摘要:

AbstractThe development of fetal layer I (marginal zone, MZ) was studied in the human neocortex by using DiI tracing and AChE and NADPH‐d histochemistry, and examining the Nissl‐stained material of the Yakovlev Collection. We describe the sequential maturation of the Cajal‐Retzius (CR) cells and the granule cells of the subpial granular layer (SGL), and the close relationship between both. The first CR cells appear in the primordial plexiform layer, at 6 gestational weeks (GW). After the formation of the cortical plate, they settle under the pial surface. At 13 GW, the SGL begins to form around the CR cells. The horizontal members of a polymorphic population of CR cells begin to mature at 13 GW, and the intermediate and vertical forms differentiate at 16 and 18 GW, respectively. All CR cells project into an axonal plexus in the lower third of the MZ. From 18 GW, CR cells and SGL become segregated, and the polymorphic CR cells lie now below the SGL, with which they remain connected by ascending processes. Granule cells invade the lower MZ contacting somata and processes of CR cells. The somata of vertical CR cells elongate until 23/24 GW when they show degenerative signs. After 24 GW, all polymorphic CR cells die. Granule cells degenerate after 24 GW; the SGL disappears at 28/30 GW. A population of persisting CR cells, morphologically different from the transient polymorphic forms, appears in a subpial position and survives in small numbers throughout life. Small non‐CR neurons differentiate first in the lower half of layer I, thereafter also in the upper half. Histochemically, all CR cells are AChE‐positive; they contain NADPH‐d only transiently at 20 GW. We propose that CR cells and SGL provide a transient innervation network for the developing cortical plate at a time when the definitive fiber systems of the molecular layer are not yet established. © 1993 Wil

ISSN:0092-7317    

DOI:10.1002/cne.903380302

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractRelatively little is known about the development of GABAAreceptor subunits and their gene expression in mammalian spinal cord. The expressions of mRNAs encoding 13 GABAAreceptor subunits (α1–6, β1–3, γ1–3, and δ) in embryonic, postnatal, and adult rat spinal cord and dorsal root ganglia (DRG) cells were studied by in situ hybridization and reverse transcription‐polymerase chain reaction (RT ‐ PCR) analysis. Both techniques revealed the presence of all subunit mRNAs originally found in the rat brain, except for α6, which was not detectable, and δ, which was weakly detected only by RT‐PCR. Two anatomically distinctive sets of subunit mRNAs were found by in situ hybridization within the ventricular zone (VZ) and mantle zone (MZ). The trio of α4, β1, and γ1 subunit mRNAs emerged exclusively in neuroepithelial cells at embryonic day 13 (E13) and remained detectable in the VZ until E17. In the MZ, β3 subunit mRNA was first detected at E12, while α2, α3, α5, β2, γ2, and γ3 transcripts appeared at E13. Expressions of the subunit mRNAs in the MZ rapidly increased and expanded in a ventrodorsal sequence from motoneurons to dorsal horn neurons before reaching a peak in the late embryonic/early postnatal period. The mRNA expressions declined during postnatal development, by region‐selective depletion, with α4, α5, β1, β2, γ1, and γ3 subunit mRNAs becoming barely detectable. In contrast, α2, α3, β3, and γ2 transcripts persisted into adulthood with distinct anatomical distributions. RT‐PCR analysis revealed unique developmental patterns in the intensities of PCR products, most of which were in good agreement with developmental changes in the densities of hybridized mRNA signals. However, RT‐PCR amplified minute amounts of mRNAs for α1, α4, α5, β1, β2, γ1, γ3, and δ subunits in adults, which were not found in film autoradiograms, but could be detected in a few grain‐positive cells in emulsion‐dipped sections. DRG cells expressed α2, α3, α5, β2, β3, and γ2 subunit mRNAs during embryogenesis but only α2, β3, and γ2 subunit mRNAs were reliably detected in the adult. The transient expression of α4β1γ1 subunit mRNAs primarily in the VZ correlates with the period of neurogenesis, while the developmental changes of α2, α3, β3, and γ2 subunit mRNAs in the MZ parallels previously reported changes in GABA expression and in synapse formation and elimination. These results implicate a role of early‐expressed GABA and GAB

ISSN:0092-7317    

DOI:10.1002/cne.903380303

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractAn understanding of the normal organization of prefrontal cortex is essential to the recognition of pathology underlying human behavioral disorders believed to depend on this region. We have therefore studied the pattern of intrinsic intra‐ and interlaminar pyramidal neuron connectivity in prefrontal areas 9 and 46 (of Walker) in macaque monkey cerebral cortex (anterior to the arcuate sulcus between the principal sulcus and midline). We made focal (200–400 μm) injections of biocytin and mapped the pattern of orthogradely transported label. Injections made into the superficial layers label wide‐ranging lateral projections within the same areas of prefrontal cortex. Projections local to such small injections form a narrow band of terminals in layers 1–3 (200–400 μm wide, 2–4 mm long) centered on the injection site. Collateral fibers spread orthogonal to this terminal band, making frequent bifurcations, to establish a series of parallel bands of terminals with uninnervated bands between, spaced regularly across the cortex (center to center 500–600 μm). The entire pattern of terminal label is stripelike, with occasional narrower interbands and crosslinks between the bands, and can extend over 7–8 mm across the cortex. These projections arise from pyramidal neurons in layers 2, 3, and 5 and terminate in layers 1–3. The stripelike pattern contrasts with patchlike patterns in other cortical regions (V1, V2, V4, motor, somatosensory) and is smaller in scale than stripelike zones of corticocortical afferent terminals to this region, reported to be 300–750 μm wide and spaced 1.0–1.5 mm center to cente

ISSN:0092-7317    

DOI:10.1002/cne.903380304

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe distributions of five NMDA receptor channel subunit mRNAs in the mouse forebrain at postnatal day 21 were semiquantitatively examined by in situ hybridization with subunit‐specific oligonucleotide probes. In contrast to ubiquitous distribution of the ζ1 subunit mRNA throughout the forebrain, distributions of four ϵ subunit mRNAs were highly variable from nucleus to nucleus. The telencephalon (except for the septum) expressed the ϵ1 and ϵ2 subunit mRNAs. Various combinations of the ϵ1, ϵ2, ϵ3, and ϵ4 subunit mRNAs were present in different nuclei of the septum, the olfactory bulb, and the thalamus. In the hypothalamus, the suprachiasmatic nucleus expressed distinct signals for the ϵ3 subunit mRNA alone, whereas other nuclei showed faint signals for the ϵ1, ϵ2, and ϵ4 subunit mRNAs. Moreover, different signal levels of the ϵ subunit mRNAs were found in various regions. The hippocampal CA1 region expressed higher signals for the ϵ1 and ϵ2 subunit mRNAs than the CA3 region and the dentate gyrus. In the cerebral cortex, signal levels of the ϵ1 subunit mRNA were higher in the laminae II/III, IV, and VI than the lamina V, whereas those of the ϵ2 subunit mRNA were highest in laminae II/III and lowest in laminae IV and V. Different signal levels between the ϵ1 and ϵ2 subunit mRNAs were also discerned in the amygdala, the caudate‐putamen, and the thalamus. The distinct anatomical distributions and differential signal levels of the ϵ subunit mRNAs strongly suggest different subunit organizations of the NMDA receptor channel in different forebrain neurons, which may result in functional diversity of the channel in vivo.

ISSN:0092-7317    

DOI:10.1002/cne.903380305

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractRecent work in nonmammalian vertebrate retinas has suggested that other cell types besides the generally accepted amacrine cells may contain serotonin. We have used immunocytochemical methods to study serotonin‐like immunoreactivity (5‐HTLI) in the retina of the developing and mature frogRana pipiens.In the adult, two types of serotonin immunoreactive (5‐HT‐ir) cells were found in the inner nuclear layer (INL) of the retina. Additionally, a large population of cells in the retinal ganglion cell layer (RGCL) had 5‐HTLI. These cells were grouped into three types based on their soma size and their primary dendritic branching pattern. The optic nerve fiber layer was also intensely stained with serotonin antisera although staining intensity decreased progressively as the fibers approached the optic nerve head. Severing the optic nerve resulted in 5‐HT‐ir elements that extended up the optic nerve shaft from the lesion site toward the retina. Both regional and temporal changes in the pattern of 5‐HTLI were seen. In middle regions of retina, approximately 30% of the cells in the RGCL were 5‐HT‐ir. Nasal and temporal regions of central retina had significantly fewer 5‐HT‐ir cells. Early in development only scattered cells in the RGCL were 5‐HT‐ir. As the animals matured there was an increase in both the proportion and the staining intensity of these cells. Our results suggest that in studying the function and development of the visual system in this animal, the role of serotonin must be exami

ISSN:0092-7317    

DOI:10.1002/cne.903380306

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractNuclei of the circadian visual system are extensively innervated by serotoninergic neurons and rhythmicity is modulated by the serotoninergic system. This study investigated the temporal relationships between prenatal origins of serotoninergic cell groups and perinatal innervation of structures in the hamster circadian visual system as well as in the remaining diencephalon. Serotonin‐immunoreactive (5‐HT‐IR) neurons of the B4‐B9 complex were first seen on embryonic day 8 (E8). The number of neurons increases sharply by E10 when the first 5‐HT‐IR cells are evident in the medulla (B1–B3 complex). The distribution of serotoninergic neurons in the hamster brainstem is generally adult‐like by E14. Thick 5‐HT‐IR fibers arch around the mesencephalic flexure at E10 and reach more rostral mesencephalic areas at E11.A branch of the medial forebrain bundle (MFB) projects ventrally toward the retrochiasmatic area; a second branch ascends along the fasciculus retroflexus. Fibers cross the midline in the supraoptic commissure by E12, others arrive in the lateral geniculate region, and a branch of the MFB extends toward the mammillary area. At E13, a periventricular medial thalamic branch of the MFB is seen, axons appear in the supramammillary commissure, and a fine fasciculus between the medial thalamus and intergeniculate leaflet is visible. Lateral, paraventricular, and retrochiasmatic hypothalamic areas and centro‐ and dorsomedial thalamus are densely innervated at E14. The mammillary area and lateral geniculate body are moderately innervated, and the first fibers appear in the deep laminae of the superior colliculus. The innervation of the suprachiasmatic nuclei, periventricular hypothalamus, and superficial layers of the superior colliculus occurs postnatally. The results are consistent with serotoninergic system development in other species.

ISSN:0092-7317    

DOI:10.1002/cne.903380307

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe purpose of the present study was to determine the pattern and density of retinal projections to the dorsal lateral geniculate nucleus (dLGN) following ablation of visual cortical areas in developing cats of different postnatal ages and in mature cats. The terminations of retinal projections to the dLGN were evaluated following the injection of tritiated amino acids into one eye. Regardless of age, a visual cortical ablation of areas 17 and 18 induces massive death of neurons within the regions of the dLGN that are linked topographically to the cortical areas removed. However, the pattern of retinal projections to these degenerated regions of the dLGN differs depending upon whether the cortical lesion is incurred early in postnatal life or in adulthood. Following ablation on the day of birth (P1), virtually all surviving cells were found in the C‐complex of dLGN with only a token number in the A‐laminae. Correspondingly, retinal projections were maintained to the C‐complex of the nucleus and were barely detectable in the degenerated A‐laminae. However, in cats in which areas 17 and 18 had been removed in adulthood (≥ 6 months of age) retinal projections were maintained to the A‐laminae even though nearly all neurons in those laminae had degenerated. Moreover, a subgroup of animals that incurred area 17 and 18 ablations at P1 showed that the modification of retinal projections to the A‐laminae occurs within the first postnatal month, and an additional subgroup showed that retinal projections become increasingly resistant to the degenerative events in the dLGN that follow ablation of areas 17 and 18 at progressively older ages during the first postnatal month. Furthermore, retinal inputs also respond, in an age‐dependent way, to degeneration of neurous in the C‐complex induced by extension of the cortical ablation to include extrastriate visua areas. © 19

ISSN:0092-7317    

DOI:10.1002/cne.903380308

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractWe studied the development of corticotectal synaptic terminal boutons and synapses by making injections of wheat germ agglutinin conjugated to horseradish peroxidase (WGA‐HRP) into area 17 of visual cortex in kittens ranging from newborn to 12 weeks of age and in adults. The location and extent of the injection site, and labeled corticotectal axon terminals in the superficial layers of the superior colliculus were demonstrated histochemically with the cobalt‐glucose oxidase diaminobenzidine reaction.During the first 2 weeks after birth, the majority of labeled profiles resembled axonal growth cones, or structures intermediate in morphology between growth cones and synaptic terminals, while very few corticotectal axon terminals forming well‐defined synaptic contacts were observed. Labeled synaptic terminals in kittens at 1 and 2 weeks of age were small, contained very few synaptic vesicles, which were usually restricted to the contact zone, and exhibited few mitochondria. By 4 and 6 weeks after birth, a well‐developed population of synaptic terminals was established; however, growth cones and intermediate profiles were still numerous. At 8 weeks of age synaptic terminals were morphologically mature, and growth cone‐like profiles were no longer observed.To study quantitative changes in synapse development we used the disector method to obtain unbiased estimates of the density and number of corticotectal synaptic terminals and synapses; both the density and number of terminals and synapses increased steadily throughout postnatal development. These results suggest that the corticotectal projection develops by the progressive elaboration of synapses, as opposed to synapse overproduction and subsequent elimination. © 1993 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903380309

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.903380310

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY