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The fluorescence method ofFalck andHillarp was used to study the occurrence of biogenic monoamines in the islets of Langerhans of monkeys. A storage of a catecholamine was demonstrated in the A2-cells of owl monkey, whereas no histochemically demonstrable amount of monoamines could be seen in the islet cells of marmoset,Rhesus monkey, squirrel monkey, andCebus monkey.

The corpora cavernosa et spongiosa penis from Rhesus monkeys, Cynomolgus monkeys and cats have been investigated by means of the method for fluorescence microscopical detection of catecholamines- and tryptamines according to Falck and Hillarp.

The adrenergic retinal neurons of perch and trout were studied with the fluorescence microscopical method of Falck and Hillarp. Pilot studies were also performed on pike, plaice, cod, eel, goldfish, cunner, black moor, cichlid and carp. Only minor differences were noted between the species.

The stellate processes and cell bodies of the dermal melanophores in the rainbow trout are intimately enclosed by a plexus of thin varicose nerves which display a specific catecholamine fluorescence. The nerves contain probably small amounts of noradrenaline and have the ability to take up and concentrate this amine. Denervation of the skin leading to dispersion of the melanophores causes the nerves to disappear. The findings leave little doubt that the dermal chromatic motor nerves are adrenergic.

1.The localization of catecholamines and 5-hydroxytryptamine has been investigated in the human testis, epididymis, ductus deferens and prostate obtained at operations on patients aged 26–79 years.2.In fluorimetric determinations noradrenaline was found to be present in varying concentrations in the genital tract. The lowest amount (0.07 µg/g) was found in the testis. In proximal direction along the ejaculatory duct system there was a progressive increase in the noradrenaline level, reaching a maximum of 1.43 µg/g in ductus deferens. The prostatic tissue (obtained from hyperplastic glands) contained only 0.15 µg/g noradrenaline.No dopamine was present. Adrenaline occurred, by all probability as an artefact, only in tissues from one single case to which this amine had been administered as part of the local anaesthetic mixture given before operation.3.Fluorescence microscopic analysis of formaldehyde-treated genital organs revealed the presence of adrenergic nerves, the number of which well agreed with the noradrenaline concentrations.Only vascular nerves were found in the testis. The bulk of the adrenergic nerve terminals in the epididymis, ductus deferens and prostate innervated the smooth muscle coats, whereas only a smaller portion of the adrenergic nerve population was of vasomotor nature.4.Microspectrophotometric characterization of the formaldehyde-induced fluorescence in the tissue sections confirmed that the adrenergic nerves contained noradrenaline.5.The finding of fluorescent ganglion cells in the prostate indicated that part — if not all — of the male genital tract also in humans is innervated by way of so-called short adrenergic neurons, originating in peripherally located sympathetic ganglia.6.Flask-shaped cells, morphologically resembling the enterochromaffin cells and emitting a yellow indole fluorescence, were present in the epithelium of the prostatic mucosa.7.Apart from the specific, formaldehyde-induced monoamine fluorescence, a considerable amount of autofluorescence of varying colour and related to different structures occurred both in the epithelial layers and in the connective tissue.

The distribution of 5-hydroxytryptamine in the central nervous system of the lizards Lacerta viridis and muralis was investigated with the fluorescence method of Falck and Hillarp. Microspectrometric analyses revealed that the yellow fluorescence had the characteristics of the fluorophore of 5-hydroxytryptamine and chemical determinations on whole brains demonstrated the presence of considerable quantities of 5-hydroxytryptamine (5,2–6,4 µg/g). Nuclear areas of the mesencephalon, di and telencephalon, which are mainly intercalated in sensory pathways, receive terminal ramifications of 5-hydroxytryptaminecontaining neurons. These fibres are presumed to originate from cells situated in the tegmentum. The nucleus reticularis mesencephali is shown to contain numerous perikarya of nerve cells rich in 5-hydroxytryptamine.

The adrenergic nerves in the pancreas of mice, rats, guinea-pigs, rabbits, and cats were investigated with the fluorescence method of Falck and Hillarp. The relations between the adrenergic fibres and the vessels were studied by the injection of india ink into the vessels.

1.The occurrence of monoamines in the median eminence of the untreated pigeon, chick, goose, sparrow, and gull was studied. In all species, monoamines were found in the external layer localized in delicate varicose fibres. It was also found that the fluorescence intensity in the external layer of the median eminence clearly differed in various species, the pigeon having the weakest fluorescence and the chick the strongest.2.The uptake of exogenous amines in the zona externa of the median eminence was investigated in the pigeon and the chick. The following substances, 1-dopa, dopamine, noradrenaline, and 5-hydroxytryptamine were accumulated into the fibers of the zona externa. A species difference could be ascertained; in general, chicks tolerated higher doses of amines than did pigeons.3.In contrast to mammals, it was established that cocaine failed to prevent the accumulation of 1-dopa, dopamine, and a-methyl-noradrenaline in the zona externa of both pigeons and chicks.

An accumulation of monoamines is found in the adult eminentia mediana and infundibular stem, close to the capillaries of the primary plexus, where they seem to be stored mainly in closely packed delicate varicose fibres, often with swollen endings, “droplets”. The first traces of monoamines are visible in the embryonic eminentia of fetuses from the last three days of the gestation period, but typical monoamine-containing fibre endings close to the primary plexus capillaries in zona externa are not found until towards the end of the first post-natal week. The adult condition is attained two weeks later. Nearly all cells in the adult pars intermedia show a specific yellowish fluorescence whose intensity shows a wide individual variation. Such fluorescent cells are sometimes present in the intermedia of the new-born. In some but not all adult specimens, a fluorescent varicose fibre system is visible. Fluorescent fibres were first observed in the intermedia of the new-born. Fluorescent fibres are visible in n. arcuatus and n. paraventricularis in the fetus at the 16th day of the gestation period. Nerve cell bodies storing visible amounts of monoamines are found in n. arcuatus, n. periventricularis anterior, and n. premammillaris ventralis of the adult. This amine storing activity is first visible in n. arcuatus of the embryo at the 17th day of the gestation period. The adult condition of these cells is reached during the first postnatal week.

In the pituitary gland of the cat, dopamine (M.V. 0.78 µg/g), noradrenaline (M.V. 0.29 µg/g) and 5-HT (M.V. 0.94 µg/g) have been found. With the histochemical fluorescence method, a rich system of delicate fluorescent varicose fibres, often provided with irregular swellings or droplets, was observed in the neural lobe and pars intermedia. Microspectrofluorimetrically, these fibre structures exhibit the spectral characteristics of catecholamines. Most cells in the pars intermedia and a large number of cells in pars distalis show a yellowish fluorescence, with microspectrofluorimetric characteristics which differ entirely from those of the catecholamines and 5-HT. In animals treated with reserpine, the pituitary dopamine, noradrenaline, and 5-HT are largely depleted. However, the intensity and the spectral properties of the cellular fluorescence are not affected by this treatment, whereas the fluorescent fibres can no longer be seen. Thus none — or only little — of the catecholamines and 5-HT but some other monoamine-like substance is stored in the fluorescent cells of the adenohypophysis. Preliminary studies suggest that this substance is closely related to or perhaps identical with tryptamine.

The nerve supply to the iridic melanophores of the rat was studied with the electron microscope. The adrenergic and cholinergic terminals were identified with the aid of 5-hydroxydopamine, which produces dense-cored 400–800 Å synaptic vesicles in adrenergic axon varicosities, whereas the synaptic vesicles of cholinergic axons remain empty. It was found that both adrenergic and cholinergic terminal axons come in close apposition (200–250 Å) with the melanophores. The appositions have the same appearance as synapses in peripheral tissues. It seems likely that the murine iridic melanophores have a double innervation, although its functional significance is obscure.

The lower spinal cord including the caudal neurosecretory system of the pike (Esox lucius) was investigated by means of light and electron microscopy and also with the fluorescence histochemical method of Falck and Hillarp for the visualization of monoamines. A system of perikarya displaying a specific green fluorescence of remarkably high intensity is disclosed in the basal part of the ventrolateral and lateral ependymal lining of the central canal. The area corresponding to the upper half of the urophysis has most cells; their number decreases caudally and cranially. A considerable number of their beaded neurites reach the neurosecretory neurons by different routes but are only occasionally present in the actual neurohemal region. An intensely fluorescent dendritic process is sometimes observed terminating with a bulbous enlargement at the ependymal surface in the central canal. Besides small, electron lucid vesicles in the terminal parts of the axons, the neurons contain numerous large dense-core vesicles which can apparently take up and store 5-hydroxydopa (5-OH-dopa) and 5-hydroxydopamine (5-OH-DA). These neurons are thought to be adrenergic and to contain a primary catecholamine, possibly noradrenaline.

The relations between adrenergic and cholinergic terminals were studied in rat iris and rat heart with the electron microscope. Adrenergic terminals were identified by treating the animals with 5-hydroxydopamine, which produces dense-cored synaptic vesicles in adrenergic terminals in tissues fixed in glutaraldehyde and osmium. The specificity of this observation was verified. It was found that adrenergic and cholinergic nerve terminals often come in close contact with one another, the distance between the adjoining membranes being about 250 Å. At times, faint membrane thickenings could be observed in these places. The available pharmacological, physiological, and morphological evidence leaves little room for doubt that cholinergic terminal fibres can influence the adrenergic fibres. From mainly morphological evidence, it is also postulated that adrenergic terminals influence cholinergic ones.

The retina of Aotes monkeys, Cebus monkeys, squirrel monkeys, and marmosets were investigated. Adrenergic perikarya were found in the innermost cell rows of the inner nuclear layer of all the investigated species. In addition, the Cebus monkey was found to have a special type of adrenergic neurons in the inner nuclear layer. This cell type was called the adrenergic pleomorph cell. Its processes ramify in the inner nuclear and inner plexiform layers. Adrenergic terminals occur in three more or less well developed sublayers of the inner plexiform layer, the layers being best developed in the Cebus monkey. Adrenergic terminals were also found around the cells of the inner nuclear layer and at the horizontal cells, where a scant sublayer is formed. More than one adrenergic sublayer of the inner plexiform layer has not been observed in primates previously, nor have the adrenergic terminals in the inner nuclear layer been observed previously in any species. The adrenergic pleomorph cells of the Cebus monkey also seem to be unique. The marked differences even between animals as closely related as some platyrhine monkeys call for caution when comparing the detailed function of the retina in different animals.

The localization of biogenic monoamines in ganglionic tissues from Anodonta piscinalis, Helix pomatia, and Buccinum undatum has been studied by means of the histochemical fluorescence method of Falck and Hillarp.

By means of a highly sensitive and specific histochemical method for the demonstration of certain biogenic monoamines a plexus of nerves containing a primary catecholamine has been demonstrated in the pars intermedia of the toad, Bufo arenarum. These nerves are restricted in distribution to the part of the gland which contains colloid vesicles (stored MSH ?) in the cells. The view is put forward, based on the results of pharmacological and surgical experiments, that the adrenergic nerves inhibit the release of the MSH from the pars intermedia. The origin of the nerves in the brain is unknown, but experiments with lesions have shown that it is not to be found in the nucleus periventricularis arcuatus.