�VERLI, �*; POTTINGER, TG; WINBERG, S: Effects of Selection for Stress Responsiveness on Behaviour and Brain Monoamines in Rainbow Trout

Recent studies in mammals suggest that differences in behavioural stress responses are associated with consistent neuroendocrine and physiological traits, which result in individual stress coping strategies, or coping styles. We present evidence suggesting that differential stress coping styles also have evolved in teleost fish. Two F1 lines of rainbow trout divergent for hypothalamus-pituitary-interrenal axis responsiveness were generated by individual selection for post stress cortisol values within the F0 generation. High-responsive (HR) fish displayed higher levels of locomotor activity than low-responsive (LR) fish in the presence of a territorial intruder, but not when in isolation. A significantly higher incidence of feed intake was seen in LR trout when held in observation tanks, suggesting that these fish acclimated more successfully to the experimental conditions than HR fish did. HR fish also reacted to stress by an increase in the concentrations of both serotonin (brain stem), dopamine (brain stem), and norepinephrine (optic tectum, telencephalon), whereas low-responsive fish did not. Brain stem and optic tectum concentrations of monoamine metabolites were also elevated after stress in HR, but not in LR fish. These results suggest that alterations in brain monamine neurotransmitter systems are involved in shaping the differential behavioural and neuroendocrine profile of HR and LR trout.