In the wild, mice have developed survival strategies to detect volatile cues that warn them of potential danger. Specific olfactory neurons found in the Grueneberg
ganglion olfactory subsystem can detect alarm
pheromones emitted by stressed conspecifics, as well as
kairomones involuntarily released by their predators. These volatile chemical cues allow intra- and interspecies communication of danger, respectively. Alarm
pheromones,
kairomones and bitter taste
ligands share a common chemical motif containing
sulfur or
nitrogen. Interestingly, three specific bitter taste receptors (TAS2Rs) have been found in the Grueneberg
ganglion neurons that are implicated in danger signalling pathways. We have recently developed a TAS2R-expressing heterologous system that mimics the Grueneberg
ganglion neuron responses after
kairomone stimulation. Here, we demonstrated by in vitro, ex vivo and in vivo experiments that the
biological secretions from the raccoon (Procyon lotor) and the skunk (Mephitis mephitis) were acting as potent sources of
kairomones. They activated the Grueneberg
ganglion neurons and induced fear-related behaviours in mice. Identification of new sources of
semiochemicals is a first step towards an understanding of the interspecies danger communication that takes place in the Grueneberg
ganglion.