摘要:

AbstractCollateral axonal branching from the medial or lateral mammillary nuclei to the anterior thalamus, Gudden's tegmental nuclei, the nucleus reticularis tegmenti pontis, and the medial pontine nucleus was studied using the fluores‐ cent retrograde double‐labeling method. One day after injection of Fast Blue into the anterior thalamic nuclei or Gudden's tegmental nuclei, Nuclear Yel‐ low was injected into Gudden's tegmental nuclei or the nucleus reticularis teg‐ menti pontis and the medial pontine nucleus. Following 1day survival, single‐ and double‐labeled neurons were examined in the mammillary nuclei.The lateral mammillary nucleus contains neurons whose collateral fibers project to both the dorsal tegmental nucleus of Gudden and the ipsilateral or contralateral anterodorsal thalamic nucleus, to both the medial pontine nucleus and the anterodorsal thalamic nucleus, and to both the dorsal tegmen‐ tal nucleus of Gudden and the medial pontine nucleus. The pars medianus and pars medialis of the medial mammillary nucleus contain neurons whose collat‐ eral fibers project to both the anteromedial thalamic nucleus and the ventral tegmental nucleus of Gudden, to both the anteromedial thalamic nucleus and the medial part of the nucleus reticularis tegmenti pontis, and to both the ven‐ tral tegmental nucleus of Gudden and the medial part of the nucleus reticu‐ laris tegmenti pontis. The dorsal half of the pars posterior of the medial mam‐ millary nucleus contains a few neurons whose collateral fibers project to both the anteromedial thalamic nucleus and the rostral part of the ventral tegmen‐ tal nucleus of Gudden, and to both the caudal part of the anteroventral thal‐ amic nucleus and the rostral part of the ventral tegmental nucleus of Gudden, while the pars lateralis of the medial mammillary nucleus contains no double‐ labeled neurons and projects only to the ant

ISSN:0092-7317    

DOI:10.1002/cne.902840102

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe rostral medial accessory olive (MAO) of the cat was studied by using an ultrastructural technique combining wheat germ agglutinin–coupled horseradish peroxidase (WGA‐HRP) anterograde tracing and postembedding GABA immunocytochemistry. One group of cats received a WGA‐HRP injection in the posterior interposed nucleus of the cerebellum and another group received an injection in the nucleus of Darkschewitsch.Based on differences in their morphology three types of GABAergic and three types of nonGABAergic terminals were observed. One type of GABAergic terminal was often GABA/WGA‐HRP double‐labeled in the cerebellar experiments, and one type of nonGABAergic terminal was often WGA‐HRP‐labeled in the mesodiencephalic experiments.Following injections of WGA‐HRP in the cerebellar nuclei virtually all WGA‐HRP‐labeled terminals were GABA positive. Quantification of these GABA/WGA‐HRP‐double‐labeled terminals showed that (1) 30% of the GABAergic terminals randomly selected from the entire neuropil were double‐labeled, (2) 13% of the GABAergic terminals adjacent to perikarya were double‐labeled, and (3) 34% of the GABAergic terminals strategically located next to both of the dendritic elements linked by a gap junction were doublelabeled. Statistical analysis of the above data showed that significantly fewer GABAergic terminals adjacent to perikarya were double‐labeled (P<.001) than would be expected from the double‐labeled proportion of the randomly selected GABAergic terminals.Following injection of WGA‐HRP in the nucleus of Darkschewitsch, all WGA‐HRP‐labeled terminals were GABA‐negative. Quantification of these terminals showed that (1) 26% of the randomly selected nonGABAergic terminals were WGA‐HRP labeled, (2) 20% of the nonGABAergic terminals adjacent to perikarya were WGA‐HRP labeled, and (3) 23% of the nonGABAergic terminals strategically located next to a gap junction were WGA‐HRP labeled. No significant differences were found among these populations.Quantification of terminals of both groups of experiments mentioned above showed that GABAergic terminals composed (1) 38% of the randomly selected terminals, (2) 64% of the terminals apposed to perikarya, and (3) 53% of the terminals strategically located next to gap junctions. Statistical analysis of the above data showed that significantly more GABAergic terminals were located adjacent to perikarya (P<.001) and strategically next to a gap junction (P<.05) than would be expected from the random GABAergic innervation.The above findings of the GABAergic, cerebellar, and mesodiencephalic input are discussed with regard to their functional role in the neuronal cir‐ cuitry of the rostral MAO. In addition, the possible noncerebellar origins of the GAB

ISSN:0092-7317    

DOI:10.1002/cne.902840103

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe purpose of the present study was to quantify the extent to which several peptides and serotonin coexist with substance P or somatostatin in selected lumbar dorsal root ganglia of the cat. The technique for the simultaneous visualization of two antigens by immunofluorescence was used to investigate the coexistence of neuropeptides in the lumbar dorsal root ganglia of colchicine‐treated cats. Perikarya immunoreactive for calcitonin gene‐related peptide, galanin, leu‐enkephalin, somatostatin, and substance P were visualized in both the lumbar 5 and 6 dorsal root ganglia. In contrast, no immunoreactivity was observed for adipokinetic hormone, bombesin, dynorphin A, met‐enkephalin, oxytocin, tyrosine hydroxylase, thyrotropin‐releasing hormone, vasopressin, vasoactive intestinal peptide, or serotonin in either ganglion examined. Substance P coexisted with calcitonin‐gene‐related peptide, somatostatin, and leu‐enkephalin. Somatostatin was colocalized with calcitonin gene‐related peptide, leu‐enkephalin, and substance P but coexisted with galanin minimally. The cell area of immunoreactive perikarya was also examined. Data concerning the cross‐sectional area of immunoreactive cells indicated that somatostatin‐immunoreactive perikarya were generally the largest population observed (up to ∼6,000 μm2). Somatostatin and calcitonin gene‐related peptide, as well as substance P and calcitonin gene‐related peptide, coexisted in populations of cell bodies that had a smaller size (less than 2,000 μm2). These results suggest that certain peptides which coexist in the dorsal root ganglia may provide histochemical markers for functional gro

ISSN:0092-7317    

DOI:10.1002/cne.902840104

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

年代:1989

数据来源: WILEY

摘要:

AbstractCollateralization of olivocerebellar (climbing) fibers was studied in the rat by means of the fluorochrome double‐labeling technique. Most of the olivocerebellar projection is crossed except for a minimal ipsilateral component which arises from the most rostral part of the inferior olivary nucleus (ION). ION neurons in the caudolateral part of the medial accessory olive (MAO) and the dorsal accessory olive (DAO) give off axons that branch to supply both hindlimb areas of the contralateral cerebellar cortex, i.e., the rostral anterior lobe and the caudal paramedian lobule. In addition, neurons in the middle one‐third of the contralateral MAO and DAO send axons that divide to terminate in both the caudal part of the anterior lobe and the rostral part of the paramedian lobule (forelimb receiving areas). Neurons within the caudal part of the MAO, the lateral part of the DAO, the ventral lamella of the principal olive (PO), and the dorsomedial cell column (DMCC) send axonal branches that terminate within at least two different areas of the same sagittal zones throughout the contralateral cerebellar cortex. Thus, the ION contains specialized cells that provide a divergence of integrated information from the ION to at least two cerebellar regi

ISSN:0092-7317    

DOI:10.1002/cne.902840105

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe representation in the inferior colliculus of the frequency modulated (FM) components of the first (25–30 kHz) and second (50–60 kHz) harmonic of the sonar signal of the mustached bat, which may be important for target range processing, was investigated by using the 2‐deoxyglucose (2‐DG) technique and single‐unit mapping.In the 2‐DG experiments, bats presented with second harmonic FM stimuli alone showed uptake of label in specific regions of the central nucleus and dorsal cortex of the inferior colliculus, and the nucleus of the brachium. In the central nucleus, a dorsoventrally and mediolaterally elongated slab at the caudal border of the anterolateral division was observed. Labeling in the dorsal cortex was contiguous with this band. Bats stimulated with pairs of first and second harmonic FM stimuli separated by short time delays showed similar patterns of labeling, with the addition of another dorsoventrally elongated region of uptake in the more rostral part of the anterolateral division, associated with label in the dorsal cortex. By comparison to control cases exposed to delayed pairs of first and third harmonic signals, or to a second harmonic constant‐frequency tone burst at the bat's reference frequency (ca. 60 kHz), we deduced that this additional region of uptake was attributable to the first harmonic FM component.To elucidate further the details of the tonotopic organization and to correlate the frequency representation with anatomical features of the IC, finegrained maps of single‐unit best frequencies were obtained in the central nucleus. Isofrequency contours were reconstructed by computer from five bats after focal, iontophoretic injection of horseradish peroxidase to locate the penetrations and trace connections of the FM2area.We found that the tissue volume representing FM2frequencies (50‐60 kHz) showed approximately a sixfold overrepresentation for this frequency band. This region occupied most of the caudal portion of the anterolateral division of the central nucleus. Only a single tonotopic representation was found in the central nucleus, consistent with the pattern seen in other mammals. However, isofrequency contours in the anterolateral division were oriented dorsoventrally, approximately parallel to the coronal plane. The small band of frequencies (ca. 60–62 kHz) associated with the dominant con‐ stant‐frequency component of the biosonar signal was even more dramatically overrepresented (40×) and was confined to the dorsoposterior division, as pre‐ viously reported by Zook et al. (1985, 530–456). The first‐harmonic FM fre‐ quencies (25–30 kHz) were localized rostrolaterally in the anterolateral division, confirming our 2‐deoxyglucose experiments. Frequencies above 65 kHz were found only in the medial division, where the isofrequency contours were also vertically oriented. The disproportionate representation of the FM2 band correlates well with its importance both as a cue for target ranging and as a critical acoustic element for the excitation of delay‐dependent “FM‐FM” facilitation neurons found at the thalamic and cortical

ISSN:0092-7317    

DOI:10.1002/cne.902840106

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

年代:1989

数据来源: WILEY

摘要:

AbstractEcholocating bats estimate target distance by analyzing the time delay between frequency‐modulated portions of their emitted ultrasonic vocalizations and the resultant echoes. In the companion paper we investigated, in the central nucleus of the inferior colliculus, the representation of the predominant second‐harmonic frequency‐modulated component (FM2) of the mustached bat biosonar signal (O'Neill et al.:J. Comp. Neurol. 283:000–000, '89). In the present paper we report the connections of this part of the colliculus, as determined by focal, iontophoretic injections of HRP following single‐unit mapping of the FM2representation. It was found that the major inputs to the FM2region of the inferior colliculus come from the contralateral cochlear nucleus; ipsilaterally from the medial superior olive, periolivary nuclei, and ventral and intermediate nuclei of the lateral lemniscus; and bilaterally from the lateral superior olive and dorsal nucleus of the lateral lemniscus. This study identifies for the first time those specific regions of brainstem nuclei providing input to the central nucleus of the inferior colliculus that process FM2information in the mustached bat. The primary outputs of the FM2region project to the medial and dorsal divisions of the medial geniculate body. In sharp contrast to other mammals, we found little evidence of connections to the ventral division of the medial geniculate. Other regions receiving significant inputs from the FM2area include the deep superior colliculus ipsilaterally and the ipsilateral lateral pontine nuclei. Some fibers also terminated near the midline in the dorsal midbrain periaqueductal gray. Sparse intrinsic connections were also seen to the ipsilateral dorsoposterior division of the central nucleus and to the contralateral inferior colliculus at a location homologous to the injection site in the anterolateral division. The finding that FM2projections to the medial geniculate heavily favor the medial and dorsal divisions is consistent with the location of “FM‐FM” delay‐dependent facilitation neurons found by Olsen (Processing of Biosonar Information by the Medial Geniculate Body of the Mustached Bat, Pteronotus parnellii.Dissertation, Washington Univ., St. Louis, '86) in these divisions, and with thalamocortical projection patterns in this species. These findings demonstrate that for the FM portions of the biosonar signal, a transformation from a tonotopic form of processing to a more specialized, convergent pattern of organization occurs at the level of the inferior c

ISSN:0092-7317    

DOI:10.1002/cne.902840107

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

年代:1989

数据来源: WILEY

摘要:

AbstractCentral and peripheral nonmedullated processes of vagal nodosal neurons of the cat were studied in normal nerves and after regeneration along their anatomical course and along the hypoglossal nerve. Nonmedullated fibers above the ganglion and in the root had comparable sizes (approximately 0.37 μm2) and caliber distribution. Below the ganglion, the cross‐sectional area increased to 1.0 μm2. In axons of equal caliber, supranodosal and radicular fibers had similar microtubular densities while infranodosal fibers had two‐ to threefold that of the former. Regenerated fibers were studied after a recovery period of 6–9 months. Regrown axons were smaller than their parent axons; in turn, these were smaller than normal axons. This holds for central and peripheral nodosal branches, for homologous and heterologous regeneration. Regrown peripheral branches, either along their anatomical pathway or along the hypoglossal nerve, showed no change in microtubular density. Central branches exhibited their characteristic microtubular content when they regenerated along their anatomical course, but when regrowth took place along the hypoglossal nerve, the original low microtubular content of these branches increased to match the high content of peripheral fibers; parent central axons also shifted their microtubular content toward the pattern of peripheral fibers. We propose that the supporting tissue participates in specifying the organization of axonal micro

ISSN:0092-7317    

DOI:10.1002/cne.902840108

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

年代:1989

数据来源: WILEY

摘要:

AbstractRetinal ganglion cells in fish and amphibians regenerate their axons after transection of the optic nerve. Fiber tracing studies during the third month of regeneration show that the axons have reestablished a basically normal fiber order in the two brachia of the optic tract; axons originating in the ventral hemiretina are concentrated in the dorsal brachium, axons from the dorsal hemiretina in the ventral brachium. Attardi and Sperry (Exp. Neurol.7:46–64, 1963) first suggested that the reestablishment of the fiber order reflects path‐finding by the regenerating axons. Recently, however, Becker and Cook (Development101:323–337, 1987) have claimed that the fiber order observed at later stages of regeneration is due to secondary axonal rearrangements and that the initial brachial choice is random.In order to evaluate whether regenerating axons are capable of navigating in the optic tract and brachia and on the tectum, the present study examined the pathway choices and the morphology of regenerating axons en route to their tectal targets in goldfish. Subsets of axons were labeled at various time intervals (2 to 30 days) following an optic nerve crush, by intraretinal application of the lipophilic fluorescent tracer 1,1‐dioctadecyl‐3‐3‐3′‐3′‐tetra‐methylcarbocyanine (DiI). After a survival time of 18 to 72 hours (to allow for diffusion of DiI along the axons), the experimental animals were perfused with fixative and their right and left optic pathways (nerve, tract, and tectum) were dissected free and separated at the chiasm. Fluorescently labeled axons were traced in whole‐mounted pathways. Pathway choices were examined at the brachial bifurcation where axons from ventral and dorsal hemiretinae normally segregate.DiI was found to label axons reliably up to their growth cones, even at the earliest stages of regrowth. The pathway choices of the axons were nonrandom. The majority of the ventral axons reached the appropriate, dorsal hemitectum through the appropriate dorsal brachium of the tract. Dorsal axons reached the ventral hemitectum mainly through the ventral brachium. This suggests the presence of specific guidance cues, accessible to the regenerating axons. Differences in the complexity of the growth cones of the regenerating axons (simple in the nerve and tectal fiber layer, complex in the tract and the synaptic layer of the tectum) provide further evidence for specific interactions between the regenerating axons and their substrates along the pathway. These result argue that regenerating retinal axons in fish are capab

ISSN:0092-7317    

DOI:10.1002/cne.902840109

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe location and chemical identity of neurons interconnecting the lateral geniculate complex and the hypothalamus were analyzed in order to provide further information on the anatomical substrates for the entrainment of circadian rhythms. A particular objective of the study was to characterize the neurons projecting between the intergeniculate leaflet (IGL) of the lateral geniculate complex and the suprachiasmatic nucleus (SCN) and related anterior hypothalamic areas. The connectivity experiments employed five combinations of fluorescent tracer injection and were combined with immunohistochemical localization of either neuropeptide Y (NPY), met‐enkephalin (mENK) or the vasoactive intestinal polypeptide (VIP)/peptide histidine isoleucine (PHI) group.IGL efferents.Injection of tracer into the SCN results in retrograde labeling of NPY‐immunoreactive neurons in the IGL as would be expected from prior work. These neurons and their terminals also contain the C‐flanking peptide of the NPY precursor molecule (CPON). In addition, there are two additional groups of neurons in the IGL that project either to the SCN or the contralateral IGL but do not exhibit NPY immunoreactivity. These include a substantial population of cells that project to the SCN and an even larger group of neurons which project to the contralateral IGL and contain mENK immunoreactivity.Hypothalamic efferents.Injection of tracer into the IGL results in retrograde labeling of scattered neurons throughout the SCN and immediately adjacent anterior hypothalamus ipsilaterally and also in labeling of a small number of neurons in the same areas on the contralateral side of the brain. In rare instances, individual SCN neurons appear to project to both IGLs. However, the retrochiasmatic area (RCA) contains the largest number of retrogradely labeled neurons following tracer injections into the IGL. These neurons are concentrated along the midsagittal plane and in the lateral RCA ipsilateral to the injected IGL. None of the labeled neurons in the SCN or adjacent anterior hypothalamus exhibit VIP or PHI immunoreactivity.These observations indicate that the anatomical relations between the geniculate complex and the anterior hypothalamus are more complex than previously shown. First, the geniculohypothalamic tract arises from two distinct groups of IGL neurons: one contains NPY/CPON immunoreactivity; the chemical content of the other is not characterized at the present time. Second, the commissural projection between the two IGLs is formed by a third group of neurons, and these cells contain mENK immunoreactivity. Finally, reciprocal projections from the hypothalamus to the IGL arise from neurons in the retrochiasmatic area, SCN, and adjacent anterior hypothalamus. These anatomical observations demonstrate that the neuronal circuitry involved in the entrainment of circadian rhythms consists of a complex series of projections that interconnect the SCN, anterior hypothalamus, an

ISSN:0092-7317    

DOI:10.1002/cne.902840110

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

年代:1989

数据来源: WILEY

摘要:

AbstractTo define the extent to which impulse blockade interferes with the morphological changes of regenerating retinal axons during their growth through the tectum, axons were deprived of activity by repeated intraocular injections of TTX. At intervals between 24 and 189 days after optic nerve section (ONS), a defined group of TTX‐silenced axons and of axons with normal activity (controls) were labeled by applications of HRP to the ventro‐ or dorsotemporal retina. The trajectories of these labeled axons were traced in DAB processed tectal wholemounts.As in controls, TTX‐blocked axons went through a phase of exploratory growth at early regeneration stages (24 to 80 days after ONS). Coursing in abnormal routes, the axons initially distributed their growing endings widely over the tectum. Axons with and without activity extended side branches with growth cones and filopodia over all regions of the tectum. These ramifications were of similar dimensions for the TTX‐blocked and control axons. Despite abnormal routes and branching over inappropriate territories, axons showed a preference for the rostral tectum. At late regeneration stages (120–189 days after ONS), axons had lost their side branches and their growth cones. Their preterminal segments exhibited striking bends, suggesting that they had undergone course corrections to achieve access to the retinotopic target. Axonal processes had disappeared from the caudal tectum, and the preferential accumulation of axons over the rostral tectum had increased. The majority of the TTX‐blocked and control axons ended in terminal arbors at retinotopic regions. The labeled arbors of the TTX‐group were no larger than those of the control group. The arbors of each group lay close together in a continuous cluster in the TTX‐group as well as in two‐thirds of the control group. In the other one‐third of the control group, however, terminal arbors were aggregated into separate patches. The clusters of the TTX‐blocked axons covered between 2.2 and 3.9% (mean 2.95%) of the tectal surface and the clusters and/or patches of active axons between 1.9 and 3.4% (mean 2.7%). Thus the terminal arbor clusters of the TTX‐silenced axons were not significantly larger than those of the active axons.These data show that retinal ganglion cell impulse activity is required for neither the extension of side branches in the early exploratory phase of regeneration nor for the withdrawal of these branches nor for the establishment of target‐directed routes and the deployment of normal‐size terminal arbors at retinotopic loci. Our data further suggest that the retinotopic map is refined considerably with time even in the absence of activity, a finding that is consistent with an abstrac

ISSN:0092-7317    

DOI:10.1002/cne.902840111

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

年代:1989

数据来源: WILEY