Background: Serotonin (5-hydroxytryptamine, 5-HT) is a regulatory and biologically active neurotransmitter and a hormone in the CNS and many organs, including the esophagus. It is known that serotonin as well as acetylcholine stimulates contractile activity of the esophageal smooth muscles. However, role of different serotonin receptors in realization of large doses of serotonin in contractile activity of the esophagus is insufficiently known. Aim: To determine receptor mechanisms in realization of large doses of serotonin in contractile activity of the esophagus.