Vomiting can be elicited by many stimuli including gastrointestinal irritation/inflammation, circulating toxins, cancer chemotherapy, and provocative motion. Stimulation may be peripheral, triggering vagal or sympathetic afferent neurons, or central, stimulating neurons in the chemoreceptor trigger zone (CTZ). The emetic center is located in the medulla oblongata and includes the nucleus tractus solitarius (NTS) and dorsal motor nucleus of the vagus. The NTS lies within the blood brain barrier (BBB), so to be an effective antiemetic, a compound must be able to cross the BBB. Neurokinin type 1 (NK1) receptors are one type of neurotransmitter receptor and it has been shown that selective antagonism of the NK1 receptors inhibits emesis. The controlled study reported in this article evaluated the use of a central NK1 receptor antagonist, maropitant (Cerenia, www.pfizer.com), in a known experimental model using gerbils. A gerbil foot-tapping model was used to investigate the in vivo functional activity of maropitant and its ability to penetrate the central nervous system and inhibit foot tapping induced by the selective NK1 agonist GR73632.

The neurokinin-1 antagonist activity of maropitant, an antiemetic drug for dogs, in a gerbil model.
de la Puente-Renondo V, Tingley FD, Schneider RP, Hickman MA. J VET PHARMACOL THER 30:281-287, 2007.