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

Regional concentrations of noradrenaline and dopamine in rat brain

The concentrations of noradrenaline and lopamine of 92 brain regions have been measured by a radiometric method which enabled discrimination between noradrenaline and adrenaline. Almost all brain regions investigated contained both noradrenaline and lopamine in measurable amount. However, both catecholamines appeared to be unevenly distributed. Very high dopamine concentrations were measured in the olfactory tubercle, the nucleus accumbens, the caudate nucleus and the rostral part of the medial forebrain bundle; the globus pallidus, the nucleus tractus diagonalis and the nucleus septalis lateralis were also very rich in dopamine. Outside the telencephalon the dopamine concentrations were rather low, except in the median eminence and the area tegmentalis ventralis (Tsai), an area corresponding to the A10 region. High noradrenaline concentrations were measured in most hypothalamic nuclei. Relatively high concentrations of this catecholamine were also measured in several mesencephalic (the ventral part of the central gray, the nucleus raphe dorsalis and the nucleus cuneiformis) and pontine (the locus coeruleus and the nuclei parabrachiales) regions. The highest noradrenaline concentrations in the medulla oblongata were observed in the A2 region and the nucleus commissuralis, which contained at least twice as much noradrenaline as did the more rostral part of the nucleus tractus solitarii.

Fluorescence histochemical and electron-microscopical observations on the innervation of the atrial myocardium of the adult human heart

The existence of both adrenergic and cholinergic innervation of the atrial myocardium of the adult human heart was demonstrated by means of fluorescence induced by formaldehyde or glyoxylic acid and by electron microscopy. The adrenergic fluorescing axons (1) followed the course of blood vessels as typical perivascular nerve plexuses, and (2) formed a three-dimensional fairly dense nerve net obviously not related to the blood vessels. The varicosities frequently came into close apposition on myocardial cells. Several types of nerve terminals were differentiated at electron microscopy: (1) an "adrenergic" type containing small (diameter 450-700 A) dense-cored vesicles and usually (in various proportions) small "empty" and/or large (900-1500 A) dense-cored vesicles, (2) a "cholinergic" type containing small (ca. 500 A) "empty" vesicles and occasionally also some large (mean diameter ca. 1200 A) dense-cored vesicles, (3) a "pale" type containing only a few or no vesicles, (4) a "disintegrated" type containing degenerated mitochondria, autophagic vacuoles, and occasional normal-looking mitochondria, (5) nerve terminals containing a large number of mitochondria in addition to varying vesicle populations, and (6) a (possibly baroreceptive type of) nerve terminal containing myelinlike lamellated structures. The "disintegrated" and the "pale" types of nerve terminals possibly represent different stages of axonal degeneration, or may correspond to diminution in the transmitter substance concentration under certain pathophysiologic conditions, respectively. Nerve terminals crowded with mitochondria may be sensory and involved in mechano-or chemoreceptive functions. In preliminary experiments convincing evidence was obtained that the glyoxylic acid-induced fluorescence histochemical method will be suitable for comparative studies on (human) clinical specimens, e.g., for analyzing the degree of the functional activity of the intrinsic adrenergic innervation of the myocardium under various pathophysiologic conditions. The modification which appeared most appropriate for such studies is described in detail, and is proposed for use as a standard method in other similar or related studies on human clinical series. The essential criteria for analyzing the specimens at fluorescence microscopy are suggested as well.

Neurogenic sympathetic vasoconstriction of the rabbit basilar artery

When examined by fluorescence microscopy the rabbit basilar artery contains a rich adrenergic-like plexus at the adventitiomedial junction. The fluorescence disappears upon chronic reserpinization and bilateral superior cervical ganglionectomy. Transmural stimulation of intramural nerves a results in a response which is predominantly constrictor but also contains a small, inconstant dilator component. The constrictor response is abolished by chronic reserpinization, bilateral superior cervical ganglionectomy, and cold storage of the preparation. The constriction is prevented by the adrenergic neuron blocking agents guanethidine and bretylium but not by such alpha-adrenergic receptor blocking agents as phenoxybenzamine (PBZ), phentolamine, and tolazoline. Our results show that doses of the three latter agents sufficient to abolish contractions to norepinephrine (NE) in concentrations of up to 10(-2) M only potentiate and prolong the contractile response to nerve stimulation. The beta-adrenergic receptor blocking agent, propranolol, and inhibitors of NE neuronal uptake, such as desipramine (desmethylimipramine, DMI) and cocaine, do not influence the size of the neurogenic response. These results suggest that the vasoconstrictor component of the rabbit basilar artery response to transmural nerve stimulation (TNS) is mediated via sympathetic adrenergic-like neurons, but at the same time also raise the question whether the transmission process is typical of classic adrenergic neuroeffector mechanisms.

Dopaminergic innervation of the rat prefrontal cortex: a fluorescence histochemical study

After the destruction of the noradrenergic ascending pathways, the localization of frontal cortical fields receiving fibers from the dopaminergic mesocortical system has been studied in rats, using a glyoxylic-paraformaldehyde method. The dopaminergic innervation was distributed in two main areas. The area of highest density was a medial field which spread in the medial cortex anterior and dorsal to the genu of the corpus callosum. It did not reach the shoulder region except in the foremost part of the frontal lobe where dopaminergic fibers were scattered in the whole cortex, including the molecular layer. A deep sulcal field was situated between the dorsal bank of the rhinal sulcus and the lateral cortex above it. In addition, a moderately dense band of dopaminergic fibers was observed between the corpus callosum and the anterior commissura, beside the accumbens nucleus. Similar data were obtained with dopamine uptake experiments on reserpine-treated but otherwise normal animals. The frontal areas receiving dopaminergic innervation coincide strikingly with the 'prefrontal cortex' as defined by neuroanatomical studies, which is assumed to be more or less equivalent to the prefrontal cortex of primates and derives direct projections from the amygdala. The functional implications of these findings are discussed.

Intraventricular 6-hydroxydopamine lowers isolation-induced fighting behavior in male mice

Male mice with high isolation-induced fighting tendencies were administered 200 mug 6-OHDA or vehicle intraventricularly and tested for fighting tendency for up to 10 weeks until sacrifice, and assayed for brain NE levels. A strong correlation was found between NE depletion and reduced fighting tendency after 6-OHDA treatment. The depressed fighting by mice with less than 200 ng. NE/g persisted throughout a series of test fights, indicating no recovery in fighting behavior throughout the survival time.

An in vitro study of prolonged vasospasm of a rabbit cerebral artery

Longitudinal stretch of the rabbit basilar artery produces local injury followed by prolonged circular constriction. After stretching and rapid release in vitro localized constrictions promptly occurred. This could be prevented by prior treatment with cyanide or calcium-free solution. Once produced, constrictions persisted for more than 72 hours. Previously induced constriction was not reversed by treatment for two hours with cyanide or by removing calcium. Histological observation indicated that constricted areas were associated with a discrete circumferential rupture of the internal elastic lamina and disruption and thinning of the underlying media. Specific catecholamine fluorescence at the adventitio-medial junction was unchanged in constricted areas. The relationship between smooth muscle cell length and resting tension of artery segments with and without constrictions was compared. Segments with constrictions had a shorter muscle length for any given resting tension, which confirms that constriction was not due to passive collapse of the vessel wall. These findings suggest that injury of cerebrovascular smooth muscle may result in essentially irreversible vasoconstriction. Such a mechanism could contribute to the pathogenesis of prolonged cerebral vasospasm after SAH or traumatic injury to the cerebrum.

Catecholaminergic axo-axonic synapses in the nucleus of the tractus solitarius (pars commissuralis) of the cat: possible relation to presynaptic regulation of baroreceptor reflexes

A study was performed on adult cats to investigate synaptic structures of nerve terminals in the commissural portion of the nucleus of the tractus solitarius (NTS); a site where the cardiovascular afferent fibers terminate and where a dense plexus of adrenergic element also resides. Synaptic contacts observed in the commissural portion were predominantly axo-dendritic but a smaller number of axo-somatic synapses were also recognized. A third type of junction, axo-axonic, appears to be unique to the commissural portion of the nucleus, since no axo-axonic contacts were encountered in the medial and ventrolateral portions of the NTS. By labeling with the 'false' neurotransmitter 5-hydroxydopamine (5-OHDA), three types of axo-axonic contacts with different presynaptic components could be identified; namely, axon varicosities with small clear spherical vesicles, axon varicosities containing flat synaptic vesicles and others with small cord vesicles labeled with 5-OHDA. Postsynaptic components were always axon varicosities with clear spherical vesicles. After surgical denervation of the IXth and Xth cranial nerves, no degenerated axon varicosities were observed in the presynaptic side in the axo-axonic contact. The present study clearly demonstrates that the commissural portion of the NTS contains axo-axonic synapses and some of the adrenergic axons in this area provide the presynaptic components for this type of synapse. Possible roles of adrenergic nerves to presynaptic regulation of baroreceptor reflexes are discussed.

Cryostat technique for central nervous system histofluorescence

This paper offers a technique for obtaining monoamine histofluorescence in the CNS by means of formaldehyde perfusion followed by cryostat sectioning. No freeze-drying is involved. Cryostat sections are exposed to formaldehyde vapor to complete the fluorophore formation. The fluorescence thus obtained is bright, well localized, and does not require loading the animals with precursors. The anatomical distribution of the pathways is identical to that obtained with the classical technique. Furthermore, the fluorescence is reversible by sodium borohydride, and exhibits the expected changes in intensity with pharmacological manipulations. The sections can be exposed to a cold aqueous medium for as long as 15 min with minimal diffusion of fluorophore; this suggests potential for combining monoamine histofluorescence with other visualization techniques.

Nonsympathetic dilator innervation of cat cerebral arteries

The results presented provide strong support for the presence of vasodilator innervation in the cat cerebral arteries. The dilator innervation is neither adrenergic nor cholinergic and does not originate in the superior cervical ganglia. The nature of the vasodilator transmitter is unidentified. Such innervation, however, may be involved in the regulation of cerebral blood flow, especially in view of the capability of some cat cerebral vessels to develop intrinsic muscle tone.

Histochemical characterization of a neocortical projection of the nucleus locus coeruleus in the squirrel monkey

Histochemical evidence is presented for a catecholamine-containing projection from the nucleus locus coeruleus to the neocortex in the squirrel monkey. The innervation of superior temporal gyrus has been examined in particular. Glyoxylic acid-induced fluorescence shows an extensive arborization of fine, catecholamine-containing fibers with prominent varicosities in all layers of the neocortex. The nucleus locus coeruleus is identified as a source of these fibers by both ortho- and retrograde axonal tracing techniques. After injection of horseradish peroxidase into the neocortex, labelled cell bodies are localized throughout the major portions of the locus coeruleus. Conversely, after microinjection into the nucleus locus coeruleus, tritiated proline is transported into the neocortex where it appears within fibers similar in distribution to those revealed by fluorescence histochemistry. Both transport techniques indicate that cortical projections of the locus coerculeus originate from both ipsilateral and contralateral nuclei.

Formation of a functional adrenergic input to intraocular cerebellar grafts: ingrowth of inhibitory sympathetic fibers

The intraocular transplantation technique was used to study the ingrowth of peripheral sympathetic adrenergic nerves from the iris into transplants of fetal rat cerebellum, and the possible function of these nerves. The transplants, grown in oculo for one-half to eight months, were analyzed by fluorescence histochemistry and electrophysiological techniques. Peripheral sympathetic adrenergic fibers from the iris were able to grow into the cerebellar transplants and arborize in a pattern similar to that in situ, appearing in all three cortical layers and the noncortical areas of the transplants. The density of visible nerves without pretreatment and after preincubation in 10(-6) or 10(-5) M alpha-methylnorepinephrine was comparable to mature rat cerebellum. The spontaneous discharge of the Purkinje cells in oculo was inhibited by microiontophoresis of norepinephrine (NE) and amphetamine in sympathetically innervated, as well as sympathectomized transplants denervated by ganglionectomy. The NE response was blocked by the adrenergic beta-receptor blocker MJ-1999. GABA also inhibited the Purkinje cell activity while glutamate accelerated the discharge. Parenteral amphetamine inhibited Purkinje cell activity in sympathetically innervated transplants, but was ineffective in denervated transplants. The Purkinje cell spontaneous activity was inhibited by electrical stimulation of the NE fiber input through the cervical sympathetic trunk. This inhibition could be antagonized by parenteral reserpine or the beta-adrenergic antagonist propranolol. The responses of the Purkinje cells within the transplants to drugs and transmitters mimic those of the adult rat in situ. In view of the fluorescence histochemical evidence for an ingrowth of peripheral sympathetic adrenergic fibers into the cerebellar transplants, and the results of stimulating the sympathetic trunk, it is suggested that peripheral adrenergic fibers may be able to establish functional connections with the Purkinje cells similar to the cerebellar adrenergic synapses normally formed in situ by fibers from the locus coeruleus.

Catecholamines in mutant mouse cerebellum: fluorescence microscopic and chemical studies

Catecholamine-containing fibers have been examined in the cerebella of normal and hypocerebellar mutant mice using Falck-Hillarp and glyoxylic acid histofluorescence techniques. The amounts of norepinephrine and dopamine were also determined chemically in the same mutants. Green fluorescent fibers in cerebella of normal mice are similar in size and distribution to those described in the rat. Weanling and adult weaver, reeler and staggerer mice all manifest greatly increased specific catecholamine fluorescence per unit area in cerebellar cortex, but the patterns of fluorescent fibers are distinctive. In weaver, the fibers are of normal diameter, surround Purkinje cell bodies and appear to climb along major dendrites. In reeler, similar fibers form a plexus around cortical and non-cortical Purkinje cells; relatively normal fluorescent fiber patterns are present in well-organized cortical regions, while stouter disoriented fibers course through the shallow molecular layer in disorganized regions. Staggerer cerebellar cortex exhibits the greatest fluorescence with most terminals appearing as matted tangles adjacent cell bodies. Clearly defined fibers, however, can be distinguished in the molecular layer running perpendicular to the pia or for long distances in the coronal plane parallel to the pia. The major catecholamine determined chemically is norepinephrine. Reeler cerebella contain normal absolute levels and a doubled concentration of norepinephrine. In contrast, and despite the fluorescence findings, the total norepinephrine content of weaver and staggerer cerebella is significantly reduced and concentrations are not significantly different from normal.

Simultaneous fluorescence histochemical demonstration of catecholamines and tryptophyl-peptides in endocrine cells

Simple and efficient fluorescence histochemical methods for the concomitant demonstration of tryptophyl-peptide-containing cells and dopamine-containing cells have been developed in this study. Combined formaldehyde and chloral vapour or solution of 5% glyoxylic acid monohydrate in n-butanol induced concomitantly strong yellow fluorescence in the tryptophyl-peptide-containing cells and moderate green fluorescence in the dopamine-containing cells in the sections of the freeze-dried adenohypophysis.

Evidence of an incerto-hypothalamic dopamine neurone system in the rat

With the recently introduced glyoxylic acid histochemical fluorescence method, a previously unknown catecholamine-containing fibre system has been revealed in the zona incerta, hypothalamus and the caudal septum. These fibres, designated the incerto-hypothalamic system, have a characteristic, very delicate, finely varicose appearance, and they have a weak fluorescence, indicating an unusually low intra-neuronal amine content. On the basis of their distribution a caudal and a rostral part can be discriminated: the caudal part extends from the area of the dopamine-containing cell bodies in the caudal thalamus, the posterior hypothalamic area and the medial zona incerta (the A11 and A13 cell groups) into the dorsal part of the dorso-medial nucleus and the dorsal and anterior hypothalamic areas; the rostral part extends from the area of the rostral periventricular dopaminergic cell system (the A14 cell group) into the medial preoptic area and the periventricular and suprachiasmatic preoptic nuclei. The system probably extends also into the most caudal portion of the lateral septal nucleus. From a series of lesions and in vitro uptake studies, evidence has been obtained that the incerto-hypothalamic fibres are the projections of short, intradiencephalic dopaminergic neurones whose cell bodies are located in the A11, A13 and A14 cell groups. The projection areas of these neurones signify an involvement of the system in the control of secretion of pituitary hormones.

Monoamine distribution in primate brain. I Catecholamine-containing perikarya in the brain stem of Macaca speciosa

The distribution of catecholamine-containing cell bodies was examined in the brain stem of Macaca speciosa using the Falck-Hillarp histofluorescence technique. Extensive accumulations of such cells were seen in the ventral tegmental area, locus coeruleus, mesencephalic reticular formation and ventrolateral reticular formation of pons and medulla. This distribution was compared to that previously reported in rat, cat, squirrel monkey and human brain. Apparent species dissimilarities and similarities are reported.

Demonstration of catecholamines in peripheral adrenergic nerves in stretch preparations with fluorescence induced by aqueous solution of glyoxylic acid

Fluorescence induced by aqueous solution of glyoxylic acid and formaldehyde-induced fluorescence of catecholamines were compared for the demonstration of peripheral adrenergic nerves in stretch preparations. Glyoxylic acid was better than formaldehyde for the demonstration of the adrenergic nerves. On the other hand, the formaldehyde was better than glyoxylic acid for the demonstration of biogenic amines in cell bodies.

The use of glyoxylic acid for the fluorescence histochemical demonstration of peripheral stores of noradrenaline and 5-hydroxytryptamine in whole mounts

The reactions of glyoxylic acid with peripheral stores of noradrenaline and 5-hydroxytryptamine to provide a fluorescence histochemical method for their localization have been investigated. Incubation in glyoxylic acid, followed by drying and heating of whole mount preparations gives an intense and well localized reaction. For incubation, a concentration of 2% glyoxylic acid, buffered to pH 7 at room temperature for 30 minutes gives ideal results. The method is equally good if the pH is varied in the range 6 to 9 or if the tissue is stored in the incubation mixture for up to 6 hours. Ideal development of the fluorophore requires an initial excess of moisture in the tissue, that this moisture is driven off during development, and that the tissue is protected from further moistening. A suitable method of achieving these ends is to heat partially dried tissue at 100 degrees C for 4 minutes and then cover it with paraffin oil. 5-hydroxytryptamine can be readily distinguished from noradrenaline because it forms a fluorophore after reaction at pH 3.5, whereas noradrenaline does not. Both amines can be visualized after incubation at neutral pH. Comparison with the formaldehyde vapour technique reveals three main advantages (and no disadvantages) of the glyoxylic acid method: (1) it gives a finer localization with higher fluorescence yield, (2) the glyoxylic acid method is less susceptible to variations in procedure and, (3) it is both simpler and quicker to apply.