摘要:

AbstractThe distributions and laminar densities of cerebral cortical dopamine D‐1 and D‐2 receptors were studied in rats, cats, and monkeys. Distributions were determined by using alternate, adjacent tissue sections processed for D‐1 and D‐2 receptor subtypes and compared to an adjacent, nearly adjacent, or similar sections stained for Nissl substance. [3H]‐SCH 23390 and [3H]‐spiroperidol (in the presence of 100 nM mianserin) were used to label the D‐1 and D‐2 receptors, respectively. The regional distribution and laminar density of dopamine receptors were determined by in vitro quantitative autoradiography and video densitometry of selected isocortical and peri‐allocortical regions. Granular (prefrontal, primary somatosensory, and primary visual), agranular (primary motor and anterior cingulate), and limbic (entorhinal and perirhinal) cortices were examined. Where possible, homologous areas among the species were compared.The D‐1 receptor was present in all regions and laminae of the cerebral cortex of rats, cats, and monkeys. The regional densities for the D‐1 receptor were higher in the cat and monkey than in the rat. The rat D‐1 receptor displayed a relatively homogeneous laminar pattern in most regions except that the deeper laminae (V and VI) contained more receptors than the superficial layers. The cats and monkeys, however, had distinctly heterogeneous laminar patterns in all regions of cortex that varied from one region to another and were quite different from that seen in the rat. The cats and monkeys had highest densities of the D‐1 receptor in layers I and II and lowest densities in layers III and IV, whereas layers V and VI were intermediate. The density of D‐1 receptors was greater than the density of D‐2 receptors in all regions and laminae of cerebral cortex of the cat and monkey and greater in most regions and laminae of the rat cerebral cortex.The D‐2 receptor was also distributed in all regions of the cerebral cortex of rats, cats, and monkeys. The D‐2 receptor was very homogeneous in its regional distribution and laminar pattern compared to the D‐1 receptor in all 3 species. The D‐2 receptor was denser in the superficial layers (I and II) of the cortex than in the deeper layers in the rats, but more homogeneous in the different laminae of the cat and monkey cerebral cortex. The rat cortical D‐2 receptor exceeded the D‐1 receptor in restricted laminae of selective regions.Kittens demonstrated low densities of both D‐1 and D‐2 receptors in the cerebral cortex. The kitten D‐1 receptor was more homogeneous in its laminar distribution than in similar regions of the adult cat. The increase in D‐1 receptor density and changes in laminar patterns suggest that portions of the cerebral cortical dopamine system may undergo significant changes during development.The distribution and density of dopamine receptors in this study agrees well with recent data on the cerebral cortical innervation of the dopamine system in different mammals. The density of dopamine receptors parallels the dopaminergic regional and laminar innervation in rats and monkeys (and presumably cats). Both the degree of innervation and the receptor density are greater in monkeys (and presumably cats) compared to rats. There are some differences in the patterns and degree of matching between dopamine innervation and dopamine receptors, which may reflect differences in the sensitivity or specificity of the different techniques or a true mismatch between them.These results support and extend the notion that the dopamine system has a more widespread role in cerebral cortical function in all mammals than was previously suspected. The high density, variability in laminar density, and regional differences of the D‐1 receptor in cats and monkeys suggest that the dopamine system, especially the D‐1 receptor, may be more involved in higher cor

ISSN:0092-7317    

DOI:10.1002/cne.902860402

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe distribution of cortical cells projecting to the pontine nuclei in rats was studied by making large injections of horseradish peroxidase that filled the basilar pons and measuring the density of labelled cells in each cortical area. All retrogradely labelled cells were layer V pyramidal cells. The highest densities of labelled cells were observed in the motor areas. The lowest densities were in temporal association cortex and perirhinal cortex. Visual cortical areas, including the primary visual cortex, provided a major source of pontine projections. The distribution of corticopontine cells within the primary visual cortex was studied in more detail. In all cases the highest density of labelled cells was observed in the region of cortex that represents the nasal visual field. Control injections into brainstem regions adjacent to the pontine nuclei produced a much lower absolute density of retrogradely labelled cortical cells and the distribution of those cells was different from that observed following pontine injections. We conclude that every area of the rat's cerebral cortex projects to the pontine nuclei and that there are consistent variations in the density of the projections both between and within areas.

ISSN:0092-7317    

DOI:10.1002/cne.902860403

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractQuantitative anatomical investigations provide the basis for functional models. In this study the density of neurons and synapses was measured in three different areas (8, 6, and 17) of the neocortex of the mouse. Both kinds of measurements were made on the same material, embedded in Epon/Araldit. In order to determine the synaptic density per mm3, the proportion of synaptic neuropil was also measured; it was found to be 84%. The cortical volume occupied by cell bodies of neurons and glia cells amounted to 12%, that by blood vessels to 4%.The total average was 9.2 × 104neurons/mm3and 7.2 × 108synapses/mm3. About 11% of the synapses were of type II. The density of neurons increased with decreasing cortical thickness; thus the number of neurons under a given surface area was about constant. The synaptic density, on the other hand, was almost constant in the three areas, the number of synapses under a given cortical surface area tended, therefore, to increase with cortical thickness. The average number of synapses per neuron was 8,200, with a tendency to increase with increasing cortical thickness.Shrinkage of the tissue was also measured for various staining techniques. No shrinkage occurred during perfusion with 3.7% formaldehyde or with a solution of buffered paraformaldehyde and glutaraldehyde and during fixation in situ. Electron microscopical material showed almost no shrinkage, whereas Nissl‐preparations on paraffin‐embedded material had only 43% of their original volume. After Nissl stain on frozen sections the volume had shrunken to 68% and after Golgi impregnation and embedding in celloidin to 70%. The total volume of the neocortex was 112 mm3(both hemispheres together). The total number of neurons was thus 1.0 × 107and the total number of synapses 8.1

ISSN:0092-7317    

DOI:10.1002/cne.902860404

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe distribution and time course of γ‐aminobutyric acid (GABA) immunoreactivity was investigated in the cranium of the chick embryo from 2 to 16 days of incubation (E2–16). A fraction of nerve fibers transiently stains GABA‐positive in all cranial motor nerves and in the vestibular nerve. Cranial motor nerves stain GABA‐positive from E4 to E11, including neuromuscular junctions at E8–11; labeled fibers are most frequent in the motor trigeminal root (E6–9.5). Substantial GABA staining is present from E4 to E10 in a subpopulation (1–2%) of vestibular ganglion cells. Their peripheral processes are labeled in the vestibular endorgan, predominantly in the posterior crista. Some GABA‐positive fibers are present in the olfactory nerve (after E5) and in the optic nerve (after E9.5); their immunoreactivity persists throughout the period investigated. Transient GABA immunoreactivity follows “pioneer” fiber outgrowth and coincides with the formation of early synaptic contacts.GABA‐containing neurons may change their neuronal phenotype (loss of GABA expression) or they may be eliminated by embryological cell death. Periods of cell death were determined in cranial ganglia and motor nuclei by aggregations of pycnotic cells in the same embryonic material. The periods of embryonic cell death partly coincide with transient GABA immunoreactivity. The function(s) of transient GABA expression is unknown. Some lines of evidence suggest that GABA has neurotrophic functions in developing cranial nerves or their target tissue. In the developing neuromuscular junction, GABA may be involved in the regulation of a

ISSN:0092-7317    

DOI:10.1002/cne.902860405

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe combined Golgi/electron microscope (EM) technique was used to analyze the fine structure and synaptic organization of the various types of neurons in the rat lateral septum (LS), i.e., in the dorsolateral (LSd), intermediolateral (LSi), and ventrolateral (LSv) nuclei of the septal complex.Two characteristic cell types were observed in the LSd: type I with thick, short dendrites densely covered with short spines, and type II with longer and thinner dendrites exhibiting fewer but longer spines. This latter type was by far the most frequently impregnated cell type in the LSd and was also present in the LSi. Synaptic contacts on spines of either cell type were asymmetric; the majority of the presynaptic boutons contained clear and dense‐core vesicles. Typical fusiform neurons with a low number of spines and rather long dendrites, sometimes invading other LS nuclei, were found in the LSi. The LSv contained numerous small neurons with small dendritic fields. A relatively large number of terminals with dense‐core vesicles were found to establish synaptic contacts with identified LSv neurons.The morphological heterogeneity of LS neurons is discussed with regard to other studies on afferent and efferent fiber systems as well as immunohistochemical studies of this particular region of the septal comp

ISSN:0092-7317    

DOI:10.1002/cne.902860406

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe objective of this study is to define the development of all components in the chick embryonic trigeminal primary sensory‐motor complex, from their first appearance through the formation of central and peripheral axonal projections up to stage 34 (8 days of incubation). This was accomplished by two labeling procedures: application of the monoclonal antibody HNK‐1, which binds to the precursors of all these components except the placode‐derived neurons, and application of HRP to axons cut immediately distal to the trigeminal ganglion.Single immunopositive motor neuron precursors are present at stage 12. These accumulate in the transient medial motor column, whose neurons initiate axon outgrowth by stage 13–14, concomitant with the onset of translocation of their somata to form the definitive trigeminal lateral motor column (LMC). Intiially these translocating somata accumulate on the medial margin of the LMC. Beginning on incubation day 5, axons growing from newly formed motor neurons pass beside the lateral margin of the LMC, and the nuclei of these cells subsequently follow this pathway. These events follow a rostral‐to‐caudal sequence, and this phase of motor nucleus formation is complete by day 8. The lateral translocation of some caudally located nuclei is arrested beginning on day 5. This cessation, which proceeds rostrally, demarcates neurons that form the dorsal motor nucleus of the trigeminal complex.Sensory neurite formation is intiated in ophthalmic placode‐derived cells at stage 14.5, one stage later by maxillomandibular neurons, and from mesencephalic V cells at stage 15. Neural crest cells do not initiate axon formation until at least day 4 to 5. Following application of HRP distal to the condensing ganglion at stage 16, labeled ophthalmic nerve projections appear in contact with the wall of the hindbrain centrally and overlying the optic vesicle peripherally. Fibers forming the descending tract elongate rapidly, reaching the level of the VIIth nerve root (200 m̈m caudal to the trigeminal root) by stage 18 and the cervical cord by stage 22. Labeled terminal arborizations of descending trigeminal afferents are first visible at stage 22 and are evident along the entire descending and proximal ascending tracts by stage 27. Later‐developing descending axons grow in close association with existing trigeminal fibers, though a few growth cones are consistently evident superficial to the other fibers. No projections different from those reported in adult birds are seen, nor are there any contralateral afferent projections.Peripheral axons from neurons in the mesencephalic trigeminal nucleus emerge from the trigeminal ganglion beginning at stage 21. These cells are labeled only when tracer is applied to the

ISSN:0092-7317    

DOI:10.1002/cne.902860407

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe prenatal development of the rabbit's retinal projections to the superior colliculus (SC) was studied by using anterograde transport of horseradish peroxidase injected intraocularly. Fetuses aged embryonic day 21 (E21) to E29 and an adult rabbit were examined. Gestation in the rabbit is 30–31 days. On E21 contralaterally projecting retinal fibers invade across the entire SC. Their distribution is initially diffuse within the superficial laminae, but by E29 they have a distinct stratified appearance. Ipsilaterally projecting retinal fibers invade the rostral half of the SC on E21. By E23 they cover the entire SC and overlap the contralateral fibers both tangentially and radially. The ipsilateral fibers for the most part are sparsely distributed, but they form a dense focal distribution in the rostrolateral quarter of the SC. This focus straddles the stratum griseum superficiale/stratum opticum (SGS/SO) border. On E25 the ipsilateral fibers maintain their widespread distribution and focal rostrolateral concentration. By E27 they are excluded almost entirely from the caudal half of the SC and are reduced in density in the rostromedial quarter of the nucleus. On E29 the ipsilateral terminal field forms distinct patches and bands that are restricted to the rostrolateral quarter of the SC and are confined to the SGS/SO border. Thus, a few days before birth the pattern and location of the ipsilateral retinocollicular projection resemble those seen in the adult. The early widespread distribution of the ipsilaterally projecting retinal fibers to the SC and their eventual restriction in the fetal rabbit are consistent with the development of this projection in other mammalian order

ISSN:0092-7317    

DOI:10.1002/cne.902860408

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractAn antiserum raised against rat glutamate decarboxylase was used to map GABAergic boutons in the inferior olive of rabbit, cat, rhesus monkey, and human. A description of the human periolivary region is also included. The inferior olive of each species contained a dense GABAergic innervation, but immunostaining intensities varied among regions. These intensities were evaluated visually and photomertrically, and the sizes and frequencies of occurence of boutons in various olivary subnuclei were measured. The beta nucleus in all species was intensely immunostained and contained the largest boutons. The caudal subdivision of the dorsal accessory olive stained with a lower intensity than the beta nucleus, but contained similarly large GABAergic boutons. By visual analysis, the rostral subdivision and the subnucleusaof the medial accessory olive and the principal olive were stained with an intermediate intensity, and these regions contained small GABAergic boutons. Photometric analysis of focal regions of the neuropil, however, revealed species differences in the staining intensity of the principal olive, which was lowest in rabbits and highest in primates. In all species, the lowest immunostaining intensity was observed in the subnucleusbof the medial accessory olive. Species variations in bouton sizes and regional staining intensities were observed in the dorsal cap and the dorsomedial cell column. The heterogeneous staining pattern and regional variation of bouton size argue for the existence of separate GABAergic projections to discrete regions of the inferior olive. Since glutamate decarboxylase immunostaining patterns in the olive are largely similar across species, the afferent projections producing these patterns may also be similar.

ISSN:0092-7317    

DOI:10.1002/cne.902860409

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902860410

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902860411

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY