Behavioural, neurochemical and neuroendocrine effects of predator stress in mice
b'Stress plays a role in the etiology of anxiety and mood disorders. To investigate these disorders, animal models are used, many of which incorporate a stressful stimulus. Especially psychological stressors may resemble stressful situations that in humans can lead to pathology. The study, described in this thesis, was undertaken to elucidate the effects the psychological stressor predator exposure has on behaviour, on neurochemical parameters in various brain regions and on neuroendocrine parameters in mice. Therefore mice of several strains were exposed to a rat. Also the effects of repeated predator exposure were assessed. Rat exposure lead to risk assessment behaviour, followed by coping strategies. Extracellular levels of serotonin and its metabolite were higher than baseline levels in the hippocampus, prefrontal cortex, lateral septum, but not in the caudate putamen. Also the levels of noradrenaline were clearly increased in the hippocampus. Plasma concentrations of ACTH and corticosterone were mildly elevated in three out of five examined strains. These strains also exhibited a slightly different behavioural profile. With re-exposure, less risk assessment took place, levels of free corticosterone were lower, but hardly any differences in neurochemical parameters were seen. Taken together, behavioural, neurochemical and neuroendocrine parameters form a complimentary picture indicating that rat exposure in its current form had mild arousing properties. Also in this mild form predator exposure elicited a selective activation of brain regions and neurochemicals. This highly differentiated response may be of utmost importance to coordinate and to fine-tune the specific neuroendocrine, behavioural and autonomic responses to this form of stress. It might be worthwhile to increase the stressful properties of the paradigm to further look into these mechanisms.'