2010). Methods are identical to those reported previously (Lad et al. 2010), except

for the timing of the test. Mice were transferred to these home cages during the middle of their light cycle (between 12:30 and 13:00). Recording took place at three time points during the 24 h test (13:00–14:00; 01:00–02:00; 11:30–12:30). The first hour (13:00–14:00) following the transfer of the mice measured their behavior in response to the novel environment. The second hour (01:00–02:00) assessed their behavior during the dark phase (the active phase for mice which are nocturnal mammals), following 12 h of habituation. The last hour (11:30–12:30) measured the behavior of the mice following Inhibitors,research,lifescience,medical an extended period (>22 h) of habituation during a typically low activity phase (light phase). Four

red multi-LED cluster lamps (LED cluster red light No. 310-6757; RS Components Northants, UK) of approximate wavelength 705 nm were DNA Synthesis inhibitor placed in the test room to provide sufficient lighting Inhibitors,research,lifescience,medical for the image capture, but give the appearance of darkness to the mice given the wavelength of the lamps. Open field The open field was performed as described previously (Lad et al. 2010), except for light level which was ~30 lux. Novel Inhibitors,research,lifescience,medical object exploration Novel object exploration was performed 48 h after the open field test using the open field arena (see Lad et al. 2010 for details). During the novel object exploration task, each mouse was exposed to two identical novel objects for 5 min. The Ethovision program was utilized for both automated tracking and manual scoring. Manual scoring allowed accurate measures of exploration Inhibitors,research,lifescience,medical (frequency and duration) of each object to be made. Holeboard The holeboard (File 2001), used to measure activity Inhibitors,research,lifescience,medical and exploration in a novel arena, was run in a Tru Scan Photo Beam Activity

System (Coulbourn Instruments, Allentown, New Jersey), which consisted of an automated arena (25.4 × 25.4 × 40.6 cm) with sensor rings to track movement in the arena (light level 300 lux). The beams were spaced 1.52 cm apart providing a 0.76 cm spatial resolution. A metal floor was used, containing 16 holes (2.2 cm in diameter), evenly distributed over the floor (4 × 4 configuration). The floor others also contained sensors to detect nose pokes. Mice were placed individually in a corner of the holeboard and allowed to freely explore for 5 min. The distance traveled, number of holes visited, and time spent in the center (17.8 × 17.8 cm) were recorded using the Tru Scan Software Version 2.0 (Coulbourn Instruments). Forced swim The forced swim test (Porsolt et al. 1978) was carried out in a clear Perspex tube (49 cm high × 15 cm diameter) filled with water at room temperature (depth 40 cm). Twenty-four hours prior to the trial, a blood sample was taken to provide a baseline measure of corticosterone, see below.