摘要:

AbstractThe cerebral cortex and the intralaminar thalamic nuclei are the major sources of excitatory glutamatergic afferents to the striatum, whereas the midbrain catecholaminergic neurones provide a dense intrastriatal plexus of dopamine‐containing terminals. Evidence from various sources suggests that there is a functional interaction between the glutamate‐ and dopamine‐containing terminals in the striatum. The aim of the present study was to determine the synaptic relationships between cortical or thalamic inputs and the dopaminergic afferents in the sensorimotor territory of the monkey striatum. To address this issue, anterograde tracing in combination with immunocytochemistry for tyrosine hydroxylase (TH) was carried out by light and electron microscopy.Squirrel monkeys received injections of biocytin in the primary motor and somatosensory cortical areas or injections of eitherPhaseolus vulgaris‐leucoagglutinin (PHA‐L) or biocytin in the centromedian nucleus (CM) of the thalamus. Sections that included the striatum were processed to visualize the anterograde tracers alone or in combination with TH immunoreactivity. The anterogradely labelled fibres from the cerebral cortex and CM display a band‐like pattern and are exclusively confined to the postcommissural region of the putamen, whereas TH‐immunoreactive axon terminals are homogeneously distributed throughout the entire extent of the striatum. Electron microscopic analysis revealed that the anterogradely labelled terminals from the cerebral cortex form asymmetric synapses almost exclusively with the heads of dendritic spines. The thalamic terminals also form asymmetric synapses, but in contrast to cortical fibres, predominantly with dendrites (67.4%) and less frequently with spines (32.6%). The TH‐immunoreactive boutons are heterogeneous in morphology. The most common type (84% of the total population) forms symmetric synapses; of these the majority is in contact with dendritic shafts (72.1%), less with spines (22.5%) and few with perikarya (5.4%). In sections processed to reveal anterogradely labelled cortical fibres and TH‐immunoreactive structures, individual spines of striatal neurones were found to receive convergent synaptic inputs from both cortical and TH‐immunoreactive boutons. In contrast, anterogradely labelled thalamic terminals and TH‐immunoreactive boutons were never seen to form convergent synaptic contacts on the same postsynaptic structure.These findings suggest that the dopaminergic afferents are located to subserve a more specific modulation of afferent cortical input than afferent thalamic input in the sensorimotor territory of the striatum in primates.

ISSN:0092-7317    

DOI:10.1002/cne.903440102

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

年代:1994

数据来源: WILEY

摘要:

AbstractIn order to define the extent to which retinotopic order in the optic pathways may contribute to fiber segregation at the chiasm or to the formation of central maps, the arrangement of fibers in the optic nerve and tract of rat embryos, on embryonic days 16.5 and 18.5, has been studied by placing a small granule of Dil in one of the four quadrants of the retina and tracing the filled fibers through transverse sections of the retinofugal pathway with confocal microscopy. There is a distinct quadrant‐specific order in the optic stalk immediately behind the eye, with fibers from the ventral nasal, dorsal nasal, dorsal temporal, and ventral temporal retina arranged sequentially across the rostrocaudal axis of the cross section of the stalk. However, this distinct order is not maintained very far. There is a gradual increase in the degree of overlap between fibers from the different quadrants as the fibers pass towards the chiasm. The dorsal groups of fibers intermingle extensively along almost the entire length of the stalk, but the fibers from ventral sectors remain separate until they reach the prechiasmatic region, where the ventral temporal and the ventral nasal fibers spread the throughout the rostrocaudal extent of the stalk and the chiasm. The initial quadrant‐specific order is completely lost at the chiasm. However, beyond the optic chiasm, the fibers are reorganized into another distinct order. In the optic tract, there is a segregation of dorsal from ventral fibers, but the nasal and temporal groups remain intermingled.The results of this study indicate that the earliest fibers in the developing optic tract are arranged according to topographical rules that differ from those obtaining behind the eye. Since all topographical order is lost between these two levels, there must be an active storing mechanism in the region where the chiasm joins the tract. Possibly this mechanism is related to the development of the dorsoventral axis of the topographic maps in the central visual targets. © 1994 Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903440103

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe intercalated cell masses (ICMs) are dense clusters of small GABAergic cells interposed between the basolateral and centromedial nucles groups of the amygdala. Until now, the ICMs have been largely ignored in anatomical studies of the amygdaloid complex. Thus, this study was undertaken to ientify some of their targets by means of tract‐tracing methods combined with immunohistochemical teniques.Wheat‐germ agglutinin conjegated to horseradish peroxidase (WGA‐HRP) was injected into numerous cortical areas and dorsal thalamic nuclei, in the anterior commissure and/or stria terminalis nuclei, and in the caudate nucleus, as wel as into latera and preoptic hypothalamic areas. Very few retrogradely labeled cells were seen in the ICMs following these injections. In contrast, massive retrograde labeling was found in the rostral groups of ICMs after WGA‐HRP injections involving the substantia innominata and horizontal limb of the diagonal band. Furthermore, these retrogradely labeled intercalated cells were also GABA immunoreactive. Results of iontophoretic injections ofPhaseolus vulgaris‐leucoagglutinin (PHA‐L) in the rostral ICMs confirmed that they contribute a massive projection to the entire extent of the substance innominata and horizontal limb of the diagonal band. Electron microscopic observations of ultrathin sections prepared for postembedding GABA or glutamate immunocytochemistry revealed that the ICM terminals labeled with PHA‐L displayed GABA, but not glutamate immunoreactivity, and formed symmetric synapses with dendritic profiles.The present findings constitue the first direct demonstration of an amygdalofgal GABAergic projection to the basal forebrain. Considering that the basal forebrain contains a group of cholinergic and GABAergic neurons collectively projecting to the entire cortical mantle, this GABAergic projection of the ICMs could allow the amygdaloid complex to influence the activity of widespread cortical regions to which it is not directly connected, at least in the cat. © 1994 W

ISSN:0092-7317    

DOI:10.1002/cne.903440104

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

年代:1994

数据来源: WILEY

摘要:

AbstractTo investigate the relationship between the structure and function of neurons in the rostral (gustatory) nucleus tractus solitarii (rNTS), we analyzed the morphological and biophysical properties of rNTS neurons by performing whole‐cell recordings in a brain slice preparation. Overall, neurons (n=58) had a mean somal diameter of 16 μm, an average dendritic length of 598 μm, an average dendritic thickness of 0.91 μm, and a spine density of 0.037 spines/μm. Neurons were separated into three groups (elongate, miltipolar, and ovoid) on the basis of previously established morphological criteria. The highest percentage (49%) of neurons were classified as ovoid, while 35% were multipolar and only 16% were elongate.The most frequently ovserved firing pattern, in all three cell types, elicited by a 1,200 ms, 100 pA depolarizing current pulse was a regularly firing spike train. However, the intrinsic firing properties of the remaining neurons were different. Thirty‐one percent of the ovoid neurons responded with a short burst of action potentials and 44% of the elongate neurons showed a delay in the onset of the spike train following a hyperpolarizing prepulse. Less than 16% of the multipolar neurons demonstrated either of these firing characteristics.Therefore, rNTS neurons with similar morphology do not have unique biophysical properties. However, the data suggest that there may be subpopulations of the three morphological types, each of which displays a different firing pattern. Since the structure and function of the three morphological groups were not strictly correlated, these subpopulations may represent functional groups. © 1994 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903440105

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe purpose of the present study was to determine the numbers of descending brainstem projections to different levels of the spinal cord in normal larval sea lamprey (Petromyzon marinus) and to examine the restoration of these projections in animals 3–32 weeks after transection of the rostral spinal cord ( ∼ 10% of body length). In normal animals approximately 1, 250, 900, and 825 brainstem neurons projected to 20%, 40%, and 60% of body length, respecively. Spinal projections originated from the diencephaln, mesencephalon, three rhombencephalic reticular nuclei, Müller and Mauthner neurons, and four cell groups in the caudal rhombencephalon. In spinal cord‐transected animals the number of brainstem neurons projecting to 20% of body length increased with recovery time, and at 32 weeks post‐transection the total number and distribution of brainstem neurons was not significantly differnt from normal animals. Brainstem projections first appeared at 40% of body length by 8 weeks post‐transection, and were present at 60% of body length by 32 weeks post‐transection. There was substantial restoration of brainstem projections to 40% of body length but limited restoration to 60% of body length. The ∼ 50 brainstem neurons, including some Müller cells, that projected to 60% of body length at 32 weeks post‐transection indicate that restoration of descending projections in excess of 50 mm can occur within the central nervous system of this vertebrate. These anatomical results are discussed in relation to the time course of recovery of locomotor functions in spinal cord‐transected lampreys. ©

ISSN:0092-7317    

DOI:10.1002/cne.903440106

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

年代:1994

数据来源: WILEY

摘要:

AbstractSpherical and globular cells in the cochlear nucleus provide input to the cell groups in the superior olivary complex devoted to the analysis of binaural cues. Desending projections from the superior olivary complex appear to inhibit the spherical and globular cells. It is not known which of the numerous cell types in the superior olive provide this descending input, but recent studies have shown that some of the cells are located in the medial nucleus of the trapezoid body (MTB). The present experiments were designed to determine whether the MTB projections arise from principal cells, which are known to play a role sound localization, and to determine whether their projections terminate on spherical or globular cells.Principal cells in the MTB are characterized by their contacts with synaptic specializations called calyces, which arise from the axons of cells in the contralateral cochlear nucleus. In the first experiment, a fluorescent tracer was injected into one cochlear nucleus to label the calyces anterogradely. A dfferent tracer was injected into the opposite cochlear nucleus to label cells retogradely in the MTB. In every case, some of the labeled cells were enveloped by a labeled calyx, demonstrating that principal cells do project to the cochlear nucleus. In the second experiment, fluorescent tracers were injected into different parts of the cochlear nucleus. Anaysis of the distribution of labeled cells suggested that MTB projections selectively target the globular cell region of the cochlear nucleus. In a third experiment, the axonal arborizations arising from this projection were labeled with biocytin or wheat germ agglutinin conjugated to horseradish peroxidase. Labeled boutons appeared to contact globular cels but not spherical cells. Multipolar cells in the ventral cochlear nucleus and cells in the dorsal cochlear nucleus were also contacted.The results suggest that MTB projections to the cochlear nucleus arise largely from principal cells and contact, at least in part, cells in the cochlear nucleus that give rise to ascending pathways involved in sound localization. © 1994 Wiley‐Liss, I

ISSN:0092-7317    

DOI:10.1002/cne.903440107

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

年代:1994

数据来源: WILEY

摘要:

AbstractWe have analyzed the early development of the main hippocampal afferents in the mouse. Following injections of the lipophilic tracer 1–1′‐dioctadecyl‐3, 3, 3′, 3′‐tetramethylindocarbocyanine perchorate (DiI) in the entorhinal cortex, entorhinal axons were observed for the first time inthe hippocampus at E15, in the white matter, At E17, entorhinal fibers arborized within the stratum lacunosum‐moleculare. At subsequent stages entorhinal axons formed dense networks that were restricted to their appropriate termination zone in the lacunosum‐moleculare. The first axons invading the fascia dentata were noticed at E19, their density increasing at later stages. These axons were mainly present in the outer molecular layer. This onset of entorhinohippocampal projections was corroborated by retrograde labeling data after injections in the hippocampus. Commissural fibers first entered the contralateral hippocampus at E18, their number increasing at the following stages. Commissural axons arborized within the stratum oriens and radiatum in the hippocampus proper. In the fascia dentata, the earliest commissural fibers were seen at P2, terminating in the inner zone of the molecular layer and in the hilus. We conclude that developing entorhinal and commissural axons show a high degree of laminar specificity from the earliest stages of formation, which is compatible with the notion that distinct subsets of early maturing neurons populating the hippocampal plexiform layers may attract particular fiber systems.Hippocamposeptal fibers develop at E15, before the first septal fibers can be detected in the hippocampus. These early hippocamposeptal fibers originated from nonpyramidal neurons and terminated in the medial septal area, which is the main source of septal afferents to the hippocampus. In contrast, septohippocampal fibers were not seen in the hippocampus until E17. At perinatal stages, the hippocamposeptal connection reshapes, sending axons to the dorsolateral septal area as the innervation of the medial septum becomes less conspicuous. This sequence suggests that hippocampal neurons pioneer the formation of septohippocampal connections. © 19

ISSN:0092-7317    

DOI:10.1002/cne.903440108

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

年代:1994

数据来源: WILEY

摘要:

AbstractWe determined the regional distribution of the dopamine D2receptor group in the rat central nervous system by quantitative receptor autoradiography with a high‐affinity and selective antagonist, [3H]YM‐09151‐2. Saturation and competition experiments demonstrated that the binding of [3H]YM‐09151‐2 to striatal sections was saturable (Bmax=37.3 fmol/section), of high affinity (Kd=0.315 nM), and was inhibited selectively by prototypic D2ligands.The anatomical localization of binding sites was determined by comparison of autoradiograms and the original3H‐ligand‐exposed sections stained with cresyl violet. Very high levels of [3H] YM‐09151‐2 binding were found in the caudate‐putamen, nucleus accumbens, tuberculum olfactorium and the insula of Calleja, to each of which midbrain dopaminergic neurons project densely. High levels of binding were also observed in other regiions rich in dopaminergic neurons and fibers including the glomerular layer of the olfactory bulb, the intermediate lobe of the pituitary, lateral septum, substantia nigra pars compacta, interfascicular nucleus, dorsal raphe nucleus, locus coeruleus, and nucleus of the solitary tract. Some regions poor in dopaminergi innervation, however, had high levels of [3H]YM‐09151‐2 binding including the molecular layer of gyrus dentatus, all layers of CA1 and the nonpyramidal layer of CA4 of hippocampus, and the deeper layer of medial entorhinal cortex. Motor neurons present in brainstem motor nuclei and spinal ventral horn were also strongly labeled. Neocortical, cerebellar, and thalamic regions had low levels of binding, except lobules 9–10 of the cerebellum, the olivary pretectal nucleus, zona incerta and lateral mammillary nucleus, in which moderate to high levels of binding were detected. Our findings concerning the widespread but region‐specific localization of [3]YM‐09151‐2 binding sites in the brain and spinal cord may prove useful for analyzing varoius dopaminergic functions in the central nervous

ISSN:0092-7317    

DOI:10.1002/cne.903440109

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe in vitro turtle brainstem‐cerebellum preparation has been a valuable tool in the study of central motor programs. In the present study, we investigate the anatomical organization of the turtle rubrocerebellar limb premotor network and its sensory connections in vitro by combining the rapid anterograde and retrograde transport of neurobiotin and biocytin with the extended viability of the isolated turtle brainstem‐cerebellum. These compounds retrogradely labeled soma, dendrites, and axons, and orthogradely labeled axons and, to a lesser extent, terminals.The chelonian red nucleus receives a dense input form the contralateral lateral cerebellar nucleus and projects heavily to the contralateral spinal cord. Rubral axons sparsley innervate the lateral cerebellar nucleus and project heavily to the lateral reticular nucleus. Lateral reticular axons heavily innervate the lateral cerebellar nucleus before terminating in the pars laterlalis of the cerebellar cortex as mossy fibers. These prominent, recurrent loops among the lateral cerebellar nucleus, red nucleus, and lateral reticular nucleus constitute the turtle rubrocerebellar limb premotor network.Sensory inputs to the red nucleus orginate in the contralateral dorsal column nuclei, the principle trigeminal nucleus, and the spinothalamic system. These sites project bilaterally to the lateral reticular nucleus. The lateral cerebellar nucleus receives a contralateral input from the dorsal column nuclei. The red nucleus projects sparsely to the dorsal column nuclei.The red nucleus also receives an ipsilateral descending projection from the suprapeduncular nucleus, located in the diencephalon, and an ascending input from the rostral rhombencephalic reticular formation. An ipsilateral descending pathway originating in the red nucleus is likely to be the rubro‐olivary tract. © 1994 Wiley‐L

ISSN:0092-7317    

DOI:10.1002/cne.903440110

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

年代:1994

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.903440111

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

年代:1994

数据来源: WILEY