Neuroscience
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Review Comparative Study
Steroid hormones, stress and the adolescent brain: a comparative perspective.
Steroid hormones, including those produced by the gonads and the adrenal glands, are known to influence brain development during sensitive periods of life. Until recently, most brain organisation was assumed to take place during early stages of development, with relatively little neurogenesis or brain re-organisation during later stages. However, an increasing body of research has shown that the developing brain is also sensitive to steroid hormone exposure during adolescence (broadly defined as the period from nutritional independence to sexual maturity). ⋯ Current research suggests that the effects of adolescent stress vary depending upon the sex of the individual and type of stressor, and the effects of stress could involve several neural systems, including the serotonergic and dopaminergic systems. Experience of stressors during adolescence could also influence brain development via the close interactions between the stress hormone and gonadal hormone axes. While sensitivity of the brain to steroid hormones during early life and adolescence potentially leaves the developing organism vulnerable to external adversities, developmental plasticity also provides an opportunity for the developing organism to respond to current circumstances and for behavioural responses to influence the future life history of the individual.
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Accumulating evidence suggests that adolescence represents a sensitive period during which social stressors influence adult behavior and stress reactivity. However, relatively little is known about the impact of social stress in adolescence on behaviors or stress reactivity in females. In this study, we exposed adolescent or adult female rats to the repeated social stress of defeat for seven consecutive days. ⋯ Using exposure to a novel restraint to assess stress reactivity, we found that stress during adolescence and adulthood led to lower basal adrenocorticotropic hormone concentrations and that both stressed and control adolescent groups exhibited a delay in recovery in adulthood compared to stressed and control adult groups. Fos protein analysis further suggested that cortical/thalamic structures serve as potential substrates that mediate these long-term impacts of stress during adolescence. Thus, repeated social stress during adolescence produces different patterns of effects as compared with repeated social stress during adulthood.
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There is increasing evidence for adolescence as a time period vulnerable to environmental perturbations such as stress. What is unclear is the persistent nature of the effects of stress and how specific these effects are to the type of stressor. In this review, we describe the effects of chronic, unpredictable stress (CUS) exposure during adolescence on adult behavior and brain morphology and function in animal models. ⋯ Finally, we discuss potential underlying mechanisms for these morphological and behavioral findings. It is our aim that the research highlighted in this review will aid in our understanding of the role of stress in adolescent mental health and development. This article is part of a Special Issue entitled: Stress, Emotional Behavior and the Endocannabinoid System.
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Adolescence is a developmental period when many teenagers first drink alcohol and often engage in binge drinking. Early onset of alcohol is linked to increased risk of stress-related disorders in adulthood in humans, suggesting that alcohol may interfere with development of the stress regulatory system. We investigated the effect of voluntary alcohol exposure on corticotropin-releasing factor (CRF) peptide-producing cells in the central nucleus of the amygdala (CeA) in adolescent male and female rats. ⋯ In both males and females, alcohol self-administration reduced the number of CRF-ir cells in the CeA compared to control conditions in which rats self-administered equivalent levels of sweetened water that did not contain alcohol. Reduced peptide labeling was not observed in the bed nucleus of the stria terminalis, indicating regional specificity of these changes. Alterations within the CRF cell population of the amygdala may have important implications for susceptibility to alcohol and stress disorders during adolescence and later on in life.