Behavioral Testing
To assess aggressive behaviors, RVI was used. RVI test was applied according to Koolhaas et al. (2013) with modifications. Briefly, the RVI test consists of the interaction of two subjects: the experimental animal, named the resident, and the interaction animal, named the intruder. RVI test was performed 6 days after pCPA administration, between 15:00h and 18:00h (Corthell et al., 2013). In order to verify that residents were heavier than intruders, the animals were weight before the test. The test was carried out in a wood box with the wood chips from the resident home cage. The box was cleaned after each test, with ethanol (10%) (Casas et al., 2011). All the tests were recorded with the Everio G-series GZ-MG330 JVC camera, from above the field. Behavioral analysis was hand scored watching the videos in blind.
RVI test total time was 900 seconds. RVI test total time was divided into two phases, the adaptation phase, and the interaction phase. The first 300 seconds were considered the resident adaptation phase to the environment. 600 seconds remaining were considered the interaction phase. At the beginning of the interaction phases, an intruder was placed on the opposite side of the resident at the end of the adaptation phase and the interaction behaviors were measured. We evaluated the animal locomotor activity as the travel distance during the adaptation phase. In the interaction phase, we evaluated four main groups of behaviors: 1-nonsocial activity, as time grooming, sniffing, and sitting; 2-social activity as the time of heterogrooming and heterosniffing; 3-aggressive behavior, as an event of the chase, moving towards, upright posture and false mount, bite, clinch, clinch attack, lateral threat and keep down were evaluated in the resident during interaction phase; and 4-aggressive latency, as the time preceding the first aggressive behavior. The criteria to discontinue resident interactions with the intruders were bite to delicate body parts e.g. belly, throat and paws.