摘要:

AbstractIt has been reported that aspartate and glutamate selectively impair the structure (Olney, '82) and function (e.g., Furakawa and Hanawa, '55) of second‐ and third‐order retinal neurons while leaving the photoreceptor unaffected. Either amino acid may mimic the endogenous photoreceptor neurotransmitter (Ehinger, '82). We report here that excitatory amino acids also induce massive rod photoreceptor disc shedding in eyecups ofXenopus laevismaintaninedin vitro.Disc shedding is the process whereby photoreceptors eliminate effete discs. It involves interaction between the distal outer segment and pigment epithelium. Millimolar L‐asparate and L‐glutamate, as well as micromolar kainic acid, a glutamate analog, stimulate disc shedding three‐to fivefold higher than normal light‐evoked shedding levels and result in extensive inner retinal damage. Fifty‐millimolar KC1, 1.0 μM ouabain, and replacement of sodium with choline also stimulate disc shedding and alter retinal structure. Extensive neurotoxicity appears unrelated to disc shedding since other amino acids having no significant or marginal effects on retinal structure also stimulate shedding. While the site and mechanism of action of these effectors, and in particular the excitatory amino acids, is now undefined, the data show that amino acids thought to act directly and specifically on inner retinal neurons can also markedly alter photoreceptor and pigment epithel

ISSN:0092-7317    

DOI:10.1002/cne.902390402

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe anatomical localization of cholecystokinin‐like immunoreactivity (CCK‐I) within the rat main olfactory bulb was analyzed by using the‐peroxidase‐antiperoxidase immunocytochemical technique. Neurons or neuronal processes containing CCK‐I were localized within all laminae of the olfactory bulb except the olfactory nerve fiber layer. A large population of CCK‐I neurons, with morphology, size, and distribution corresponding to that of the middle and external tufted cells, was observed within a zone extending from the deep periglomerular region through the superficial one‐half to one‐third of the external plexiform layer. A smaller number of immunoreactive perikarya were found in the deep external plexiform layer, the glomerular layer, and rarely within the inner plexiform layer. These CCK‐I neurons appeared to correspond to internal tufted cells, periglomerular cells, and deep short‐axon cells, respectively. Dense CCK‐I staining of fibers and terminals was present within the internal plexiform layer and, less densely, within the neuropil of the granule cell layer. In addition, terminal‐like CCK‐I was localized within layer 1A of the anterior olfactory nucleus, the olfactory tubercle, and the most rostral piriform cortex. This observation provides corroboration for the identification of the principal CCK‐I neuron in the rat olfactory bulb as the centrally projecting middle tufted cell. The present results, demonstrating the localization of CCK‐I to both local circuit and projection neurons of the olfactory bulb and to terminal‐like puncta in the internal plexiform and granule cell layers, suggest that CCK may be significantly involved in olfacto

ISSN:0092-7317    

DOI:10.1002/cne.902390403

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe functional organization of the motoneurons in the spinal cord of the sea robin,Prionotus carolinus, was studied by means of retrograde transport of horseradish peroxidase (HRP). This species has a complex pectoral apparatus which includes not only a webbed fin, but also three independently mobile fin rays.The motoneurons in the rostral spinal cord fall into two longitudinal columns: dorsal and ventral. The motoneurons of the ventral column innervate the appendicular musculature of the pectoral apparatus.Within the ventral motor column of the rostral spinal cord, four distinct motoneuronal pools were found. The largest pool is situated at the rostral‐most end of the spinal cord and contains the motoneurons that innervate the musculature of the webbed pectoral fin. The motoneurons that innervate the fin rays are located in sequentially more posterior pools so that the antero‐ventral fin ray is controlled by motoneurons situated farthest caudally. The somatotopic arrangement exactly corresponds to the sensory somatotopy determined previously. Furthermore, each fin ray has its sensory representation in a unique accessory spinal lobe which is connected in a reflex fashion to the motoneuronal pool that provides motor output to the same fin

ISSN:0092-7317    

DOI:10.1002/cne.902390404

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

年代:1985

数据来源: WILEY

摘要:

AbstractPeripheral and central oculomotor organization was studied in the goldfish. The sizes of the extraocular muscles were quantified by counting the fibers contained in a given muscle and by area measurements of the cross‐sectional surfaces. All the muscles were of approximately similar size. Kinematics were determined by electrical stimulation of a given muscle. The macroscopic appearance and kinematics of the muscles had the characteristics of other lateral‐eyed animals (e.g., rabbit). Locations of extraocular motor neurons wert found by retrograde transport of horseradish peroxidase (HRP) following injections into individual extraocular muscles. The eye muscles were innervated by four ipsilateral (lateral rectus, medial rectus, inferior oblique, inferior rectus) and two contralateral (superior rectus, superior oblique) motor neuron pools. The oculomotor nucleus was found in the midbrain, at the level of the caudal zone of the inferior lobe of the hypothalamus. Inferior rectus motor neurons were located drosally in the oculomotor nucleus, whereas medial rectus, superior rectus, and inferior oblique motor neurons were intermingled in its more caudal portions. All labelled cells were located dorsally and medially to the medial longitudinal fasciculus (MLF) in close proximity to either the floor of the ventricle or the midline region. Occasionally, motor neurons were interspersed within the fiber bundles of the MLF or the exiting fibers of the oculomotor nerve. The trochlear nucleus, containing superior oblique motor neurons, was found in the immediate lateral and caudal neighborhood of the oculomotor nucleus, where its rostral border overlapped with the caudal border of the latter. The abducens nucleus, containing lateral rectus motor neurons, was located in the posterior brainstem in the neighborhood of the vestibular nuclear complex. This nucleus was divided into a rostral and a caudal portion. The axons of ipsilaterally projecting motor neurons headed toward their respective nerve roots via the shortest possible route, as did the axons of superior rectus motor neurons, which crossed the midline without detour to enter the contralateral oculomotor nerve. In contrast, trochlear motor neuron axons arched around the dorsal aspect of the ventricle through the cerebellar commissure to reach the contralateral trochlear nerve. The morphology of individual motor neurons was visualized by intrasomatic injection of HRP. Cell somata had oblong shapes, and their large dendrites were oriented laterally and ventrally. The axons did not collateralize within the midbrain region or the oculomotor nerve as far as they could be traced. The oculomotor system of the goldfish is similar to that found in other teleosts and higher vertebrates, displaying characteristics of an animal whose eye movements cover all regions of its external environm

ISSN:0092-7317    

DOI:10.1002/cne.902390405

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

年代:1985

数据来源: WILEY

摘要:

AbstractBy using anterograde transport autoradiography, the present experiments demonstrated that the pattern of tectogeniculate projections in young (birth–14 postnatal days) kittens is strikingly different from that present in adult cats. Rather than being confined to the ventral C laminae, the neonatal projection extended across all layers of the lateral geniculate nucleus. This projection, like that in the adult cat, originates from cells in superficial laminae and is visuotopically organized. Thus, labeling only a portion of the superior colliculus with tritiated leucine produced a topographically appropriate strip of labeling in the ipsilateral lateral geniculate nucleus that encompassed all laminae and was especially dense in all interlaminar zones. Transported label also invaded the medial interlaminar nucleus (MIN).The loss of tectogeniculate projections in the neonate from MIN and the dorsal laminae and interlaminar zones of the lateral geniculate nucleus does not appear to begin until 1–2 weeks postnatal. Once initiated, however, the process is nearly completed by 21 days postnatal. It is not yet known whether the loss of these “anomalous” projections is due to the pruning of axonal collaterals, cell death, or a combination of the two processes. However, by comparing these data with those from other laboratories, it does appear that the loss of tectogeniculate projections depends on the presence of the two eyes and may reflect the differential laminar distribution of W‐, X‐, and Y‐cell types. The protracted postnatal anatomical maturation of tectogeniculate projections differs substantially from the earlier maturing patterns apparent in all other tectof

ISSN:0092-7317    

DOI:10.1002/cne.902390406

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

年代:1985

数据来源: WILEY

摘要:

AbstractInjections of the retrograde tracer HRP into the border region of the temporal visual area MT and adjoining cortex inCallithrixlabeled pyramidal neurons in area 17 of the contralateral hemisphere. Evidence is presented that this newly discovered heterotopic callosal projection of the monkey striate cortex connects regions of representation of the zero vertical meridian of the visual field in a retinotopic order.

ISSN:0092-7317    

DOI:10.1002/cne.902390407

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe coexistence of cholecystokinin‐octapeptide‐like (CCK‐L) and/or vasoactive‐intestinal‐polypeptide‐like immunoreactive (VIP‐LI) materials and glutamate decarboxylase (GAD) was studied in the rat hippocampus and dentate gyrus by means of immunohistochemistry. Consecutive 40‐μm‐thick sections were incubated in different antisera and those cells which were bisected by the plane of sectioning so as to be included at the paired surfaces of two adjacent sections were identified. The coexistence of the immunoreactivities for these peptides and GAD in the same cell could thus be determined by observing the immunoreactivity of the two halves of the cell, incubated in two different antisera.Almost all of the CCK‐LI neurons were also GAD immunoreactive, whereas only about 10% of the GAD‐immunoreactive neurons were CCK‐LI. The percentages of GAD‐immunoreactive neurons which were also immunoreactive for CCK were dependent on the laminar area in which they were found: i.e., 15–20% in the stratum radiatum of the hippocampus, about 10% in the stratum pyramidale, and about 6% in the stratum oriens.In contrast to the CCK‐LI neurons, only about 40% of the VIP‐LI neurons were identified to be also GAD immunoreactive, which might correspond to only part of the GAD‐immunoreactive neurons. Furthermore the coexistence of VIP‐LI and CCK‐LI materials was recognized in about 10% of the CCK‐LI neurons or about 35% of the VIP‐LI neurons, indicating that some GABAergic neurons (presumably about 1%) in the rat hippocampus and dentate gyrus ma

ISSN:0092-7317    

DOI:10.1002/cne.902390408

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe histological organization of the filum terminale of the spinal cord inRana catesbeianaandRana pipienswas characterized to determine if this region possessed an organized neuropil or whether it was merely a glial remnant that persisted after absorption of the larval tail.The excised filum was maintained in vitro. Intracellular electrophysiological recording was performed with horseradish peroxidase injection. Tyrosine hydroxylase and serotonin distribution were revealed by immunocytochemical methods.Astroglia were the dominant cell type and displayed an elaborate variety of forms. The mean membrane potential was logarithmically related to the extracellular potassium concentration but displayed a sub‐Nernstian slope. Oligodendroglia were also seen, as well as ependyma that extended from the central canal to the pial surface.Neuronal activity was revealed by occasional intracellular penetration of elements that displayed spontaneous excitatory postsynaptic or action potentials. The major evidence for the presence of neurons was the demonstration of tyrosine hydroxylase (TH) immunoreactivity in a large population of cerebrospinal fluid‐contacting neurons that abutted the ventral half of the central canal. The axons of these cells entered a ventral bundle and ascended the cord; some fibers left this tract and apparently terminated on large arcuate neurons within the filum. Serotoninergic fibers were primarily confined to a subpial location at the dorsal midline.We conclude that the filum terminale of the frog has a sparse but functional neuropil that is organized around the central canal and supported by a profusion of elaborate glial fo

ISSN:0092-7317    

DOI:10.1002/cne.902390409

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe population of sensory hair cells in the macula neglecta auditory epithelium in skates increases from 500 to more than 3,000 postembryonically, but during the same time period the number of neurons innervating the epithelium changes by a much smaller amount, if at all. Morphometric analyses of the peripheral terminal arbors of these neurons demonstrate that the arbors expand in area through intussusceptive growth, so that each neuron contacts more hair cells as the epithelium grows by appositional addition of new hair cells at its outer edge. The synaptic contacts that these neurons make with hair cells may not be permanent. Many of the neurons that innervate the growing macula appear to shift their terminal arbors, breaking synaptic contacts with older hair cells in the center of the sensory epithelium as they branch to form new contacts with younger hair cells that are located in the periphery of the epithelium. Over 80% of the terminal branches of these auditory neurons are directed toward the outer edge of the macula, the site where new hair cells are produced. This suggests that the growth cones of these continually growing neurons are guided to newly produced hair cells by an active attraction mechanism.

ISSN:0092-7317    

DOI:10.1002/cne.902390410

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe projections from the deep cerebellar nuclei and the sensorimotor cortex to the red nucleus were studied in the rat using anterograde transport of horseradish peroxidase conjugated with wheat germ agglutinin (HRP‐WGA). The anterogradely transported HRP‐WGA was visualized ultrastructurally by using a modification of the tetramethylbenzidine (TMB) histochemical technique of Carson and Mesulam ('82). Following injection of HRP‐WGA into the sensorimotor cortex, ultrastructural examination of anterograde labeling in the ipsilateral red nucleus revealed labeled synaptic terminals located on small‐diameter dendrites of the parvocellular region. These terminals made asymmetrical contacts and contained round vesicles. HRP‐WGA placement in the nucleus lateralis resulted in anterograde labeling of synaptic terminals which made asymmetrical contacts with small‐ to medium‐sized dendrites of the parvocellular red nucleus. Similar placements in the nucleus interpositus gave rise to anterograde labeling of synaptic terminals which made asymmetrical contacts with somata and proximal dendrites of magnocellular neurons. In addition, retrograde labeling of magnocellular neurons was also observed following HRP‐WGA placements in the nucleus interpositus. Anterogradely labeled interpositorubral synaptic terminals were located on retrogradely labeled rubrocerebellar neurons. The rat red nucleus thus receives topographically organized afferents which are characterized by their specificity in location at the

ISSN:0092-7317    

DOI:10.1002/cne.902390411

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

年代:1985

数据来源: WILEY