摘要:

AbstractThe neuronal morphology of the rat subthalamic nucleus (STH) was studied using Golgi techniques and Nissl stain. The results show that the somatic shapes of STH neurons vary from fusiform to oval or polygonal. Soamtic cross‐sectional areas vary between 140 μm2and 440 μm2. Some of the cells have a few somatic spines. Two to six primary dendrites gave rise to tapering daughter dendrites which extend up to 500 μm. These dendrites are sparsely covered with spines. Some distal dendrites and primary dendrites of the STH also bear filiform appendages. Neurons located in the deep portion of the STH have oval dendritic fields whose long axis is parallel to the long axis of the nucleus in frontal or sagittal planes. Some of these neurons have one or two dendrites which cross the borders of the STH into the zona incerta, the lateral hypothalamus, or the cerebral peduncle. Generally, neurons located at the borders of the STH have their dendritic fields extending parallel to the borders and are confined to the nucleus. However, some neurons adjacent to the ventrolateral border of the nucleus have some dendrites extending into the cerebral peduncle. Quantitative analysis of the STH neurons showed a unimodal distribution of somatic sizes as well as the number of primary dendrites. No neurons with obvious Golgi type II characteristics were found.Two types of afferent fibers were observed entering the STH. One type consists of axon collaterals arising from the cerebral peduncle ventrolaterally, or the internal capsule rostrally, while the other enters the nucleus after crossing the internal capsule rostrally.These results suggest that the rat STH is an open nucleus in contrast to other species such as man, monkey, and cat, where it is closed, and that the rat STH may contain only one type of ne

ISSN:0092-7317    

DOI:10.1002/cne.902360102

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

年代:1985

数据来源: WILEY

摘要:

AbstractCorticosubthalamic projections in the rat were investigated using the autoradiographic anterograde axonal tracing technique. After unilateral injections of tritiated amino acids in the cerebral cortex, projections to the ipsilateral subthalamic nucleus (STH) could be found arising only from the frontal agranular cortex and the zone of MI‐SI overlap. Injections into granular areas of the cortex (e.g., somatosensory and visual areas) did not result in labeling in STH. Following injections in the frontal agranular cortex, labeling was present in the ipsilateral but not the contralateral STH. In general, injections that involved the lateral agranular field of frontal cortex, as defined by Donoghue and Wise (1982), resulted in a greater amount of labeling in STH than injections within the medial agranular area or the zone of MI‐SI overlap. The projection from the frontal agranular areas to STH is topographically organized. The rostral part of the lateral agranular cortex projects to the lateral portion of the rostral two‐thirds of STH, and the caudal part of this field projects to the ventral aspect of the middle third of STH. Injections in the rostral part of the medial agranular cortex resulted in labeling throughout the ventral two‐thirds of the medial half of STH. The caudal part of the medial agranular cortex projects to the dorsolateral part of the caudal two‐thirds of STH.The present results reveal projections from only the frontal agranular cortex and the zone of MI‐SI overlap to STH in the rat. The cortico‐STH projection is ipsilateral and terminates in a topographical manner in all

ISSN:0092-7317    

DOI:10.1002/cne.902360103

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

年代:1985

数据来源: WILEY

摘要:

AbstractHorseradish peroxidase conjugated to wheat‐germ lectin is being used with increasing frequency as an anterograde label to trace pathways in the nervous system, owing to the sensitivity of the method and ease of use. However, it has been suggested that horseradish peroxidase conjugated to wheat‐germ lectin may be transneuronally transported, thus affecting the ease of interpretation of the results. The present study used the projections of the dorsal column nuclei and spinal cord to the thalamus as a model system to determine whether transneuronal transport could be demonstrated and whether the degree of such transport was related to the size of the injection site.Light microscopic observation of sections incubated with tetramethyl benzidine after large injections (1 μL of a 10% solution of horseradish‐peroxidase‐conjugated wheat‐germ lectin in water) in the dorsal column nuclei demonstrated the presence of labeled neurons in the nucleus reticularis thalami, which is not known to receive afferents from or project to these nuclei. The electron microscopic study, although based upon the use of the chromogen benzidine dihydrochloride, less sensitive than tetramethyl benzidine, revealed the existence of labeled neurons in the thalamic ventrobasal complex. This is unlikely to be due to retrograde labeling and is therefore interpreted as a result of transneuronal, perhaps transsynaptic, transport. Glial and perivascular cells also contained granules of reaction product in some cases. Smaller injections (100 nL) in the dorsal column nuclei, on the other hand, did not produce this apparent transneuronal labeling.After small injections (100 nL) in the spinal cord, anterograde labeling was observed mainly in the thalamic ventrobasal complex in the rat, and in the posterior group in the cat, and the nuclei centralis lateralis and submedius in both species, as has been described in numerous other studies. After large injections, additional labeled areas were observed in the posterior intralaminar region (parafascicular‐center median complex), in the medial thalamus (nuclei reuniens, rhomboid and paraventricular), and in the cat, in the ventroposterolateral nucleus. In the rat, experiments were performed in which a kainic acid injection was made to induce neuronal loss in the nucleus reticularis gigantocellularis of the medulla, which is a relay of the spinoreticulothalamic pathway, known to project to some of these thalamic areas. After such lesions and large spinal injections of horseradish‐peroxidase‐conjugated wheat germ lectin, labeling was clearly decreased in some of these additional sites of projection and not in the areas which contained labeling after small injections, thus demonstrating that nucleus reticularis gigantocellularis neurons are necessary for some of the additional labeling. N‐methyl DL aspartic acid was applied to the spinal cord in other rats, destroying dorsal horn neurons but not axons of other systems. Horseradish‐peroxidase‐conjugated wheat germ lectin injected into the spinal cord of these animals resulted in retrograde labeling of brain stem neurons, but the loss of labeled fibers in the thalamus, which suggested that collaterals of brain stem neurons are not the source of transport of the tracer from cord to medial thalamus.The results of the present study suggest the possibility of significant transneuronal labeling when horseradish‐peroxidase‐conjugated wheat germ lectin is used to trace anterograde transport in somatosensory pathways, especially when large volumes of it are injected. Thus, it is necessary to interpret the results of these tract‐tracing experiments with caution. Some mechanisms which may subserve such transne

ISSN:0092-7317    

DOI:10.1002/cne.902360104

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

年代:1985

数据来源: WILEY

摘要:

AbstractRetinal ganglion cells were labeled retrogradely by localized injections of HRP into different regions of the pretectum, tectum, and optic tract in 26 cats. Retinal projection zones in the pretectum were labeled anterogradely in the same cats by intravitreal injections of3H‐proline. This allowed the HRP injection sites to be located with respect to the retinal termination zones.The form of the projection zones from retina to pretectum was determined from serial reconstructions of either coronal or horizontal sections. The zones are best distinguished in horizontal sections, where they are seen as four roughly parallel strips on either side of the brain. They are more‐or‐less parallel to the anterior border of the tectum, and appear to traverse the entire width of the retinal projection to the tectum. Each zone is similar in form for the ipsilateral and contralateral projections, although the contralateral projection is thicker and denser. Binocular injections of3H‐proline showed that the projections from the two eyes were in register and did not interdigitate.Cells labeled by HRP injections in the anteromedial end of the pretectum were concentrated in the lower nasal quadrant of the contralateral retina, and the lower temporal quadrant of the ipsilateral retina. Posterolateral injections labeled cells in the upper quadrants. There is thus a rough retinotopic mapping along the elongated axis of the pretectum. When the distributions of ganglion cells labeled by HRP injections to different parts of the pretectum are combined, they show a concentration in both the visual streak and area centralis, and thereby reflect, at least qualitatively, the relative spatial distribution of the entire ganglion‐cell population. About 85% of the retinal projection to the pretectum is contralateral. For all of the HRP injections, the spatial density of labeled cells was always low, accounting for no more than 3% of the total spatial density of ganglion cells in any retinal region.Several types of ganglion cells were labeled following injections to most regions of the pretectum; these included alpha, beta, and epsilon cells, as well as small‐bodied cells showing a variety of morphologic forms. Alpha cells were labeled mainly from the anterolateral end of the pretectum, but other cell types were labeled from all injected regions. In the peripheral retina, 2% of the labeled cells were alpha cells, 32% were beta cells, 19% were epsilon cells, and the remaining 47% were small cells whose dendrites only occasionally filled to any significant extent.Interpretation of the HRP findings is necessarily complicated by the fact that fibers of passage to the tectum pass through the entire extent of the retinal projection zones to the pretectum. Some of the ganglion cells that projected only to the pretectum were undoubtedly labeled as well. However, injections into the pretectum labeled a significantly higher proportion of beta and epsilon cells (51%) than did tectal injections (22%), thus suggesting that the uptake by axonal terminals was greater than the uptake by nonter‐minating fibe

ISSN:0092-7317    

DOI:10.1002/cne.902360105

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe distribution of serotonin‐like immunoreactivity in five regions of the rodent midbrain periaqueductal gray (PAG) was studied by using light and electron microscopic immunohistochemistry in combination with quantitative analysis. Light microscopic analysis revealed the presence of serotonin‐like immunoreactive cell bodies located in the ventrolateral and ventromedial regions of the caudal PAG and serotonin‐like immunoreactive processes throughout the PAG. Ultrastructural analysis showed dendritic profiles that stained positively for serotonin primarily in ventral regions, although an occasional profile was seen dorsally. Numerous synaptic contacts between unstained axon terminals and ventral dendritic profiles were seen. Axonal profiles that contained reaction product were identified throughout the PAG, but were rarely observed to make any type of specialized contact. Ultrastructural quantification of serotonin‐like immunoreactive processes indicated that the highest volume fraction of serotonin immunoreactivity occurred caudoventrally where stained processes constituted 2.6% of the neuropil volume. Rostroventrally stained processes constituted only 0.14% of the neuropil volume at the level of the posterior commissure. By contrast the amount of serotonin‐like immunoreactivity found dorsally remained relatively constant at all rostrocaudal levels. Analysis of serotonin staining among PAG regions demonstrated the lowest overall volume friction in the dorsal region and the highest overall volume fraction in the ventromedial region. No significant differences were observed between medial and lateral regions. A comparison of the results of light microscopic quantitative analysis of serotoninergic processes with electron microscopic quantitative analysis indicated that both techniques produce comparabl

ISSN:0092-7317    

DOI:10.1002/cne.902360106

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe distribution of neuropeptide Y (NPY) immunoreactivity in the brain of the squirrel monkey (Saimiri sciureus) was studied by means of the indirect immunofluorescence, peroxidase‐antiperoxidase, and avidin‐biotin‐complex methods. The antiserum used was raised in rabbits and did not show any significant crossreactivity with related peptides including peptide YY and avian pancreatic polypeptide.In theupper brainstemof the squirrel monkey a dense NPY‐immunoreactive terminal field is seen in lateral parabrachial area, locus coeruleus, and interpeduncular nucleus. A small group of NPY‐immunoreactive cell bodies is present in the lateral habenula and a moderate number of NPY‐immunoreactive fibers occurs in periaqueductal gray and nucleus raphe pallidus. The substantia nigra (SN) appears mostly devoid of NPY immunoreactivity whereas the ventral tegmental area contains a few reactive fibers. In thehypothalamusthe medial preoptic area as well as the arcuate and paraventricular nuclei receive a strikingly dense NPY innervation. In addition, numerous NPY‐positive cell bodies are found within the dorsomedial half of the supraoptic nucleus but very few are seen in paraventricular nucleus. A large number of NPY‐immunoreactive cell bodies is also present in arcuate nucleus. In thebasal telencephalonNPY‐immunoreactive cells abound mostly in striatum, but some are also found in the amygdala (particularly basal, central, and lateral amygdaloid nuclei), the claustrum, and in the bed nucleus of the stria terminalis. Intensely reactive network of NPY‐immunoreactive fibers is also present in all of these structures. In striatum, the numerous, fine and nonvaricose NPY‐immunoreactive fibers, as well as the NPY‐positive cell bodies, are slightly more abundant in caudate nucleus than in putamen. The globus pallidus (GP) is mostly devoid of NPY‐immunoreactive fibers and terminals. The fact that the two major recipient structures of striatal outflow (SN and GP) do not receive significant NPY input suggests that the striatal NPY‐containing neurons

ISSN:0092-7317    

DOI:10.1002/cne.902360107

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

年代:1985

数据来源: WILEY

摘要:

AbstractThis study describes the differentiation of photoreceptors in larval goldfish retina. The earliest photoreceptors to differentiate were cones;3H‐fucose labeled cone but not rod outer segments in larval as well as adult goldfish. All major cone types known to be present in the adult goldfish retina (double cones, long and short single cones) were found in the larval retina by 2 days after hatching. The cones matured rapidly; within a few days they had well‐developed outer segments and synaptic pedicles that were smaller, but otherwise similar to those in adults. Rods were slower to mature. Their outer segments were at first short, wide, and misshapen; only as they grew longer and narrower did they become straight and properly aligned. Rod spherules were first seen in fish older than 1 month; immature rods contained perinuclear synaptic ribbons and invaginating processes penetrated the cell body. These results suggest that the influence of rods and cones on visual function in larval goldfish may be quite different from the ad

ISSN:0092-7317    

DOI:10.1002/cne.902360108

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

年代:1985

数据来源: WILEY

摘要:

AbstractLocation of the neurons in the trigeminal mesencephalic nucleus innervating stretch receptors of the lateral pterygoid muscle and the mode of their synaptic connection on the lateral pterygoid motoneurons of the guinea pig were studied physiologically as well as morphologically, in comparison with the trigeminal mesencephalic neurons innervating muscle spindles in the superficial masseter muscle, with the following results: (1) stimulation of the caudal half of the trigeminal mesencephalic nucleus evoked monosynaptic excitatory postsynaptic potentials in the ipsilateral lateral pterygoid motoneurons. (2) Stimulation of the lateral pterygoid nerve directly evoked spike potentials in the neurons located in the caudal half of the ipsilateral trigeminal mesencephalic nucleus, which responded with increased firing to stretch, and with silent period to twitch, of the ipsilateral lateral pterygoid muscle. (3) Averaging of intracellular potentials of the lateral pterygoid motoneurons with extracellular spike potentials of these trigeminal mesencephalic neurons revealed excitatory postsynaptic potentials after a monosynaptic latency, but no inhibitory postsynaptic potentials. (4) Injection of horseradish peroxidase into the lateral pterygoid muscle labeled 15–20 cells in the caudal half of the ipsilateral trigeminal mesencephalic nucleus, while 174–228 cells retrogradely labeled by horseradish peroxidase were found throughout the whole rostrocaudal extent of the ipsilateral trigeminal mesencephalic nucleus following injection of horseradish peroxidase into the masseter muscle. It was concluded that neurons in the caudal half of the trigeminal mesencephalic nucleus send their peripheral processes to stretch receptors, presumably muscle spindles, in the ipsilateral lateral pterygoid muscle and that their central processes have excitatory synapses on ipsilateral lateral pterygoid motoneurons, thus comprising the afferent limb of a monosynaptic stretch reflex arc of the lateral pterygoid muscle of the guinea

ISSN:0092-7317    

DOI:10.1002/cne.902360109

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

年代:1985

数据来源: WILEY

摘要:

AbstractBlack and white Lister hooded rats were undernourished from the 16th day of gestation until 25 postnatal days of age. These previously undernourished rats and a set of well‐fed rats were later subjected to 30 days of environmental diversity, i.e., environmental enrichment or isolation. Two separate experiments were carried out. In experiment 1, the environmental diversity lasted from 85 to 115 days of age and in experiment 2, from 35 to 65 days of age.At the end of the period of environmental diversity, all rats were killed by perfusion with 2% phosphate‐buffered glutaraldehyde. Small pieces of tissue from the right visual cortex were embedded in Spurr's resin. For each rat two blocks of resin‐embedded tissue were randomly selected, and from these semithin sections (0.5 μm) were cut and stained with toluidine blue. Photomicrographs of cortical layers II and III were taken from these sections and used to estimate the numerical density of neurons. Ultrathin (ca. 70 nm) sections of the same region of the cortex were cut and stained with lead citrate. These sections were used to estimate the synaptic disc diameter and numerical density. Synapse‐to‐neuron ratios were calculated from the estimates of synaptic and neuronal numerical densities.In experiment 1, well‐fed rats raised in enriched environments had a significantly smaller neuronal numerical density and a greater synaptic disc diameter than well‐fed rats raised in an impoverished environment. In experiment 2, neither the well‐fed nor previously undernourished rats showed significant effects of environmental treatment on any of the features studied. The statistical interaction between nutrition and environment was not significant for any of the features in e

ISSN:0092-7317    

DOI:10.1002/cne.902360110

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

年代:1985

数据来源: WILEY

摘要:

AbstractImmunocytochemical procedures have been used to examine the distributions of substance P (SP)‐positive fibres within the intermediate zone of the thoracolumbar spinal cords of rabbits, cats, and monkeys. In all three species SP fibres were concentrated in areas known to contain sympathetic preganglionic neurones. These included the intermediolateral nucleus and the funiculus just lateral to it, the medial gray matter in the area of the nucleus intercalatus, and the paracentral region. The density of the SP innervation varied in a characteristic way both between these subpopulations of sympathetic neurones and in its overall input to different segmental levels. Generally the greatest accumulations of SP fibres were found in the T3–T5and L2–L4regions and these were concentrated in the intermediolateral nucleus (ILN). The highest densities of SP fibres in the lateral funiculus were in the upper thoracic and upper lumbar segments whereas SP fibres forming transverse bands, possibly in association with neurones in the nucleus intercalatus, were most prominent in T5–T8. Substance P fibres adjacent to the midline were more or less equally dense throughout the segments examined. Substance P‐positive cell bodies situated immediately lateral to the central canal were present at a density of 200–300 per segment throughout the cat thoracolumbar cord. These neurones may be the cells of origin of at least some of the SP fibres in the intermediate zone. The close association of sympathetic preganglionic neurones with SP fibres, many of which are thought to be derived from cells in the medulla, suggests a role for SP‐containing fibres in the modulation of sympathetic activity. The variation in input to different segments and classes of sympathetic neurones further suggests a specificity which may be related to the different functions of the neuron

ISSN:0092-7317    

DOI:10.1002/cne.902360111

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

年代:1985

数据来源: WILEY