摘要:

AbstractThe central terminations, in the trigeminal nucleus, of afferents from the rat's postero‐orbital (PO) sinus hair have been investigated with transganglionic transport of horseradish peroxidase (HRP) and succinic dehydrogenase (SDH) histochemistry. The normal pattern of terminations has been compared with that found after section of an adjacent nerve, the infraorbital (IO) nerve, at three ages: neonatal, 1 week old, and adult.The PO afferent fibres have three separate representations in the brainstem‐in trigeminal sensory nucleus principalis (Vp) and rostral subnucleus oralis (Vo), in trigeminal subnucleus interpolaris (Vi), and in caudal trigeminal subnucleus caudalis (Vc) and C1dorsal horn. In coronal sections the areas of terminations were seen as oval patches lying ventrolaterally in Vp, Vo, and Vi and ventromedially in Vc and C1. Following neonatal IO nerve section the terminal areas were approximately doubled in Vp, Vo, and Vi but were unchanged in Vc and C1. IO nerve section at day 7 also caused a significant, though smaller (1.4× compared with 2.0×), increase in the terminal areas in the rostral three nuclei, without changing Vc and C1. However, no significant change in area occurred after adult IO nerve section. SDH histochemistry at 3 to 4 weeks of age showed patches of terminals on both normal and lesioned sides consistent with those seen after HRP.Previous studies have reported increased functional representation of surrounding intact skin regions, including the PO sinus hairs, after neonatal but not adult, IO nerve section. The present results show that there are concomitant anatomical changes. Like the functional results, the extent of the anatomical changes are dependent on the maturity of the rat when les

ISSN:0092-7317    

DOI:10.1002/cne.903120302

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

年代:1991

数据来源: WILEY

摘要:

AbstractCytogenesis in the postnatal cat retina was studied with the aid of3H‐thymidine autoradiography to identify the cell classes generated. Cell proliferate in two stages, Which are separate spatially and temporally. Previous studies have shown that during Stage 1, cytogenesis occurs at high density at the ventricular surface of the retina, whereas Stage 2 occurs at low density in the inner retinal layers. At the ages studied, the progeny of Stage 1 cytogenesis are distributed in an annulus toward the margin of the retina, and those of Stage 2 occur central to the annulus, indicating that Stage 2 follows Stage 1. Cell genesis in Stage 1 appears to cease by P16; genesis in Stage 2 persists until between P21 and P30. The same cell classes (amacrine cells, bipolar cells, Müller cells, and rod photoreceptors) are generated during both Stages 1 and 2, but there are significant changes in their proportions both within and between stages. The proportion of the Stage 1 mitoses that form bipolar cells increases from 31% at P0 to 62% at P14. A corresponding decrease is observed in the proportion of rods (from 60% at P0 to 32% at P14). The proportion of cells generated during Stage 2 that become rods increases from 39% at P0 to 70% at P21, whereas the proportion of bipolar cells decreases from 50% at P0 to 23% at P21. Müller cells form a relatively constant proportion (8 to 15%) of the cells generated during both Stage 1 and 2. Thus at the end of Stage 1, mostly bipolar cells are generated; at the end of Stage 2, mostly rods are genera

ISSN:0092-7317    

DOI:10.1002/cne.903120303

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe topographic organization of the somatosensory representation in the deep layers of the cat superior colliculus was reexamined using methods previously used to examine the visuotopy in these layers. This technique identified the distribution of neurons in the superior colliculus that represent a designated region of the body surface (i.e., a dermal image), as well as assessed the differential distribution of deep layer neurons representing different body regions (e.g., face, forelimb, hindlimb, etc.). When the area of densest representation within a dermal image was considered, a well‐ordered somatotopy was evident that was similar to the one previously described (Stein et al., '76:J. Neurophysiol. 39:401–419). Each region of the body surface, however, was represented within a surprisingly broad area of the deep layers, which often had considerable overlap with the representations of adjacent body regions. This organization was similar to that of the deep layer visuotopy and emphasizes that the representation of a peripheral stimulus is accomplished by the simultaneous activation of a large population of deep layer neurons. Furthermore, an examination of the convergence patterns on somatosensory‐responsive neurons demonstrated that the somatotopy was formed primarily by multisensory neurons. These data indicate that the somatosensory representation is best considered as a component of a comprehensive multisensory functional unit that plays a critical role in effecting behavioral responses to a wide variety of st

ISSN:0092-7317    

DOI:10.1002/cne.903120304

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe possible coexistence of calbindin D28k with parvalbumin and of calbindin D28k with cholecystokinin was studied in nonpyramidal cells of the rat dorsal hippocampal formation. Neighbouring Vibratome sections were immunostained either for calbindin D28k and parvalbumin or for calbindin D28k and cholecystokinin. The cells, halved during sectioning, were identified in both sections immunostained for different antigens. The coexistence of calbindin D28k and parvalbumin in the same neuron was rare throughout the hippocampal formation with the exception of stratum oriens of the CA1 region, where 9.6% of the parvalbumin‐immunoreactive cells also contained calbindin D28k. In stratum radiatum of the CA3 region, calbindin D28k and cholecystokinin coexisted in 12.5% and 21.2% of the calbindin D28k and cholecystokinin‐immunoreactive cells, respectively. In other regions of the hippocampal formation, the two markers coexisted in less than 5% of the cells of either type. The present results demonstrate that calbindin D28k‐, parvalbumin‐ and cholecystokinin‐containing nonpyramidal cells represent largely nonoverlapping cell populations and may thus be involved in different inhibitory

ISSN:0092-7317    

DOI:10.1002/cne.903120305

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

年代:1991

数据来源: WILEY

摘要:

AbstractCells in the superficial layers of the superior colliculus innervate multiple visual regions within the pulvinar‐lateral posterior complex of the cat. To characterize these neurons we have examined their immunocytochemical properties in conjunction with their projection patterns. In the present study, we show that a monoclonal antibody for substance P recognizes a morphologically diverse population of neurons, which can be classified as granular, stellate, angular, and horizontal or nonhorizontal fusiform cell types. These neurons are distributed throughout the superficial layers of the colliculus, with a peak density corresponding to sublayer 2 of the stratum griseum superficial. Injections of rhodamine latex microspheres into the pulvinar‐lateral posterior complex demonstrate that a substantial proportion of these collicular cells (at least 35%) project to this region of the posterior thalamus. The overall population of substance P‐containing cells, as well as the immunoreactive projection neurons, is composed of the same proportions of cell classes, with the exception that granular cells were not found to be projection neurons.A distinct wedge of substance P immunoreactivity, consisting of fiber and diffuse extracellular labeling, was discovered in the pulvinar‐lateral posterior complex. This staining was demonstrated to be confined entirely within the medial division of the lateral posterior nucleus, which is considered to be the principal tectorecipient zone of the extrageniculate visual thalamus. Lesions of the superior colliculus largely abolished the substance P immunoreactivity in the ipsilateral tectorecipient zone. These results are consistent with the view that substance P plays a role in the functional organization of the principal tectothalamic pathway of the cat's extrageniculate visual

ISSN:0092-7317    

DOI:10.1002/cne.903120306

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe avian nucleus of the solitary tract has an extensive subnuclear organization. Several subnuclear cell groups can be distinguished on the basis of cytoarchitectonic criteria. In general, the subnuclei of the medial division of the nucleus of the solitary tract receive gastrointestinal afferents, whereas the subnuclei of the lateral division of the nucleus of the solitary tract receive cardiopulmonary afferents. Forebrain afferents to the nucleus of the solitary tract are segregated to medial and lateral subnuclei, which are located at the periphery of the nucleus. These peripheral subnuclei of the nucleus of the solitary tract are also the source of ascending axonal projections to the forebrain. In this study, the tyrosine hydroxylase (initial enzyme for catecholamine synthesis) content of the anteromedial hypothalamic projecting neurons of the nucleus of the solitary tract is determined by use of a combined retrograde fluorescent dye‐immunofluorescence method.Fast Blue implanted into the anteromedial hypothalamus (in the region of the nucleus periventricularis magnocellularis) resulted in the retrograde labeling of neurons in the caudal two‐thirds of the nucleus of the solitary tract. At levels rostral to the obex, dye‐labeled cells were mostly observed in the dorsally located subnuclei medialis superficialis pars posterior and lateralis dorsalis pars posterior and in the ventrally located subnucleus medialis ventralis pars posterior. More centrally located subnuclei contained few labeled cells, if any. For example, subnucleus medialis intermedius pars posterior only had a few retrogradely labeled cells, whereas the centrally located subnucleus medialis dorsalis pars posterior was almost devoid of labeled cells. At levels caudal to the obex, many retrogradely labeled neurons of the nucleus of the solitary tract were observed.Neurons immunoreactively labeled for tyrosine hydroxylase were mostly found within subnuclei, which contain anteromedial hypothalamic projection neurons. In subnuclei medialis superficialis pars posterior and lateralis dorsalis pars posterior, 87% of the retrogradely dye‐labeled cells were also immunoreactively labeled, whereas in the caudal nucleus of the solitary tract (at levels caudal to the obex), 68% of the retrogradely labeled cells were immunoreactively labeled. Not all tyrosine hydroxylase containing cells had projections to the implantation site in the anteromedial hypothalamus since only 40% of the immunoreactive cells in the caudal nucleus of the solitary tract and 59% of the immunoreactive cells in the subnucleus medialis superficialis pars posterior were retrogradely labeled with Fast Blue. No double‐labeled neurons were found in the taenia choroidea (comparable in part to the mammalian area postrema) and the nucleus lateralis superficialis of the taenia choroidea, although many TH immunoreactive cells were observed. This study further underscores the complex subnuclear organization of the avian nucleus of the solitary tract as exemplified by the segregation of hypothalamic projecting neurons, which are mostly chemically coded for catec

ISSN:0092-7317    

DOI:10.1002/cne.903120307

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

年代:1991

数据来源: WILEY

摘要:

AbstractThrough its complex network of interconnections, each of the functionally specialized subdivisions in the cat primary somatosensory cortex may provide the motor cortex with different input and thus play a unique role in motor behavior. Areas 2 and 3a receive separate peripheral information. Cells in both regions project directly to the cat motor cortex but are thought to target different populations of neurons. In this study the morphology and distribution patterns of the area 3a projection to the motor cortex were compared to previous findings on the projection from area 2. Also, details of the projection from area 3a to area 2 were studied. Injections ofPhaseolus vulgarisleucoagglutinin were made into area 3a and fixed brain tissue was processed for immunohistochemical staining of this anterograde tracer. Tissue was examined with the light microscope to determine the patterns of the 3a projections to area 2 and motor cortex, area 4. Axons arising from cells in area 3a terminated in multiple column‐like clusters in both motor cortex and area 2. The small number of cells labeled at the injection sites suggested that multiple foci of the 3a fibers are formed by collateral axonal branches of the same neurons. The topography of the projection from area 3a to the motor cortex was more clearly denned than that from area 3a to area 2. Electron microscope analysis determined the laminar distribution and types of synapses formed between area 3a efferents and their target neurons. A high proportion of synapses was found in layer III in both target regions. However, unlike in area 4, labeled terminals were sparse in laminae I and II of area 2. Axospinous synapses were slightly more numerous than axodendritic synapses, but both were distributed similarly throughout the thickness of the cortex. In area 2 the axospinous synapses accounted for 63% of synapses and in area 4 for 57% of synapses. No axosomatic synapses were detecte

ISSN:0092-7317    

DOI:10.1002/cne.903120308

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

年代:1991

数据来源: WILEY

摘要:

AbstractThis study was done to elucidate the ancestral (plesiomorphic) condition for visual pathways to the hypothalamus in teleost fishes. Three patterns of pretectal organization can be discerned morphologically and histochemically in teleosts. Their taxonomic distribution suggests that the intermediately complex pattern (seen in most teleost groups) is ancestral to both the elaborate pattern (seen in percomorphs) and the simple pattern (seen in cyprinids). The pretectal nuclei involved can be demonstrated with acetylcholinesterase histochemistry selectively and reliably in different species of teleosts, suggesting that the same‐named nuclei are homologous in representatives of the three different patterns.Whereas there are visual pathways to the hypothalamus in both the elaborate (percomorph) and the simple (cyprinid) patterns, different pretectal and hypothalamic nuclei are involved. Thus visual hypothalamic pathways in these two patterns would not appear to be homologous.In this study, circuitry within the third, i.e., the intermediately complex, pattern is investigated. It is demonstrated that visual pathways project via the pretectum to the hypothalamus inOsteoglossum bicirrhosumand that they are very similar to the visual pathways in the elaborate pattern. This suggests that the circuitry in the intermediately complex pattern, as represented byOsteoglossum, is plesiomorphic (evolutionarily primitive) and the circuitry in both the simple pattern (seen in cyprinids) and the elaborate pattern (seen in percomorphs) is apomorphic (evolutionarily derived) for teleost

ISSN:0092-7317    

DOI:10.1002/cne.903120309

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

年代:1991

数据来源: WILEY

摘要:

AbstractThis study examined the effect of neonatal administration of capsaicin on nociceptive threshold and the distribution of calcitonin gene‐related peptide (CGRP), substance P (SP), and fluoride‐resistant acid phosphatase (FRAP) in the dorsal horn of the spinal cord during the course of development (10 days to 12 weeks of age) in the rat. As early as 10 days of age, CGRP‐like immunoreactivity was reduced in laminae I, II, and V, as well as in the bundles of fibers situated dorsal and ventral to the central canal. However, beginning on or about 6 weeks of age, the density of CGRP‐like immunoreactivity in the superficial laminae and in the bundles dorsal and ventral to the central canal increased. Moreover, thick, nonvaricose CGRP‐like immunoreactive fibers appeared in laminae III and IV. These recurring fibers were of primary afferent origin as demonstrated by their disappearance after multiple, unilateral rhizotomies. A similar age‐dependent alteration in the density of FRAP activity was also observed. Although virtually absent at 10 days of age after neonatal administration of capsaicin, the density of FRAP activity increased in lamina II by 8 weeks of age. This activity disappeared after multiple, unilateral rhizotomies, indicating that the FRAP activity that reappeared was of primary afferent origin. Neonatal administration of capsaicin also reduced the density of SP‐like immunoreactivity in the dorsal horn as early as 10 days of age, although the density of SP‐like immunoreactivity showed some recovery after 6 weeks of age. However, unlike CGRP‐like immunoreactivity or FRAP activity, the density of SP‐like immunoreactivity in capsaicin‐treated rats was not detectably altered by multiple, unilateral rhizotomies, indicating that it originated principally from intrinsic dorsal horn neurons. Age‐dependent alterations in both thermal and mechanical, but not chemical, nociceptive thresholds were also observed in these same animals. Thus, tail flick latency, hot plate latency, and paw withdrawal threshold were maximally increased at 6 weeks of age, after which time thresholds declined to vehicle‐treated values. In contrast, capsaicin‐treated animals were uniformly insensitive to ophthalmic administration of capsaicin. The correspondence between developmental alterations in CGRP‐like immunoreactivity or FRAP activity and in thermal and mechanical nociceptive thresholds is suggestive of a role of CGRP‐ or FRAP‐containing primary afferents in t

ISSN:0092-7317    

DOI:10.1002/cne.903120310

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

年代:1991

数据来源: WILEY

摘要:

AbstractThis study examined the ultrastructure of the region of transition where fascicles of olfactory axons leave the peripheral nervous system (PNS) to enter the central nervous system (CNS), the so‐called PNS‐CNS transitional zone. Adult rats were transcardially perfused with a solution of 1% glutaraldehyde and 1% paraformaldehyde, decapitated, and the heads decalcified over a period of several weeks in a solution of 1% glutaraldehyde in 0.1 M tetrasodium ethylenediamine tetraacetic acid; the latter solution was changed daily. It was found that astrocytes did not form the glia limitans at the nerve entry zone, unlike the situation that exists in other cranial and spinal nerves. Rather, the glia limitans in this region of the olfactory bulb was formed by a special type of glial cell, referred to as an ensheathing cell. Ensheathing cells are found only in the nerve fiber layer of the olfactory bulb. They possess a mixture of Schwann cell and astrocytic features and are more likely to be of placodal than of CNS origin. The meningeal coverings of the olfactory nerve rootlets and of the olfactory bulb are also described and the functional implications of the findings discus

ISSN:0092-7317    

DOI:10.1002/cne.903120311

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

年代:1991

数据来源: WILEY