Pathophysiology of Opioid-Induced Nausea Nausea may be experienced in many conditions, including pregnancy, seasickness, central nervous system (CNS) diseases, anxiety, and opioid therapy. The sensation is orchestrated by a complex group of sensory inputs, ultimately coordinated by the vomiting center in the lateral reticular formation of the medulla . The nausea is experienced depending on which sensory input is stimulated. The vomiting center is stimulated by neurotransmitters, histamine, and acetylcholine. It acts physiologically as a processing center for all the afferent signals that may elicit nausea. Origins of these afferent signals include the chemoreceptor trigger zone (CTZ), vestibular apparatus, and mechanoreceptors and chemoreceptors that originate from various locations in the gastrointestinal tract and cortex.[11-13] Pharmacotherapy 22(2):240-250, 2002. Remember we are NOT Doctors and have NO medical training. This site is like an Encylopedia - there are many pages, many links on many topics. Support our work with any size DONATION - see left side of any page - for how to donate. You can help raise awareness of CAM.