Scientists discover among a handful of sensory neurons, two types are dedicated to specific respiratory functions, which may suggest new ways of considering clinical conditions related to the vagus nerve.

The team, led by Stephen Liberles, Harvard Medical School associate professor of cell biology, has effectively deconstructed the vagus nerve, a key connection between body and brain that is important because it controls not only breathing but also heart rate, feeding behavior and responses to illness.

Using genetic tools to activate these two neuron types with light, the scientists found that stimulating one neuron type caused mice to stop breathing completely, trapping them in a state of exhalation. Activating the second neuron type made the mice take rapid, shallow breaths, as if they had inhaled some kind of irritant to their lungs, hinting at a pulmonary defense mechanism.

This research shows that because the vagus nerve is not one uniform structure, cutting or stimulating all of it to treat certain conditions may not be the best choice. Vagal nerve stimulation is nevertheless widely used clinically to treat a range of conditions, from epilepsy to mood to obesity. Targeting particular subsets electrically or pharmacologically may bypass clinical side effects.

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