Stress and Social Behaviour in the Mouse: Experimental Models for Preclinical Psychopharmacology

Over the last two decades, the concept of stress as a non-specific adaptive response of the organism to physical factors 1 has been modified as experimental research has pointed to specific kinds of stress responses and to a role of cognitive factors in determining stress 2 . In the light of these new ideas, stress can be viewed as a possible result of changes in the environment-organism interaction (fig. 1). Even species with very simple behaviour characterized by fixed action patterns, must retain some ability to adapt to changes in the environment in order to survive. An organism can be viewed, in fact, as an open system constantly interacting with its environment such that changes in the environment necessarily bring about changes in the organism 3 . When the environment is modified, the organism detects discrepancies between observed and expected events and attempts to restore the expected situation. This phase is characterized by a particular picture of physiological changes commonly termed arousal 4. If attempts to restore the expected situation fail, given the characteristics of the environment, the organism undergoes a crisis we call stress. This crisis produces a number of significant alterations in the organism’s functioning which lead either to a new equilibrium between the organism and the environment or to pathology. The stress response may Involve different physiologial systems depending on the characteristics of the stressor, on genetic make up and on the history of the individual (i.e. previous stressful experiences).