摘要:

AbstractTissue removed from 3, 6, 9, 12, 15, and 21‐day‐old rats has been prepared for correlative light and electron microscopy to examine the maturation of cell bodies, dendrites, and axons of pyramidal neurons in layer V of rat visual cortex. As the size of the cell body increases steadily during the first 3 postnatal weeks there is an equivalent growth in nuclear volume. By day 15, there are infoldings in the nuclear envelope which may be induced by eye opening on day 14. Nucleoli increase in size until day 9, after which they appear to condense. Within the perikarya, the most conspicuous change is the amount and organization of the rough endoplasmic reticulum. Symmetric axosomatic synapses are evident by day 6. The ultrastructure of dendrites does not change substantially with age. Dendrites form synapses with symmetric densities as early as day 3 and asymmetric ones by day 9. It seems that dendritic spines begin as low, broad protrusions having symmetric junctions with smaller diameter axonal processes. With time they become taller stumps, before acquiring their mature lollipop shape and participating in asymmetric synapses with axonal varicosities. Other dendritic appendages, filopodia, and growth cones are transient structures, being conspicuous only between days 3 and 12. “Terminal” growth cones are essential for extension of dendritic processes, whereas “en passant” growth cones and filopodia seem important for dendritic branching. Boutons of mature pyramidal cell axons form asymmetric synapses with dendritic shafts and spines, but the developing synapses formed by these axons have more symmetric junctions. The maturation of pyramidal cell features progresses in concert with such extrinsic determinants as afferent input and is probably influenced by the competency of synaptic

ISSN:0092-7317    

DOI:10.1002/cne.902030402

出版商:Alan R. Liss, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractIn this paper we present evidence that early eye rotation inXenopusleads to anatomical rearrangements in a portion of the binocular visual system. In the past, electrophysiological mapping had shown that the topography of the ipsilateral visuotectal projection is changed by such eye rotation and that this change requires visual experience. However, knowledge of the anatomical basis for this electrophysiological change was lacking. The identification of the nucleus isthmi as a link in the projection has allowed us to study the topography of the ipsilateral system by use of horseradish peroxidase. We present data showing that early eye rotation alters the topography of the crossed isthmotectal projection. These results demonstrate that the orientation of a topographically organized projection can be changed by procedures which do not involve direct manipulation of the source, pathway, or target of the projection.

ISSN:0092-7317    

DOI:10.1002/cne.902030403

出版商:Alan R. Liss, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractThe accessory optic system ofRana pipienswas investigated by autoradiographic, horseradish peroxidase, and Golgi techniques, revealing a complexity of neuroanatomical organization previously unrecognized. Retinal afferents project to the nucleus of the basal optic root (nBOR) via a primary bundle and more diffuse, medial bundle of optic axons, both of which contain large‐ and small‐diameter fibers. At least six types of retinal ganglion cell contribute to the basal optic root (BOR), including giant ganglion cells, two intermediate‐sized ganglion cell types, small ganglion cells, and two types of displaced ganglion cell. The major retinal projection is contralateral, but a small, ipsilateral component also exists. Afferents from neurons which are postsynaptic to the thalamic retinal terminal fields also reach nBOR.Four distinct cell types were identified within the terminal field of nBOR: stellate neurons (63%), amacrine cells (19%), elongate neurons (14%), and large ganglionic neurons (4%). Both stellate and amacrine cells appear to be intrinsic neurons, while elongate and ganglionic neurons constitute the efferent neuron population of nBOR. In addition, cells which lie medial to the terminal field, pyriform and commissural neurons, send dendrites into nBOR. Pyriform neurons project to the nucleus of the medial longitudinal fasciculus (nMLF) and cranial nerve nuclei III and IV, while commissural neurons project to the contralateral nBOR. Large reticular neurons of the nMLF also send dendrites into nBOR.Efferent projections from nBOR were observed in the large‐celled pretectal nucleus and in nucleus lateralis profundus. A second major projection originates from the peri‐nBOR region and is associated with the oculomotor system and with the nMLF. Efferent projections from the nMLF to the vestibular nuclei and to the rostral spinal cord were also observed, as well as projections which reach the brainstem from the large‐celled pretectal nucleus, the posterior thalamic and anterior mesencephalic c

ISSN:0092-7317    

DOI:10.1002/cne.902030404

出版商:Alan R. Liss, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractThe distribution of monoaminergic cell bodies in the brainstem of the cat has been examined with Falck‐Hillarp fluorescence histochemical technique. Quantitative determinations indicate that the cat brainstem contains about 60,300 indolaminergic (IA) cells. The majority of these (about 46,700, or 77.5%) are located within raphe nuclei. The largest number is contained within nucleus raphe dorsalis (RD), accounting for around 24,300 IA cells, while raphe pallidus (RP) holds about 8,000, raphe centralis superior (RCS) 7,400, raphe magnus (RM) 2,400, raphe obscurus (RO) 2,300, linearis intermedius (LI) 2,100, and the raphe pontis (RPo) only some 280 IA cells. The IA cells represent, however, only part of the neuronal population of raphe nuclei, which, in addition, hold varying numbers of other medium‐sized and small‐sized neurons. Thus, quantifications in Nissl‐stained material indicate that the IA cells make up about 70% of the medium‐sized cells in RD, 50% in RP, 35% in RCS and RO, 25% in LI, 15% in RM, and only 10% in RPo. The substantial numbers of small‐sized perikarya observed in all raphe nuclei may represent interneurons.Significant numbers of IA cells were consistently located outside the raphe nuclei at all brainstem levels. In all, these amounted to approximately 13,600, or 22.5% of the total number of IA cells. Thus, IA cells occurred in the myelinated bundles, and sometimes in reticular formation, bordering the raphe nuclei; in the ventral brainstem forming a lateral extension from the ventral raphe (RP, RM, RPo, RCS, and LI) to the position of the rubrospinal bundle; in the periventricular gray and subjacent tegmentum of dorsal pons and caudal mesencephalon; in the locus coeruleus (LC) complex; around the motor trigeminal nucleus; caudal to the red nucleus; and in the interpeduncular and interfascicular nuclei. The wide distribution of IA cells leads to a considerable mixing with catecholaminergic (CA) cell groups.Our observations on CA cell distribution are essentially in accordance with previous reports. Quantifications indicate that the LC complex contains about 9,150 CA cells, unilaterally. A previously unnoticed group of scattered CA cells was found in relation to the vestibular nuclei and extending dorsally toward the deep cerebe

ISSN:0092-7317    

DOI:10.1002/cne.902030405

出版商:Alan R. Liss, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractThe torus semicircularis of Gymnotiform fish is an enlarged laminated midbrain structure which receives lemniscal input from electrosensory, mechanoreceptive lateral line, and auditory systems. The electrosensory input is confined to the dorsal torus, while the auditory and mechanoreceptive systems project to the ventral torus. Anterograde and retrograde techniques were used to determine the connections of the dorsal torus inApteronotusandEigenmannia.The dorsal torus can be divided into nine major laminae, each of which has distinct afferent and efferent connections. The dorsal torus receives five afferent inputs: (1) A contralateral topographic input from the posterior lateral line lobe (PLLL) projects to laminae III, V, VI, VII, VIIIB, and VIIID. (2) Eurydendroid cells of the caudal lobe of the cerebellum project contralaterally to lamina VIIIB. (3) A portion of the descending nucleus of V projects to laminae VIIIA, VIIIC, and IX. (4) Lamina I is a cap of fine myelinated fibers which may originate in the torus longitudinalis. They project to laminae II and III. (5) The ipsilateral optic tectum projects to the dorsal torus. The dorsal torus projects to six major targets: (1) Laminae VII, VIII, and IX project bilaterally to a lateral region of the diencephalon above n. preglomerulosus, herein named n. electrosensorius. An area below the dorsal thalamus receives a smaller ipsilateral projection. (2) Laminae II, V, VIvn, VII, VIII, and IX project topographically to the deeper laminae of the ipsilateral optic tectum. This projection is in spatial register with the visual map in the superficial layers of the tectum. (3) Lamina VIIID projects ipsilaterally to the lateral reticular formation. (4) All laminae other than I, VI, and VIIIB project topographically to the ipsilateral n. praeeminentialis, which provides a powerful descending projection to the PLLL. (5) Lamina IX projects to a dorsal pretectal area. (6) The ipsilateral inferior olive receives a projection from the dorsal torus.

ISSN:0092-7317    

DOI:10.1002/cne.902030406

出版商:Alan R. Liss, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractThe chick ventral lateral geniculate nucleus (GLv) receives topographically corresponding projections from the retina and optic tectum. Tectal lesions produced on the day of hatching removed the tectogeniculate input to the GLv region corresponding to the tectal lesion and also severed some retinotectal axons. Following a survival period of 3 to 10 weeks, a patch of augmented retinogeniculate projection was noted in the GLv segment that corresponds topographically to the damaged area of the tectum. Changing the site of the tectal lesion led to changes in the locus of heavy retinal projection to the GLv predictable from topographic maps. Nuclei which received retinal but not tectal projections did not appear to have regions of augmented retinal termination nor did nuclei which received tectal but not retinal innervation. It is unlikely that the increased retinogeniculate termination is due to rerouting of growing retinotectal axons since the chick retinofugal pathway is well established by the time of hatching. Furthermore, there was no evidence of a projection from the ipsilateral eye to the affected GLv. On the basis of these light microscopic studies, it would appear that retinogeniculate terminals have sprouted in the GLv and that competition for terminal space, conservation of terminal space, proximity, and perhaps other factors are necessary for the augmented projection to occur.

ISSN:0092-7317    

DOI:10.1002/cne.902030407

出版商:Alan R. Liss, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractThe nonpyramidal neurons in area 17 of cat visual cortex have been examined in Golgi preparations. From their dendritic patterns, neurons are classified as beingmultipolar, bitufted, orbipolar, and on the basis of the abundance of dendritic spines asspinous, sparsely spinous, orsmooth.When neurons are so classified seven different types of nonpyramidal neurons are encountered in layers II through V.Three of the types of multipolar neurons in layers II through V have spherical dendritic trees. Thesmall multipolar cellshave smooth dendrites and are the smallest neurons in the cortex. They have short dendrites and dense local axonal plexuses and occur throughout layers II to V Thesparsely spinous stellate cellshave longer dendrites, are confined to layer II/III, and have local axonal arborizations, whereas thespinous stellate cellsare limited to layer IV. A fourth type of multipolar neuron in layers II through V is thebasket cell.Such neurons have elongate dendritic trees and either smooth or sparsely spinous dendrites. Depending upon the orientation of the neurons in the sections, their axons appear to form arcades or long, horizontally extended branches, or a mixture of these two axonal patterns. The terminal portions of the axons of these basket cells pass around the cell bodies of adjacent neurons.The two types of bitufted neurons in layers II through V have vertically oriented dendritic trees. One type, thechandelier cell, has smooth dendrites and a characteristic axon forming vertical strings of terminals. The othersparsely spinous bitufted neuronshave axons producing vertically oriented plexuses. The remaining type of neuron encountered in layers II through V is abipolar cell.The bipolar cell has a single major dendritic trunk arising from each pole of the cell body, and each of these gives rise to a very narrow, long, and vertically oriented dendritic tree. The axon usually takes origin from one of the primary dendrites.In layer I are horizontally oriented, bitufted cells with smooth dendrites. The axons of thesehorizontal cells of layer Iarise from one of the primary dendritic trunks and appear to form a plexus confined to layer I. Horizontally oriented neurons are also present in deep layer VI, but thehorizontal cells of layer VIare bipolar. The other two neuronal types in layer VI are multipolar cells with sparsely spinous dendrites. The larger of these two types resembles the basket cells in layers II through V, the only important difference between them being that in addition to the long horizontal branches, the axons of thebasket cells of layer VIhave a long ascending branch which reaches at least as far as layer IV. The othersparsely spinous cells of layer VIare medium sized. Their axons take a descending and oblique course before elaborating a locally distributed plexus.The various types of neurons defined in this study are compared with neurons described by previous authors who have examined the populations of nonpyramidal cells in area 17 of cat visual cortex and in other visual and nonvisual cortical areas of cats, monkeys, and rodents. In some cases it has been possible to postulate the functional roles that particular types of neurons might play within cat visual cortex.

ISSN:0092-7317    

DOI:10.1002/cne.902030408

出版商:Alan R. Liss, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractThe topographical organization of the hippocampal mossy fiber system, which connects the dentate granule cells with the pyramidal cells of the regio inferior, has been examined in rats with retrograde tracing methods. Following the application of the fluorescent dye True Blue to different parts of the mossy fiber layer in the hippocampal regio inferior, retrogradely labeled granule cells were observed in the dentate fascia. The distribution of the labeled cells within the dentate granule cell layer indicates that all mossy fibers have an almost parallel, slightly descending course in regio inferior near the dentate hilus. In the ventricular part of regio inferior, particularly toward the transition to the regio superior, the mossy fibers are sorted out according to the position of their parent cell bodies within the granular layer. Near the transition to regio superior the fibers from lateral granule cells extend both septally and temporally over a longer distance than the fibers from more medial cells. Similarly, the fibers coming from the superficial cells extend both septally and temporally over a longer distance than those from the deep cells. The mossy fibers arising from a specific septotemporal level of the dentate fascia innervate a segment of the regio inferior that extends approximately 180 μm above to approximately 1,600 μm below the level of origin. Similar results were obtained following injections of Nuclear Yellow and horseradish peroxidase.Since previous studies have demonstrated that the granule cells are formed along gradients from lateral to medial and from superficial to deep, there appears to be a correlation between the formation, and hence the position, of the granule cells and the topography of their projection into the regio inferio

ISSN:0092-7317    

DOI:10.1002/cne.902030409

出版商:Alan R. Liss, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractHorseradish peroxidase (HRP, Sigma VI, 30–70 nl of a 10–15% solution in saline) or3H‐5HT (30 Ci/mmole, 2.5 × 10−3M containing 3.3 × 10−3M norepinephrine in saline, 50–100 nl) was injected unilaterally into the dorsal hippocampus in separate groups of rats.HRP‐labeled cells were seen in the hippocampus, medial septal nucleus, nucleus of the diagonal band, supramammilary nucleus, median raphe nucleus, interfascicular portion of the dorsal raphe nucleus, and the locus coeruleus. In contrast,3H‐5HT‐labeled cells were largely restricted to the raphe nuclei. In this nucleus an equal number of ipsilateral and bilateral cells were found. Occasionally, these labeled cells stretched across the midline (bridge pattern).In another series, the3H‐5HT and HRP were injected into the same hippocampus either as a mixture or sequentially. This resulted in double labeling of the median and dorsal raphe neurons. A final group of rats received injections of3H‐5HT and HRP into opposing hippocampi. Double‐labeled cells accounted for 10% of the neurons labeled. In addition, closely paired neurons composed of an HRP‐and3H‐5HT‐containing cell were found. In summary, the serotonergic fibers may play a key role in harmonizing the electrical activity of the hippocampi by use of bilateral projections, paired neurons with differential projections, and bridging neurons stretching across the midline

ISSN:0092-7317    

DOI:10.1002/cne.902030410

出版商:Alan R. Liss, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractThe currently accepted concept of a primary sensory cell is a cell that gives rise to a central process which passes through the dorsal root to the spinal cord and a peripheral process which passes to the periphery via a peripheral nerve. If this is correct, then there should be equal numbers of sensory axons in the dorsal root, dorsal root ganglion cells, and sensory axons in the proximal peripheral nerve. The present study obtains these counts in animals in which extraneous axons have been removed from the peripheral nerve and root. The counts indicate that there are approximately 2.3 sensory axons in the dorsal root and proximal peripheral nerve for each ganglion cell in the sacral segments of the rat. We interpret these data as indicating that there is significant branching of sensory axons in the dorsal root and proximal peripheral nerve and thus the generally accepted picture of a dorsal root ganglion cell is not correct for some, perhaps all, of these cells. We offer the speculation that this peripheral branching may be an indication of single sensory neurons having receptive fields in two separate locations, and thus this may be an anatomical explanation for certain types of referred pain.

ISSN:0092-7317    

DOI:10.1002/cne.902030411

出版商:Alan R. Liss, Inc.    

年代:1981

数据来源: WILEY