Serotonin is a neurotransmitter produced by the body, the main component of which is 5-hydroxytryptamine, the main product of tryptophan metabolism. Serotonin is an important inhibitory neurotransmitter and intracellular messenger, widely distributed in the body, and closely related to a variety of physiological activities. In the central nervous system, serotonin is usually distributed in the pineal gland and hypothalamus, and is involved in the regulation of physiological functions such as pain and sleep, such as inhibiting pain, promoting sleep, and also causing a sense of pleasure in the brain. Therefore, a deficiency of serotonin may result in symptoms such as somatic conscious pain and insomnia. In peripheral tissues, serotonin is a strong vasoconstrictor and smooth muscle contraction stimulant, involved in gastrointestinal motility as well as the regulation of immune and other functions, such as serotonin can agonize the receptors within the smooth muscle of the gastrointestinal tract, causing contraction of the gastrointestinal tract smooth muscle, accelerating gastrointestinal peristalsis. Clinically serotonin has certain pharmacological effects, such as can be used as an antidepressant drug to help improve and relieve anxiety, depression and other bad mood. It can also be applied as a sleeping drug to people suffering from mild sleep disorders to help relieve insomnia and other conditions. Application should strictly follow the doctor’s instructions, do not blindly self-medication.