Maturation of the adrenocortical stress response: neuroendocrine control mechanisms and the stress hyporesponsive period.

During the first two weeks of life rat pups show a markedly reduced adrenocortical response to stress, and this period of adrenocortical quiescence has been termed the 'stress non-responsive period' (SNRP). The adaptive value of the SNRP can be understood in terms of the effects of glucocorticoids on CNS development: excessively high or low corticoid levels are associated with abnormal neural and behavioral development. We have attempted to explain adrenocortical activity during this period in terms of the unique pattern of glucocorticoid-receptor concentrations that exist in the brain and pituitary of the neonatal rat. This pattern of receptor concentrations results in a negative-feedback condition at the level of the brain and pituitary that ensures the low, stable corticoid levels that appear to be optimal for neuronal development in glucocorticoid-sensitive brain regions.