Dopamine is one of many neurotransmitters of the brain. This is a catecholamine neurotransmitter and it is capable of activating five types of dopamine receptors (D1, D2, D3, D4 and D5 receptors). Dopamine can be synthesized in more than few parts of the brain. It is generally produced in the substantia nigra and the ventral tegmental area. This neurotransmitter is also produced by the hypothalamus. The most important function of dopamine is to act as antagonist of the release of prolactin from the pituitary gland.
Some people may suffer from certain illnesses and they require increase in the amount of dopamine in their brains. This is the case with patients suffering from Parkinson's disease or dopa-responsive dystonia. Even though dopamine is available in a form of intravenous medications, this particular form simply cannot be directly transferred to the central nervous system. So, in order to increase the amount of dopamine in the brain this particular group of patients receives L-DOPA, the precursor of dopamine.
What are Functions of Dopamine?
Dopamine is an essential neurotransmitter which regulates behavior and cognition. It is also connected with motivation, reward and voluntary movement. Several more functions of dopamine are associated with sleep, attention, mood, learning as well as inhibition of prolactine production. Learning new behavior is only possible if specific parts of the brain are signaled by dopamine.
Dopamine is related to motivation and a felling of pleasure. For example, if we eat our favorite food, we feel good. This particular feeling occurs due to dopamine. Food and sexual activity are both triggers for the release of dopamine.
Furthermore, our motivation depends on dopamine. Dopamine also controls movements and it is engaged in signaling of error in the prediction of reward and cognition. Scientists say that if we expect a reward, dopaminergic neurons fire this neurotransmitter as a motivating substance.
And finally, dopamine is in charge with transmission of information from different parts of the brain to the frontal lobe. This is why if there is a lack of dopamine in the pre-frontal cortex a person may suffer from attention deficit disorder.
Pathways of Dopaminergic Neurons
Neural pathways are essential for transmission of dopamine from one region of the brain to another. In human brain there are four major dopaminergic pathways: mesolimbic pathway, mesocortial pathway, nigrostriatal pathway and tuberoinfudibular pathway. All of them are in charge with adequate transmission and function of dopamine. In mesolimbic pathway the neurotransmitter is transferred from the midbrain, ventral tegmental area to the nucleus accumbens in the limbic system. Mesocortical pathway provides with transmission of dopamine from the VTA to the frontal cortex. In nigrostriatal pathway dopamine is transferred from the substantia nigra to striatum. Dysfunction or degeneration of this particular pathway results in Parkinson's disease. And finally, in tuberoinfudibular pathway dopamine is transferred from the hypothalamus to the pituitary gland.