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.