摘要:

AbstractThe distribution and morphology of serotoninergic neurons in the marmoset (New‐World monkey) brainstem were studied by immunocytochemistry and computer‐assisted threevdimensional reconstruction. The cytoarchitectonic localization of serotoninergic neurons was ascertained in series of adjacent immunostained and Nissl‐stained sections, and the extent and shape of the serotoninergic nuclei were visualized by computer reconstruction. The overall distribution of the immunoreactive neurons is comparable to that already described for several species of primates. The serotoninergic nuclei are spatially well segregated into an anterior and a posterior group. The anterior group, in the mesencephalon and the rostral pons, contains the largest population of serotoninergic neurons. These neurons are not confined to the raphe nuclei near the midline, but rather expand laterally in the reticular formation. This expanded distribution of the neurons in the anterior group results in a partial fusion of the nuclei. In some nuclei, particularly the median raphe, subdivisions can be clearly delineated on the basis of the distinct morphology of the neurons and of their clustering. The neurons of the posterior group, in the caudal pons and the medulla, are almost all contained within the limits of the raphe nuclei. The serotoninergic neurons located in the reticular formation form a lateral column, which is clearly separated from the serotoninergic neurons found near the midline.Immunoreactive axons are distributed throughout the brainstem, but they innervate certain motor and sensory nuclei more densely. It was consistently found in newborn animals that the overall immunoreactive axonal network was richer than in juveniles or adults, suggesting that there may be a major modification in the function of the serotoninergic system around

ISSN:0092-7317    

DOI:10.1002/cne.902700402

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractThe inferior colliculus of the mustache bat is similar in most respects to the inferior colliculus of more commonly studied mammals, but one isofrequency contour, the dorsoposterior division, is greatly overrepresented. The present study utilizes this specialization of the auditory system in the mustache bat to determine the total set of ascending projections to a single isofrequency contour of the inferior colliculus. Within the dorsoposterior division, neurons are all very narrowly tuned to 60 kHz, the major component of this bat's echolocation call. The afferent projections to this isofrequency contour were identified by making deposits of horseradish peroxidase (HRP) within the dorsoposterior division after physiologically defining its borders. Two other frequency representations are present in the central nucleus of the inferior colliculus of the mustache bat, the anterolateral division in which there is an orderly progression of frequencies from 59 down to 20 kHz, and the medial division in which frequencies from 63–120 kHz are represented. In additional experiments, the afferent projections to the medial and anterolateral divisions were examined, providing an anatomical description of the tonotopicity of the lower auditory nuclei.Deposits of HRP in the DPD labeled cells in each of the lower brainstem auditory nuclei that have previously been shown to project to the entire central nucleus of the inferior colliculus. The ascending projections to the dorsoposterior division include contralateral projections from the cochlear nucleus and inferior colliculus, ipsilateral projections from the medial superior olive, ventral and intermediate nuclei of the lateral lemniscus, and bilateral projections from the lateral superior olive and dorsal nucleus of the lateral lemniscus. In most of the nuclei, labeled cells were confined to specific portions of the nuclei, often forming “slabs” of labeled cells across the rostrocaudal extent of most nuclei. These slabs presumably represent the 60 kHz representation in each of the lower nuclei. When deposits of HRP were made into other frequency band representations of the inferior colliculus, in either the medial or anterolateral division, labeled cells again formed slabs in each lower nucleus. However, the location of the slab varied as a function of the best frequency of neurons at the deposit site, and labeled cells were not present within the 60 kHz representation. These results show the general tonotopy of the mustache bat's brainstem auditory nuclei, and with respect to the dorsoposterior division, clearly reveal the total set of projections to a single isofrequency region. In addition, results are presented that suggest that some nuclei project to restricted areas of the dorsoposterior div

ISSN:0092-7317    

DOI:10.1002/cne.902700403

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractProjections from the rat lateral entorhinal cortex (area 28‐l) to the dentate gyrus were traced and then interpreted according to a parcellation scheme that recognized four cytoarchitectonic subdivisions of area 28‐1: areas dorsolateral (dl), ventrolateral (vl), ventromedial (vm), and TR. Following lesions of area 28‐l, anterograde degeneration was traced with the Fink‐Heimer method. In parallel experiments iontophoretic injections of horseradish peroxidase (HRP) were made in the lateral perforant path terminal zone of the dentate molecular layer. Retrograde neuronal labeling patterns within area 28‐l were charted following dorsal, midseptotemporal (mid ST), and ventral dentate injections. In two additional cases HRP was deposited in the ventral subiculum.Lesions of area dl (which lies entirely on the posterolateral cortex) produced terminal degeneration that was confined to the dorsal one‐half of the dentate gyrus. Lesions involving primarily areas vl and vm (which lie on the posteroinferior cortex) caused a complementary pattern of degeneration; silver grains predominated in the ventral dentate gyrus.Injections of HRP into the outer dentate molecular layer labeled layer II neurons within area 28‐l. Deposits of HRP in the dorsal one‐third of the dentate gyrus labeled a rostrocaudal strip of neurons within the dorsal one‐third of area dl; no other subdivisions of area 28vl contained labeling. After mid‐ST deposits of HRP, a rostrocaudally oriented strip of labeled cells appeared in the ventral one‐third of area dl. Mid‐ST injections also labeled neurons in the caudolateral quadrant of area vl. Injection of HRP into the ventral dentate gyrus labeled neurons in the caudomedial quadrant of area vl as well as a few neurons in caudal area vm. No labeled cells were ever found in area dl following ventral dentate HRP deposits. Neurons within area TR were never retrogradely labeled from injections of HRP into the dentate perforant path zone. However, ventral subicular injections of HRP labeled a few cells in the posterior part of area TR, as well as hundreds of neurons throughout the rostrocaudal extent of area vl.The results indicate a highly organized innervation of the dentate gyrus by several subdivisions of area 28‐l. In area dl, rostrocaudal strips of layer II neurons innervate distinct segments of the dorsal ST axis. The posterior half of areas vl and vm innervates the ventral half of the ST axis; a lateromedial gradient there corresponds to increasingly ventral terminations along the dentate ST axis. Finally, in contrast to the other lateral entorhinal subdivisions area TR does not appear to innervate the distal dendrites of dentate granule cells. The implications of this organization for the study of functional diversity along t

ISSN:0092-7317    

DOI:10.1002/cne.902700404

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractAs part of a study on the organization of the brainstem in a primitive group of vertebrates, the efferent cells and primary afferent fibers of the urodele amphibianPleurodeles waltliiwere examined by means of retrograde and anterograde axonal transport and anterograde degeneration. The trigeminal motor nucleus is located in the periventricular gray just medial to the sulcus limitans. Its rostral part is a band of pear‐shaped cells lying parallel to the wall of the ventricle, whereas its caudal part is a round mass consisting of polygonal cells. In addition, a small group of scattered neurons is situated ventral to the rostral part of the nucleus. The primary afferent fibers enter the brainstem in the dorsal two‐thirds of the trigeminal root. They diverge into a short ascending and a long descending tract. The former distributes its axons to the principal sensory trigeminal nucleus, which is an ill‐defined cell group located at the ventrolateral edge of the periventricular gray. In the descending tract, the fibers of the ophthalmic nerve are predominantly located ventromedially, and those of the maxillomandibular nerve dorsolaterally. A fascicle of the ophthalmic nerve leaves the descending tract and, apparently, makes contact with the accessory abducens nucleus. The descending tract extends caudally into the three upper cervical segments of the spinal cord. The mesencephalic trigeminal nucleus consists of conspicuous large cells, which are scattered through the tectum of the mesencephalon. The cells with peripheral branches in the ophthalmic nerve are mainly located in the caudal half of the tectum, and those with peripheral branches in the maxillomandibular nerve in the rostral half Collaterals of the central branches of the mesencephalic trigeminal system were traced to an area of the periventricular gray situated between the motor nucleus and the principal sensory nucleus of the trige

ISSN:0092-7317    

DOI:10.1002/cne.902700405

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractA quantitative in situ hybridization analysis was used to investigate changes in levels of ribosomal RNA (rRNA) in neurons of the supraoptic nucleus (SON) of rats stimulated osmotically by giving 2% NaCl as drinking solution for 0 (control rats), 1, 4, and 14 days. The quantitation was autoradiographically accomplished by in situ hybridization with a nick‐translated tritiated ribosomal DNA probe and with the use of computer‐based image analysis system. The mean number of grains per neuron in the ventral SON was significantly increased: 1.8‐fold for 1 day, 2.9‐fold for 4 days, and 1.7‐fold for 14 days of salt loading, whereas the mean number of grains per neuron in the dorsal SON was increased 1, 3‐fold for 1 day, 2.5‐fold for 4 days, and 1.7‐fold for 14 days. Kolmogorov‐Smirnov analysis of frequency histograms of grains per neuron indicated that the amount of rRNA in neurons in the ventral and dorsal SON was significantly increased by osmotic stimulation. These increases were accompanied by increases in cell size. The subcellular location of hybridizable rRNA in magnocellular neurons was altered by osmotic stimulation. Following 1–14 days of salt‐drinking, rRNAs appeared to be more unevenly distributed throughout the cytoplasm. These findings are consistent with the notion that hyperosmotic stimulation has a substantial effect on the expression of rRNA genes in neurons of both the v

ISSN:0092-7317    

DOI:10.1002/cne.902700406

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractTransplants of the embryonic rat spinal cord survive and differentiate in the spinal cords of adult and newborn host rats. Very little is known about the extent to which these homotopic transplants can provide an environment for regeneration of adult host axons that normally terminate in the spinal cord. We have used horseradish peroxidase injury filling and transganglionic transport methods to determine whether transected dorsal roots regenerate into fetal spinal cord tissue grafted into the spinal cords of adult rats. Additional transplants were examined for the presence of calcitonin gene‐related peptidelike immunoreactivity, which in the normal dorsal horn is derived exclusively from primary afferent axons. Host animals had one side of the L4‐5 spinal cord resected and replaced by a transplant of E14 or E15 spinal cord. Adjacent dorsal roots were sectioned and juxtaposed to the graft. The dorsal roots and their projections into the transplants were then labeled 2–9 months later. The tracing methods that used transport or diffusion of horseradish peroxidase demonstrated that severed host dorsal root axons had regenerated and grown into the transplants. In addition, some donor and host neurons had extended their axons into the periphery to at least the midthigh level as indicated by retrograde labeling following application of tracer to the sciatic nerve. Primary afferent axons immunoreactive for calcitonin gene‐related peptide were among those that regenerated into transplants, and the projections shown by this immunocytochemical method exceeded those demonstrated by the horseradish peroxidase tracing techniques. Growth of the host dorsal roots into transplants indicates that fetal spinal cord tissue permits regeneration of adult axotomized neurons that would otherwise be aborted at the dorsal root/spinal cord junction. This transplantation model should therefore prove useful in studying the enhancement and specificity of the regrowth of axons that normally terminate in the spin

ISSN:0092-7317    

DOI:10.1002/cne.902700407

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractA primate model has been used to explore the possibility that anterolateral chordotomy may produce intraspinal sprouting or rearrangement of primary afferent nerve terminations that could account for delayed postoperative recovery of sensory function. Monkeys were trained to limit the duration of an electrical stimulus, and the vigor and frequency of their escape responses were used to differentiate painful from nonpainful levels of stimulation. Behavioral testing after chordotomy revealed: (1) contralateral hypalgesia in all animals, with sensory recovery in half of the group, and (2) bilateral decreases in reflexive force in all animals, with reflex recovery in the majority of monkeys. At the terminal experiment, dorsal rootlets caudal to the spinal lesion were labeled bilaterally with HRP, and the distribution of labeled synaptic complexes was determined within the dorsal horn. When compared to controls, animals undergoing chordotomy showed a loss of terminals in the superficial dorsal horn and an increase of synaptic enlargements in deeper layers. These effects were bilateral, but were most pronounced on the side contralateral to chordotomy. Animals with diffuse spinal lesions showed a completely different change in the distribution of primary afferent terminals. Animals with sensory recovery demonstrated a more normal terminal distribution pattern than persistently hypalgesic monkeys, but there was considerable variability in the data, and analysis by different statistical tests yielded varying results.

ISSN:0092-7317    

DOI:10.1002/cne.902700408

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractA morphometric study of the glomerular population in the olfactory bulb of the mouse has been carried out by using stereological methods. On the basis of the assumption that the glomerular population is a polydispersed system of spheres, glomerular profile distributions obtained from profile measurements were subjected to a mathematical unfolding procedure to obtain the actual glomerular size distribution. We used a distribution‐free method to account for the combined effects of overprojection due to section thickness and truncation (two missing profile mechanisms). Results proved better than those obtained directly from profile measurements without stereological analysis. Several new findings were obtained. First, significant variations of the glomerulus sizes were found along the rostrocaudal axis. The glomeruli are larger in the middle region of the olfactory bulb, whereas their numerical density decreases in the same region. Moreover, the profile density is homogeneous along the rostrocaudal axis. In other words, the relative surface occupied by the periglomerular cells in the glomerular layer is invariant. As a consequence, it may be concluded that the variations in size and numerical density are inversely correlated. Thus, since the glomeruli are larger in the middle region, their number per unit volume is logically smaller in this same area. Finally, the computerization of all these data has led us to estimate the number of glomeruli (1,810 ± 41) in the olfactory bulb of the mouse. In order to get a comparative idea of their advantages and disadvantages, other standard stereological methods were used in the present study to determine this number. Functional interpretations of the variations of the size and numerical density along the rostrocaudal axis of the olfactory bulb are discussed with respect to ontogenetic and morphofunctional data obtained elsewhe

ISSN:0092-7317    

DOI:10.1002/cne.902700409

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractPeripheral transganglionic transport of horseradish peroxidase (HRP) was used to label afferent fibers in the taste buds and lingual epithelium 2–12 weeks after chronic chorda tympani or combined chorda tympani‐lingual nerve lotions, From 4–12 weeks after a chronic chorda tympani lesion, taste buds could be found. These were innervated by fibers from the ipsilateral lingual nerve. From 8–12 weeks after a. chronic chorda tympanivlingual nerve lesion, nerve fibers from the contralateral lingual nerve could be found in a few taste buds on the denervated side of the tongue. Thus, collateral sprouting took place over the midline in this instance. These findings indicate that intact gustatory axons do not sprout into denervated taste buds, but trigeminal fibers in the lingual nerve do have this

ISSN:0092-7317    

DOI:10.1002/cne.902700410

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractNormally, axons within the corpus callosum are ordered according to the cortical regions from which they originate, and callosal cells and terminations form elaborate cortical patterns related to the underlying topographic representations of the sensory periphery. About 30% of mice of the BALB/c strain show congenital deficiencies of the callosal commissure which range from total absence of the corpus callosum to a moderate reduction in the size of this commissure. In the light of current theories about the origin of these callosal deficiencies, it seems likely that fibers crossing the mid‐plane in mutant mice have to circumvent local disturbances along their migration path. Since these disturbances in fiber trajectory may, in turn, alter the overall pattern of callosal projections, we set out to investigate whether the distribution of callosal connections in mice with marked deficiencies of the corpus callosum is as ordered as in normal mice.In groups of normal and mutant mice, we used multiple injections of horseradish peroxidase to reveal the overall distribution of callosal connections and restricted injections of horseradish peroxidase conjugated with wheat germ agglutinin to reveal finer aspects of the organization of the callosal pathway in these animals. Our results show that the number of labeled cells is reduced in mice with a small corpus callosum and that no labeled cells are present in the neocortex of acallosal mice. Furthermore, the topographic distribution of fibers within the corpus callosum of mutant mice can be significantly less ordered than in normal mice. However, even in mice with extreme deficiencies of the corpus callosum, callosal fibers originate from and terminate in all major areas of the cortex, and, within these areas, callosal cells and terminations are distributed according to the normal plan. The laminar distribution of callosal cells also appears normal in these mice. These findings indicate that gross developmental anomalies of the corpus callosum do not prevent normal specification of the callosal pattern during development. Within the context of current theories about the origin of congenital callosal deficiencies, our findings suggest that callosal fibers are able to establish appropriate contralateral connections in spite of alterations of their migration route. They also suggest that fiber topography within the corpus callosum does not play an important role in guiding migrating axons to their correct contralateral targets. Finally, our failure to find labeled fibers within the anterior commissure indicates that this commissure does not serve as an alternative route for deviated callosal axon

ISSN:0092-7317    

DOI:10.1002/cne.902700411

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY