Resea R ch highlights CHE m OSENSAt ION the most likely sites for the detection of chemostimuli. The GG cells were ensheathed by glial cells and were located underneath a keratinylated epithelium, which lines Alarm pheromones are secreted to the nasal cavity and is permeable to signal danger to conspecifics, but water-soluble substances. how mammals detect them has To identify the GG stimuli, the remained unknown. Now Broillet authors added different chemical and colleagues have identified the stimuli to a solution with which GG Grueneberg ganglia — located at tissue slices were perfused during 2+ the tip of the nose — as the alarm- Ca -imaging experiments. Alarm detection system in mice. pheromones collected from stressed Grueneberg ganglia (GG) were animals were the only stimulus tested first described approximately 20 that activated GG cells. This activa- years ago and have recently been tion was observed in slices obtained recognized as an olfactory subsystem: from both newborn and adult mice. on each side of the nose, a bundle To test the behavioural role of the of axons from 300–500 GG cells GG, axonal projections from the GG projects to the olfactory bulb. To were severed in pups. When exposed investigate the structure and function to alarm pheromones 30 days after of the GG, the authors used a mouse surgery, the mice did not show the strain in which all olfactory neurons, freezing behaviour that is seen in including GG cells, were labelled control mice. with green fluorescent protein (GFP). As GG...