Dopamine: Enhancing this Important Neurotransmitter

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Dopamine is an important catecholamine monoamine neurotransmitter.  Dopamine plays important roles in motor control, motivation, arousal, cognitive control, reinforcement, and reward.  It is considered a stimulatory neurotransmitter.

Dopamine controls the brains voltage or power. The brains power determines the ability to:

  • Stay focused
  • Stay on task
  • Concentrate
  • Accomplish a job or task

A deficiency of dopamine results in not enough maintenance of brain voltage, which is generally manifested as the brain slowing down and losing energy.

After age 45, the brain’s dopaminergic neurons age rapidly, causing a decline in dopamine levels of 13% per decade. [ [i] ] A drop in brain dopamine to 30% of the normal level leads to Parkinson’s, and a plummet to 10% results in death.

Dopamine - Voltage Change and Impact on Cognitive Abilities

Voltage Change 
VoltageConditions
20Superior energy and concentration
10Normal energy and concentration
9Fatigue, mild memory loss and cognitive deficit
8Insomnia, panic disorder
7Obesity, moderate obsessive-compulsive disorder, mild depression
6Moderate addiction, major depression
5Borderline personality disorder, chronic fatigue
4Chronic depression, violent behavior
3Attention deficit disorder
2Alzheimer’s disease
1Schizophrenia
0Coma

The following physical manifestations are apparent with a deficiency of dopamine:

  • Loss of mental intensity
  • More time and effort needed to complete a task
  • Less concentration (wandering mind)
  • Decision making is not as fast
  • Work intensity is diminished and slowed

Dopamine Deficiency

Dopamine Deficiency 
Overall SymptomsPhysical Symptoms
Confusion/Loss of AttentionAddiction
Anemia
Bone density loss
Constipation
Diabetes
Difficulty achieving orgasm
Digestion problems
Excessive sleep
High blood pressure
Hypoglycemia
Impotence
Inability to lose weight
Involuntary movements
Joint pain
Kidney problems
Lack of quickness
Low sex drive
Narcolepsy
Obesity
Parkinson’s disease
Poor blood sugar stability
Poor physical strength
Poor walking
Shuffling gait
Slow metabolism
Slow or rigid movements
Thyroid disorders
Wide-based gait

Dopamine Precursors and Biosynthesis

There are three precursors to the neurotransmitter dopamine:

  • L-Tyrosine
  • L-Phenylalanine
  • L-DOPA

N-Acetyl-L-Tyrosine (NALT) can be substituted for L-Tyrosine and has better bioavailability while being able to cross the blood brain barrier better than L-Tyrosine.

D,L-Phenylalanine can be substituted for L-Phenylalanine.

L-DOPA is the direct precursor to dopamine and is able to cross the blood brain barrier.   A natural high-yielding source of L-DOPA is Mucuna pruriens (Velvet Bean).  The seeds of the plant contain about 3.1–6.1% L-DOPA and the leaves contain about 0.5% L-DOPA.

The sequence of the biosynthesis of dopamine is as follows:

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L-Phenylalanine is converted into L-tyrosine by the enzyme phenylalanine hydroxylase (PAH), with molecular oxygen (O2) and tetrahydrobiopterin (THB) as cofactors.

L-Tyrosine is converted into L-DOPA by the enzyme tyrosine hydroxylase (TH), with tetrahydrobiopterin (THB), O2, and ferrous iron (Fe2+) as cofactors.

L-DOPA is converted into dopamine by the enzyme aromatic L-amino acid decarboxylase (AADC; also known as DOPA decarboxylase (DDC)), with pyridoxal phosphate (PLP) as the cofactor.

Dopamine itself is also used as precursor in the synthesis of the neurotransmitters norepinephrine and epinephrine.

Dopamine is converted into norepinephrine by the enzyme dopamine β-hydroxylase (DBH), with O2 and L-ascorbic acid as cofactors.

Norepinephrine is converted into epinephrine by the enzyme phenylethanolamine N-methyltransferase (PNMT) with S-adenosyl-L-methionine (SAM) as the cofactor..

Deficiency in any required amino acid or cofactor will result in subsequent dopamine, norepinephrine, and epinephrine biosynthesis impairment and deficiency.

DopamineSynthesis

Dopamine Biosynthesis

There are a few natural cofactors that assist in the biosynthesis of dopamine and are required by the various enzymes:

  • Vitamin C (Ascorbic acid)
  • Vitamin B6 (Pyridoxal phosphate (PLP, pyridoxal 5′-phosphate, P5P))
  • S-Adenosyl methionine (SAMe)

Dopamine: Required Enzymes and CoFactors

Dopamine - Enzymes and CoFactors  
Amino Acid/NeuroTEnzymeCofactor(s)
L-Phenylalaninephenylalanine hydroxylase (PAH)
molecular oxygen (O2)
tetrahydrobiopterin (THB)
L-Tyrosinetyrosine hydroxylase (TH)
tetrahydrobiopterin (THB)
O2
ferrous iron (Fe2+)
L-DOPAaromatic L-amino acid decarboxylase (AADC; also known as DOPA decarboxylase (DDC))
pyridoxal phosphate (PLP)
Dopaminedopamine β-hydroxylase (DBH)
L-ascorbic acid (Vitamin C)
O2
Norepinephrinephenylethanolamine N-methyltransferase (PNMT)
S-adenosyl-L-methionine (SAM)

Other than the three precursors that assist in the production of dopamine, namely, L-Phenylalanine, L-Tyrosine and L-DOPA, there are also certain natural substances that are recognized to enhance the production and function of dopamine.

Substances that May Enhance the Production and Function of Dopamine

Dopamine  
CategoryNootropics/Nutraceuticals/Foods/HerbsReference
Amino Acids
Acetyl-L-Carnitine (ALCAR)1
Theanine2
Herbs
Ginko Biloba3
Korean Ginseng4
Siberan Ginseng5
St. John’s Wort6
Lipids
DHA7
Phosphatidylserine8
Minerals
Copper9
Magnesium10
Manganese11
Nootropics
CDP-Choline12
Deprenyl13
Vinpocetine14
Nucleic Compounds
NADH15
Uridine16
Quinones
Coenzyme Q1017
Vitamins
Alpha-GPC18
Vitamin B619
Vitamin C20


References:

[i] Knoll J. (-)Deprenyl-medication: a strategy to modulate the age-related decline of the striatal dopaminergic system. J Am Geriatr Soc. 1992 Aug;40(8):839-47.


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