Social stress, immune functions and disease in rodents

Relations between different coping strategies for social stress, tumor development and neuroendocrine and immune activity in male mice

This study analyzes the effects of acute social stress and different coping strategies employed in response to it on the development of B16F10 melanoma pulmonary metastases, the activation of the HPA axis and the NKG2D receptor expression. To this end, male OF1 mice were subjected to 24h of social stress using the sensorial contact model. This model includes three 5-min sessions of direct social interaction with resident cagemates selected for consistent levels of aggression. Subjects' behavior was videotaped and assessed. Six days after the first social interaction (1st social stress), the animals were inoculated with tumor cells or vehicle, and six days later, both tumor-bearing and non tumor-bearing mice were subjected to a second 24h sensorial contact social stress session (2nd social stress). One hour after the 2nd social interaction, corticosterone levels and NKG2D receptor expression were determined. Lung metastatic foci numbers were determined 21 days after inoculation (15 days post-stress). Social stress increased the number of pulmonary metastases and the serum corticosterone level. A combination of cluster and discriminant analyses established the existence of two types of coping strategies: (1) a passive-reactive strategy characterized by subjects dedicating a greater percentage of time to submission, flee and avoidance behaviors; and (2) an active-proactive strategy, characterized by subjects dedicating a greater percentage of time to attack and non social exploration behaviors. Subjects belonging to the passive-reactive group were found to have a higher number of tumor foci, a higher level of corticosterone and a lower NKG2D receptor expression than subjects in the active-proactive group. These data indicate the relationship between different coping strategies for social stress and tumor development.

Chronic social stress, hedonism and vulnerability to obesity: lessons from rodents

Obesity is a current health pandemia. Determinants of this pathology are rather complex and include genetic, developmental and environmental factors only partially disclosed. Stress related neuroendocrine dysregulation and overconsumption of high palatable high caloric food and are likely to contribute to this modern health threats. Despite the evidence that psychosocial stress is one of the main sources of stress in humans and may play an important role in the development of the stress disorders, including obesity and metabolic syndrome, animal models focusing on the relationship between chronic stress and energy homeostasis are scattered and most of them encompasses physical rather than psychosocial stress. Aim of the present paper is to review rodent studies on the effect of psychosocial stress throughout life on body weight and food intake regulation. In the second part of the review special focus will be given on the mechanisms linking stress and the reward system.

Towards developing standard operating procedures for pre-clinical testing in the mdx mouse model of Duchenne muscular dystrophy

This review discusses various issues to consider when developing standard operating procedures for pre-clinical studies in the mdx mouse model of Duchenne muscular dystrophy (DMD). The review describes and evaluates a wide range of techniques used to measure parameters of muscle pathology in mdx mice and identifies some basic techniques that might comprise standardised approaches for evaluation. While the central aim is to provide a basis for the development of standardised procedures to evaluate efficacy of a drug or a therapeutic strategy, a further aim is to gain insight into pathophysiological mechanisms in order to identify other therapeutic targets. The desired outcome is to enable easier and more rigorous comparison of pre-clinical data from different laboratories around the world, in order to accelerate identification of the best pre-clinical therapies in the mdx mouse that will fast-track translation into effective clinical treatments for DMD.

Stress amplifies memory for social hierarchy

Individuals differ in their social status and societies in the extent of social status differences among their members. There is great interest in understanding the key factors that contribute to the establishment of social dominance structures. Given that stress can affect behavior and cognition, we hypothesized that, given equal opportunities to become either dominant or submissive, stress experienced by one of the individuals during their first encounter would determine the long-term establishment of a social hierarchy by acting as a two-stage rocket: (1) by influencing the rank achieved after a social encounter and (2) by facilitating and/or promoting a long-term memory for the specific hierarchy. Using a novel model for the assessment of long-term dominance hierarchies in rats, we present here the first evidence supporting such hypothesis. In control conditions, the social rank established through a first interaction and food competition test between two male rats is not maintained when animals are confronted 1 week later. However, if one of the rats is stressed just before their first encounter, the dominance hierarchy developed on day 1 is still clearly observed 1 week later, with the stressed animal becoming submissive (i.e., looser in competition tests) in both social interactions. Our findings also allow us to propose that stress potentiates a hierarchy-linked recognition memory between "specific" individuals through mechanisms that involve de novo protein synthesis. These results implicate stress among the key mechanisms contributing to create social imbalance and highlight memory mechanisms as key mediators of stress-induced long-term establishment of social rank.