Monoamines transmit signals from a neuron to a cell. Monoamines are either catecholamines or indolamines. Catecholamines operate in the sympathetic and central nervous systems. Indolamines consist of serotonin and are spread throughout the body's tissues. 

Dysfunction of monoamines can lead to neurological symptoms related to the transport of dopamine, norephinephrine, epinephrine, and serotonin.