1). Despite the convergence and interaction of these hormonal and

neurobiological variables that may render the adolescent particularly vulnerable to stressors, not all adolescents are adversely affected by stress and experiencing stressors during adolescence does not inevitability result in negative outcomes. However, it is unclear what may account for the different reactions that adolescents show in response to stress exposure. Some differences in the neurobehavioral responses to adolescent stress across studies are undoubtedly mediated by subtle or significant differences in the specific experimental paradigms and/or assays used. For instance, studies that exposed adolescent rats to social defeat stress found either increased or decreased anxiety-like behaviors in adulthood (Watt Gemcitabine et al., 2009 and Weathington et al., 2012), but these diametrically opposed results can likely be explained by experimental

differences, such as the length and frequency of the social defeat and the animal housing conditions (i.e., single vs. group) used in these two studies. More intriguing, however, BMN 673 cell line is the difference in how individual animals respond to a stressor within an experiment. A greater understanding and appreciation of this variation may potentially shed light on what makes some animals more or less resistant to stressful experiences. To

illustrate this stress-induced variability, I present a specific example from a pilot study we recently conducted. Briefly, in this study we exposed others adolescent male rats to 1 h of restraint stress every other day from postnatal day (PND) 28–49. This age span was used as this 3 week period in rodents is associated with the most significant changes in physiological, neurobiological, and behavioral parameters as animals transition into adulthood (Spear, 2000). We then tested these animals in the forced swim test in young adulthood to measure depressive-like behaviors (Porsolt et al., 1977). We found that the rats exposed to restraint stress during adolescence showed a shorter latency to immobility than age-matched non-stressed controls (Fig. 2; unpublished observation). Though these results suggest that adolescent stress exposure leads to depressive-like behaviors in adulthood, these data are presented here to provide an example of the relatively high degree of variability in the experimental group. Specifically, the mean and standard deviation of the control group are 176.0 and 33.6, respectively, while the stress group is 72.2 and 79.3, respectively. This high standard deviation in the experimental group indicates a rather large spread around the mean.