Why We Feel Nauseous

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Researchers say queasy lab rats could teach us a thing or two about nausea, a common but poorly understood sensation.

"We know about vomiting. The vomiting reflex is very well characterized, but the experience of nausea is something that little is known about," Linda Parker, a psychologist at the University of Guelph in Ontario, said in a statement. "How is it generated? Where is it generated?"

By studying the minds of nauseous lab rats, Parker and her colleagues found the mechanism that is responsible for nausea in the rat brain, which could hold clues about the experience in humans.

Although they don't vomit, rats have a "disgust reaction" called gaping when tasting something that made them feel sick in the past. In the study, published this week in Journal of Neuroscience, the researchers first showed that taking away serotonin in the entire insular cortex — a site of taste and illness input in the brain — stopped the gaping reactions in rats.

The scientists then gave the rats drugs that either activated serotonin-3 receptors or blocked serotonin-3 receptors in specific parts of the insular cortex. They found that in the visceral insular cortex, activating serotonin caused nausea while blocking the brain chemical reduced it.

Many drugs and treatments, such as chemotherapy, come with nausea as an unfortunate side effect. The researchers hope their study will lead to a better understanding of the sensation in humans and eventually lead to a way to control nausea.

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