摘要:

AbstractGlomerular organization of the antennal (olfactory) lobe is initiated by the arrival of sensory axons from the antenna. Bundles of axon terminals coalesce into spheroidal knots of neuropil called protoglomeruli. Previous studies have suggested that the protoglomeruli form a template for the mature glomerular array, but an early role for projection neurons in establishing the template has not been excluded. We examined with the confocal laser scanning microscope the morphological development of the uniglomerular projection neurons during the stages in which glomeruli are constructed. Groups of projection neurons were stained with the lipophilic dye DiI to assess the development of the population as a whole; individual neurons were filled intracellularly with Lucifer Yellow to examine in detail the development of shape. In some preparations, sensory axons and glial cells also were labeled by using different fluorescent dyes to reveal possible interactions between projection neuron dendrites and sensory axons or glial cells.Protoglomeruli form in a wave beginning at the entry point of the antennal nerve and proceeding across the lobe to the opposite pole. A second wave follows in which projection neurons become tufted and innervate the newly formed glomeruli, sometimes extending into the glial border surrounding the protoglomeruli. In animals deprived of sensory axons, some projection neurons still form tufted dendritic trees and, in one region of the neuropil, a glomerulus‐like structure.The early presence of projection neuron processes in the protoglomeruli and the formation of at least one glomerulus‐like structure in unafferented lobes suggest that uniglomerular projection neurons play an active role in the construction of olfactory glomeruli. © 1994 Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903500102

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe midbrain periaqueductal grey matter (PAG) has numerous functional roles that include mediating nociceptive inhibition and integrating behavioural and physiological responses to potentially threatening or stressful stimuli. Underlying these behaviours is the diverse interconnectivity of this region, and it is possible that neurochemical subdivisions within the PAG reflect the functional properties of the different PAG regions. In this study, using in situ hybridization, we have investigated the distribution in the rat PAG of the messenger ribonucleic acids (mRNAs) encoding seven neuropeptides: enkephalin (ENK), substance P (SP), somatostatin (SST), galanin (GAL), vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY), and calcitonin gene‐related peptide (CGRP). Each peptide mRNA had a distinct topographical distribution in the PAG. Preproenkephalin A (ENK) mRNA‐expressing cells were found at all levels of the PAG in three distinct longitudinal columns. Preprotachykinin A (SP)‐expressing cells were found at all levels of the PAG, principally in the Edinger‐Westphal nucleus and the lateral and dorsal PAG. There was a column of neurones producing mRNA‐encoding somatostatin that extended along the rostrocaudal extent of the ventrolateral PAG; there were also labelled cells in the dorsal and dorsolateral subdivisions at some levels of the PAG. Galanin mRNA‐producing neurones were limited to the dorsal raphe nucleus and to a second population in the ventral border of the aqueduct. VIP mRNA‐producing neurones were found in very localized regions of the PAG, including the cell‐sparse region immediately ventral to the aqueduct and the ventral part of the dorsal raphe nucleus. NPY mRNA‐producing neurones were localized mainly in some cells of the Edinger‐Westphal nucleus and dorsal raphe nucleus. CGRP mRNA‐expressing neurones were limited to the oculomotor and trochlear nucleus. The results showed a topographical distribution of neuropeptides over the rostrocaudal extent of the PAG that is compatible with the emerging theory that the anatomical and functional specificity of the PAG is expressed in the form of longitudinally arranged neuronal columns that extend for varying distances along the rostrocaudal axis of the midbrain PAG.

ISSN:0092-7317    

DOI:10.1002/cne.903500103

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractFor a better insight into general and derived traits of developmental aspects of catecholaminergic (CA) systems in amniotes, we have studied the development of these systems in the brain of a lizard,Gallotia galloti, with tyrosine hydroxylase (TH)‐ and dopamine (DA) immunohistochemical techniques. Two main groups of TH‐immunoreactive (THi) perikarya appear very early in development: one group in the midbrain which gives rise to the future ventral tegmental area, substantia nigra and retrorubral cell groups, and another group in the tuberomammillary hypothalamus. Somewhat later in development, TH/DA‐immunoreactive cells are observed in the thalamus, rostrodorsal hypothalamus and spinal cord, and, with another delay, in the suprachiasmatic nucleus, the periventricular organ, and the pretectal posterodorsal nucleus. CA cell groups that appear rather late in development include the cells in the olfactory bulb, the locus coeruleus and the caudal brainstem. As expected, the development of immunoreactive fibers stays behind that of the cell bodies, but reaches the adult‐like pattern just prior to hatching.The present study revealed considerable variation in the relation between the state of cytodifferentiation and first expression of TH/DA immunoreactivity between CA cell groups. Catecholamine cells in the midbrain and tuberomammillary hypothalamus are still migrating, immature (absence of dendrites) and express only TH immunoreactivity at the time of first detection. Cells which appear at later developmental stages lie already further away from the ventricle, possess two or more dendritic prccesses, and generally express both TH‐ and DA immunoreactivity. © 1994 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903500104

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractGalanin was purified from an extract of the stomach of the rainbow trout,Oncorhynchus mykiss, and its primary structure was established as Gly‐Trp‐Thr‐Leu‐Asn‐Ser‐Ala‐Gly‐Tyr‐Leu10‐Leu‐Gly‐Pro‐His‐Gly‐Ile‐Asp‐Gly‐His‐Arg20‐Thr‐Leu‐Ser‐Asp‐Lys‐His‐Gly‐Leu‐Ala. Trout galanin shows six amino acid substitutions compared with pig galanin, but the N‐terminal region (residues 1–14) has been fully conserved. The distribution of galanin‐immunoreactive (GAL‐IR) structures in the trout brain and pituitary was studied via immunohistochemistry. GAL‐IR cell bodies were observed only in the caudal telencephalon, the preoptic region, and the mediobasal hypothalamus. GAL‐IR fibers, however, are widely distributed throughout the brain, with a much lower density in the midbrain and posterior brain than in the tel‐ and diencephalon. Particularly dense innervation of the mediobasal hypothalamus, the ventral and supracommissuralis parts of the caudal telencephalon, and the region above and below the anterior commissure was observed. A heavy innervation of the pituitary was consistently detected. GAL‐IR fibers were present in neurohypophyseal digitations of both the anterior and intermediate lobes with highest density in the region of the proximal pars distalis, where growth hormone and gonadotropic cells are located. Fibers were also seen in digitations of the rostral pars distalis, in particular between the prolactin follicles. The distribution of GAL‐IR neurons in the central nervous system and pituitary of the trout suggests that the peptide may exercise an important role in the regulation of neuroendocrine func

ISSN:0092-7317    

DOI:10.1002/cne.903500105

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe development of the vibrissae and their innervation and the maturation of the brainstem trigeminal sensory nuclei have been studied in the wallaby,Macropus eugenii, from birth to adulthood. At birth, developing vibrissal follicles consist of solid epidermal pegs surrounded by dermal condensations. The developing follicles and adjacent skin are innervated by trigeminal afferents. Ten days after birth the follicle contains a dermal papilla and the deep vibrissal nerve can be recognised. A hair cone is present at postnatal day (P) 30 and hairs are apparent on the skin surface by P35. By P63 the deep vibrissal nerve can be seen innervating Merkel cells in the outer root sheath; in addition, the first signs of the blood sinus can be recognised. Innervation of the inner conical body and lanceolate and lamellated receptors supplying the mesenchymal sheath and waist region are not seen until P119, when the follicle resembles that seen in the adult.At birth, central processes of the trigeminal ganglion cells have entered the trigeminal tract and extend from the rostral pons to the upper cervical cord. Labelling with a carbocyanine dye at P0 shows afferents extending medially from the tract into the trigeminal subnuclei at all levels. At this stage the trigeminal nuclei appear as areas of increased cell density in the lateral brainstem. By P30–40 the four subnuclei can be distinguished on the basis of shape, cytoarchitecture, and succinic dehydrogenase reactivity. Adult morphology is not fully established until P210. In mature animals, nucleus principalis contains closely packed, polymorphic cells, frequently aligned parallel to thick fibre bundles that traverse the nucleus obliquely. Subnuclei oralis and interpolaris contain sparsely distributed, medium to large cells, randomly oriented, as well as prominent rostrocaudally directed fibre bundles. Subnucleus caudalis consists of the marginal layer, substantia gelatinosa, and magnocellular layers as described in other species.Patches of increased succinic dehydrogenase or cytochrome oxidase reactivity, presumably corresponding to the vibrissae, are present in subnuclei principalis, interpolaris, and caudalis in developing and adult animals, although the pattern is less clear than in rats. The brainstem patches are first seen at P40, approximately 6 weeks before the corresponding vibrissal‐related pattern develops in the cortex. This suggests that the onset of patch formation may be regulated independently at different levels of the pathway. © 1994 Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903500106

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractIn order to examine to what extent the neuronal and metabolic activities of avascular vertebrate retinae are reflected in the morphology of their Müller cells we have studied (by using several monoclonal antibodies) the morphology of Müller cells in two species of diurnal birds (chicken,Gallus domesticus, and pigeon,Columba livia) and one species of nocturnal saltwater crocodiles (Crocodylus porosi). In all three species, the outer nuclear layer is relatively thin and the Müller cell trunks divide into rootlets that wrap around the photoreceptors. In both diurnal birds studied, the trunks of Müller cells in the inner plexiform layers invariably divide into numerous fine filamentous processes that terminate in small expansions covering most of the vitreal surface of the retina. Furthermore, the networks of filamentous processes of birds' Müller cells exhibit conspicuous horizontal lamination in the inner plexiform layer. In contrast, the filamentous processes arising from the individual Müller cell trunks of the crocodile, if present, are much less numerous and less widely spread than those of diurnal birds. It is proposed that the splitting of the Müller cell trunks into numerous filamentous processes terminating in small vitreal expansions represents a morphological adaptation for: (1) effective spatial buffering of K+ions in thick and presumably metabolically highly active, yet avascular, avian retinae, and (2) effective absorption and distribution of nutrients leaking from the vitreally located supplemental nutritive organ, the pecten. © 1994 Wiley‐

ISSN:0092-7317    

DOI:10.1002/cne.903500107

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractWe have studied the early development of the uncrssed retinofugal projection in the gray short‐tailed opossum. Axons that form the adult uncrossed retinofugal projection arise from the temporal crescent of the retina and reach the optic chiasm on postnatal day 7. The sites at which the uncrossed fibres segregate from the crossed fibres and the pattern of this segregation are very different from those seen in eutherian mammals. In the opossum, the uncrossed fibres segregate from the crossed fibres within the juxtachiasmatic part of the optic nerve before they have encountered either the fibres of the other eye or midline structures of the ventral diencephalon. The uncrossed fibres turn perpendicular to the axis of the nerve and grow dorsoventrally through the crossed projection to gather as a discrete bundle at the ventral edge of the nerve. The abrupt divergence of the uncrossed fibres occurs at a border between two glial cell types: the interfascicular glia that characterise the main part of the optic nerve and the radial glia of the juxtachiasmatic part of the nerve. At the ventral part of the nerve, the bundle of uncrossed fibres turns caudally across the axis of the nerve and enters the ipsilateral optic tract. When retinofugal fibres encounter the border between the interfascicular and radial glia, a very specific axonal reorganisation occurs in marsupials, and this is strikingly different from the axonal reorganisation that occurs at the same site in eutherians, where essentiallyallretinofugal fibres reorganise, not just the uncrossed component. We believe this to be an important example of an identified cellular element that has quite distinct axon‐guidance properties in different species. © 1994 Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903500108

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractEarly commissural axons in the zebrafish spinal cord extend along a pathway consisting of a ventrally directed ipsilateral, a contralateral diagonal, and a contralateral longitudinal segment. The midline floor plate cell is one important cue at the transition from the ipsilateral to the contralateral pathway segments. In order to identify additional guidance cues, the interactions between commissural growth cones and their substrates were examined at the electron microscopic level in the different pathway segments. The growth cones extended near the superficial margin of the spinal cord, within filopodial reach of three bilateral longitudinal axon pathways that were ignored irrespective of whether other axons were already present. Ultimately the commissural growth cones pioneered an additional independent longitudinal pathway in the dorsolateral spinal cord. Neuroepithelial cells were extensively contacted in the lateral marginal zone of the dorsal spinal cord and are thus in a position to contribute to the establishment of the longitudinal commissural pathway segment. The extent of contact with neuroepithelial cells in the ventral spinal cord was dependent on whether commissural growth cones had already crossed the ventral midline: ipsilateral, but not contralateral, growth cones showed extensive contacts with neuroepithelial processes and minor contacts with the basal lamina. In marked contrast, commissural growth cones that had already crossed the ventral midline and entered the diagonal pathway segment showed major appositions to the basal lamina. Extensive contact with the basal lamina was first established in the ventral midline region, where crossing growth cones always inserted between the basal lamina and the base of the midline floor plate cells. This indicates that a change occurs in the response characteristics of commissural growth cones as they cross the ventral midline of the spinal cord. Such a change could help to explain why the growth cones extend first toward but then away from the ventral midline. 1994 Wiley‐Liss. In

ISSN:0092-7317    

DOI:10.1002/cne.903500109

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractChanges in the expression of neurotransmitter receptors in developing cerebral cortex may be related to the functional maturation of distinct areas. In the present study, we have tested whether GABAAreceptor expression in neonatal rats reflects the differentiation of cortical areas. Specifically, the α1 subunit, one of the most prevalent GABAAreceptor subunits in adult cerebral cortex, is up‐regulated postnatally, suggesting a link with the establishment of inhibitory circuits. Using immunohistochemistry with a subunit‐specific antiserum, we observed a striking area‐ and lamina‐specific increase in staining for GABAAreceptors containing the α1 subunit (α‐GABAAreceptors), from low levels in neonates to an intense and uniform staining in adults. Already at birth, the α‐subunit immunoreactivity selectively demarcated the boundaries of certain cortical areas. In particular, the primary somatosensory (S1) and visual (V1) areas were distinctly delineated with a band of α1‐subunit immunoreactivity located in the developing layers III and IV. The staining ended abruptly at the presumptive boundaries of S1 and V1, adjacent areas being unstained at this age. Around postnatal day 3, clusters of α‐subunit positive cells were seen in layers III–IV of S1 and V1 extending their dendrites up to layer I, where they arborized profusely. In addition, the distribution of α‐GABAAreceptors in S1 revealed in detail the differentiation of the barrel field during early postnatal development. Although staining was observed in all areas by postnatal day 6, differences in the laminar distribution of α‐GABAAreceptors persisted for at least 1 more week. Our results provide evidence for the existence of area‐specific boundaries in neocortex of newborn rats before layers III–IV are fully differentiated and innervated by cortical afferents. Furthermore, the area‐ and lamina‐specific maturation of α‐GABAAreceptor staining demonstrates the value of this marker for investigating the cytoarchitectonic differentiation of cortical areas

ISSN:0092-7317    

DOI:10.1002/cne.903500110

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractPrimary sensory neurons that are motoneuron‐like in morphology and often nonspiking (transmit afferent signals as graded depolarizations) characterize an unusual type of stretch receptor in decapod crustaceans. Nonspiking and spiking receptors occur in similar positions at homologous joints in different species and have been presumed to be homologous, the spiking one considered „primitive.”︁ To better understand the evolutionary origin of these stretch receptors and why some are nonspiking, we examined the spiking telson‐uropod stretch receptors in the spiny sand crabBlepharipoda occidentalis(Albuneidae) and the squat lobsterMunida quadrispina(Galatheidae) and compared them with the nonspiking telson‐uropod stretch receptor of the mole sand crabEmerita analoga(Hippidae). The position, morphology and responses to stretch of the sensory neurons, and the ultrastructure of the elastic strand portion of the receptor are similar inM. quadirspinaandB. occidentalis, except that inB. occidentalisthe receptor muscles are substantially smaller and the extracellular matrix of the elastic receptor strand is both more extensive and more organized, reminiscent of the ultrastructure ofE. analoga'snonspiking receptor. We conclude that the spiking telson‐uropod stretch receptors of albuneids and galatheids are homologous. The differences in the ultrastructure of their receptor strands imply that the efficiency of coupling receptor length change to deformation of the dendritic termini increases in the orderM. quadrispina

ISSN:0092-7317    

DOI:10.1002/cne.903500111

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY