Characterization of behavioural responses in different test contexts after a single social defeat in male golden hamsters (Mesocricetus auratus).

The objective of the present study was to characterize behavioural responses of male hamsters in each of three test contexts after they had experienced either a single social defeat or a neutral encounter. In experiment 1, hamsters were observed in a familiar social context (i.e., their home cages), and defeated males displayed different amounts of time and submissive behaviours towards a known opponent than a novel intruder, whereas males in the neutral-encounter groups did not show such differences. In experiment 2, in an unfamiliar social context (i.e., a Y-maze), defeated males generated submissive behaviours and fear memory towards a known opponent that they re-encountered 5-min and 24-h after the defeat. The formation of long-term memory was interrupted by an injection of anisomycin (210 mg/kg). In experiment 3, in a non-social, anxiogenic context, hamsters that had previously had different social experiences did not demonstrate additional anxiety in an elevated plus-maze, with the exception of males that had previously experienced repeated social defeats. Our data suggested that hamsters' behavioural changes following defeat are context-dependent and stimulus-specific. The experience of a single social defeat is sufficient to regenerate submissive behaviours and fear memory when reencountering a known opponent.