This document discusses serotonin, its receptors, and drugs that affect the serotonin system. Serotonin is a neurotransmitter found in the gastrointestinal tract and central nervous system that regulates mood, sleep, and body temperature. It acts through various receptor subtypes (5-HT1-7) located on neurons and other cells. Drugs that affect serotonin include selective serotonin reuptake inhibitors for depression, triptans for migraine, cisapride for gastrointestinal issues, and antagonists for conditions like nausea. Serotonin receptors and their roles are important targets for psychotherapeutic drugs.