In Vivo imaging study for the regulation of salivary gland functions is a project that ran from 2011-15 and sought to shed light on the regulatory mechanisms of salivary secretions. It was led by Dr Akihiko Tanimura and co-investigator Akihiro Nezu from the Health Sciences University of Hokkaido, Japan. The article discusses the background of the project, the research undertaken and some of the key findings. Xerostomia, also known as dry mouth, is caused by reduced or absent saliva flow. It usually presents as a symptom of medical conditions, a side effect of medications or of radiation to the head and neck. It affects dental and psychological health and can cause issues such as a burning sensation, difficulty swallowing and speaking, and gum disease and tooth loss. The muscarinic acetylcholine receptor (mAChR) is what mediates normal salivary function, with stimulation of this receptor increasing Ca2+ concentrations in salivary cells, and resulting in the salivary secretions. ?Tanimura and his team are endeavoring to provide insight into the hidden functions of Ca2+ responses in salivary cells: ‘Ca2+ have been thought to be the major intracellular messenger for the salivary fluid secretion, though the precise role of Ca2+ is still unknown’ he explains. ‘Our in vivo Ca2+ imaging provides direct links between Ca2+ responses and salivary secretions, and leads us to examine the direct and indirect effects of chemical compounds, candidates of therapeutic medicine, on the salivary cells and salivary secretions.' The researchers are also succeeded in monitoring Ca2+ responses with direct action of parasympathetic nervous through the stimulation of the lingual nerve in rats. ‘It is also possible we would be able to expand this method for studying salivary secretions with physiological stimuli including testes, oral sensations, and conditional reflections,’ highlights Tanimura. ‘Our in vivo Ca2+ imaging and real time monitoring of salivary secretion are more sensitive than traditional methods, and we are trying to find unknown mechanisms, Ca2+-dependent and -independent, for regulating salivary secretion. The researchers unearthed surprising findings in the form of the tissue-wide synchronization of Ca2+ oscillations with the perfusion of acetylcholine. Results also suggests the possibility that the activations of mAChR enhance salivary secretions with some changes in gene expression.