摘要:

AbstractLight and electron microscopic immunocytochemistry was used to study the fine structural organization of the catecholaminergic and hypothalamic peptidergic innervation of the dorsal vagal complex of the medulla oblongata in the rat and guinea pig, the latter of which is known to lack central adrenergic neurons. In the rat, adrenergic fibers immunoreactive to phenylethanolamine‐N‐methyltransferase were concentrated in the dorsal motor nucleus of the vagus, where they established frequent symmetric synapses with dendrites and perikarya. On the other hand, the density of both oxytocin‐ and corticotropin‐immunoreactive fibers appeared far lower in this nucleus than in the dorsal regions of the nucleus of the tractus solitarius, where they formed asymmetric synapses with small dendrites. In tissue treated for the dual labeling of two neuronal antigens, oxytocin‐ or corticotropin‐reactive fibers were in close contact with adrenergic neurons in this dorsal medullary region. In the guinea pig, unlike the rat, the dorsal motor nucleus of the vagus contained large amounts of oxytocin‐ and corticotropin‐reactive fibers, which formed many symmetric synapses with perikarya and dendrites. Taken together, these data suggest that the control of vagal preganglionic neurons by hypothalamic peptidergic neurons involves a bisynaptic neuronal pathway including adrenergic medullary neurons in the rat, whereas it is direct in the guinea pig, which lacks this a

ISSN:0092-7317    

DOI:10.1002/cne.902900302

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractWe hypothesized that the afferent fibers in the ventral root of the rat are the third branches of dorsal root ganglion cells; these afferent processes in the ventral root are of varying length and end bluntly along the length of the root. In the case of an injury at either the central or the peripheral processes of the dorsal root ganglion cells in the neonatal stage, these fibers sprout at the blunt endings along the length of the ventral root. We cut either the sciatic nerve or the dorsal root on one side in neonatal rats. After the rats were fully grown, the number of both myelinated and unmyelinated fibers was counted in electron photomicrographs at multiple sites along the length of the ventral root. We observed a greatly increased number of unmyelinated fibers in the ventral root after the sciatic nerve had been cut at the neonatal stage. The magnitude of increase was more at the distal than at the proximal portion of the ventral root, suggesting that added fibers originated from the distal side. Neonatal dorsal rhizotomy, however, did not produce the same result. These results are consistent with our hypothesis that peripheral nerve injury at the neonatal stage triggers sprouting of the third branches of the dorsal root ganglion cells which end bluntly along the length of the ventral root in the normal animal.

ISSN:0092-7317    

DOI:10.1002/cne.902900303

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe rostral anteroventral cochlear nucleus (AVCN) of the chinchilla provides a preparation in which neuronal cell bodies and synapses in the mammalian central nervous system can be examined after direct freezing and freeze‐substitution of rapidly excised brain stem slices. Cell bodies and synapses in the freeze‐substituted AVCN differed from those in perfusion‐fixed AVCN in several interesting respects. Despite of these differences, four types of synaptic terminal were distinguished in freeze‐substituted AVCN and correlated with the four well‐known types of perfusion‐fixed terminal. Since the transmitter at each of the four types of terminal has been tentatively identified, the structure of synaptic vesicles and junctions in the freeze‐substituted terminals could be related to transmitter type. Synaptic vesicles were uniformly round, but their diameters, deployment, and related cytoskeletal elements near the synaptic junction differed in each chemical type of synapse; the synapses thought to be cholinergic, for instance, had only a few vesicles clustered at their presynaptic junctions while the rest of the vesicles were separated from the junction by a network of fine filaments. Two types of filamentous components, short vertical projections from the postsynaptic membrane and thin filaments protruding from these projections, comprised the basic structure of the postsynaptic specialization, but their sizes and distribution differed at each chemical type of terminal. For instance, the postsynaptic specialization at the glycine terminal was distinguished by numerous thin filaments which curved sideways to run parallel to the plasmalemma. Thus, freeze‐substitution gives new information about structural differences between chemically different types of synapses, which may reflect differences in their transmitter storage, release, and reception. In addition, the AVCN preparation is of general interest in making cell bodies in the mammalian central nervous system available to the various structural and analytical techniques which depend on direct,

ISSN:0092-7317    

DOI:10.1002/cne.902900304

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe cellular location of Neuropeptide Y (NPY) synthesis in rat brain is identified by using in‐situ hybridisation histochemistry. The results show that NPY mRNA is widely distributed through the rat brain, although the levels of NPY mRNA are surprisingly low. There is a large degree of variation in the content of NPY mRNA in different regions. The highest cellular levels of NPY mRNA are found in the arcuate nucleus of the hypothalamus, in the cerebral cortex, and in the hilar region of the hippocampus. In general, the distribution of perikarya containing NPY mRNA corresponds to the reported distribution of perikarya containing NPY‐immunoreactivity. However, NPY mRNA was detected in the majority of the perikarya in the reticular nucleus of the thalamus, an area not previously known to contain NPY neurones. In many areas of the forebrain the distribution of NPY mRNA parallels that of somatostatin mRNA, supporting suggestions of their coexistence. The ability to detect NPY mRNA at the cellular level should be of considerable use in dynamic studies of the activity of NPY neuro

ISSN:0092-7317    

DOI:10.1002/cne.902900305

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractBinding of propylbenzilylcholine mustard, a muscarinic acetylcholine receptor antagonist, to isolated retinal cells was examined with light microscopic autoradiography. Dissociation of the adult tiger salamander retina yielded identifiable rod, cone, horizontal, bipolar, amacrine/ganglion, and Müller cells. Preservation of fine structure was assessed with conventional electron microscopy. For all cell types, the plasmalemma was intact and free of adhering debris; in addition, presynaptic ribbon complexes were present in photoreceptor and bipolar axon terminals indicating that synaptic structures were retained. Specific binding to cell bodies and processes was analyzed separately by using morphometric and statistical techniques. The highest grain densities occurred on processes of amacrine/ganglion cells and axons and 2° and 3° dendrites of bipolar neurons. Bipolar cells, however, seemed to be a heterogeneous population because there was great variation in the density of binding sites on both their axons and distal dendrites. Intermediate levels of binding were found on bipolar 1° dendrites and horizontal cells. No specific binding was detected on Müller cells and most parts of photoreceptors. Comparisons between cells showed that grain densities were similar for bipolar axons and amacrine/ganglion cell processes but bipolar dendrites were richer in binding sites than horizontal cell dendrites. Thus, muscarinic receptors in the salamander retina are located on amacrine/ganglion, bipolar, and horizontal cells and primarily confined to the processes which compose the two synaptic layers. In the inner plexiform layer, muscarinic receptors reside on processes from all three inner retinal neurons; in the outer synaptic layer, receptors are only on second‐order cells and are more numerous along bipolar than horizontal cell den

ISSN:0092-7317    

DOI:10.1002/cne.902900306

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe primary purpose of the present study is to obtain evidence as to the destination of the recently discovered unmyelinated primary afferent fibers in the mammalian dorsal funiculus. To do this rat dorsal roots were transected unilaterally from segments T8 or T9 caudally, and the numbers of axons were determined in the C3 fasciculus gracilis in normal animals and from both sides of the rhizotomied animals. In addition, C3 fasciculus gracilis counts were done in animals that had complete T6 or T10 spinal transections. The data indicate that there is an 80% loss of unmyelinated axons ipsilaterally and a 60% loss contralaterally in the fasciculus gracilis of the rhizotomied animals. These findings are interpreted as indicating that a significant fraction of the unmyelinated fibers in the fasciculus gracilis ascend, presumably to the nucleus gracilis in the brain stem, and also that a significant number of these fibers branch. We also provide evidence for contralateral myelinated primary afferent fiber projection in the fasciculus gracilis and show that the myelinated primary afferent fibers seem to be a more diverse population than the unmyelinated primary afferent fibers in the C3 fasciculus gracilis.

ISSN:0092-7317    

DOI:10.1002/cne.902900307

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractImmunocytochemical staining procedures with the HRP‐complexed antibody to substance P have been carried out on the turtle retina. Examination by light microscopy of wholemount retinas has allowed us to evaluate the morphology and distribution of the substance P immunoreactive cell types. Two amacrine cell types and two or more ganglion cell types are stained in our hands. Type A amacrines are tri‐stratified wide‐field amacrines. They have their major dendrites in S1 and S3 of the inner plexiform layer and they emit fine dendrites from the major dendrites that end in varicose boutons in S5 on and around cell bodies in the ganglion cell layer. Some of the dendrites in S1 radiate out in axon‐like fashion for 1 mm across the retina. The type B amacrine cells are small to medium‐field in dendritic extent. They have smaller cell bodies than type A and a single or, at most, two primary dendrites that pass directly to S3 before branching profusely into an intricate net‐like dendritic field. The ganglion cells that are stained with substance P antibodies appear to be of several types but their exact morphologies are in doubt because only portions of their major dendrites are stained. Substance P immunoreactive axons are clearly seen to project from the cell bodies to the optic nerve head and axons are stained in the optic nerve itself.The substance P‐stained ganglion cells occur in an irregular distribution that reaches a peak density in an elongated band parallel to and 1 mm below the visual streak. The type B amacrine cells reach a maximum density in the visual streak and are distributed in a highly regular mosaic decreasing in density in elliptical isodensity contours from the visual streak. In contrast the type A amacrine cells are rare or absent in the streak, being located in an irregular mosaic in peri

ISSN:0092-7317    

DOI:10.1002/cne.902900308

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractHorseradish peroxidase was used to identify motor neurons projecting to the adductor mandibulae, levator hyomandibulae, levator operculi, adductor operculi, and dilator operculi muscles in Siamese fighting fish,Betta splendens.These muscles participate in the production of respiratory and feeding movements in teleost fishes. The dilator operculi is also the effector muscle for gill‐cover erection behavior that is part ofBetta'saggressive display. The motor innervation of these muscles inBettawas compared to that previously described for carp.Motor neurons of the adductor mandibulae, levator hyomandibulae, and dilator operculi are located in the trigeminal motor nucleus, and motor neurons of the adductor operculi and levator operculi are located in the facial motor nucleus inBettaand in carp. The trigeminal motor nucleus in both species is divided into rostral and caudal subnuclei. However, there are substantial differences in the organization of the subnuclei, and in the distribution of motor neurons within them. InBetta, the rostral trigeminal subnucleus consists of a single part but the caudal subnucleus is divided into two parts. Motor neurons for the dilator operculi and levator hyomandibulae muscles are located in the lateral part of the caudal subnucleus; the medial part of the caudal subnucleus contains only dilator operculi motor neurons. The single caudal subnucleus in carp is located laterally, and contains motor neurons of both the dilator operculi and levator hyomandibulae muscles.Differences in the organization of the trigeminal motor nucleus may relate to the use of the dilator operculi muscle for aggressive display behavior by perciform fishes such asBettabut not by cypriniform fishes such as carp. Five species of perciform fishes that perform gill‐cover erection behavior had aBetta‐like pattern of organization of the caudal trigeminal nucleus and a similar distribution of dilator operculi motor neurons. Goldfish, which like carp are cypriniform fish and do not display, had a carp‐like trigeminal organization and dilator operculi motor neuron distr

ISSN:0092-7317    

DOI:10.1002/cne.902900309

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe central projections of physiologically characterized vestibular nerve fibers originating from the horizontal semicircular canal were studied in the vestibular nuclei of adult cats after intracellular staining with horseradish peroxidase (HRP). First, primary nerve fibers were physiologically classified as regular or irregular types on the basis of the regularity of the spontaneous discharge pattern. Then, these two types of fibers were morphologically analyzed and compared following HRP intraaxonal injection. The two types of axons showed a basically similar trajectory in the four major vestibular nuclei. They bifurcated into an ascending and a descending branch in the ventrolateral part of the lateral vestibular nucleus (LVN). The ascending branch extended rostrally and gave off one or two collaterals in the superior vestibular nucleus (SVN), although some of the ascending branches further ran rostrally into the cerebellum. The collaterals, while running medially, gave rise to fine terminal branches with en passant boutons in the SVN, and further coursing caudally, they entered the rostral part of the medial vestibular nucleus (MVN). The descending branch, while running caudally in the lateral part of the LVN and the inferior vestibular nucleus (IVN), gave off several thick collaterals to the MVN and extensive terminals were present in the IVN and MVN. In each primary axon, about one‐third of the total terminal boutons were distributed in each of the SVN, the MVN, and the IVN. In contrast to this similarity of the overall axonal trajectory within the vestibular nuclei, both types of axons exhibited several marked differences in diameter and in the mode of terminal arborization. In almost every part of the ramification, the irregular‐type fibers were thicker than the regular‐type fibers. In the regular‐type axons, many small terminal boutons (mean size, 2.4 × 1.4 μm, N = 2,739) were located in close proximity (100–150 μm) to the parent collateral. In the irregular‐type axons, slightly larger terminal boutons (mean size, 3.0 × 1.7 μm, N = 1,287), were spread more widely (200–300 μm) around their collaterals. These clear morphological differences between the regular‐type and the irregular‐type terminal axons were consistently observed in

ISSN:0092-7317    

DOI:10.1002/cne.902900310

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractNuclear pores were assessed on freeze‐fracture replicas from different neuronal and glial cell types of the rat cerebellar cortex. Nuclear diameter and perimeter were measured on semithin sections, and nuclear surface area and volume were calculated from these data. The proportion of inner nuclear membrane in apposition to condensed chromatin was measured on thin sections. The values of nuclear pore numerical density (number/μm2) were as follows (mean ± S.D.): Purkinje cells, 22 ± 3; Golgi cells 17 ± 3; granule cells, 6 ± 4; stellate and basket cells, 6 ± 1; protoplasmic astrocytes, 11 ± 1; Bergmann glia, 10 ± 1; oligodendrocytes, 6 ± 1. The total number of nuclear pores per nucleus varied from 18,451 ± 2,336 (Purkinje cells) to 621 ± 394 (granule cells) among neurons, and from 1,782 ± 162 (protoplasmic astrocytes) to 402 ± 67 (oligodendrocytes) among glial cells. The number of nuclear pores per unit nuclear volume (number/μm3), a parameter related to nucleocytoplasmic transport capacity, varied from 15 ± 2 in Purkinje cells to 6 ± 4 in granule cells. The proportion of nuclear membrane free of condensed chromatin was significantly (P<0.01) correlated to pore numerical density and total number of pores per nucleus. Some nuclear pores were associated in clusters of two or more pores. The amount of pore clustering was measured by counting the proportion of pores associated in clusters. This proportion varied among the different cell types from 82% in Purkinje cells to 44% in stellate and basket cells. The amount of pore clustering showed a positive linear correlation to pore numerical density and pore number per nucleus. However, the proportion of pores in clusters was not significantly correlated with the amount of condensed chromatin applied against the inner

ISSN:0092-7317    

DOI:10.1002/cne.902900311

出版商:Alan R. Liss, Inc.    

年代:1989

数据来源: WILEY