Dopamine has important functions mainly in the brain but also in other parts of the body.
Functions of dopamine in the brain
The brain includes several pathways called dopamine pathways, facilitating the activities of this chemical in the brain.
Some of the important activities are
- Behavior motivated by reward. An increase in reward increases dopamine levels in the brain. This is commonly found in various kinds of addiction.
- control of different hormones in the body
- Control of motor activity.
Functions outside the brain
Here it acts as a messenger causing changes in local chemicals.
Some examples are:
- Dilatation of the blood vessels and reducing hypertension– Dopamine, by reducing norepinephrine, which causes constriction of blood vessels, effectively reduces blood pressure.
- Increases urine excretion and the amount of sodium excreted with urine as well.
- Diminishes insulin production. While these are some of the more important functions, dopamine can affect practically any part of the body.
Effects of changes in dopamine levels — Dopamine, as we know, serves several important functions in the body.
Therefore any change in its levels can cause many problems like:
- Parkinson’s disease, this is caused by dysfunction of dopamine pathways. It is most commonly treated with the precursor of dopamine, L-dopa.
- Some psychotic conditions like depression and schizophrenia are attributed to altered levels of this chemical. The anti-psychotic drugs are aimed at reducing dopamine activity.
- In certain conditions like ADHD, small doses are used for treatment.
Therefore, it is important that an optimal amount of dopamine is synthesized in the body for preventing such diseases and for maintaining good health.
How is dopamine available?
It is available in many food items. However, this is not of much use to the body. This is because, dopamine so available, cannot cross blood-brain barrier. It is therefore not available for maintaining the dopamine pathways. So dopamine has to be synthesized in the brain itself.
What is involved in dopamine synthesis?
- Dopamine can be synthesized from L- tyrosine directly. Tyrosine is a non-essential amino-acid. It is abundantly present in most protein foods. In fact dopamine itself also is quite freely available. But because it cannot enter the brain from the blood, it has to be synthesized inside the brain itself.
- Dopamine can also be indirectly formed from L-phenylalanine. This is first converted into L-tyrosine, which is then converted to L-dopa, and then to dopamine.
- Dopamine can be further converted into other compounds like nor-epinephrine, and also act through these chemicals.
- Several enzymes help in the different stages of synthesis of dopamine, as well as its further transformation and degradation.
- Finally, dopamine becomes metabolically inactive by reacting with some enzymes, broken down and eliminated from the body. However, sometimes, it combines with oxygen and results in formation of free radicals. These are harmful substances, which affect different cells of the body, resulting in disease.
Dopamine is an important chemical neuro-transmitter of the body. A 3 step process is involved in dopamine synthesis from its precursor, tyrosine. Too much of dopamine like in schizophrenia, or too little as in Parkinson’s disease, can both be detrimental to health. Therefore, it is important that dopamine pathways as well as the processes involved in its synthesis should function well in order to maintain health at all times.