The strain of unfamiliar conspecifics affects stress identification in rats

• Published in: Behavioural processes 2022-09, Vol.201, p.104714-104714, Article 104714
• Main Authors: Kiyokawa, Yasushi, Kuroda, Naoko, Takeuchi, Yukari
• Format: Article
• Language: English
• Subjects: Emotion identification; Ingroup advantage; Ingroup favouritism; Strain differences
• ISSN: 0376-6357; 1872-8308
• DOI: 10.1016/j.beproc.2022.104714

Humans show distinct social behaviours when we evaluate an individual as being a member of the same group and recognize social similarity to the individual. One example is more accurate identification of emotion in that individual. Our previous studies proposed that rats recognize social similarity to certain strains of unfamiliar rats. It is therefore possible that the strain of unfamiliar conspecifics affects stress identification in rats. Wistar subject rats were allowed to explore a pair of unfamiliar Wistar, Sprague-Dawley (SD), Long-Evans (LE), or Fischer344 (F344) stimulus rats. To induce differences in stress, one of the stimulus rats had received foot shocks immediately before the test. It was found that the subjects showed biased interaction towards the shocked Wistar and SD stimulus rats, but not toward the shocked LE or F344 stimulus rats. Subsequent experiments confirmed that the biased interaction towards the shocked Wistar and SD stimulus rats was driven by stress in these stimulus rats. In addition, the lack of biased interaction towards the shocked LE and F344 stimulus rats did not appear to be due to procedural reasons. The experiment using LE subject rats further confirmed that the shocked LE stimulus rats emitted distress signals. These results suggested that Wistar rats could identify stress in unfamiliar Wistar and SD rats, but not in unfamiliar LE or F344 rats. Therefore, rats appear to recognize social similarity to certain unfamiliar strains of rats. •Subjects were offered a choice between a naive and shocked rat of the same strain.•Biased interaction towards the shocked rat was regarded as stress identification.•Wistar subjects could identify stress in unfamiliar Wistar and Sprague-Dawley rats.•Wistar subjects could not identify stress in unfamiliar Fisher344 rats.•Wistar and Long-Evans rats could not identify stress in each other.