The Interacting Neuroendocrine Network in Stress-Inducing Mood Disorders

Abstract

Extensive research studies showed the existing interaction between different systems of the body that maintain the stability of homeostatic processes and which allow species to adapt to its environment in response to stressors. Adaptive responses to stressors activates adaptive-mechanisms, that result in the synthesis and release of several brain neurotransmitters, peptide hormones, proinflammatory cytokines and adrenal steroids from neural, neuroendocrine and immune cells which prepared the organism to alert its systems to adopt the proper behavioral responses against stressful events. Neurotransmitters, peptide hormones and cytokines act through the HPA axis forming a regulatory loop that maintains homeostasis in response to different stressors. One route to understand the interactions between brain transmitters, neurosecretory peptide-hormones, adrenal steroids and immune-borne cytokines, including neurotrophic factors is when bodys systems and chemical communication between cells appear to be disrupted during stressful events as occurs in mood-related disorders and depression. Thus, this review will described the functional interactions between HPA axis activity and the projecting neural pathways (DRN-5HT neurons; LC-NA neurons) and brain neurotransmitters (NE, 5-HT, DA, GLU) that impinge on forebrain-limbic structures (hypothalamus, hippocampus, mPFCx) that drive the release of the CRH and CRH-dependent secretion of ACTH from anterior hypophysis and cortisol from adrenal glands, under stressful conditions. Moreover, interactions between immune-borne cytokines and HPA axis activity, and glucocorticoid receptors have been shown to be extremely important to understand the pathophysiological mechanisms that operate in mood-related disorders and MDD, including the stress-inducing altered changes in brain morphology, neuronal atrophy and neurogenesis in brain areas involved in learning processing and memory functions.