My work is focused on two neuropeptides: neuromedin U (NMU) and neuromedin S (NMS). These neuropeptides are regulators of the hypothalamo-pituitary-adrenal axis, which is an important component of the biological stress response system. However, understanding their distinct roles in stress biology is challenging. Therefore, our aim is the direct measurement of in vivo NMU and NMS release following optogenetic stimulation of NMU-releasing neurons. The use of microchip ultrahigh performance liquid chromatography coupled to tandem mass spectrometric detection (LC-MS/MS) will allow us to analyze low concentrations of these two neuropeptides in microdialysis samples.