Final answer:
NK1 antagonists work by blocking the neurokinin 1 (NK1) receptor, preventing substance P from activating it and therefore reducing its physiological effects.
Step-by-step explanation:
The mechanism of action (MOA) of NK1 antagonists involves the inhibition of the interaction between substance P (a neuropeptide) and the neurokinin 1 (NK1) receptor. By blocking this receptor, NK1 antagonists decrease the activity of substance P, which is implicated in various physiological processes, including pain perception, mood regulation, and vomiting. Thus, NK1 antagonists are useful in preventing chemotherapy-induced nausea and vomiting (CINV) and may have potential applications in treating mood disorders and pain.