What percentage of serotonin receptors are located in the gastrointestinal tract?

The correct choice reflects the fact that approximately 90% of the body's total serotonin is found in the gastrointestinal tract. This high concentration of serotonin in the gut is primarily involved in regulating intestinal movements, promoting peristalsis, and facilitating communication between the gastrointestinal system and the central nervous system. The presence of serotonin receptors in the gastrointestinal tract highlights the significant role of serotonin beyond its well-known function in mood regulation within the central nervous system. This connection establishes important implications for understanding gastrointestinal disorders and their potential psychiatric links, emphasizing the interconnectedness of both systems in health and disease.