STRESS AND NEUROENDOCRINE PLASTICITY

Stress represents an integral part of every day's life and a number of adaptative responses are activated in order to maintain homeostasis i n the face of a challenging external and/or internal milieu. The neuro endocrine activation plays a pivotal role in these adaptative response through the release of neuropeptides, neurotransmitters and glucocort icoids. Here we focus our attention on two physiological conditions ch aracterized by changes in stress responsiveness and neuroendocrine pla sticity: the period of neonatal development and the period of lactatio n in the adult female. Both periods are intimately linked and neuroend ocrine changes during lactation might be viewed as a protective condit ion insuring the optimal survival and development of the young. We dis cuss changes in stress responsiveness, reproductive functions and emot ionality during lactation as they relate to plastic changes in neurona l responsiveness and morphology. Since the neonatal period in both hum ans and rodents is characterized by intense synapse formation and remo delling, we examine the influence of early stressors occuring during n eonatal life on stress responsivity in neonatal and adult life. These studies should help us define mechanisms, both in the early life perio d and later in adulthood, that keep the stress response under control and also understand the dysregulations of this system occuring in seve ral pathologies like depression and anxiety disorders.