ISSN:0092-7317    

DOI:10.1002/cne.903050102

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe fine structure and synaptic architecture of the afferent terminations in dorsal horn lamina II are studied using a combined light and electron microscopic procedure after anterograde labelling with horseradish peroxidase. Vibratome parasagittal sections, stained with heavy metal intensified diaminobenzidine after tracer application to the dorsal roots, were flat‐embedded in Epon. The five types of labelled terminal arbors occurring in lamina IIi (Cruz et al., '87:J. Comp. Neurol. 261:221–236) were drawn and relocated in 5‐μm sections cut serially from the thick sections. Ultrathin sections were then cut from the 5‐μm sections so that the terminal fibers and swellings observed in the light microscope could be traced in the electron microscope. Theflame‐shaped arborsarose from fine myelinated stem fibers. Terminal strands generated large oval central terminals of type II synaptic glomeruli (CII), which established frequent axoaxonal contacts. Similar terminals have been labelled in the cat after tracer injections into hair‐follicle fibers (Réthelyi et al., '82:J. Comp. Neurol. 207:381–393). The other four plexuses arose from unmyelinated stem fibers. Theswarms of ultrafine boutonsconsisted of extremely thin terminal fibers generating very small, round, or polygonal glomerular terminals containing tightly packed agranular synaptic vesicles of variable size and one mitochondrion at best. The terminal strands of thebouquet plexusbore long and scalloped central varicosities of type I synaptic glomeruli (CI) with pleomorphic agranular vesicles and a relative abundance of dendroaxonal contacts. These features, together with the location in dorsal lamina IIi, suggest their belonging to the fluoride resistant acid phosphatase (FRAP)‐reactive population. The boutons of theundulating fibersand those of thelateral plexuswere, like those of the bouquets, scalloped and elongated rostrocaudally (CI), but contained a few large granular vesicles. The occurrence of the swarm, undulating, and lateral plexuses in ventral lamina IIi, which seems to lack FRAP or peptidergic terminals, suggests an origin from other, still unidentified neurochemical populations of fine

ISSN:0092-7317    

DOI:10.1002/cne.903050103

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe distribution of axons arising from the central complex (or centre médian‐parafascicular complex) and terminating in the striatum was studied in seven macaques and one squirrel monkey. Deposits of anterograde tracers were made in the two lateral‐most subdivisions of the central complex, i.e., the middle part (or pars media) and the lateral part (or pars paralateralis). All injections avoided the pars parafascicularis. The intrastriatal distribution of labeled axonal endings was mapped in relation to the standard ventricular (CA‐CP) system of coordinates. Labeled endings were observed in the major posterior and dorsal parts of the putamen (excluding its anteromedial and ventral parts) and also in a restricted ventrolateral part of the caudate nucleus. The topography of the central territory of the striatum, denned as the striatal space receiving axons from the central complex, was found to correspond exactly to that of the cortical sensorimotor territory delineated after cortical injections. The termination pattern of the central axons within the striatum was patchy. Viewed as a whole, the irregular and hazy patches formed oblique streaks, parallel one with the other. The three‐dimensional reconstructions of data from transverse sections revealed that the streaks were bi‐dimensional pictures of three‐dimensional parasagittal layers covering the whole anteroposterior extent of the cortical sensorimotor territory of the striatum. Our work shows that the pars media of the central complex, which receives selectively pallidal afferent axons (Francois et al., '88:Brain Res. 473:181–186), is the main source of the centroputaminal projection. The probable implication of this in a closed sensorimotor loop of the basal gangli

ISSN:0092-7317    

DOI:10.1002/cne.903050104

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThis report focuses on a class of large synaptic endings, the endbulbs of Held. These endings are located in the anteroventral cochlear nucleus and arise from the axons of type I spiral ganglion neurons. Axons were stained with horseradish peroxidase (HRP) using intracellular injections of single fibers or extracellular injections into the auditory nerve. Individual endbulbs or pairs of endbulbs that converged onto the same spherical bushy cell were examined with the aid of a light microscope and subjected to morphometric analyses. Endbulbs of fibers having low spontaneous discharge rates (SR, ≤ 18 spikes/sec) have a more complex shape than those of high SR fibers (>18 s/s), a feature represented by systematic differences in endbulb silhouette perimeter without differences in endbulb silhouette area. Consequently, the ratio, silhouette area divided by silhouette perimeter, yields a “form factor” separating endbulbs of high SR from those of low SR. High SR fibers had ratios>0.52 (mean = 0.63 ± 0.09), whereas low SR fibers had ratios<.52 (mean = 0.45 ± 0.06). Pairs of endbulbs with unknown physiological properties had similar form factor values, despite the wide range of values observed in the endbulb population. These data imply that endbulbs converging upon the cell body of a spherical bushy cell arise from fibers of the same SR group.Electron microscopic examination was conducted on the endbulb of one physiologically characterized and intracellularly stained auditory nerve fiber (CF = 1.4 kHz; SR = 55 s/s) and its unstained endbulb mate with the aid of serial ultrathin sections. In addition to the well‐known axosomatic synapses, these endbulbs formed axodendritic synapses: 11.7% for the HRP‐labeled endbulb and 13.3% for the unlabeled endbulb. The axodendritic synapses appear to occur on dendrites of nearby spherical bushy cells and may represent a mechanism whereby single endbulbs can disperse activity to multiple neurons in the cochlear nucleus. We propose that axosomatic synapses preserve fiber SR groupings, whereas axodendritic synap

ISSN:0092-7317    

DOI:10.1002/cne.903050105

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractYoung rats learn to approach an odor that had been experienced in the presence of reinforcing tactile stimulation. Subsequent presentation of the conditioned odor also evokes an enhanced focal uptake of 2‐deoxyglucose (2‐DG) in the glomerular layer of the olfactory bulb, and the glomerular‐layer width of such foci increases in conditioned pups. In the present study, we determined whether an increase in the glomerular‐layer cell population contributes to this structural and functional change. We therefore counted and measured glomerular‐layer cells in Nissl‐stained sections from focal regions of radiolabeled 2‐DG uptake. While cell size did not differ between groups, conditioned pups had a 19% increase in the number of glomerular‐layer cells associated with the 2‐DG foci compared to controls. The increase in cell number may contribute to the enhanced 2‐DG uptake in gl

ISSN:0092-7317    

DOI:10.1002/cne.903050106

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe retinal afferents of the tectum opticum and the n. opticus principalis thalami (OPT) were studied with fluorescent tracers in pigeons. Injections into the tectum opticum revealed topographically related areas of high density labelling in the contralateral retina. In these areas up to 15,000 cells/mm2were labelled. After tectal injections the soma sizes of labelled retinal ganglion cells in the area centralis ranged from 5 to 23 μm with a mean of 7.5 μm. Afferents from the ipsilateral retina could not be demonstrated. Injections into the OPT labelled neurons throughout the retina without a clear topographical relation to the locus of injection. The density never exceeded 150 cells per mm2. The soma size range was 8 to 35 μm with a mean of 14.6 μm. Independently of the injection area within the OPT, the red field in the dorsotemporal retina was always extremely sparsely labelled. The number of labelled ganglion cells in this area never exceeded 25 neurons/mm2. After OPT injections the average density of labelling per unit area was six times higher in the yellow than in the red field. The results confirm previous reports of a massive and topographically organized retinal projection onto the optic tectum. The projection onto the OPT was clearly smaller and with the retrograde tracing techniques in use, an orderly topography has not been demonstrated. The paucity of red field projections onto the OPT suggests that the role of the thalamofugal pathway in binocular integration is very limi

ISSN:0092-7317    

DOI:10.1002/cne.903050107

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe distribution of zinc has been described in two areas of the hippocampal region of the domestic pig, viz., the subiculum and the hippocampus. Zinc was demonstrated histochemically according to the Neo‐Timm method, a modification of the sulphide‐silver procedure. In each of the examined areas the staining displayed a distinctly stratified pattern which has been compared in detail to fields and layers defined on the basis of cyto‐ and fibroarchitecture, resulting in a combined chemo‐ and cytoarchitectonic map. Most of the staining was confined to the neuropil, but a considerable number of stained nerve cell bodies were seen in both the subiculum and the hippocampus.In the subiculum, the plexiform layer was divided into a superficial, weakly stained subzone and a deep, better stained subzone. The cell layer was generally well stained, but displayed a complex staining pattern with differences in staining intensity of both the cell bodies and neuropil. In regio superior of the hippocampus, the stratum moleculare appeared weakly stained, with the exception of a tapering process of more darkly stained tissue projecting from the plexiform layer of the subiculum into the deepest part of the layer. Stratum radiatum and the superficial subzone of stratum oriens showed a weak staining intensity, contrasting to the relatively darkly stained pyramidal cell layer and the intensely stained deep subzone of stratum oriens. In regio inferior, the stratum moleculare was divided into a moderately stained superficial part and an unstained deep part. Stratum radiatum and stratum oriens both appeared weakly stained. The layer of mossy fibers was very intensely stained and appeared almost homogeneously black in its main suprapyramidal part, whereas the infrapyramidal part was looser in character. The pyramidal cell layer was darker than in regio superior.The distribution of zinc in the pig was compared with that in the guinea pig and rat, described previously. The staining pattern is fundamentally similar in all three species, though notable species‐specific traits

ISSN:0092-7317    

DOI:10.1002/cne.903050108

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractFollowing the injection of horseradish peroxidase (HRP) into the brachial spinal cord of the chick on embryonic day (E)4.5, retrogradely labeled neurons can be found in the brainstem (Okado and Oppenheim:Journal of Comparative Neurology232:143–161, 1985). By contrast, following high cervical spinal transection, functional (behavioral) deficits are not observed until E10 (Oppenheim:Journal of Comparative Neurology160:37–50, 1975). To determine whether this temporal difference between projections and function reflects a delay in synaptogenesis, we looked for the presence of anterogradely HRP‐labeled pre‐synaptic terminals in brachial cord following injection of HRP into the boundary between brainstem and spinal cord at ages between E3.5 and E7. HRP‐labeled fibers were observed in the brachial cord by E4.5 and were diffusely distributed in the ventral and lateral marginal zones (presumptive ventral and lateral funiculi, respectively). Although some axo‐dendritic and axo‐somatic synapses were observed in the brachial cord prior to E6, the presynaptic profiles were always unlabeled by HRP and thus must originate from propriospinal sources. The first HRP‐labeled supraspinal synapses were found in the ventral and lateral funiculi on E6. They contained several clear spherical synaptic vesicles and were axo‐dendritic in nature. The cells of origin of the postsynaptic dendrites were determined by injecting HRP into the wing‐bud to label the brachial motoneurons retrogradely and the presynaptic component was identified as supraspinal by HRP injections into the brainstem/spinal cord boundary to orthogradely label the descending fibers. Several double‐labeled axo‐dendritic synapses were found in the ventral and lateral funiculi of E6 brachial cord. Therefore, at least some descending supraspinal fibers make synapses directly onto motoneuron dendrites. We conclude that (1) there is a delay of about 1.5 days between the arrival of supraspinal fibers and synapse formation in, the brachial cord, (2) the earliest synapses are axo‐dendritic in nature, (3) at least some supraspinal fibers make direct contact with motoneuron dendrites as early as E6, and 4) synaptogenesis from propriospinal sources precedes that from supraspinal descending axons. These observations provide evidence indicating that the temporal difference between the onset of projections of supraspinal descending fibers and the onset of their function may be partly owing

ISSN:0092-7317    

DOI:10.1002/cne.903050109

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe present study examined the distributions of connexin43 mRNA and connexin32 mRNA in the central nervous system (CNS) of the rat by using in situ hybridization histochemistry. These connexins are the best studied gap junction proteins; connexin32 forms direct cell‐cell channels in the liver, as does connexin43 in the heart. There was a differential distribution of cells containing connexin32 mRNA compared with the population of cells which contained connexin43 mRNA, thus implying a regional specificity in the expression of connexins in the CNS. Cells containing connexin43 mRNA were uniformly distributed throughout the gray matter of the neuraxis. Several areas had a higher concentration of cells that express connexin43, such as layer IA of the piriform cortex, supraoptic and paraventricular nuclei of the hypothalamus, anterior cortical amygdaloid nucleus, the reticular part of the substantia nigra, lateral habenula, mesencephalic trigeminal nucleus, Purkinje cell layer of the cerebellum, facial nucleus, prepositus hypoglossal nucleus, and dorsal cochlear nucleus. The pattern of connexin43 hybridization and the morphology of connexin43 mRNA containing cells suggest that this gap junction forming protein is found predominantly in astrocytes, Con‐nexin32 mRNA was detected in discrete cell groups of the gray matter that appeared to be neurons, including cells in layer 2 of the neocortex, layer II of the piriform cortex, pyramidal cell layer of the hippocampus, granule and polymorphic cell layers of the dentate gyrus, islands of Calleja, olfactory tubercle, lateral thalamic nuclei, lateral habenula, and Purkinje cell layer of the cerebellar cortex. A large population of cells in white matter tracts that were labelled with the connexin32 riboprobe appeared to be oligodendrocytes. These studies suggest that neurons and glial cells express connexin32 mRNA, but only astrocytes express connexin43 mRNA. Many of the areas in which connexin mRNAs were demonstrated have electrically coupled cells, morphologically distinct gap junction plaques, and/or have immunocytochemically identifiable connexin proteins. These results indicate that cells with mRNAs coding for intercellular channels have a widespread distribution in the mammalian

ISSN:0092-7317    

DOI:10.1002/cne.903050110

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractAromatic L‐amino acid decarboxylase (AADC), the enzyme that converts L‐dopa to dopamine, displayed species‐specific differences in both activity and immunoreactivity in the cerebellum, olfactory bulb, and adrenal glands of three rodent species, the hamster, rat, and mouse. Specifically, in the hamster but not the rat or mouse, AADC immunoreactive cells were observed in the cerebellum and adrenal cortex. The unusual distribution of the enzyme was confirmed biochemically. AADC activity was greater in the adrenal gland and the cerebellum in the hamster than in the mouse or rat. In addition, by Western blot analysis, one band of appropriate molecular weight was observed both in the hamster adrenal gland and cerebellum. The rat adrenal gland displayed a similar immunoreactive protein on the Western blot; however, the protein could not be detected in the rat cerebellum by the technique utilized. Tyrosine hydroxylase (TH) immunoreactivity in these same tissues did not differ among the species. In the main olfactory bulb of the mouse, juxtaglomerular cells exhibited very limited immunoreactivity for AADC, but TH‐immunoreactivity in these cells was robust. In contrast, juxtaglomerular cells in the rat displayed a similar intensity of immunostaining for both AADC and TH. AADC activity in the mouse, consistent with the reduced immunostaining for the enzyme, was 50% of that in the rat and the hamster. These data demonstrate that AADC protein, which is contained in cells of diverse function, also displays qualitative and quantitative species specific variations in both distribution and

ISSN:0092-7317    

DOI:10.1002/cne.903050111

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY