摘要:

AbstractVisually responsive cortical areas and subcortical nuclei were studied in the awake cat using the 2‐deoxyglucose technique. Visual input was confined to one hemisphere by unilaterally sectioning the optic tract, the corpus callosum and the commissura anterior. Within the intact hemisphere, numerous cortical regions were distinguishable in the autoradiographs due to differential labelling. Comparison of the intact with the visually deafferented hemisphere confirmed the visual character of eighteen cortical areas (areas 17, 18, 19, 20a, 20b, 21a, 21b, the posteromedial lateral, posterolateral lateral, anteromedial lateral, anterolateral lateral, dorsal lateral, ventral lateral, and posterior suprasylvian areas, the splenial and anterior ectosylvian sylvian areas, insular visual area and posterior area 7) and revealed the visual nature of an area in the posterior cingulate gyrus which had not been described previously. We refer to this area as cingulate visual area (CVA). This area exhibits a gradient in interhemispheric differences along a caudorostral axis similar to that observed in posterior area 7 which is in keeping with the strong and topographic connections between CVA and posterior area 7. These results support the validity of metabolic mapping for the characterisation of cortical areas. © 1995 Wiley‐Liss,

ISSN:0092-7317    

DOI:10.1002/cne.903540202

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

年代:1995

数据来源: WILEY

摘要:

AbstractWe compared the central projections of retinal ganglion cells in temporal retina and the cortical representation of visual fields in areas 17 and 18 in cats with various hypopigmentation phenotypes (albino, heterozygous albino, Siamese, and heterozygous Siamese). In all cats studied, we found that the extent of abnormal ipsilateral visual field representation varied widely, and more of the ipsilateral visual field was represented in area 18 than in area 17. The greatest degree of ipsilateral visual field representation was found in albino cats, followed by Siamese, heterozygous albino and heterozygote Siamese cats, respectively. Additionally, in the different groups there was wide variation in the numbers of contralaterally projecting alpha and beta ganglion cells in temporal retina. In all cases, however, contralaterally projecting alpha cells were found to extend further into temporal retina than beta cells. We found that in each cat studied, the maximum extent of the abnormal ipsilateral visual field representation in areas 18 and 17 corresponded to the location of the 50% decussation line (i. e., the point where 50% of the ganglion cells in temporal retina project to the contralateral hemisphere) for alpha and beta cells, respectively, for that cat. Our results suggest that the extent of the abnormal visual field representations in visual cortex of hypopigmented cats reflects the extent of contralaterally projecting retinal ganglion cells in temporal retina. © 1995 Wiley‐Liss, I

ISSN:0092-7317    

DOI:10.1002/cne.903540203

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

年代:1995

数据来源: WILEY

摘要:

AbstractAxosomatic and axodendritic synapses occur on sympathetic preganglionic neurons, but it is not yet known whether their axons receive synaptic input, which could be particularly effective at regulating sympathetic outflow. Here, we examined retrogradely labelled sympathetic preganglionic axons to see if they received synapses. Cholera toxin B subunit (CTB) or CTB conjugated to horseradish peroxidase (CTB‐HRP) was used to label neurons projecting to the rat or rabbit superior cervical ganglion, the rat adrenal medulla, or the rabbit stellate ganglion. At the light microscopic level, small groups of CTB‐immunoreactive axons travelled through the ventral horn near its lateral boundary, with occasional axons taking a more medial course. The axons passed through the ventrolateral funiculus to exit at the ventral roots. In parasagittal section, a few axons branched within the ventral horn, sending processes rostrally and caudally for short distances before they turned ventrally to exit the spinal cord. At the ultrastructural level, CTB‐immunoreactive rat and rabbit sympathetic preganglionic axons were almost exclusively unmyelinated. In contrast, labelling with CTB‐HRP revealed both myelinated and unmyelinated axons in the ventral horn, the ventrolateral white matter, and the ventral roots. CTB‐HRP also allowed the detection of the initial segment of a sympathetic preganglionic axon. Synapses, with vesicles clustered presynaptically and membrane specializations postsynaptically, were found on some unmyelinated CTB‐immunoreactive axons. Occasional axons received several synapses. Synapses were most common on CTB‐containing axons just ventral to the intermediolateral cell column. One synapse was found on an axon within 2 μm of its origin from a proximal dendrite. Rare synapses were found several hundred micrometers ventral to the intermediolateral cell column. One branching axon had synapses just below the branch point on both the main axon and the axonal branch. These findings indicate an extensive synaptic input to the axons of at least some sympathetic preganglionic neurons. These axoaxonic synapses could have a profound effect on sympathetic activity. © 1995

ISSN:0092-7317    

DOI:10.1002/cne.903540204

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe origin, migration, and differentiation of microglial precursors in the avascular quail retina during embryonic and posthatching development were examined in this study. Microglial precursors and developing microglia were immunocytochemically labeled with QH1 antibody in retinal whole mounts and sections. The retina was free of QH1+macrophages at embryonic day 5 (E5). Ameboid QH1+macrophages from the pecten entered the retina from E7 on. These macrophages spread from central to peripheral areas in the retina by migrating on the endfeet of the Müller cells and reached the periphery of the retina at E12. While earlier macrophages were migrating along the inner limiting membrane, other macrophages continued to enter the retina from the pecten until hatching (E16). From E9 on, macrophages were seen to colonize progressively more scleral retinal layers as development advanced. Macrophages first appeared in the ganglion cell layer at E9, in the inner plexiform layer at E12, and in the outer plexiform layer at E 14. Therefore, it seems that macrophages first migrated tangentially along the inner retinal surface and then migrated from vitreal to scleral levels to gain access to the plexiform layers, where they differentiated into ramified microglia. Macrophages appeared to differentiate shortly after arrival in the plexiform layers, as poorly ramified QH1+cells were seen as early as E12 in the inner plexiform layer and at E14 in the outer plexiform layer. Radial migration of macrophages toward the outer plexiform layer continued until posthatching day 3, after which retinal microglia showed an adult distribution pattern. We also observed numerous vitreal macrophages intimately adhered to the surface of the pecten during embryonic development, when macrophages migrated into the retina. These vitreal macrophages were not seen from hatching onwards, when no further macrophages entered the retina. © 1995 Wiley‐Liss,

ISSN:0092-7317    

DOI:10.1002/cne.903540205

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

年代:1995

数据来源: WILEY

摘要:

AbstractFollowing peripheral trochlear nerve axotomy in the cat, the normal number of myelinated axons is restored despite significant motor neuron death, suggesting regulation of the number of myelinated axons in the regenerated nerve. In this study we used light and electron microscopy to examine the production and maintenance of axonal sprouts at different locations in the nerve and at different postoperative intervals. Despite proliferative sprouting and an overproduction of nonmyelinated axons in the regenerating trochlear nerve, the number of myelinated axons was strictly regulated. Only ∼1,000 regenerated axons were eventually remyelinated, but many nonmyelinated axons were still present 6–8 months postaxotomy. Regenerated axons were remyelinated in a proximal‐to‐distal direction between 3 and 4 weeks postaxotomy.We also examined the maturation of regenerated myelinated axons by measuring axon diameter and myelin index (an expression of myelin thickness). Mean myelinated axon diameter remained significantly below normal in long‐term regenerated nerves. Mean myelin index was not different from normal at 4 weeks postaxotomy but was significantly decreased at long postoperative intervals, reflecting a slightly thicker myelin sheath relative to the axon diameter. This relative increase in mean myehn thickness could serve to restore normal conduction velocity despite the decrease in mean axon diameter.We suggest that the regulation of the number of myelinated axons at the normal number despite cell death and the increase in mean myelin thickness may both be compensatory mechanisms that function to restore preoperative conditions and maximize functional recovery. © 1995 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903540206

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

年代:1995

数据来源: WILEY

摘要:

AbstractMetabotropic glutamate receptors (mGluRs) mediate the effects of glutamate neurotransmission on intracellular second messenger systems. Among the seven distinct mGluR receptor isoforms currently identified, the mGluR5 isoform is expressed particularly prominently in the striatum, where it may contribute to neuronal plasticity, motor behaviors, and excitotoxic injury. mGluR5 mRNA expression in striatal enkephalinergic, somatostatinergic, and cholinergic neurons was examined using double label in situ hybridization techniques. mGluR5 expression is abundant in a large number of medium‐sized striatal cells but is absent in a significant minority of neurons. Double label in situ hybridization with35S‐dATP‐ and digoxygenin‐dUTP‐tailed oligonucleotide probes demonstrated that mGluR5 message is highly expressed by enkephalinergic striatal neurons but is not detectable in cholinergic or somatostatin interneurons. In addition, some nonenkephalin, presumably substance P, neurons were also strongly labeled for mGluR5. The differential expression of mGluR5 in striatal projection neurons vs. interneurons may contribute to the selective vulnerability of these neurons to disease processes. © 1995 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903540207

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

年代:1995

数据来源: WILEY

摘要:

AbstractA number of neuroactive peptides including calcitonin gene‐related peptide (CGRP), substance P, neurokinin B, opioids, somatostatin (SRIF), galanin, neurotensin and vasoactive intestinal polypeptide (VIP) have been localized in adult rat spinal cord and are considered to participate either directly and/or indirectly in the processing of sensory, motor and autonomic functions. Most of these peptides appear early during development, leading to the suggestion that peptides, in addition to their neurotransmitter/neuromodulator roles, may possibly be involved in the normal growth and maturation of the spinal cord. To provide an anatomical substrate for a better understanding of the possible roles of peptides in the ontogenic development of the cord, we investigated the topographical profile as well as variation in densities of [125I]hCGRPα, [125I]substance P/neurokinin‐1 (NK‐1), [125I]eledoisin/neurokinin‐3 (NK‐3), [125I]FK 33–824 ([D‐Ala2, Me‐Phe4, Met(O)ol5]enkephalin)/μ‐opioid, [125I]galanin, [125I]T0D8‐SRIF14(an analog of sornatostatin), [125I]neurotensin and [125I]VIP binding sites in postnatal and adult rat spinal cord using in vitro quantitative receptor autoradiography. Receptor binding sites recognized by each radioligand are found to be distributed widely during early stages of postnatal development and then to undergo selective modification to attain their adult profile of distribution during the third week of postnatal development. The apparent density of various receptor sites, however, are differently regulated depending on the lamina and the stage of development studied. For example, the density of μ‐opioid binding sites, following a peak at postnatal day 4 (N), declines gradually in almost all regions of the spinal cord with the increasing age of the animal [125I]substance P/NK‐1 binding sites, on the other hand, show very little variation until P14 and then subsequently decrease as the development proceeds. In the adult rat, most of these peptide receptor binding sites are localized in relatively high amounts in the superficial laminae of the dorsal horn. To varying extents, moderate to low density of various peptide receptor binding sites are also found to be present in the ventral horn, intermediolateral cell column and around the central canal. Taken together, these results suggest that each receptor‐ligand system is regulated differently during development and may each uniquely be involved in cellular growth, differentiation and in maturation of the normal neural circuits of the spinal cord, Furthermore, the selective localization of various receptor binding sites in adult rat spinal cord over a wide variety of functionally distinct regions reinforces the neurotransmitter/ modulator roles of these peptides in sensory, motor and autonomic functions associated with the spinal

ISSN:0092-7317    

DOI:10.1002/cne.903540208

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe rhythmically active pyloric and gastric mill motor patterns in the stomatogastric ganglion of the crab,Cancer borealis, are influenced by modulatory projection neurons whose somata are located primarily in the other ganglia of the stomatogastric nervous system. One of these projection neurons exhibits substance P‐like immunolabeling. However, bath application of substance P does not influence these motor patterns. To determine whether a different peptide is responsible for the substance P‐like immunolabeling, we studied the presence and physiological effects of the locustatachykinins and the leucokinins, two families of tachykininlike peptides originally identified in insect nervous systems. Locustatachykinin‐hke immunolabeling has the same distribution in the stomatogastric nervous system as substance P‐like immunolabeling and colocalizes with it in the majority of immunopositive structures. Preincubation of locustatachykinin antibody with substance P, and preincubation of substance P antibody with locustatachykinin, blocks subsequent immunolabeling in the stomatogastric nervous system. In contrast, we found no leucokinin‐like immunolabeling in this system. Bath application to the stomatogastric ganglion of individual locustatachykinins or leucokinins excited the pyloric rhythm in a state‐dependent manner. Each peptide family had distinct effects on the pyloric rhythm. Thus, both of these tachykinin‐like peptide families are likely related to native neuropeptides that influence the pyloric rhythm. Furthermore, a member of the locustatachykinin family is likely to be the source of the previously identified substance P‐like immunoreactivity in the stomatogastric nervous system. © 1995

ISSN:0092-7317    

DOI:10.1002/cne.903540209

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

年代:1995

数据来源: WILEY

摘要:

AbstractExtensive regeneration of the optic nerve takes place in adult Amphibia. In this study, we have determined whether one aspect of retinotectal organisation, namely immunoreactive laminae in the retinorecipient layers of the optic tectum, is restored after optic nerve regeneration. To do so, the distributions of substance‐P, bombesin, and leucine‐enkephalin immunoreactivities were examined in the optic tectum of the frogLitoria (Hyla) moorei. Results of a normal series were compared with those at intervals up to 84 days and at 196 days after either unilateral deafferentation or optic nerve crush.In the normal series, distinct neuropeptide immunoreactive laminae were located within the retinorecipient tectal layers. There were two major laminae with substance‐P, two with bombesin, and one with leucine‐enkephalin immunoreactivities. Additional faint laminae of both substance‐P and bombesin immunoreactivity were present in the tectal region that receives input from the visual streak. In addition, labelling of cell bodies and dendrites was seen elsewhere in the tectum.All except one immunoreactive lamina changed after deafferentation. The deeper of those with substance‐P immunoreactivity, along with both bombesin laminae, were eventually lost the lamina with leucine‐enkephalin immunoreactivity was halved in intensity. We assume that these laminae are wholely or, in the case of the leucine‐enkephalin lamina, partially associated with primary optic input. By contrast, the more superficial lamina with substance‐P immunoreactivity remained unchanged and is presumably not directly related to visual input.During nerve regeneration, the intensity of all laminae associated with optic input initially fell as in the deafferentation series but, in the long term, recovered to approximately 80% of normal intensities. We conclude that ganglion cells associated with each of the immunoreactivities tested had successfully regenerated. The reduced intensity of immunoreactivities after regeneration is due presumably in part to the cell loss from the ganglion cell population.Furthermore, we discuss the findings of similar studies forRana pipiens(Kuljis and Karten [1983] J. Comp. Neurol. 217:239–251 and [1985]240:1–15) in light of the present findings. We argue that some of the previous observations can be reinterpreted to indicate that regeneration was not limited to ganglion cells associated with substance‐P immunoreactivity as first thought.

ISSN:0092-7317    

DOI:10.1002/cne.903540210

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

年代:1995

数据来源: WILEY

摘要:

AbstractSeveral matrix and adhesion molecules in fish optic nerve, which are constitutively expressed, are increased during axonal regeneration and are primarily associated with nonneuronal cells (W. P. Battisti, Y. Shinar, M. Schwartz, P. Levitt, and M. Murray [1992] J. Neurocytol. 21:557–573). The current study examines the reactions of specific cell types to optic nerve crush and axonal regeneration.The goldfish optic nerve contains macroglia and microglia as well as a population of monocyte‐derived cells (granular macrophages) unique to goldfish. Two cell types were OX‐42 positive (granular macrophages and microglia), indicating monocyte lineage, each with a distinct morphology and distribution within the nerve. Within hours of the optic nerve crush, the number of OX‐42‐labeled cell profiles increased near the crush site, remained elevated during the time axons were elongating, and then declined. Microglia, but not granular macrophages, were phagocytically active. Astrocytes are readily identified in the normal optic nerve, but they exhibited marked morphologic changes within hours of injury, which is consistent with the contribution these cells make to the altered environment. Oligodendroglia could not be reliably identified in regenerating optic nerves until myelin was formed.A comparison of the distribution of OX‐42‐labeled cells with that of transforming growth factor β‐1 (TGF‐β1) and tenascin suggests that these molecules are expressed by granular macrophages. Tenascin staining may be additionally associated with astrocytes and/or microglia. The rapid response of these nonneuronal cells to injury, their rapid phagocytic activity, and the secretion of growth‐promoting factors by these cells likely contributes to the environment that supports robust regeneration by optic axons in the goldfish.

ISSN:0092-7317    

DOI:10.1002/cne.903540211

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

年代:1995

数据来源: WILEY