Light-dark box test.
The LDB apparatus consists of a box (64 x 48 x 24 cm3) that is divided in 2 different chambers: light chamber (two-thirds of the total size) and dark chamber (one-third of the total size). The light and dark chambers are connected by a squared opening (8 x 8 cm2). The light chamber, which is uncovered, has white walls, and is illuminated by white light (400-lux). The dark chamber has black walls and has no appreciable illumination at the centre of the chamber (≤ 2 lux). After at least 5 min of habituation, animals were gently placed at the centre of the light box, with the head facing opposite to the squared opening, and then animals explored freely for 5 minutes. Spontaneous behaviours of the rats were videotaped in the light box during the test for its posterior analysis. The test was performed during the dark cycle, at least 2 hours after the lights went off. The analysed parameters were the time spend in the light box (seconds, s) and the number of transitions between chambers. All the measurements were expressed as the mean ± SEM.