regulatory mechanisms universally mediate a switch between proactive (active / aggressive) and reactive (conservation/withdrawal) behaviour in response to unpredictable and uncontrollable events. Thresholds for switching from active coping to behavioural inhibition are individually variable, and depend on experience and genetic factors. Such factors affect physiological stress responses as well as perception, learning, and memory about external events. This project involves research on an important contributor to neural processing, the set of biochemical, molecular, and structural processes collectively referred to as neural plasticity. We will continue our work in teleost fishes, while also elucidating conserved aspects between fishes and mammals.  In fishes, environmental and physiological control of brain cell proliferation and neurogenesis has received recent attention. This work has revealed that the expression of genes involved in CNS plasticity is affected by heritable variation in stress coping style, and is also differentially affected by short- and long-term stress. Chronic stress experienced by subordinate fishes in social hierarchies leads to a marked suppression of brain cell proliferation. To understand the molecular biology behind such environmental control of brain structural plasticity, we will study the transcription of neurogenesis related genes in chronically stressed zebrafish (Danio rerio), rainbow trout (Oncorhynchus mykiss) or Atlantic salmon (Salmo salar). The potential for these findings to illuminate stress-related neurobiological disorders in other vertebrates will be a central theme in a MSc thesis from the project. The project is supervised by the IBV programme for physiology and neurobiology, professor G?ran Nilsson and Dr. ?yvind ?verli.