Abstract # 1728 Physical versus psychosocial stress: Distinctive stressors result in differential behavioural and biological phenotypes

Abstract

Chronic stress can alter the immune system, stress reactivity, and induce anxiety-and depressive-like behaviour in rodents. However, no study to date has discriminated between the effect(s) of different types of stress. Previous research in our laboratory has shown that physical stress, modelled by daily intraperitoneal injection, induces an anxiety-like behavioural phenotype, while psychosocial stress, modelled by permanent social isolation, induces a depressive-like behavioural phenotype. To determine whether a distinct biological profile corresponds to each of these behavioural phenotypes, we assessed stress responsivity and immune system functioning in our animals exposed to social isolation and/or chronic injection. Here, we show how chronic injection significantly increased stress responsivity, and decreased plasma levels of tumour necrosis factor (TNF)- α in adult male BALB/cAnCrl mice. In contrast, permanent social isolation significantly decreased stress responsivity, and resulted in multiple immunological changes, specifically increasing plasma levels of TNF- α , and decreasing levels of interleukin (IL)-12, IL-10, and vascular endothelial growth factor (VEGF). Interestingly, animals exposed to both stressors had a stress response similar to control animals, and had significantly decreased levels of VEGF. Our data show how two different types of stress, which lead to distinct behavioural phenotypes, results in divergent biological outcomes. Moreover, there appears to be no additive effect of combining physical and psychosocial stress on animal physiology. Indeed, combining distinctive stressors may be masking the effect of individual stressors.