Social defeat models in animal science: What we have learned from rodent models

Abstract

Studies on stress and its impacts on animals are very important in many fields of science, including animal science, because various stresses influence animal production and animal welfare. In particular, the social stresses within animal groups have profound impact on animals, with the potential to induce abnormal behaviors and health problems. In humans, social stress induces several health problems, including psychiatric disorders. In animal stress models, social defeat models are well characterized and used in various research fields, particularly in studies concerning mental disorders. Recently, we have focused on behavior, nutrition and metabolism in rodent models of social defeat to elucidate how social stresses affect animals. In this review, recent significant progress in studies related to animal social defeat models are described. In the field of animal science, these stress models may contribute to advances in the development of functional foods and in the management of animal welfare.

Keywords: depression; feed; metabolome; social defeat.

Figure 1

Development of a mouse model of social defeat. An ICR mouse is housed in a compartment separated by a transparent acrylic divider containing many holes (a). After a few days of habituation, a C57BL/6J (B6) mouse is introduced into this compartment, and normally the ICR mouse will severely attack the B6 mouse (b). After several minutes of this social conflict, the B6 mouse is moved to an adjacent compartment for the remainder of the day (c). The following day, the B6 mouse is subjected to social conflict with another ICR mouse. This sequence of physical and psychological stress is repeated for 10 days to induce depressive symptoms in the B6 mouse.

Figure 2

Social interaction test for evaluation of defeated mice. The social behavior of stressed and control B6 mice is monitored with or without ICR mice (a). Control and resilient mice engage in social interaction with ICR mice (b), whereas susceptible mice avoid ICR mice (c).