250 stress-related disorders in adult individuals (Heim and Nemeroff 2001; Heim et al. 2000; McEwen 2003; Rao et al. 2010) and particularly in women. Early life stress in rodents can be induced by maternal separation (MS) or maternal deprivation (MD), i.e. the removal of the dam for a given period of time (>3 or 24 h, respectively) during the first two postnatal weeks (Lehmann and Feldon 2000; Levine et al. 1991). MS and MD were shown to increase corticosterone levels during the early postnatal period (Rosenfeld et al. 1992; Schmidt et al. 2004; Stanton et al. 1988) and can programme hypothalamic–pituitary–adrenal axis function later in life (Lehmann et al. 2002; Plotsky and Meaney 1993; Workel et al. 2001). Interference during the first two postnatal weeks may therefore be of particular relevance for the maturation of the dentate gyrus, a sub-region of the hippocampus that develops for the larger part postnatally (Altman and Bayer 1990a, b). In addition to this, the dentate gyrus exhibits lifelong structural plasticity in the form of adult neurogenesis, a process that has been implicated in hippocampus-dependent learning and memory (Deng et al. 2010; Dupret et al. 2007; Kempermann 2005; Leuner and Gould 2010). These young, adult-born granule cells contribute significantly to behavioural functions such as contextual fear memory, spatial pattern separation and spatial learning (Clelland et al. 2009; Kitamura et al. 2009; Saxe et al. 2006). The role of neurogenesis in stress-related pathology is still under debate (Lucassen et al. 2010a; Sahay and Hen 2007), but neurogenesis seems required for the behavioural effects of (certain) antidepressants in animal studies (Santarelli et al. 2003; Surget et al. 2008). Surprisingly—given the relevance of structural changes in conjunction with early life stress for depression in women—little is known on how exposure to early life stress affects DG structure and function in (adult) female offspring (Andersen and Teicher 2004; Petersen et al. 2008). Recently, it was reported that adult female rats suffer from memory impairments and depressive-like behaviour in adulthood after early life stress, indicating that females are affected functionally by these stressors (Aisa et al. 2008). In a previous study from our group, we found that early maternal deprivation (24 h at postnatal day (PND) 3) reduces the number of immature neurons in the dentate gyrus of the hippocampus in young (PND 21) female, but not male rats (Oomen et al. 2009). This suggested that females apparently respond strongly to a severe early life stressor, which may render them sensitive to hippocampal dysfunction in adulthood. Here, we tested if hippocampal function and structure in female rats exposed to MD is indeed compromised at an adult age. Therefore, we examined the effects of 24 h MD on PND 3, a critical time point in dentate gyrus maturation (Altman Psychopharmacology (2011) 214:249–260 and Bayer 1990a, b), on adult neurogenesis and granule cell morphology. Furthermore, we addressed lasting functional consequences of MD during development, by studying spatial and emotional learning in vivo and synaptic plasticity in vitro, both under stressful and neutral conditions. Materials and methods Animals and breeding procedure All animal procedures presented in this paper were in compliance with the principles of laboratory animal care and were approved by the animal ethics committee of the University of Amsterdam, The Netherlands. To minimise variation and to avoid stress in the perinatal environ- ment, all animals were bred in-house. Wistar rats were purchased from Harlan (Zeist, The Netherlands), kept under standard housing conditions (dark/light phase 12:12, lights on at 8 a.m., humidity 55 ± 15%, tempera- ture 20–22°C) and habituated to the animal facilities for 10 days. For breeding, one male rat was put together with two females for a period of 1 week. After mating, females were pair-housed until the beginning of the third gestational week. Then, females were individually housed with extra bedding material and monitored for birth each morning at 9 a.m. If a litter was found, the previous day was designated PND 0, day of birth. Dams with litters were left undisturbed until PND 3 and then randomly assigned to one of the two experimental (MD or control (CON)) groups, making sure that litters from the same father were not in the same experimental group. Maternal deprivation procedure On the morning of PND 3 (9 a.m.), litters were separated from their mother as a whole, shortly handled, culled to four males and four females, and placed back into their home cage. The cage was placed on a heating pad in another room to avoid disturbance by vocalisation in the breeding room. The dam was housed in a novel cage and returned to the breeding room. Litters were kept warm by placing them on a heating pad set at a temperature of 32°C during the 24-h deprivation period. Litters were, with the exception of two litters of six pups, larger than or equal to eight pups, with an average of 11 ± 2 pups. Due to large litter size, culling to four males and four females was usually possible. In this study, we repeated the exact same experimental procedure as in our previous study (Oomen et al. 2009). No pups were lost during the MD procedure.