摘要:

AbstractThis study assessed interspecies differences in regional brain distribution of [3H]QNB binding, [125I]α‐bungarotoxin binding and acetylcholinesterase activity, by autoradiographic and histochemical methods. Eleven mammalian species were examined, including carnivores (cat, dog), a lagomorph (rabbit), and rodents (squirrel, guinea pig, gerbil, hamster, vole, lemming, rat, mouse). Comparisons were based on primary visual system structures (superior colliculus, lateral geniculate nucleus, primary visual cortex) and the hippocampal formation. The two radioligands differed greatly in the degree of interspecies variation: while the pattern of [3H]QNB binding was quite similar across species, [125I] α‐bungarotoxin showed striking interspecies diversity. This contrast was most obvious in laminar patterns of the visual cortex and hippocampal formation. Regional distributions of acetylcholinesterase staining were fairly diverse, and were unlike the patterns of either [3H]QNB or [125I]α‐bungarotoxin. The two ligands showed more consistency in overall levels across species than did acetylcholinesterase. Possible correlates of the differences in interspecies diversity are discussed. © 1993 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903290402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractIn recent years, GABAergic neurons have been identified in the basal forebrain where cholinergic cortically projecting neurons are located and known to be important in mechanisms of cortical activation. In the present study in the rat, the relationship of the GABA‐synthesizing neurons to the acetylcholine‐synthesizing neurons was examined by application of a sequential double staining immunohistochemical procedure involving the peroxidase‐antiperoxidase technique for glutamic acid decarboxylase (GAD) and choline acetyltransferase (ChAT). In these double and adjacent single immunostained series of sections, the GAD+ and ChAT+ cells were mapped, counted and measured with the aid of a computerized image analysis system.Through the entire basal forebrain, there was no evidence for colocalization of GAD and ChAT in the same neurons. Instead, a large population of GAD‐immunoreactive neurons is codistributed with ChAT‐immunoreactive neurons and outnumbers them by a factor of two: approximately 39,000 GAD+ cells to 18,000 ChAT+ cells. Although the GAD+ and ChAT+ neurons lie intermingled within fascicles of the major longitudinal and transverse forebrain fiber systems in subregions of the basal forebrain, the GAD+ cells are more highly concentrated within different sectors of the pathways and regions than the ChAT+ cells. Although GAD+ neurons resemble ChAT+ neurons in certain regions, both being bi‐ or multipolar and, on average, medium‐sized cells, the GAD+ neurons are, in the majority (51%), small‐sized cells (<15 μm in length) and as a population significantly smaller than the ChAT+ neurons. These results suggest that many GABAergic neurons may represent interneurons in the basal forebrain and potentially exert an inhibitory influence on adjacent cortically projecting cholinergic neurons. Medium‐ to large GAD+ cells, which resemble similar ChAT+ cells, are also present and represent the majority of the GAD+ cells in the nucleus of the diagonal band of Broca, magnocellular preoptic nucleus, and olfactory tubercle, but represent the minority in the anterior and posterior substantia innominata and globus pallidus. Given their prominent size, such GABAergic cells may also exert an inhibitory influence outside the basal forebrain as projection neurons and potentially in parallel with cholinergic neurons, to certain regions of the cerebral cortex. Accordingly, GABAergic cells may be considered as constituents of the magnocellular basal nucleus and potentially important elements within the ventral extrathalamic relay from the brainstem reticular formation to the cerebral cortex. © 1

ISSN:0092-7317    

DOI:10.1002/cne.903290403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractI have investigated the morphology of neurons in the thalamic reticular nucleus (TRN) by means of intracellular injections in fixed tissue in order to study whether neurons in visual (dorsocaudal part), somatosensory (intermediate part), or limbic/motor (rostral part) sectors in the rat, rabbit, and cat differ morphologically in relation to their different sensory cortical or thalamic inputs. In addition, I have compared the different mammalian species to ask whether there is a morphological difference of TRN neurons according to reported differences in the intrinsic thalamic organisation, for example, due to the presence of GABAergic local circuit neurons in the majority of thalamic nuclei in the cat and the lack of those neurons in most of the rat thalamic nuclei, and presynaptic dendrites in the cat but not in the rat. In all animals investigated so far, neurons in the caudal (visual) and intermediate (somatosensory) part of the TRN have an elongated dendritic morphology in all three species, but some neurons in the rostral part, in particular in dorsal sections, have a distinctive multipolar morphology. Neurons have round, ovoid, or elongated somata ranging in area between 150 and 860 μm2. In general 4–8 first order dendrites emerge directly from the two poles of the soma or from a thick stem segment. Most of the dendrites then run parallel to the borders of the nucleus extending for relatively long distances, up to 450 μm, but remain inside the border of the nucleus. Only a few (1–3) dendrites could be observed to run perpendicular to the border of the nucleus and generally only for a short distance (20–70 μm). Some of the smooth first order dendrites give rise to second order dendrites (up to 200 μm in length), which then branch into short (15–70 μm) third order dendrites. Dendritic spines and varicosities, spine‐like protusions and/or hair‐like processes are mainly found on second and third order dendrites. Surprisingly, the shape, arrangement, and the size of the dendritic field are not strictly related to the shape and size of the nucleus. In mammalian species with a comparatively narrow TRN (rat and cat) the dendritic field size was similar to that in the rabbit with a broad TRN. There was considerable variability in dendritic morphology in the caudal and intermediate parts of TRN. However, in contrast to two recent studies in the rat TRN I have found no obvious basis for classification of neurons in the mammalian TRN according to dendritic morphology. In addition, there seems to be no difference in neuronal morphology of TRN neurons in relation to different intrinsic thalamic organisation within or between species. © 199

ISSN:0092-7317    

DOI:10.1002/cne.903290404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe spinal cord terminations of two electrophysiologically identified single C‐fibers (one identified as a C‐nociceptor) were intraaxonally labeled with horseradish peroxidase and analyzed with both light and electron microscopy. Serial section ultrastructural analysis and postembedding immunocytochemical techniques for calcitonin gene‐related peptide (CGRP), substance P (SP), and GABA were used to study the synaptology, and neuropeptide content.All C‐terminal synapses were in laminae I and II. The terminals sampled (n = 73) from these two C‐fibers rarely established glomerular synaptic complexes, but rather, simple terminals, usually measuring 1–4 μm in length and 1–3 μm in diameter. They most often established 1 or 2 (range 1 to 5) quite large asymmetric axodendritic synaptic contacts. Postsynaptic structures included dendritic spines and shafts with and without vesicles. C‐terminals were filled with small round synaptic vesicles (45–60 nm) and also contained variable numbers of large dense‐core vesicles (LDCVs, 80–110 nm). LDCVs inside identified C‐terminals frequently displayed CGRP immunoreactivity. We were unable to detect SP immunoreactivity inside our sample of C‐fiber LDCVs. C‐terminals were never found postsynaptic to other profiles.Thus, the C‐fiber terminals sampled in this study have simple synaptology, do not receive presynaptic control and contain CGRP immunoreactivity. They differ greatly from the terminals of Aδ nociceptors studied previously by our group that had glomerular endings, often received presynaptic input and did not contain CGRP immunoreactivity. This suggests the existence of different processing mechanisms, at the level of the first synapse, for nociceptive inputs arriving to lamina I and II through different types of primary a

ISSN:0092-7317    

DOI:10.1002/cne.903290405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe central arborizations in the dorsal horn of the spinal cord of 23 rapidly adapting (RA) A‐beta primary afferent neurons innervating different regions of the glabrous skin of the hindpaw were studied by the intra‐axonal injection of horseradish peroxidase in adult rats. A total of 284 arbors of the complex, simple, and blind‐ending variety were recovered. The arbors of RA afferents innervating the toes, paw pads, and non‐pad hindpaw differed from each other in branch pattern and dimensions. The simple and complex arbors, which are both bouton‐containing, were distributed mainly in laminae III–V, although some complex arbors projected dorsally into lamina IIi.The hindpaw glabrous skin afferent terminals were located in the lumbar enlargement from caudal L3 to rostral L6. A crude somatotopic organization was observed such that toes 1–5 were represented successively in more caudal positions from mid‐L4 to caudal L5. The paw pads were organized in a rostrocaudal sequence moving from the paw pads proximal to toe 1 across the foot to the paw pads proximal to toe 5, from caudal L3 to mid‐L5. Non‐pad hindpaw afferents were located in caudal L5. Overlap between toe, paw pad and non‐pad afferent central fields was present, however, and the central terminals of afferents with non‐adjacent peripheral receptive fields were shown to occupy the same region of the dorsal horn.

ISSN:0092-7317    

DOI:10.1002/cne.903290406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractTo elucidate the role of neuron‐glia cell adhesion molecule (Ng‐CAM) in axonal pathway formation of avian spinal interneurons, we have examined the ultrastructural expression of Ng‐CAM in the developing spinal cord, by using a preembedding immunocytochemical method. Ng‐CAM immunoreactivity was punctate and was restricted to cell surfaces. In accordance with our previous light microscopic observations (Shiga et al., '90), the earliest developing spinal interneurons were Ng‐CAM‐positive on their cell bodies, axons, and growth cones. Axons and growth cones that were either fasciculated or in contact with each other strongly expressed Ng‐CAM, thus indicating the possible involvement of Ng‐CAM in fasciculation of axons and in the contact guidance of growth cones along preexisting axons. By using higher resolution immunoelectron microscopy, the present study has also revealed new information on the subcellular localization of Ng‐CAM on developing spinal interneurons, neuroepithelial cells, and floor plate cells. Although Ng‐CAM immunoreactivity was prominent on both axons and growth cones, these structures were Ng‐CAM‐negative when they contacted the basal lamina around the spinal cord. By contrast, Ng‐CAM was detectable on the surface of both neuroepithelial cells and floor plate cells only when they made contact with the Ng‐CAM‐positive axons and growth cones of interneurons. These results suggest that the subcellular distribution of Ng‐CAM is regulated differentially, depending on the apposing cell surfaces, and that such differential and developmentally regulated expression may contribute to the elongation, fasciculation, and guidance of spina

ISSN:0092-7317    

DOI:10.1002/cne.903290407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractIn order to determine their morphological development and ontogenetic fate, Martinotti neurons immunoreactive for substance P and somatostatin have been analysed in the cat visual cortex. Martinotti neurons are located in layers V and VI. They are multipolar to bitufted, and most dendrites remain in layers V and VI. Their typical feature is the ascending axon, which emerges from an apical dendrite or from the upper pole of the soma. A number of collaterals branch off in layer V, forming a local terminal plexus. The axon then branches into 2–8 collaterals, which ascend as a bundle to layers III and II, where a second terminal plexus is formed. Some collaterals ascend to layer I where they adopt a horizontal course. Horizontal collaterals in the terminal layers V, III, II, and in layer I may reach up to 400 μm in length.Martinotti neurons begin to differentiate perinatally. The quantitative analysis reveals that the initial time course of differentiation of Martinotti cells is very similar in material stained for substance P and for somatostatin. Double immunofluorescence then confirms that the two peptides are colocalized in Martinotti cells of layers V and VI during the early postnatal period. Further, substance P is colocalized with GABA.Substance P expression in Martinotti cells can be observed only in the immature visual cortex. After postnatal day 15, the Martinotti neuron system becomes less and less detectable by substance P immunoreactivity. It declines to virtually undetectable levels after the third postnatal month. The adult visual cortex is almost devoid of substance P‐immunoreactive cell bodies, processes and axon terminals. In situ hybridization confirms this finding, revealing beta‐preprotachykinin mRNA‐expressing cell bodies in layers V and IV at postnatal day (P)6 and P12, but not in the adult cortex. This suggests a downregulation of the substance P expression at the transcriptional level.In contrast, somatostatin‐immunoreactive Martinotti cells, most of which have coexpressed substance P during early postnatal life, can still be observed in the adult cortex. Thus, the Martinotti neurons constitute a persisting cell type, although many individual neurons of this type disappear during the second postnatal month by degeneration and cell death.In summary, while somatostatin is permanently expressed in Martinotti neurons in the cat visual cortex, substance P peptide and mRNA are transiently expressed during an early postnatal period, and apparently are downregulated later in development. © 1993 Wile

ISSN:0092-7317    

DOI:10.1002/cne.903290408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe hindbrain is evolutionarily conserved among diverse vertebrate phyla. In vertebrate embryos, the hindbrain is segmentally organized as a series of overt swellings known as rhombomeres. In the larval zebrafishBrachydanio rerio, conspicuous and identifiable reticulospinal neurons are positioned in the center of rhombomeres. Segmentally homologous reticulospinal neurons that share a range of morphological, developmental, and biochemical features occupy adjacent rhombomeres.We have recently shown that reticulospinal neurons of the zebrafish survive ontogeny without considerable morphological modification and we suggested that homologous neurons may share similar functions at different stages of development (Lee and Eaton: Journal of Comparative Neurology304:34–52, 1991). The goldfishCarassius auratus, a related cyprinid, is especially suited for neurophysiological and behavioral studies. However, it is not yet known if the various reticulospinal neurons of zebrafish are generalizable to other species such as the goldfish. Therefore, we sought to examine the extent to which reticulospinal neurons of the zebrafish are also present in the adult goldfish.Analysis of 45 brains retrogradely labeled with horseradish peroxidase (HRP) from the spinal cord showed that reticulospinal neurons are arranged as a series of seven segments within the hindbrain; a regular interval of approximately 200 μm separates adjacent segments. Although the goldfish reticulospinal system has more neurons than the zebrafish, many reticulospinal neuron types continue to be identifiable. Moreover, comparisons of dendritic arborizations and axon paths between the two species showed that the morphology between various neuron types is virtually identical. The cross‐taxonomic similarities between the reticulospinal systems of these related cyprinids make it possible to pursue functional considerations of segmentally homologous neurons in the goldfish hindbrain. © 1993 Wiley‐Li

ISSN:0092-7317    

DOI:10.1002/cne.903290409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.903290401

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY