Animal Models (Nonprimate) for Human Stress1

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An organism undergoes a series of physiological changes when exposed to a stressor. In the short term, several brain centers can be activated, including, among others, the locus coeruleus in the brain stem, the paraventricular nucleus in the hypothalamus, and amygdala and hippocampus in the limbic system. The activation of these centers leads to increased sympathetic nervous system (SNS) activity and elevated hypothalamic-pituitary-adrenocortical (HPA) axis hormones. These responses are homeostatic mechanisms that allow an individual to cope with a stressor and eventually turn off the stress response through negative feedback. However, if people are exposed to a very severe or prolonged stressor, more persistent changes characteristic of posttraumatic stress disorder or a general stress reaction can become established. Animal models of stress have been used to study these and other facets of acute and chronic stress responses.