254 consecutive time interval (contextual fear conditioning) and before-tone vs. after-tone interval (cued fear condi- tioning), respectively. Effects of corticosterone treatment on baseline synap- tic transmission were tested by comparing the average slope of the fEPSP of the first baseline (−20 to −10 min) with the average of the second baseline (−10 to 0 min) using a three-factor repeated measures ANOVA (be- tween-subjects factors: early life treatment and drug treatment; within-subjects factor: baseline). To determine the effects of early life stress and application of the stress hormone corticosterone on the degree of LTP, a three- factor repeated measures ANOVA was performed using early life treatment and corticosterone treatment as between-subjects factors and pre- or post-TBS as within-subjects factor. We compared the second baseline (−10 to 0 min) with early LTP (0–30 min post-TBS) and total LTP (0–60 min post-TBS). When significant, a post hoc LSD test was performed to compare treatment groups. Results Experiment I. Body weight and basal corticosteroid levels are reduced by MD On PND 51, MD females had significant (p = 0.003) lower bodyweights (171 ± 3 g, n = 8) compared to CON females (194 ± 6 g, n = 8). Although we have no explanation for the lasting reduction in body weight, it is possible that 24-h maternal deprivation at PND 3 programmes metabo- lism in such a way that body weight is persistently reduced. In addition, basal corticosterone levels were significantly lower in MD (47 ± 11 ng/ml) than in CON (127 ± 23 ng/ml) animals (p= 0.002). Thirty minutes after a moderate stressor (tail nick), corticosterone levels were elevated in both groups. Although at that time point plasma corticosterone levels were higher in CON than MD animals (639± 129 ng/ml (n= 8) vs. 373±101 ng/ml (n= 9), respectively), this differ- ence did not reach significance (p= 0.2). One hour after swim stress, both CON (482±87 ng/ml, n= 10) and MD (302± 102 ng/ml, n = 10) rats showed similar elevations in corticosterone level (p= 0.2). Experiment II. Maternal deprivation only mildly affects neurogenesis, cell morphology and dentate gyrus architecture Stereological quantification of several phases of adult neurogenesis in the dentate gyrus revealed no significant effects of MD on the total numbers of proliferating cells (Ki-67+), on the number of 18-day-old newborn (BrdU+) Psychopharmacology (2011) 214:249–260 Table 1 Effects of MD on adult neurogenesis Proliferation (Ki-67) Cell survival (BrdU) Neuronal differentiation (DCX) CON (n =8) MD (n =8) 2,843±264 1,703±120 32,769±2,594 2,661± 206 1,588± 103 29,343± 2,143 Absolute cell numbers per hemisphere were not significantly different between CON and MD animals (p>0.1) cells and on the number of young neurons (DCX+) reflecting neurogenesis (Table 1). Further detailed analysis was performed by comparing total cell numbers according to their distribution along the rostrocaudal axis, between the supra- and infra-pyramidal blade and as a percentage of total cells. This also did not reveal any significant differences. While neurogenesis was not affected by maternal deprivation, stereological quantification of the number of DG granule neurons revealed that maternal deprivation significantly reduced the total cell number (p = 0.04) and cell density (p = 0.03) in the GCL by about 12% (Fig. 1a, b), without affecting granular cell layer volume (CON 1.03 ± 0.03 mm 3 ; MD 1.05 ± 0.02 mm3, p = 0.51) or the volume of 3 the molecular layer (CON 3.26 ± 0.16 mm ; MD 3.25 ± 0.08 mm3, p = 0.94). Morphological analysis of the Golgi-stained individual neurons revealed a change in the dendritic arrangement, but not total dendritic length, number of branch points or spine density in females subjected to MD (Table 2). The average number of primary dendrites extending from the soma was increased (p = 0.02) in MD animals when compared to controls. Fig. 1 Effects of MD on the granule cell layer of the hippocampal dentate gyrus. a MD treatment caused a significant reduction in absolute granule cell numbers (p=0.04) as well as b cell density (p=0.03; both groups n=8)