Monoamines in biochemistry include organic compounds with only one amino group. The most important members in this group are the neurotransmitter group catecholamines (including dopamine, epinephrine, and norepinephrine) and the indoleamine serotonin. Monoamines seem to contribute to stable moods, and an excess or deficiency of monoamines seems to cause or result from several mood disorders.
Monoamines are moved into or out of cells via a class of proteins called monoamine transporters. Antidepressants and psychoactive drugs often affect the monoamine transporters rather than the monoamine itself.
A monoamine neurotransmitter relays, amplifies, and modulates electrical signals between two neurons. MAOIs prevent breakdown of monoamine neurotransmitters, therefore increasing concentrations in the brain. Partly because there are several different monoamine neurotransmitters, general MAOI therapy can be associated with several adverse reactions, including hyptertensive crisis when patients eat high-tyramine foods and take certain drugs. More targeted drugs for specific monoamines, like selective reuptake inhibitors for serotonin, generally work better.
Neurotransmitter effects are defined by the neural receptor, not by the neurotransmitter itself.
- Sythesized endogenously (inside the presynaptic neuron)
- Available in sufficient quantities in the presynaptic neuron to cause some sort of effect to the postsynaptic neuron the neurotransmitter is sent to
- If administered externally (not produced by the body), it must mimic the naturally-produced substance
Among organic compounds, there are six monoamines classified as neurotransmitters in addition to non-monoamines such as acetylcholine, purines, certain fatty acids, and around fifty peptides including some hormones.
The six monoamine neurotransmitters include:
- Dopamine, produced from phenylalanine and tyrosine
- Norepinephrine or noradrenaline
- Epinephrine or adrenaline
- Serotonin, also known as 5-hydroxytryptamine, or 5HT
- Histamine, produced from histidine
Web Resources On Monoamine Neurotransmitters
Complex Chemistry for a Simple Task
Power Point Presentation
Book Resources On Monoamine Neurotransmitters
Quantitative Imaging: Neuroreceptors Neurotransmitters and Enzymes by Frost & Wagner
Monoamine distribution in primate brain by David L Felten