Immunohistochemical study on Met-enkephalin-Arg-Gly-Leu-like immunoreactive nerve fibers in the rat adrenal medulla

Generating diversity: Mechanisms regulating the differentiation of autonomic neuron phenotypes

Sympathetic and parasympathetic postganglionic neurons innervate a wide range of target tissues. The subpopulation of neurons innervating each target tissue can express unique combinations of neurotransmitters, neuropeptides, ion channels and receptors, which together comprise the chemical phenotype of the neurons. The target-specific chemical phenotype shown by autonomic postganglionic neurons arises during development. In this review, we examine the different mechanisms that generate such a diversity of neuronal phenotypes from the pool of apparently homogenous neural crest progenitor cells that form the sympathetic ganglia. There is evidence that the final chemical phenotype of autonomic postganglionic neurons is generated by both signals at the level of the cell body that trigger cell-autonomous programs, as well as signals from the target tissues they innervate.

Chemical coding of sympathetic neurons controlling the tarsal muscle of the rat

Sympathetic axons in the upper eyelid and in tissues in the superior retro-orbital space were examined for NPY immunoreactivity. Sympathetic nerve terminals containing co-localised NPY were associated with blood vessels, the conjunctiva and the Meibomian glands. The acini of the Harderian gland completely lacked sympathetic innervation. Sympathetic axons lacking NPY were only found in the tarsal muscle. In addition, a minority of terminals, located in the more proximal part of the tarsal muscle, contained weak immunoreactivity to NPY. Injections of the retrograde tracer, Fast Blue, into the eyelid or retro-orbital space labelled postganglionic somata in the superior cervical ganglion. While many retrogradely labelled somata were immunoreactive for NPY, around half lacked NPY immunoreactivity and so are likely to project to the tarsal muscle. Most of the retrogradely labelled postganglionic somata lacking NPY were surrounded by terminals immunoreactive for met-enkephalin, leu-enkephalin and met-enkephalin arg-gly-leu which were all found to be present in the same nerve terminals. Sectioning the cervico-sympathetic trunk eliminated all enkephalin-immunoreactive pericellular baskets. Many enkephalin-immunoreactive pericellular terminals contained co-localised VAChT, calretinin and calbindin immunoreactivity, but completely lacked nitric oxide synthase immunoreactivity. A second population of nerve terminals that were immunoreactive for nitric oxide synthase also surrounded tarsal muscle-projecting neurons, but these terminals lacked immunoreactivity to enkephalin. Thus, postganglionic neurons projecting to the tarsal muscle are of at least two chemical phenotypes (with or without NPY) and they receive convergent input from at least two populations of preganglionic neurons with distinctive chemical phenotypes.

Preganglionic sympathetic neurones, innervating the guinea pig adrenal medulla, immunohistochemically contain choline acetyltransferase and also leu-enkephalin

Applying retrograde neuronal tracing combined with double labelling immunofluorescence, preganglionic nerve cell bodies in the intermediate grey matter of the guinea pig thoracic spinal cord, projecting to the adrenal gland, co-exhibited immunolabelling for choline-acetyltransferase (ChAT) and sometimes, also for leu-enkephalin. Likewise, ChAT-immunoreactive nerve fibres, forming a dense meshwork in the adrenal medulla, partly contained immunostaining also for leu-enkephalin. Some of the intramedullary nerve cell bodies were ChAT-positive but were non-reactive for leu-enkephalin. The findings provide evidence for an extrinsic (preganglionic) and an intrinsic (postganglionic) cholinergic nerve system in the guinea pig adrenal medulla, the preganglionic system utilising leu-enkephalin as co-mediator.

[Met]enkephalin-Arg6-Gly7-Leu8-immunoreactive nerves in guinea-pig and rat lungs: distribution, origin, and co-existence with vasoactive intestinal polypeptide immunoreactivity

[Met]Enkephalin-Arg6-Gly7-Leu8 is an endogenous opioid peptide, first isolated from the bovine adrenal medulla. Because this octapeptide is specifically contained in the amino acid sequence of preproenkephalin A but not in other opioid precursors like preproopiomelanocortin or preproenkephalin B, [Met]enkephalin-Arg6-Gly7-Leu8 has been regarded as a specific marker for preproenkephalin A and its derivatives. In this study, we examined the occurrence and origin of [Met]enkephalin-Arg6-Gly7-Leu8-immunoreactive nerves in the guinea-pig and rat lung by immunohistochemical techniques, using a specific antiserum against this peptide. In addition, we investigated the possible co-existence of [Met]enkephalin-Arg6-Gly7-Leu8 and vasoactive intestinal peptide immunoreactivity in neuronal elements of the respiratory tract. In both species, [Met]enkephalin-Arg6-Gly7-Leu8 immunoreactivity was localized in nerve fibers chiefly distributed to the trachea and major bronchi, where they were prevalent in smooth muscle bundles, in the lamina propria, around airway glands, and in the walls of pulmonary vessels, but were absent in airway epithelium. Slight differences in the distribution pattern of immunoreactive nerve fibers were noted between the two species: immunoreactive nerve fibers in the smooth muscle bundles were much more abundant in guinea-pigs than in rats, while those in the mucous glands were richer in rats than in guinea-pigs. Neither chemical sympathectomy by 6-hydroxydopamine, nor chemical sensory denervation by capsaicin, changed the density or distribution of [Met]enkephalin-Arg6-Gly7-Leu8-immunoreactive nerve fibers in the airway, suggesting an intrinsic source for these nerve fibers. Colchicine injection into the tracheal wall, to promote the accumulation of neuropeptides in nerve cell bodies, led to the visualization of [Met]enkephalin-Arg6-Gly7-Leu8 immunoreactivity in some neuronal cell bodies within airway ganglia. Immunostaining for [Met]enkephalin-Arg6-Gly7-Leu8 and for vasoactive intestinal polypeptide on serial adjacent sections of airway ganglia obtained from colchicine-treated tracheae, demonstrated the co-existence of these immunoreactivities in a population of nerve cell bodies in these ganglia. The immunohistochemical localization of immunoreactive [Met]enkephalin-Arg6-Gly7-Leu8 in nerve elements in guinea-pig and rat lungs provides a morphological basis for the possibility that preproenkephalin A-related opioid peptides may have a neuromodulatory role in mammalian airways and pulmonary vessels.

Immunocytochemical localization of neuropeptides in the adrenal medulla

The distribution of neuropeptides exhibits pronounced interspecies heterogeneity. Neuropeptides may function as hormones secreted from chromaffin cells or as neurotransmitters/neuromodulators released from nerve terminals. However, other possible functions such as trophic or intracellular effects should also be considered. Thus, to understand the role of neuropeptides, it is important to explore their localization in different species. The distribution of enkephalins, neurotensin, neuropeptide Y, calcitonin gene-related peptide, and galanin in the adrenal medulla of rat, cat, hamster, and mouse is presented in detail.

Differential distribution of neuropeptides and serotonin in pig adrenal glands

A differential distribution of vasoactive neuropeptides and serotonin in chromaffin cells and nerve fibers within the adrenal glands of the pig (Sus scrofa) was found using immunohistochemical methods. Met- and leu-enkephalins, present at high levels in the medulla (measured by radioimmunoassay), occurred in adrenaline storing cells, some of which contained calcitonin gene-related peptide. Islets of chromaffin cells beneath the capsule also contained enkephalins and calcitonin gene-related peptide. Nerve fibers with enkephalin-like immunoreactivity were sparse, but many varicose fibers in the inner cortex and medulla showed calcitonin gene-related peptide immunofluorescence in a pattern similar to vasoactive intestinal polypeptide. Neuropeptide Y was mainly associated with perivascular fibers and neither neuropeptide Y nor vasoactive intestinal polypeptide immunoreactive chromaffin cells were detected. In contrast to the neuropeptides, most serotonin-like immunoreactivity coincided with noradrenaline histofluorescence. It is concluded that the distribution of nerve fibers with calcitonin gene-related peptide and vasoactive intestinal polypeptide would allow interactions between chromaffin and inner cortical cells. Stimuli activating noradrenaline chromaffin cells could release serotonin while stimulation of adrenaline storage cells would release enkephalin and, to a lesser extent, calcitonin gene-related peptide. Met-enkephalin, which occurs 3 4:1 over leu-enkephalin, is the most likely of the co-released peptides to reach distant receptors via the venous outflow.

Immunohistochemical localization of oxytocin and vasopressin in the adrenal glands of rat, cow, hamster and guinea pig

The distribution of oxytocin and vasopressin in the adrenals of rat, cow, hamster and guinea pig has been studied by use of immunohistochemical techniques. In all the species studied the adrenal cortex contained both peptides; the staining in the zona glomerulosa being more intense than that in zona fasciculata or zona reticularis. The medulla, however, showed considerable species variation. In the cow, both peptides appear to be present in the adrenergic and noradrenergic cells, though staining was particularly prominent in cortical islands interspersed within the medullary tissue. In the rat, groups of medullary cells positive for both peptides were found, though it was not possible to associate these groups with particular chromaffin cell types. In the hamster oxytocin was present only in adrenaline-containing cells, whereas vasopressin was present in all medullary cells. The guinea pig medulla, which contains only adrenaline-secreting cells, was positive for both peptides. The possibilities that vasopressin and oxytocin have an autocrine or paracrine role in functioning of the adrenal gland is discussed.

Calcitonin gene-related peptide (CGRP)-like immunoreactivity in scattered chromaffin cells and nerve fibers in the adrenal gland of rats

The present immunohistochemical study reveals that a small number of chromaffin cells in the rat adrenal medulla exhibit CGRP-like immunoreactivity. All CGRP-immunoreactive cells were found to be chromaffin cells without noradrenaline fluorescence; from combined immunohistochemistry and fluorescence histochemistry we suggest that these are adrenaline cells. In addition, all CGRP-immunoreactive cells simultaneously exhibited NPY-like immunoreactivity. CGRP-chromaffin cells were characterized by abundant chromaffin granules with round cores in which the immunoreactive material was densely localized. These findings suggest the co-existence of CGRP, NPY and adrenaline within the chromaffin granules in a substantial number of chromaffin cells. Thicker and thinner nerve bundles, which included CGRP-immunoreactive nerve fibers, with or without varicosities, penetrated the adrenal capsule. Most of them passed through the cortex and entered the medulla directly, whereas others were distributed in subcapsular regions and among the cortical cells of the zona glomerulosa. Here the CGRP-fibers were in close contact with cortical cells. A few of the fibers supplying the cortex extended further into the medulla. The CGRP-immunoreactive fibers in the medulla were traced among and within small clusters of chromaffin cells and around ganglion cells. The CGRP-fibers were directly apposed to both CGRP-positive and negative chromaffin cells, as well as to ganglion cells. Immunoreactive fibers, which could not be found close to blood vessels, were characterized by the presence of numerous small clear vesicles mixed with a few large granular vesicles. The immunoreactive material was localized in the large granular vesicles and also in the axoplasm.(ABSTRACT TRUNCATED AT 250 WORDS)

An immuno-electron-microscopic study of the localization of VIP-like immunoreactivity in the adrenal gland of the rat

VIP-like immunoreactivity was revealed in a few chromaffin cells, medullary ganglion cells and a plexus of varicose nerve fibers in the superficial cortex and single varicose fibers in the juxtamedullary cortex and the medulla of the rat adrenal gland. VIP-like immunoreactive chromaffin cells were polygonal in shape without any distinct cytoplasmic processes and they appeared solitarily. Their cytoplasm contained abundant granular vesicles having a round core and the immunoreactive material was localized to the granular core. VIP-immunoreactive ganglion cells were multipolar and had large intracytoplasmic vacuoles. The immunoreactive material was localized not only in a few granular vesicles but also diffusely throughout the axoplasm. VIP-immunoreactive varicose nerve fibers in the superficial cortex were characterized by abundant small clear vesicles and some large granular vesicles, while those in the juxtamedullary cortex and medulla and the ganglionic processes were characterized by abundant large clear vesicles, as well as the same vesicular elements as contained in the nerves in the superficial cortex. The immunoreactive material was localized on the granular cores and diffusely in the axoplasm in both nerves. Based on the similarity and difference in the composition of the vesicles contained in individual nerves, it is likely that the VIP-immunoreactive nerve fibers in the medulla and the juxtamedullary cortex are derived from the medullary VIP-ganglion cells, while those in the superficial cortex are of extrinsic origin. The immunoreactive nerve fibers in both the cortex and the medulla were often in direct contact with cortical cells and chromaffin cells, where no membrane specializations were formed.(ABSTRACT TRUNCATED AT 250 WORDS)

Localization of Met-enkephalin-Arg6-Gly7-Leu8 immunoreactivity in rat duodenum

The distribution of Met-enkephalin-Arg6-Gly7-Leu8 (Met-ENK-Arg6-Gly7-Leu8) in the rat duodenum was determined using specific antibodies against Met-ENK-Arg6-Gly7-Leu8 and the immunofluorescence microscope technique. Met-ENK-Arg6-Gly7-Leu8 immunoreactive perikarya have been detected in the myenteric plexus. These neuronal cell bodies were large in diameter and round in shape. Met-ENK-Arg6-Gly7-Leu8 immunostained nerve fibres were noted in both the circular muscle layer and, more abundantly, in interconnecting myenteric plexus nerve fibre bundles. These findings might indicate that Met-ENK-Arg6-Gly7-Leu8 has important physiological roles as neurotransmitter and/or neuromodulator in the human and mammalian gastrointestinal tract.

Modulation of bovine adrenal gland secretion by etorphine and diprenorphine

Retrograde perfusion was used to investigate the effect of an opiate agonist and an opiate antagonist on the release of catecholamines and [Met5]-enkephalin immunoreactive material (ME-IRM) from bovine adrenal glands. Etorphine (5 X 10(-7) M) inhibited the spontaneous outflow of ME-IRM by approximately 10 percent but had no significant effect on the spontaneous catecholamine release. Acetylcholine (ACh, 5 X 10(-5) M) or 1,1-dimethyl-4-phenylpiperazinium (DMPP, 5 X 10(-5) M) stimulated release of ME-IRM and catecholamines was significantly decreased by the addition of etorphine. Diprenorphine (5 X 10(-7) M) had no significant effect on the spontaneous outflow of either ME-IRM or catecholamines. Diprenorphine reversed the inhibition of the DMPP-stimulated release caused by etorphine. After submaximal stimulation of the gland with DMPP (1 X 10(-5) M), a further stimulation of release of ME-IRM and catecholamines was observed after the addition of diprenorphine alone, i.e., in the absence of etorphine. These results provide further evidence supporting the contention that opiates modulate the secretion of catecholamines and ME-IRM from the adrenal gland.

Neuropeptide tyrosine (NPY)-like immunoreactivity in adrenal chromaffin cells and intraadrenal nerve fibers of rats

The present peroxidase-antiperoxidase immunohistochemical study demonstrated that approximately 50% of the total chromaffin cells of the rat adrenal medulla exhibited NPY-like immunoreactivity. The immunoreactive material was localized in the core of the chromaffin granules as well as diffusely in the cytoplasm. By combination of immunohistochemistry with noradrenaline-fluorescence microscopy, all NPY-immunoreactive chromaffin cells are nonfluorescent, indicating that all NPY-chromaffin cells co-store adrenaline. A comparison of two consecutive sections, each of which was processed for the immunostaining with anti-NPY and anti-Met-Enk-Arg-Gly-Leu antisera, respectively, indicated that NPY and preproenkephalin A and its derivatives coexist in approximately one-fifth of the total NPY-immunoreactive cells. In addition to the NPY-immunoreactive cells, a plexus of NPY-immunoreactive nerve fibers with varicosities was found in the subcapsular regions of the adrenal gland. The nerve fibers were often associated with small blood vessels and extended into the zona glomerulosa. Single NPY-immunoreactive fibers were sparsely distributed in the deeper regions of the cortex and in the medulla. Ganglion cells in the adrenal gland were not seen exhibiting intensely positive NPY-like immunoreactivity. The NPY-immunoreactive nerve fibers contained abundant small clear vesicles mixed with a few small and large granular vesicles. The immunoreactive material appeared on the granular cores as well as in the axoplasm. The NPY fibers were closely apposed to smooth muscle cells and pericytes of small blood vessels in the cortex.(ABSTRACT TRUNCATED AT 250 WORDS)

Localisation of oxytocin, vasopressin and parts of precursors in the human neonatal adrenal

Being a possible alternative source for the production of vasopressin (AVP) and oxytocin (OXT), a study was undertaken of the fetal adrenal. The concentrations of these peptides within the fetal adrenal turned out to be low, viz., approx. 1 pg/mg in the rat and within the pg/g range in the human. Immunocytochemistry was performed either on conventional autopsy material kept till 12 years in paraffin blocks, or on more recently obtained formalin or glutaraldehyde-paraformaldehyde fixed material. In both types of material staining was good. In order to localize AVP cells, anti-AVP, an antibody against its associated neurophysin (anti-NSN) or an antibody raised against the c-terminal glycopeptide part of the AVP precursor (anti-GP) was used. OXT cells were localized by means of anti-OXT or an auto-antibody of a multiple sclerosis patient (auto-MS) probably recognizing OXT-neurophysin. The antibodies were characterized on human and rat brain material. In the external zone of the definitive cortex, apart from parenchyma cells, anti-AVP, anti-NSN and anti-GP stained fibre-like structures running in the connective tissue septa and around parenchyma cells and the cytoplasma of these cells. Anti-OXT and auto-MS stained droplets in the cytoplasm of the fetal zone cells. Similar distinct staining patterns for AVP and OXT cells were obtained in human anencephalics. These observations show that the peptides are not derived from the fetal brain, but are rather produced in the fetal adrenal cortex.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence for the coexistence of acetylcholine and enkephalin in the sympathetic preganglionic neurons of rats

The localization of the cholinergic neurons in the lower thoracic segments of the spinal cord of rats was examined by a monoclonal antibody against choline acetyltransferase (ChAT). The ChAT-immunoreactive neurons were located in the intermediate as well as anterior gray matters. In the intermediate gray the highest incidence of the immunoreactive neurons was in the nucleus intermediolateralis, followed by the nucleus intercalatus pars paraependymalis and a few immunoreactive neurons were seen in the nucleus intercalatus proprius. In the sequential immunostaining of one and the same section of the spinal cord pretreated with colchicine using the ChAT antibody and a polyclonal antibody against methionine-enkephalin-argynine-glycine-leucine (Met-Enk-Arg-Gly-Leu), substantial numbers of neurons were immunostained simultaneously by the two antibodies in the intermediate gray matter. The present finding gives strong evidence for the coexistence of acetylcholine and enkephalins in, at least, some of the preganglionic neurons projecting their axons to the periphery.

Substance P-like immunoreactivity in adrenal chromaffin cells and intra-adrenal nerve fibers of rats

The present peroxidase-antiperoxidase immunohistochemical study demonstrated a relatively small number of cells with substance P(SP)-like immunoreactivity in the adrenal medulla of rats. These cells were found alone or in small groups, were polygonal in shape and lacked long cytoplasmic processes. At immunoelectron microscopy, the immunoreactive cells were characterized by abundant granular vesicles, and the immunoreactive material was confined to the round core of the vesicles. Thus, it is suggested that SP co-exists with catecholamines in a population of chromaffin cells of the rat adrenal medulla. In addition a few SP-immunoreactive nerve fibers with varicosities were found in the adrenal medulla of rats. They extended between small clusters of chromaffin cells and had their dot-like terminals around and within the cell clusters. The SP-immunoreactive nerve fibers were characterized by the presence of abundant small clear vesicles mixed with a few large granular vesicles; the immunoreactivity appeared in the latter, but was also perfused throughout the entire axoplasm. The nerve fibers formed synapses on nonimmunoreactive chromaffin cells. Judging from the presence of bundles of SP-immunoreactive nerve fibers penetrating the adrenal capsule and cortex as well as the absence of SP-immunoreactive ganglion cells in the medulla, the intramedullary SP-immunoreactive nerve fibers seem to be extrinsic in origin.