摘要:

AbstractGlial cell‐lined derived neurotrophic factor (GDNF) has been shown to promote survival of developing mesencephalic dopaminergic neurons in vitro. In order to determine if there is a positive effect of GDNF on injured adult midbrain dopaminergic neurons in situ, we have carried out experiments in which a single dose of GDNF was injected into the substantia nigra following a unilateral lesion of the nigrostriatal system. Rats were unilaterally lesioned by a single stereotaxic injection of 6‐hydroxydopamine (6‐OHDA; 9 μg/4 μl normal saline with 0.02% ascorbate) into the medial forebrain bundle and tested weekly for apomorphine‐induced (0.05 mg/kg s. c. ) contralateral rotation behavior, Rats that manifested>300 turns/hour received a nigral injection of 100 μg GDNF, or cytochrome C as a control, 4 weeks following the 6‐OHDA lesion, Rotation behavior was quantified weekly for 5 weeks after GDNF. Rats were subsequently anesthetized, transcardially perfused, and processed for tyrosine hydroxylase immunohistochemistry. It was found that 100 μg GDNF decreased apomorphine‐induced rotational behavior by more than 85%. Immunohistochemical studies revealed that tyrosine hydroxylase immunoreactivity was equally reduced in the striatum ipsilateral to the lesion in both cytochrome C and GDNF‐injected animals. In contrast, large increments in tyrosine hydroxylase immunoreactivity were observed in the substantia nigra of animals treated with 100 μg of GDNF, with a significant increase in numbers of tyrosine hydroxylase‐immunoreactive cell bodies and neurites as well as a small increase in the cell body area of these neurons. The results suggest that GDNF can maintain the dopaminergic neuronal phenotype in a number of nigral neurons following a unilateral nigrostriat

ISSN:0092-7317    

DOI:10.1002/cne.903550402

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

年代:1995

数据来源: WILEY

摘要:

AbstractTemporal‐spatial patterns of surviving Purkinje cells were studied quantitatively in a rat mutant(shaker)with differential hereditary cerebellar ataxia and Purkinje cell degeneration.Shakerrat mutants are characterized behaviorally as mild if they are ataxic or as strong if they have ataxia and tremor. Purkinje cells degenerate in both mild and strongshakermutants, but the temporal and spatial patterns of cell death are strikingly different. In mildshakermutants, Purkinje cell death is temporally restricted, with 31‐46% of the Purkinje cells in lobules I‐IX dying by 3 months of age. Very few Purkinje cells degenerate after this age. Purkinje cell death is spatially random. In lobules I‐IX, every second, third, or fourth Purkinje cell degenerates. Purkinje cells in lobule X do not degenerate. In strongshakermutants, Purkinje cell degeneration is temporally protracted and spatially restricted. By 3 months of age, most Purkinje cells in lobules I‐VIa, ‐b, and ‐d, and ‐d have degenerated. Numerous Purkinje cells in the paravermis of lobules VIIb‐VIII have also degenerated. Surviving Purkinje cells in the vermis and lateral hemisphere of lobules VIIb‐VIII are aligned in parasagittally oriented stripes or transversely oriented bands. Purkinje cells continue to degenerate in localized areas of the posterior lobe such that, by 18 months of age, surviving Purkinje cells are limited primarily to lobules VIc, VIIa, IXd, and X. Quantitative analysis indicates that none of the Purkinje cells in these

ISSN:0092-7317    

DOI:10.1002/cne.903550403

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

年代:1995

数据来源: WILEY

摘要:

AbstractThis study examined cortical connections of areas 3b and 1 in 17 macaque monkeys in reference to regional somatotopography. The fluorescent retrograde tracers Fast Blue and Diamidino Yellow and the anterograde tracer Rhodamine Dextran were injected into closely related cutaneously responsive sites in primary somatosensory cortex, e. g., adjacent digits.Supra‐ and infragranular layers in nearly all studied areas contained labeled pyramidal cells. Labeled infragranular cells predominated at the fringes of a distribution where cells labeled from different tracer injections in the same brain intermixed more.All topographical regions across area 1 have reciprocal connections with areas 4, 3a, 3b, 1, 2, and 5. Intrinsic connections within area 1 and between it and area 2 are greatest; those with area 3b are less. Intrinsic connections within area 3b exceed all other nearby projections from this area which reciprocally connects with areas 3a, 1 and 2. Connections appear topographically organized, including those with poorly mapped regions, like area 5. These connections link representations of neighboring skin and skip map regions that include disjoint dermatomal areas. Connections from adjacent digit representations overlap; however, double‐labeled cells were not found. Distal and proximal digit zones mostly interconnect within an area. Intrinsic connections spread further in area 1 than in area 3b, thereby joining more disparate topographical zones than interareal connections, which project more homotopically. The domain over which the map in somatosensory cortical area I (SI) dynamically changes following in tracortical microstimulation (Recanzone, Merzenich and Dinse, Cerebral Cortex 2:181‐196, 1992) may depend on the range of intrinsic connections observed in this study. The extent of connections between cortical areas was less than expected and this challenges the hypothesis that these connections directly create receptive field enlarge

ISSN:0092-7317    

DOI:10.1002/cne.903550404

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

年代:1995

数据来源: WILEY

摘要:

AbstractCortical connections between various body representations in areas 3b and 1 and lateral parietal cortex were examined in 18 macaque monkeys. We injected tracers (Fast Blue, Diamidino Yellow, Horseradish Peroxidase, and Rhodamine Dextran), alone or in combination, into closely related cutaneous responsive sites, e. g., adjacent digits. Separated patches of labeling were found across the parietal operculum and insula for all injected locations. On the basis of cytoarchitectural criteria, the labeled regions include the second somatosensory area (SH), retroinsular area (Ri) and granular insula (Ig). Assuming the connections are homotopical from physiologically identified body representations in primary somatosensory cortex, the labeling patterns in SII include complete anterior and posterior body maps. The orientation of the body is erect in the posterior and supine in the anterior SII region. Area 3b has greater density of connections with anterior SIL The maps are mirror images aligned along the distal extremities. The anterior‐posterior (A‐P) length of the “SII region” exceeds 7 mm; it extends in the coronal plane from the fundus of the lateral sulcus to surface cortex near the anterior tip of the intraparietal sulcus. Two additional topographically organized maps are likely in Ri. These are “worm‐like” body maps oriented along the A‐P axis and joined at the head representation. Connections with the center of Ig are not somatotopically organized.The diversity of somatosensory areas in lateral parietal cortex revealed by the labeled connections was discussed in reference to prior mapping of SII in monkeys and was compared to reports of multiple areas in this region of cortex i

ISSN:0092-7317    

DOI:10.1002/cne.903550405

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe main goal of the present study was to examine the possibility of electrophysiologically identifying the excitable enteric S and AH neurons by use of one single criterion. Intracellular recordings were made from 189 cells of 64 ganglia in isolated preparations of the myenteric plexus of the guinea pig distal ileum. The recordings were made under visual control of the cells by using Hoffman Modulation Contrast optics at high magnification (600 X). From photomicrographs, the soma size and the location within the ganglion of the individual (unstained) cells were determined.The cells were classified into three types according to their electrical excitability and the shape of the action potential. Excitable cells were classified as AH cells (n = 84) if the action potential showed a shoulder on the falling phase, otherwise as S cells (n = 56). Cells in which no action potential could be evoked by current injection were classified as nonspiking (NS) cells (n = 49). The three classes of cells showed significant differences with respect to membrane potential, input resistance and fast synaptic input. The AH cells had significantly larger somata (P<0.01) than the S cells. The NS cells were significantly smaller than the AH and S cells (P<0.01). AH and S cells were found to be randomly located in the ganglia, whereas the NS cells clustered (P<0.008) in close proximity to the onsets of internodal strands.We conclude that the shoulder of the action potential canbe used as a single criterion to distinguish “on line” S and AH neurons unequivoca

ISSN:0092-7317    

DOI:10.1002/cne.903550406

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

年代:1995

数据来源: WILEY

摘要:

AbstractHistochemical staining for cytochrome oxidase (CO) and axonal transport of horseradish peroxidase (HRP) were used to investigate thalamocortical connections in the vibrissa‐barrel system of adult rats. CO staining revealed that the medial division of the ventrobasal thalamic nucleus (VBm) consists of intensely stained rod‐like configurations, containing thalamocortical projection neurons and intervening neuropil, separated by lighter‐stained septa. CO‐dark rods span the thickness of VBm, are arranged in a pattern of rows and arcs that resembles the distribution of vibrissae on the mystacial pad, and are similar to the cytoarchitectonic structures termed “barreloids” in the mouse thalamus. Based upon the dimensions of CO‐dark structures and the numerical density of neurons in VBm we estimated that a barreloid in the rat may contain 250‐300 neurons.HRP injections into lamina IV of the somatosensory cortex led to retrograde labeling of neurons within one or more barreloids. When injections were centered within the CO‐dark hollows of cortical barrels about 95% of retrogradely labeled neurons were located in the barreloid that is isomorphic to the injected barrel; up to 5% of labeled neurons were located within a single adjacent barreloid. Barrel hollow injections that also included a barrel side yielded a larger proportion of labeled neurons in non‐isomorphic barreloids. Interestingly, such extra‐barreloid labeling was topologically consistent in that HRP‐labeled neurons were distributed among barreloids that corresponded to cortical barrels nearest the injected barrel side. Injections into the septa between barrels similarly resulted in labeling within barreloids that corresponded to cortical barrels flanking the septal injection site.Following lamina IV injections the density of labeled neurons tended to be highest in the ventrolateral one‐half to two‐thirds of VBm. Retrograde labeling of neurons in the dorsomedial one‐third to one‐half of VBm was more often observed after HRP injections at the lamina V/VI border. Thus, barreloid neurons may be heterogeneous with respect to their laminar pattern of terminations within the somatosensory cortex. Some HRP injections in the cortex resulted in orthograde labeling of corticothalamic axons in the barreloids. When observed, labeled corticothalamic axons arborized principally within the barreloid isomorphic to the injected barrel column. Indeed, terminal labeling was densest in the vicinity of neurons retrogradel

ISSN:0092-7317    

DOI:10.1002/cne.903550407

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

年代:1995

数据来源: WILEY

摘要:

AbstractDevelopment of the peripheral innervation patterns of the L1‐S1 lumbosacral ganglia and motor segments in embryonic day 12‐17 (E12‐17) rat embryos was examined using carbocyanine dyes. Individual dorsal root ganglia (DRGs) and/or isolated ventral horn (VH) segments, or individual peripheral nerves, were isolated in rat embryos fixed at different stages and filled with one of three carbocyanine dyes; DiI, DiA, and DiO. Individual experimental preparations included labeling of (1) single DRGs; (2) multiple DRGs with alternating dyes, DiO, DiI, and DiA; (3) single isolated VH segments; (4) multiple VH segments with alternating dyes; (5) single VH segments and the corresponding segmental DRGs with different dyes; and (6) two or more individual peripheral nerves labeled with different dyes.Results from these preparations have shown that the first fibers exited the lumbar ventral horn and DRGs at E12. At E13 major nerve trunks (e. g., femoral and sciatic) were visible as they exited the plexus region. By E14 afferent fibers were present in the epidermis of the proximal hindlimb, and the major nerve trunks extended into the leg. Fibers originating from L3 to L5 (DRG and VH) reached the paw by E14. 5‐E15, and the epidermis of the most distal toes was innervated by E16‐E16. 5. While afferent fibers and motor axons of the same segmental origin mixed extensively in the spinal nerve, fibers of different segmental origin combined in the plexus and major nerve trunks with little or no interfascicular mixing.Dermatomes observed at E 14 were in general spotty and non‐contiguous. However, by E 16 the dermatomes resembled mature forms with substantial overlap only between adjacent ones. Thus the adult pattern of spatial relationships between cutaneous afferent fibers in the periphery is established early in

ISSN:0092-7317    

DOI:10.1002/cne.903550408

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

年代:1995

数据来源: WILEY

摘要:

AbstractThese studies were designed to determine the pattern of initial afferent fiber ingrowth into the prenatal spinal gray matter and the establishment of the topographic organization of the presynaptic neuropil in the dorsal horn. A total of 113 lumbar dorsal root ganglia were labeled with carbocyanine fluorescent dye DiI or DiA in 67 rat embryos and neonatal pups aged embryonic day 13 to postnatal day O (E13–PO).The initial fiber penetration of the lumbar spinal gray began at E15 and was restricted to the segments of entry. Subsequent growth of fibers into gray matter of adjacent segments began approximately one day later, and this delay was continued, about one day for each successive segment. A second wave of ingrowth of putative small‐diameter afferents into the substantia gelatinosa began at E19 and also displayed the same rostrocaudal delay. Fiber ingrowth was specific and occupied the somatotopic area appropriate for the adult, from the earliest stages (E 18) in which dorsal horn laminae could be adequately defined. The somatotopic organization of the presynaptic neuropil in laminae III and IV did not change significantly throughout embryonic development as the amount of overlap between adjacent and non‐adjacent ganglion projections remained constant throughout embryonic development. In addition, it was found that fibers innervating the proximal and distal hindlimb entered the spinal gray simultaneously at E 15 before the innervation of the distal toes was established.The results of these studies indicate that the somatotopic organization of the presynaptic neuropil is established very early in development and requires little refinement to match that seen in the adult. The simultaneous penetration of the fibers originating from the proximal and distal areas of the limb before innervation is complete suggests that this ingrowth may be independent of the establishment of specific peripheral connec

ISSN:0092-7317    

DOI:10.1002/cne.903550409

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe first thalamocortical axons to arrive in the developing cerebral cortex traverse a pathway that is separate from the adjacent intracortical pathway for early efferents, suggesting that different molecular signals guide their growth. We previously demonstrated that the intracortical pathway for thalamic axons is centered on the subplate (Bicknese et al. [1994] J. Neurosci. 14:3500‐3510), which is rich in chondroitin sulfate proteoglycans (CSPGs; Sheppard et al. [1991]J. Neurosci. 11:3928‐3942), whereas efferent axons cross the subplate to exit in a zone containing much less CSPG. To define the molecular composition of the subplate further, we used antibodies against CSPG core proteins and chondroitin sulfate disaccharides in an immunohistochemical analysis of their distribution in the developing neocortex of the rat. Immunolabeling for neurocan, a central nervous system‐specific CSPG (Rauch et al. [1992] J. Biol. Chem. 267:19537‐19547), and for chondroitin 6‐sulfate and unsulfated chondroitin becomes prominent in the subplate before the arrival of thalamic afferents. Immunolabeling is initially sparse in the cortical plate but appears later in maturing cortical layers. A postnatal decline in immunolabeling occurs uniformly for most proteoglycans, but, in the somatosensory cortex, labeling for neurocan, phosphacan, and chondroitin 4‐ and 6‐sulfate declines in the centers of the whisker barrels before the walls. In contrast to neurocan, immunolabeling for other proteoglycans is either uniformly distributed (syndecan‐1, N‐syndecan, 5F3, phosphacan, chondroitin 4‐sulfate), restricted to axons (PGM1), distributed exclusively on nonneuronal elements (2D6, NG2, and CD44), or undetectable (9. 2. 27, aggrecan, decorin). Thus, neurocan is a candidate molecule for delineating the intracortical pathway of thalamocortical axons and distinguishing it from that of

ISSN:0092-7317    

DOI:10.1002/cne.903550410

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

年代:1995

数据来源: WILEY

摘要:

AbstractTransneuronal tracing techniques were used to identify sites in the central nervous system involved in the neural control of urethral function. The distribution of virus‐infected neurons was examined in the spinal cord and brainstem at various intervals (56‐96 hours) following pseudorabies virus (PRV) injection into the urethra. In the lumbosacral (L6‐Sl) spinal cord at 56 hours, neurons containing PRV immunoreactivity (PRV‐IR) were located in the region of the sacral parasympathetic nucleus (SPN), around the central canal, and in the dorsal commissure. Some animals also exhibited PRV‐IR in cells in the L6 dorsolateral motor nucleus. At longer survival times (72‐96 hours), PRV‐IR cells were observed in the superficial and deeper laminae of the dorsal horn, and increased numbers of PRV‐IR cells were consistently detected in the region of the SPN, around the central canal, and in the dorsal commissure. PRV‐IR fiber‐like staining also occurred along the lateral edge of the dorsal horn extending from Lissauer's tract to the region of the SPN. In rostral lumbar segments (Ll‐L2), PRV‐IR cells were located in the region of the dorsal commissure and the intermediolateral cell nucleus (IML), around the central canal, and in the dorsal horn. After 72‐84 hours, PRV‐IR cells were also noted at more rostral levels of the neuraxis including the medulla, pons, midbrain, and diencephalon. At 72 hours, PRV‐IR cells were consistently observed in Barrington's nucleus (pontine micturition center), nucleus raphe magnus (RMg), parapyramidal reticular formation, and the A5 and A7 regions. At 78–84 hours, additional regions exhibited PRV‐IR cells, including the periaqueductal gray, locus coeruleus, the dorsal and ventral subcoeruleus alpha, and the red nucleus. A few cells were also located in the lateral hypothalamic area. This distribution of PRV‐labeled cells in the spinal cord and brainstem is similar in many respects to the distribution of cells labeled in previous studies by PRV injection into the urinary bladder. This overlap of urethra and bladder neurons is consistent with the results of physiological experiments indicating a close coordination between the central nervous contr

ISSN:0092-7317    

DOI:10.1002/cne.903550411

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

年代:1995

数据来源: WILEY