摘要:

AbstractThe retinal projection to the pretectum in the pigeon has previously been described in detail only by means of anterograde degeneration techniques (Repérant, '73). The present study reinvestigated these retinal projections by using the more sensitive anterograde autoradiographic technique. In general, our results confirm and extend those of Repérant ('73). We have found that three pretectal nuclei–the nucleus lentiformis mesencephali, tectal gray, and the area pretectalis– receive heavy retinal input. A fourth pretectal nucleus, pretectalis diffusus, receives a slight retinal input. The nucleus lentiformis mesencephali can be divided into two closely apposed subnuclei that are cytoarchitecturally similar. We have termed them “lentiformis mesencephali, pars medialis” and “lentiformis mesencephali, pars lateralis.” The tectal gray can be divided into a rostral, retinorecipient region and a narrow, caudal, nonretinorecipient region. The cytoarchitecture and retinal terminal field in area pretectalis have been described previously by us (Gamlin et al., '84). Pretectalis diffusus is located caudal to the retinorecipient dorsal thalamus and rostral to area pretectalis.Localized retinal injections of3H proline delineated the number and extent of the retinal representations in the pretectum. Separate retinal representations were present in lentiformis mesencephali, pars medialis, lentiformis mesencephali, pars lateralis, the tectal gray, area pretectalis, and pretectalis diffusus. Only in the lentiformis mesencephali, pars medialis, lentiformis mesencephali, pars lateralis, and the tectal gray could the retinal representations be analyzed. Whereas the retinal representations in the lentiformis mesencephali, pars medialis and the tectal gray are comparable, the retinal representation in the lentiformis mesencephali, pars lateralis is different, being a mirror‐image mediolaterally.In this study we introduce a conservative nomenclature for the retinorecipient pretectal nuclei that is consistent with earlier studies, in particular, those of Kuhlenbeck ('39), but has been modified in the light of our findings. We believe that this nomenclature, combined with the detailed cytoarchitectural descriptions provided, should facilitate future studies of the

ISSN:0092-7317    

DOI:10.1002/cne.902690102

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractWe have used anterograde autoradiographic and retrograde HRP techniques to investigate the efferent connections of the retinorecipient pretectal nuclei in the pigeon. In the accompanying paper we identified these nuclei in the pigeon as the nucleus lentiformis mesencephali–pars lateralis and pars medialis, the tectal gray, the area pretectalis, and pretectalis diffusus. Although there are reports of a few of the projections of these nuclei, they had not previously been the subject of a detailed study.We found that different cell types in the lentiformis mesencephali, pars medialis and the lentiformis mesencephali, pars lateralis have descending projections to different targets. These targets include the inferior olive, the cerebellum, the lateral pontine nucleus, the nucleus papillioformis, the nucleus of the basal optic root, the nucleus mesencephalicus profundus, pars ventralis, the nucleus principalis precommissuralis, and the stratum cellulare externum. We found that a few cells in the lentiformis mesencephali project to the medial pontine nucleus, but that a much heavier projection arises from the nucleus laminaris precommissuralis, which is medial to the nucleus lentiformis mesencephali, pars medialis.The tectal gray has predominantly ascending projections to the diencephalon. The nuclei that it projects to are the nucleus intercalatus thalami, the nucleus of the ventral supraoptic decussation, the nucleus posteroventralis, the ventral lateral geniculate nucleus, the nucleus dorsolateralis medialis, and the nucleus dorsolateralis anterior. The tectal gray also projects topographically to layers 4 and 8–13 of the optic tectum.Area pretectalis has both ascending and descending projections. It has ipsilateral ascending projections to the nucleus dorsolateralis anterior, pars magnocellularis, the nucleus lateralis anterior, and the nucleus ventrolateralis thalami. It has ipsilateral descending projections to the central gray, the nucleus of the basal optic root, pars dorsalis, the lateral pontine nucleus, and the deep layers of the optic tectum. It has contralateral projections to the area pretectalis, the nucleus Campi Foreli, the interstitial nucleus of Cajal, the nucleus of Darkschewitsch, the cerebellum, and the Edinger‐Westphal nucleus.The efferent projections of pretectalis diffusus are limited. It projects contralaterally to the pretectalis diffusus, and ipsilaterally to the nucleus of the ventral supraoptic decussation, the lateral pons, and the cerebellum.Our results demonstrate that, by way of their ascending and descending projections, the retinorecipient pretectal nuclei can exert important influences on the range of visuomotor functions in which they participate. We know that area pretectalis mediates the pupillary light reflex (Gamlin et al., '84) and that the lentiformis mesencephali is involved in optokinetic nystagmus (McKenna and Wallman, '85). However, to our knowledge, other potential roles of the retinorecipient pretectal nuclei have not been ident

ISSN:0092-7317    

DOI:10.1002/cne.902690103

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractThe termination patterns in the rat phrenic nucleus of neurons within two respiratory cell groups of the ventrolateral medulla (Bötzinger Complex and the rostral ventral respiratory group) were determined. The plant lectin,Phaseolus vulgarisleuco‐agglutinin, was used as an anterograde tracer to label presynaptic processes of bulbospinal neurons, and horseradish peroxidase was used simultaneously to label phrenic motoneurons. Labeled bulbospinal axons ended with dense terminal arborizations within the phrenic cell column and on radial phrenic motoneuron dendrite bundles, which represented the exclusive site of termination of Bötzinger Complex and rostral ventral respiratory group neurons in the lower cervical spinal cord. Terminals of these descending axons formed presumptive synaptic contacts within longitudinal and radial dendrite bundles, and on the cell somata of phrenic motoneur

ISSN:0092-7317    

DOI:10.1002/cne.902690104

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractThe pre‐ and postnatal development of the dopaminergic innervation in the prefrontal cortex (PFC) of the rat is described from embryonic day 14 through postnatal day 90. By embryonic day 15 the dopamine (DA)‐containing fibers reach the anlage of the lateral neocortex; 2 days later the first fibers have reached the subplate of the future prefrontal cortex. The process of entering the cortical plate starts just before birth. Prenatally, some dopaminergic fibers can be observed in the marginal zone of both the lateral and the medial wall of the hemisphere. Within 48 hours after birth a large number of dopaminergic fibers can be observed in the marginal zone, i.e., the future layer I, in some subareas of the PFC. A transient appearance of DA‐positive fibers is noticed in the late embryonic and early postnatal periods especially in the marginal zone and possibly in the superficial layers of the pregenual cingulate cortex. Changes in the morphology of DA fibers at P4 suggest that the actual DA innervation starts at this age. From postnatal day 6 the different subareas of the PFC can be recognized according to the characteristics of the topographical distribution of the dopaminergic fibers. Until postnatal day 60 the density of the dopaminergic fibers continues to increase. No difference in density and topography was observed between postnatal days 60 a

ISSN:0092-7317    

DOI:10.1002/cne.902690105

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractThe distribution and density of the nonretinal projections to the rabbit medial terminal accessory optic nucleus (MTN) have been studied after injections of horseradish peroxidase (HRP) into the MTN in seven rabbits, and confirmation for the presence of certain of these projections has been made in the rabbit or rat by utilizing anterograde transport of tritiated leucine or leucine/proline after appropriate injections into cerebral cortical areas and brainstem nuclei.In seven cases studied by the retrograde axonal transport method, HRP‐labeled neurons have been identified: (A) In four visual or preoculomotor nuclei in which available autoradiographic brain series have confirmed the presence of projections to the MTN: (1) The nucleus of the optic tract/dorsal terminal accessory optic nucleus, (2) the interstitial nucleus of the superior fasciculus (posterior fibers), (3) the periaqueductal gray (including its supraoculomotor portion), and (4) the medial division of the deep mesencephalic nucleus. (B) Within the ventral lateral geniculate nucleus, from which a projection to the MTN has been confirmed autoradiographically in the rat by other workers. (C) In brainstem nuclei and cerebral cortical areas in which available autoradiographic brain series fail to confirm the presence of afferents to the MTN: (1) The nucleus reticularis pontis, pars oralis and pars caudalis, (2) the intermediate interstitial nucleus of the medial longitudinal fasciculus, (3) the nucleus raphe pontis, and (4) five cerebral cortical areas (the area retrosplenialis granularis dorsalis, the striate area, the parietal area 3, the subicular cortex, and the regio praecentralis granularis). Finally, we report retrograde labeling which, on the basis of published connectional data, we believe to result from the spread to and uptake from axonsen passant. The false‐positive labeling in this category is likely to result from spread of HRP into ventral tegmental nuclei or tracts adjacent to the MTN. Thus, as a result, in themedullaandpons, labeled neurons are found in the medial, lateral, and superior vestibular nuclei, the medullary reticular formation including the nucleus reticularis gigantocellularis, the lateral reticular nucleus, the nucleus raphe magnus, the spinal nucleus of V, the nucleus gracilis/nucleus cuneatus, the dorsal and ventral divisions of the parabrachial nucleus, the central pontine gray, the nucleus K of Meessen and Olszewski, and the dorsal nucleus of the lateral lemniscus. In themidbrain, labeled neurons are present in the interstitial nucleus of Cajal and the strata griseum intermedium and profundus of the superior colliculus. In thediencephalonlabeled neurons are found in the posterior and medial pretectal nuclei, the zona incerta, and the ventral lateral geniculate nucleus. Labeled somata also are observed in the caudate‐putamen, fundus striati, lateral preoptic area, and lateral hypothalamic nucleus of thetelencephalonThe present study represents the first comprehensive analysis of the total nonretinal projections to the MTN in any vertebrate species. It provides data whichimpinge in two ways upon other findings that show that the terminal accessory optic nuclei, including the MTN, contain substantial populations of GABAergic neurons and axon terminals: First, in relation to the present demonstration of the nonretinal afferents of the MTN, which may contribute to the GABAergic innervation of MTN neurons, and, second, related to the fact that these nonretinal afferents may activate GABAergic neurons of the MTN (Penny et al.:J. Comp. Neurol. 228:38–56, '84; Giolli et al.:Exp. Brain Res. 61:194–203, '85) triggering a fine tuning of compensatory eye movements to ret

ISSN:0092-7317    

DOI:10.1002/cne.902690106

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractThe timing of the final mitotic division of basal forebrain cholinergic neurons was studied by injecting [3H]thymidine into timed pregnant rats and processing the brains of their progeny as young adults for immunohistochemistry with a monoclonal antibody to choline acetyltransferase (ChAT) followed by autoradiography. ChAT‐positive neurons located caudally in the basal forebrain were found to become postmitotic mostly on embryonic (E) days 12 and 13, whereas the peak final mitosis of more rostrally located ChAT‐positive neurons occurred increasingly later, with the most rostral ChAT‐immunoreactive neurons leaving their final mitotic cycles on E15 and E16. In all basal forebrain regions, cholinergic neurogenesis was complete by E17. These results indicate that the cholinergic neurons in the basal forebrain become postmitotic in a caudal‐to‐rostral gradient over about 5 days. The continuity of the gradient suggests that these cholinergic neurons may derive from the same germin

ISSN:0092-7317    

DOI:10.1002/cne.902690107

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractSensory neurons in dorsal root ganglia of frogs project to areas of the spinal cord they do not normally innervate following removal of adjacent ganglia at tadpole stages (Frank and Westerfield,J. Physiol (Lond.) 324:495–505, '82b). A possible explanation of this phenomenon is that sensory neurons project to wider areas of the spinal cord in tadpoles than in adult frogs and that partial deafferentation causes the retention of these widespread projections. Therefore, the specificity of sensory projections to the spinal cord in tadpoles was assessed by staining individual dorsal roots with horseradish peroxidase. Thoracic sensory neurons project to thoracic segments of the spinal cord and to the brainstem in tadpoles, like thoracic sensory neurons in adult frogs. They rarely arborize in the brachial region even at stages when no other sensory fibers arborize at this level. Furthermore, their projections are restricted to the dorsal horn at all stages. Conversely, hypoglossal sensory neurons, which project into the intermediate gray matter in the adult, also project to this area in tadpoles. The finding that sensory neurons in tadpoles only project to areas of the spinal cord that they innervate in the adult suggests that the novel projections observed following partial deafferentation of the spinal cord are actually induced by the operation. An additional finding was that forelimb afferents, which project to an area extending from the obex to midthoracic levels in adult frogs, arborize at rostral spinal levels and at thoracic levels several stages before they form projections to the region around their own dorsal root. These differences in the stages at which projections to different levels of the spinal cord develop suggest that local properties of the spinal cord may control the timing of sensory fiber arborizatio

ISSN:0092-7317    

DOI:10.1002/cne.902690108

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractIn birds, displaced ganglion cells (DGCs) constitute the exclusive source of retinal input to the nucleus of the basal optic root (nBOR) of the accessory optic system. Tyrosine‐hydroxylase (TH) immunoreactivity was examined in the pigeon retina after injections of rhodamine‐labeled microspheres into the nBOR. A population of about 400 DGCs was observed in each case to exhibit both TH immunoreactivity and rhodamine bead fluorescence. This corresponded to about 10–15% of the total number of identified DGCs in each retina. Double‐labeled cells were medium‐ to large‐size (12 to 20 μm in the largest axis) and were always located at the border between the inner nuclear and the inner plexiform layers. Their dendrites could be followed horizontally in lamina 1 of the inner plexiform layer for up to 300 μm from the cell body. The distribution of double‐labeled DGCs appeared to be mostly peripheral, matching the overall distribution of identified DGCs. Larger DGCs (21–28 μm) were never seen to contain TH immunoreactivity. Examination of brain sections revealed plexuses of thin varicose TH‐positive axons in all subdivisions of the nBOR. Unilateral enucleation produced an almost complete elimination of TH immunoreactivity in the contralateral nucleus. Such results suggest the existence of a population of catecholaminergic DGCs projecting into the accessory optic system of the pigeon. They also support the emerging hypothesis concerning the neurotransmitter heterogeneity of ganglion cells in t

ISSN:0092-7317    

DOI:10.1002/cne.902690109

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractThis study examines the origin of cells in the interauricular granular band (iagb) in the cerebellum of the frog tadpole during early stages of development by means of histological and autoradiographic methods.Premetamorphic bullfrog tadpoles were exposed to multiple doses of3H‐thymidine (10 μCi/g body weight per exposure) at developmental stages ranging from 1 week to 1 year and were killed at either 6 or 12 months of age. The autoradiographic data were examined to determine the time when cells of the iagb were generated.Our findings show that initial generation of iagb cells begins at week 3 and that a peak in the formation of postmitotic neurons is reached at the age of 10 weeks. This is followed by other peaks of cell generation at the ages of 16 weeks, 10 months, and 11.5 months. The generation cycles of iagb cells are interrupted by periods of quiescence when label cannot be detected in any of the cells. These quiescent periods occur at the ages of 20–26 weeks, 7 months, and 12 months. These findings indicate that cells of the iagb are generated in a cyclical manner over the entire 1‐year period which was studied. Comparison of our present data on iagb cell formation with the generation of cells in the EGL shows that the production of these two groups of cells is overlapping, but cells of the iagb begin and cease production before those of the EGL. On the basis of our findings we propose that the cells of the iagb and the EGL belong in separate cell groups which are generated by distinct subpopulations of germinal cells in the neuroepitheli

ISSN:0092-7317    

DOI:10.1002/cne.902690110

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractThis study addressed the issue of whether paralimbic regions of the cerebral cortex share common thalamic projections. The corticothalamic connections of the paralimbic regions of the orbital frontal, medial prefrontal, cingulate, parahippocampal, and temporal polar cortices were studied with the autoradiographic method in the rhesus monkey. The results revealed that the orbital frontal, medial prefrontal, and temporal polar proisocortices have substantial projections to both the dorsomedial and medial pulvinar nuclei, whereas the anterior cingulate proisocortex (area 24) projects exclusively to the dorsomedial nucleus. These proisocortical areas also have thalamic connections with the intralaminar and midline nuclei. The cortical areas between the proisocortical regions on the one hand and the isocortical areas on the other, that is, the posterior cingulate region (area 23) and the posterior parahippocampal gyrus (areas TF and TH), project predominantly to the dorsal portion of the medial pulvinar nucleus, the anterior nuclear group (AV, AM), and the lateral dorsal (LD) nucleus. Additionally, the posterior cingulate and medial parahippocampal gyri (area TH) have projections to the lateral posterior (LP) nucleus.Thus, it appears that the proisocortical areas, which are characterized by a predominance of infragranular layers and an absence of layer IV, have common thalamic relationships. Likewise, the intermediate paralimbic areas between the proisocortex and isocortical regions, which also have a predominance of infragranular layers but in addition have evidence of a fourth layer, project to the medial pulvinar and to the so‐called limbic nuclei, AV, AM, LD, as well as a modality‐specific nucleus,

ISSN:0092-7317    

DOI:10.1002/cne.902690111

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY