Using EthoVision to study social interactions in rodents.

Berry Spruijt, Thorwald Hol and Jacob Rousseau

Rats have a complex repertoire of social behaviours. In their natural habitat they live in groups, but may share resources such as food and water. In laboratory situations in the presence of a receptive female, male rats rapidly develop combative behaviours towards unfamiliar conspecifics. As social behaviour is an accessible "read-out system", it is often used for studying brain-behaviour relationships, e.g. as a model for anxiety. This research is focused on the behavioural and physiological characteristics of social isolation.
Each animal was continuously tracked using EthoVision. From these data the inter-individual distance and the direction of movement regarding the animals were derived. If an isolated and a socially housed animal were confronted with each other, the isolated animal was relatively more likely to approach than the socially housed animal. In addition, opiates were shown to affect the response to isolation. Isolated animals that had been treated chronically (two weeks) with morphine did not show any signs of isolation. Also local treatment with the ACTH(4-9) analogue Org2766 into the central nucleus of the amygdala counteracted the isolation-induced enhancement of approach-like behaviour. Prenatal treatment with morphine also influenced approach and avoidance behaviours in adulthood as assessed by EthoVision.