The History of Dopamine #1: It All Began with a Faba Bean

Beans, greens, and a lot of funky names.

In 1910, in a laboratory at the University of Rome, a man with a truly fabulous name identified an interesting chemical compound from a slightly less faba-ulous bean. Torquato Torquati - yes, that's really his name - had isolated DOPA from Faba Beans. Earlier in that year, DOPA - the shorthand name for Dihydroxyphenylalanine (try saying that one ten times fast) - had been discovered as a precursor to synthesising noradrenaline. In 1911, Casimir Funk from the Lister Institute in London also synthesised this funky DOPA stuff while making adrenaline in vivo.

Then in 1913, yet another in a curious procession of people with very satisfying names - one Markus Guggenheim, of Grenzach, Switzerland - extracted some DOPA from his own batch of Faba beans. After giving it a minute of thought, he decided it might be interesting to give the stuff to a rabbit just to see what happens.

Well, the rabbit didn't seem to mind the 1 gram dosage, and no ill effects observed, so obviously that meant it was time to try it on himself!

After swallowing 2.5 grams worth, he promptly began throwing up, noting later that "this showed, however, that the substance is not completely harmless."

All in the name of Science!

For the next 40 years, there wasn't a whole lot of progress being made in this particular area, what with the 2 largest mass-slaughters in all of human history happening one after the other and everything. Eventually, though, the parts of humanity that survived those mega-catastrophes got back on the wagon of progress.

DOPA was a precursor chemical which could be transformed into something called "hydroxytyramine", before transforming into noradrenaline. The name "hydroxytyramine" doesn't exactly roll easily off the tongue either, and soon, it was given a rebranding.

"The term 'dopamine' has recently been proposed by Dale for what is here called hydroxytyramine", wrote Hermann Blaschko in 1952; "this new name is preferable because it is less ambiguous and because it stresses the relationship between amino-acid and amine." Or in other words: it's way easier to say and spell.

In 1956, our friend Blaschko gave a lecture to the Swiss Society of Physiology, Biochemistry and Pharmacology, in Freibourg, Switzerland (seriously, Italy and Switzerland were right into this stuff for some reason), and raised the real question: "What is the functional significance of dopamine?"

What the hell does it even do here?

He went on to suggest "the possibility that dopamine has some regulating functions of its own which are not yet known.", whereupon he proceeded to drop the microphone and strut out of the lecture hall, leaving a stunned and perplexed audience behind to ponder. Not really, but that would have been fun.

Now, in 1958, we finally begin unearthing (unbraining?) endogenous dopamine from the brain of a (post-)living creature: we're back to the rabbits. Poor things can’t catch a break. Arvid Carlsson - one of the least-satisfying names in this particular history, but perhaps one of the most significant - found a lot more of the stuff inside the rabbit brain than anyone had expected. If Dopamine was merely a precursor chemical on the way to synthesis of noradrenaline, there shouldn't be much of it at all just lying around, but there was. There was a ton of it, in fact. After conducting some chemical tomfoolery, they were able to prove that dopamine was truly endogenous, and was there in its own right, and wasn't just all being converted into noradrenaline.

Okay, so rabbits have the stuff, what about other animals? In 1959, Bertler and Rosengren - two students of Carlsson - examined a variety of species, including cows, sheep, pigs, dogs, cats, guinnea pigs, rats, and rabbits. Every single one of them had significant quantities of dopamine in the brain, and it was particularly prevalent in the Basal Ganglia and Caudate nucleus, where approximately 80% of the brain's dopamine was located. Further studies done by other scientists then extended this same finding to humans.

This evidence apparently wasn't enough for some attendees of the 1960 Ciba Foundation Symposium in London. Marthe Vogt - again with those fantastic names - and Sir Henry Dale were not convinced. They cited their own experimentation with increasing dopamine levels in rabbits, where no behavioural change was identified. This wasn't exactly a water-tight case *against* the previous findings, and very soon, the implications of Carlssons conclusions were accepted by the community, and he was awarded a Nobel Prize for his efforts - 40 years later. Wouldn’t want to be too hasty with that award, would we?

Clearly, there was something to this dopamine stuff, however Noradrenaline - Dopamine's older sibling - was still hogging the scientific spotlight throughout the 1960s, with the scraps being snatched up by 5-HT and Acetylcholine. It wasn't until 1967 that the first real breakthrough finally came around.

Locura Manganica: The Manganese Madness

George Constantin Cotzias was a man of energy, intensity, and destiny. Born on the island of Crete in 1918, he did his first years of medical schooling in Athens up until August of 1941, where as a refugee from the Nazi invasion of Greece, and after having fought briefly with the Greek resistance, he arrived with his family at a port in New York, broke and destitute and carrying the mental scars and physical exhaustion of a harrowing and desperate escape through warring countries. After the defeat of the Axis powers in 1945, his parents were able to return to Athens and pick up the pieces of their past lives of privilege and prestige.

When George applied for admission to an American medical school in 1942 - after his arrival in New York - to complete his studies, he was summarily rejected, on the grounds that not only was his English not considered good enough, but - according to the university - his medical training in Athens had also not brought him even close to the minimum standards expected in the areas of Physiology, Pharmacology, and Biochemistry. He was told he would require significant training before being eligible even to begin first year medical school.

On the advice of his father, he put those rejections aside, and continued sending applications in to other prestigious universities of medicine. Eventually, he won acceptance to Harvard Medical School, graduating cum laude only 2 years later.

So much for not being up to scratch, hey?

After a stint as resident of neurology at Massachusetts General Hospital, he was invited to join a new department at Rockefeller Hospital, researching salt metabolism and energy balance disturbances in hypertensive patients. His work lead him to investigate the metabolism of amines in organic tissue, finding that 3 major amine groups - catecholamines, diamines, and histamines - played a role in hypertensive disorders, and his focus turned toward enzymes that inhibited their activity through oxidation. This work would turn out to be vital preparation for a great discovery many years later.

And then one day, he managed to get his hands on a Cyclotron at Brookhaven National Labs, after moving there in 1954. Now he was firing high-energy neutron beams at tissue samples, detecting with unprecedented accuracy the trace metal distribution in various types of cells, including blood cells. It wasn't just any trace metal he was interested in, no - there was one in particular which had long held secrets in its effects on the brain.

Chilean miners digging for manganese had long been known to the medical science community for an affliction called "Locura Manganica", or "Manganese Madness". No, unfortunately it is not a disease from the over-consumption of japanese comics. People with manganism suffered from a symptomatology with a remarkable resemblance to Parkinsons, and had long been the subject of neurologist attention and interest.

When over-exposed to manganese, an individual suffers from a litany of psychomotor effects, "Characterized by compulsive or violent behaviours, emotional instability, disorientation, and hallucinations" (Bouchard et al, 2007). While these would last only about a month, it was the long-term chronic effects that were of the highest concern, forming: "a parkinsonian syndrome typified by muscular hypertonia, gait dysfunction with a propensity to fall backward, postural instability, bradykinesia, rigidity, micrographia, masked facies, speech disturbances and muscle tremors", while, "Lower levels of [manganese] exposure among active workers are associated with neurofunctional alterations characterized by neuromotor and cognitive deficits, as well as mood changes".

How exactly this was happening, no one had any clue.

Something about manganese was causing alarming long-term damage to vital systems in the brains of these miners. Could Parkinsons disease be linked to manganese poisoning? Unlikely, since Parkinsons afflicted people from any and all walks of life and career, not just miners, and symptoms had a long ramp-up period. However, considering that they shared some very highly specific symptoms, perhaps more could be learned about Parkinsons if we could follow the trail of manganese metabolism in tissues, and see where it ends up.

Along comes George with his Cyclotron, ready for pursuit. It was as though he was born for this very task. He was fascinated by how the body processes all kinds of molecules, from essential nutrients to toxins, and the Cyclotron meant he had exactly the right tool for sniffing out manganese in samples of any kind of tissue. "In a series of basic studies over the following decade", wrote Vincent P. Dole of the National Academy of Sciences in his 1995 memoir of George, "he elucidated the distribution, absorption, elimination kinetics, and probable function of manganese.". It was during these studies that he began to shine light on its specific neurotoxic effects, and what he found were distinct parallels between manganism and Parkinsons disease: manganese was devastating areas of the basal ganglia, in the same locations where lesions are found in the brains of Parkinsons patients, and both matched the locations where the majority of dopamine concentration was found by Carlsson et al.

It was becoming apparent that dopamine seemed to be implicated Parkinsons and Locura Manganica somehow.

Dope-a

When Carlsson and his team were messing around with the brains of poor fluffy bunny-rabbits in 1957-1958, they were simply intending to study the effects of Reserpine - a recent and highly effective anti-psychotic. However, in large doses, especially in those who were not in the throes of a psychotic episode, Resperine could bring on symptoms that mimicked Parkinsons. What was then known about Reserpine's neurochemical effects showed that both serotonin and noradrenaline levels were depleted, which suggested this must be how it achieves its anti-psychotic effects.

If reducing levels of serotonin and noradrenaline was truly the responsible mechanism, then the effects of Reserpine must be reversible by restoring those amines to previous levels. This was achieved by administering the precursor molecules which could cross the blood-brain barrier and be transformed into the required compounds of serotonin and noradrenaline.

So they began by trying to restore serotonin, injecting the precursor 5-HT. No changes observed. Then they went for the noradrenaline, and injected the precursor DOPA, which transforms to dopamine, and then to noradrenaline. Suddenly, they saw massive relief of the parkinson-like symptoms brought on by Reserpine. Eureka? Was noradrenaline the key?

Carlsson and co decided to take a closer look at the composition of these compounds in the brains of their test subjects following the injection of the precursor amines. If it truly was the noradrenaline reversing the Reserpine's effects, they should rightly see a restoration of something like normal levels of the neurotransmitter in the brain.

That isn't what they found.

Noradrenaline levels seemed mostly unaffected following the treatment with the DOPA precursor. This came as a bit of a shock. They knew that DOPA first has to transform into dopamine after crossing the blood-brain-barrier, before it transforms into noradrenaline. What was Dopamine's role in all of this? No one was even really sure whether it was a "real" neurotransmitter. So far, it had always been assumed to be an intermediate step towards noradrenaline, which was otherwise useless.

Further investigation revealed that areas of the brain with high dopamine content were typically sites with the least amount of noradrenaline, and vice versa. Now it was becoming clear as day: Dopamine was the real thing. It wasn't just precursor material. It was a neurotransmitter in its own right, and one that perhaps could play a big role in physiological and motor functions. It was all adding up.

It was with these results that they made their way to that Ciba Foundation Symposium in 1960, and were met with not just surprise, but disbelief, from the mass of their peers in the field. This reaction was to be short-lived, however. Over the following years, not only was Carlsson's evidence being taken very seriously by working neurologists in the field, but it was becoming the foundation of further work and research, and gave inspiration to a collection of scientists around the world who were now determined to take this even further.

Enter: Hornykiewicz

In a heating-up contest for "most fascinating name in the history of dopamine", a man by the name of Oleh Hornykiewicz - a very serious family man, described as "realistically direct" by colleagues, but without arrogance - was determined to be #1 in this grand name contest.

Not really. He was more focussed on his science, and in his field, he came to be considered "ingenious". After having experienced brutal Nazi and then savage Soviet occupations in his formative teenage years living in Vienna, he had a somewhat hardened character and did not take fools gladly, but he had still maintained the ability to keep an open mind, listen to other opinions and ideas, and then formulate his own very original thinking.

Oleh spent a few years working with our old friend Blaschko in his lab at Oxford on various dopamine-related subjects, and was encouraged to continue on the dopamine track with further study. After returning to Vienna, and having read and been inspired by the works of Kathleen Montagu on dopamine in the central nervous system, as well as various others, he was also starting to believe in dopamine as a neurotransmitter, and understanding its role in more detail became a mission.

That's when he and a young post-doc - Herbert Ehringer - set off trying to acquire various human body parts from patients who had died after suffering from Parkinsons disease, in order to compare them to samples from deceased individuals who had not had it (called a "control sample", like a baseline to compare against).

Can you just imagine like, calling up your local morgue, "Hey yeah, so I'm trying to get a hold of some spare human parts, you wouldn't happen to have any in stock? Preferably any brains, from Parkinsons patients? Maybe a few normal brains too?"

If I were the morgue phone person I'd have hung up, but that's probably why I'm not a morgue phone person.

Upon acquiring their loot of extracted human brains, they proceeded to snip out bits and pieces from them, as though they were cutting away the toxic parts of a fugu fish and then slicing it into sashimi. By the way, did you know that it takes 3 years of full time study and training before a Chef can be legally qualified to prepare fugu? Zero room for error with that one.

Over 8 weeks, they took their sashimi-like extracts of the corpus striatum and put them through an iodine reaction developed by von Euler and Hamberg to stain dopamine molecules bright pink. They then took these under the microscope, and found that non-parkinson patient brains contained an abundance of the pink stuff. Much dopamine. When they checked the very same sections of the brains from Parkinsons patients, it was completely absent. No pink stuff. No dopamine.

Oleh and Herbert published these findings in 1960 after a lot of further analysis, but like many great discoveries, it took a while to really settle the case that this was the real deal and not just some anomaly in the samples, or a post-mortem artefact, or whatever. In 1964, a study by Bernheimer was able to prove their observations and conclusions were solid. It was no fluke, anomaly or artefact.

Dopamine research warmed up significantly during the latter half of the 1960s. There was Dahlstrom and Fuxe's discovery of the high dopamine content of the substantia nigra and other parts of the striatum in rats by using new staining technology in 1964, and a dopamine pathway demonstrated by lesion experiments in the same year by Porter and Sourkes, another paper from the same pair on pharmacological manipulations of the nigrostriatal dopamine system, strongly arguing for its importance in motor movement, and on it went. Hornykiewicz wasn't just sitting on his hands, either.

Behind his monumentally thick-rimmed glasses, his mind was well and truly at work on an idea.