Serotonergic innervation of the foot of the pond snail Lymnaea stagnalis (L.)

The aminergic innervation of the foot of Lymnaea stagnalis was investigated using electron microscopy, immunocytochemistry, and HPLC. The foot was found to contain large amounts of serotonin and dopamine, though at lower concentrations than are found in nervous tissue. Serotonin containing tissue was concentrated in the ventral surface of the foot, under ciliated areas of the epidermis where it occurred in varicosities, with fine tracts joining these varicosities. Varicosities also occurred in deeper tissues, probably adjacent to mucus cells. Positive fluorescence for serotonin in axons was found in nerves innervating the foot, but few neuronal cell bodies containing serotonin were detected, indicating that most of the innervation was coming from the central ganglia. Axon varicosities were found using TEM on ciliated cells, mucus cells, and muscle cells as well as interaxonal junctions (possibly non-synaptic) within nerves. The neuronal varicosities contacting the ciliated cells and mucus cells contained mostly dense-cored vesicles of between 60 and 100 nm in diameter. Smaller, lucent vesicles also occurred in these terminals. The origin and significance of this innervation is discussed. It is suggested that both serotonin and dopamine may play a large role in controlling ciliary gliding by the foot.     

Serotonin-immunoreactive axons in the cell column of sympathetic preganglionic neurons in the spinal cord of the filefish Stephanolepis cirrhifer

Serotonin-immunoreactive axonal components were observed in the central autonomic nucleus (CAN), a cell column of sympathetic preganglionic neurons in the rostral spinal cord of the filefish Stephanolepis cirrhifer. Serotonin-positive axonal varicosities were seen around neuronal perikarya through the whole rostrocaudal extent of the CAN, although their distribution pattern in the rostral CAN was different from that in the caudal CAN. Electron microscopically, serotonin-positive axonal varicosities were found to make axodendritic and axosomatic synapses on CAN neurons. Many serotonin-positive neuronal cell bodies were seen in the raphe nuclei in the lower brainstem, whereas only a few were found in the spinal cord. Thus most of serotoninergic axons within the CAN were considered to originate from the raphe nuclei in the lower brainstem.     

An ultrastructural analysis of the developing enteric nervous system of the guinea-pig small intestine

Summary The developing enteric nervous system of the guinea-pig has been analysed ultrastructurally. In addition, electron microscope autoradiography, following incubation with tritiated 5-hydroxytryptamine ([³H]5-HT) or tritiated norepinephrine ([³H]NE) was used to locate the developing axons of enteric serotoninergic and adrenergic neurons respectively. Observations have been correlated with previous studies of the development of the various types of enteric neuron and the onset of intestinal neuromuscular function. Prior to 25 days of gestation no neurons can be recognized morphologically. Neurons first appear at 25 days' gestation, together with a primitive neuropil in neural islands within the outer gut mesenchyme. Ganglion cell precursors are primitive at first and resemble the cells in the surrounding mesenchyme. Growth cones are abundant but there are no terminal varicosities or synapses. The circular muscle also begins to form at this time. At 32 days' gestation the longitudinal layer of smooth muscle can be discerned and, within the myenteric plexus, terminal axonal varicosities appear containing small (about 50 nm in diameter) electron-lucent synaptic vesicles. The submucosal plexus appears to be derived from neurons and neurites that reach it from the earlier-developing myenteric plexus. The submucosal plexus can be recognized at 38 days of gestation but is not well developed until day 42. Synapses on ganglion cell somata first appear in the myenteric plexus on gestational day 38 and are numerous on day 42 when the first axo-dendritic synapses can be seen. Between days 42 and 48 the developing neural tissue and growing smooth muscle cells interdigitate but after day 48, the plexus becomes ensheathed by supporting cells and connective tissue and this interdigitation is lost. Prior to day 48 most varicosities contain small electron-lucent synaptic vesicles; however, after this time a variety of terminals appears. Between days 48 and 53 of gestation evidence of degenerating neuronal processes is common, indicating that cell death may occur. Electron microscopic autoradiography with [³H]5-HT reveals labelling of axons in the neuropil of the myenteric plexus at day 32 of gestation. Some primitive appearing cell bodies, however, are also labelled and these cells seem to be entering the myenteric plexus from the surrounding mesenchyme. After 42 days of gestation [³H]5-HT labels only axons of both nerve plexuses. Often, labelled terminals are apposed to ganglion cells or dendrites. In contrast, significant labelling by [³H]NE is not found until gestational day 48. Axons are labelled by [³H]NE and these tend to be located at the interface between the myenteric plexus and the surrounding connective tissue.     

Three-dimensional visualization of the intraganglionic structures of the rat myenteric plexus: scanning electron microscopy with the connective tissue digestion method

The rat myenteric plexus was chemically microdissected and the internal structures of the ganglia were demonstrated under a scanning electron microscope. The present preparation offers a view of the three-dimensional features of ganglion cells and permits their surface structures and the size and pattern of varicosities to be observed. Numerous finger-like processes were observed on the cell bodies of the studded neurons in close relationship with the varicose axons. The intramuscular branches of the plexus were also microdissected and their running pattern was observed.     

Noradrenergic and non-noradrenergic nerves containing small granular vesicles in Auerbach's plexus of the guinea-pig: evidence against the presence of noradrenergic synapses

The appearance and distribution of varicosities containing small granular vesicles in Auerbach's plexus of the guinea-pig ileum, distal colon and rectum has been studied with the electron-microscope. Two types of varicosity were recognised. The first type was located predominantly at the surface of the plexus and did not form synapses on intrinsic neurons. This type became labelled with 5-hydroxydopamine, a specific marker for noradrenergic axons, and was destroyed by 6-hydroxydopamine and extrinsic denervation, procedures which lead to degeneration of noradrenergic nerves in the gut. The second type formed axodendritic and axosomatic synapses on intrinsic neurons and the morphology of its synaptic vesicles differed subtly from that of the first type. The second type was unaffected by 5-hydroxydopamine, 6-hydroxydopamine, or extrinsic denervation. It is concluded that the two types of small granular vesicle-containing varicosities belong to different neurons and that the first type is noradrenergic. Noradrenergic varicosities do not, therefore, form synapses in Auerbach's plexus. This conclusion is in accord with the electrophysiological findings. The second type of small granular vesicle-containing varicosity is not noradrenergic although it was formerly thought to be so. It is intrinsic to the gut and is resistant to the serotoninergic neurotoxin, 5,6-dihydroxytryptamine.     

Anatomy of primary afferents and projection neurones in the rat spinal dorsal horn with particular emphasis on substance P and the neurokinin 1 receptor

The dorsal horn of the spinal cord plays an important role in transmitting information from nociceptive primary afferent neurones to the brain; however, our knowledge of its neuronal and synaptic organisation is still limited. Nociceptive afferents terminate mainly in laminae I and II and some of these contain substance P. Many projection neurones are located in lamina I and these send axons to various parts of the brain, including the caudal ventrolateral medulla (CVLM), parabrachial area, periaqueductal grey matter and thalamus. The neurokinin 1 (NK1) receptor on which substance P acts is expressed by certain neurones in the dorsal horn, including approximately 80 % of lamina I projection neurones. There is also a population of large NK1 receptor-immunoreactive neurones with cell bodies in laminae III and IV which project to the CVLM and parabrachial area. It has been shown that the lamina III/IV NK1 receptor-immunoreactive projection neurones are densely and selectively innervated by substance P-containing primary afferent neurones, and there is evidence that these afferents also target lamina I projection neurones with the receptor. Both types of neurone are innervated by descending serotoninergic axons from the medullary raphe nuclei. The lamina III/IV neurones also receive numerous synapses from axons of local inhibitory interneurones which contain GABA and neuropeptide Y, and again this input shows some specificity since post-synaptic dorsal column neurones which also have cell bodies in laminae III and IV receive few contacts from neuropeptide Y-containing axons. These observations indicate that there are specific patterns of synaptic connectivity within the spinal dorsal horn.     

Distribution of enteric nerve cell bodies and axons showing immunoreactivity for vasoactive intestinal polypeptide in the guinea-pig intestine

Immunoreactivity for vasoactive intestinal polypeptide has been localized in neurons in the guinea-pig ileum, colon and stomach. In the ileum, 2.5% of the nerve cell bodies of the myenteric plexus and 45% of those of the submucous plexus showed vasoactive intestinal polypeptide-like immunoreactivity. Varicose axons containing vasoactive intestinal polypeptide ramified amongst the nerve cell bodies of both plexuses and in some cases formed rings of varicosities around non-reactive nerve cells. Axons were traced from the myenteric plexus to the circular muscle and deep muscular plexus. There were numerous positive axons running in fine strands within the circular muscle, parallel to the muscle bundles. Axons containing vasoactive intestinal polypeptide were associated with mucosal blood vessels, but few supplied the vascular network of the submucosa; some immunoreactive axons also contributed to the periglandular plexus of the mucosa. There were no changes in the distribution of axons in the ileum after extrinsic denervation.The results are discussed in relation to the possible functional roles of neurons that contain vasoactive intestinal polypeptide in the intestine: the distribution of such nerve cells in the myenteric plexus and of axons in the circular muscle and sphincters is consistent with this polypeptide being a transmitter of enteric inhibitory neurons; it is also possible that vasoactive intestinal polypeptide is the enteric vasodilator transmitter.     

PRQFVamide,a novel pentapeptide identified from the CNS and gut of Aplysia

We have purified a novel pentapeptide from the Aplysia nervous system using bioassay on gut contractions. The structure of the peptide is Pro-Arg-Gln-Phe-Val-amide (PRQFVa). The precursor for PRQFVa was found to code for 33 copies of PRQFVamide and four related pentapeptides. Peaks corresponding to the predicted masses of all five pentapeptides were detected in Aplysia neurons by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Northern analysis revealed that expression of the precursor is abundant in the abdominal ganglion, much less in the pedal and cerebral ganglia, and rarely seen in the buccal and pleural ganglia. PRQFVa-positive neurons, mapped by immunohistochemistry and in situ hybridization, were present in all the central ganglia. PRQFVa immunopositive processes were observed in the gut, particularly in association with the vasculature. Some arteries and other highly vascularized tissues, such as the gill and the kidney, also contain numerous PRQFVa immunopositive processes. Application of synthetic PRQFVa suppresses not only contractions of the gut but also contractions of vasculature. PRQFVa is expressed in some of the neurons within the feeding circuitry and application of synthetic PRQFVa was found to decrease the excitability of some (B4/5 and B31/32) but not all (B8) neurons of the buccal feeding circuit. Our findings suggest that PRQFVa may act as a modulator within the feeding system as well as in other systems of Aplysia.     

Ultrastructural identification of noradrenergic axons and their distribution within the enteric plexuses of the guinea-pig small intestine

Summary Noradrenergic axons in the enteric plexuses of the guinea-pig ileum have been identified at the ultrastructural level using three techniques: the chromaffin reaction, localization of dopamine--hydroxylase (DBH) with horseradish peroxidase-conjugated antibody, andin vivo andin vitro loading with 5-hydroxydopamine (5-OHDA).In the myenteric (Auerbach's) plexus from normal ileum all of these methods produced electron-dense deposits in a distinctive population of axonal varicosities that contained many flattened vesicles (usually more than 30% of the total number of vesicles), as well as oval or irregularly shaped vesicles. When noradrenergic axons to the small intestine had degenerated after surgical denervation, no profiles containing vesicles with electron-dense deposits were observed with the chromaffin reaction, DBH localization or loading with 5-OHDA. Pretreatment with 6-hydroxydopamine (6-OHDA) substantially reduced the number of noradrenergic axons identified by these three techniques. Axons with many flattened vesicles of similar dimensions but without dense cores were found in myenteric plexus from conventionally fixed intestine. These axons had the same distribution within the ganglia as cytochemically labelled noradrenergic terminals and disappeared after extrinsic denervation.In the normal submucous (Meissner's) plexus, both 5-OHDA loading and the chromaffin reaction produced electron-dense granules in small and large vesicles in some axon terminals. In ganglia labelled by these techniques, reactive terminals contained many small round vesicles and few flattened and large round vesicles as did a population of nonreactive terminals. In axon terminals of submucous plexus labelled with anti-DBH, flattened vesicles were found to be more numerous than with the other treatments. As in the myenteric plexus, all reactive axons disappeared from the submucous plexus after extrinsic denervation. In conventionally processed submucous ganglia, noradrenergic axon profiles could not be distinguished from some non-noradrenergic profiles on the basis of types and proportions of vesicles.In the myenteric plexus noradrenergic axon terminals were seen most often near the edges of ganglia. Noradrenergic varicosities also occurred near nerve cell bodies but were rarely found in internodal strands. In the submucous plexus noradrenergic terminals appeared to be randomly distributed throughout submucous ganglia. No axosomatic synapses formed by noradrenergic axons were found in either plexus, but synapses on nerve processes were occasionally encountered in submucous ganglia.     

Immunohistochemical evidence for the presence of somatostatin,a powerful inhibitory peptide,in some primary sensory neurons

With the indirect immunofluorescence technique somatostatin or somatostatin-like immunoreactivity was found in some neuronal cell bodies in spinal ganglia, in fibers in the substantia gelatinosa of the spinal cord and in nerves in the gut. These findings suggest that a certain population of primary sensory neurons contain somatostatin (or a somatostatin-like peptide), a peptide known to exert an inhibitory action both in the central nervous system and in some endocrine systems.     

Ultrastructure of the nerve plexuses of the mammalian intestine: The enteric glial cells

The ultrastructure of the glial cells in the enteric plexuses of the rat, guinea-pig, rabbit, cat and sheep has been investigated by freeze-fracture and by thin-section electron microscopy. In all the ganglia studied, glial cells outnumber neurons. They are readily identified by their shape, position and ultrastructure (particularly the abundant amount of gliofilaments) but could not be subdivided into separate types. They provide a partial sheath to the ganglion neurons (but large areas of neuronal membrane lie directly beneath the basal lamina and collagen fibrils) and have long laminar processes extending between nerve processes. Most nerve processes are in direct membrane-to-membrane contact with each other; the glial cells only separate groups of them and rarely form a sheath around an individual neurite.The gliofilaments are anchored to conspicuous dense bodies beneath the cell membrane at the surface of ganglia. The possible significance of these systems of gliofilaments (and the high number of intermediate junctions) is discussed in the light of the severe mechanical stresses imposed on the ganglia by the contractile activity of the gut wall.Numerous specialized contacts, of unknown significance, are found between vesicle-containing nerve varicosities and glial cell bodies or glial processes. In freeze-fracture preparations (cat and guinea-pig), a specific pattern of intramembrane particles allows the cell membrane of the enteric glial cells to be readily identified.     

The serotoninergic system of the brain of the viper, Vipera aspis. An immunohistochemical study

Serotoninergic cell bodies and fibers in the brain of the viper, Vipera aspis, were visualized by immunohistochemistry. Immunoreactive cell bodies were observed in the diencephalic hypothalamic periventricular organ and in the dorsal wall of the infundibular recess, in the nuclei raphe superior and inferior of the midbrain and hindbrain, and to a lesser extent in the nuclei reticularis superior, reticularis inferior and reticularis lateralis. In contrast to other reptilian species, serotoninergic cells were also observed in the central gray matter of the midbrain in the neighbourhood of the nucleus of the trochlear nerve. Immunoreactive fibers are widely distributed throughout the brain of the viper. In the olfactory bulb, fibers were observed in the internal plexiform layer and mitral cell layer. The cerebral cortex contains the highest density of fibers in the dorsal region. The distribution of immunoreactive fibers in the dorsal ventricular ridge is extremely heterogeneous, and five subcomponents of this structure can be distinguished. The majority of diencephalic and mesencephalic structures that contain immunoreactive fibers are also primary visual centres: the nuclei geniculatus lateralis pars dorsalis, the n. posterodorsalis and n. opticus tegmenti, and the optic tectum. Serotoninergic fibers in the nuclei of the oculomotor and motor cranial nerves (III, IV, V, VII, X) are disposed in a tightly woven basket around the non-immunoreactive cell bodies of the motoneurons. These findings, together with the available literature, suggest that the serotoninergic system in snakes is comparable to that in lizards, with a massive ascending projection of fibers from the n. raphe superior to mesencephalic and prosencephalic structures, and a descending projection from the n. raphe inferior to the spinal cord.     

Ontogeny of the neuronal intermediate filament protein, peripherin, in the mouse embryo

The expression of peripherin, a type III neuron-specific intermediate filament protein, and the middle neurofilament subunit were studied in the mouse embryo using immunofluorescence staining. The earliest staining for both proteins is seen at embryonic day 9 in the myelencephalon, initially as fiber staining followed by cell body staining in the developing facial and acoustic nuclei. As the embryo develops, there is rostral as well as caudal extension of peripherin and staining is seen in the trigeminal ganglia, nerve fibers and in the enteric nervous system. As the spinal cord forms there is anti-peripherin staining in developing motoneurons of the anterior horns while little cell body staining is seen for the middle neurofilament subunit. Both antibodies stain the developing dorsal root and its entry zone, but peripherin is found in the secondary sensory and commissural fibers while the middle neurofilament subunit is not. While both proteins are found in the neurons of the dorsal root ganglia, their distribution varies. The larger peripheral cells of the ganglia contain both proteins while the smaller more central cells, constituting over 60% of the cells in the ganglia, contain only peripherin. A similar picture is found in the sympathetic ganglia where there are cells which contain peripherin. middle neurofilament subunit or both, but where the majority of the neurons have only peripherin in their cell bodies. Peripherin is not found in the developing retina or in the adrenal medulla. Peripherin is also completely absent from cell bodies in the cerebral and cerebellar cortices. These results indicate that peripherin is found in development only in regions in which it is found in the adult. It can either co-exist with neurofilaments in the same neuron or the two may be independently expressed.     

Retinotectal reorganization in goldfish--IV. Effects of retinal ganglion cells after half tectal ablation

During compression of the entire retinotectal projection into the rostral half of the tectum after ablation of the caudal half there is widespread sprouting of ganglion cell axons, not only those cut during the operation but also those left intact. However, unlike cut axons those left intact sprout without their cell bodies showing chromatolysis or swelling. Chromatolysis and swelling of the cell bodies of cut axons are more prolonged than after optic nerve section and resolve in more central regions of retina first. The cut axons of cell bodies in these regions tend to be the first to form terminal arborizations during the compression process as judged electrophysiologically. However, there is no clear correlation in individual fish between these measures and the state of compression assessed electrophysiologically. Large areas of retina may contain chromatolysed cells even after compression has occurred. Electrophysiological mapping alone may give a misleading picture of the interactions occurring between retinal and tectal cells during reorganization.     

Co-localization of calcitonin gene-related peptide-like immunoreactivity with substance P in cutaneous, vascular and visceral sensory neurons of guinea pigs

Calcitonin gene-related peptide (CGRP) has been immunohistochemically co-localized with substance P (SP) in capsaicin-sensitive, varicose axons supplying the skin, viscera and cardiovascular system of the guinea pig. After treatment with colchicine in vitro, 82% of SP neurons in the dorsal root ganglia contained CGRP-like immunoreactivity while 96% of CGRP neurons were immunoreactive for SP. Both CGRP- and SP-like immunoreactive material are transported peripherally and centrally from dorsal root ganglia. Thus, in tissues such as the gut where there are intrinsic nerves containing SP but lacking CGRP, CGRP-like immunoreactivity is a useful means of specifically labelling axons of most sensory neurons containing SP.     

Long-term changes in the distribution of galanin in dorsal root ganglia after sciatic or spinal nerve transection in rats

The neuropeptide galanin is upregulated in primary afferent and sympathetic neurones and might be involved in the development of sympathetic perineuronal baskets ("rings") following nerve injury. Galanin, calcitonin gene-related peptide and tyrosine hydroxylase have been examined immunohistochemically in dorsal root ganglia and associated roots at times up to one year after transection of either sciatic or L5 spinal nerves in adult rats. Small diameter somata containing calcitonin gene-related peptide (with or without galanin) were reduced in number, whereas galanin (and, at later times, calcitonin gene-related peptide) appeared in medium to large diameter cells after both types of lesion. Galanin also appeared in axons in grey rami and somata in lumbar paravertebral ganglia. Within dorsal root ganglia, galanin-positive axons formed perineuronal rings of two types: (i) smooth coiled axons surrounded small (< 30 microm diameter) somata from which they probably arose; these were rare after 12 weeks, particularly after a spinal nerve lesion; and (ii) varicose terminals encircled medium to large galanin-positive somata; some arose from brightly immunofluorescent somata nearby and took nearly a year to disappear. About 30% of varicose galanin-positive rings had associated calcitonin gene-related peptide-positive terminals (partly colocalized) whereas nearly 45% had associated tyrosine hydroxylase-positive terminals (partly colocalized). Synaptophysin was present in swollen axons and in some varicosities of all types.We conclude that, after peripheral nerve lesions, varicose perineuronal rings around large diameter dorsal root ganglion cells may be formed by axotomized primary afferent neurones (some containing calcitonin gene-related peptide) and sympathetic neurones, both of which contain upregulated galanin. Exocytosis from the varicosities may modify the excitability of mechanosensitive somata. Small galanin-positive somata disappear over several months after both lesions as calcitonin gene-related peptide reappears in medium to large neurones.     

Afferent axons and their relations with neurons in the nucleus lateralis of the cerebellum: A light microscopic study

Summary The axons of Purkinje cells are the sole corticonuclear afferents to the lateral nucleus. The terminal arborizations of these axons consist of many (30–50) varicose branchlets, which issue from a thick, myelinated parent axon. Each terminal plexus fills a conical field which penetrates the lateral nucleus radially encompassing the cell bodies and parts of the dendritic trees of approximately 40 neurons. The fields of neighboring Purkinje axons overlap considerably. The non-cortical axons are simple, usally unbranched varicose fibers of three sizes: (1) thick, with large varicosities, (2) medium sized with smaller varicosities, or (3) fine, delicate threads with beadlike varicosities. These axons cross the dendritic trees of successive neurons as they penetrate into the nucleus in a radial fashion.The configuration of the dendritic trees of neurons in the various parts of the nucleus—the multipolar neurons and the columnar neurons—can be related to the conical shape of the Purkinje axonal plexus. It is suggested that the organization of converging Purkinje cell axonal fields determines the pattern of input to the cells of the lateral nucleus, rather than the topographical arrangement of Purkinje cells in the cortex. The terminal arborizations of Purkinje cell axons adjacent to one another in the lateral nucleus need not necessarily arise from neighboring Purkinje cells in the cerebellar cortex.The relationships between neurons in the central columnar zone and in the swirled zones of the lateral nucleus with the two classes of afferents are discussed. It is suggested that by virtue of their slender profiles, each of the large columnar neurons falls into the field of one Purkinje cell axonal cone whereas elsewhere, the multipolar neurons tend to share their well spread dendrites with neighboring Purkinje axonal fields. The small neurons that span columns in the central zone are oriented to sample larger numbers of axonal inputs than are adjacent columnar neurons.Supported in part by U.S. Public Health Service Research Grants NS10536, NS03659, Training Grant NS 05591 from the National Institute of Neurological Diseases and Stroke, and a William F. Milton Fund Award from Harvard University.     

Serotonin-immunoreactive varicosities in the cell body region and neural sheath of the snail, Helix pomatia, ganglia: an electron microscopic immunocytochemical study

The distribution and connections of serotonin-immunoreactive fibers in the cell body region and neural sheath of the central ganglia of the snail, Helix pomatia, have been examined. The cell body region of the ganglia is supplied by an extremely dense network of varicose serotonin-immunoreactive fibers which surround neuronal perikarya in the ganglia. Immunoreactive processes also run to the neural sheath of both the ganglia and the peripheral nerve roots, forming a dense network. Electron microscopy revealed five different connections of serotonin-immunoreactive varicosities, according to their target: (i) non-specialized contacts with neuronal perikarya; (ii) non-specialized contacts with axon processes on the surface of the peripheral nerve roots; (iii) non-specialized neuromuscular connections with smooth muscle fibers in the neural sheath; (iv) varicosities engulfed by glial processes in both the cell body region and neural sheath; (v) varicosities embedded in the connective tissue elements of the sheath either partly or completely free of glial processes. In all cases of appositions no membrane specializations could be observed on either site of the contacts. These observations provide morphological evidence for non-synaptic regulatory actions of serotonin-containing neurons in Helix central nervous system: (i) modulation of the activity of neuronal perikarya; (ii) involvement in neuromuscular regulation; (iii) neurohormonal modulation of peripheral processes by release through the neural sheath.     

Immunohistochemical localization of the high-affinity NGF receptor (gp 140-trkA) in the adult human dorsal root and sympathetic ganglia and in the nerves and sensory corpuscles supplying digital skin

Background: Nerve growth factor (NGF) is produced in target issues of sympathetic and neural-crest derived sensory neurons, including skin, to provide them trophic support. The biological effects of NGF on responsive cells are mediated by specific high-affinity receptors. Recently, a protein tyrosine kinase of ? 140 kDa molecular weight, encoded by the proto-oncogene trkA, has been identified as the high-affinity NGF receptor (gp140-trkA). The present work was undertaken to study the localization of gp140-trkA-like immunoreactivity (IR) in human peripheral ganglia (sympathetic and dorsal root ganglia), and in glabrous skin. Methods: Lumbar dorsal root ganglia, para- and prevertebral sympathetic ganglia, and digital glabrous skin were studied immunohistochemically using a rabbit anti-gp140-trkA polyclonal antibody. In order to accurately establish the localization of gp140-trkA IR, the neurofilament proteins and S-100 protein were studied in parallel in: (1) sensory and sympathetic ganglia, to label neuron cell bodies and satellite or supporting cells, respectively; (2) human skin, to label axons, Schwann and related cells within nerves and sensory corpuscles. Moreover, a quantitative study (neuron size, intensity of immunostaining) was carried out on sympathetic and dorsal root ganglia neuron cell bodies. Results: A specific gp140-trkA-like IR was found in: (1) a subpopulation (65%) of primary sensory neuron cell bodies, including most of the largesized ones but also small- and intermediate-sized ones; (2) most of sympathetic neuron cell bodies (82%); (3) theineurial cell, Schwann cells, and large axons of the nerve trunks supplying digital skin; (4) the lamellar cells of Meissner corpuscles; (5) the central axon, inner-core, outer-core, and capsule of Pacinian corpuscles. In addition, the occurrence of gp140-trkA-like IR was observed in some non-nervous tissues of the skin, including epidermis (mainly in the basal layer), sweat glands, and arterial blood vessels. Conclusions: Present results provide evidence for the localization of gp140-trkA-like IR in: (1) nerve cells which are known to be NGF-responsive, and (2) non-nervous cutaneous tissues which are innervated by NGF-dependent peripheral neruons. These findings suggest that, in addition to the well-established role of NGF on sensory and sympathetic neurons, this neurotrophin may be able to regulate some other functions on non-nervous cell which are targets for NGF-dependent peripheral neurons. © 1994 Wiley-Liss, Inc.     

Immunocytochemical evidence for a serotoninergic innervation of dorsal column postsynaptic neurons in cat and monkey: Light- and electron-microscopic observations

Dorsal column postsynaptic neurons in the lumbosacral enlargements of cats and a monkey were retrogradely labeled by placing horseradish peroxidase on their severed axons in the thoracic dorsal columns. After visualizing the retrogradely-labeled neurons, the tissue was immunocytochemically stained with an antiserum directed against serotonin. Immunoreactive axonal varicosities contacted the perikarya and proximal dendrites of every retrogradely-labeled neuron examined in cat (mean 61 contacts/cell) and nearly every neuron in the monkey (mean 18 contacts/cell). Electron microscopy showed that the immunoreactive axonal varicosities contained pleomorphic (round to oval) agranular vesicles and formed symmetrical synapses on retrogradely-labeled neurons.

It is concluded that dorsal column postsynaptic neurons are innervated directly by the brain stem's descending, serotoninergic system(s).