“People say, “I wish I had more motivation today, because then I would try something.” But our thinking is backward. The way our brain works is that dopamine - the so-called feel-good chemical - is released the second we actually do something. So the motivation doesn’t come before, it comes after.”
—Brendon Burchard
1. Introduction
Dopamine (DA) (3,4-dihydroxyphenethylamine) is a member of the catecholamine family (a monoamine, an organic compound that has a catechol and a side-chain amine) of neurotransmitters in brain and is an antecedent to epinephrine (adrenaline) and norepinephrine (noradrenaline). DA is produced in the body (primarily by nervous tissue and adrenal glands) initially by the hydration of the amino acid tyrosine to DOPA by tyrosine hydroxylase and further by the decarboxylation of DOPA by aromatic-l-amino-acid decarboxylase. It is a key transmitter in the extrapyramidal system of the brain and crucial in synchronizing movement. A group of receptors (dopamine receptors) facilitates its function.
DA performs critical role in reward and movement control in the brain. Further, it has a function to play in modulation of behavior and cognition; voluntary movement, motivation, inhibition of prolactin production, sleep; dreaming; mood; attention; working memory; and learning. DA has multiple other functions outside the brain. In blood vessels, it impedes norepinephrine delivery and acts as a vasodilator (at endogenous concentrations); in the kidneys, it increases sodium evacuation and urine yield; in the pancreas, it diminishes insulin making; in the digestive system, it lessens gastrointestinal motility and guards intestinal mucosa; and in the immune system, it diminishes activity of lymphocytes. In the circulation, DA is primarily deposited in and transported by blood platelets [1]. Performing multiple unrelated critical biological functions makes this smart chemical, a “VVIP” for sustenance of life both in health and disease.
2. Synthesis, metabolism, and reuptake of dopamine
Tyrosine hydroxylase (TH) is a rate-limiting enzyme in the biosynthesis of DA and other catecholamines (Figure 1). Altering expression level of this critical enzyme, which eventually regulates the synthesis of DA, assists in developing promising therapeutic approaches and strategies to promote human health and address disease [2]. In presynaptic neurons, DA is encapsulated into synaptic vesicles and stored (this process is regulated by VMAT2 (vesicular monoamine transporter 2)). Later, synaptic vesicles release the DA into the synapse. Then, it binds either to presynaptic receptors (the signal can either inhibit (leading to inhibit the synthesis and release of neurotransmitters) or excite the cell) or to postsynaptic receptors. Once after the execution of function, DA is taken up into the presynaptic cell either by DAT (DA transporter) or by plasma membrane monoamine transporters (Figure 2).
COMT (catechol O-methyl transferase, principally expressed by glial cells) and MAO (has two isoforms A and B: monoamine oxidase A, primarily found in catecholaminergic neurons (e.g., neurons of
3. Dopamine: health and disease
DA acts upon to elicit feelings of enjoyment and bolstering, which motivates an animal to perform certain tasks repeatedly. In other words, reward system of the brain is strongly associated with “feel good” chemical DA. In certain areas of brain such as nucleus accumbens and prefrontal cortex, release of dopamine primarily due to fulfilling experiences such as food, drugs, physical exercise, sex, learning new tasks, figuring out unknown things, and neural stimuli correlated with these actions [4].
Parkinson’s disease (PD) is a degenerative ailment causing tremor and motor impairment and is instigated by a loss of dopamine-secreting neurons in an area of the midbrain called
There is evidence that schizophrenia comprises distorted levels of dopamine activity [6, 7], and most antipsychotic drugs utilized to cure this are DA antagonists, which reduce dopamine activity [8]. Therefore, antagonists have a significant therapeutic value in treating psychiatric conditions such as schizophrenia, which result due to overexcited dopamine organization. Attention-deficit hyperactivity disorder, bipolar disorder, and addiction are also characterized by defects in dopamine production or metabolism [9, 10, 11, 12]. When present in sufficiently high levels, dopamine can be a neurotoxin (chemical that disorders neural tissue) and a metabotoxin (endogenously produced metabolite that causes adversarial health consequences at persistently elevated levels). Chronically high levels of dopamine are linked with neuroblastoma, Costello syndrome, leukemia, pheochromocytoma, aromatic L-amino acid decarboxylase deficiency, and Menkes disease (MNK). High levels of dopamine can lead to hyperactivity, insomnia, agitation and anxiety, depression, delusions, excessive salivation, nausea, and digestive problems [9].
4. Natural ways to boost brain dopamine levels for healthy living
Though DA is available in certain food materials, as it does not cross blood-brain barrier, it will not be available in brain. Therefore, other way of enhancing brain dopamine levels in a simple way is consuming foods containing the precursor of dopamine, tyrosine that can cross blood-brain barrier and enter brain where dopamine will be synthesized from tyrosine.
Foods such as bananas, eggs, avocados, almonds, fish, and chicken are rich in tyrosine. Recent studies substantiate the fact that certain bacteria (probiotics) in gut synthesize dopamine and influence mood and behavior. Velvet beans (
5. Conclusion
The book “
Therefore, the very nature and purpose of the present endeavor aims at understanding the fundamental knowledge relating to dopamine and applying the same for supporting human life, which is very essence of biomedical research. At the same time, it is essential to realize the basic fact that practice of balanced lifestyle, meaning moderate consumption of food along with good physicomental (Yoga, Dahn, Shinshin-Toitsu-Do, etc.) and recreational activities, as practiced in ancient civilizations, can sustain the optimum levels of neurotransmitters and hormones and promote happy living. Here comes the importance of traditional/indigenous practices and knowledge of multiple age-old civilizations in promoting human health. The contents of this book fulfill the aim with which this project is initiated and moved on and successfully brought to a shape.
Acknowledgments
This work is supported by funding from Department of Biotechnology (DBT), India, grant numbers (BT/405/NE/U-Excel/2013 and BT/PR16868/NER/95/328/2015), and DST-SERB (Department of Science and Technology-Science and Engineering Research Board), India, grant number (EMR/2016/002375).
References
- 1.
Calabresi P, Picconi B, Tozzi A, Di Fillippo M. Dopamine-mediated regulation of corticostriatal synaptic plasticity. Trends in Neurosciences. 2007; 30 (5):211-219 - 2.
Tolleson C, Classen D. The function of tyrosine hydroxylase in the normal and Parkinsonian brain. CNS and Neurological Disorders-Drug Targets. 2012; 11 (4):381-386 - 3.
Mousseau DD, Baker GB. Recent developments in the regulation of monoamine oxidase form and function: Is the current model restricting our understanding of the breadth of contribution of monoamine oxidase to brain dysfunction? Current Topics in Medicinal Chemistry. 2012; 12 (20):2163-2176 - 4.
Maas JW, Bowden CL, Miller AL, et al. Schizophrenia, psychosis, and cerebrospinal fluid homovanillic acid concentrations. Schizophrenia Bulletin. 1997; 23 (1):147-154 - 5.
DeMaagd G, Phillip A. Parkinson’s disease and its management. Part 5: Treatment of nonmotor complications. Pharmacy and Therapeutics. 2015; 40 (12):838-842 - 6.
Leruelle M, Abi-Dargham A, van Dyck CH. Single photon emission computerized tomography imaging of amphetamine induced dopamine release in drug-free schizophrenic subjects. Proceedings of National Academy of Sciences, USA. 1996; 93 :9235-9240 - 7.
Jones HM, Pilowsky LS. Dopamine and antipsychotic drug action revisited. Brazilian Journal of Psychiatry. 2002; 181 :271-275 - 8.
Olguin HJ, Guzman DG, Garcia EH, Mejia GB. The role of dopamine and its function as a consequence of oxidative stress. Oxidative Medicine and Cellular Longevity. 2016; 9 (730):467 - 9.
Schildkraut JJ. The catecholamine hypothesis of affective disorders: A review of supportive evidence. American Journal of Psychiatry. 1965; 122 :509-522 - 10.
Schildkraut JJ, Orsulak PJ, Schatzberg AF, Gudeman JE, Cole JO, et al. Toward a biochemical classification of depressive disorders. I. Differences in urinary excretion of MHPG and other catecholamine metabolites in clinically defined subtypes of depression. Archives of General Psychiatry. 1978; 35 :1427-1433 - 11.
Wise RA. Addictive drugs and brain stimulation reward. Annual Review of Neuroscience. 1996; 19 :319-340 - 12.
Cook EH, Stein MA, Krasowski MD. Association of attention-deficit disorder and the dopamine transporter gene. American Journal of Human Genetics. 1995; 56 :993-998 - 13.
Lampariello LR, Cortelazzo A, Guerranti R, Sticozzi C, Valacchi G. The magic velvet bean of Mucuna pruriens . Jouranl of Traditional and Complementary Medicine. 2012;2 (4):331-339 - 14.
Greenwood BN. The role of dopamine in overcoming aversion with exercise. Brain Research. 2018. pii: S0006-8993(18)30452-9. In Press - 15.
Salimpoor VN, Benovoy M, Larcher K, Dagher A, Zatorre RJ. Anatomically distinct dopamine release during anticipation and experience of peak emotion to music. Nature Neuroscience. 2011; 14 (2):257-262