Adaptive and maladaptive regulations in response to environmental stress in adolescent rodents

Abstract

Adolescent mammals exhibit a plethora of age-specific behaviours that mark a discontinuity with earlier stages of life and prepare the individual to the challenges of adulthood. Stress sensitivity during adolescence is remarkably different from earlier and later maturational stages. Specifically, although adolescent and adult mammals mount a similar endocrine response to external stressors, such response is excessively prolonged in adolescents. This unique response profile may relate to an asynchronous developmental profile of the several components of the hypothalamic- pituitary-adrenocortical axis. Experiential factors encountered throughout this period are thus likely to persistently adjust long-term regulations to the adult environment. Such age-specific developmental plasticity entails both risks and opportunities. Whilst being sensitive to external stimulation favours the integration of external cues into the mature function, the latter may result pathologic if inappropriately stimulated. For example, precocious experience with drugs of abuse or exposure to adverse environments may favour the onset of conduct disorders (e.g. Addiction, emotional disturbances). In this chapter we describe the inextricable link between adolescent plasticity and long-term individual regulations both in terms of predisposition to pathology and in terms of adaptive plasticity to the adult environment.