摘要:

AbstractNeurons in the ventrolateral medulla oblongata, a brain region implicated in central vasomotor regulation, have previously been reported to project to some forebrain limbic structures. The aim of the present study was (1) to describe the termination pattern of ventral medullary afferents in forebrain limbic areas using anterograde tract tracing, and (2) to determine the location and some morphological characteristics of the projection neurons using retrograde tract tracing from selected forebrain sites.Following ionophoretic microinjections of the anterograde tract tracerPhaseolus vulgarisleucoagglutinin into the rostral ventrolateral medulla, labelled afferents were observed in the hippocampus, entorhinal and retrosplenial cortices, dorsal septum, nucleus accumbens, and the medial prefrontal cortex. Anterogradely labelled axons, ascending from the caudal ventrolateral medulla, could be traced only to the rostral aspects of the investigated forebrain limbic structures. Here, the main target of the ascending projection was in the ventral septum. However, labelled terminals were also present in the nucleus accumbens, the dorsolateral septum, and in the infralimbic cortex. The density of the ventrolateral medullary projections into all examined forebrain areas was low.The location of the cells in the ventral medulla oblongata which give rise to direct forebrain projections was examined using retrograde tract tracing with wheat germ agglutinin conjugated horseradish peroxidase (WGA‐HRP). Following WGA‐HRP injections into the septo‐accumbens region, retrogradely labelled cells were present in both the rostral and caudal ventrolateral medulla. When the tract tracer injection was restricted to the ventral region of the septal complex, the labelled cells were concentrated in the caudal aspects of the ventrolateral medulla (and the nucleus of the solitary tract). Following tracer injections into the anterior cingulate cortex or the hippocampus or the entorhinal cortex, retrogradely labelled cells in the medulla oblongata were predominantly in the rostral ventrolateral medulla.As a first attempt to reveal the chemical nature of the projection cells, the contribution of tyrosine hydroxylase‐immunoreactive cells to the innervation of the septo‐accumbens area was also investigated: tyrosine hydroxylase‐immunoreactive cells of both the caudal ventrolateral medulla and the nucleus of the solitary tract were found to contribute to the innervation of the septo‐accumbens area.The distribution of retrogradely labelled cells as well as the termination pattern of the anterogradely labelled terminals indicated that the innervation of the various forebrain limbic areas arises from cells, diffusely distributed in the rostral and/or the caudal ventrolateral medulla oblongata. Considering the important role of the ventrolateral medulla oblongata in autonomic coordination, it is proposed that direct projections from the ventral medulla oblongata to limbic forebrain structures might contribute to the coordination of behavioural states and cardiovascular performance. © W

ISSN:0092-7317    

DOI:10.1002/cne.903400402

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractCalcium/ calmodulin‐dependent protein kinase II is a prominent enzyme in the mammalian brain that phosphorylates a variety of substrate proteins. In the present study, monoclonal antibodies that specifically recognize either the α or the β isoforms of this enzyme were used to determine the distribution of these isoforms within the rat and monkey spinal cord. In the rat, the corticospinal tract consists of two components: the dorsal corticospinal tract, which occupies the ventralmost aspect of the dorsal funiculus; and the ventral corticospinal tract, which occupies an area adjacent to the ventral median fissure. Both dorsal and ventral corticospinal tract fibers were strongly immunopositive for the α‐antibody. Unilateral ablation of the sensorimotor cortex of the rat eliminated the α‐immunoreactive staining in the contralateral dorsal corticospinal tract. The neuropil in the superficial laminae of the dorsal horn (Rexed's laminae I and II) was densely stained with the α‐antibody, whereas the neuropil in laminae IV‐X was immunonegative. Dense α‐immunopositive neurons were also distributed in the head of the dorsal horn (laminae I‐IV). In contrast to the strong α‐immunoreactivity seen in the dorsal corticospinal tract fibers, only very weak β‐immunoreactivity was observed in this tract. Moderate β‐immunoreactive products were distributed homogenously throughout the neuropil of the gray matter, although the neuropil of the superficial laminae of the dorsal horn (laminae I and II) was stained more strongly than the other regions of the gray matter (laminae III‐X). Neuronal components in all laminae were immunopositive for the β‐antibody. Thus, motoneurons in the ventral horn, which were immunonegative for the α‐antibody, were immunopositive for the β‐antibody. This selective distribution pattern of immunoreactivity of α‐ and β‐antibodies in the rat was also present in the monkey spinal cord, although the α‐immunopositive corticospinal tract fibers in the monkey descended in the lateral funiculus as the lateral corticospinal tract instead of passing through the dorsal funiculus, as is the case in the rat. The differential distribution of immunoreactivity in the spinal cord suggests that these two isoforms of calcium/ calmodulin‐dependent protein kinase II may have different func

ISSN:0092-7317    

DOI:10.1002/cne.903400403

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractLateral line sensory receptors and their cranial nerves in axolotls arise from a dorsolateral series of placodes, including the octaval placode, that gives rise to the inner ear and the octaval nerve. Anterodorsal and anteroventral placodes occur rostral to the octaval placode and give rise to anterodorsal and anteroventral lateral line nerves and electroreceptors and mechanoreceptors of the snout, cheek, and lower jaw. Middle, supratemporal, and posterior placodes occur caudal to the octaval placode and give rise to similarly named lateral line nerves, electroreceptors and mechanoreceptors of the occipital region of the head, and trunk neuromasts.All placodes, except the posterior placode, elongate, forming sensory ridges, following the genesis of sensory ganglia. Primary mechanoreceptor primordia begin to form within the central zone of the sensory ridges at stage 36; primary electroreceptor primordia originate within the lateral zones of these ridges at stage 38. The first primary mechanoreceptors erunt during stage 37; all primary mechanoreceptors have erupted at hatching (stage 41). Primary electroreceptors begin to erupt at stage 43. Secondary mechanoreceptor primordia begin to form in 1‐week‐old larvae and erupt 1–2 weeks later. Secondary electroreceptor primordia also begin to form in 1‐week‐old larvae and continue until clusters of two to five electoreceptors are formed.The developmental stages thought to characterize lateral line placodes in the earliest gnathostomes suggest that this ancestral ontogeny has been truncated in modern amphibians, and ontogenetic mechanisms underlying placodal differentiation are suggested. © Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903400404

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractFungiform taste buds in mature hamsters are less subject to neurotrophic influences than those of other species. This study evaluates taste‐bud neurotrophism during development in hamsters by examining the relation between growing nerves and differentiating fungiform papillae. Chorda tympani (CT) or lingual (trigeminal) nerve (LN) fibers were labelled with Lucifer Yellow as they grew into (CT fibers) or around (LN fibers) developing taste buds. Developing fungiform papillae and taste pores were counted with the aid of a topical tongue stain.The tongue forms on embryonic days (E) 10.5–11 and contains deeply placed CT and LN fibers but no papillae. By E12, the tongue epithelium develops scattered elevations. These “eminences” selectively become innervated by LN fibers that grow to the epithelium earlier and in larger numbers than CT fibers. Definitive fungiform papillae form rapidly during E13–14 and become heavily innervated by LN fibers. Intraepithelial CT fibers, rare at E13, invariably innervate fungiform papillae containing nascent taste buds at E14. During E14–15 (birth = E15–16), most papillae contain taste buds with pores, extensive perigemmal LN innervation, and extensive intragemmal CT innervation. At birth, numbers of fungiform papillae and taste pores are adultlike.The results show that fungiform eminences begin forming in the absence of innervation. The subsequent differentiation of definitive fungiform papillae and their innervation by LN fibers occur synchronously, prior to the differentiation of taste buds and their CT innervation. The hamster is precocious (e.g., compared to rat) in terms of LN development and the structural maturity of the anterior tongue at birth. © W

ISSN:0092-7317    

DOI:10.1002/cne.903400405

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractPrevious observations indicate that spinocervical tract terminals contain relatively high levels of glutamate. To examine whether these high glutamate levels are likely to represent a neurotransmitter pool or an elevated metabolic pool, the distributions of glutamate‐ and glutamine‐like immunoreactivities were examined in adjacent immunogold‐labeled sections of the lateral cervical nucleus. Spinocervical tract terminals were identified by anterograde transport of horseradish peroxidase and wheat germ agglutinin‐horseradish peroxidase conjugate from the spinal cord.Spinocervical tract terminals were found to contain significantly higher levels of glutamate‐like immunoreactivity than other examined tissue compartments (large neuronal cell bodies, terminals with pleomorphic vesicles, astrocytes, and average tissue level). In contrast, the highest levels of glutamine‐like immunoreactivity were detected in astrocytes. The different analyzed tissue elements formed three groups with respect to glutamate: glutamine ratios: one high ratio group including spinocervical tract terminals, a second group with intermediate ratios consisting of neuronal cell bodies and terminals containing pleomorphic synaptic vesicles, and a third low ratio group including astrocytes.Our findings indicate the presence of a compartmentation of glutamate and glutamine in the lateral cervical nucleus, similar to that postulated in biochemical studies of the central nervous system. The results also show that spinocervical tract terminals have high glutamate: glutamine ratios, similar to those previously observed in putative glutamatergic terminals in the cerebellar cortex. Thus, spinocervical tract terminals display biochemical characteristics that would be expected of glutamatergic terminals and the present findings therefore provide further evidence for glutamate as a spinocervical tract neurotransmitter. © Wil

ISSN:0092-7317    

DOI:10.1002/cne.903400406

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractIn the cat, serotoninergic (5HT) axons and terminals form a dense plexus that is present throughout the granule cell and Purkinje cell layers of the cerebellar cortex and all of the cerebellar nuclei. The intent of the present study was to identify the source of 5HT fibers in the cerebellar nuclei. The medial, interposed, and lateral cerebellar nuclei were selectively injected with either rhodamine or fluorescein‐labeled latex microspheres that were retrogradely transported to brainstem neurons. Transverse sections of the brainstem were processed with a primary antibody to 5HT and secondary antibody tagged with either rhodamine or fluorescein. The location of neurons containing both serotonin‐like immunoreactivity and retrogradely transported microspheres was plotted. All three of the cerebellar nuclei receive 5HT afferents from the nucleus locus coeruleus, the dorsal raphe nucleus, and the dorsal tegmental nucleus. In addition, the medial nucleus receives projections from the superior central nucleus, the nucleus raphe obscurus, the nucleus raphe magnus, and the periolivary reticular formation. The interposed nuclei receive additional projections from the nucleus raphe magnus, whereas the lateral nucleus receives additional projections from the superior central nucleus. In conclusion, the 5HT projections to the cerebellar nuclei do not appear to be collaterals of those projecting to the cortex (Kerr and Bishop, J Comp Neurol 304:502–515, 1991). These findings suggest that, although the cortex and nuclei are anatomically and physiologically related, they do not process all information in parallel. © Wiley‐L

ISSN:0092-7317    

DOI:10.1002/cne.903400407

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractExcitatory input regulates cell birth and survival in many systems. The granule cell population of the rat dentate gyrus is formed primarily during the postnatal period. Excitatory afferents enter the dentate gyrus and begin to form synapses with granule cells during the first postnatal week, the time of maximal cell birth and death. In order to determine whether excitatory input plays a role in the regulation of cell birth and survival in the developing granule cell layers and their germinal regions, the subependymal layer and hilus, we treated rat pups with the N‐methyl D‐aspartate (NMDA) receptor antagonists MK‐801, CGP 37849, or CGP 43487 during the first postnatal week and examined the numbers of3H‐thymidine‐labeled cells, pyknotic cells, and healthy cells in these regions. In order to determine the cell type that was affected, sections from brains of MK‐801‐treated rats were processed for3H‐thymidine autoradiography combined with immunohistochemistry for the marker of radial glia, vimentin, and the marker of mature astrocytes, glial fibrillary acidic protein (GFAP).Within the dentate gyrus, NMDA receptor blockade resulted in the following changes: (1) the density of3H‐thymidine‐labeled cells was increased, (2) the density of pyknotic cells was increased, (3) the density of3H‐thymidine‐labeled pyknotic cells was increased, and (4) the density of healthy cells was decreased. The infrapyramidal blade/hilus showed changes throughout its extent, whereas the suprapyramidal blade showed changes only at the rostral level. No change in the numbers of3H‐thymidine‐labeled vimentin‐immunoreactive or GFAP‐immunoreactive cells was observed in the dentate gyrus with MK‐801 treatment, indicating that glia are not primarily affected by NMDA receptor blockade.Blockade of NMDA receptors resulted in gross morphologic changes in the dentate gyrus; in most cases, the infrapyramidal blade was indistinguishable from the hilus. Moreover, in several brains of animals treated with CGP 37849 or CGP 43487 on postnatal day (P)5, an abnormal aggregation of cells was observed ventral to the normal location of the infrapyramidal blade. This cellular cluster contained many pyknotic and3H‐thymidine‐labeled cells and may represent cells that normally comprise the infrapyramidal blade. Dramatic changes to the subependymal layer were also seen following NMDA receptor blockade. The cross‐sectional area of this region was significantly increased with MK‐801, CGP 37849, or CGP 43487 treatment and contained a high density of3H‐thymidine‐labeled cells and3H‐thymidine‐labeled pyknotic cells.These results indicate that NMDA receptor activation is critical for the normal development of the rat dentate gyrus. The finding that blockade of NMDA receptors resulted in increased levels of cell death and birth supports the hypothesis that NMDA receptor activation is a natural signal for the inhibition of these processes i

ISSN:0092-7317    

DOI:10.1002/cne.903400408

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe function of different vascular beds in the rat eye and brain was evaluated by measuring the transfer of a vascular tracer,14C‐α‐amino‐isobutyric acid, from blood to tissue. The density of vascular pores was measured in electron micrographs of perfusion‐fixed, age‐matched tissue to determine whether the differences in tracer transfer were paralleled by differences in ultrastructure. Tracer transfer in retina was approximately four times that in brain of the same animal. The transfer constant was not changed by the inclusion of cold α‐amino‐isobutyric acid, showing that transport across retinal vessels is not saturable, and indicating that, as in brain, transport is due to passive diffusion. Ultrastructurally, retinal vessels have a higher density of interendothelial junctions and of endothelial vesicles, both of which suggest higher vascular permeability. However, pericytes, which contribute to a second line of defence in the blood‐brain barrier, are approximately four times as numerous in retina as in brain, and we suggest that in the retina, they act to compensate for a more permeable endothelial barrier. Ciliary body vessels had a high transfer of tracer, probably as a consequence of the fenestrations in their walls. Iridial vessels had a relatively low transfer of tracer, similar to that in retina even though a proportion of the interendothelial junctions in iridial vessels had expanded junctional clefts suggestive of open paracellular channels. However, both iris and ciliary body may lose tracer to the anterior chamber fluid, leading us to underestimate the vascular permeability in these sites.

ISSN:0092-7317    

DOI:10.1002/cne.903400409

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractLocalization of preganglionic neurons of the accessory ciliary ganglion (ACG), including ectopic intraocular ganglion cells, was investigated in the cat with the aid of horseradish peroxidase (HRP) and HRP‐conjugated wheat germ agglutinin (WGA‐HRP) methods. When HRP or WGA‐HRP was injected into the anterior and posterior chambers of the eye, no retrogradely labeled cells were found in the visceral oculomotor nuclei, although most neurons of the ACG and the main ciliary ganglion (CG) were intensely labeled. When a microsyringe needle was inserted into the ciliary body, the tracer diffused into the suprachoroid lamina and the intraocular ganglion cells, and a small number of labeled neurons appeared in the midplane between each side of the somatic oculomotor nuclei. After injection into the ACG, many labeled neurons were observed in the anteromedian nucleus, Edinger‐Westphal nucleus, and midplane between the somatic oculomotor nuclei, their ventral continuations of the ventral tegmental area, and the periaqueductal gray. HRP /WGA‐HRP injection into the CG labeled cells in all these areas and in the lateral border zones of the anteromedian, Edinger‐Westphal and somatic oculomotor nuclei, and their ventral continuations of the ventral tegmental area. These findings indicate that the visceral oculomotor neurons which project to the ACG tend to be located more medially than those to the CG. © Wil

ISSN:0092-7317    

DOI:10.1002/cne.903400410

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.903400401

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY