Sociability and Social Novelty Tests

Sociability and social novelty tests were performed as previously described [60 (link)]. Sociability and social novelty were analyzed in an arena (60 × 60 cm) with two equidistant clear Plexiglas cylinders (each 7 cm in diameter, 12 cm tall). The cylinders had multiple holes (1 cm in diameter) to allow the auditory, visual and olfactory interaction between the stimulus mouse placed inside and the test mouse outside of the cylinder. Between trials, the apparatus and cylinders were cleaned with 75% ethanol and dried before testing the next mouse. Time sniffing the social and non-social cylinders was operationally defined as the time during which the test mouse made direct nose-to-cylinder contact with the social and non-social cylinders, respectively. This was captured and recorded with Sony digital video camera mounted above the chamber. The paradigm consisted in a three-stage procedure: During habituation phase, the testing mouse was allowed to initially explore the apparatus with the cylinders for 10 min. In social approaching phase, an unfamiliar sex-matched mouse was placed in one of the cylinder, maintaining the other empty. Finally, in social novelty test, another unfamiliar mouse was introduced to the other empty cylinder. In the preference for social novelty test, preference score was calculated by subtracting the time spent sniffing the two stranger mice.