What is the function of ENS-based serotonin receptors?

Lawrence Schiller MD  

There are several different serotonin receptors that are located in the enteric nervous system. The two main ones are the 5-HT3 receptors and the 5-HT4 receptors. These receptors pick up serotonin from the surrounding environment and cause the nerve cell to discharge or make the nerve cell less likely to discharge. As a result of that, the enteric nervous system is either stimulated or depressed.

Serotonin is released from the enterochromaffin cells that are part of the lining cells in the intestine. And those cells, when they're stimulated, will release serotonin and interact with the 5-HT3 and the 5-HT4 receptors on the enteric nerves. They will cause various effects. The 5-HT3 receptors and the 5-HT4 receptors that are on the sensory nerves will then cause that nerve to discharge onto the inner neuron. And from there, the signal will go to the various motor neurons that will affect gut function, either to stimulate or to suppress peristalsis.

The 5-HT3 receptors tend to cause the gut to react in a way that will produce diarrhea. And so blocking those receptors tends to mitigate diarrhea and slow peristalsis. The 5-HT4 receptors, because they cause the release of acetylcholine, tend to stimulate peristalsis, and so stimulating the 5-HT4 receptors will stimulate peristalsis.