摘要:

AbstractThe striatopallidal projection originating in the nucleus accumbens was investigated by using anterograde transport of PHA‐L in combination with peptide immunohistochemistry in order to localize the injection sites and transported lectin with respect to neurochemically defined subterritories in the nucleus accumbens and subcommissural ventral pallidum. The results reported here supplement our previous observations, which indicated that the subcommissural ventral pallidum of the rat comprises two immunohistochemically defined subterritories (Zahm and Heimer, '88: J. Comp. Neurol., 272:516–535) which give rise to dichotomous downstream projection systems (Zahm, '89: Neuroscience, 30:33–50). The present data indicate that the neurotensin immunoreactivity‐rich ventromedial district of ventral pallidum receives its accumbal input almost exclusively from the shell district of the nucleus accumbens. The accumbal core, alternatively, projects to the dorsolateral ventral pallidal subterritory that lacks appreciable neurotensin immunoreactivity and in many other respects more resembles the adjoining striatopallidal components of the caudate‐putamen. In addition to direct topographic relationships in the frontal plane among the accumbal injection sites and ventral pallidal terminations, it was observed that more caudally placed core injections resulted in patches of striatopallidal terminations that were more caudally located in ventral pallidum. Shell injections, in contrast, produced columns of terminations that extended continuously from the rostralmost level that they appeared to the caudal end of ventromedial ventral pallidum. The accumbal shell, its exclusive projection to the ventromedial subterritory in the subcommissural ventral pallidum, and the previously reported, almost exclusive projection of that pallidal subdistrict to the mesencephalic ventral tegmental area are discussed in terms of a number of other neurochemical and hodological features that serve to distinguish them sufficiently to suggest that they represent a uniquely specialized part of the basa

ISSN:0092-7317    

DOI:10.1002/cne.903020302

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe anatomy and physiology of neurones with axons in left and right homologous nerves was studied in abdominal ganglia of the migratory locust,Locusta migratoria, by using a differential cobalt/nickel staining method. These neurones reside within two clusters at the anterior and posterior ends of all unfused abdominal ganglia. Each cluster contains at least seven neurones with bilaterally projecting axons.All neurones of the anterior cluster possess bilaterally projecting axons which leave the ganglion through nerve 2 (=sternal nerve) or nerve 1 (=tergal nerve). Additional axon collaterals, which are present in some of these neurones leave through either nerve 1 or nerve 2 of the right or left side of the ganglion. With few exceptions, the neurones show further asymmetries in their dendritic arborizations.Neurones of the posterior group also have bilaterally projecting axons that leave the ganglion through nerve 1 or nerve 2. Among these neurones are the two large posterior dorsal unpaired median (DUM) neurones with bilaterally symmetrical axons that were described earlier as DUM1 and DUM2. They innervate the skeletal muscles of an abdominal segment. Two other cells of this cluster have anatomical properties similar to the DUM1 neurone and were termed DUMheart1A and DUMheart1B. The rest resemble the bilaterally projecting neurones of the anterior group.With the exception of the two classic DUM neurones (DUM1 and DUM2), all neurones of the anterior and posterior cluster innervate the heart or a neurohaemal area.

ISSN:0092-7317    

DOI:10.1002/cne.903020303

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractPrevious studies have reported considerable plasticity in the rodent corticospinal pathway in response to injury. This includes sprouting of intact axons from the normal pathway into the contralateral spinal cord denervated by an early corticospinal lesion. We carried out the present study to obtain detailed information about the time course, origin, and degree of specificity of corticospinal axons sprouting in response to denervation. Hamsters (Mesocricetus auratus) ranging in age from 5 to 23 days received unilateral lesions of the left medullary pyramidal tract. Two weeks after the lesion, small regions of the right sensorimotor cortex opposite the lesion were injected with the plant lectinPhaseolus vulgarisleucoagglutinin (PHA‐L). After a further 2 week survival period, immunohistochemistry was carried out on frozen sections of the fixed brains and spinal cords. Detailed morphological analysis of PHA‐L labeled corticospinal axons revealed that sprouting from the intact corticospinal pathway into the contralateral denervated spinal cord occurred only at local spinal levels and not at the pyramidal decussation. Arbors sprouting into the denervated cord frequently arose from corticospinal axons that branched into the normal side of the cord as well. Sprouting was maximal after early lesions (5 days) and declined with lesions at later ages up to 19 days. Sprouting corticospinal axons arborized with the same degree of functional and topographic specificity as previously reported for normal corticospinal arbors (Kuang and Kalil:J. Comp. Neurol.292:585–598, '90), such that axons arising from somatosensory cortex projected only to the dorsal horn, those from motor cortex innervated only the ventral horn, and normal forelimb and hindlimb topography was preserved. Sprouting fibers also had normal branching patterns. Parallel studies of developing corticospinal arbors showed that sprouting could not be attributed to maintenance or expansion of early bilateral connections. These results suggest that local signals, most likely similar to those governing normal corticospinal development, elicit corticospinal sprouting and determine specificity of axon a

ISSN:0092-7317    

DOI:10.1002/cne.903020304

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractCobaltic‐lysine complex was used to label the afferent and efferent components of the glossopharyngeal nerve in the ganglion and brainstem of the Mexican salamander, axolotl (Ambystoma mexicanum). The distribution of afferent cell bodies in the combined glossopharyngeal‐vagus ganglion (the IX‐X ganglion) was reconstructed from serial sections, and the sizes of the cell bodies were measured. The central projection of afferents and the location of efferent cell bodies were determined by the tracer.The afferent cell bodies in the ganglion were medium‐sized (ca. 25 μm). Cell bodies with a single process were seen. The ganglion was not clearly divided into superior and inferior ganglia, as is observed in mammals and frogs, but comprised a single ganglion. Labelled cells were diffusely distributed in the rostral part of the IX‐X ganglion. A few labelled cells also were seen in the caudal part, where the vagus nerve fibers and cell bodies were mainly distributed. Double labellings of the glossopharyngeal and vagus nerves with HRP and cobaltic‐lysine demonstrated that the ganglion cells of each nerve are not clearly separated in the IX‐X ganglion. In the brainstem, the majority of afferent fibers formed thick ascending and descending limbs in the solitary fasciculus. The remaining afferent fibers formed a thin bundle in the spinal tract of the trigeminal nerve, which had a short ascending limb and a long descending limb. These two bundles had terminal areas in the ipsilateral brainstem: in the dorsal gray matter for the solitary fasciculus and in the lateral funiculus for the spinal tract of the trigeminal nerve, respectively. The cell bodies of the efferent neurons possessed developed dendritic arborizations in the ventrolateral white matter, and formed a longitudinal cell column in the ventrolateral margin of the gray matter. Thus, the glossopharyngeal nerve system in the axolotl assumes a primordial form in its ganglions, but its topographical organization in the brainstem is basically similar to t

ISSN:0092-7317    

DOI:10.1002/cne.903020305

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractIn Nembutal‐anesthetized, immobilized, and artificially ventilated cats, we studied the morphological characteristics of inspiratory neurons with nonaugmenting firing patterns. HRP was injected intracellularly into a total of 22 neurons of the Bötzinger complex (BÖT) and the ventral respiratory group (VRG). In 20 cases somata with their axonal trajectories were stained, and in two cases only axons were stained. None of the neurons stained could be antidromically activated by stimulation of the cervical cord. The somata of 20 neurons were located in the vicinity of the nucleus ambiguus or the retrofacial nucleus (RFN) between 600 μm and 2,800 μm caudal to the rostral end of the RFN. Their axons could be traced for a distance of several millimeters on the side of the somata, and showed various projection patterns. According to these projection patterns, the 20 neurons were tentatively classified into four groups: A (8/20), B (4/20), C (6/20), and motoneurons (2/20). Group A neurons gave off extensive axon collaterals that arborized and distributed boutons predominantly in the BÖT and the VRG areas. Group B neurons had less extensive axon collaterals with various projection patterns, projecting rarely to the BÖT or the VRG area. Group C neurons sent their stem axons, without issuing any axonal collaterals, to the contralateral side in five cases and to the ipsilateral pons in one case. The two motoneurons had axons leaving the brainstem without any intramedullary collaterals. Thus, the nonaugmenting inspiratory neurons showed morphological variations, which may play different roles in neural control of resp

ISSN:0092-7317    

DOI:10.1002/cne.903020306

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractWe studied the terminal patterns of single, physiologically identified geniculocortical axons in the striate cortex of the tree shrew by using intracellular recording and labeling methods. Axons were classified by their response to the onset (ON‐center) or offset (OFF‐center) of a light stimulus presented to the ipsilateral or contralateral eye. Then, we attempted to penetrate each axon for labeling with horseradish peroxidase. We recovered 23 axons and studied 16 of these in detail. Light microscopic reconstructions of these axons revealed several distinct terminal patterns within cortical layer IV. ON‐center axons had terminal arbors that ended mainly in the upper part of layer IV (IVa), while OFF‐center axons ended in the lower part of layer IV (IVb). Within layers IVa and IVb, axons driven by the ipsilateral eye and those driven by the contralateral eye had overlapping distributions. However, their terminal arbors differed in size, in shape, and in the number of boutons. Compared with contralateral eye arbors, ipsilateral eye axons were on average three times larger in lateral extent (925 μm vs. 325 μm), spread over four times the surface area (0.13 mm2vs. 0.03 mm2), and supported one and one‐half times as many terminal boutons (1,647 vs. 1,086). The ipsilateral eye axons had more boutons at the edges of layer IV (i.e., the upper part of layer IVa and the lower part of layer IVb), while those from the contralateral eye axons were more evenly distributed. These results show that each functional class of geniculocortical fiber has a different laminar and areal arrangement of boutons and we consider the significance of these differences for visual cortic

ISSN:0092-7317    

DOI:10.1002/cne.903020307

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractHippocampal area CA1provides the major cortical output of the hippocampus, but only its projections to the subiculum and lateral septal nucleus are well characterized. The present study reexamines these extrinsic projections by using anterograde and retrograde tracing techniques. Injections of the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA‐L) in theseptalone‐third of CA1label axons and terminals in subicular, postsubicular, retrosplenial, perirhinal, and entorhinal cortices, lateral septal nucleus, and diagonal band of Broca. The septal CA1, injections also label terminal fields in contralateral CA1, and in contralateral subicular, postsubicular, perirhinal, and entorhinal cortices. Injections into thesplenialone‐third of CA1label axons and terminals in subiculum, postsubiculum, ventral area infraradiata, and lateral septal nucleus, but they do not label axons and terminals on the contralateral side of the brain. Injections in thetemporalone‐third of CA1label axons and terminals in subicular, parasubicular, entorhinal, and infraradiata cortices, anterior olfactory nucleus, olfactory bulb, lateral septal nucleus, nucleus accumbens, amygdala, and hypothalamus. The temporal CA1injections label no axons on the contralateral side of the brain. These data demonstrate that CA1has more widespread projections than previously appreciated, and they provide the first clear evidence that CA1projects to the contralateral cortex and to the ipsilateral olfactory bulb, amygdala, and hypothalamus. The results also demonstrate a heterogeneity in the efferent projections originating in different septotemporal levels

ISSN:0092-7317    

DOI:10.1002/cne.903020308

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe organization of the visual system of larval lampreys was studied by anterograde and retrograde transport of HRP injected into the eye. The retinofugal system has two different patterns of organization during the larval period. In small larvae (less than 60–70 mm in length) only a single contralateral tract, the axial optic tract, is differentiated. This tract projects to regions in the diencephalon, pretectum, and mesencephalic tegmentum. In larvae longer than 70–80 mm, there is an additional contralateral tract, the lateral optic tract, which extends to the whole tectal surface. In addition, ipsilateral retinal fibers are found in both small and large larvae. Initially, the ipsilateral projection is restricted to the thalamus‐pretectum, but it reaches the optic tectum in late larvae. Changes in the organization of the optic tracts coincide with the formation of the late‐developing retina and consequently, the origin of the optic tracts can be related to specific retinal regions.The retinopetal system is well developed in all larvae. Most retinopetal neurons are labeled contralaterally and are located in the M2‐M5 nucleus of the mesencephalic tegmentum, in the caudolateral mesencephalic reticular area and adjacent ventrolateral portions of the optic tectum. Dendrites of these cells are apparent, especially those directed dorsally, which in large larvae extend to the optic tectum overlapping with the retino‐tectal projection.These results indicate that in lampreys, visual projections organize mainly during the blind larval period before the metamorphosis, their development being largely independent of visu

ISSN:0092-7317    

DOI:10.1002/cne.903020309

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThree highly specific opioid ligands—[D‐Ala2, Gly‐ol.]‐enkephalin (DAGO) for mu (m̈) receptor sites, [D‐Pen2, D‐Pen5]‐enkephalin (DPDPE) for delta (δ) sites, and U‐69593 for kappa (κ) sites—were used to determine the regional distribution of the three major subtypes of opioid receptor binding sites in the brains of 1‐day‐old domestic chicks by the technique of quantitative receptor autoradiography. Whilst there was a degree of heterogeneity in the binding levels of each of the ligands, some notable similarities existed in the binding of the μ and κp ligands in several forebrain regions, and in the optic tectum of the midbrain where μ and δ binding was very high. In the forebrain there was a high level of binding of μ and κ ligands in the hyperstriatum, and for the μ ligand there was a very distinct lamination of binding sites in hyperstriatum accessorium, intercalatum supremum, dorsale and ventrale. Levels of binding of the μ and κ ligands were also high in nucleus basalis, and (for μ only) in the neostriatum. The distribution of binding of the δ specific ligand in the forebrain showed marked differences to that of μ and κ, being particularly low in the hyperstriatum and neostriatum. Very high levels of labelling of δ binding sites were, however, found in the nucleus rotundus. Binding of the three ligands was generally low or absent in the cerebellum and medulla, apart from a distinct labelling of the granule cell layer by the μ‐ligand. A kinetic analysis was made of the binding of the three ligands to whole forebrain sections using scintillation counting methods. The μ‐ligand DAGO had the highest affinity,KD(1.0 n mol L−1), followed by the κ ligand U69593 (4.6 n mol L−1), and then the δ ligand DPDPE (6.0 n mol L−1). TheBmaxvaried from 14.6 f mol/mg tissue for the μ ligand to 6.3 fmol/mg tissue (δ), and 4.3 fmol/mg tissue (κ). However, an analysis of the kinetics of binding of the μ, δ, and κ ligands to individual forebrain regions by quantitative receptor autoradiography revealed a considerable variation in the affinity for binding sites and in maximal binding levels. A previous study was made of the distribution of the three opioid binding sites in adult pigeon brain by Reiner et al. (Journal of Comparative Neurology280:359–382, 1989). The present data show some similarities to the earlier study, but there are also marked dissimilarities which may be due either to species specific, or age related, differences. In the domestic chick the greatest densities of opiate receptor binding sites appear to coincide with regions in

ISSN:0092-7317    

DOI:10.1002/cne.903020310

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe innervation of the rat thymus was studied by light and electron microscopy in juvenile and aged rats. By light microscopy numerous fine nerves were found in the connective tissue septa penetrating between the thymic lobules. These septa were clearly delineated in the juvenile animals, but indistinct in the aged rats, thus creating the spurious impression that thymic parenchyma contains nerves. In the aged animals the nerves are thicker, tortuous, and more branched than in juvenile animals.Electron microscopy confirms the light microscopic observations: no nerves were found within the thymic parenchyma. The thymic capsule and larger connective tissue septa contain bundles of myelinated and unmyelinated axons, surrounded by a perineural sheath. Within the extraparenchymal compartment, which is greatly enlarged in aged animals, efferent and sensory nerves, devoid of perineurium, were found to contact mainly reticular cells, and in rare instances plasma cells and lymphocytes. The majority of axonal varicosities are not closely related to cellular elements, and, in general, vesicles are relatively infrequent. The possible functional significance of these observations is discussed.

ISSN:0092-7317    

DOI:10.1002/cne.903020311

出版商:Wiley‐Liss, Inc.    

年代:1990

数据来源: WILEY