摘要:

AbstractThe morphology and physiology of small multimodal ocellar interneurons (SM‐neurons) have been examined in the cockroachPeriplaneta americana.The SM‐neuron is monopolar with its cell body in the tritocerebrum near the esophagus. In axon ascends to the protocerebrum and extends into the ocellar neuropil through the ocellar tract and the ocellar nerve. The axon sends a long collateral process towards the optic tract. The SM‐neuron responded with spike discharges to various sensory stimuli. The collateral and many side branches along the axon in the deutocerebrum appear to be input regions from those sensory afferents. Cereal stimulation triggered most effectively a train of spikes in the SM‐neuron: some of seven giant axons in the ventral nerve cord were involved in this pathway. Cereal stimulation also evoked depolarization in the large second order ocellar neurons (L‐neurons). A possible neural connection between SM‐neurons and L‐neurons was examined pharmacologically. Interaction of ocellar illumination and cereal stimulation in the L‐neuron was also examined. These data are discussed in relation to the ocellar function of cockroaches and in comparison with data obtained i

ISSN:0092-7317    

DOI:10.1002/cne.903010402

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

年代:1990

数据来源: WILEY

摘要:

AbstractIn the present study two types of descending ocellar neurons have been morphologically and physiologically identified in the cockroachPeriplaneta americana: a descending ipsilateral ocellar neuron (DIO‐neuron) and a descending contralateral ocellar neuron (DCO‐neuron). Both DIO‐and DCO‐neurons possess a cell body near the ocellar tract in the protocerebrum and extend dendritic processes into the ipsilateral ocellar nerve. An axon of the DIO‐neuron descends to the metathoracic ganglion, and its entire course is ipsilateral to the cell body. An axon of the DCO‐neuron crosses the median plane of the protocerebrum and descends through the contralateral ventral nerve cord to the second abdominal ganglion. Both axons possess masses of branches in each ganglion as well as in the brain. Both DIO‐and DCO‐neurons showed no spontaneous spike discharges, and responded with a few off‐spikes to ocellar illumination. They responded to various mechanical stimuli, like cereal stimulation with a train of spikes which was suppressed by ocellar illumination. Spikes of DCO‐neurons caused postsynaptic potentials and spikes in some interganglionic metathoracic interneurons, and spikes in motor nerves. These data are discussed in relation to the ocellar function of the cockroach as well as in comparison with th

ISSN:0092-7317    

DOI:10.1002/cne.903010403

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

年代:1990

数据来源: WILEY

摘要:

AbstractMany neurotransplantation studies have dealt with the ability of solid fetal spinal grafts to develop in the previously traumatized spinal cord of a host. In neurodegenerative spinal diseases, however, motoneuronal death occurs in the absence of a trauma, i.e., in the absence of axotomy of afferent fibers. Lesioning the spinal cord with an excitotoxic agent may provide a useful neurodegenerative model. The present study has been undertaken to determine whether homotypic fetal neurons transplanted as a cell suspension are able to rebuild a neural circuitry. Emphasis is given here to the analysis of the development of transplanted motoneurons and host‐graft connectivity.The lesion was made by kainic acid on the right side of the lumbar enlargement 1 week before transplantation. The fetal spinal cords were taken from rat embryos (gestational day E12‐13) and transplanted as cell suspensions.Light‐ and electron‐microscopic analysis demonstrated that the excitotoxic lesion extended over the entire spinal segment and was confined primarily to the ventral and intermediate horns, implying the death of all motoneurons with consequent paralysis and muscular atrophy of corresponding hindlimb. The lesion was characterized by a lack of neurons, glial proliferation, and sparing of fibers of passage and afferents.Two to fourteen months after surgery, the transplants were generally large, occupying most of the neuron‐depleted area. The boundaries between the transplant and host tissue were clearly delineated by the higher cellular density of the graft and the particular cytoarchitecture, i.e., the cell suspension grafts did not display a laminar organization. Among the different neuronal populations within the transplant, one resembled motoneurons: large, typically Nissl‐stained and immunoreactive for calcitonin gene‐related peptide (CGRP). No grafted neuron, however, extended an axon into the host ventral roots.Monoaminergic afferents from the host were studied using immunostaining for serotonin, noradrenaline, and tyrosine hydroxylase. These afferent fibers, thin and varicose, grew for a long distance and formed a network within transplants. Similarly, primary sensory CGRP‐immunoreactive fibers (entering the graft from the dorsal host‐graft interface) penetrated deeply into transplants. The response of cortico‐and rubro‐spinal afferents to the implantation of fetal tissue was different. After injection of WGA‐HRP, a few anterogradely labeled cortical and rubral fibers entered only the most peripheral portion of transplants.In conclusion, our results indicate that fetal spinal neurons can be successfully transplanted into the adult neuron‐depleted spinal cord. Host‐to‐graft connections can be formed, although their spatial extent in the transplants may depend upon structural features of the afferent fiber systems. In contrast, axonal growth of transplanted neurons into the depopulated ventral roots was not observed. Such a failure may be due to the nonpermissive substrate formed by mature oligodendrocytes and myel

ISSN:0092-7317    

DOI:10.1002/cne.903010404

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

年代:1990

数据来源: WILEY

摘要:

AbstractWe utilized3H‐8‐hydroxy‐N,N‐dipropyl‐2‐aminotetralin (3H‐DPAT) and125I‐iodocyanopindolol (125I‐CYP) to label serotonin (5HT) 1A and 5HT1B receptors, respectively, in sections of the rat brain after characterizing the pharmacologic specificity of these agents. We then used quantitative autoradiography to measure the concentrations of 5HT1A and 5HT1B receptors in individual subnuclei of the nucleus of the solitary tract (NTS) and adjacent structures of the dorsal vagal complex. The highest 5HT1A receptor concentrations were observed within the central and intermediate subnuclei of the NTS, with low quantities of3H‐DPAT binding sites observed in the hypoglossal nucleus and dorsal motor nucleus of the vagus. In contrast, the density of 5HT1B receptors was relatively homogeneous through all NTS subnuclei, with the highest concentrations localized within the ventrolateral subnucleus. The hypoglossal and dorsal motor nuclei had slightly higher 5HT1B receptor densities than the NTS subnuclei, whereas the area postrema had a very low density. These data suggest that 5HT1A receptors are organized in a manner consistent with the cytoarchitectural and hodological parcellation of the NTS into individual subnuclei. The high concentrations of 5HT1A receptors in the central and intermediate subnuclei suggest a role for these receptors in medullary reflex pathways subserving deglutition. The relatively high density of 5HT1B receptors in the ventrolateral subnucleus suggests that these receptors modulate respiratory neurons, whereas the diffuse organization of 5HT1B receptors in the remaining subnuclei suggests that they are associated with central 5HT afferent pathways to the NTS. Further studies will be required to understand the physiologic role of 5HT1 recep

ISSN:0092-7317    

DOI:10.1002/cne.903010405

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe solitary nuclear complex (NST) consists of a number of subdivisions that differ in their cytoarchitectonic features as well as in the amounts of inputs they receive from lingual afferent axons. In this study horseradish peroxidase (HRP) was injected into the parabrachial nucleus (PBN) of the hamster to determine which of these subdivisions contain cells that project to the pons. In the rostral, gustatory division of the NST, the rostral central subdivision contains the greatest number of labelled pontine‐projection neurons. The rostral lateral subdivision contains moderate numbers of labelled cells; progressively fewer labelled cells are in the ventral, medial, and dorsal subdivisions. In the caudal, general viscerosensory division of the NST, the caudal central subdivision contains the majority of labelled cells, although fewer than its rostral counterpart. Progressively fewer cells are labelled in the medial, laminar, ventrolateral, and lateral subdivisions; none in the dorsolateral subdivision. Small horseradish peroxidase injections into the pons revealed that cells of the rostral central and rostral lateral subdivisions of the NST project to the medial subdivision of the PBN, predominantly to caudal and ventral parts of the subdivision. Cells of the caudal central and medial subdivisions of the NST project to the central lateral subdivision of the PBN, predominantly to intermediate and rostral‐dorsal parts of the subdivision. Outside the NST, cells in the spinal trigeminal nucleus and parvicellular reticular formation were also labelled after PBN injections.Within the rostral central and rostral lateral (gustatory) subdivisions of the NST at least two types of neurons, distinguished on the basis of dendritic and cell body morphology, were labelled after HRP injections that included the medial PBN. Elongate cells have ovoid‐fusiform somata and dendrites oriented in the mediolateral plane parallel to primary afferent axons entering from the solitary tract. Stellate cells have triangular or polygonal cell bodies and three to five dendrites oriented in all directions, although one or two often extend mediolaterally.These results indicate that cytoarchitectonic subdivisions of the NST are distinguished by their efferent ascending connections. For each subdivision within the rostral, gustatory NST there is a correlation between the density of lingual inputs it receives and the density of pontine‐projection neurons it contains. Within the rostral central subdivision, which contains the densest lingual inputs and the largest collection of PBN‐projection neurons, cell types previously identified in studies with the Golgi method were found to send their axons to the PBN. The presence of two types of pontine‐projection cells in the rostral central subdivision provides a structural basis for parallel information processing in the ascending gustatory system. Projections to the PBN from regions outside the NST provide opportunities for convergence, at the level of the pons, between inputs arising from gustatory/general viscerosensory subdivisions of the NST and from trigeminal sensory nuclei and the reticula

ISSN:0092-7317    

DOI:10.1002/cne.903010406

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe cerebellar cortex contains five major classes of neurons that can be differentiated from one another on the basis of their location, size, shape, and, in some cases, molecular characteristics. The cerebellar cortex also contains other, less numerous neuronal types, including the Lugaro cell, which has been described on only a few occasions. The Lugaro cell is a relative rare cell type and is characterized by a fusiform cell body with thick, horizontally oriented dendrites. It is located in or slightly below the Purkinje cell layer. Because the Lugaro cell shares some morphological characteristics with the other large granular layer neurons, it often has been classified as a Golgi cell.In the present study we have taken advantage of differences in the molecular properties of neurons and have used monoclonal antibodies to identify and classify the Lugaro cell. Three large neuronal types in the cerebellar cortex were examined with cell‐type‐specific antibodies: Cat‐301 and Cat‐304 for Lugaro cells; Rat‐303 for Golgi cells; and anti‐calbindin for Purkinje cells. Double label immunocytochemistry on sections of the cat cerebellum was performed with subclass‐ or species‐specific secondary antibodies. Each of the three antibodies was selective for one of the three large neuron classes. Cat‐301 and Cat‐304 recognized Lugaro cells but not Golgi or Purkinje cells.Our results demonstrate that the Lugaro cells are molecularly, as well as morphologically, distinct from Purkinje and Golgi cells and thus constitute a distinct cell type in th

ISSN:0092-7317    

DOI:10.1002/cne.903010407

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

年代:1990

数据来源: WILEY

摘要:

AbstractIn normal development, cell layers in the dorsal lateral geniculate nucleus (dLGN) segregate from a relatively homogeneous cell group. If all retinal input is removed prior to this segregation, the layers fail to form. In the present study, we used ultrastructural and morphometric analyses to study dLGN development in the tree shrew following neonatal removal of retinal input. The goal of the present study was to determine whether there are differences between normal animals and enucleates in the development of dLGN cells and their interrelationships with each other and/or with the surrounding glia, which might explain the failure of cellular lamination in enucleated animals. The results indicate that although the development in enucleated animals may take place somewhat more slowly, by P90 cell size and density are not significantly different from normal. These results, coupled with the observation that the dLGN in enucleates is smaller than in normals, suggest that the removal of retinal input results in dLGN cell loss. At both the light and electron microscopic level, cells in the developing normal dLGN are arranged in bands of immediately adjacent cells. In enucleates, dLGN cells are less frequently in immediate contact and are arranged in small groups or clumps which may be separated by degenerating cells. The present data suggest that the presence of retinal input may be necessary to allow dLGN cells to maintain the intercellular relationships necessary for laminar segregation to take place.

ISSN:0092-7317    

DOI:10.1002/cne.903010408

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

年代:1990

数据来源: WILEY

摘要:

AbstractIntracellular recording and labelling with Lucifer yellow of respiratory neurons in the rostral ventrolateral medulla were carried out in urethane‐anaesthetised rats. A combined immunofluorescence and immunoperoxidase technique enabled an assessment of the tyrosine hydroxylase immunoreactivity, as well as an examination of the morphology of inspiratory and expiratory neurons in this part of the medulla oblongata. The results demonstrate: (a) that respiratory neurons in the rostral ventrolateral medulla of the rat are intermingled with catecholamine‐containing neurons of the C1 cell group, but are not themselves catecholamine‐containing; (b) that many non‐spinally projecting respiratory neurons have axonal arborisations within the ventrolateral medulla in the same region as the C1 cell group, other respiratory neurons, and neurons reported to have a cardiovascular function; and (c) that the dendrites of respiratory neurons in this region radiate throughout the ventrolateral medulla and frequently approach the ventral

ISSN:0092-7317    

DOI:10.1002/cne.903010409

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

年代:1990

数据来源: WILEY

摘要:

AbstractWGA‐HRP was used to examine projections to the brainstem from the supplementary eye field (SEF). The SEF was defined electrophysiologically in awake, behaving monkeys and connections were compared to those of the arcuate frontal eye field (FEF), area 6DC, and primary motor cortex. The SEF was found to have either direct or indirect connections with almost every known pre‐ and paraoculomotor structure of the brainstem. The SEF was found to project bilaterally to layers I and IV of a tangentially widespread region of the superior colliculus. Terminal label was evident in the pretectal olivary nucleus, nucleus of the optic tract, nucleus raphe interpositus (omnipause region), nucleus prepositus hypoglossi, the perioculomotor cap of the central gray, dorsal central gray, nucleus reticularis tegmenti pontis, nucleus reticularis pontis oralis, and to multiple nuclei of the basis pontis (most densely to the dorsomedial nucleus). Bilateral projections were found in the parvicellular red nucleus. Reciprocal connections were present in the nucleus limitans, the mesencephalic reticular formation, locus coeruleus, and the serotonergic nuclei of the raphe complex (dorsalis and central superior). Overall patterns of connectivity were similar to those of the FEF and markedly different from those of the contiguous dorsocaudal area 6 or primary motor cortex. It was concluded that observed patterns of SEF‐brainstem connectivity further justifies viewing this region as a distinct eye field that is likely to serve preparatory and trigger functions in the generation of saccadic eye move

ISSN:0092-7317    

DOI:10.1002/cne.903010410

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe effects of unilateral cochlea removal on GABA‐immunoreactive (GABA‐I) terminals in nucleus magnocellularis (NM) of the chick were assessed by immunocytochemical (ICC) techniques. Posthatch chicks (5–8 days old) survived from 1–37 days following unilateral cochlea removal. In the ipsilateral NM, the density of GABA‐I terminals appeared to increase relative to normal controls. 10–37 days after cochlea removal. However, most of that increase could be attributed to a decrease in cell size, cell number, and volume of the nucleus as a result of deafferentation. In the contralateral NM, the density of GABA‐I terminals decreased relative to the ipsilateral NM and to normal animals 1–21 days after cochlea removal. The number of GABA‐I terminals per NM neuron also decreased in the contralateral NM while that in the ipsilateral NM was comparable to normal controls. To ascertain whether these changes represented changes in the number of terminals or in the amount of GABA contained within the terminals, we also examined these terminals using an antibody to glutamic acid decarboxylase (GAD), the biosynthetic enzyme for GABA. Following unilateral cochlea removal, there was no difference in the density of GAD‐I terminals in NM between the two sides of the brain for any of the survival times. Similarly, bilateral cochlea removal had no discernible effect on the density of GABA‐I terminals in NM. These data suggest that unilateral deafferentation may temporarily downregulate the biosynthesis of GABA in

ISSN:0092-7317    

DOI:10.1002/cne.903010411

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

年代:1990

数据来源: WILEY