Catecholamines

Catecholamines are derived from the amino acid tyrosine and share a catechol nucleus (a benzene ring with two hydroxyl groups).

Dopamine: A neurotransmitter involved in reward, motivation, memory, attention, and regulation of body movements. It is synthesized in the brain and is crucial for the pleasure and reward system.

Norepinephrine (Noradrenaline): Acts both as a hormone and a neurotransmitter. It is involved in the body’s fight or flight response, regulating arousal and alertness, and increasing heart rate and blood pressure.

Epinephrine (Adrenaline): Primarily a hormone but also acts as a neurotransmitter. It plays a critical role in the fight or flight response by increasing blood flow to muscles, output of the heart, pupil dilation, and blood sugar level.

Indolamines

Indolamines are derived from the amino acid tryptophan and include compounds that contain an indole ring.

Serotonin (5-HT): A neurotransmitter that contributes to feelings of well-being and happiness. It regulates mood, appetite, sleep, memory, and learning. Serotonin is also involved in various physiological functions such as cardiovascular regulation and endocrine secretion.

Melatonin: A hormone produced by the pineal gland that regulates sleep-wake cycles. It is derived from serotonin and helps control the body’s circadian rhythms.

Trace Amines

These are naturally occurring, endogenous amines that are present in the body in trace amounts.

Tyramine: A naturally occurring monoamine derived from the amino acid tyrosine. It can influence blood pressure by causing blood vessels to constrict.

Octopamine: Found in trace amounts in mammals, it is more prominent in invertebrates. It is involved in regulating behaviors such as locomotion and feeding.

Other Monoamines

These monoamines do not fall neatly into the above categories but play important roles in the body.

Histamine: Involved in local immune responses and regulating physiological functions in the gut as well as acting as a neurotransmitter. It plays a key role in the inflammatory response and has a part in regulating sleep-wake cycles and gastric acid secretion.