With the help of the highly specific and sensitive fluorescence method of Falck and Hillarp together with the histochemical and pharmacological criteria for the specificity of the fluorescence reaction convincing evidence has been obtained that the fine, varicose nerve fibres observed in a vast number of regions in the mammalian central nervous system (mouse, hamster, rat, guineapig, rabbit, cat), which exhibit a green or yellow fluorescence, contain primary catecholamines and 5-HT respectively. Strong support has been given for the view that CA fibres showing a rapid recovery after administration of α-MMT contain DA, while those showing a slow recovery contain NA. There is little doubt that the monoamine-containing fibres in the brain represent the terminal ramifications of axons belonging to specific monoamine neurons and that they are true synaptic terminals. They seem to make their contacts via the varicosities which have extremely high concentrations of amines and in all probability represent the presynaptic structures, specialized for synthesis, storage and release of the amines. The central monoamine terminals thus have the same characteristic appearance as the adrenergic synaptic terminals in the peripheral nervous system. All the data strongly support the view that the specific central neurons giving rise to the terminals are monoaminergic, i.e. function by releasing their amines from the synaptic terminals. Consequently, DA, NA and 5-HT seem to be central neurotransmitters. Not only the median eminence but also the nuc. caudatus putamen, tuberculum olfactorium, nuc. accumbens and the small circumscribed areas medial to nuc. accumbens contain very fine (partly sublightmicroscopical) CA terminals. These areas react to treatment with reserpine, nialamide-dopa and α-MMT in the same way and since the nuc. caudatus putamen and tuberculum olfactorium are known to have a high DA content it seems likely that abundant DA terminals are accumulated in these special areas.

Evidence for the existence of monoamine neurons in the central nervous system. 3. the monoamine nerve terminal.

This paper gives a detailed description of the glyoxylic acid fluorescence histochemical method as designed for the highly sensitive visualization of catecholamine neurons. In this method, the primary catecholamines, dopamine and noradrenaline, are efficiently converted to intensely fluorescent 2-carboxymethyl-dihydroisoquinoline derivatives in a well defined reaction with glyoxylic acid. The method is carried out on sections from fresh or glyoxylic acid-perfused tissue, which are immersed in a glyoxylic acid solution, dried, and then reacted either by heating at +100°C, or by glyoxylic acid vapour treatment at +100°C. The method has a high reproducibility, is rapid and convenient, and if desired, sections of good quality can be ready for fluorescence microscopy within half an hour after the sacrifice of the animal. The glyoxylic acid method demonstrates central and peripheral dopamine- and noradrenaline-containing neurons with an extraordinary sensitivity and precision. The entire adrenergic neuron, including the non-terminal portions of the axon and sometimes also the dendrites, becomes fluorescent, making the method ideal for neuroanatomical tracing of central catecholamine pathways. The spectral characteristics of the glyoxylic acid-induced fluorophores have been investigated, and it is concluded that the catecholamine fluorophores can be identified and distinguished by microspectrofluorometry from those of other fluorogenic monoamines known to occur in the vertebrate brain.

The glyoxylic acid fluorescence histochemical method: a detailed account of the methodology for the visualization of central catecholamine neurons.

In vivo and in vitro studies using the histochemical fluorescence technique of Falck and Hillarp were made on the submaxillary and sublingual glands of the rat after the administration of catecholamines or dopa, or the incubation of slices of the glands with the same drugs. Catecholamines and in all probability also L-dopa were found to be bound extraneuronally in the salivary gland parenchyma under the conditions of the experiments. It is probable that the present experiments visualize the same type of extraneuronal binding as has been found with biochemical techniques. It appears that a certain activity of the parenchyma is necessary for the binding to occur. Apart from being a source of error in the evaluation of biochemical measurements, extraneuronal binding may be of importance related to transmitter mechanisms.

Extraneuronal binding of catecholamines and 3,4-dihydroxyphenylalanine (dopa) in salivary glands.

Phloroglucinol compounds of natural origin

Using ice-cold 3% potassium permanganate as a fixative (Richardson, 1966), isolated tissues from the central and peripheral nervous system were investigated in the electron microscope, with the object of identifying monoamine-containing neurons at the ultrastructural level. Thin brain slices and peripheral tissues from untreated rats and from rats treated with drugs interfering with monoamine metabolism (e.g. reserpine, H 44/68 or tetrabenazine) were incubated in physiological buffer solutions without and with monoamines in different concentrations. In certain cases, drugs interfering with monoamine metabolism (e.g. amphetamine, desipramine, cocaine or phenoxybenzamine) in different concentrations were added to the incubation medium.

In vitro studies on central and peripheral monoamine neurons at the ultrastructural level.

Catecholamines are readily converted into highly fluorescent products by treatment with formaldehyde gas, under the condition that the reaction takes place in a dry protein containing layer. The reaction, which has been found to be catalyzed by some amino-acids and peptides, has been studied by examination of the products formed especially from dopamine [β-(3,4-dihydroxyphenyl)-ethylamine] in serum albumin layers.

Fluoreszenzenzmethoden zur histochemischen Sichtbarmachung von Monoaminen. 2.. Identifizierung des fluoreszierenden Produktes aus Dopamin und Formaldehyd

A North African grasshopper (Poekilocerus bufonius (Klug 1882) (Pyrgomorphidae)), with warning coloration and which feeds on milkweeds (Asclepiadaceae), contains cardenolides similar to those found in the plant. These heart poisons which, like digitalis, excite nausea and vomiting are found in the insect's body tissues and can also be ejected in solution from its defensive glands. They thus form part of the grasshopper's defence mechanisms.

Cardenolides (Heart Poisons) in a Grasshopper feeding on Milkweeds

Über Bestandteile der Nebennierenrinde. 20. Mitteilung. Isolierung der Substanzen Q (Desoxy‐corticosteron0) und R sowie weiterer Stoffe

Die Beschaffung authentischer Samen von Strophanthus intermedius Pax wird beschrieben. Die Samen gaben nach Einwirkung des wasserloslichen Teils der darin enthaltenen Fermente reichliche Mengen von Glykosiden, aus denen sich bisher vor allem Intermediosid (1,46%) und Panstrosid (0,88%) isolieren liessen. Daneben wurde eine kleine Menge eines neuen Glykosids Nr. 800 isoliert sowie reichliche Mengen eines Kristallisats Nr. 790, das sich als Mischkristallisat von 3–4 Stoffen erwies und das bisher noch nicht vollstandig getrennt werden konnte.

Die Glykoside von Strophantus intermedius Pax. Glykoside und Aglykone, 82. Mitteilung

Mevalonic-[3-14C] acid (Ia) has been prepared by partial reduction of β-hydroxy-β-methyl-glutari-[3-14C] acid. After introduction of the ammonium salt of Ia into Digitalis lanata plants by the vick technique, crist. radioactive digitoxigenin was isolated. This contained a significant amount of radioactivity in C-20 position. From this, together with results of former authors, it follows that the biosynthesis of digitoxigenin from mevalonic acid (probably via squalene) proceeds through a pregnane derivative. The latter needs only one molecule of acetate to form the butenolide ring.

J. v. Euw

Papers

Fluoreszenzenzmethoden zur histochemischen Sichtbarmachung von Monoaminen. 2.. Identifizierung des fluoreszierenden Produktes aus Dopamin und Formaldehyd

Cardenolides (Heart Poisons) in a Grasshopper feeding on Milkweeds

Über Bestandteile der Nebennierenrinde. 20. Mitteilung. Isolierung der Substanzen Q (Desoxy‐corticosteron0) und R sowie weiterer Stoffe

Die Glykoside von Strophantus intermedius Pax. Glykoside und Aglykone, 82. Mitteilung

Die Biosynthese des Digitoxigenins, Herkunft des C-20. Glykoside und Aglykone, 253. Mitteilung†‡