2024-04-25

Variabilities of Dopamine (₯) - Prequel

"Dopamine" in the brain affects many different aspects of our daily life, including regulating emotions, learning, memory and movement. Dopamine in the body is related to the degree of vasoconstriction/relaxation, reduces insulin production when blood sugar is too low, and can also protect the intestinal lining. "She" seems to be our good friend, but not enough dopamine can cause Parkinson's disease, and too much can lead to low blood pressure, hallucinations, impulse control disorders such as addiction, mania, and increased aggression[1]. Once upon a time, the "happy dopamine" in the general population could also make people "extremely happy and sad"?! The prerequisite for in-depth understanding is to first have a glimpse of "her" shaping process in science. This article refers to dopamine in the first person of a woman as a tribute to the first female scientist who discovered it.

Teenage Dopamine (₯): Famous From Disease Research Onwards

Dopamine was "born" outside London in 1957 (the time it was discovered in the human brain). Kathleen Montagu's filter paper chromatography method identified evidence of dopamine in the brains of multiple species, including humans.

Then in 1958, Arvid Carlsson and his colleagues at the Swedish National Heart Institute discovered the function of the dopamine neurotransmitter. Carlson won the Nobel Prize in Physiology or Medicine in 2000 for showing that dopamine is not only a "precursor" of norepinephrine and epinephrine - a compound that precedes another in a metabolic pathway - but is also a "Neurotransmitter" (Figure 1[2]).

Dopamine was unknown in the scientific community before the age of ten. In 1967, a breakthrough was made in the research of levodopa (L-DOPA). In the past ten years, the research boom in brain functions, receptor identification and related pharmacology, antipsychotic drugs, etc. has been accelerated. . Dopamine, who was in her twenties, gradually became famous through academic exploration, and her understanding gradually took shape[3].

If you break down the name of dopamine, "amine" is her "surname". It belongs to catecholamines and phenylethylamine, two organic chemicals in the amine family. "Dopa" is the precursor chemical substance whose "name" is levodopa. Interestingly, "Dopa" is also a natural substance "Dopa" created by the "God ADOPA" in the magical terminology of the Renaissance! (Picture 2[4])

Dopamine(₯) in Female Youth: Spokesperson of Happiness

At the age of 21, dopamine established its most widely circulated identity: "happy hormone" and "happy molecule". In 1978 Roy Wise published a seminal paper showing that dopamine, at least in its role in a circuit near the middle of the brain, is necessary for feeling good. Next, it supports Wise's hypothesis that dopamine is a "happy" signal, which becomes the basis of the connection between dopamine and happiness.

Dopamine(₯) and not confused at 40? Care about reward motivation and goals

However, the happy dopamine status lasted for about 20 years. At the age of 41, she seemed unable to maintain her status as a happy molecule. Kent Berridge and Terry Robinson proposed in 1998 that dopamine is not the neurotransmitter of pleasure, but a stimulus that regulates rewards and triggers the desire to "want", developing a contemporary Addiction theory and redefines dopamine as a "desire signal": the dopamine system can modulate the incentive salience of rewards, regulating incentive value in a way that is separate from hedonic and reward learning. Clearly stated in the paper:

"The dopamine system is necessary for "want" motivation, but not for "likes" or learning new "likes" and "dislikes." [5]

The precise nature of variable dopamine continues to be challenged into the 21st century. John Salamone and Mercè Correa, discussing the changing theories of this period under the heading "Mysterious Motivational Functions" in 2012, noted that what was once thought to be dopamine " "Hedonic" or "reward" function markers actually reflect more complex "motivation and goal-directed action" regulatory functions, such as effort processes, perception of effort-related or opportunity costs, and decision-making. Other new research has also introduced dopamine Neuronal responses to aversive stimuli, and topics such as reinforcement learning or habit formation. As the concept continues to evolve, pathology of dopamine behavioral activation processes has become more clinically significant for motivational dysfunction in patients with depression, schizophrenia, substance abuse, and other disorders.

The exact nature of dopamine has been a hotly debated issue. In 2017, the American Scientist discussed the scientific uncertainty of dopamine's physiological role as the "currency of desire" and pointed out that some studies believe that dopamine sends desire signals in the brain's reward system, while others emphasize that the brain predicts rewards and can guide accordingly. Behavior. The other argument is to separate the differences, but both explanations are valid. The scientific consensus is that dopamine does not neurologically define happiness, but it drives us to unravel the intricate mysteries of neurotransmitters in the brain[6].

Today’s Dopamine(₯): Her sultriness fascinate science

Dopamine, 67 years old this year, is scientifically known to live mainly in dopaminergic neurons in the ventral tegmental area of ​​the midbrain, substantia nigra compacta, arcuate nucleus of the hypothalamus, and the gastrointestinal tract. Not only can it work with gamma-aminobutyric acid (GABA) to help olfactory sensory neurons detect and distinguish odors[7], but if it dynamically interacts with serotonin, it can also affect human social behavior[8].

Today, dopamine is no longer a simple brain chemical. Our understanding of "her" also includes early pleasure molecules, mid-term desire signals, reward systems, motivational functions, and later more complex motivation and goal-oriented action regulators. It is also a key controller that is closely related to memory, sleep, and movement sensation. With the continuous scientific understanding, the exact characters of dopamine continue to change. When I see the "Ho Ho" in her formula smiling (picture 3), I can't help but say that the more we understand dopamine, the more addictive it becomes.


[1] Collingwood, C. What is dopamine? Apr.28.2023, The Royal Institution. https://www.rigb.org/explore-science/explore/blog/what-dopamine

[2] Channer, B., Matt, S. M., Nickoloff-Bybel, E. A., Pappa, V., Agarwal, Y., Wickman, J., & Gaskill, P. J. (2023). Dopamine, immunity, and disease. Pharmacological Reviews, 75(1), 62-158.

[3] Björklund, A., & Dunnett, S. B. (2007). Fifty years of dopamine research. Trends in Neurosciences, 30(5), 185-187.

[5] Berridge, K. C., & Robinson, T. E. (1998). What is the role of dopamine in reward: hedonic impact, reward learning, or incentive salience?. Brain Research Reviews, 28(3), 309-369.

[6] Szalavitz, M. Dopamine: The Currency of Desire, Scientific American, Jan 1, 2017, https://www.scientificamerican.com/article/dopamine-the-currency-of-desire/

[7] EurekAlert, How neurotransmitters work together to detect and discriminate odors. Nov. 28. 2023. https://www.eurekalert.org/news-releases/1009395

[8] EurekAlert, First-in-humans discovery reveals brain chemicals at work influencing social behavior. Feb. 26. 2024, https://www.eurekalert.org/news-releases/1035368

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