摘要:

AbstractThe circuit from the cochlear nucleus magnocellularis to the nucleus laminaris supports the encoding and measurement of interaural time differences in the auditory brainstem. Specialization for the encoding of temporal information include the few and/or short dendrites and thick axons of the magnocellular and laminaris neurons, and the high degree of convergence in the circuit.Magnocellular cells have large cell bodies covered with somatic spines. The cells have few dendrites, and the number of dendrites decreases from low to high best frequency regions of the nucleus. Magnocellular neurons receive both auditory nerve terminals and GABAergic terminals with symmetric synapses and terminals filled with pleomorphic vesicles.The axonal projections of magnocellular neurons to the nucleus laminaris form maps of interaural time difference. About 100 magnocellular afferents from each side converge on each laminaris neuron, and the terminals from each side do not occupy separate domains on the cell. These terminals form punctate asymmetric synapses on both the dendrites and the cell bodies of laminaris neurons. Laminaris neurons also receive GABAergic terminals which form symmetric synapses. Laminaris neurons have oval cell bodies covered with very short dendrites. The cells in the low best frequency region of the nucleus laminaris have longer dendrites. © 1993 Wiley‐Liss, I

ISSN:0092-7317    

DOI:10.1002/cne.903340302

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

年代:1993

数据来源: WILEY

摘要:

AbstractIn order to gain a more complete understanding of the sequential pattern of gene expression during neurogenesis and gliogenesis in humans, we followed the expression of well‐characterized, developmentally regulated polypeptides in the cerebellar cortex and dentate nucleus by immunohistochemistry using monoclonal antibodies of highly defined specificity. At 8–10 weeks gestational age (GA), progenitor cells and their immediate progeny in the rhombencephalic ventricular zone expressed vimentin and nestin and, to a lesser extent, microtubule‐associated protein 5 (MAP5) and glial fibrillary acidic protein (GFAP), but not the low affinity nerve growth factor receptor (NGFR). In contrast, postmitotic, migrating immature neurons in the intermediate zone gave strong reactions for MAP2, tau, and a nonphosphorylated form of middle molecular weight neurofilament (NF) protein (NF‐M) and weak reactivity for NGFR. At 15 weeks GA, proliferating cells of the superficial part of the cerebellar external granular layer stained only for NGFR, while more deeply situated cells of the external granular layer stained positively for NGFR, MAP2, MAP5, tau, and chromogranin A, which correlates with the early outgrowth of parallel fibers. All phosphoisoforms of NF‐M as well as the low (NF‐L) and high (NF‐H) molecular weight NF proteins and alpha‐internexin were expressed in the somatodendritic domain of Purkinje cells and dentate nucleus neurons from about 20 weeks GA with a gradual compartmentalization of highly phosphorylated forms of NF‐M and NF‐H into axons by the end of gestation. Alpha‐internexin was also expressed strongly in axons of the deep white matter from 20 weeks GA to adulthood. MAP2, synaptophysin, and NGFR showed early, transient expression in the somatodendritic domain of Purkinje cells followed by the appearance of a 220 kDa nestin‐like peptide that continued to be expressed in adult Purkinje cells. Notably, developing dentate nucleus neurons expressed many of these proteins in a similar temporal sequence. Early in the developing cerebellar cortex, the expression of NF protein and synaptophysin occurred in discrete patches or columns similar to those described for other antigens (i.e., zebrins). Finally, radial glia were positive for vimentin, GFAP, and nestin from 8 weeks GA to 8 months postnatal. This study describes the distinct molecular programs of lineage commitment in cerebellar progenitor cells and in differentiating neurons and astrocytes of the human cerebellum. The acquisition of a mature molecular neuronal phenotype correlates with the establishment of structural polarity in cerebellar neurons.

ISSN:0092-7317    

DOI:10.1002/cne.903340303

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

年代:1993

数据来源: WILEY

摘要:

AbstractDorsal root ganglion (DRG) neurons decrease their substance P (SP) synthesis after peripheral nerve lesions. Levels in the dorsal horn also decline but return to normal if regeneration is successful. In adults, when regeneration is prevented, recovery of SP in the dorsal horn is slow and incomplete, whereas in newborns, recovery is rapid and complete even though retrograde cell death of DRG neurons is greater than in adults. We have examined the mechanisms that might account for the rapid and complete recovery of SP and calcitonin‐gene related peptide (CGRP) in the dorsal horn after peripheral nerve injury in newborns. Peptides were compared in the L4 and L5 DRG and spinal cord segments of normal rats and in rats surviving 6 days to 4 months after sciatic nerve section/ligation within 24 hours of birth.Sciatic nerve section/ligation produced 50% neuron death in L4 and L5 DRGs, but immunocytochemical methods showed that both SP‐immunoreactivity (‐IR) and CGRP‐IR recovered completely in dorsal horn. Radioimmunoassay confirmed that recovery of SP was not an artefact due to shrinkage. β‐Preprotachykinin (PPT)‐mRNA hybridization and SP‐IR were observed mostly in small neurons; α‐CGRP‐mRNA‐hybridized and CGRP‐IR neurons were more heterogeneous. The percentage of DRG neurons that contained SP (∼ 25%) or CGRP (∼ 50%) was the same in normal newborn and adult rats. Neither selective cell survival nor change in neuron phenotype was likely to contribute to the recovery seen in the dorsal horn, and DRG neurons ipsilateral to the lesion exhibited the same level of hybridized β‐PPT‐mRNA and α‐CGRP‐mRNA as intact DRG neurons. Because neither the constitutive level of expression of the genes nor peptide levels increased above those observed in intact DRG neurons, these mechanisms were also not responsible. Axotomized DRG neurons, however, contributed to recovery. Recovery was also due to sprouting by neurons in intact DRGs rostral and caudal

ISSN:0092-7317    

DOI:10.1002/cne.903340304

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

年代:1993

数据来源: WILEY

摘要:

AbstractBy using the combined Golgi/electron microscopy (EM) technique and postembedding immunocytochemistry for gamma‐aminobutyric acid (GABA), we describe a novel type of local circuit neuron in the rat fascia dentata that gives rise to an axon profusely ramifying in the dentate molecular layer. The relatively small ovoid cell body (long axis 12–15 μm) is located directly underneath the granular layer. From both poles of the cell body dendritic processes emerge that enter the molecular layer and hilar region, respectively. The apical dendrites traverse the granular layer, invade the molecular layer, and branch in the same way as granule cell dendrites. Some branches reach the hippocampal fissure. Thus, the apical dendrites of these neurons may receive a similar input pattern as the granule cells. The dendrites are smooth, occasionally bearing varicosities. A few spines are regularly observed. The axon originates from the apical dendrite and traverses the molecular layer horizontally for up to 500 μm. It gives off numerous collaterals that are distributed throughout the entire width of the molecular layer and only rarely enter the granule cell layer. Electron microscopy of the cell body of gold‐toned neurons revealed the well‐known fine‐structural characteristics of nonpyramidal neurons, i.e., an indented nucleus with nuclear inclear inclusions and large aggregations of endoplasmic reticulum. Apical as well as basal dendrites are densely covered with presynaptic boutons, mainly forming asymmetric synapses. The axon terminals of these cells form symmetric synapses with dendritic shafts and, to a lesser extent, with spines. These symmetric synapses, together with the results of our GABA postembedding immunocytochemical study, suggest that this cell is a GABAergic inhibitory neuron that almost exclusively innervates the dentate molecular layer. Together with data from the literature on dentate axoaxonic cells (which innervate the axon initial segments of the granule cells) and GABAergic basket cells (which innervate the granule cell somata and proximal dendrites in the granular layer), the present results indicate that there is a lamination of the GABAergic innervation of the fascia dentata corresponding to the well‐known segregated termination of entorhinal and commissural afferents to this region. © 1993 W

ISSN:0092-7317    

DOI:10.1002/cne.903340305

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

年代:1993

数据来源: WILEY

摘要:

AbstractAnterograde tracing with horseradish peroxidase (HRP) was used to compare the organization of retinotectal projections in normal adult hamsters and in animals that sustained subcutaneous injections of the neurotoxin 5,7‐dihydroxytryptamine (5,7‐DHT) on the day of birth. Neonatal injection of this neurotoxin decreases the density of the serotoninergic (5‐HT) innervation of the cerebral and cerebellar cortices, but increases the density of these fibers in the brainstem including the superior colliculus (SC). Analysis of tissue from the retinorecipient laminae of the SC by high‐pressure liquid chromatography indicated that these lesions increased the amount of 5‐HT in the adult SC by 47%. The increased serotoninergic innervation of SC was associated with a marked change in the distribution of the uncrossed retinotectal projection. In normal adult hamsters, fibers from the ipsilateral eye form dense clusters in the lowermost stratum griseum superficiale (SGS) and stratum opticum (SO). A small number of uncrossed fibers are also visible in the more caudal portions of these layers. In the animals that sustained neonatal 5,7‐DHT injections, uncrossed retinotectal fibers formed a nearly continuous band in rostral SO and lower SGS, and numerous labeled fibers were present in the caudal SC, primarily in the SO. Neonatal treatment with 5,7‐DHT also produced alterations in the crossed retinotectal pathway and in the crossed and uncrossed retinogeniculate projections. These results indicate that the 5‐HT input to the developing brainstem may strongly influence the development of retinofugal projections. © 1993

ISSN:0092-7317    

DOI:10.1002/cne.903340306

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

年代:1993

数据来源: WILEY

摘要:

AbstractWe investigated the source of axons and terminals in the cat's lateral geniculate nucleus that stain positively for NADPH‐diaphorase. The functional significance of such staining is that NADPH‐diaphorase is identical to the enzyme nitric oxide synthetase, and thus it is though to reveal cells and axons that use nitric oxide as a neuromodulator. Within the lateral geniculate and adjacent perigeniculate nuclei, a dense network of axons and terminals is labeled for NADPH‐diaphorase, The pattern of NADPH‐diaphorase staining here is remarkably similar to that of choline acetyltransferase (ChAT) staining, suggesting that the source of these axons and terminals might be the parabrachial region of the brainstem because this provides the major cholinergic input to the lateral geniculate nucleus. In other areas of the brain to which parabrachial axons project, there is also a similar staining pattern for NADPH‐diaphorase and ChAT. Furthermore, the patterns of cell staining within the parabracial region for NADPH‐diaphorase and ChAT are virtually identical. However, the relationship between ChAT and NADPH‐diaphorase staining for the parabrachial region is not a general property of cholinergic neurons. Other cholinergic cells and axons, such as the trochlear nerve, the oculomotor nerve and nucleus, and the parabigeminal nucleus, which all label densely for ChAT, stain poorly or not at all for NADPH‐diaphorase. It is significant that the parabigeminal nucleus, which provides a cholinergic input to the lateral geniculate nucleus, has no cells that label for NADPH‐diaphorase. We used double labeling methods to identify further the source of NADPH‐diaphorase staining in the lateral geniculate nucleus. We found that parabrachial cells co‐localize NADPH‐diaphorase and ChAT. Noradrenergic and serotoninergic cells in the brainstem also innervate the lateral geniculate nucleus, but we found that none of these co‐localize NADPH‐diaphorase. Finally, by combining NADPH‐diaphorase histochemistry with retrograde labeling of cells that project to the lateral geniculate nucleus, we found that the cholinergic cells of the parabrachial region are essentially the sole source of NADPH‐diaphorase in the lateral geniculate nucleus. We thus conclude that cells from the parabrachial region that innervate the lateral geniculate nucleus use both acetylcholine and nitric oxide for neurotransmission, and that this is virtually the only afferent input to this region that uses nitri

ISSN:0092-7317    

DOI:10.1002/cne.903340307

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

年代:1993

数据来源: WILEY

摘要:

AbstractMammalian central nervous system neurons do not regenerate after axonal injury, unlike their counterparts in fish and amphibians. After axonal injury, glial cells in mammals do not support regrowth of axons, while in fish they support the regeneration process. Controversy exists as to whether or not the intact fish optic nerve expresses glial fibrillary acidic protein, a well‐known marker for mature astrocytes, and thus whether its astrocytes differ in this respect from those of the brain and spinal cord, as well as from optic nerve astrocytes of other species. In an attempt to resolve this question we cloned fish glial fibrillary acidic protein. Two different complementary DNA clones were isolated from a carp brain complementary DNA library, each encoding a different form of glial fibrillary acidic protein apparently originating from different genes. Monospecific polyclonal antibodies were raised against a peptide synthesized according to the predicted amino acid sequence, and used to identify and localize the fish glial fibrillary acidic protein. Two glial fibrillary acidic proteins (of 49 kDa and 51 kDa) were identified by the antibodies in all tested fish central nervous system tissues. The antibodies were then used to examine glial fibrillary acidic protein immunoreactivity in sections taken from uninjured and injured optic nerves of goldfish. Injury was followed by an elevation in glial fibrillary acidic protein immunoreactivity along the whole length of the nerve, except at the site of the injury, where—as in the case of vimentin—no immunoreactivity was detectable. However, in contrast to vimentin‐positive glial cells, which repopulate the site of the injury soon after the optic nerve is injured, glial fibrillary acidic protein‐positive glial cells remained outside the injury site for as long as 6 weeks after the injury. Despite the injury‐induced changes in glial fibrillary acidic protein immunoreactivity, no change was observed in the level of transcript encoding glial fibrillary acidic protein after injury, while there was an increase in the amount of glial fibrillary acidic protein associated with the cytoskeleton and a reduction in the soluble form. These results suggest that the injury‐induced changes in immunoreactivity on sections involve changes not in transcription or translation of glial fibrillary acidic protein, but in glial fibrillary acidic protein compartmentalization. © 1993 W

ISSN:0092-7317    

DOI:10.1002/cne.903340308

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

年代:1993

数据来源: WILEY

摘要:

AbstractNeural connections between the mushroom body (MB) and other protocerebral areas of the honeybee's brain were studied with the help of cobalt chloride and Golgi staining methods. Focal injections of cobalt ions into the α‐lobe neuropil of the MB reveal seven clusters of somata located in the protocerebrum and deutocerebrum of each brain hemisphere. These neurons connect the mushroom body neuropil with protocerebral areas and number approximately 400. They contact the layered organization of the α‐lobe at different locations. Some project not only into the α‐lobe, but also into the β‐lobe and pedunculus neuropils. Fifteen cell types which form intraprotocerebral circuits are morphologically described. They can be divided into three categories: (1) unilateral neurons, with projection fields restricted to the ipsilateral protocerebrum; these neurons connect the α‐lobe with areas in the protocerebral lobe and ramify with densely layered arborisations arranged perpendicularly to the longitudinal axis of the α‐lobe; (2) recurrent neurons, which interconnect subcompartments of the MB, forming loops at different leveles of the neuropil; their arborisations are mainly restricted to the α‐lobe, β‐lobe, pedunculus, and calyces of the ipsilateral MB; they also ramify sparsely around the neuropil of the α‐lobe; and (3) bilateral neurons, which either interconnect both α‐lobes or connect the ipsilateral α‐lobe and protocerebral lobe with the dorsolateral protocerebral lobe of the conntralateral hemisphere. The connections of different compartments of the MB with other parts of the protocerebrum as revealed in this study are discussed in the context of hypotheses about the functional role of MBs in the honeyb

ISSN:0092-7317    

DOI:10.1002/cne.903340309

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe hypoglossal nucleus contains serotonin and several different serotonin receptors, and serotonin is present in fibers and terminals contacting hypoglossal motoneurons. Serotonin alters the excitability of hypoglossal motoneurons, and may influence hypoglossal motoneuron activity in a variety of physiological processes. Since the hypoglossal nucleus contains no serotoninergic somata, the present study sought to identify the sources of serotoninergic afferents to the hypoglossal nucleus. Fluorogold was injected into the hypoglossal nucleus and serotoninergic immunofluorescence was utilized in a dual‐fluorescence technique to identify the sources of serotoninergic afferents to the hypoglossal nucleus. The results demonstrate that most serotoninergic afferents to the hypoglossal nucleus originate from the nuclei raphe pallidus and obscrus, while fewer originate from the nucleus raphe magnus and the parapyramidal region. Other regions of the medial tegmental field and the pons that contain both serotoninergic neurons and neuronal afferents to the hypoglossal nucleus contain no double‐labeled neurons. © 1993 Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903340310

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe distribution of histamine‐, octopamine‐, gamma‐aminobutyric acid‐ (GABA) and taurine‐like immunoreactivity in the bivalve molluscMacoma balthicawas studied immunocytochemically with antisera produced in rabbits. Histamine levels in the ganglia and whole animals were also measured by high‐performance liquid chromatography using a postcolumn derivatization method. Immunoreactivity for these substances, except for taurine, is found in the central nervous system of this species. The most extensive neuronal system is revealed with the antiserum against histamine. All the main ganglia contain histamine‐immunoreactive cell bodies, and a dense network of nerve fibers is seen in the ganglia and nerve roots. Histamine‐immunoreactive nerve fibers project to the mantle edge, lips and oesophagus. The basal part of the inhalant siphon is rich in histamine‐immunoreactive fibers. Unlike histamine, octopamine‐ and GABA‐like immunoreactivities are restricted to the central nervous system. Taurine‐like immunoreactivity is not found in the nervous system of this species. In the nervous system, histamine‐immunoreactive cell bodies and fibers are more numerous than those that are octopamine‐ and GABA‐immunoreactive. The distribution of these substance in the ganglia is different. GABA‐immunoreactive cells are typically smaller than most of the histamine‐ and octopamine‐immunoreactive cells. Most GABA‐ and octopamine‐immunoreactive cells and fibers are located in the pedal ganglion. Histamine is distributed more evenly in the ganglia and nerve roots. The biochemical measurements of histamine correlate well with the immunohistochemical findings and confirm the predominant location of the amine in the nervous tissue. These results suggest that histamine is more widespread than some other putative transmitters, and support the concept that histamine may have an important role in many physiological proces

ISSN:0092-7317    

DOI:10.1002/cne.903340311

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

年代:1993

数据来源: WILEY