The salivary glands produce various substances and secrete them as saliva to maintain the function of the oral cavity.The secreted saliva is swallowed, but when it is absorbed from the lower part of the tongue, it is sent to the whole body without being metabolized by the liver, so the drug is highly effective and immediate.The research group confirmed that when brain-derived neurotrophic factor (BDNF), a protein substance important for maintaining the function of nerve cells, is administered from the lower tongue, it is transferred to the entire brain.However, the functional significance of BDNF produced in the salivary glands was unclear.The research group has previously reported that BDNF increases during stress in the salivary glands and is an important organ that increases blood BDNF levels.

　This time, we developed a mouse that highly expresses BDNF in the salivary glands and analyzed its characteristics.As a result, a slight increase in blood BDNF and total BDNF in the hippocampus in the brain was observed, and anxiolytic behavior was shown in the elevated cross maze and open field test.That is, salivary gland BDNF increases the amount of BDNF in the hippocampus after transfer to blood, which increases glutamate decarboxylase (GAD1) ​​and further from glutamate to the inhibitory neurotransmitter γ-aminobutyric acid (GABA). It was found that the production of) increased and anti-anxious behavioral changes occurred, and the functional significance of saliva BDNF was clarified for the first time in the world.

　This study presents a whole new concept that the salivary glands, which are close to the brain, are organs that affect the brain.In the future, the salivary gland-brain organ network will be elucidated and the relationship with brain function and psychiatric disorders will be investigated.

Paper information:[International Journal of Molecular Science] Salivary Gland Derived BDNF Overexpression in Mice Exerts an Anxiolytic Effect