![]() Chronic exposure to this kind of stress profoundly alters the motivation for social interactions in rodents and also leads to short- and long-term behavioral and physiological changes, such as decreased locomotion and exploratory activity, in addition to increased emotionality. Indeed, SD stress does not result in habituation upon repeated presentations, providing an ethologically and ecologically relevant form of persistent emotional distress. In particular, it has been proposed that, compared to models based on physical stressors, social defeat (SD) stress, which (in mice and rats) is based on the experimental induction of social conflicts through repeated exposures to a larger, dominant, conspecific might represent a reliable paradigm to model stress-induced human psychopathological traits. By contrast, social stressors are effective in triggering powerful physiological and, more importantly, emotional responses both in humans and in social animals such as rats and mice also leading to avoidance/withdrawal, a behavioral trait which is common in several human affective disorders including depression, social phobia and also PTSD. However, as many authors have pointed out, most of these stressful challenges used in the laboratory setting are not so relevant to situations that humans encounter in their everyday life, likewise they hardly resemble those usually faced by rodents in a natural context. In an attempt to model pathologies associated with stress, powerful stressors such as cold, electric foot-shock, forced swimming, restraint and chronic unpredictable stress are commonly used. In addition, they indicate that variations in the nociceptive threshold might represent a physiological marker of both short- and long-term effects of stress.Īnimal models represent a key heuristic approach to identifying reliable markers and pathophysiological aspects of stress-related diseases, such as generalized anxiety, major depression, post-traumatic stress disorder (PTSD) and schizophrenia. These data indicate that the SD paradigm is able to induce emotional changes associated with a stressful/traumatic event. ![]() Moreover, an increase in nociceptive threshold (stress-induced analgesia) was found both in the short-term and 4 weeks after the end of stress. SD subjects were characterized by increased corticosterone levels (30 min following stress exposure), increased latency to approach the social target in the short-term as well as increased emotionality in the long-term. Social avoidance and pain threshold were assessed 24 h and 4 weeks after the end of SD stress, while corticosterone was assayed at the beginning and at the end of the stressful procedure (days 1 and 10). To this end, 3-month-old C57BL/6J male mice were exposed to social defeat (SD) stress for 10 days as this stressor shows good face and predictive validity for several models of human affective disorders including depression, social phobia and post-traumatic stress disorder. Animal models with an eco-ethological relevance can help in identifying novel and reliable stress-related markers.
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