Abstract
Nausea and vomiting (emesis) occur under a variety of conditions in response to activation of one or more emetic triggers, such as abdominal visceral, cardiac and vestibular nerve afferents, the area postrema chemoreceptor trigger zone in the caudal brainstem, and higher brain centers. The act of vomiting is coordinated by neuronal circuitry located in the brainstem and extending from the nucleus of the solitary tract through the lateral tegmental field of the reticular formation to the ventrolateral medulla. The sensation of nausea is thought to involve the cerebral cortex. The motor act of vomiting is produced primarily by complicated changes in the activity of the respiratory muscles. There are also complex changes in the activity of the gastrointestinal tract, which are mediated by the vagus nerve but are not essential for vomiting. The recently introduced serotonin type 3 receptor antagonists are very effective in combating nausea and vomiting induced by cancer chemotherapy and radiation therapy. More broad based anti-emetic action has been achieved in animal models by using serotonin type 1A receptor agonists and neurokinin type 1 receptor antagonists. Stimulation of the P6 acupuncture point is reported to be effective against motion and pregnancy sickness, and postoperative and cancer chemotherapy-induced nausea and vomiting. Greater understanding of the mechanisms underlying nausea and vomiting and more effective treatments are still required, especially in conditions such as pregnancy sickness, postoperative nausea and vomiting, the delayed phase of vomiting following cisplatin therapy, and cyclical vomiting.
