Psychopharmacology (2011) 214:249–260 ethanol) or vehicle (0.01% ethanol) was added to the aCSF during the second half of baseline recordings (t = −10 to 0 min), co-terminating with TBS (Bagot et al. 2009). This concentration of corticosterone was shown before to occupy both MR and GR and is therefore comparable and relevant to mimic in vivo stressful situations (Champagne et al. 2008; Karst et al. 2000). Experiment IV. Spatial and emotional learning One cohort of animals (ten CON and ten MD rats) was used for three behavioural tasks described in the following section. Animals were housed in pairs. During testing, rats from the same home cage were tested on different days to avoid effects of acute stress. Before and in between tasks, rats were handled every other day, starting 2 weeks before the start of the first experiment. The order of testing was as described below, and the time in between tasks was at least 1 week. To study potential changes in basal exploration and anxiety levels after maternal deprivation, CON (n = 10) and MD (n = 10) rats were tested in an elevated plus maze at the age of 11 weeks. For this, each rat was transferred from its home cage to the experimental setup in an adjacent room. In this testing room, animals were put on the centre of a plus maze (100 cm from the ground), facing one of the two open arms. The plus maze was made of black plastic and shaped like a cross with two opposite open arms (10 × 40 cm) and two opposite closed arms (10 × 40 cm, 25-cm-high walls) connected to an open centre. Animals were placed in the centre and allowed to freely explore the open and closed arms for 5 min. Exploration patterns were recorded by a video camera coupled to a computer and processed by Ethovision (Noldus, Wageningen, The Netherlands). Total time, frequency and latency to first appearance in all compart- ments of the maze were analysed to determine the exploration pattern. To determine spatial learning ability of MD rats, animals were trained in a Morris water maze (Morris 1984). CON (n =10) and MD (n = 10) animals (13 weeks old) were trained in 2 days, during which they received four trials per day with an inter-trial interval of 15 min. The water maze (150 cm in diameter) was situated in a room adjacent to where animals were housed and filled with opaque water (22°C, with added non-toxic paint). In one quadrant (NW), a transparent platform (12 cm in diameter) was hidden 0.5 cm under the water surface. During training, trials were started in one of the three quadrants without platform (i.e. NE, SW or SE quadrant) and starting position alternated between trials, rats and days. At the start of each trial, rats were placed in the water facing the wall of the pool. Animals were allowed to swim in the maze until they had 253 reached the platform or until a maximum time of 2 min had passed. When rats were unable to find the platform, they were guided there manually. Animals were left on the platform for an additional 20 s. Trials were recorded and analysed for latency, swim distance and time in the platform quadrant (Ethovision; Noldus). To assess hippocampus- and amygdala-dependent emotional memory, rats were subjected to contextual and cued fear conditioning (Phillips and LeDoux 1992; Zhou et al. 2009). During fear conditioning, 15-week-old rats (CON = 10; MD = 10) learned to associate a fearful stimulus (foot shock) with a context (conditioning box) and a cue (tone). The strength of fear-associated memory was determined by measuring the amount of freezing behaviour. Scoring was done manually, every 2 s, by two observers blinded to the experimental group. Rats were habituated to the experimental room starting 2 days before conditioning. Animals were trained by placing them in the fear conditioning box (30 × 26 × 24 cm, walls made of black and transparent plastic with metal grid floor) in which they were allowed to explore freely for 3 min. After that, a 30-s tone was played (100 dB, 2.8 kHz) that co- terminated with a foot shock (12 s, 0.4 mA). On the second day at the same time, animals were put into the conditioning box for 3 min under identical circumstances (i.e. the same cleaning solvent, lighting conditions, gloves and lab coats). Contextual memory was evaluated by scoring freezing behaviour. Two hours later, cued memory was tested by placing rats in a different box, with a solid white floor and light-coloured walls under changed circumstances (i.e. different cleaning solvent, lighting conditions, gloves and lab coat). Again, rats were allowed to explore the box freely for 3 min, after which the tone was presented for 30 s. Rats remained in the box for an additional 60 s to determine the behavioural response to the cue. Statistical analysis Statistical analysis was performed using SPSS 16.0. All data are presented as average ± SEM. Differences between CON and MD animals concerning body weight, corticoste- rone levels, levels of neurogenesis (all expressed per hemisphere), morphological parameters and water maze probe trial were tested for significance using a two-tailed Student’s t test with a probability level of 5%, after determining equality of variances using Levene’s test (all data p> 0.05). Differences in acquisition of the water maze, context- dependent freezing and cue-dependent freezing were tested with a single-factor repeated measures ANOVA using early life treatment as a between-subjects factor. Within-subjects factors were used: trial (water maze),