The Falck-Hillarp method of fluorescence (the F-H method) is a technique that makes it possible to demonstrate and study, with unique precision and susceptibility, certain

monoamine Monoamine neurotransmitters are neurotransmitters and neuromodulators that contain one amino group connected to an aromatic ring by a two-carbon chain (such as -CH2-CH2-). Examples are dopamine, norepinephrine and serotonin. All monoamines are ...

s, among those the three

catecholamine A catecholamine (; abbreviated CA) is a monoamine neurotransmitter, an organic compound that has a catechol (benzene with two hydroxyl side groups next to each other) and a side-chain amine. Catechol can be either a free molecule or a subst ...

dopamine Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic compound, organic chemical of the catecholamine and phenethylamine families. Dopamine const ...

noradrenaline Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic chemical in the catecholamine family that functions in the brain and body as both a hormone and neurotransmitter. The name "noradrenaline" (from Latin '' ad'', ...

, and

adrenaline Adrenaline, also known as epinephrine, is a hormone and medication which is involved in regulating visceral functions (e.g., respiration). It appears as a white microcrystalline granule. Adrenaline is normally produced by the adrenal glands and ...

, as well as

serotonin Serotonin () or 5-hydroxytryptamine (5-HT) is a monoamine neurotransmitter. Its biological function is complex and multifaceted, modulating mood, cognition, reward, learning, memory, and numerous physiological processes such as vomiting and vas ...

and related substances. The method is based on the important and decisive discovery that these compounds are able to react with

formaldehyde Formaldehyde ( , ) (systematic name methanal) is a naturally occurring organic compound with the formula and structure . The pure compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde (refer to section F ...

– in near complete absence of water – to form

fluorophore A fluorophore (or fluorochrome, similarly to a chromophore) is a fluorescent chemical compound that can re-emit light upon light excitation. Fluorophores typically contain several combined aromatic groups, or planar or cyclic molecules with se ...

s, i.e. molecules that, when irradiated with light invisible to the eye, will emit visible light. This happens in a “dry” state, without extracting the monoamines from the cells during the entire procedure, a process that starts with separation of a tissue sample and ends with a thin tissue slice that can be examined in a fluorescence microscope. The F-H method allowed, for the first time, the examiner to watch these monoamines light up in the microscope and to precisely determine in which cells they were present, and thereby understanding their functions. The method was developed by Bengt Falck and

Nils-Åke Hillarp Nils-Åke Hillarp (4 July 1916 – 17 March 1965) was a Swedish scientist and a prominent force in research on the brain's monoamines. Biography Hillarp was the son of merchant Nils Bengtsson and Hulda, former Johansson, and the brother of Rut Hi ...

in the 1960s at the Department of Histology,

University of Lund , motto = Ad utrumque , mottoeng = Prepared for both , established = , type = Public research university , budget = SEK 9 billion central Central is an adjective usually referring to being in the center of some place or (mathematical) object. Central may also refer to: Directions and generalised locations * Central Africa, a region in the centre of Africa continent, also known as ...

and the

peripheral nervous system The peripheral nervous system (PNS) is one of two components that make up the nervous system of bilateral animals, with the other part being the central nervous system (CNS). The PNS consists of nerves and ganglia, which lie outside the brain ...

and for the first time comprehend that these substances act as signal substances, i.e. transmitters. The initial publication, written already in 1961, described a wide-ranging examination of nerves supplying a large number of organs in the body. This work validated the concept of

Ulf von Euler Ulf Svante von Euler (7 February 1905 – 9 March 1983) was a Swedish physiologist and pharmacologist. He shared the Nobel Prize in Physiology or Medicine in 1970 for his work on neurotransmitters. Life Ulf Svante von Euler-Chelpin was born in S ...

, the Nobel prize winner, that noradrenaline is the signal substance in peripheral autonomic nerves. In the same year, this first publication was followed by an explanation of the chemical background of the F–H method. Very thin membranes, such as the rat iris or mesentery, do not have to be sectioned for microscopic studies but may simply be spread on glass, dried, and then exposed to gaseous formaldehyde for subsequent study with a fluorescence microscope. The publication on the chemical background was later named among "The 200 Most-Cited Papers of All Time". In 2012, the Faculty of Medicine at the University of Lund arranged a symposium “From Nerve to Pills” celebrating the 50th anniversary of the initial publication of the F-H method.

References

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External links

The Falck-Hillarp Fluorescence Method
Biochemistry methods