Open-field test. Mice were placed individually in the corner of an open-field box (L × W × H, 45 cm by 45 cm by 45 cm) and allowed to explore freely for 6 min. Their spontaneous activities over the last 5 min were recorded. The total move distance was designated as an index of locomotor activity, while increased proportion of time or distance spent in the center (inner 25% of the surface area, away from the walls) indexes decreased anxiety.

Sociability and social novelty preference test. Mice were placed in a rectangular, three-chambered box. Each chamber was 40 cm by 20 cm by 22 cm (L × W × H) in size. Dividing walls were made from clear plexiglass, with rectangular openings (L × H, 35 mm by 35 mm) allowing access into each chamber. The test was composed of three sequential 10-min trials: trial 1, habituation (the mouse was allowed to explore the three chambers); trial 2, sociability (an unfamiliar mouse was placed into a mesh wire cage in either the left or right chamber, and exploration of the three chambers by the test mouse was recorded for a further 10 min); and trial 3, social novelty preference (a novel mouse was placed into a mesh wire cage in the chamber opposite the familiar mouse from the previous stage; exploration of the three chambers by the test mouse was again recorded for 10 min). The amount of time spent in each chamber was recorded. An entry was defined as all four paws in one chamber. Test chambers were cleaned with disinfectant and 70% ethanol after each trial.

PPI test. The test was measured using the SR-LAB System (San Diego Instruments, San Diego, CA) as described previously. Before testing, each mouse was acclimatized to the plexiglass cylinder with background noise (70 dB) for 5 min. The mouse was then exposed to six blocks of seven trial types that were presented in a pseudorandom order with an average intertrial interval of 15 s. The seven trial types comprised the following: trial 1 (startle-only trial), 40 ms, 120-dB sound burst; trials 2 to 6 (prepulse trials), 120-dB startle stimulus preceded 100 ms earlier by 20-ms prepulse sounds of 74, 78, 82, 86, or 90 dB; and trial 7, 70-dB background noise. The startle response was recorded for 65 ms, measuring every 1 ms from the onset of the startle stimulus. The maximum startle amplitude recorded during the 65-ms sampling window was used as the dependent variable. The percentage of PPI induced by each prepulse intensity was calculated as [1 − (startle amplitude on prepulse trial)/(startle amplitude on pulse alone)] × 100%.

Y-maze. The Y-maze apparatus consisted of three dark gray arms (L × W × H, 45 cm by 10 cm by 29 cm). Each mouse was placed at the end of one arm and allowed to freely explore the maze for 8 min. The sequence and total number of arms entered were recorded. Entry into an arm was considered valid only when all four paws of the mouse were inside that arm. The percentage of alternation was used to assess memory performance and calculated by dividing the number of triads containing entries into all three arms by alternation opportunities × 100.

Forced swimming test. The mice were placed individually in plexiglass cylinders (30 cm in height and 15 cm in diameter) filled with 15 cm of water (25° ± 1°C). Test sessions lasted for 6 min, with the last 5 min scored for immobility. A mouse was judged to be immobile when it remained floating in an upright position, making only the movements necessary to keep its head above the water.

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