60 Fun Facts About Dopamine

Dopamine is made from its precursor L-DOPA by removing what?

The step is called decarboxylation and is done by the enzyme DOPA decarboxylase.

Rather than pleasure itself, mainstream pharmacology holds that dopamine signals what?

In other words it flags how desirable or aversive an outcome is and drives behaviour toward or away from it.

To which chemical family, along with norepinephrine and epinephrine, does dopamine belong?

It is the simplest possible catecholamine: a benzene ring with two hydroxyl groups and an amine on an ethyl chain.

The primary synthesis pathway for dopamine starts with which essential amino acid?

Phenylalanine becomes tyrosine, tyrosine becomes L-DOPA and L-DOPA becomes dopamine.

Which enzyme carries out the rate-limiting step of dopamine synthesis, turning an amino acid into L-DOPA?

It needs tetrahydrobiopterin, oxygen and iron as cofactors.

Besides oxygen, which vitamin-derived cofactor does dopamine beta-hydroxylase need?

Norepinephrine is then converted to epinephrine using S-adenosyl-L-methionine.

What is the main inactive end product of dopamine breakdown, excreted in urine?

Its plasma levels have been used in schizophrenia research as a proxy for brain dopamine activity.

Which two enzymes, along with aldehyde dehydrogenase, break dopamine down?

Both MAO-A and MAO-B metabolise dopamine effectively.

How many subtypes of dopamine receptor have been identified in mammals?

They split into D1-like and D2-like families, all of them G protein-coupled.

Which dopamine receptor is the most numerous in the human nervous system?

D2 comes next; D3, D4 and D5 are present at much lower levels.

Roughly how many dopamine-producing neurons does the human brain contain?

Their cell bodies sit in a few small areas, but their axons reach much of the brain.

Which transporter packs dopamine into synaptic vesicles for storage?

After release and reuptake, dopamine is either repackaged by VMAT2 or broken down by monoamine oxidase.

Which two Swedish scientists first mapped the brain's dopamine cell groups (A8 to A14) in 1964?

Groups A1 to A7 in their scheme contain norepinephrine instead.

The substantia nigra, whose dopamine neurons die in Parkinson's, sits in which part of the brain?

Its name is Latin for "black substance".

What gives the substantia nigra its dark colour?

There is evidence that this pigment is at least partly dopamine-melanin.

The dopamine projection from the substantia nigra to the dorsal striatum is called what?

When enough of these neurons die, the result is a parkinsonian syndrome.

Which projection carries dopamine from the ventral tegmental area to the nucleus accumbens?

Together with the mesocortical projection to the prefrontal cortex it forms the mesocorticolimbic system.

Dopamine from the hypothalamus is the main inhibitor of which pituitary hormone?

Without dopamine the pituitary's lactotroph cells secrete it continuously.

Dopamine-releasing amacrine cells in the retina are active when?

They boost cone cells and suppress rods, sharpening colour and contrast in bright light.

Which two researchers accidentally discovered brain-stimulation reward in rats in 1954?

Rats would press a lever hundreds or thousands of times an hour to zap their own brains.

Robinson and Berridge's 1993 incentive-sensitization theory split reward into which two components?

Dopamine drives the wanting; the liking lives in separate hedonic hotspots.

Cambridge neuroscientist Wolfram Schultz discovered that dopamine neurons signal what?

He found it recording from macaque monkeys in the 1980s and 1990s.

Why is L-DOPA given to Parkinson's patients instead of the neurotransmitter itself?

It is usually paired with carbidopa or benserazide to stop it being converted before it reaches the brain.

L-DOPA was first isolated in 1913 from the seeds of which plant?

Swiss biochemist Markus Guggenheim did it; velvet beans of the genus Mucuna are an even richer source.

Which Vienna-based scientist found that Parkinson's disease stems from a dopamine deficiency?

He shared the 1979 Wolf Prize with Carlsson and Roger Sperry for opening the L-DOPA approach.

Oliver Sacks's memoir Awakenings, filmed in 1990, describes giving L-DOPA to survivors of which epidemic?

Robin Williams played the Sacks-based doctor and Robert De Niro the patient Leonard Lowe.

Which misfolded protein clumps into Lewy bodies in Parkinson's disease?

Because of it, Parkinson's is classed as a synucleinopathy.

Long-term dopaminergic Parkinson's treatment can cause compulsive gambling and sex in a condition called what?

It involves overuse of the medication as well as compulsive pursuit of natural rewards.

Cocaine and methylphenidate raise synaptic levels of the neurotransmitter mainly by doing what?

Amphetamines also raise synaptic dopamine but by different mechanisms.

How long do the effects of cocaine typically last?

That rapid, brief action is a big part of why it is so addictive; pill-form methylphenidate can last 12 hours.

For which addictive drug does the dopamine surge play only a minor role in addiction, per the article?

Stimulant withdrawal produces craving rather than the physical suffering of opiate or alcohol withdrawal.

Typical antipsychotics such as chlorpromazine work as antagonists at which receptor?

That realisation in the 1970s led to the dopamine hypothesis of schizophrenia.

The chemoreceptor trigger zone that controls nausea sits in which brainstem region rich in D2 receptors?

That is why D2 blockers such as metoclopramide stop vomiting and D2 agonists cause it.

Which fruit contains the highest measured concentration of dopamine, at 40 to 50 parts per million?

Eating it does nothing for the brain, because dietary dopamine never reaches it.

Dopamine has been found in the ink of which animals?

Dopamine as a neurotransmitter dates back over 500 million years to the Cambrian.

Dopamine makes up about what share of dry weight in the marine alga Ulvaria obscura?

It reduces consumption by snails and isopods.

Dopamine was first synthesised in 1910 at Wellcome Laboratories in which city?

George Barger and James Ewens made it; the name is a contraction of its full chemical name.

Who first identified dopamine in the human brain, in 1957?

Her paper came out in August; Carlsson's, often wrongly credited as first, appeared in November.

Arvid Carlsson won the Nobel Prize in Physiology or Medicine for his dopamine work in what year?

He shared it with Eric Kandel and Paul Greengard.

Which drug did Carlsson give to animals to show that depleting dopamine causes Parkinson-like symptoms?

He then reversed the symptoms with L-DOPA.

Manufactured dopamine, sold as Intropin, is given intravenously mainly to treat what?

Its plasma half-life is only about a minute, so it goes in as a continuous drip.

What is the approximate plasma half-life of dopamine in adults?

In newborns it is about twice as long.

In the kidneys, locally made dopamine has what effect?

Faults in renal dopamine can contribute to high blood pressure.

What does dopamine do to the hormone-producing beta cells of the pancreatic islets?

Where their dopamine comes from is still not clearly established.

Over 95% of the dopamine in human blood plasma is bound up as what conjugate?

Levels jump more than fifty-fold after a meal, apparently as a way of detoxifying dietary dopamine.

Which two ADHD medications named in the article increase both dopamine and noradrenaline?

They act mainly through D1 and alpha-2 receptors in the prefrontal cortex.

Mussel adhesive research led to the 2007 discovery that dopamine solutions coat almost any material with what?

The coating is technically a form of melanin and its exact structure is still unknown.

Per Cameron Sepah, who coined the term, what is the real goal of the 'fasting' fad named after this molecule?

Critics call the more extreme ascetic versions unscientific.

Where in the human body, besides neurons, is dopamine mainly synthesised?

Dopamine there is a stepping stone toward adrenaline.

Loss of dopamine with age is thought to explain which common neurological sign?

Age-related declines in D1, D2 and D3 receptors are well documented.

Restless legs syndrome and ADHD are both associated with what?

Dopamine neurons in the posterior hypothalamus that project to the spinal cord may be involved in restless legs.

The catechol part of a dopamine molecule is a benzene ring carrying two of which side groups?

An amine attached via an ethyl chain completes the simplest possible catecholamine, and also makes it a substituted phenethylamine.

Dopamine in jellyfish and corals dates its neurotransmitter role to which geological period?

That puts its emergence at the very first appearance of nervous systems, more than 500 million years ago.

In what salt form is dopamine supplied for chemical and pharmaceutical use?

The protonated form is stable and water-soluble; the free base is more reactive and readily oxidises. Dry, the salt is a white-to-yellow powder.

In leeches, dopamine inhibits swimming and promotes which behaviour instead?

In flatworms it produces 'screw-like' movements; in every animal examined it modifies motor behaviour in some way.

In which model organism does dopamine reduce locomotion and increase food-exploratory movements?

Roundworms, flatworms, molluscs and fruit flies can all be trained to repeat an action that is followed by a rise in dopamine.

Which plant, known as the velvet bean, is the richest natural source of L-DOPA?

Dopamine in food cannot reach the brain, but its precursor can, which is why the leaves and pods have been used as a drug source.

Which norepinephrine-like chemical was long thought to mediate reward in arthropods instead?

Later work found its rewarding effect in fruit flies actually comes from activating a previously overlooked set of dopamine neurons.

Who first synthesised dopamine in 1910, together with James Ewens?

The name reflects the synthesis: a monoamine whose precursor was 3,4-dihydroxyphenylalanine, better known as L-DOPA.

With which colleague did Arvid Carlsson first recognise dopamine as a neurotransmitter in 1958?

The work at Sweden's National Heart Institute showed dopamine was more than a mere precursor of noradrenaline and adrenaline.