摘要:

AbstractPrevious studies indicate that tuberculoventral and cartwheel cells in the dorsal cochlear nucleus as well as a group of stellate cells in the ventral cochlear nucleus are likely to be glycinergic. To test whether these neurons contain higher levels of free glycine than cells that are probably not glycinergic, immunocytochemical studies with antibodies against glycine conjugates were undertaken on slices of the murine cochlear nuclear complex. Present results show that the cell bodies of all three groups of neurons are immunolabeled. However, the somatic labeling of the tuberculoventral and cartwheel cells can be modulated by experimental conditions. In slices fixed immediately after cutting, many cell bodies in the deep layer of the dorsal cochlear nucleus (DCN), presumably tuberculoventral neurons, are labeled. As a slice is incubated in vitro, cell bodies in the deep layer of the DCN lose their glycine‐like immunoreactivity. After 7 hours in vitro, labeled cells are absent in the deep DCN, but the immunoreactivity can be regained by electrically stimulating the auditory nerve for 20 minutes. The loss of immunoreactivity is prevented by electrical stimulation, by axotomy, and by inclusion of 0.8 μM tetrodotoxin, or 1 μM strychnine, or 50 μM colchicine or 50 μM μ‐lumicolchicine in the bathing saline. Cartwheel cells retain their immunoreactivity during incubation in vitro without electrical stimulation, but lose it under two conditions. One is following a cut across the ventral cochlear nucleus (VCN) that severs most of their granule cell input, and the other is the inclusion of tetrodotoxin in the bathing saline. The labeling of cell bodies in the ventral cochlear nucleus and of puncta and processes is not changed by any of these experimental manipulations. © 1994 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903390302

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe principle neuronal output of the neostriatum comes from medium spiny neurons that project from the caudate/putamen to the globus pallidus and substantia nigra. Although current evidence generally indicates that γ‐aminobutyric acid (GABA) is the principal neurotransmitter in this pathway, this cannot account for the excitatory synaptic activity present among cultures of striatal neurons or the short latency excitatory postsynaptic potentials which often proceed or obscure inhibitory activity evoked by striatal stimulation. In this study, retrograde transport of [3H]D‐aspartate has been used to demonstrate striatopallidal and striato‐nigral neurons that possess a high‐affinity uptake system for glutamate and aspartate and are therefore putatively glutamatergic. Injections of [3H]D‐aspartate into the globus pallidus or substantia nigra, pars reticularis of the rat retrogradely labeled mediumsized neurons throughout the rostral‐caudal extent of the neostriatum. To characterize this population further, adjacent sections were immunoreacted with antibodies to either GABA, glutamic acid decarboxylase (GAD), calbindin, or parvalbumin prior to autoradiographic processing. Under these conditions, autoradiographically labeled neurons displayed positive immunoreactivity for GABA, GAD, or calbindin. Autoradiographic label did not colocalize with parvalbumin immunoreactivity. The colocalization of anatomical markers of GABAergic and glutamatergic neurotransmission raises the possibility that both neurotransmitters are functionally expressed within single striatal projection neurons. © 1994 Wi

ISSN:0092-7317    

DOI:10.1002/cne.903390303

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe gamma aminobutyric acidA/benzodiazepine (GABAA/BZ) receptor is a multisubunit (α, β, γ, δ, and ρ) ligand‐gated chloride channel; there are several variants of the α, β, and γ subunits, each of which has been localized throughout the central nervous system. A large number of GABAA/BZ subunit variants are expressed within the cerebellar cortex. In previous studies from other laboratories, α6subunit mRNA has been reported to be present exclusively in cerebellar granule cells. The developmental expression of α6mRNA in cerebellar and cochlear granule cells is of interest because it has been suggested that each of these cell types is derived from a common precursor pool. The polymerase chain reaction was used to generate a cDNA fragment encoding a portion of the M3–M4 intracellular loop of the α6subunit of the GABAA/BZ receptor. A [35S] riboprobe, transcribed from this cDNA fragment, was used to examine the expression of the α6subunit mRNA by in situ hybridization in developing normal mice and in adult mutant mice with known deficits in synaptic circuitry. A strong hybridization signal was observed over the granule cell layers of both the cerebellum and cochlear nuclei in adult mice. The signal over the cochlear nuclei appeared after birth toward the end of postnatal week 1, coinciding with the appearance of labeling in the cerebellar cortex. The intensity of the hybridization signal in both regions increased rapidly until postnatal day 14, after which it increased more gradually, reaching adult levels during postnatal week 3. In the weaver mutant, α6labeling was detected in surviving granule cells, but not in cerebellar regions devoid of granule cells. Significant levels of the α6hybridization signal were also present in cerebellar granule cells of Purkinje cell degeneration, lurcher, and staggerer mutants, suggesting that aberrations in synaptic circuitry do not prevent α6subunit gene expression.Our results demonstrate that α6subunit mRNA is not limited to the cerebellum, but is expressed in other neurons which share a common cellular precursor pool. These data also suggest that these granule cell precursors may be intrinsically programmed to acquire a specific form of the GABAA/BZ receptor, irrespective of their final location and lack of connections with target neurons. ©

ISSN:0092-7317    

DOI:10.1002/cne.903390304

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe nucleus isthmi is reciprocally connected to the ipsilateral optic tectum. Ablation of the nucleus isthmi compromises visually guided behavior that is mediated by the tectum. In this paper, horseradish peroxidase (HRP) histochemistry and electron microscopy were used to explore the synaptic interrelationships between the optic tectum and the ipsilateral nucleus isthmi. After localized injections of HRP into the optic tectum, there are retrogradely labeled isthmotectal neurons and orthogradely labeled fibers and terminals in the ipsilateral nucleus isthmi. These terminals contain round. Clear vesicles of medium diameter (40–52 nm). These terminals make synaptic contact with dendrites of nucleus isthmi cells. Almost half of these postsynaptic dendrites are retrogradely labeled, indicating that there are monosynaptic tectoisthmotectal connections.Localized HRP injection into the nucleus isthmi labels terminals primarily in tectal layers B, E, F, and 8. The terminals contain medium‐sized clear vesicles and they form synaptic contacts with tectal dendrites. There are no instances of labeled isthmotectal terminals contacting labeled dendrites. Retrogradely labeled tectoisthmal neurons are contacted by unlabeled terminals containing medium‐sized and small clear vesicles. Fifty‐four percent of the labeled fibers connecting the nucleus isthmi and ipsilateral tectum are myelinated fibers (average diameter approximately 0.6 μm). The remainder are unmyelinated fibers (average diameter approximately 0.4 μm). © 1994 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903390305

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe spinal pia mater receives a rich innervation of small sensory axons via the ventral roots. Other sensory axons enter the ventral roots but end blindly or turn abruptly in hairpin loop‐like formations and continue in a distal direction. In the present study, the content of substance P (SP)‐, calcitonin gene‐related peptide (CGRP)‐, growth‐associated protein (GAP‐43)‐, and low‐affinity neurotrophin receptor protein (p75NGFr)‐like immunoreactivity (‐LI) associated with these different types of sensory axons was assessed with light and electron microscopic immunohistochemical techniques. In addition, the binding of antibodies against synthetic peptides representing unique sequences of residues in the products of thetrkandtrkB protooncogenes was analyzed. These genes encode membrane spanning proteins, which have been shown to constitute specific high affinity binding sites for several members of the nerve growth factor family of neurotrophic factors.The results of the present study imply that the ventral root afferents comprise several different types of sensory axons, which all contain SP‐, CGRP‐, GAP‐43‐, and p75NGFr‐like immunoreactivities. In addition, at least some of the presumed sensory fiber bundles in ventral roots and the pia mater were immunoreactive for thetrkB gene product. Moreover, leptomenin‐geal cells and nonneuronal cells of the ventral roots were shown to bind antibodies to both thetrkandtrkB gene products. The ventral root afferents seem to share their immunohistochemical pattern with pain‐transducing axons at some other locations, such as the tooth pulp. The contents of SP‐ and CGRP‐LI in sensory axons that reach the central nervous system (CNS) through the ventral root indicate that ventral root afferents may be involved in sensory mechanisms, such as the ventral root pain reaction, as well as in the control of the pial blood vessels. The demonstration of GAP‐43 and neurotrophin receptor‐immunoreactivities associated with unmyelinated fibers in ventral roots and the pia mater is discussed in relation to previous reports on postnatal plasticity in these a

ISSN:0092-7317    

DOI:10.1002/cne.903390306

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

年代:1994

数据来源: WILEY

摘要:

AbstractClusterin (SGP‐2) is a newly described glycoprotein associated with several putative functions including responses to brain injury. This study reports the regional and cell type expression of clusterin mRNA and its encoded glycoprotein in the rat brain; a limited comparison was also done with the human brain. Using in situ hybridization combined with immunocytochemistry, we found that astrocytes and neurons may express clusterin mRNA in the normal adult brain. While astrocytes throughout the brain contained clusterin mRNA, there was regional selectivity for neuronal clusterin expression. In the striatum, clusterin mRNA was not detected in neurons. Only a subset of substantia nigra dopaminergic neurons or locus ceruleus noradrenergic neurons (tyrosine hydroxylase immunopositive) contained clusterin mRNA. However, neuronal clusterin mRNA was prevaìent in pontine nuclei and in the red nucleus of the midbrain tegmentum. Similarly, clusterin mRNA was prevalent in both rat and human hippocampal neuron‐specific enolase immunopositive pyramidal neurons, although rat CA1 neurons had less mRNA than CA2–CA3 neurons. Monotypic primary cell cultures from the neonatal rat showed clusterin mRNA in both neurons and astrocytes, but not in microglia.By immunocytochemistry, no clusterin immunopositive glia were observed in any region of the rat brain, confirming previous studies. However, clusterin immunopositive cells (putative neurons) were observed in the Purkinje cell layer of the cerebellum, medial and interposed cerebellar nuclei, trigeminal motor nucleus, and red nucleus. Finally, in vitro studies suggest that astrocytes, but not neurons, secrete clusterin, which is pertinent to clusterin immunodeposits found after experimental lesioning. © 1994 Wiley‐

ISSN:0092-7317    

DOI:10.1002/cne.903390307

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe aim of this study is to describe the postnatal change in dendritic morphology of those motoneurons in the hypoglossal nucleus that innervate the genioglossus muscle. Forty genioglossal (GG) motoneurons from four age groups (1–2, 5–6, 13–15, and 19–30 postnatal days) were labeled by intracellular injection of neurobiotin in an in vitro slice preparation of the rat brainstem and were reconstructed in three‐dimensional space.The number of primary dendrites per GG motoneuron was ∼6 and remained unchanged with age. The development of these motoneurons from birth to 13–15 days was characterized by a simplification of the dendritic tree involving a decrease in the number of terminal endings and dendritic branches. Motoneurons lost their 6th–8th order branches, in parallel with an elongation of their terminal dendritic branches maintaining the same combined dendritic length. The elongation of terminal branches was attributed to both longitudinal growth and the apparent lengthening caused by resorption of distal branches. The elimination of dendritic branches tended to increase the symmetry of the tree, as revealed by topological analysis. Later, between 13–15 days and 19–30 days, there was a reelaboration of the dendritic arborization returning to a configuration similar to that found in the newborn. The length of terminal branches was shorter at 19–30 days, while the length of preterminal branches did not change, suggesting that the proliferation of branches at 19–30 days takes place in the intermediate parts of terminal branches.The three‐dimensional distribution of dendrites was analyzed by dividing space into six equal volumes (hexants). This analysis revealed that GG motoneurons have major components of their dendritic tree oriented in the lateral, medial, and dorsal hexants. Further two‐dimensional polar analysis (consisting of eight sectors) revealed a reconfiguration of the tree from birth up to 5–6 days involving resorption of dendrites in the dorsal, dorsomedial, and medial sectors and growth in the lateral sector. Later in development (between 13–15 days and 19–30 days), there was growth in all sectors, but of a greater magnitude in the dorsomedial, medial, and dorsolatera

ISSN:0092-7317    

DOI:10.1002/cne.903390308

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe distribution of cortical efferent connections to brainstem vestibular nuclei was quantitatively analysed by means of retrograde tracer substances injected into different electrophysiologically identified parts of the brainstem vestibular nuclear complex of five Java monkeys (Macaca fascicularis). Three polysensory vestibular areas were found to have a substantial projection to the vestibular nuclei: area 2v located at the tip of the intraparietal sulcus, the parietoinsular vestibular cortex (PIVC) covering the most occipital part of the granular insula (Ig) and the retroinsular area (Ri or reipt), and the dorsolateral part of the somatosensory area 3a (“area 3aV” neck/trunk region). From physiological recording experiments, these three cortical fields were known to contain many neurons responding to stimulation of semicircular canals as well as to optokinetic (area 2v, PIVC) and somatosensory stimuli (PIVC, area 3a). These three regions form the inner cortical vestibular circuit. Besides these polysensory vestibular cortical fields, three other circumscribed cortical regions of the macaque brain were also found to project directly to the brainstem vestibular nuclei: a circumscribed part of the postarcuate premotor cortex (area 6pa), part of the agranular and the adjacent dysgranular cortex located around the cingulate sulcus (area 6c/23c), and a predominantly visual (optokinetic) association field located at the fundus of the lateral sulcus (area T3). These areas are known to have connections with the structures of the inner cortical vestibular circuit. Only a few efferent connections to the brainstem vestibular nuclei were found for the different parts of cytoarchitectonic area 7. Significant differences were found between the efferent innervation patterns of the axons originating in the six cortical areas mentioned and ending in the various compartments of the vestibular nuclear complex. Vestibular nuclei with a dominant output to the gaze motor system of the brainstem receive efferent connections preferably from the parietoinsular vestibular cortex. Vestibular structures with their primary output to skeletomotor centers, however, receive stronger efferent connections from areas 6pa and 3a. The ventrolateral nucleus, which sends efferent axons to both the oculomotor and skeletomotor systems of the brainstem and the spinal cord, also receives its main cortical efferents from the somatomotor area 6 and from area 3aV. Through these connections the cortical somatomotor system may directly influence vestibuloocular and vestibulocollic reflexes. It is speculated that the corticofugal connections to the vestibular brainstem nuclei are predominantly inhibitory, suppressing vestibular reflexes during cortically controlled goal‐directed movements. © 1994 Wiley‐L

ISSN:0092-7317    

DOI:10.1002/cne.903390309

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

年代:1994

数据来源: WILEY

摘要:

AbstractPrimary auditory nerve fibers were labelled in the barn owl by localized horseradish peroxidase (HRP) injections into the cochlear nucleus angularis. They were followed to their terminal sites in the hearing organ (basilar papilla), confirming that they were auditory, and to the cochlear nucleus magnocellularis. The terminal sites of low‐frequency fibers within nucleus magnocellularis always included an area previously described as the lagenar part, i.e., an area receiving primary input which is probably only vestibular. Furthermore, a number of differences were recognized between these low‐frequency (up to 0.64 kHz) and the high‐frequency (1.8 kHz and above) auditory nerve projections to nucleus magnocellularis. Most importantly, the collaterals given off by low‐frequency fibers into the nucleus typically showed multiple terminal branching, with both en passant and terminal bouton‐like swellings. High‐frequency fiber collaterals, in contrast, terminated unbranched in a single endbulb of Held. Nucleus magnocellularis is the first station in a brainstem auditory pathway processing stimulus timing information, coded through neuronal phase locking. The prominent difference in terminal shape found between its low‐ and high‐frequency input fibers is interpreted as reflecting different requirements of the absolute temporal precision for significant phase locking. Terminals in the shape of endbulbs of Held are probably a specialization to improve the temporal precision of synaptic transmission, allowing phase locking to higher frequencies. © 1994

ISSN:0092-7317    

DOI:10.1002/cne.903390310

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

年代:1994

数据来源: WILEY

摘要:

AbstractIt has been hypothesized that the corticotropin‐releasing hormone (CRH) neurons of the hypothalamic paraventricular nucleus (PVN) become hyperactive with age, and even more so in Alzheimer's disease. This hyperactivity could be due to an increased production of CRH per neuron, or an increased number of PVN neurons producing CRH, or both. As a first step in elucidating which of these biological mechanisms might be operative, we have estimated the absolute number of CRH immunoreactive neurons in the PVN of 10 human control subjects between 36 and 91 years of age and 10 Alzheimer patients between 40 and 97 years of age. CRH neurons were immunocytochemically detected in 6 μm paraffin sections with the aid of a highly specific monoclonal antibody to CRH. The antibody signal was amplified by the biotinstreptavidin and alkaline phosphatase methods. The absolute number of CRH neurons in the PVN was obtained by multiplying the number of CRH neurons in a unit volume (Nv) by the total volume of the PVN. Two different methods were used to estimate the Nv: an unfolding method and a disector method (about three times more time‐consuming). Compared to the disector, the unfolding method consistently yielded a lower cell number for all patients by 38% (± 2.8%; mean ± SEM). However, both methods yielded an increase in the absolute number of CRH neurons in control and Alzheimer patients with age. No statistically significant difference in the absolute number of CRH neurons was found between control and Alzheinler patients with both methods. The age‐dependent increase in the absolute number of CRH neurons within the PVN of both control and Alzheimer patients is interpreted as a sign of activation of the CRH neurons with age. © 1994 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903390311

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

年代:1994

数据来源: WILEY