Glyoxylic acid condensation: a new fluorescence method for the histochemical demonstration of biogenic monoamines

Early attempts to visualize cortical monoamine nerve terminals

The Falck-Hillarp, formaldehyde fluorescence method for the demonstration of monoamine neurons in a microscope was established in Lund, Sweden and published in 1962. In the same year Hillarp moved to Karolinska Institutet in Stockholm. Two years later Dahlström and Fuxe published the famous supplement in Acta Physiologica Scandinavica, describing the distribution of the dopamine, noradrenaline and serotonin cell groups in the rat brain. This landmark paper also represented an important contribution to an emerging discipline in neuroscience - chemical neuroanatomy. During the following years several modifications of the original method were developed, attempting to solve some shortcomings, one being the reproducible demonstration of noradrenaline nerve terminals in cortical regions. One result was the paper focused on in the present article, which also describes other efforts in the same direction going on in parallel, primarily, in Lund and Stockholm. As a result there was, in the mid 1970s, a fairly complete knowledge of the catecholamine systems in the rat brain. This article is part of a Special Issue entitled SI:50th Anniversary Issue.

Distribution and morphology of the catecholaminergic neural elements in the human hypothalamus

Previous studies have demonstrated that catecholaminergic, tyrosine hydroxylase (TH)-immunoreactive (IR) perikarya and fibers are widely distributed in the human hypothalamus. Since TH is the key and rate-limiting enzyme for catecholaminergic synthesis, these IR neurons may represent dopaminergic, noradrenergic or adrenergic neural elements. However, the distribution and morphology of these neurotransmitter systems in the human hypothalamus is not entirely known. Since the different catecholaminergic systems can be detected by identifying the neurons containing the specific key enzymes of catecholaminergic synthesis, in the present study we mapped the catecholaminergic elements in the human hypothalamus using immunohistochemistry against the catecholaminergic enzymes, TH, dopamine beta-hydroxylase (DBH) and phenylethanolamine-N-methyltransferase (PNMT). Only a few, PNMT-IR, adrenergic neuronal elements were found mainly in the infundibulum and the periventricular zone. DBH-IR structures were more widely distributed in the human hypothalamus occupying chiefly the infundibulum/infundibular nucleus, periventricular area, supraoptic and paraventricular nuclei. Dopaminergic elements were detected by utilizing double label immunohistochemistry. First, the DBH-IR elements were visualized; then the TH-IR structures, that lack DBH, were detected with a different chromogen. In our study, we conclude that all of the catecholaminergic perikarya and the majority of the catecholaminergic fibers represent dopaminergic neurons in the human hypothalamus. Due to the extremely small number of PNMT-IR, adrenergic structures in the human hypothalamus, the DBH-IR fibers represent almost exclusively noradrenergic neuronal processes. These findings suggest that the juxtapositions between the TH-IR and numerous peptidergic systems revealed by previous reports indicate mostly dopaminergic synapses.

The catecholamine neuron: Historical and future perspectives

My goals for this perspective are to enumerate what I consider to have been the major discoveries in the investigations of the central catecholamine neuron systems from the synaptic, cellular and systems physiological and neurohistochemical perspectives. To do so, I will emphasize here the synaptic and physiological aspects of the central noradrenergic (NE) system, considering both the past research and what we may expect to witness in the decades ahead.

Protein expression patterns of identified neurons and of sprouting cells from the leech central nervous system

It has previously been shown that cephalic, segmental, and caudal ganglia from the medicinal leech show differences in their protein composition. Here we studied whether the neuronal reorganization that occurs in cultured segmental ganglia from the medicinal leech is accompanied by detectable changes in the protein expression pattern. Using silver-stained two-dimensional gels we showed that after 5 and 12 days in culture changes in the protein patterns can be detected in isolated ganglia. The changes observed in the two-dimensional gels occurred concomitantly with a sprouting of serotoninergic neurites and a decreased transmitter content of dopaminergic neurites as shown by using the glyoxylic acid condensation reaction. In addition, we present evidence that Retzius cells, which can be identified by their characteristic morphology and action potential waveform, exhibit biochemically unique properties with respect to their protein expression pattern.

ACE inhibition improves cardiac NE uptake and attenuates sympathetic nerve terminal abnormalities in heart failure

Cardiac sympathetic nerve terminal dysfunction plays an important role in the downregulation of myocardial beta-adrenoceptors in heart failure. To determine whether chronic angiotensin-converting enzyme (ACE) inhibition improved cardiac sympathetic nerve terminal function and hence increased myocardial beta-adrenergic responsiveness, we administered ACE inhibitors to dogs with chronic right-sided heart failure (RHF) produced by tricuspid avulsion and pulmonary artery constriction. The RHF animals exhibited fluid retention, elevated right heart filling pressures, blunted inotropic response to isoproterenol, and reduced beta-adrenoceptor density. These changes were accompanied by decreases in right ventricular norepinephrine (NE) uptake and neuronal NE histofluorescence and tyrosine hydroxylase immunoreactive profiles. ACE inhibitors had no effect on the production of heart failure but greatly reduced the attenuation of cardiac NE uptake, neuronal NE histofluorescence, and tyrosine hydroxylase immunoreactive profiles. ACE inhibition also improved the inotropic response to isoproterenol and restored myocardial beta-adrenoceptor density. The changes probably are caused by reduction of cardiac NE release by ACE inhibition and may contribute to the beneficial effects of ACE inhibitor therapy in patients with chronic heart failure.

In vivo neuropharmacological and in vitro laser ablation techniques as tools in the analysis of neuronal circuits underlying behavior in a molluscan model system

1. This paper reviews the selective lesioning techniques employed to elucidate the role of the neurotransmitters dopamine and serotonin and single, identified interneurons in the feeding system of the pond snail Lymnaea stagnalis. 2. The pathway lesioning work reviewed in this paper showed that dopamine is necessary for the feeding response to occur and serotonin has a mainly modulatory role in the feeding system of Lymnaea. 3. The photoinactivation results reviewed here assist in the elucidation of the different roles that different types of interneurons play in the initiation and modulation of patterned neuronal activity underlying feeding.

Behavioural and biochemical changes in the feeding system of Lymnaea induced by the dopamine and serotonin neurotoxins 6-hydroxydopamine and 5,6-dihydroxytryptamine

The neurotoxins 5,6-dihydroxytryptamine (5,6-DHT) and 6-hydroxydopamine (6-OH-DA) were used to examine the role of monoamines in the feeding system of the snail Lymnaea stagnalis . Biting responses to sucrose were monitored up to 25 days after injection with drugs. Cerebral and buccal ganglia and cerebro-buccal connectives from the same groups of snails were examined for changes in serotonin and dopamine levels by high performance liquid chromatography and the glyoxylic acid histo-fluorescence technique. Twelve to eighteen days after injection with 5,6-DHT only 57% of the snails responded to sucrose with biting movements, compared with 98% of controls. Those that did respond had a longer latency to the first bite and the bites were of shorter duration and occurred at a lower rate when compared with controls. This was accompanied by a 39% drop in 5-HT levels in the cerebro-buccal commissure and nerves and a loss of fluorescence in the axons of the paired cerebral giant cells, the main serotonergic neurons involved in feeding. Earlier behavioural effects of injecting 5,6-DHT at 20 min and 3-4 h after injection could not be explained by specific changes in 5-HT levels. Recovery of both behavioural response and serotonin levels occurred between 22-25 days after injection. Injection of 6-OH-DA also inhibited feeding responses but the effects were quicker (1-3 days) and more dramatic, with only 40% of snails showing any biting response to food compared with a 98% response in controls. Reduction in dopamine (DA) levels of 40%, together with a loss of DA fluorescence in nerve fibres accompanied the reduction of behavioural responsiveness. An early (3-4 h) effect of 6-OH-DA injection could not be correlated with a specific reduction in DA levels. Behavioural responses and DA levels returned to normal by 4-7 days after injection. Both neurotoxins inhibited uptake of their target monoamines and this appeared to be the main mechanism for depleting 5-HT and DA. Early effects of neurotoxin injection probably directly inhibited monoamine uptake, whereas long-term inhibition was a secondary effect because of degeneration of nerve fibres. Neither neurotoxin caused release of monoamines. Results from both neurotoxins suggest that monoamines play an important role in the initiation and maintainance of the feeding response, the consummatory phase of feeding. Neither neurotoxin prevented the occurrence of the initial appetitive phase of feeding when snails orientate towards food in the experimental chamber.

The role of glutamate and GABA receptors in the generation of dorsal root reflexes by acute arthritis in the anaesthetized rat

1. In rats anaesthetized with pentobarbitone sodium, a unilateral acute arthritis was produced by the injection of kaolin and carrageenan into one knee-joint cavity. Four hours after injection, the medial articular nerve (MAN) was sectioned distally and recordings obtained from the proximal stump of the nerve. 2. Centrifugally conducted action potentials were recorded from the cut MAN following the development of arthritis. Acute dorsal rhizotomy, but not sympathectomy, prevented the action potentials, and so it is concluded that the action potentials represent dorsal root reflexes. 3. Central administration of either the GABAA receptor antagonist, bicuculline, or the non-NMDA receptor antagonist, CNQX, also prevented dorsal root reflexes in the MAN. 4. Neither the GABAB receptor antagonist, CGP35348, nor the NMDA receptor antagonist, AP7, altered the dorsal root reflexes in the MAN. 5. It is concluded that arthritis causes excess primary afferent depolarization in the dorsal horn of the spinal cord leading to dorsal root reflexes. It is proposed that these dorsal root reflexes contribute to the inflammation.

Development of dopamine-beta-hydroxylase-positive fiber innervation of the rat hippocampus

Development of the noradrenergic fiber innervation of the rat hippocampus by the locus coeruleus was examined immunohistochemically in fixed tissue from animals aged 4 days through 55 days postnatal. The presence of tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DBH) immunoreactive cells and fibers was evaluated in sections of hippocampus and locus coeruleus. Large, multipolar TH- and DBH-positive cells with long beaded fibers were visible within locus coeruleus at all ages; no immunopositive cell bodies were found in hippocampus. In hippocampal sections from mature animals (PN55), the highest density of DBH-stained fibers was found in stratum lucidum of CA3 and in the hilus and inner molecular layer of the dentate gyrus. Whereas similar patterns of fiber positivity were found at PN21 and PN10 (although with somewhat reduced density of immunopositive fibers), the pattern was quite different at PN4. Although fiber staining was relatively sparse at PN4, relative density of DBH fibers was highest in stratum radiatum of CA1 and subiculum. This change in staining pattern suggests that noradrenergic function in hippocampus may change as the rat matures. Double immunofluorescence techniques showed an overlap of DBH and TH positive fibers in all hippocampal regions at all ages. DBH immunostaining appeared to be somewhat more sensitive than the TH staining. These data made it impossible to confirm the presence of significant numbers of nonnoradrenergic, catecholamine-containing fibers in hippocampus.

Demonstration of immunoglobulin G with affinity for dopamine in cerebrospinal fluid from psychotic patients

Using an enzyme-linked immunosorbent assay, significantly raised concentrations of immunoglobulin G with affinity for the neurotransmitter dopamine were demonstrated in cerebrospinal fluid from psychotic patients. We have varied the antigen presentation in order to find a conjugate with low unspecific binding. The conjugation of dopamine to carbodiimide-activated poly-L-glutamic acid and that to activated succinimide ester of biotin are described. The use of glutaraldehyde conjugation is not recommended because of the risk of formation of tetrahydroisoquinolines. A strong correlation (r = 0.94, P < 0.001) between the results obtained with dopamine conjugated to poly-L-glutamic acid and dopamine conjugated to biotin was observed. Forty-two human cerebrospinal fluid samples from 20 psychotic patients, (12 with a bipolar disorder and 8 with schizophrenia) and 22 control patients, with various neurological diseases but no apparent psychiatric diseases were investigated. A significantly higher incidence (P < 0.001) of antibodies with affinity for dopamine were found in the group of psychotic patients compared with the neurological control group.

The microvasculature in skeletal muscle. VI. Adrenergic innervation of arterioles in normotensive and spontaneously hypertensive rats

A microanatomical study of the adrenergic nerve plexus on the arterioles in the spinotrapezius muscle of normotensive and spontaneously hypertensive rats was carried out. The spinotrapezius muscle was selected since its microvasculature has been reconstructed in previous studies of this series. A modified glyoxylic acid amine densification technique was used to visualize the major portion of the microvascular nerve plexus. The nerve plexus density was quantified in the form of fiber length per unit area of vascular smooth muscle media. The adrenergic innervation was found to be limited to the arterial/arteriolar side of the microcirculation and positioned in close vicinity to vascular smooth muscle, in line with previous reports. Substantial variations of the nerve plexus density could be detected along the arterioles. Arcade arterioles show a significant reduction of the adrenergic innervation compared to that of the thoracodorsal supply artery. There was a significant elevation of the nerve plexus density at the origin of the transverse arterioles at the arcade arterioles, a site that in the past has been shown to exhibit the highest microvascular tonus in all arterioles of this organ. Distal to this site, transverse arterioles exhibit a progressive reduction of adrenergic plexus density toward their capillary endings, in line with the termination of vascular smooth muscle in these small branches. Sporadic fiber extensions were encountered leading from some of the transverse arterioles into the capillary network per se, but no regular innervation was detected in capillaries or in venules. These results suggest that the transverse arterioles may play a central role in nervous control of blood flow to the capillaries of muscle. Compared with the Wistar and Wistar-Kyoto strain, the spontaneously hypertensive rats exhibit qualitatively a similar pattern, but show quantitatively a significantly higher plexus density in the thoracodorsal artery and the arcade arterioles, a factor that may contribute to the elevated arteriolar tone.

The effect of atherosclerosis on neuromodulation of sympathetic neurotransmission by neuropeptide Y and calcitonin gene-related peptide in the rabbit mesenteric artery

The neuromodulatory actions of neuropeptide Y (NPY) (0.1 microM) and calcitonin gene-related peptide (CGRP) (0.01 microM) on nerve-evoked contractions have been studied in the Watanabe heritable hyperlipidemic (WHHL) rabbit mesenteric artery from 4-, 6- and 12-month-old animals with New Zealand white (NZW) rabbits being used as age- and sex-matched controls. Nerve-evoked contractions in 12-month-old rabbits were smaller in WHHL in comparison to NZW rabbits, with no difference between the two strains of rabbit at 4 and 6 months of age. Both the potentiating effect of NPY and the inhibitory effect of CGRP on nerve-evoked contractions increased significantly at 12 months of age compared with responses measured in younger WHHL rabbits, and were greater than in 12-month-old control NZW rabbits. In contrast, the direct smooth muscle relaxant response of CGRP on raised-tone preparations was not different between the two strains of rabbit at any age. Both NPY-immunoreactive and CGRP-immunoreactive nerve fibres were less varicose in 6- and 12-month-old WHHL rabbits when compared with younger WHHL rabbits and NZW controls. In conclusion, this study shows that while nerve-evoked contractions are reduced, in the 12-month-old WHHL rabbit mesenteric artery, the neuromodulatory actions of NPY and CGRP are augmented.

Noradrenergic nerve fibers of the rectal mucosa in autonomic disorders: comparison of histochemical study with clinical severity and changes in plasma noradrenaline induced by standing

A histochemical study was carried out on the rectal mucosae biopsied from 20 patients with autonomic dysfunctions and 13 controls using a catecholamine fluorescent staining method, and the rectal noradrenergic nerve fiber lesions were compared with the severity of autonomic symptoms and disturbance of plasma noradrenaline increase in response to standing in 17 patients. In 9 patients with type I familial amyloid polyneuropathy and 1 with acute pandysautonomia, the number of fluorescent nerve fibers was greatly reduced, and the degree of depletion correlated well with the other 2 parameters showing the severity of autonomic dysfunction. In contrast, rectal noradrenergic nerve fibers were normally preserved in 10 patients with multiple system atrophy, although they suffered from severe autonomic symptoms with poor noradrenaline response to the postural loading. It is concluded that noradrenergic nerve fiber lesions in the biopsied rectal mucosa may represent the systemic involvement of sympathetic post-ganglionic nerves.

Dopamine-immunoreactive neurones in the central nervous system of the pond snail Lymnaea stagnalis

The distribution of dopamine and dopamine-immunoreactive neurones was studied in the central nervous system of the snail Lymnaea stagnalis. The results from immunocytochemical labelling were compared with those from the application of the glyoxylic acid fluorescence method and 6-hydroxydopamine-induced pigment labelling. Comparisons were also made between the number of dopamine immunoreactive neurones and the dopamine content of the ganglia, measured by high-performance liquid chromatography. Dopamine immunocytochemistry proved to be superior to the other two histochemical techniques in terms of specificity and sensitivity. The 6-hydroxydopamine-induced pigment labelling failed to prove a useful tool for the in vivo identification of all dopamine-containing neurones. The distribution and number of dopamine-immunoreactive neurones and levels of biochemically measured dopamine in specific ganglia showed a close correspondence. By using the results of the dopamine immunocytochemistry and glyoxylic acid technique, a detailed map of dopamine-containing neurones was constructed. Dopamine-containing inter- and intra-ganglionic axon tracts were also demonstrated. The mapping of dopamine-containing neurones will facilitate further neurophysiological analysis of dopaminergic neural mechanisms in Lymnaea.

Fluorescence histochemical techniques for catecholamines as tools in neurobiology

Formaldehyde-induced and glyoxylic-acid-induced fluorescence histochemistry permits the tissue localization of catecholamines in the central nervous system (CNS) and peripheral nervous system (PNS), and in culture. Counterstains such as ethidium bromide provide excellent background identification of specific innervated regions in both the CNS and the periphery. Use of fluorescence histochemistry with immunocytochemistry can elucidate catecholamine-peptide relationships. Gelatin-ink perfusion used with fluorescence histochemistry permits the investigation of neuro-vascular relationships and documentation of vascular and parenchymal compartmentation of innervation. Combined use of fluorescence histochemistry and retrograde tracing methods demonstrates the specific cellular sources of innervation of target regions. Micropunch neurochemical analysis provides quantitative data for correlation with fluorescence histochemistry within a target region of innervation, and microspectrofluorometric analysis provides a semi-quantitative evaluation of the amount of fluorophore within a target region or within specific subcellular compartments such as the cell body or terminals.

Catecholamine-containing neurons in the sheep brainstem and diencephalon: immunohistochemical study with tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DBH) antibodies

The present study describes the distribution and morphological characteristics of neurons and nerve fibers containing the catecholamine-synthesizing enzymes, tyrosine hydroxylase and dopamine-beta-hydroxylase, in the sheep brainstem and diencephalon on the basis of immunohistochemical procedures. Neurons and fibers were considered to be dopaminergic if they showed anti-tyrosine hydroxylase immunoreactivity, without corresponding anti-dopamine-beta-hydroxylase immunoreactivity. The structures labeled with both antisera were considered noradrenergic or adrenergic. The distribution of catecholaminergic neurons corresponds to that described by other authors with similar methods in the rat and in primates. The noradrenergic neurons belong to cell groups A1 to A7 and the dopaminergic neurons to cell groups A8 to A15. In almost all studied areas, the catecholaminergic innervation is similar to that observed in the other species. However, the central catecholaminergic systems of the sheep showed some specific characteristics: (1) groups A3 and A4, described in the rat, were not found, (2) group A14 contains fewer neurons than in the rat, (3) group A15 does not contain a dorsal but only a ventral portion, (4) there is a larger dispersion of neurons within each group, especially A6 and A7, than in rodents, and (5) there is a larger noradrenergic innervation of the catecholaminergic groups than in the other species.

A comparison of four techniques for mapping the distribution of serotonin and serotonin-containing neurons in fixed and living ganglia of the snail, Lymnaea

The distribution of serotonin and serotonin-containing neurons was studied in the ganglia of the CNS of the snail Lymnaea stagnalis. Results of the application of three different labelling techniques on wholemount preparations were compared with each other and with the serotonin content of the ganglia, measured by high-performance liquid chromatography. Serotonin immunocytochemistry resulted in the highest number of labelled neurons, but the more recently developed in vivo method of 5,6- or 5,7-dihydroxytryptamine-induced pigmentation also proved to be a reliable technique for the visualization of serotonin-containing cell bodies. In comparison with these two techniques, the glyoxylic acid fluorescence method appeared to be less sensitive. The distribution and number of serotonin-containing neurons and biochemically measured serotonin in specific ganglia showed a close correlation. By combining the results of the three labelling techniques, a detailed map of serotonin-containing neurons was constructed, and this was compared with maps of identified neurons prepared from earlier electrophysiological studies. Previously described serotonergic neurons were consistently found, as well as several new serotonin-containing cell types in the cerebral, visceral and parietal ganglia. A network of serotonin-containing inter- and intraganglionic axon tracts, and thin serotonergic fibres in the perineurium were also demonstrated. This in vivo and in vitro identification of serotonin-containing neurons will facilitate further neurophysiological analysis of serotonergic neural mechanisms in Lymnaea.

Central dopamine-synthesis regulation by the calcium-calmodulin-dependent system

The effects of the intraventricular (IVT) administration of calcium on the amount of dopamine (DA) in various regions of the mouse brain were analyzed immunohistochemically by using a microphotometry system. The DA levels in the nucleus accumbens and the lateral part of the neostriatum were increased by approximately 45% (p less than 0.01) and 25-35% (p less than 0.01), respectively, by the IVT administration of CaCl2 (10 mumol/kg). It was also found that this effect was abolished by the calmodulin antagonist, W-7 (4.2 micrograms/mouse, IVT). The brain regions in which the amount of DA was increased by calcium were areas where high levels of calmodulin and tyrosine hydroxylase are distributed. These findings suggest that the synthesis of central DA is regulated by calcium through a calmodulin-dependent system.

Consecutive diaphorase-acetylcholinesterase histochemistry in the myenteric plexus of frog stomach

An investigation was made on the frog stomach myenteric plexus with 2 different histochemical techniques. Neuronal perikarya were stained with nicotinamide-adenine-dinucleotide-diaphorase (NADHd), while the acetyl-cholinesterase (AChE) staining showed rather the axoarchitectonic arrangement of the frog myenteric plexus. In double-labelled "whole mounts", NADHd-positive cell bodies and AChE-positive nerve processes were revealed. Some of the nerve cells and neuronal processes did not exhibit AChE activity at all. Since glyoxylic acid-induced fluorescence (GIF) was not detected in the myenteric plexus, the presence of catecholamines can be excluded. As a consequence of these observations, we suggest the presence of a non-cholinergic, non-adrenergic intrinsic neuronal system in the frog stomach myenteric plexus, containing purines or peptides as transmitters.

Comparison of functional responses of canine coronary artery and saphenous vein

Functional responses of canine circumflex coronary arteries and saphenous veins before and after grafting surgery were assessed following physiologic and pharmacologic interventions. Developed tension of ringed segments of vessels was recorded isometrically. Dose-dependent responses to norepinephrine revealed significantly greater responses of saphenous veins than coronary arteries (maximal responses were 2.79 +/- 0.45 and 0.44 +/- 0.34 g, respectively; p less than 0.001). Sensitivity to norepinephrine [as evaluated by 50% effective dose (ED50) value] was 3.3 times greater in the saphenous veins (p less than 0.001). STA2, a synthetic thromboxane A2 analog (see Methods), produced similar contractions of both vessels [maximal responses were 2.13 +/- 0.37 g in saphenous vein and 1.64 +/- 0.85 g in coronary artery; p less than not significant (NS)], while sensitivity to STA2 of saphenous veins was 3.1 times greater than that of coronary arteries (p less than 0.001). In contrast to the foregoing responses, coronary arteries demonstrated significantly greater responses to potassium than saphenous veins (maximal responses were 2.16 +/- 0.71 g and 1.40 +/- 0.56 g, respectively; p less than 0.001). Moreover, coronary arteries revealed 1.6 times greater sensitivity than saphenous veins (p less than 0.001). When saphenous veins were transplanted into the femoral artery, the segments of the grafts (2 weeks or 3 months after surgery) revealed 4.0 and 1.7 times greater sensitivity (denervation supersensitivity) to norepinephrine and potassium than those of the control veins (p less than 0.01, respectively). Contractile tension response, however, decreased by at least 50% 3 months after surgery, most probably due to a thickened vessel wall and a reduced compliance.(ABSTRACT TRUNCATED AT 250 WORDS)

The organization of the cardiac ganglion of the axolotl (Ambystoma mexicanum)

The heart of the axolotl Ambystoma mexicanum was studied with histochemical methods to determine the distribution of neurons containing acetylcholine esterase, catecholamines and 5-hydroxytryptamine. The cardiac ganglion is made up of cholinergic nerve fibers and somata, and of catecholaminergic fibers. Small intensely fluorescent cells were found along blood vessels in the pericardial wall at the base of the heart, but not in the heart itself, except, in a few instances, in the region bordering the pericardial wall. Both the cholinergic and the catecholaminergic innervation of the heart were poorly developed at hatching and reached their mature state after a few months. Cholinesterase staining fibers appeared several weeks before catecholaminergic fibers. The number of postganglionic cholinergic neurons in the heart increased several-fold during the first month after hatching. Histofluorescence studies of organ cultures suggested that all the catecholamine present in the heart are of extrinsic origin. Liquid chromatography with electrochemical detection demonstrated that the dominant catecholamine in the heart is norepinephrine. No neurons containing 5-hydroxytryptamine were found.

Distribution of noradrenergic nerve fibers in canine nasal mucosa following selective neurectomies

In this study, we have used noradrenergic histofluorescence and selective neurectomies of the vidian, ethmoid and caudal nasal nerves to evaluate the distribution of postganglionic sympathetic fibers in the canine nasal mucosa. In conjunction with the histochemical localization of the noradrenergic fibers in the nasal mucosa after vidian neurectomy, the norepinephrine content of the mucosa was also evaluated using high-performance liquid chromatography. Unilateral neurectomy of the superior cervical ganglion (SCG) resulted in the unilateral disappearance of all noradrenergic histofluorescence in the nasal mucosa, while no morphological changes in noradrenergic fibers could be identified after neurectomy of the cervical sympathetic trunk 1 cm below the SCG. Ethmoid neurectomy caused the disappearance of noradrenergic fibers of the upper third of the nasal mucosa, while vidian neurectomy resulted in a partial loss of noradrenergic fibers in the lower two-thirds of the nasal mucosa. The loss was chiefly in the area adjacent to venous sinusoids and was responsible for 50% of the norepinephrine content of this tissue. We concluded that all the postganglionic sympathetic fibers are from the ipsilateral SCG. Some of them travel via the ethmoid nerve and innervate the upper third of the nasal mucosa. The remaining fibers travel via the vidian nerve and perhaps the vessel walls of the supplying arteries and innervate the lower two-thirds of the nasal mucosa. The vidian nerve chiefly innervates the venous sinusoids of the lower two-thirds of the nasal mucosa.

Serotonin as an alternative transmitter in sympathetic nerves of large cerebral arteries of the rabbit

The distribution of serotonin (5-HT)-like immunoreactive (5-HT-LI) nerves and the potential role of 5-HT as a vasoconstrictor transmitter in large cerebral arteries of the rabbit were examined. 5-HT-LI fibers with weak immunofluorescence were observed in the anterior cerebral, middle cerebral, and basilar arteries when fixed by immersion after dissection from exsanguinated animals. The 5-HT-LI fibers, however, were not detected in these arteries when fixed either in vitro or in situ after first being perfused with Krebs solution in situ to flush the blood component from the lumen prior to dissection. In these arteries, 5-HT-LI nerve fibers with intense immunofluorescence, however, reappeared following incubation with 5-HT in vitro. The intensity of the 5-HT-LI fibers seemed to be proportional to the duration and 5-HT concentration during incubation. Following chronic surgical sympathectomy, 5-HT-LI fibers were not detected in arteries before or after incubation with 5-HT. Transmural nerve stimulation elicited constriction in 50% of the control arterial segments examined. The constriction was not affected by ketanserin but was prevented by guanethidine and chronic surgical sympathectomy. The remaining arterial segments that did not respond on transmural nerve stimulation, however, became constrictive on transmural nerve stimulation following incubation with 5-HT in vitro. The constriction was blocked by ketanserin and clonidine. These results demonstrate that the large cerebral artery of the rabbit brain has extremely sparse or no authentic 5-HT-LI nerves.(ABSTRACT TRUNCATED AT 250 WORDS)

The distribution of sympathetic nerve fibres in the AV node and AV bundle of the bovine heart

The sympathetic nervous system has important effects on the properties of the heart, including the conduction of the impulse. However, it is not known how this nervous system is distributed in the atrioventricular (AV) bundle, which together with the AV node constitutes the only conduction pathway between the atria and ventricles in normal hearts. Therefore, in the present study the adrenergic innervation in the bovine AV node/AV bundle was examined by use of the glyoxylic acid induced method for histofluorescence demonstration of catecholamines. Acetylcholinesterase (AChE) histochemistry was also used. It was found that the AChE-positive nerve fascicles in these regions partly contain sympathetic nerve fibres, that sympathetic nerve fibres occur in the proximity of some of the ganglionic cells that occur outside the AV node/AV bundle, that the arteries supplying AV bundle tissue as well as AV nodal tissue have perivascular plexuses of sympathetic nerve fibres, and that there is a substantial number of sympathetic nerve fibres outside Purkinje fibre bundle surfaces. The observations give new insight into the question of the distribution of the sympathetic nerves in the AV bundle in relation to the distribution of these nerves in the AV node. Possible functional implications of the observations are discussed.

Effect of calcium on the histochemical distribution and intensity of biogenic amine-containing neurons in the mouse brain

The effect of calcium on the biogenic amine level and distribution in the mouse brain was investigated by a histochemical method using a microscopic photometer (Pl, Nikon). Histochemical fluorescence intensities in the corpus striatum and cortex cerebri regions were significantly increased by the intraventricular administration of CaCl2. This result suggests that calcium increases biogenic amine levels. These results are consistent with our previous pharmacological and biochemical findings.

Intramural neurons of the guinea-pig urinary bladder: histochemical localization of putative neurotransmitters in cultures and newborn animals

Histochemical methods have been used to study the distribution of putative neurotransmitters in the urinary bladder of newborn guinea-pigs and in cultures of intramural ganglia. Following the nicotinamide adenine dinucleotide (NADH)-diaphorase reaction which specifically labels nerve cell bodies, up to 66 ganglia were observed in stretch preparations of the newborn urinary bladder. Each ganglion contained 2-50 nerve cell bodies. Vasoactive intestinal polypeptide was localized in a few nerve cell bodies of intramural ganglia both in in situ and culture preparations. In the in situ preparations it was widely distributed in nerve fibres to the muscle, being most dense at the base of the bladder, and in some mucosal epithelial cells. Somatostatin was contained in numerous neuronal cell bodies in the detrusor muscle both in situ and in culture. Extensively distributed varicose fibres were found in culture and in the muscle, submucous and mucosal layers in situ. Substance P immunofluorescence was demonstrated in a few neuronal cell bodies in ganglia both in situ and in vitro, particularly in those of the mucosa at the base of the bladder. In the in situ preparations varicose nerve fibres containing substance P were seen in the muscle coats with greatest density in the bladder base. Met-enkephalin-immunoreactive nerve cell bodies were not seen either in situ or in culture. Nerve fibres in in situ preparations were found largely enveloping neuronal cell bodies within the ganglia. Neither serotonin-immunoreactive nor catecholamine-containing neuronal cell bodies were seen in the in situ bladder preparation. However, some nerve cell bodies in culture showed positive staining, possibly as a result of selective uptake of serotonin and catecholamine known to be contained in foetal calf serum in the culture medium or possibly as the result of increased synthetic activity in certain neurones in the culture situation. In whole-mount stretch preparations, no serotonin-immunoreactive nerve fibres were seen, but catecholamine-containing small intensely fluorescent cells and nerve fibres were observed. Acetylcholinesterase-positive nerve cell bodies and nerve fibres were observed both in in situ and culture preparations of the bladder. Quinacrine-positive nerve cell bodies (as an indicator of purinergic neurones) were found in numerous intramural neurones examined. in situ; however, under the culture conditions used, non-selective staining of all cell types occurred.

Histochemical studies of the adrenergic innervation of canine cerebral arteries

The glyoxylic acid method was used to examine the adrenergic innervation of the major cerebral arteries of the circle of Willis in dogs. Fluorescent nerve fibers were observed in whole-mount preparations of the part of the internal carotid artery lying in the cavernosus sinus, the anterior, middle and posterior cerebral arteries, the posterior communicating artery and the basilar artery. Adrenergic nerve fibers were most abundant in the proximal portions of the anterior, middle and posterior cerebral arteries as well as in the posterior communicating artery. The distal smaller arteries were less densely innervated than larger ones. The basilar artery contained a moderate number of fluorescent fibers while the internal carotid artery lying in the cavernosus sinus had a very sparse innervation. The peak wavelengths of the excitation and emission spectra of the fluorescence were analyzed by means of a microepifluorescence spectrophotometer and were about 415 and 465 nm, respectively. These values suggest that the fluorescent fibers are adrenergic ones containing norepinephrine.

Increase in neuronotrophic activity during the period of smooth muscle innervation

The expansor secundariorum is a unique smooth muscle of the avian wing that receives a dense sympathetic innervation and contains high concentrations of survival factors for sympathetic neurons. In the present study it has been possible to simultaneously examine the appearance of the neuronotrophic activity and the arrival of nerve fibres during the period of innervation. The results show that catecholamine containing nerve fibres can first be detected within the muscle on the fourteenth day of incubation (stage 40) followed by a rapid increase in the density of fibres during the next few days until the adult pattern is reached shortly before hatch. Biochemical estimation of the innervation process by measurement of dopamine beta-hydroxylase activity was supported by the histochemical findings. Estimation of neuronotrophic activity revealed that muscle from stage 40 embryos contains only low levels of activity which increases rapidly as innervation proceeds and further, that this increase in neuronotrophic activity was directly correlated with the dopamine beta-hydroxylase activities. Possible mechanisms regulating this dramatic increase in the specific activity of trophic factors are discussed.

Regulation of sympathetic trophic factors in smooth muscle

The level and nature of trophic activity present in the chicken expansor secundariorum muscle has been shown to be altered by denervation. This muscle receives a dense, sympathetic innervation and contains high concentrations of trophic factors, which were found to be immunologically and functionally distinct from mouse Nerve Growth Factor. In young birds, denervation increased the number of neurons which could be supported by muscle extract. This difference was apparent with regard to E8 to E16 sympathetic neurons. Innervated but not denervated extract was additive with NGF in promoting neurite outgrowth. In contrast, when extracts of denervated and innervated muscle from mature birds were examined, no difference was seen in the number of neurons supported by each extract. However when the denervated and innervated extracts from mature birds were combined more neurons were supported than by a saturating dose of either extract alone. Furthermore, muscle from mature birds responded to denervation only between 2 and 9 days, whereas in young birds the effect was apparent for at least 3 weeks. Analysis of intact, control muscles during the first 8 weeks posthatch demonstrated that the number of neurons that could be supported by the individual extracts varied with the age of the bird. It is concluded that denervation does not in all instances lead to an increase in trophic activity, but does produce a change in the nature of the activity present, such that a different neuronal subpopulation may be supported.(ABSTRACT TRUNCATED AT 250 WORDS)

An improved glyoxylic acid technique for the histochemical localization of catecholamines in brown adipose tissue

A glyoxylic acid method using cryostat sections to demonstrate catecholaminergic fibres of the central nervous system was modified to show the extent of the adrenergic innervation in rat brown adipose tissue. It revealed prominent interlacing fluorescent parenchymal fibres surrounding individual adipocytes. The density of this network of fine fibres was not evident using earlier techniques. The new method also confirmed the dense networks of adrenergic fibres associated with arterial vessels. Its specificity was verified by simultaneously performing radioenzymatic determinations of tissue catecholamine levels and histochemical studies of brown adipose tissue from normal and sympathectomized rats. Chemical sympathectomy with 6-hydroxydopamine resulted in a pronounced decrease in brown adipose tissue and heart catecholamine (noradrenalin and dopamine) levels. Significantly, in brown adipose tissue of sympathectomized animals no fluorescence could be detected in terminal nerves of either the parenchyma or those of vascular smooth muscles. Nevertheless, some intense fluorescence was seen in axon bundles. The findings suggest that catecholamines of the parenchymal innervation form a larger proportion of the total catecholamine content of brown adipose tissue than was previously believed, provide stronger support for direct control of the function of multilocular adipocytes, and also confirm unpublished data reporting considerable dopamine content in brown adipose tissue.

Evidence for the presence of cholinergic nerves in cerebral arteries: an immunohistochemical demonstration of choline acetyltransferase

The presence of cholinergic nerves in cerebral arteries of several species was investigated by an immunohistochemical method using antibodies against choline acetyltransferase (ChAT). In cats, pigs, rats, and dogs, ChAT immunoreactivities were found to be associated with large bundles and single fibers in the circle of Willis and anterior cerebral, middle cerebral, and basilar arteries. In the rabbit, the ChAT-immunoreactive (ChAT-I) nerves were also observed in the circle of Willis and anterior and middle cerebral arteries, but only few or none were found in the basilar and vertebral arteries. The ChAT-I nerves were found only in the adventitial layer of vessels examined. Superior cervical ganglionectomy did not appreciably affect the distribution of ChAT-I nerves. These results indicate the presence of cholinergic nerves in cerebral arteries. The distribution pattern of ChAT-I nerves was different from that of vasoactive intestinal polypeptide (VIP)-like-immunoreactive nerves and acetylcholinesterase-positive nerves. The possible coexistence of ChAT and VIP-like substance in the same neuron is discussed.

Developmental regulation of phenylethanolamine N-methyl transferase in avian sympathetic nerves

The presence of the catecholamine synthetic enzyme, phenylethanolamine N-methyl transferase (PNMT), has been detected in the expansor secundariorum, a smooth muscle of the avian wing. The concentration of the enzyme was estimated over a 10-week time course from 17 days incubation to 9 weeks posthatch and found to increase rapidly up until hatch in parallel with dopamine beta-hydroxylase activity, but then to fall precipitously to very low levels. The time course of the initial increase in activity corresponds to the presence of ingrowing sympathetic nerve fibres, and denervation of the expansor results in loss of greater than 80% of the PNMT activity. It is concluded that during the period of innervation the growing nerves contain the enzyme PNMT and therefore have the capacity to synthesize adrenaline, but that shortly after innervation is complete the capacity to synthesize adrenaline is lost. Several alternate mechanisms are proposed to explain the observations.

Immunohistochemical localization of endogenous nerve growth factor

Nerve growth factor (NGF) has been proposed as a trophic molecule essential for the development of sympathetic and primary sensory neurones. In newborn mice and rats, administration of nerve growth factor results in an increase in the number of surviving neurones, whereas administration of antiserum to NGF decreases neuronal survival. Thus it has been proposed that the factor is produced and secreted by the relevant target tissues to provide trophic support for the ingrowing nerves. The site of synthesis of nerve growth factor is still unknown, and it has been emphasized that a precise physiological role for the molecule cannot be ascribed until the cell types that produce it are known. I report here the use of immunohistochemistry to localize endogenous NGF in the rat iris, a tissue in which there is sound biochemical evidence for the production of NGF activity. Surprisingly, the results reveal that NGF can be detected readily in Schwann cells, but not in smooth muscle cells of the iris when it is sympathetically denervated or cultured.

Alpha 1- and beta-adrenergic and muscarinic cholinergic receptors in guinea-pig nasal mucosa

The alpha 1- and beta-adrenergic and muscarinic cholinergic receptors in guinea-pig nasal mucosa were measured for the first time by direct binding techniques using [3H]prazosin, [3H]dihydroalprenolol ([3H]DHA) and [3H]quinuclidinyl benzilate ([3H]QNB). The maximum binding capacities of [3H]prazosin, [3H]DHA and [3H]QNB in guinea-pig nasal mucosa were 20.1, 42.3, 159 fmol/mg protein, respectively. The dissociation constants of [3H]prazosin, [3H]DHA and [3H]QNB in guinea-pig nasal mucosa were 0.37, 0.77 and 1.5 nM, respectively. After the removal of the superior cervical ganglion in the guinea-pig, the number of alpha 1-adrenergic receptors was increased in the nasal mucosa while the number of beta-adrenergic and muscarinic receptors remained unchanged. Thus, alpha 1-adrenergic receptors are probably postsynaptic receptors in the target cells of sympathetic nerves, while beta receptors relate to the circulating catecholamines.

Altered cerebral vessel innervation in the spontaneously hypertensive rat

Autonomic innervation in the cerebral arterial walls of adult male spontaneously hypertensive rats and of normotensive Wistar-Kyoto rats was studied. When examined by fluorescence microscopy, dense catecholamine fluorescence was observed in anterior cerebral and middle cerebral arteries of both Wistar-Kyoto and spontaneously hypertensive rats. However, vertebral and basilar arteries and small pial arteries of Wistar-Kyoto rats received extremely sparse or no catecholamine fluorescence, whereas, in the respective regions of spontaneously hypertensive rats, catecholamine fluorescence was found to be significantly elevated. The endogenous norepinephrine content was also higher in cerebral arteries of spontaneously hypertensive than of Wistar-Kyoto rats. When examined ultrastructurally (potassium permanganate fixation), the incidence of granular vesicle-containing nerves, indicative of sympathetic nerves, was found to be significantly elevated in all cerebral arteries of spontaneously hypertensive rats examined. In contrast, the agranular vesicle-containing nerve, indicative of nonsympathetic nerves, with close synaptic cleft distance (less than 2 micron) was found to decrease or remain unchanged in the cerebral arteries of spontaneously hypertensive rats. These results suggest that cerebral sympathetic vasoconstriction may become more prominent than nonsympathetic vasodilation in spontaneously hypertensive rats. This finding lends further credence to the previous in vivo findings that cerebral sympathetic vasoconstrictor nerves become more functional and exhibit a protective effect against brain lesions during hypertension. The potential roles of neurogenic components involved in cerebral blood flow autoregulation are also discussed.

Identifiable neurons in the locust central nervous system that react with antibodies to serotonin

A detailed account is given of a number of neurons in the locust central nervous system that react with antibody raised to serotonin-albumin complex. The antibody was applied to a series of frozen sections of locust ganglia and visualized by using the peroxidase immunohistochemical procedure. The neurons described include certain afferents and their related neuropiles, a small number of efferents and several systems of interneurons, some of which are segmentally repeated, some run from the brain through the whole nerve cord, while others are confined to the brain. It has been possible to identify many of the neurons from previous descriptions obtained from cobalt, Golgi, and osmium ethyl gallate methods.

Aminergic innervation of cerebral veins. Histochemical comparison with extracranial veins

The density and distribution pattern of aminergic nerve fibers in intracranial and extracranial veins were compared by means of catecholamine histofluorescence studies. Extracranial veins (internal jugular, inferior caval, portal, renal, internal iliac, and femoral veins) showed quite a uniform distribution pattern. Large veins (jugular, caval, renal, and iliac veins) revealed a spiral pattern, and small veins presented as a meshwork (femoral vein) or in a longitudinal pattern (a branch of the femoral vein). In contrast, intracranial veins displayed more complex patterns: the dural sinus showed a longitudinal pattern and the internal cerebral vein and the superficial vein of Labbé revealed a meshwork of nerve fibers. The aminergic fibers were denser in cerebral veins (dural sinus and internal cerebral vein) than in extracranial veins. The complex distribution and the density of aminergic fibers in cerebral veins suggest that the aminergic innervation of the circulatory system may be more important in the brain than in the extracranial organs.

Distribution of fluorogenic monoamines in the gastrointestinal muscularure of Helix pomatia

By the use of a glyoxylic acid induced fluorescence method an intensive green fluorescence characteristic to catecholamines was observed on nerve fibres with varicosities, nerve bundles and perykaryons on wholemount stretch preparates of snail's gut. Considering the distribution of the fluorescent nerve elements and also the fluorescence intensity a decreasing gradient was revealed from the fore-gut through the stomach to the hind-gut.