摘要:

AbstractThe dorsal column nuclear complex, one of the most important relays for tactile perception, has well been known to be somatotopically organized. Topographical arrangements of terminal sites of individual cutaneous nerves within the dorsal column nuclei, however, have not been examined systematically, although many studies have been done upon primary afferents to the medulla oblongata, including the dorsal column nuclear complex. Thus, in the present study, distribution of primary afferent fibers projecting from the hindlimb cutaneous nerves to the medulla oblongata was examined in the cat and rat by means of the transganglionic transport method with horseradish peroxidase. Cutaneous primary afferent fibers projecting from the hindlimb to the medulla oblongata were distributed mainly in the ipsilateral gracile nucleus. Terminal labeling in the gracile nucleus was seen at all rostrocaudal levels of the nucleus, occasionally including the nuclear part straddling the midline (the median or accessory nucleus). The labeled axon terminals in the gracile nucleus were more densely distributed in the middle and caudal parts of the nucleus than in the rostral part. Although the fields of termination of the hindlimb cutaneous nerves overlapped in the gracile nucleus, the foci of the terminal labeling of the nerves innervating the distal parts of the hindlimb were located more medially or dorsomedially than those of the nerves innervating the proximal parts. Terminal labeling was further found in a small zone immediately medial to the rostromedial border of the external cuneate nucleus. This hitherto undescribed zone (U zone) contained a small cluster of medium‐sized neurons in the cat. Although no particular cell cluster was found in the U zone of the rat, convergence of the primary afferent fibers of the cutaneous nerve from the hindlimb appeared to occur as in the U zone of the ca

ISSN:0092-7317    

DOI:10.1002/cne.903410202

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

年代:1994

数据来源: WILEY

摘要:

AbstractThis study examines dendrites from physiologically characterized and intracellularly labelled thalamocortical projection (TCP) neurons from the rat ventrobasal complex (VB) and posterior nucleus (POm). The goals were to provide quantitative descriptions of TCP neuron dendrites, examine underlying design principles of dendritic morphology, and determine correlations between dendritic size parameters. Forty‐four dendrites from seven VB neurons and 21 dendrites from three POm TCP neurons that responded to low‐threshold mechanical stimuli were reconstructed and quantitatively analyzed at the light microscopic level. The dendritic architecture of the neurons was remarkably similar in most parameters studied, including the percentage of dichotomous branching, contribution of terminal branches to total dendritic length, and branching symmetry. There was a positive correlation between stem dendrite diameter and the length of the entire dendrite arbor, making it possible to estimate the total length of a dendritic arbor by measuring the stem dendrite diameter. The correlations of the VB and POm dendrites had different slopes. The path distance (the distance from the soma to a dendritic end point) of individual dendrites showed only a small variation with large differences in the total dendritic length of an arbor. The constant diameter of distal dendrites shows that dendrite diameter is a poor predictor of synaptic location on the dendritic tree.Although the morphology of neurons and their individual dendrites varied considerably in overall size and qualitative appearance, when examined qualitatively, many aspects of dendritic structure were similar within and between groups. We suggest that the rat somatosensory TCP neurons have a stereotyped dendritic architecture and present data which provide a base for future comparative, developmental, and plasticity stud

ISSN:0092-7317    

DOI:10.1002/cne.903410203

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

年代:1994

数据来源: WILEY

摘要:

AbstractLivingLimulusventral photoreceptor cells were injected with long chain lipophilic carbocyanine fluorescent dyes to label the endoplasmic reticulum (ER). The purpose of this study was to examine the continuity, dynamic changes, and structure of the ER in the living cell, using laser scanning confocal microscopy and three‐dimensional image reconstruction.In this highly polarized neuron, three lines of evidence indicate that the ER is a continuous network extending throughout both lobes of the cell. First, injection of DiO or DiI results in the labeling of ER throughout both lobes of the cell. Second, three‐dimensional image reconstruction of the optical sections reveals a dispersed membrane meshwork which may be the structure that serves to interconnet the ER in the two lobes. Third, in cells fixed before dye injection, the pattern of labelling was similar to that in living cells, indicating that vesicle transport was not responsible for the spread of dye throughout the cell.The overall organization of the ER in the photoreceptor cell is relatively stable; however, the fine structure changes over time. This dynamic process appears to represent continual reorganization of the intracellular membranes in the cell.Three morphological types of ER were observed. The ER of the light‐sensitive lobe, identified by coinjection of rhodamine‐phalloidin to label the microvillar actin, is characterized by a concentration of stratiform membranes interconnected by thin tubular cross‐bridges. The perinuclear ER is characterized by a tangle of convoluted tubules sometimes terminating in bulbous structures. Finally, there is a fine tubular reticulum dispersed throughout

ISSN:0092-7317    

DOI:10.1002/cne.903410204

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe study of Golgi‐impregnated lizard brains has revealed a scarce but heterogeneous neuronal population in the outer plexiform layer of the medial cortex. Some of the neuronal types detected here resemble the neurons of the dentate molecular layer of the mammalian hippocampus.According to their morphology, five intrinsic neuronal types have been clearly identified: short axon aspinous bipolar neuron (type 1, or sarmentous neuron), short axon aspinous juxtasomatic neuron (type 2, or coral neuron), short axon sparsely spinous multipolar neuron (type 3, or stellate neuron), short axon sparsely spinous juxtasomatic multipolar neuron (type 4, or deep stellate neuron, and sparsely spinous juxtasomatic horizontal neuron (type 5, or couchant neuron).Most neuronal types were identified as γ‐aminobutyric acid (GABA) and parvalbumin immunoreactive, and are thus probably involved in medial cortex inhibition. Moreover, a small fraction of them displayed ß‐endorphin immunoreactivity.The distribution of these neuronal types is not uniform in the laminae of the outer plexiform layer. Type 1 (sarmentous) and type 3 (stellate) neurons overlap the axonal field projection coming from the dorsal cortex and the thalamus, whereas types 4 (deep stellate) and 5 (couchant) neurons overlap ipsi‐ and contralateral dorsomedial projection fields as well as raphe serotoninergic and opioid immunoreactive axonal plexi. Thus, these neuronal types may be involved in the control of specific inputs to the medial cortex by presumably feed‐forward inhibition; nevertheless, feed‐back inhibition may also occur regarding type 4 (deep stellate) neurons that extend deep dendrites to the zinc‐ri

ISSN:0092-7317    

DOI:10.1002/cne.903410205

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

年代:1994

数据来源: WILEY

摘要:

AbstractDevelopment and maintenance of peripheral sensory and sympathetic neurons are regulated by target‐derived neurotrophins, including nerve growth factor (NGF). To determine whether trophins are potentially critical prior to and during target innervation, for neuronal survival or axon guidance, in situ hybridization was performed in the rat embryo. We examined the expression of genes encoding NGF, neurotrophin‐3 (NT‐3), and their putative high‐affinity receptors, trk A and trk C, respectively. Trks A and C were detected in dorsal root sensory ganglia (DRG) on embryonic day 12.5 (E12.5), implying early responsiveness to NGF and NT‐3. NGF mRNA was expressed in the central spinal cord target and by the peripheral somite, at this early time, which thereby may function as a transient “guidepost” target for sensory fibers. Somitic expression was transient and was undetectable by E17.5. NT‐3 was expressed in the DRG itself from E13.5 to 17.5, suggesting local transient actions on sensory neurons. NT‐3 was also expressed in the ventral spinal cord at low levels on E13.5. We examined the trigeminal ganglion to determine whether cranial sensory neurons are similarly regulated. Trk A was detected in the trigeminal ganglion, while NGF was expressed in the central myelencephalon target, paralleling observations in the DRG and spinal cord. However, NT‐3 and trk C were undetectable, in contrast to DRG, suggesting that the environment or different neural crest lineages govern expression of different trophins and trks. Apparently, multiple trophins regulate sensory neuron development through local as well as transient target mechanisms prior to innervation of

ISSN:0092-7317    

DOI:10.1002/cne.903410206

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

年代:1994

数据来源: WILEY

摘要:

AbstractEarlier studies have shown that retinohypothalamic projections terminate extensively within the hypothalamus of the rat. Recently, we identified a light retinal projection to the supraoptic nucleus as well as a larger, well‐focused projection resulting in a peri‐supraoptic nucleus terminal field. In this study, we employed a double labeling method with cholera toxin conjugated to horseradish peroxidase (CT‐HRP) and pseudorabies virus, a transsynaptic neural tracer, to evaluate retinorecipient neurons in both the supraoptic nucleus and peri‐supraoptic nucleus terminal field. In addition, we looked for evidence that cells in the peri‐supraoptic nucleus terminal field project into the supraoptic nucleus. Three strains of pseudorabies virus were compared. A direct retinosupraoptic nucleus circuit was confirmed with all three strains. Retinorecipient neurons in the peri‐supraoptic nucleus terminal field were also confirmed. However, there was a strain‐based difference in the identification of these neurons. The wild‐type Becker strain labeled cells in the peri‐supraoptic nucleus terminal field in a manner paralleling the early, intermediate and late stages of infection of the suprachiasmatic nucleus. This parallel time course suggests that retinal ganglion cells terminate directly on cells in the peri‐supraoptic nucleus terminal field. Conversely, the Bartha and PRV‐91 strains showed appreciable labeling of peri‐supraoptic neurons only at long survival times. This longer time course suggests that these mutant strains label neurons in the peri‐supraoptic nucleus terminal field indirectly, after passing through additional neurons. In addition, experiments with monocular injection of CT‐HRP and posterior pituitary injection of pseudorabies virus showed retrogradely labeled second‐order cells in the peri‐supraoptic nucleus amidst the CT‐HRP labeled terminal field of the retinohypothalamic tract. These results demonstrate a direct projection from the retina to the supraoptic nucleus and provide evidence for an indirect circuit from the retina to the supraoptic nucleus via neurons located in the peri‐supraoptic nucleus terminal field. The strain‐based differences imply that those retinal ganglion cells that project to the peri‐supraoptic nucleus terminal field differ from those that project to the supra‐chiasmatic nucleus. In addition, these results suggest a neuroanatomic basis for photic effects on physiological mechanisms that are no

ISSN:0092-7317    

DOI:10.1002/cne.903410207

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

年代:1994

数据来源: WILEY

摘要:

AbstractAn antiserum raised against locustatachykinin I, one of four myotropic peptides that have been isolated from the locust brain and corpora cardiaca, was characterized by enzyme‐linked immunosorbent assay (ELISA) and used for immunocytochemical detection of neurons and endocrine cells in the nervous system and intestine of the blowflyCalliphora vomitoria.The ELISA characterization indicated that the antiserum recognizes the common C‐terminus sequence of the locustatachykinins I‐III. Hence, the cross reaction with locustatachykinin IV is less, and in competitive ELISAs no cross reaction was detected with a series of vertebrate tachykinins tested. It was also shown that the antiserum recognized material in extracts of blowfly heads, as measured in ELISA. In high‐performance liquid chromatography the extracted locustatachykinin‐like immunoreactive (Lom TK‐LI) material eluted in two different ranges. A fairly large number of LomTK‐LI neurons was detected in the blowfly brain and thoracicoabdominal ganglion. A total of about 160 LomTK‐LI neurons was seen in the proto‐, deuto‐, and tritocerebrum and subesophageal ganglion. Immunoreactive processes from these neurons could be traced in many neuropil regions of the brain: superior and dorsomedian protocerebrum, optic tubercle, fan‐shaped body and ventral bodies of the central complex, all the glomeruli of the antennal lobes, and tritocerebral and subesophageal neuropil. No immunoreactivity was seen in the mushroom bodies or the optic lobes. In the fused thoracicoabdominal ganglion, 46 LomTK‐LI neurons could be resolved. The less evolved larval nervous system was also investigated to obtain additional information on the morphology and projections of immunoreactive neurons. In neither the larval nor the adult nervous systems could we identify any efferent or afferent immunoreactive axons or neurosecretory cells. The widespread distribution of LomTK‐LI material in interneurons suggests an important role of the native peptide(s) as a neurotransmitter or neuromodulator within the central nervous system. Additionally a regulatory function in the intestine is indicated by the presence of immunoreactivity in endo

ISSN:0092-7317    

DOI:10.1002/cne.903410208

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

年代:1994

数据来源: WILEY

摘要:

AbstractSince ischemic damage in the brain is linked to glutamate excitotoxicity, the effects of an acute exposure to glutamate, α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole proprionic acid (AMPA) or N‐‐methyl‐D aspartate (NMDA) on the radial dendrites were compared with these occurring after a severe cochlear ischemia. Glutamate and AMPA, but not NMDA, produced a drastic swelling restricted to the radial dendrites below the inner hair cells (IHCs). At a concentration of 20 μM AMPA, a full electrophysiological recovery could be observed in some cochleas after washing the drug out. A prior perfusion of 6‐7‐dinitroquinoxaline‐2,3‐dione (DNQX, 50 μM) prevented the 25 μM AMPA‐induced dendritic swelling. No protective effect of D‐2‐amino‐5‐phosphonopentanoate (D‐AP5) could be observed. In the same way, ischemia (5‐40 minutes) resulted in a clear swelling of the radial dendrites. While D‐AP5 had no protective effects, 50 μM DNQX protected most of the radial dendrites from the ischemia‐induced swelling, excepting those contacting the modiolar side of the IHCs. Finally, 50 μM DNQX + 50 μM D‐AP5 resulted in a nearly complete protection of all the radial dendrites. Altogether, these results suggest that the acute swelling of radial dendrites primarily occurs via AMPA/kainate receptors. However, in radial dendrites contacting the inner hair cells on th

ISSN:0092-7317    

DOI:10.1002/cne.903410209

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

年代:1994

数据来源: WILEY

摘要:

AbstractIn this study, antiserum raised against an insect myotropic peptide, leucokinin I (DPAFNSWGamide), was: used for mapping leucokinin‐like immunoreactive (LK‐LI) neurons in the gastropod mollusc,Helix pomatia.Immunocytochemistry performed on both whole‐mounts and cryostat sections demonstrated LK‐LI neurons in all ganglia of the central nervous system (CNS), except the visceral ganglion. Altogether about 700 immunolabelled neurons have been found, with nearly one‐half (46%) in the cerebral ganglia. A large proportion of the LK‐LI neurons have small cell bodies and are likely to be interneurons. The most prominent LK‐LI cell group is represented by the entire neuron population of the mesocerebri, which is the major source of a thick fiber bundle system, encircling and innervating the whole CNS. One single LK‐LI giant neuron was found, which is located in the left pedal ganglion and is termedGLPdLKC(giant left pedal leucokinin immunoreactive cell). This cell has not been identified previously. The ganglion neuropils are heavily innervated by varicose LK‐LI fiber arborizations. Some integrative centers, such as the medullary neuropil of the procerebri, reveal an extreme density of LK‐LI innervation. All major peripheral nerves contain a large number of LK‐LI axons, and LK‐LI innervation is found in the musculature of different peripheral organs (buccal mass, lip, tentacles, oviduct, intestine). Among the peripheral organs investigated, the intestine contains a rich varicose LK‐LI network, composed of both intrinsic and extrinsic elements. Radioimmunoassay (RIA) demonstrates a very high content of LK‐LI material inHelixganglion extracts (about 50 pmol/CNS). This is the first report on the occurrence of a substance resembling the myotropic neuropeptide leucokinin I in a phylum outside arthropods. Based on our immunocytochemical observations, a role for leucokinin‐like peptides in both central and peripheral regulatory processes inHelixis suggested. According to double‐labelling experiments, only a small number of the LK‐LI neurons are labelled with an antibody to the

ISSN:0092-7317    

DOI:10.1002/cne.903410210

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

年代:1994

数据来源: WILEY

摘要:

AbstractWe have studied the organization of gamma‐aminobutyric acid (GABA)ergic profiles in the superior colliculus of the rabbit to determine whether the synaptic types found in cat and monkey also exist in a mammalian species whose visual system has a different organization. Ultrastructure of GABAergic profiles was examined by use of a polyclonal antibody to GABA and quantitative postembedding immunocytochemistry.Three distinct types of vesicle‐containing profiles were labeled by the GABA antibody in the rabbit superior colliculus. One type was a putative presynaptic dendrite (PSD profile) that received synaptic input from other profiles and contained pleomorphic synaptic vesicles scattered throughout the profile. These PSD profiles frequently received retinal input and formed dendrodendritic synapses. A second type of profile was a large caliber dendrite, often horizontal in orientation (H profile), that had one or more discrete clusters of pleomorphic synaptic vesicles at sites of synaptic contact with conventional dendrites. These H profiles received few synaptic contacts. A third profile type was a putative axon terminal (F profile) with smaller, more flattened synaptic vesicles that densely and uniformly filled the profile. Quantitative analysis of gold particle density revealed that F profiles had a significantly higher gold particle density (14.3/ μm2) than did PSD or H profiles (10.4 and 10.2/ μm2), suggesting that GABAergic profile types contain different concentrations of GABA. The vesicle density of these profile types also differed, but no obvious relationship between vesicle and particle distributions was observed. We conclude that the profiles labeled by GABA in rabbit superior colliculus are similar to those in cat and monkey and must represent a phylogenetically conserved organization common to many mammals, and that particle density analysis of postembedding immunocytochemistry can distinguish different GABAergic profile

ISSN:0092-7317    

DOI:10.1002/cne.903410211

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

年代:1994

数据来源: WILEY