Neuroendocrine aspects of adaptation

This chapter discusses the interplay among glucocorticoids and the important neuromodulatory peptide, vasopressin, and the involvement of these neuroactive substances in the process of adaptation. Neural plasticity is characterized by adaptation of neurochemical, neuroanatomical, and behavior systems. Adaptations to environmental stimuli are alterations in the responses of individual and complex ensembles of neurons, which lead to long lasting changes in their functional capabilities. The endocrine system plays an important role in this type of adaptation by acting as a signaling network that triggers both chemical and morphological changes in select populations of neurons and glial cells. The hippocampus responds to glucocorticoids both during the diurnal cycle and in response to stress. Among other effects, results of glucocorticoid actions during the diurnal cycle modify synaptic efficacy within a hippocampal system that is involved in learning and memory and is also influenced by the neuropeptide, vasopressin. A common site of vasopressin and glucocorticoid action is the noradrenaline-stimulation of cyclic AMP formation.