The proposed project examines coping behavior and individual differences in reactivity to inescapable shock in the """"""""learned helplessness"""""""" model of depression. Rats exposed to inescapable shock show a variety of behavioral and physiological disorders. By contrast, the availability of a simple escape response protects the animal against virtually all forms of debilitation. Such coping behavior is assumed to exert its prophylactic action by reducing the amount of time spent in fear during the pretreatment session. Stimuli generated by the act of escaping are postulated to acquire fear-inhibiting properties, thereby attenuating fear conditioning and mitigating the nonassociative consequences of chronic fear. Thus the ability to control shock termination serves as an effective coping mechanism only because it enhances prediction of shock termination and a shock-free period -- there is nothing inherently prophylactic about instrumental control. From this view, it should be possible to model the beneficial effects of an escape response with the presentation of exteroceptive stimuli in various contingent relations with inescapable shock. When all the relevant signal features of an escape response are represented by external stimuli, the dimension of instrumental control should not contribute to group difference in a helplessness experiment. Individual differences in reactivity to inescapable shock will be studied within the context of social dominance. Whereas submissive rats appear to be particularly vulnerable to inescapable stresses, dominant rats appear to be """"""""resistant"""""""" or """"""""immune"""""""". Research is proposed to assess the extent of the difference between dominant and submissive rats, and rats genetically selected for differences in emotionality, in the helplessness paradigm. Experiments also will determine the relation, if any, between dominance, emotionality, and helplessness. This project has relevance to the prevention of stress effects, mechanisms of coping, and represents a partial test of an anxiety-based interpretation of """"""""learned helplessness"""""""". an animal model of depression.
