Relationship between brain-derived neurotrophic factor and stress in saliva and salivary glands

ObjectiveThe nerve growth factor (NGF) family comprises of NGF, brain-derived neurotrophic factor (BDNF) and neurotrophins (NTs)-3 to -7, all of which are collectively referred to as NTs. However, the expression of NTs other than NGF in the salivary gland has not been described in detail. BDNF is a well-studied NT involved in the neurogenesis, differentiation, and maintenance of select peripheral and central populations of neuronal cells during development and adulthood. NTs, in concert with the hypothalamic–pituitary–adrenal (HPA) axis, play key roles in modulating brain plasticity and behavioral coping, especially during ontogenetically critical periods, when the developing brain is particularly sensitive to external stimuli. Early life events, such as psychophysical stress, affect BDNF levels, and induce dysregulation of the HPA axis, thereby affecting brain development and contributing to inter-individual differences in vulnerability to stress or psychiatric disorders. Immobilization stress modifies BDNF mRNA expression in some organs.ResultsWe studied the effect of immobilization stress on BDNF and its receptor, tyrosine receptor kinase B (TrkB), in rat submandibular glands, and found increased BDNF expression in duct cells under immobilization stress. In addition, stress increases the amount of plasma BDNF derived from the submandibular gland, and the amount of TrkB receptor mRNA in the adrenal medulla.ConclusionsPlasma BDNF might therefore activate TrkB receptors in the adrenal medulla during acute stress. The salivary glands are also likely to influence not only oral health, but also systemic organs. This review addresses the relationship between BDNF and stress in the saliva and salivary glands.