Do the serotonergic agents alosetron and tegaserod affect serotonin receptors outside the ENS?

Lawrence Schiller MD  

Serotonin receptors are located throughout the body. About 95% of them are located in the enteric nervous system and about 5% are in the brain. They have important functions in both areas.

However, the 5-HT3 receptor antagonist alosetron and the 5-HT4 receptor agonist tegaserod are limited in their ability to get into the brain because of their chemical structure. And so they mainly affect the 5-HT3 and 5-HT4 receptors in the gut. Those receptors are important for the regulation of peristalsis and thus the main effect that we see with these drugs is on peristalsis and not in other functions elsewhere in the body.