Socially isolated or group reared rats that were concomitantly handled or non-handled (N = 32; n = 7–9/group) were tested in the open field on postnatal day 70. The open field was a Plexiglas square grey arena (80 × 80 × 80 cm) surrounded by 4 black walls. On the floor, two zones of equivalent areas were defined: a central square compartment of 56 cm/side and a concentric peripheral frame including the area within 24 cm from the walls. Rats were placed in the central zone and behavior was monitored for 5 min. Room light and background noise was kept at 15 lux and 65 dB, respectively. Locomotor activity was measured as the number of times the two front paws of a rat crossed a 4 × 4 grid superimposed onto a video recorded image of the open field. The duration of time spent in the central compartment of the open field and number of fecal boli excreted during this test was also assessed.
