Abstract
The concepts of allostatic load and overload, i. e., a dramatic increase in the allostatic load that predisposes to disease, have been extensively described in the literature. Here, we show that rats engaging in active offensive response (AOR) behavioral strategies to chronic predator scent stress (PSS) display less anxiety behavior and lower plasma cortisol levels vs. rats engaging in passive defensive response (PDR) behavioral strategies to chronic PSS. In the same chronic PSS paradigm, AOR rats also have higher lactate and lower glutamate levels in amygdala but not in control-region hippocampus vs. PDR rats. The implications of these findings for regulation of allostatic and stress responses, and post-traumatic stress disorder (PTSD) are discussed.
Highlights
Many physiologic and behavioral consequences of homeostatic adaptations during chronic stress, and differences between homeostatic and allostatic regulation— as regards the limbic hypothalamic pituitary adrenal (LHPA) axis—remain undefined
There was a significant influence of behavioral phenotype in response to predator scent stress (PSS) on a relative number of branch entries [F(2,25) = 10.84, p < 0.001], exploring [F(2,25) = 14.3, p < 0.001], and time [F(2,25) = 21.04, p < 0.0001] in open arms (OA)
PSS led to increased OA entries, OA exploring, and OA times in the active offensive response (AOR) rats vs. the passive defensive response (PDR) rats or unstressed controls
Summary
Many physiologic and behavioral consequences of homeostatic adaptations during chronic stress, and differences between homeostatic and allostatic regulation— as regards the limbic hypothalamic pituitary adrenal (LHPA) axis—remain undefined. Advancing knowledge in these areas has the potential to significantly increase our understanding and treatment of stress and stress-related disorders, such as post-traumatic stress disorder (PTSD). Biological changes that occur during the adaption and exhaustion stages are referred to as allostasis and allostatic overload; they include activation of the LHPA axis and its downstream effector pathways, and changes in immune responses, cardiovascular and energy metabolism, and hypothalamus-mediated behavior (Korte et al, 2005). An allostatic state is defined by chronic deviation of regulatory systems away from their normal state of operation, to establish a new set point (Koob and Le Moal, 2001)
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