NMU triggered calcium flux remains intact in splenocytes lacking all known NMU receptors. Splenocytes from C57BL/6 mice (black) or mice lacking NMUR1, NMUR2 and NTSR1 (red) were loaded in vitro with the calcium sensitive dye Indo-1 and then stimulated with NMU at the 60 second timepoint at the indicated concentrations. Intracellular calcium flux was measured with flow cytometry and is plotted as the ratio of fluorescence emission at 405 nm (bound Indo-1) to fluorescence emission at 495 nm (free Indo-1) over time. Data are representative of three independent experiments. NMU: neuromedin U.