ISSN:0092-7317    

DOI:10.1002/cne.903000102

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractWe quantified the spatial distribution of presumed ganglion cells and displaced amacrine cells in unstained whole mounts of six young normal human retinas whose photoreceptor distributions had previously been characterized. Cells with large somata compared to their nuclei were considered ganglion cells; cells with small somata relative to their nuclei were considered displaced amacrine cells. Within the central area, ganglion cell densities reach 32,000‐‐38,000 cells/mm2in a horizontally oriented elliptical ring 0.4‐‐2.0 mm from the foveal center. In peripheral retina, densities in nasal retina exceed those at corresponding eccentricities in temporal retina by more than 300%; superior exceeds inferior by 60%. Displaced amacrine cells represented 3% of the total cells in central retina and nearly 80% in the far periphery. A twofold range in the total number of ganglion cells (0.7 to 1.5 million) was largely explained by a similar range in ganglion cell density in different eyes. Cone and ganglion cell number were not correlated, and the overall cone: ganglion cell ratio ranged from 2.9 to 7.5 in different eyes. Peripheral cones and ganglion cells have different topographies, thus suggesting meridianal differences in convergence onto individual ganglion cells.Low convergence of foveal cones onto individual ganglion cells is an important mechanism for preserving high resolution at later stages of neural processing. Our improved estimates for the density of central ganglion cells allowed us to ask whether there are enough ganglion cells for each cone at the foveal center to have a direct line to the brain. Our calculations indicate that (1) there are so many ganglion cells relative to cones that a ratio of only one ganglion cell per foveal cone would require fibers of Henle radiating toward rather than away from the foveal center; and (2) like the macaque, the human retina may have enough ganglion cells to transmit the information afforded by closely spaced foveal cones to both ON‐ and OFF‐channels. Comparison of ganglion cell topography with the visual field representation in V1 reveals similarities consistent with the idea that cortical magnification is proportional to ganglion cell density throughout the v

ISSN:0092-7317    

DOI:10.1002/cne.903000103

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractRecent studies of neuronal cholecystokinin (CCK) expression performed with more sensitive techniques have demonstrated that the distribution of the expression of this peptide is more widespread than previously thought. In the present study, hybridization histochemistry was used to map cortical neurons expressing the CCK gene in adult and developing rats. Retrograde tracing with Fluorogold in combination with hybridization histochemistry was used to demonstrate some of the projections of these neurons.Neurons expressing the CCK gene were found in all areas of the neo‐ and allocortices. They were of several morphological types, including pyramidal neurons, and were found in almost all layers, albeit at different relative numbers and with different levels of expression. Generally, layers II and III, deep layer V, and layer VI had many neurons expressing CCK mRNA.Cortical CCK expression was first detected on the 15th day of gestation in the primordial plexiform layer. Expression developed thereafter in a regular and continuous fashion until an adult‐like pattern was present on the 21st day after birth.Cortical neurons containing CCK mRNA were found in almost all the projections studied. Many neurons in both neo‐ and allocortical areas with cortico‐cortical, associational, and commissural pathways contained CCK mRNA. Similarly, numerous corticostriatal neurons contained CCK mRNA; however, only a few corticothalamic neurons expressed CCK mRNA. These results demonstrate that in the rat cortex the distribution of projection neurons expressing CCK is much more widespread than had been previously shown and will stimulate further investigations into the role of CCK in these

ISSN:0092-7317    

DOI:10.1002/cne.903000104

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractIntracellular, in vivo recordings were used to identify and subsequently to label neurons in the cat motor cortex in which long‐term potentiation (LTP) was induced. Thirty‐nine motor cortical neurons that produced excitatory postsynaptic potentials (EPSPs) in response to microstimulation in areas 1‐‐2 (SI) or in area 5a (SIII) were studied. Amplitudes of EPSPs produced in response to test stimulation (1 Hz) were recorded before and after tetanic stimulation (200 Hz, 20 seconds). In 25/39 cells (64%), EPSP amplitudes were significantly increased following the tetanic stimulation (65 ± 51% average increase), and remained at the potentiated level as long as stable recordings could be maintained (20 ± 18 minutes, maximum = 90 minutes). LTP was induced exclusively in cells that produced monosynpatic EPSPs in response to area 1‐‐2 or area 5a stimulation. Of the 39 analyzed cells, 13 were labeled by intracellular injections of 5% biocytin. Neurons in which LTP was induced included both pyramidal and nonpyramidal cells and were located exclusively in layers II or III of the motor cortex; cells in deeper cortical layers were not potentiated. These findings indicate that various corticocortical inputs can increase the efficacy of synaptic transmission in a subset of motor cortical neurons. We propose that this plasticity in synaptic transmission constitutes one of the bases of motor learni

ISSN:0092-7317    

DOI:10.1002/cne.903000105

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe influence of aging and age‐related cochlear impairment on the ventral cochlear nucleus was evaluated by measuring morphological properties of the octopus cell area (OCA) in five age groups of inbred C57BL/6J and CBA/J mice (young adult to very old). The former strain demonstrates progressive cochlear sensorineural pathology and hearing loss during middle age; the latter has only modest sensorineural pathology late in life. Histological sections of the OCA were evaluated with serial sections and several stains for neurons, glia, and fibers, and Golgi impregnations were also used. Aging was associated with a decrease in volume of the OCA, a loss of neurons, slight decrease in neuron size, increased packing density of glial cells, and changes in dendrites ranging from minor to total loss of primary branches. The greatest changes occurred in extreme old age, beyond the median lifespan. Age‐related changes were not exacerbated by sensorineural pathology in aging C57BL/6J mice. Individual octopus cells varied greatly in the extent of age‐related abnorm

ISSN:0092-7317    

DOI:10.1002/cne.903000106

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe distribution of cholecystokinin (CCK)‐immunoreactive nerve fibers and cell bodies was studied in the forebrain of control and colchicine‐treated guinea pigs by using an antiserum directed against the carboxyterminus of CCK octapeptide (CCK‐8) in the indirect immunoperoxidase technique. Virtually all forebrain areas examined contained immunoreactive nerve fibers. A dense innervation was visualized in: neocortical layers II‐III, piriform cortex, the medial amygdala, the medial preoptic area, a circumventricular organ‐like structure located at the top of the third ventricle in the preoptic area, the subfornical organ, the posterior bed nucleus of the stria terminalis, the posterior globus pallidus (containing labeled woolly fiber‐like profiles), the ventromedial hypothalamus, the median eminence, and the premammillary nucleus. A moderately dense innervation was visualized elsewhere excepted in the septum and thalamus where labeled axons were comparatively few. Immunoreactive perikarya were abundant in: neocortex (especially layers II‐III), piriform cortex, amygdala, the median preoptic nucleus, the bed nucleus of the stria terminalis, the hypothalamic paraventricular (parvicellular part), arcuate, and dorsomedial (pars compacta) nuclei, the dorsal and perifornical hypothalamic areas, and throughout the thalamus. Areas also containing a moderate number of labeled cell bodies were the medial preoptic area, the globus pallidus, the caudate‐putamen, and the periventromedial area in the hypothalamus. Immunostained perikarya were absent or only occasionally observed in the septum, the suprachiasmatic nucleus, the magnocellular hypothalamoneurohypophyseal nuclei, and the ventral mesencephalon. In the adenohypophysis corticomelanotrophs were labeled in both males and females, and thyrotrophs were labeled in females only.This distribution pattern of CCK‐8 immunoreactivity is compared to those previously recorded in other mammals. This shows that very few features are peculiar to the guinea pig. It is discussed whether some interspecific differences in immunostaining are real rather th

ISSN:0092-7317    

DOI:10.1002/cne.903000107

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe morphology of afferent fibers ascending to the cuneate nucleus has been examined in this and the subsequent paper in order to quantify the pattern of arborization and bouton arrangement of selected classes of primary afferents and to compare these data with data from postsynaptic fibers ascending to the cuneate nucleus.Electrophysiologically identified G hair and la muscle afferent fibers in the cuneate fasciculus were intraaxonally injected with horseradish peroxidase. Cutaneous afferents terminated dorsal to proprioceptive afferents, especially at middle levels of the cuneate nucleus. The spacing of collaterals along G hair fibers was variable, but averaged 1.46 collaterals per mm; collateral density was higher at middle cuneate levels than in the rest of the nucleus. Collateral density of Ia fibers was lower than for G hair fibers and was lowest at caudal levels of the nucleus. Branches of G hair collaterals, though often initially diverging, usually converged to terminate in a single focus in the dorsal part of the nucleus. The probability of bifurcation of Ia collaterals decreased steadily at successive branch points. These collaterals branched less symmetrically than G hair collaterals, and terminated in the ventral cuneate with less dense arbors, stretched mediolaterally, but of comparable cross‐sectional area.Individual G hair collaterals gave rise to more boutons than Ia collaterals; in both cases they were mostly of the en passant type. Boutons were restricted to distal branches of G hair collaterals, whereas boutons of Ia collaterals were also located on proximal branches. Bouton size was similar for the two classes of collaterals.The data reported here, in combination with the published literature, suggest that the collaterals of roughly 300 G hair fibers overlap at any given point at middle levels of the cuneate nucleus. This high degree of anatomical convergence is not predicted by the functional segregation described with electrophysiological mapping, implying the presence of intrinsic nuclear mechanisms enhancing response specificit

ISSN:0092-7317    

DOI:10.1002/cne.903000108

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe morphology of single postsynaptic afferent fibers terminating in the feline cuneate nucleus was investigated by using transport ofPhaseolus vulgarisleucoagglutinin from the cervical spinal cord and intraaxonal injections of horseradish peroxidase into identified postsynaptic fibers in the cuneate fasciculus.Injections ofPhaseolusin C5 and C6 of both rhizotomized and non‐rhizotomized cats gave similar results and confirmed previous observations with other techniques. In one animal with the smallest injection and the fewest labeled fibers in the cuneate nucleus, ten individual collaterals were reconstructed from serial sections. Most of these collaterals were at middle levels of the cuneate (from obex to about 4 mm caudal to it); they were largely confined to the rim and ventral regions of the nucleus, and their terminal fields were restricted rostrocaudally. Electrophysiologically identified fibers stained with horseradish peroxidase had large receptive fields on the ipsilateral forepaw, and latencies suggesting an oligosynaptic link to the periphery. Most of the collaterals from these fibers were also at middle cuneate levels and terminated mainly at the periphery of the nucleus but gave rise to larger terminal arbors, including sparse terminal branches to the core of the nucleus.Individual postsynaptic fibers differed in several respects from primary afferent fibers. While the spacing of collaterals of postsynaptic fibers was intermediate between that of G hair and Ia fibers, their arbors were larger than either, and could extend through the dorsoventral extent of the cuneate nucleus. The pattern of bifurcation of postsynaptic fibers resulted in stringier arbors which encompassed larger and less dense terminal fields than those of primary afferents. The number of boutons per collateral was intermediate between G hair and Ia fibers, but boutons of postsynaptic fibers were substantially smaller. These morphological differences are consistent with distinct functional roles for the two main ascending afferent systems, as suggested by electrophysiological dat

ISSN:0092-7317    

DOI:10.1002/cne.903000109

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.903000101

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY