Stress adaptation is of utmost importance for the maintenance of homeostasis and,
therefore, of life itself. The prevalence of stress-related disorders is increasing,
emphasizing the importance of exploratory research on stress adaptation. Two major
regulatory pathways exist: the hypothalamic-pituitary-adrenocortical axis and the
sympathetic adrenomedullary axis. They act in unison, ensured by the enormous bidirectional
connection between their centers, the paraventricular nucleus of the hypothalamus
(PVN), and the brainstem monoaminergic cell groups, respectively. PVN and especially
their corticotropin-releasing hormone (CRH) producing neurons are considered to be
the centrum of stress regulation. However, the brainstem seems to be equally important.
Therefore, we aimed to summarize the present knowledge on the role of classical neurotransmitters
of the brainstem (GABA, glutamate as well as serotonin, noradrenaline, adrenaline,
and dopamine) in stress adaptation. Neuropeptides, including CRH, might be co-localized
in the brainstem nuclei. Here we focused on CRH as its role in stress regulation is
well-known and widely accepted and other CRH neurons scattered along the brain may
also complement the function of the PVN. Although CRH-positive cells are present on
some parts of the brainstem, sometimes even in comparable amounts as in the PVN, not
much is known about their contribution to stress adaptation. Based on the role of
the Barrington's nucleus in micturition and the inferior olivary complex in the regulation
of fine motoric-as the main CRH-containing brainstem areas-we might assume that these
areas regulate stress-induced urination and locomotion, respectively. Further studies
are necessary for the field.
