Chapter 4 - Stress-Hyporesponsive Period

Abstract

The development of the mammalian stress system plays a crucial part in shaping its function during adulthood and impacts on stress resilience and the vulnerability to stress-related disorders later in life. In rodents, a critical developmental period is the so-called stress-hyporesponsive period (SHRP), which has been defined by the reduced adrenocortical glucocorticoid secretion following most stress situations. As similar developmental periods also exist in other mammals, including humans, it has been postulated that disruption of the SHRP might be a critical physiological event, triggering long-term adaptation of physiology and behavior. This chapter will discuss the historical development of the concept of the SHRP and the function of the stress system at the different organizational levels during this developmental time period. It will become clear that while the adrenal is indeed relatively quiescent during the first two postnatal weeks in the rodent, higher-order structures as the pituitary or the brain are highly sensitive to external or internal challenges during this time. A key question is therefore how the neonatal stress system discriminates between different stressors and how, if necessary, the hyporesponsiveness of the adrenal can be overcome.