These behaviors depend on the context and the repertoire of the species. Active coping strategies are used when escape from threat is possible, and the autonomic changes associated with these active strategies are mediated predominantly by sympathetic activation (selleck products hypertension, tachycardia). This is the fight-or-flight response originally described by Cannon.17 Passive coping strategies, such as immobilization or freezing, are usually elicited when threat is inescapable, and are usually characterized by autonomic inhibition (hypotension, bradychardia), and a more pronounced increase in the neuroendocrine response Inhibitors,research,lifescience,medical (activation of the hypothalamopituitary-adrenal axis and increased glucocorticoid

secretion). This type of passive response was originally described by Engel and Schmale as a conservation-withdrawal strategy.18 The concept of alternative (active/passive) strategies itself owes much to the work of Henry and coworkers.

19 Specific brain circuits appear to mediate distinct coping reactions to different types Inhibitors,research,lifescience,medical of stressors.20,21 Inhibitors,research,lifescience,medical According to Panksepp, flight and other active coping behaviors are unconditional responses to proximate threat, whereas passive coping strategies, such as freezing, are conditioned responses to distal stimuli predictive of danger. These two strategies have distinct and successive roles, and are modulated by the (cognitive) apprehension of the environment and probability of success, eg, whether or not there is a route of escape. Thus, when an animal faces a predator, freezing is preferentially activated when the source of known danger is still far Inhibitors,research,lifescience,medical away. When danger gets closer, and the stimulus passes through some critical “psychometric” distance, it becomes a true unconditional stimulus and a flight pattern

is activated.22 Defensive behaviors have been studied in a large number of species,23 and it has recently been shown that human defensive behaviors to threat scenarios arc not unlike those seen in nonhuman mammals.24 The importance of risk assessment in making a proper decision about the best strategy to be used in a particular Inhibitors,research,lifescience,medical context has been emphasized.25 It should be underlined, however, Brefeldin_A that the choice between an active or passive defense strategy does not entirely depend on contextual clues. Individual differences in coping styles do exist and may also influence this choice. In a given situation, some individuals may react actively (“proactive” style), whereas other individuals may react in a more passive way (“reactive” style). These coping styles are characterized by consistent behavioral and neuroendocrine patterns, and may kinase inhibitor Dasatinib explain individual differences in vulnerability to stress-induced diseases.26 Differences in coping styles have also been found between various strains of mice,27 or between genetically selected rat lines,28 which suggests that they have a genetic basis.