Nausea is an uneasiness of the stomach that more times than not come before vomiting. Nausea can be a symptom of a host of conditions such as motion sickness, morning sickness during pregnancy, emotional distress, brain injury, cancer or even medications. In contrast to vomiting, nausea has not been well understood, until now.

Researchers from the University of Guelph, Ontario, have discovered the mechanism responsible for feeling nauseous.

"We know about vomiting. The vomiting reflex is very well characterized, but the experience of nausea is something that little is known about. How is it generated? Where is it generated?" said Professor Linda Parker of the Department of Psychology.

Though rats cannot vomit, they do demonstrate similar nauseated actions called gaping. With the help of the gaping model, Katharine Tuerke, PhD student, University of Toronto Professor Paul Fletcher, neuroscience researcher Cheryl Limebeer and Professor Parker, uncovered that serotonin may be responsible for the nausea sensation.

Serotonin, released in the visceral insular cortex, may cause this particular feeling. The insular cortex is the region of the brain responsible for taste and illness. The insular cortex can be classified into two regions: the gustatory insular cortex and the visceral cortex. The gustatory insular cortex receives taste inputs whereas the visceral insular cortex receives input from regions of the stomach that may produce the sensation of nausea.

Additionally, researchers also observed the effects of medication that either activates or block serotonin receptors. In the visceral insular region, activating serotonin will cause nausea, whereas blocking serotonin reduces nausea.

Prior research has only demonstrated neurotransmitter serotonin is essential for the production of nausea.

Researchers hope these findings will lead to a better comprehension of the neural process that may be affected by prescribed medications. They believe targeting serotonin will lead to controlling nausea and vomiting caused by cancer chemotherapy.

The study was published in the Journal of Neuroscience.