Neurotransmitters are either excitatory or inhibitory. Serotonin (5-hydroxytryptamine, 5-HT) is a neurotransmitter in the brain. Serotonin (5-hydroxytryptamine or 5-HT) is a monoamine neurotransmitter synthesized in serotonergic neurons in the central nervous system and enterochromaffin cells in the gastrointestinal tract. Serotonin is believed to play an important part of the biochemistry of depression, bipolar disorder and anxiety. It is also believed to be influential on sexuality. The name "serotonin" is something of a misnomer and reflects the circumstances of the compound's discovery. This agent was later chemically identified as 5-hydroxytryptamine (5-HT) and as the broad range of physiological roles were elucidated, 5-HT became the preferred name in the pharmacological field.