What is dopamine?

dopamine_chemical_structure

‘The Happy Hormone’ – is it really? I often wonder how a chemical can change the whole way we feel about a situation, and what triggers its release. That is the beauty of Biochemistry – explanation of the complex at a molecular level.

It helps to understand some things about how the body communicates before considering dopamine. (There is some similar information in the Taste Buds post). The nervous system is the body’s communication method. Neurons (nerve cells) go, for example, from your finger to the spinal cord + brain, and then back down to your finger muscle in order to move. The connections between neurons are tiny little gaps called synapses. Neurotransmitters are little chemical packets released from one neuron that travel across the synapse to the receptor cells on the next neuron, stimulating the nervous signal in the next neuron so the information can travel to/from the brain.

Dopamine is a neurotransmitter. It is produced in three places (all slightly long and complicated): the ventral tegmental area (in the frontal lobe of the brain), the substantia nigra pars compacta (near the hypothalamus) and the arcuate nucleus of the hypothalamus. Basal ganglia cells involved in voluntary movement that require dopamine in order to function with efficiency – in fact, a lack of dopamine has been linked to conditions where the patient struggles to control movement, such as Parkinson’s disease, for this reason. Too much dopamine is believed to cause an ‘excess’ of movement, such as in Tourette’s patients.

Rather than being just a chemical that stimulates happiness and helps with movement (as above), dopamine has a wide range of functions. It reacts to unpleasant stimuli as well as rewarding stimuli, suggesting that happy hormone is not quite the right definition. Dopamine has been proven to be produced when a person just thinks about a pleasant stimulus (eg. the smell of freshly baked chocolate cookies), rather than direct stimulation of that stimulus. It is also involved in memory and learning since it controls passage of information in the frontal lobe, sleep and attention.

Another function of dopamine is the inhibition of prolactin, which enables women to produce milk. If dopamine is released from the arcuate nucleus of the hypothalamus, it diffuses into the blood which supplies the pituitary gland. Then, the dopamine causes change in lactotrope cells in the pituitary gland, resulting in a lack of prolactin production.

Drugs can change the effect of dopamine. Normally, once dopamine has been released, it travels back across the synapse to the cell from which it was released, and re-enters the neuron through specific proteins. Cocaine stops the uptake of dopamine, hence the happy feeling and the following addiction. Amphetamines are a similar shape to dopamine, so enter neurons and force dopamine to exit, leading to a feeling of reward.

It is quite amazing that a specific molecular structure (as pictured) can quite drastically change a person’s behaviour, self-perception and muscle ability…

 

Sources:

https://www.youtube.com/watch?v=lIJW9XLDE-I

http://www.news-medical.net/health/Dopamine-Biochemistry.aspx

http://www.news-medical.net/health/Dopamine-Functions.aspx

https://www.psychologistworld.com/biological/neurotransmitters/dopamine.php

 

Image credit: http://elit.umwblogs.org/2012/02/09/dopamine-and-the-neurological-benefits-of-video-games-in-the-classroom/

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