摘要:

AbstractThe morphology and laminar distribution of immunolabeled neurons in the medial and dorsomedial telencephalic cortices of the lizardPodarcis hispanicawere examined in vibratome sections after preembedding γ‐aminobutyric acid (GABA)‐immunocytochemistry. In both cortical areas and at all rostrocaudal levels, GABA‐immunoreactive neurons were found in all cortical layers, with the largest number (74%) of GABA‐positive cells in layer 3. GABA‐positive neurons were classified into pyramidlike, vertical‐fusiform, multipolar, and horizontal neurons. Cells that could be so classified were counted in each cortical lamina.In themedial cortex, multipolar and horizontal‐bipolar cells dominated layer 1. Layer 2 displayed mainly horizontal and pyramidlike cells at its outer margin and pyramidlike cells at its inner margin. In layer 3, horizontal cells were the prevalent group. In thedorsomedial cortex, layer 1 mainly contained small multipolar neurons (35% of layer‐1 cells) in its outer third and vertical‐fusiform neurons (37% of layer‐1 cells) in its inner two thirds. In layer 2, 47% of the few GABA‐positive perikarya were pyramidlike. The largest population of neurons in layer 3 was that formed by multipolar cells (45% of layer‐3 cells).Ultrastructural examination revealed that GABA‐immunoreactive neurons possessed indented euchromatic nuclei with a central nucleolus. Their cytoplasm contained numerous mitochondria and a very well‐developed granular endoplasmic reticulum. Their somata were contacted by numerous unstained boutons making asymmetric contacts and by a few symmetric synapses of GABA‐positive terminals. Dendrites of GABA‐immunoreactive cells were thin, with irregular outlines, and generally aspinous. Like the somata, dendrites were contacted by many unstained asymmetric synapses. Some dendritic profiles also received symmetric contacts from GABA‐positive boutons.GABA‐positive terminal‐like puncta were found throughout the layers, with a maximal concentration in layer 2. Electron microscopy confirmed that nearly all of the puncta represent GABA‐positive terminal boutons.Comparison of GABA‐immunoreactive cells inPodarciswith those found in the mammalian hippocampus suggests that these cells may be inhibitory

ISSN:0092-7317    

DOI:10.1002/cne.902780402

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe thalamic reticular nucleus has been shown to receive cholinergic innervation from both the nucleus basalis of Meynert in the forebrain and the pedunculopontine and laterodorsal tegmental nuclei in the brainstem (Steriade et al.:Brain Res. 408:372–376, '87; Levey et al.:Neurosci. Lett. 74:7–13, '87). Relatively dense populations of choline acetyltransferase‐ (ChAT) immunoreactive axons and terminallike varicosities have been shown to be distributed throughout this nucleus (Levey et al.:J. Comp. Neurol. 257:317–332, '87). In this study, the ultrastructure of ChAT‐immunoreactive axons and of their synaptic terminals in the reticular nucleus was examined in the electron microscope. All ChAT‐immunoreactive axonal profiles in the reticular nucleus were presynaptic; the postsyaptic elements were exclusively dendritic profiles; and no axo‐axonic or axosomatic contacts from labelled axons were observed. Most ChAT‐immunoreactive synaptic contacts were made by profiles less than 0.25 μm in minor diameter. Single ChAT‐immunoreactive axons made synaptic contact with several dendritic profiles as the axons were followed through serial sections. These results suggest that the cholinergic innervation of the reticular nucleus will modulate the function of reticular neurons by synapsing onto the dendrites of its neurons without direct effect on the corticothalamic and thalamocortical terminals which also innervate the

ISSN:0092-7317    

DOI:10.1002/cne.902780403

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

年代:1988

数据来源: WILEY

摘要:

AbstractDistinct laminae and sublaminae in the goldfish optic tectum exhibit substantial differences in cytochrome oxidase (C.O.) reactivity. To determine whether these differences are associated with differential reactivity of different neuronal profiles, each tectal sublamina was examined at the ultrastructural level following C.O. treatment. The greatest abundance of darkly reactive mitochondria was found in the optically innervated layers within both pre‐ and postsynaptic profiles in correspondence with the most intense staining of these layers at the light microscopic level. Many reactive mitochondria were localized within terminals that were presumed to be optic on the basis of cytological criteria or were shown to be optic by filling optic fibers with HRP and processing so as to simultaneously demonstrate both mitochondrial C.O. reactivity and HRP labeling. These optic terminals tended to differ from each other in size and level of reactivity. The largest terminals were located within sublamina d of the stratum fibrosum et griseum superficials (SFGSd), and these were the most intensely reactive and contained the greatest number of darkly reactive mitochondria. Medium‐sized terminals were found within sublaminae SFGSa, SFGSb, and a and c of the stratum album centrale (SACa,c). These were also darkly reactive but contained fewer mitochondria. Other medium‐to‐small optic terminals were found in stratum opticum a and b (60a,b), SFGSb, SFGSc, and stratum griseum centrale c (SGCc). These typically contained fewer mitochondria that also tended to be relatively less reactive, although darkly reactive mitochondria were also present. We suggest that the metalbolic differences within optic terminals of different size and sublaminar stratification arise from different ganglion cell classes and that the different optic layers of tectum are functionally substratified.As expected, darkly reactive mitochondria were most abundant in the intensely stained sublaminae, which included the optic lamina SFGS and nonoptic sublamina SGCa, and they were found not only within optic terminals but also within dendrites, presynaptic dendrites, and nonoptic terminals as well. Glial processes tended to contain less reactive mitochondria. The most prominent of the nonoptic terminals were the large‐diameter P1 terminals, which contained pleomorphic vesicles and formed symmetric (presumed inhibitory) synapses. In stratum marginale most of the darkly reactive mitochondria were localized within dendrites. In the rest of the tectal layers most of the darkly reactive mitochondria were found in both presynaptic terminals and dendrites. The localization of numerous reactive mitochondria to terminals contrasts with several mammalian CNS structures in which reactive mitochondria are found predominantly in dendrites. The darkly reactive layers also tended to have more complex neuropils with a greater variety of presynaptic profiles. The less reactive neuropil strata contained comparatively few P1 terminals. The remaining layers, which contained mainly cell bodies (stratum periventriculare) or axons (SOa, SOc, SACb), were only lightly to moderately reactive.These laminar differences further support our previous light‐level observations that the goldfish optic tectum may be subdivided into metabolically and, presumably, functionally distinct

ISSN:0092-7317    

DOI:10.1002/cne.902780404

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

年代:1988

数据来源: WILEY

摘要:

AbstractCytochrome oxidase (C.O.) histochemistry and cytochemistry were used to examine the effects of optic denervation and subsequent optic fiber regeneration on oxidative metabolism in the retina and optic tectum of the goldfish. In the tectum, there was a dramatic and rapid decrease in C.O. activity within the optic layers 3–4 days after contralateral eye removal or optic nerve crush. At the E.M. level this was correlated with an initial decrease in mitochondrial reactivity within optic terminals followed by the subsequent degradation of mitochondria and phagocytosis of optic terminals.By 1 month after optic nerve crush, the entire tectum was reinnervated. However, the normal dark reactivity of the stratum fibrosum et griseum superficialis (SFGS), the main optic innervation layer, was not restored until after 3–4 months postcrush. The normal intense reactivity of the largediameter optic axons and terminals at the bottom of the SFGS required an even longer period, about 7–8 months, for full recovery. The delayed restoration of C.O. reactivity was not due to a delay in synaptogenesis or in mitochondrial accumulation within optic terminals but to a delay in the maturation of mitochondrial reactivity. Following regeneration, the normal sublaminar stratification of C.O. bands was reestablished, suggesting that metabolically distinct classes of optic fibers may reinnervate at their original sublaminae. By using a distinct and persistent C.O. reactive sublamina, a of stratum griseum centrale (SGCa), just subjacent to the SFGS, it was possible to measure the thickness of the SFGS following optic denervation and subsequent reinnervation. At 1 week after optic nerve crush, the SFGS shrank by 35%. During regeneration, the thickness of the SFGS gradually increased to about 23% above normal at 2 months postcrush and this was maintained indefinitely.In the retina, ganglion cells were hypertrophic by 1 month postcrush and exhibited elevated levels of C.O. during the same period of time when optic terminals were unreactive. This indicates that oxidative metabolic activity within perikarya and axon terminals of the same neuron may be locally and independently regulated. It also suggests that in spite of the well‐known elevation of axonal transport during the initial period of axon elongation and synaptogenesis, that oxidative metabolic energy production within the optic fibers is less than that of the mature projection. We hypothesize that the comparatively greater oxidative metabolism of the mature projection results from greater synaptic convergence of fibers having correlated activity and may be a target‐mediated metabolic response of optic axons having reached their topographically appropriate synap

ISSN:0092-7317    

DOI:10.1002/cne.902780405

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

年代:1988

数据来源: WILEY

摘要:

AbstractA new approach to high‐resolution 2‐deoxy‐D‐glucose (2DG) emulsion‐autoradiography which combines improved retention of 2DG labeling, staining with immunohistochemical and other specific markers, and automated data collection and analysis of local silver grain and stain densities is described. The Durham et al. (J. Neurosci. 1:519–526, '81) procedure for fixation of 2DG with periodate‐lysine‐paraformaldehyde (PLP, McLean and Nakane:J. Histochem. Cytochem. 22:1077–1083, '74) was adapted to increase retained label roughly tenfold. Phenobarbital anesthesia is induced 45 minutes after 2DG injection. Barbiturate anesthesia increases brain glycogen (Nelson et al.:J. Neurochem. 15:1271–1279, '68) and presumably increases the incorporation of intracellular 2DG from 2DG‐6P into brain glycogen and other molecules (Nelson et al.:J. Neurochem. 43:949–956, '84; Pentreath et al.:Neuroscience 7:759–767, '82). Iodoacetate is added to cold fixative to prevent glycogen breakdown (Cammermeyer and Fenton:Histochemistry 76:339–356, '82).This high‐resolution 2DG protocol is directly compatible with many other neuroanatomical techniques. We demonstrate 2DG emulsion autoradiography combined with cytochrome oxidase (CO) histochemistry, markers for axonal pathway tracing, plastic embedding for semithin sections, and immunohistochemical staining for glutamate decarboxylase (GAD). The method should be compatible with antibodies for other antigens and with other neuroanatomical stains.To collect the data directly from microscope slides, a computer‐controlled microscope was integrated with image‐processing software to eliminate the need for manual counting and scoring of autoradiograms. Regions of interest are scanned automatically at high resolution to map regional labeling and/or stain density. There is excellent correspondence between computer‐enhanced two‐dimensional maps of the data and the original autoradiograms. Automated counts for five specimens were compared to counts of labeled cells by trained observer. The correlation between the two sets of measurements is high (r =. 93).Automated data collection has been generalized to measure regional stain densities on the autoradiographed sections for direct comparison with silver grain density. The method is extremely flexible, especially since new image‐processing strategies can be developed in software to extract the desired information from materials labeled by other methods (e.g., HRP).The combination of experimental and data collection strategies generates two‐ or three‐dimensional “maps” of 2DG labeling, histochemical stain, etc., over a brain area of interest and allows direct comparison of these different maps. To our knowledge this is the first report of quantitative reconstructions of 2DG labeling patterns on the basis of large and systematically sc

ISSN:0092-7317    

DOI:10.1002/cne.902780406

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

年代:1988

数据来源: WILEY

摘要:

AbstractCortical columns associated with barrels in layer IV of the somatosensory cortex were characterized by high‐resolution 2‐deoxy‐D‐glucose (2DG) autoradiography in freely behaving mice. The method demonstrates a more exact match between columnar labeling and cytoarchitectonic barrel boundaries than previously reported. The pattern of cortical activation seen with stimulation of a single whisker (third whisker in the middle row of large hairs—C3) was compared with the patterns from two control conditions—normal animals with all whiskers present (“positive control”)—and with all large whiskers clipped (“negative control”). Two types of measurements were made from 2DG autoradiograms of tangential cortical sections: (1) labeled cells were identified by eye and tabulated with a computer, and (2) grain densities were obtained automatically with a computer‐controlled microscope and image processor.We studied the fine‐grained patterns of 2DG labeling in a nine‐barrel grid with the C3 barrel in the center. From the analysis we draw five major conclusions.1Approximately 30–40% of the total number of neurons in the C3 barrel column are activated when only the C3 whisker is stimulated. This is about twice the number of neurons labeled in the C3 column when all whiskers are stimulated and about ten times the number of neurons labeled when all large whiskers are clipped.2There is evidence for a vertical functional organization within a barrel‐related whisker column which has smaller dimensions in the tangential direction than a barrel. There are densely labeled patches within a barrel which are unique to an individual cortex. The same patchy pattern is found in the appropriate regions of sections above and below the barrels through the full thickness of the cortex. This functional arrangement could be considered to be a “minicolumn” or more likely a group of “minicolumns” (Mountcastle: In G.M. Edelman and U.B. Mountcastle (eds):The Material Brain: Cortical Organization and the Group‐Selective Theory of Higher Brain Function.Cambridge: MIT Press, '78).3Within the stereotyped geometry of the barrel field, there is considerable individual variation in the radial labeling distribution in corresponding (homotypical) columns of different cerebral hemispheres. This result is consistent with the hypothesis that dynamic processes operate to determine the connection strengths between neural elements in somatosensory cortex. It provides a basis for testing various “connectionist” and “group selection” theories of neural organization and development.4There are reproducible laminar labeling patterns consistent with known physiology for all experimental conditions. In activated columns, layer IV labeling is greatly increased, and all laminae show increases in labeling over adjacent unstimulated columns. With C3‐only stimulation the label in neighboring columns is predominantly in layers II and III.5The labeling pattern in B and D barrel rows shows a consistent asymmetry with all whiskers stimulated (higher in row D barrels) which is correlated with frequency of whisker‐substrate contact (greater for row D whiskers) during behavior. When C3 alone is stimulated the opposite row asymmetry is observed (higher in row B barrels). This shift in asymmetry is consistent with the hypothesis that experience determines

ISSN:0092-7317    

DOI:10.1002/cne.902780407

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

年代:1988

数据来源: WILEY

摘要:

AbstractAccumulating evidence indicates that electrophysiologically distinct subsets of sympathetic neurons selectively innervate different classes of targets. The organization of this system may therefore be reflected in the sympathetic fiber contents of peripheral nerves. To test this possibility, we have mapped the pathways followed by three groups of postganglionic sympathetic axons in the bullfrog by recording compound action potentials and by retrograde tracing with horseradish peroxidase (HRP). The axons that were studied arise from fast B, slow B, and C‐type neurons in ganglia 9 and 10 at the lumbar end of the paravertebral sympathetic chain. They project to peripheral targets primarily by way of the sciatic nerve and can be distinguished by the velocities with which they conduct action potentials.Action potentials were recorded with suction electrodes from isolated preparations composed of paravertebral chain ganglia 7–10, the sciatic nerve, and branches of the sciatic nerve that supply striated muscles, skin, and the bladder. Preganglionic B fibers were selectively activated by stimulating the paravertebral chain rostral to ganglion 7, and preganglionic C fibers were selectively activated by stimulating spinal nerves 7 and 8 at points central to their rami communicantes. Compound action potentials recorded from the sciatic, peroneal, tibial, and sural nerves and from the primary trunk of the pelvic nerve were each found to contain three components produced, respectively, by fast B, slow B, and C‐type sympathetic axons. Similarly, action potentials recorded from cutaneous branches of the sciatic tree were found to contain three sympathetic components. By contrast, when compound action potentials were recorded from branches of the sciatic tree that directly enter and innervate striated muscles and also the bladder, the sympathetic responses were found to arise solely from C‐type axons.HRP was used to label the sympathetic neurons that project to the sartorius muscle and into the cutaneous lateral crural nerve. Retrograde transport of HRP from the sartorius muscle labeled 17 ± 4 (mean ± s.d.) sympathetic neurons and 27 ± 3 spinal motoneurons while transport from the lateral crural nerve labeled 68 ± 47 sympathetic neurons but no spinal neurons. The average somatic diameter of ganglion cells projecting to the sartorius muscle was significantly smaller than that of cells projecting to the lateral crural nerve.The electrophysiological results indicate that fast B and slow B sympathetic axons in the sciatic trunk and its primary branches project selectively into cutaneous nerves while sympathetic C axons project into all peripheral nerves. The HRP data support these findings given that C cells are, on average, smaller than B cells. Together the results provide an anatomical basis for the hypothesis that B and C neurons serve different physiologica

ISSN:0092-7317    

DOI:10.1002/cne.902780408

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

年代:1988

数据来源: WILEY

摘要:

AbstractPrevious attempts to trace the central pathways of the thin axons from type II spiral ganglion neurons have been hampered by technical difficulties such as fading of the reaction product as distance increases from the injection site (Ryugo et al.:Soc. Neurosci. Abstr. 12:779, '86; Brown:J. Comp. Neurol. 260:591–604, '87). By using small rodents (gerbils and mice), which have short auditory nerves, we have succeeded in filling the entire central axon and terminals of type II neurons after peripheral injections of horseradish peroxidase. The general course of the type II fibers within the auditory nerve and cochlear nucleus is similar to that of type I fibers except that terminals from type II neurons are often found in regions of the cochlear nucleus that have high densities of granule cell

ISSN:0092-7317    

DOI:10.1002/cne.902780409

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

年代:1988

数据来源: WILEY

摘要:

AbstractHorseradish peroxidase was used to label axons of olivocochlear (OC) neurons by intracellular injections in cats and extracellular injections in rodents. These axons arise from cell bodies in the superior olivary complex and project to the cochlea. En route to the cochlea, the thick axons (>0.7 μm diam.) of medial olivocochlear (MOC) neurons formed collaterals that terminated in the ventral cochlear nucleus, the interstitial nucleus of the vestibular nerve (in cats), and the inferior vestibular nucleus (in rodents). The thin axons (<0.7 μm diam.), presumed to arise from lateral olivocochlear (LOC) neurons, did not branch near the CN. Within the CN, the MOC collaterals tended to ramify in and near regions with high densities of granule cells, regions also associated with the terminals of type II afferent axons (Brown et al.:J. Comp. Neurol. 278:581–590, '88). These results suggest that those fibers associated peripherally with outer hair cells (MOC efferents and type II afferents) are associated centrally with regions containing granule cells, whereas those fibers associated with inner hair cells peripherally (LOC efferents and type I afferents) are

ISSN:0092-7317    

DOI:10.1002/cne.902780410

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

年代:1988

数据来源: WILEY

摘要:

AbstractThis paper describes electron microscopic observations of dense‐cored vesicle‐containing axons, cell bodies, and endings of the terminal nerve in several elasmobranchs. The vesicles are found in two apparent cell types, one with a polymorphic nucleus and another with an oval nucleus. The types may correspond to cells producing one each of two neuropeptides (LHRH and FMRF‐amide) that have previously been localized in the nerve. Dense‐cored vesicles are found in many unmyelinated fibers in both the terminal nerve proper and its major ganglia. Some of these form complicated structures with interdigitation and wrapping of membranes. Vesicle‐containing fibers branch from the nerve, run along nearby blood vessels, and appear to end adjacent to endothelial cells which demonstrate vesicular activity. The observations suggest terminal nerve neurosecretion into the cerebral circulation. Synapses are found in and near the ganglia where they appear to be axodendritic, with multiple contacts in s

ISSN:0092-7317    

DOI:10.1002/cne.902780411

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

年代:1988

数据来源: WILEY