Exposure to the social interaction test in rats induces changes in defensive burying

To detect changes in experimental anxiety, defensive burying (DB) was studied in several groups of rats after being exposed to social interaction (SI). Animals were studied in the DB paradigm after being submitted to the following SI treatments: control (without SI exposure), and SI for 1.5, 5, 10 and 15 min respectively. A bimodal effect was found: facilitated DB response values in the group tested after a 1.5 min exposure to SI and a strong reduction of DB in the 10 and 15 min groups. The inhibition in DB elicited by the 15 min exposure to SI revealed a slow recovery, returning to control levels after 30 min. The actions of novelty on defensive burying were assessed in a third experiment. Animals were tested for DB immediately after being placed for 1.5 or 15 min in the SI arena without a partner. DB levels increased in these animals. Another group was placed in the SI arena for 1.5 min and tested in the DB paradigm 13.5 min after being returned to the home cage. A return to the basal control DB levels was observed in this group. Data are discussed in terms of anxiety-like fluctuations and the adaptive functions underlying these.