Nothing is worse than eating spoiled food, feeling a wave of nausea and then spending the next 15 minutes vomiting in the bathroom. We know that the reason for vomiting is the body’s defence mechanism to reject potential toxins. Still, scientists had not fully understood how messages from the gut reach the brain , triggering the reaction. A study by a team of Chinese scientists, published on Tuesday in the peer-reviewed journal Cell, mapped the neural pathways in mice that detailed what happens when the stomach registers bad food and when our brain tells other parts of the body to puke . “Details about how the signals are transmitted from the gut to the brain were unclear because scientists could not study the process on mice,” said Peng Cao, a study author, in a press release, referring to the fact that mice do not vomit. However, mice do retch, opening their mouth and contracting their stomach, which Cao said is similar to the human urge to vomit but just expressed differently. The team of scientists gave the mice a bacteria that also causes human vomiting, which worked consistently in inducing retching, allowing the team to study the brain’s defence mechanism against the toxin. They discovered that when the mice’s stomachs came in contact with the bacteria, they released serotonin, a chemical that carries messages across the body’s nervous system. The serotonin then binds to sensory neurons located in the intestine, and a signal is transmitted across the body to a specific type of neuron in the brainstem called Tac1+DVC. That neuron appears to trigger the vomit reflex because when the team of scientists deactivated the Tac1+DVC neurons in the mice, the animals retched significantly less often. “With this study, we can better understand the molecular and cellular mechanisms of nausea and vomiting, which will help us develop better medications,” Cao says. To the point about medicine, the team also investigated whether mice retched less from a type of chemotherapy medicine after their Tac1+DVC neurons were blocked. They found that they did. Cao said this is why some chemotherapy anti-nausea medications work: they can effectively block serotonin receptors that trigger the vomiting process. Ideally, he said, if we can better understand why the brain reacts in specific ways to expel toxins, we can more precisely develop medicines to solve problems. The team wants to continue studying how the brain reacts to certain pathogens, and Cao brought up the example that we do not know the specifics about why we cough when trying to expel the coronavirus.