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What Are Monoamines?

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  • Written By: Kathy Dowling
  • Edited By: A. Joseph
  • Last Modified Date: 28 September 2014
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"Monoamines" is a term used to describe neurotransmitters that act to transmit signals of a nerve or neuron to a cell. They play a significant role in the metabolism or processing of the brain and elicit many different behaviors. Monoamines fall under two categories — catecholamines and indolamines — and within each class are different neurotransmitters. Catecholamines consist of neurotransmitters such as epinephrine, norepinephrine and dopamine, and indolamines include the neurotransmitter serotonin.

Chemical substances called catecholamines are created within the body from amino acids such as phenylalanine and tyrosine. Amino acids are a vital building block for proteins within the body. Proteins are produced within the human body by 20 different amino acids, nine of which have been classified as "essential" or indispensable amino acids. They are given this label because the body alone is unable to produce them but is very dependent upon them. These amino acids are provided to the body via food.

Catecholamines are a class of monoamines consisting of epinephrine, norepinephrine and dopamine. These neurotransmitters usually operate within the sympathetic and central nervous system and have many different roles. Under a microscope, the chemical structure of a catecholamine consists of a benzene ring with amine and hydroxyl side chains.

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Epinephrine is released from the adrenal glands and stimulates the sympathetic nervous system, creating feelings such as excitement, shock and fear. Norepinephrine is the precursor of epinephrine and functions to mediate the signaling of such nerve impulses. Dopamine is the precursor of norepinephrine. The greatest concentration of dopamine is found within the basal ganglia, an area of the brain involved in regulating subconscious voluntary movement.

Indolamines are another class of monoamines and consist of the neurotransmitter serotonin. This chemical substance is extensively spread throughout the body's tissue. It is particularly found within the brain, in the lining of the gastrointestinal tract and in platelets located in blood. Serotonin has the role of controlling states of consciousness and mood, and it functions to inhibit gastric secretions from the gastrointestinal tract.

Monoamines are neuromodulators, which means they are able to stimulate many neurons that are located far away from each other. As a result of this, monoamines are able to produce many different behavioral outcomes. Monoamines are broken down by naturally occurring enzymes called monoamine oxidases (MAOs).

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aviva
Post 3

Monoamine Oxidase Inhibitors (MAOI) do an excellent job at preventing the oxidase from destroying the neurotransmitters, but it can create some potentially dangerous side effects as well. You can't take this drug with some over the counter cold medicines or with certain foods.

Here is a small list of monoamine oxidase inhibitors names and the type of medication it's commonly found in. Amphetamine and dextroamphetamine used to treat ADHD. Eye drops with decongestants, Isometheptene found in Migranal, Meperidine found in Demerol, Methylphenidate which is Ritalin, Naphazoline and Oxymetazoline found in nasal sprays, phenylephrine is a decongestant found in cold products and Pseudoephedrine which is a nasal decongestant.

If you or someone you know is taking an MAOI as an antidepressant or for any other reason, please read the labels before taking any other medications as it could be fatal to combine two or more of these inhibitors at the same time.

Markus
Post 2

@goldensky - I had a teacher explain the monoamine oxidase inhibitors role to me once like this.

Think of the monoamine neurotransmitters as mail carriers. Think of the monoamine oxidase as a big mean dog trained to stop the mail carrier dead in his tracks.

Now think of a monoamine oxidase inhibitor as a big dog bone. Once the bone (inhibitor) has been administered, the dog, (monoamine oxidase) is calm and quiet so the carriers (neurotransmitters) can go about doing their job.

I know that sounds like a childish explanation, but it works and I guess that's why I remembered it after all these years.

goldensky
Post 1

I'm a bit confused by the last paragraph in the article about the monoamine oxidase inhibitors. I mean I understand what monoamine neurotransmitters are and their function at delivering information, but are the monoamine oxidases purpose? Can anyone clarify this please?

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