The Dopamine Dilemma: The Misunderstood Brain Chemical

Dopamine is often portrayed as the ‘feel-good chemical’ in our brains, but this oversimplification fails to capture its true complexity. Dopamine helps drive our motivation to pursue certain actions, yet it is not responsible for the pleasure that results from these actions. Let’s explore the multifaceted nature of dopamine and uncover the truth behind this misunderstood brain chemical.

In 1957, pharmacologist Dr. Arvid Carlsson discovered dopamine as a chemical messenger in the brain.1 He found dopamine to be concentrated in the basal ganglia, a group of brain structures situated deep within our brains that are important in motor control, cognitive function, learning, and emotional regulation (2). Dr. Carlsson’s research revealed a correlation between a decline in dopamine levels in the brain and a reduction in movement, which mirrored the clinical symptoms of the neurological disorder Parkinson’s Disease (3). These studies led to the development of the oral medicine L-dopa, a precursor of dopamine, which remains an effective treatment for motor symptoms linked to Parkinson’s Disease.

Since this pioneering work, research on dopamine has been consistently evolving and have greatly impacted our understanding of how the brain functions in health and disease. The early demonstration of its involvement in movement disorders has expanded into its discovery in contributing to symptoms of schizophrenia, substance-use disorders, attention deficit hyperactivity disorder (ADHD), and motivational disorders (4–7).

So, when did we start calling dopamine the “feel-good chemical?”

Over 20 years after Dr. Carlsson’s initial discovery, researcher Dr. Roy Wise published an influential paper on dopamine and its possible connection to pleasure (8). He found that when he depleted dopamine levels in rats, they would stop working to obtain sugary rewards. Based on these results, Dr. Wise concluded that dopamine likely played an important role in pleasure, and that a lack of dopamine could result in reduced enjoyment in life. This was further supported by the finding that people with clinical depression tend to have low levels of dopamine in their brain (9). Over the years, support for Wise’s idea grew. Until the late 1980s, when researcher Kent C. Berridge found an interesting result that went against this favored idea.

Berridge studied the facial expressions of pleasure in rats, such as licking their lips after getting sweet food or opening their mouths in disgust after encountering something bitter. When he gave rats that lacked the ability to make dopamine a sweet food to see if they appeared pleased, he saw their facial reactions were completely normal (10). Even with depleted dopamine levels, these rats still licked their lips or grimaced in response to sweet and bitter foods, yet they rarely moved, ate, or drank on their own. He then repeated the experiment with rats with heightened levels of dopamine, the rats did not lick their lips more or show signs of increased pleasure. However, these rats with heightened dopamine levels ate the food far more voraciously than normal. It appeared that instead of producing pleasure, dopamine cells seemed to drive desire, or motivation to consume the food (11).

Similarly, research on drug dependence and substance use disorder has challenged the traditional view of dopamine and pleasure. Experiments have shown that even if dopamine signaling or production in the brain is disrupted, the feelings of euphoria induced by drugs persists (12–14). This indicates that dopamine is not the cause of the pleasurable sensations. Instead, studies have revealed that dopamine plays a role in motivation and learning, which is why blocking dopamine signaling can affect these processes. This complex interaction between dopamine and substance misuse highlights the need for a more nuanced understanding of the role of dopamine in the brain.

It is important to note that dopamine is not the sole factor in motivation. Our brains are not divided into neat, separate, and non-overlapping sections, like a map with clearly marked territories. Therefore, understanding the connection between motivational processes and other essential functions, including emotion, cognition, learning, reinforcement, sensation, and motor function is crucial. Other brain chemicals, such as serotonin and norepinephrine also play key roles in regulating our behavior, thoughts, and emotions (15–17). Furthermore, many factors contribute to motivation, including our experiences, environment, and internal drives. This complexity highlights the importance of considering a wide range of factors when trying to understand motivation and its underlying mechanisms. Dopamine, although a critical player, is just one piece of a much larger puzzle.

References

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2. Lanciego JL, Luquin N, Obeso JA. Functional Neuroanatomy of the Basal Ganglia. Cold Spring Harb Perspect Med. 2012;2(12):a009621. doi:10.1101/cshperspect.a009621

3. Carlsson A. Basic concepts underlying recent developments in the field of Parkinson’s disease. Contemp Neurol Ser. 1971;8:1-31.

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13. Gawin FH, Kleber HD. Abstinence symptomatology and psychiatric diagnosis in cocaine abusers: Clinical observations. Archives of General Psychiatry. 1986;43:107-113. doi:10.1001/archpsyc.1986.01800020013003

14. Leyton M, Casey KF, Delaney JS, Kolivakis T, Benkelfat C. Cocaine craving, euphoria, and self-administration: a preliminary study of the effect of catecholamine precursor depletion. Behav Neurosci. 2005;119(6):1619-1627. doi:10.1037/0735-7044.119.6.1619

15. Blows WT. Neurotransmitters of the brain: serotonin, noradrenaline (norepinephrine), and dopamine. J Neurosci Nurs. 2000;32(4):234-238. doi:10.1097/01376517-200008000-00008

16. Frazer A, Hensler JG. Serotonin Involvement in Physiological Function and Behavior. Basic Neurochemistry: Molecular, Cellular and Medical Aspects 6th edition. Published online 1999. Accessed January 31, 2023. https://www.ncbi.nlm.nih.gov/books/NBK27940/

17. Hu H, Real E, Takamiya K, et al. Emotion Enhances Learning via Norepinephrine Regulation of AMPA-Receptor Trafficking. Cell. 2007;131(1):160-173. doi:10.1016/j.cell.2007.09.017

Abi Elerding is a PhD student at the University of Washington working to identify and isolate neuronal cell systems that guide behavior in health and disease. Her research focuses on understanding how GABA interacts with dopamine and its role in motivation and learning.