Dopamine beta-hydroxylase in health and disease

Increased dopamine-beta-hydroxylase-like immunoreactivity in non-noradrenergic axons supplying the guinea-pig uterine artery after 6-hydroxydopamine treatment

We have reinvestigated the immunohistochemistry of autonomic axons supplying the guinea-pig uterine artery to determine whether non-noradrenergic paracervical ganglion neurons projecting to the artery contain immunoreactivity to dopamine-beta-hydroxylase (DBH) or somatostatin (SOM) in addition to neuropeptide Y (NPY) and vasoactive intestinal peptide (VIP). In untreated arteries no VIP axons had immunoreactivity to tyrosine hydroxylase (TH), although 9% had immunoreactivity to DBH. Somatostatin immunoreactivity was detected in 25% of non-noradrenergic axons containing NPY and VIP. After in vivo treatment with 6-hydroxydopamine (6-OHDA), noradrenergic axons containing immunoreactivity to NPY, DBH and TH were absent from the adventitia-medial junction. However, 65-70% of the non-noradrenergic axons with NPY and VIP showed DBH immunoreactivity after 6-OHDA. These axons did not show catecholamine fluorescence after incubation with pargyline together with noradrenaline, dopamine or L-DOPA. The number of axons with SOM immunoreactivity increased by 44% after 6-OHDA treatment, but only 24% of SOM axons had DBH immunoreactivity. Surgical destruction of the non-noradrenergic autonomic axons in 6-OHDA-treated animals led to the loss of all DBH immunoreactivity. These results demonstrate that DBH immunoreactivity can be detected in a small proportion of non-noradrenergic axons supplying uterine arteries from untreated animals. After chemical sympathectomy with 6-OHDA, the levels of DBH immunoreactivity in axons of non-noradrenergic neurons increased, and more axons with DBH immunoreactivity were detected. DBH immunoreactivity seemed to increase preferentially in axons with NPY and VIP, but not SOM. The number of NPY, VIP axons containing SOM also increased after 6-OHDA. These findings demonstrate that peripheral neurons containing several different potential neurotransmitters can change their levels of neuropeptides and transmitter-synthesizing enzymes in response to local environmental changes.

Co-existence of neuropeptides in sympathetic, cranial autonomic and sensory neurons innervating the iris of the guinea-pig

We have used double-labelling immunofluorescence to identify the peptide content of autonomic and sensory neurons innervating the iris of albino guinea-pigs. Four major classes of neurons were identified on the basis of their distributions, origins and immunohistochemical characteristics. A dense plexus of noradrenergic axons in the constrictor and dilator muscles of the iris originated from the superior cervical ganglion, and contained immunoreactivity (IR) to both neuropeptide Y (NPY) and dynorphin (DYN). The constrictor and dilator muscles were also supplied with a dense plexus of axons with IR to substance P (SP). These axons probably originated from SP-IR nerve cell bodies located along the ciliary nerves, and are almost certainly the same axons as those producing cholinergic pupilloconstriction. The iris was also innervated by unmyelinated, capsaicin-sensitive axons with IR to both SP and calcitonin gene-related peptide. Most of these axons also contained IR to DYN and some were also IR for cholecystokinin. These axons are almost certainly sensory. Axons containing IR to both NPY and vasoactive intestinal peptide (VIP) were common in the ciliary processes, and also formed a sparse plexus near the ciliary margin of the dilator muscle. Following surgical sympathetic denervation these axons showed IR for dopamine-beta-hydroxylase; they seemed to originate from the sphenopalatine ganglion. These results demonstrate that there are well-defined patterns of coexistence of neuropeptides in the autonomic and sensory neurons supplying the iris of guinea-pigs. To understand the physiological roles of these peptides, it will be necessary to consider the possibility of complex interactions between them.

Paracervical ganglia of the female rat: histochemistry and immunohistochemistry of neurons, SIF cells, and nerve terminals

The paracervical ganglia of the female rat were studied to elucidate the variety of neural elements in the ganglia. Light and electron microscopy, histochemistry, and immunohistochemistry were employed to reveal subtypes of neurons; small, intensely fluorescent (SIF) cells; and nerve terminals and to examine the relationships between these elements. On the basis of their histochemical markers, four subtypes of principal neurons were identified: acetylcholinesterase (ACHE)-positive, noradrenergic, neuropeptide tyrosine-immunoreactive (NPY-I), and vasoactive intestinal polypeptide-immunoreactive (VIP-I). The NPY-I neurons appeared to be the most numerous and the noradrenergic the least common type of neuron. Four subtypes of chemically coded SIF cells were revealed: catecholamine-containing, NPY-I, and those immunoreactive for calcitonin-gene-related peptide (CGRP-I) and cholecystokinin-octapeptide (CCK-8-I). The SIF cells were present as single cells among and adjacent to principal neurons and as large clusters near the edges of the ganglia or in nearby nerve trunks. Synaptic contacts on SIF cells, or between SIF-cell processes and neurons, were not observed. Seven subtypes of nerve terminals were stained: ACHE-positive, CGRP-I, CCK-8-I, VIP-I, substance P-I, enkephalin-I, and atrial natriuretic factor-I. Nerve terminals enwrapped the neurons as perineuronal plexuses in synaptic-like relationships. These results demonstrate that the paracervical ganglia of the female rat are a complex system of neural elements. For example, several classes of chemically coded neurons, SIF cells, and terminals exist in the ganglia. Each of these components contains a number of substances, some of which are putative neurotransmitters, which could influence activity in the ganglia or in the effector organs innervated by the ganglia.

Nerve fibers containing neuropeptide Y in the cerebrovascular bed: immunocytochemistry, radioimmunoassay, and vasomotor effects

Perivascular nerve fibers containing neuropeptide Y (NPY)-like immunoreactivity were identified around cerebral blood vessels of human, cat, guinea pig, rat, and mouse. The major cerebral arteries were invested by dense plexuses; veins, small arteries, and arterioles were accompanied by few fibers. Removal of the superior cervical ganglion resulted in a reduction of NPY-like material in pial vessels and dura mater. Pretreatment with 6-hydroxydopamine or reserpine reduced the number of visible NPY fibers and the concentration of NPY in rat cerebral vessels. Sequential immunostaining with antibodies toward dopamine-beta-hydroxylase (DBH) (an enzyme involved in the synthesis of noradrenaline) and NPY revealed an identical localization of DBH and NPY in nerve cell bodies in the superior cervical ganglion and in perivascular fibers of pial blood vessels, suggesting their coexistence. Administration of NPY in vitro resulted in concentration-dependent contractions that were not modified by a sympathectomy. The contractions induced by noradrenaline, 5-hydroxytryptamine, and prostaglandin F2 alpha and the dilator responses to calcitonin gene-related peptide were not modified by NPY in rat cerebral arteries. However, the constrictor response to NPY was reduced by 70% in the presence of the calcium entry blocker nifedipine, and abolished following incubation in a calcium-free buffer. These data suggest an interaction of NPY at a postsynaptic site, which for induction of contraction may open calcium channels in the sarcolemma of cerebral arteries.

Neuropeptide Y-like immunoreactivity is absent from most perivascular noradrenergic axons in a marsupial, the brush-tailed possum

Noradrenergic perivascular axons were demonstrated in all systemic arteries and veins of a marsupial, the brush-tailed possum (Trichosurus vulpecula), by a catecholamine fluorescence procedure and with antisera directed against the catecholamine-synthesizing enzymes tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (D beta H). Perivascular axons with neuropeptide Y-like immunoreactivity (NPY-LI) were not found in most systemic arteries and veins using antisera which recognize NPY and other members of the pancreatic polypeptide family in diverse vertebrate species. The exceptions were the renal, coeliac, main mesenteric and iliac arteries, where up to 50% of axons with TH-LI or D beta H-LI also showed NPY-LI with two of the 4 antisera used. No noradrenergic nerve cell bodies in thoracic sympathetic ganglia had NPY-LI, whilst 3% of noradrenergic nerve cell bodies in lumbar sympathetic chain ganglia had weak NPY-LI. This marsupial is the first vertebrate species found to date in which the majority of perivascular noradrenergic axons do not contain NPY-LI. If these axons contain an as yet unidentified neuropeptide, it is unlikely to be closely related to NPY.

Existence and coexistence of peptides in nerves of the mammalian ovary and oviduct demonstrated by immunocytochemistry

The immunocytochemical distribution of substance P (SP), gastrin releasing peptide (GRP), vasoactive intestinal polypeptide (VIP), peptide histidine isoleucine (PHI), and neuropeptide Y (NPY) was studied in the ovary and the Fallopian tube (oviduct) of rats, guinea-pigs, cows, pigs and humans. Generally, the nerve supply was better developed in the oviduct than in the ovary. GRP fibers were most scarce in all tissues. Nerves containing SP were particularly numerous in the oviduct of rat and guinea-pig, supplying the muscular wall and blood vessels. VIP and PHI coexisted in dense plexuses of nerves, not only around blood vessels but also in the follicular wall and the interstitial gland of the ovary, as well as within the smooth muscle layers and subepithelially in the oviduct. The general distribution of NPY was similar, but these immunoreactive nerves were even more numerous. Sequential staining for dopamine-beta-hydroxylase and NPY together with results of chemical sympathectomy with 6-hydroxydopamine suggested that NPY was stored in the noradrenergic sympathetic nerves.

Co-localization of neuropeptide Y, vasoactive intestinal polypeptide and dynorphin in non-noradrenergic axons of the guinea pig uterine artery

Two major populations of perivascular axons containing immunoreactivity to neuropeptide Y (NPY) have been revealed in the main uterine artery of the guinea pig by immunohistochemical procedures which allow the simultaneous visualization of two antigens. One population contained immunoreactivity to dopamine-beta-hydroxylase (D beta H) and was presumably noradrenergic. The other main population of axons with NPY-like immunoreactivity (NPY-LI) did not have D beta H-like immunoreactivity (D beta H-LI) and was presumably non-noradrenergic. These non-noradrenergic axons also contained immunoreactivity to vasoactive intestinal polypeptide (VIP) and dynorphin (DYN). Indeed, nearly all axons with VIP-LI also contained NPY-LI and DYN-like immunoreactivity (DYN-LI). NPY constricted the uterine artery perfused in vitro, whilst VIP dilated uterine arteries preconstricted with noradrenaline or NPY. Thus, we have evidence for the coexistence of a vasoconstrictor peptide and a vasodilator peptide in the same non-noradrenergic perivascular axons, which also contain an opioid peptide, dynorphin.

Inhibition of the retrograde axonal transport of dopamine-beta-hydroxylase antibodies by the calcium ionophore A23187

High levels of calcium, as well as calcium ionophores, have been reported to inhibit the anterograde transport of proteins. The effect of the calcium ionophore, A23187, on the retrograde axonal transport of proteins was therefore investigated. The uptake of antibodies to dopamine-beta-hydroxylase (anti-D beta H) by sympathetic nerve terminals in the iris and their subsequent accumulation in the superior cervical ganglion was inhibited by up to 65% by A23187 (6 nmol, i.o.). At this dose, catecholamine fluorescence in the iris was reduced, indicating a high rate of exocytosis, but tyrosine hydroxylase levels and the capacity of the treated irides to take up noradrenaline were unaffected. Higher amounts of A23187 (28 nmol, i.o.) did not cause a greater degree of inhibition of retrograde transport. However, this dose was toxic to the neurons, as shown by a 68% decrease in the ability of the nerve terminals in the iris to take up [3H]noradrenaline. This loss of function occurred gradually over a 12-h period. On the other hand, tyrosine hydroxylase levels were unaffected by 28 nmol A23187. The toxicity of A23187 may be a consequence of a build up in intracellular calcium, but such toxicity did not lead to any apparent loss of nerve terminals within a 3-day period.

Neuropeptide Y-like immunoreactivity in perivascular nerve fibres of the guinea-pig

The distribution of perivascular nerve fibres displaying neuropeptide Y-like immunoreactivity was studied in the guinea-pig. Generally, neuropeptide Y fibres were numerous around arteries and moderate in number around veins. In the heart, immunoreactive fibres were numerous in the auricles and the atria (epi- and endocardium) whereas the ventricles had a more scarce supply. The coronary vessels were richly supplied with fibres. Around large elastic and muscular arteries the fibres formed well developed plexuses. Small arteries in the respiratory tract, the gastrointestinal tract and the genito-urinary tract received a particularly rich supply. In the liver, spleen and kidney only few perivascular fibres were seen. Since immunoreactive fibres around blood vessels disappeared upon surgical or chemical sympathectomy, and sequential immunostaining with antisera against dopamine-beta-hydroxylase (a marker for adrenergic neurons) and against neuropeptide Y revealed their co-existence, it is concluded that neuropeptide Y fibres around blood vessels are sympathetic and adrenergic.

Neuropeptide Y: occurrence and distribution in dental pulps

Nerve fibers displaying neuropeptide Y (NPY) immunoreactivity were seen in the dental pulp of several mammals, including man. Generally, the NPY fibers were more numerous in the apical part than in the coronal part and were distributed around small blood vessels and as single fibers in the pulpal stroma. Sequential staining with antibodies against the enzyme dopamine-beta-hydroxylase (DBH), a marker for adrenergic neurons, and NPY showed that DBH and NPY were located in the same perivascular nerve fibers. Further, since chemical and surgical sympathectomy caused the disappearance of pulpal NPY fibers, it is conceivable that NPY fibers in the dental pulp are identical with adrenergic ones. There is thus a morphological basis for suggesting that NPY and noradrenaline cooperate in regulating pulpal blood flow.

Occurrence and distribution of neuropeptide-Y-immunoreactive nerves in the respiratory tract and middle ear

Nerve fibres displaying neuropeptide-Y (NPY) immunoreactivity are abundantly distributed in the respiratory tract of cats, guinea-pigs, rats and mice. Fine beaded NPY fibres were seen in whole-mount spreads of the middle-ear mucosa. In the nasal mucosa and in the wall of the Eustachian tube NPY fibres were numerous around arteries and arterioles but sparse in the vicinity of veins; single fibres were found close to the acini of seromucous glands. In the tracheobronchial wall NPY fibres occurred in the proximity of blood vessels, in the subepithelial layer and in the smooth muscle. Surgical and chemical (6-hydroxydopamine treatment) sympathectomy resulted in disappearance of adrenergic and NPY-containing nerve fibres in the nasal mucosa. Sequential staining with antibodies against dopamine-beta-hydroxylase (DBH) and NPY revealed that DBH and NPY occur in the same perivascular nerve fibres in the nasal mucosa. The distribution of NPY fibres in the respiratory tract suggests multiple functions of NPY, such as regulation of local blood flow, glandular secretion and smooth muscle activity.

Putative dopamine-containing cells in the retina of seven species demonstrated by tyrosine hydroxylase immunocytochemistry

Immunocytochemistry with antibodies to catecholamine synthesizing enzymes has revealed cells in the retina of chick, mouse, hamster, rat, guinea-pig, piglet and marmoset which contain tyrosine hydroxylase but not dopamine beta-hydroxylase. These findings suggest that the cells in question produce dopamine but that catecholamine synthesis does not proceed further to noradrenaline. Tyrosine hydroxylase-containing amacrine cells, located in the innermost part of the inner nuclear layer, were present in all the species studied. Some species showed atypically located amacrine cells in the inner plexiform or ganglion cell layer. In the rodents, the existence of tyrosine hydroxylase-containing interplexiform cells was suggested by the presence of a few short immunoreactive ascending processes. Three different morphological types of putative dopamine-containing cells were classified according to the level of ramification.

Retrograde transport of dopamine beta-hydroxylase antibodies in sympathetic neurons: effects of drugs modifying noradrenergic transmission

Antibodies to dopamine beta-hydroxylase (anti-D beta H) were taken up by noradrenergic nerve terminals in the iris following attachment to D beta H, and were transported back to, and accumulated in, the superior cervical ganglion (SCG). Concurrent, or prior destruction of noradrenergic terminals with 6-hydroxydopamine, injected intraocularly, blocked the retrograde transport of anti-D beta H. However, recovery was rapid, reaching 50% of control values within 1 day. Such transport was characterized by a shorter time period before accumulation could be detected in the SCG and by a slower rate of accumulation. These results suggest that noradrenergic neurons recover their ability to turn over synaptic vesicles by exocytosis and transport these back to the ganglion early during the period of axonal regeneration when the axonal length is shorter than normal. The uptake and transport of anti-D beta H was regulated by alpha-adrenergic agents administered locally in the vicinity of noradrenergic nerve terminals. Thus intraocular injection of phentolamine resulted in an increased accumulation of anti-D beta H in the SCG, while amphetamine and the postsynaptic alpha-receptor antagonist, phenylephrine, decreased accumulation. Clonidine and desipramine, which have a predominant presynaptic action, failed to influence the transport of anti-D beta H. These results suggest that in vivo the uptake of anti-D beta H can be increased more by local postsynaptic reflex actions than by a mechanism depending on the inhibition of presynaptic alpha-receptors.

Neuropeptide Y co-exists and co-operates with noradrenaline in perivascular nerve fibers

Neuropeptide Y (NPY)-immunoreactive nerve fibers were numerous around arteries and few around veins. NPY probably co-exists with noradrenaline in such fibers since chemical or surgical sympathectomy eliminated both NPY and noradrenaline from perivascular nerve fibers and since double staining demonstrated dopamine-beta-hydroxylase, the enzyme that catalyzes the conversion of dopamine to noradrenaline, and NPY in the same perivascular nerve fibers. Studies on isolated blood vessels indicated that NPY is not a particularly potent contractile agent in vitro. NPY greatly enhanced the adrenergically mediate contractile response to electrical stimulation and to application of adrenaline, noradrenaline or histamine, as studied in the isolated rabbit gastro-epiploic and femoral arteries. The potentiating effect of NPY on the response to electrical stimulation is probably not presynaptic since NPY affected neither the spontaneous nor the electrically evoked release of [3H]noradrenaline from perivascular sympathetic nerve fibers.

Neuron specific enolase: a marker for the early development of nerves and endocrine cells in the human lung

Neuron specific enolase (NSE), an isoenzyme of the glycolytic enzyme enolase, has been established by immunocytochemical means as a marker of morphological and functional maturation in central neurons and appears late in development. However, little is known about the presence of NSE in developing peripheral neurons and endocrine cells and its relationship to the development of classical neurotransmitters and peptides. We therefore investigated the appearance of NSE immunoreactivity in nerves and mucosal endocrine cells of the human respiratory tract in foetal, neonatal and adult life. NSE was found to be present in neuroblasts, nerve fibres and endocrine cells from the earliest period of gestation examined (8 weeks), before the appearance of acetylcholinesterase activity (10-12 weeks), dopamine-beta-hydroxylase (20 weeks), vasoactive intestinal polypeptide (20 weeks) or calcitonin (20 weeks). Bombesin-like immunoreactivity was found in a small proportion of mucosal endocrine cells as early as eight weeks in the foetal respiratory tract. These findings indicate that unlike central neurons and their processes, peripheral neurons of the lung contain NSE immunoreactivity well before full maturation and establishment of synaptic contact with end organs.

Neurone-specific enolase and S-100: new markers for delineating the innervation of the respiratory tract in man and other mammals

Lung innervation has been studied in the past by methylene blue staining and silver impregnation and more recently by histochemical methods. These techniques give only a partial picture of the total innervation. We have delineated the innervation of the lung in man and three other mammalian species by immunostaining with antibodies to two new markers of nervous tissue. These markers are neurone-specific enolase (NSE), an enzyme present in nerve cells in both the central and the peripheral nervous systems, and S-100, a protein found in glial cells. Throughout the respiratory tract NSE was localised in ganglion cells and nerve fibres in all species examined, while S-100 was found in the supporting glial cells of ganglia and in Schwann cells of peripheral nerves. The distribution of NSE immunoreactivity in serial sections was compared with that of acetylcholinesterase-containing, noradrenergic, and peptide-containing nerves. In all areas NSE was found to be a specific marker for all three types of nerves. Thus these two antibodies provide an effective histological means of examining both the neuronal and the non-neuronal components of the lung innervation and should be of value in investigating this system in lung disease.

Mapping, quantitative distribution and origin of substance p- and VIP-containing nerves in the uvea of guinea pig eye

VIP- and substance P-like immunoreactivities were found in considerable concentrations (VIP: 17.3 +/- 4.8 pmol/g, mean +/- SEM; substance P:11.1 +/- 1.8 pmol/g) in the uveal portion of the guinea pig eye. Immunocytochemistry localised these two regulatory peptides to nerve fibres found principally in a plexus in the iris (substance P) and in an extensive network surrounding the blood vessels of the choroid (VIP). A remarkable anatomical demarcation of the two types of peptide-containing nerves was established by the staining of substance P-containing nerves, which stops at the level of the ciliary body. This uveal area is known to be involved in the ocular responses to nociceptive stimuli. At the ultrastructural level, immunoreactivity for both peptides was localised to distinct subpopulations of p-type nerves, distinguishable by the size of their large dense-cored vesicles. Those immunoreactive for VIP were significantly larger (p less than 0.0005) than those immunoreactive for substance P (95 +/- 7 nm and 82 +/- 9 nm respectively; mean +/- SD). Interruption of the trigeminal pathway produced a remarkable decrease of substance P immunoreactivity in the anterior portion of the uvea (9.1 +/- 1.5 pmol/g, mean +/- SEM, control; 5.3 +/- 1.3 pmol/g, denervated), but not of VIP immunoreactivity in the choroid. Following colchicine treatment, VIP-immunoreactive neuronal cell bodies were localised in the choroid. The separate anatomical localisations and distributions of the two uveal peptides appear to be related to their different origins and functional roles in the response of the eye to noxious stimuli.

Immunogold staining procedure for the localisation of regulatory peptides

The use of protein A- and IgG-conjugated colloidal gold staining methods for the immuno-localisation of peptide hormones and neurotransmitters at light- and electron microscope level are described and discussed. Bright-field and dark-ground illumination modes have been used to visualise the gold-labelled antigenic sites at the light microscope level. Immunogold staining procedures at the ultrastructural level using region-specific antisera have been adopted to localise specific molecular forms of peptides including gastrin (G17 and G34), glucagon and pro-glucagon, insulin and pro-insulin, in normal tissue and in tumours of the gastroenteropancreatic system. Similar methods have been used to demonstrate the heterogeneity of p-type nerves in the enteric nervous system. Vasoactive intestinal polypeptide (VIP) has been localised to granular sites (mean +/- S.D. granule diameter = 98 +/- 19 nm) in nerve terminals of the enteric plexuses and in tumour cells of diarrhoeogenic VIP-producing neoplasias (mean +/- S.D. granule diameter = 126 +/- 37 nm) using immunogold procedures applied to ultraviolet-cured ultrathin sections. Co-localisation of amines and peptides in carotid body type I cells and in chromaffin cells of normal adrenal medulla and phaeochromocytomas has also been demonstrated. Advantages of the immunogold procedures over alternative immunocytochemical techniques are discussed.

Effect of nerve activity on transport of nerve growth factor and dopamine beta-hydroxylase antibodies in sympathetic neurones

The effect of nerve activity on the uptake and retrograde transport of nerve growth factor (NGF) and dopamine beta-hydroxylase (DBH) antibodies was studied by injecting 125I-labelled NGF and anti-DBH into the anterior eye chamber of guinea-pigs. Decentralization of the ipsilateral superior cervical ganglion (SCG) had no significant effect on the retrograde transport of either NGF or anti-DBH. Phenoxybenzamine produced a 50% increase in anti-DBH but not NGF accumulation and this effect was prevented by prior decentralization. This demonstrates that NGF is taken up independently of the retrieval of synaptic vesicle components.

Phentolamine increases neuronal binding and retrograde transport of dopamine beta-hydroxylase antibodies

When 125I-labelled antibodies against dopamine beta-hydroxylase (DBH) were injected into the anterior eye chamber of guinea-pigs they bound to sympathetic nerve terminals, were internalized into the axons and retrogradely transported to the ipsilateral superior cervical ganglion (SCG). This process was demonstrated to depend on specific binding sites since neutralized antibodies were not taken up and transported. The alpha-receptor antagonist phentolamine caused a 2.5-fold increase in binding in the iris and a 2.1-fold increase in accumulation of [125I]anti-DBH in the SCG. The results demonstrate that retrograde axonal transport of synaptic vesicle components is coupled to their turnover in nerve terminals.