摘要:

AbstractIn order to investigate the possible routes linking the thalamus in the two sides of the brain, the connections of the reticular nucleus (RT), the major component of the ventral thalamus, with contralateral dorsal thalamic nuclei were systematically investigated in the adult rat. This study was performed with several tract‐tracing techniques: single and double retrograde labeling with fluorescent tracers, and anterograde tracing with biocytin. Retrograde tracing was also combined with immunocytochemistry to provide additional criteria for the identification of labeled RT neurons.The data obtained with the retrograde transport of one fluorescent tracer showed that RT neurons project to contralateral dorsal thalamic domains. In particular, retrograde labeling findings indicated that the anterior intralaminar nuclei, as well as the ventromedial (VM) nucleus, are preferential targets of the contralateral RT projections. Commissural neurons were concentrated in two portions of RT: its rostral part, including the rostral pole, which projects to the contralateral central lateral (CL) and paracentral (Pc) nuclei, and the ventromedial sector of the middle third of RT, which projects to the contralateral VM and posterior part of CL and Pc. The double retrograde labeling study of the bilateral RT–intralaminar connection indicated that at least part of the commissural RT cells bifurcate bilaterally to symmetrical portions of the anterior intralaminar nuclei.The targets of the RT commissural system inferred from the retrograde labeling data were largely confirmed by anterograde tracing. Moreover, it was shown that RT fibers cross the midline in the intrathalamic commissure.The present data demonstrate that bilateral RT connections with the dorsal thalamus provide a channel for interthalamic crosstalk. Through these bilateral connections with thalamic VM and intralaminar neurons, RT could influence the activity of wide territories of the cerebral cortex and basal ganglia of both hemispheres. © 1993 Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903320202

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe premotor effects of intersegmental ascending interneurones upon uropod motor neurones in the crayfishProcambarus clarkii(Girard) are examined with intracellular recording and staining techniques. We show that many ascending interneurones can affect the activity of the antagonistic opener and closer motor neurones in the terminal ganglion. Based upon soma position, ascending interneurones are divided into three groups of rostral, medial, and caudal interneurones. Twenty‐four ascending interneurones are characterized physiologically according to their inputs from the tailfan and their output effects on the uropod motor neurones of both sides. Each interneurone is identifiable as a unique individual by means of overall shape, soma position, number of main branches, the commissure in which primary neurites cross the midline, axon position in the 5th–6th abdominal connective and physiological responses. They are classified into six classes; coactivating, coinhibiting, reciprocally closing, reciprocally opening, variably effective, and not effective interneurones, according to their premotor effects on the uropod motor neurones. These ascending interneurones seem to act as multifunctional units conveying sensory information from the tailfan to the anterior abdominal ganglia and, at the same time, influencing the uropod motor pattern in the terminal abdominal ganglion. © 1993 Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903320203

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe corticostriatal connections of the parietal association cortices were examined by the autoradiographic technique in rhesus monkeys. The results show that the rostral portion of the superior parietal lobule projects predominantly to the dorsal portion of the putamen, whereas the caudal portion of the superior parietal lobule and the cortex of the upper bank of the intraparietal sulcus have connections with the caudate nucleus as well as with the dorsal portion of the putamen. The medial parietal convexity cortex projects strongly to the caudate nucleus, and has less extensive projections to the putamen. In contrast, the medial parietal cortex within the caudal portion of the cingulate sulcus projects predominantly to the dorsal portion of the putamen, and has only minor connections with the caudate nucleus. The rostral portion of the inferior parietal lobule projects mainly to the ventral sector of the putamen, and has only minor connections with the caudate nucleus. The middle portion of the inferior parietal lobule has sizable projections to both the putamen and the caudate nucleus. The caudal portion of the inferior parietal lobule as well as the lower bank of the intraparietal sulcus project predominantly to the caudate nucleus, and have relatively minor connections with the putamen. The cortex of the parietal opercular region also shows a specific pattern of corticostriatal projections. Whereas the rostral portion projects exclusively to the ventral sector of the putamen, the caudal portion has connections to the caudate nucleus as well. Thus, it seems that parietostriatal projections show a differential topographic distribution; within both the superior and the inferior parietal region, as one progresses from rostral to caudal, there is a corresponding shift in the predominance of projections from the putamen to the caudate nucleus. In addition, with regard to the projections to the putamen, the superior parietal lobule is related mainly to the dorsal portion, and the inferior parietal lobule to the ventral portion. The striatal projections of the cortex of the caudal portion of the cingulate gyrus (corresponding in part to the supplementary sensory area) and of the rostral parietal opercular region (corresponding in part to the second somatosensory area) are directed almost exclusively to the dorsal and ventral sectors of the putamen, respectively. This pattern resembles that of the primary somatosensory cortex. The results are discussed with regard to the overall architectonic organization of the posterior parietal region. Possible functional aspects of parietostriatal connectivity are considered in the light of physiological and behavioral studies. © 1993 Wiley‐Liss, I

ISSN:0092-7317    

DOI:10.1002/cne.903320204

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractIn the adult spinal cord, immunocytochemical staining for NT75 is concentrated in nerve terminals in the superficial laminae of the dorsal horn. Deeper laminae of the dorsal horn contain moderate immunocytochemical labeling, but the ventral horn is only sparsely stained. The origin of spinal nerve terminals containing NT75 was investigated with lesion techniques, colchicine treatment, and retrograde tracing in combination with immunocytochemical staining. Primary afferent neurons express NT75 immunoreactivity and account for most of the dense staining in the superficial dorsal horn and part of the labeling in the deeper laminae. It was found that corticospinal and virtually all brainstem neurons with descending projections to the spinal cord also express NT75 immunoreactivity, including those terminating in the ventral horn. Colchicine treatment of the spinal cord also resulted in NT75 staining in most, if not all, spinal neurons. It appears that neurons in all three major sources of spinal afferents (primary sensory, descending, and intrinsic systems) can express NT75 immunoreactivity, but that some neurons normally contain higher levels of the protein in their nerve terminals. Previous analysis of developing spinal cord has shown widespread, dense NT75 labeling throughout the spinal gray in the early postnatal period, which later becomes restricted to the adult pattern. These studies support the hypothesis that many spinal pathways express high levels of NT75 immunoreactivity during development, but that only certain pathways maintain high levels in the adult. © 1993 Wiley‐Liss, I

ISSN:0092-7317    

DOI:10.1002/cne.903320205

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractOne of the most persistent problems in the study of the superior colliculus is the relationship between its superficial and deep layers. The superficial tier of layers is considered to be visuosensory in function, whereas the deep tier is multisensory and has premotor functions. This fundamental distinction is the primary basis for the view that a visually triggered shift in the direction of gaze depends on the transfer of information from sensory cells in the superficial tier to premotor cells in the deep tier. The goal of the present experiments was to examine the interalaminar projections of the superficial gray layer in the tree shrewTupaia belangeri. We used biocytin as the marker for tracing the pathways. The tree shrew was chosen because its large and distinctly laminated superior colliculus facilitates the task of examining connections between the layers. Biocytin was used because of its sensitivity and because it allowed us to place very small injections restricted entirely to the superficial gray layer. The results demonstrated that a prominent pathway originates in the superficial gray layer and terminates in stratum opticum. In comparison, the projection from the superficial gray layer to the layers beneath stratum opticum is extremely sparse. The pathway from the superficial gray layer to stratum opticum has a columnar distribution, extending about 100 m̈m rostrally and caudally from the center of the injection site. There were no signs of more remote intracollicular connections, nor of patches or bands of terminals. The biocytin injection sites also labeled pathways to nuclei as distant from the superior colliculus as the diencephalon, including the dorsal and ventral lateral geniculate bodies, and the pulvinar. The results suggest that stratum opticum may serve as a link between the superficial gray layer and the deeper layers. © 1993 Wiley‐Liss,

ISSN:0092-7317    

DOI:10.1002/cne.903320206

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe present study compared the ultrastructural morphology of enkephalin‐immunoreactive boutons and their postsynaptic targets in different territories of the nucleus accumbens in the rat. The synaptic bouton profiles were identified by antibodies directed against [leu5]enkephalin. Ninety‐five percent of the synaptic contacts were symmetric in configuration and the remaining 5% were asymmetric. Axosomatic contacts comprised 6% of all enkephalin‐immunoreactive junctions and were distributed equally in all parts of the nucleus. Most (76%) synaptic terminals contacted dendrites but they contacted proportionally fewer dendrites in the shell (71%) than in the core (78%). Moreover, enkephalin‐immunoreactive synaptic boutons in the shell (19%) and caudal enkephalin‐rich areas (17%) of the core contacted twice as many spines than in the remaining parts of the core (8.5%). In the core, long pallidum‐like dendrites were occasionally found ensheathed in enkephalin‐immunoreactive terminal boutons.We conclude that the differential arrangement of enkephalinergic contacts in the shell and core could have important functional consequences, especially when considered in relation to other known morphological and neurochemical differences between these regions. © 1993 W

ISSN:0092-7317    

DOI:10.1002/cne.903320207

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe neuron adhesion molecules NILE/L1 and NCAM may be involved in axonal guidance and cell recognition. To investigate all exposed membrane domains of single neurons, something which has not previously been done for any adhesion molecule, we used digitally processed scanning electron microscopy with a high‐energy backscatter electron detector. This allowed a quantitative analysis of immunogold staining densities on all surfaces of isolated rat hippocampal neurons in culture to study NILE/L1 and NCAM expression independent of potentially inductive innervation.During early stages of neuritic extension, all growth cones showed similar NILE/L1 expression, but as soon as a single process extended farther than the others (by 20 hours), this putative axon and its growth cone generally showed a stronger level of NILE/L1 immunogold labeling than the other neurites. This is the earliest evidence of plasma membrane differentiation between axons and dendrites. With further neuritic growth, the relative NILE/L1 expression on axons and their growth cones continued to increase. In contrast to some earlier reports, NILE/L1 was expressed on axonal growth cones growing on both polylysine‐coated glass and astrocyte substrates.Strong immunostaining for NCAM‐related polysialic acid (PSA) was found on axonal growth cones and filopodia, suggesting that the homophilic adhesive action of NCAM may be reduced during axonal growth. PSA showed greater labeling on distal axons than on other areas of the neuron, indicating a variable NCAM‐mediated adhesion on different regions of the same cell. Neither NILE/L1, NCAM, nor PSA appeared to show regional differences in axons fasciculating or defasciculating on themselves. A strong intercellular heterogeneity of NILE/L1, NCAM, and PSA expression levels on neurons in the same culture dish was found, suggesting that subsets of cells from the hippocampus may express biologically relevant differences in adhesion molecules compared to neighboring neurons.In light of the growing body of evidence pointing to the multifaceted array of homophilic and heterophilic binding interactions that NILE/L1 and NCAM may exhibit, and the functional importance of molecular densities, the quantitative data here support the hypothesis that sufficient cellular and subcellular heterogeneity exists for these molecules to be involved in some aspects of axonal guidance. © 1993 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903320208

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe goal of the present study was to investigate aspects of the central organization of the neurons belonging to the octavolateralis efferent system of amphibians. The perikarya of three genera,Pleurodeles, Xenopus, andDiscoglossus, were located in the brainstem by applying retrograde to the appropriate cranial nerves and choline acetyltransferase immunohistochemistry was used to identify cholinergic neurons.The efferent neurons supplying lateral line (Pleurodeles, Xenopus) and labyrinthine (Pleurodeles, Xenopus, andDiscoglossus) end organs were found to intermingle in a single octavolateralis efferent nucleus. The neurons lie bilateral to the labelled nerves inPleurodelesand ipsilateral inXenopusandDiscoglossus. Separate labelling of the anterior and posterior octavus rami provided no evidence for distinct groupings of efferent neurons that could be associated with auditory and vestibular end organs. In all three species many if not all octavolateral efferent neurons displayed immunoreactivity for choline acetyltransferase. They could be distinguished from the cholinergic facial motoneurons, with which they sometimes intermingle, on the basis of either their distinctive size and shape (Pleurodeles, Xenopus) or their location (Discoglossus). Double labelling inXenopusconfirmed the cholinergic nature of the efferent neurons. © 1993 Wiley‐Liss, I

ISSN:0092-7317    

DOI:10.1002/cne.903320209

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.903320201

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY