Bulgarian Journal of Psychiatry, 2021; 6(2):14-23
STRESS IN BRAIN – FOCUS ON HIPPOCAMPUS, AMYGDALA AND THEIR CONTROL ON BEHAVIOR
Bogomil Peshev, Vasya Vutova, Vihra Milanova
Clinic of Psychiatry, UMHAT „Alexandrovska“ – Sofia
Stress could be described as an active or unpredictable change in organismic homeostasis due to internal or external factors known as stressors. This change is followed by a process of adaptation to the given set of stressors termed allostasis and characterized by complex interactions between multiple systems: nervous, endocrine, immune ones, etc. Stressors are further subdivided into physical (pain, inflammation, blood loss) and psychological (stimuli from the environment which are interpreted in accordance with the individual’s prior experience). The limbic system of the brain, the hippocampus, and the amygdala in particular, are all involved in the regulation of two stress responses: 1) the rapid “fight or flight” response that is marked by the increased secretion of adrenaline from the medulla of the adrenal gland due to the activation of the sympathetic nervous system, and 2) the slower recovery, neuroendocrine response based around the activity of the hypothalamic‐pituitary‐adrenal axis and leading to increased secretion of cortisol (corticosterone in animals). Stress is a key factor in the development of anxiety disorders (F41, IDC10) like panic disorder (F41.0) or mixed anxiety and depressive disorder (F41.2), and adjustment disorders due to severe stress (F43, ICD10) like post traumatic stress disorder (F43.1). This short review is dedicated to discussing the effect of stress on the morphology and functionality of the hippocampus and the amygdala, and by doing so, it intends to bridge the laboratory studies from the field of neurobiology with the knowledge about the role of stress in the above‐mentioned psychopathologies emerging from the field of psychiatry. It is important to note that while the publications outlined here are only a small part of the existing literature, the current paper is a suitable starting point for a more detailed investigation of what is known about the regulation of stress responses and the pathobiological causes for the maladaptive behaviors related to anxiety disorders.
Key words: stress, anxiety, hippocampus, amygdala, glucocorticoids, adult neurogenesis