摘要:

AbstractNeutral endopeptidase 24.11 (NEP; “enkephalinase”) may inactivate a number of centrally active neuropeptides including the enkephalins and substance P. In most areas of the central nervous system, the cell types which express NEP activity are not known. The hypoglossal nucleus (N. XII) was selected as a model system to characterize the cytochemical localization of NEP. The effect of hypoglossal nerve axotomy upon the distribution of NEP activity in the hypoglossal nucleus was compared to the effect upon cholinergic markers, the muopiate receptor, and the enkephalins.By use of a fluorescence histochemical method, NEP was localized at all levels of N.XII to the soma and proximal processes of the majority of the apparent motor neurons in the nucleus.Fluorescent double‐labeling studies revealed the presence of numerous enkephalinergic varicosities which localized to the neuropil surrounding NEP‐stained motor neurons. Todetermine whether NEP was synthesized by these motor neurons, 18 rats received a unilateral transection of the hypoglossal nerve. A pronounced decrease in NEP staining in N.XII wasobserved on the operated side as early as 3 days following axotomy. This decrease persisted at all levels of the nucleus for about 5 weeks. By 7 weeks, the staining between the control andoperated sides was indistinguishable. By contrast, there was no apparent change in the density or distribution of enkephalin‐immunoreactive varicosities in five animals examined 6 to 32 daysfollowing axotomy. Radioligand binding of [3H]DAMGO to the μ‐opiate receptor in N.XII wasstudied in 20 animals by quantitative autoradiography at 2, 6, and 11 days after axotomy. No significant changes in the level of radioligand binding to the μ‐receptor were detected inresponse to axotomy. In contrast to the opiate system, the cholinergic enzymes choline acetyltransferase, acetylcholinesterase, and pseudocholinesterase showed a coordinate decreasein motor neuron‐associated staining on the operated side of N.XII at 3 ,6 , and 11 days following axotomy which paralleled the decrease in NEP staining. By contrast, the lysosomal enzymemarker, acid phosphatase, showed a pronounced increase in staining on the operated side.The results of this study are consistent with the synthesis of NEP by cholinergic N.XII motor neurons and indicates that the enkephalins and NEP in N.XII are closely associated, but derive from separate neuronal populations. The widespread overlap in the distribution of NEP‐stained motor neurons and enkephalinergic varicosities in N.XII provides additional anatomical support for a potential role for NEP in the inactivation of centrally active enkephalins. The apparently stable levels of the enkephalins and μ‐opiate receptor after axotomy, in contrast to the coordinate decrease in cholinergic enzyme staining, suggest a differential regulation of the opiate and cholinergic systems in response to axotomy.

ISSN:0092-7317    

DOI:10.1002/cne.903400202

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractCholinergic neurons in the chick auditory brainstem were studied with the aid of an antiserum to choline acetyltransferase (ChAT), the biosynthetic enzyme for acetylcholine. ChAT‐immunoreactive (ChAT‐I) neurons were found in a ventrolateral and a dorsomedial cell group. The ventrolateral group is a rostrocaudally directed column of cells that surround the superior olive (SO), are ventromedial to the ventral facial nucleus (VIIv), and are lateral to the nucleus pontis lateralis (PL) as far rostrally as the nucleus subceruleus ventralis. Cells in the dorsomedial group were found in the pontine reticular formation medial to the dorsal facial nucleus and lateral to the abducens nerve root. Occasionally, small ChAT‐I cells were found in the crossed dorsal cochlear tract and in the medial vestibular nucleus near the dorsal border of the caudal nucleus magnocellularis (NM). No ChAT‐I neurons or fibers were observed in NM, nucleus angularis, nucleus laminaris, in the nuclei of the lateral lemniscus, or in the nucleus mesencephalicus lateralis pars dorsalis.To determine which cholinergic neurons project to the cochlea, a double‐labeling technique was used combining ChAT‐I and the retrograde transport of biotinylated dextran amine (BDA) from the inner ear. Double‐labeled cells were found bilaterally in both the ventrolateral and dorsomedial cell groups, with the exception of large ChAT‐I cells dorsal to the SO, which do not appear to project to the cochlea. Cholinergic cells that project to the cochlea were classified into three morphological groups: multipolar, elongate, and round‐to‐oval. Both the ventrolateral and the dorsomedial cell groups appear to have a mixture of these different cell types. The average somal area of cholinergic cochlear efferents was 246 μm2. Only about 70% of the cochlear efferent neurons, however, are cholinergi

ISSN:0092-7317    

DOI:10.1002/cne.903400203

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractGAP‐43 is a membrane‐bound protein selectively concentrated in axonal growth cones during brain development and implicated in axonal outgrowth and elongation. A sex dimorphism in the number of synapses in certain regions of the adult rat brain has been attributed to differences in gonadal steroid hormone action during early postnatal life. The results of recent studies have demonstrated that gonadal steroids modulate GAP‐43 mRNA in regions of the postnatal and adult brain where steroid hormone receptors are concentrated. Since gonadal steroids influence the development of the sexually undifferentiated brain during the first few weeks of postnatal life, the present study investigated the ontogeny of GAP‐43 mRNA in the male and female rat brain between postnatal days 1 and 25. On postnatal days 1, 3, 6, 12, 18, and 25, brains were collected from male and female postnates and frozen, and 16 μm cryostat sections were processed and hybridized with a35S‐labeled antisense riboprobe complementary to GAP‐43 mRNA. Evaluation of film autoradiograms demonstrated a widespread distribution of GAP‐43 mRNA in postnatal brain regions, including the cerebral cortex; bed nucleus of the stria terminalis; and medial preoptic area, ventromedial nucleus, and arcuate nucleus of the hypothalamus. Densitometric measurements revealed that GAP‐43 mRNA was transiently elevated during early postnatal life, with a subsequent decrease during brain maturation, although the pattern of change varied among the brain regions investigated. In addition, the level of GAP‐43 hybridization signal was significantly higher in the male cortex, bed nucleus, and medial preoptic nucleus, but not the ventromedial and arcuate nuclei, than in postnatal females. Analysis of slide autoradiograms demonstrated that the change in GAP‐43 mRNA during postnatal development was due to changes at the cellular level. The present results indicate that expression of GAP‐43 mRNA is transiently elevated and sexually dimorphic in certain regions of the early postnatal rat brain. The results further suggest that the differential expression of GAP‐43 in the male and female postnatal brain may be related to sex differences in neuronal outgrowth and connectivity resulting in a dimorphism in the pattern of adult neuronal circ

ISSN:0092-7317    

DOI:10.1002/cne.903400204

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe metamorphic fate of larval visual interneurons in the swallowtail butterflyPapilio xuthushas been examined by using reduced silver impregnation and immunocytochemistry of γ‐amino butyric acid (GABA). Visual interneurons in the second larval optic neuropile (medulla) can be followed throughout metamorphosis because of large somata located in the anterior edge of the imaginal medulla. Ten to 12 neurons in the larval medulla were immunoreactive to a GABAantiserum. They arborize in the larval medulla and extend dendritic processes to the first larval optic neuropile (lamina). After pupation, the medulla neurons lose GABA‐immunoreactive larval processes and differentiate new processes that enter tangentially into the developing imaginal medulla. Axons of the surviving larval neurons follow an optic tract between the lobula and the lobula plate and extend to the lateral area of the protocerebrum. Thus, larval visual interneurons are incorporated into the imaginal optic lobe and may play a new role in the visual processing of the butterfly. © Wiley‐Li

ISSN:0092-7317    

DOI:10.1002/cne.903400205

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractIn the central nervous system (CNS) myelin is present not only in white matter, but also in varying amounts in many gray matter areas. In addition to the function of electrical insulation of axons, myelin and oligodendrocytes contain molecules that are powerful inhibitors of neurite growth. Nevertheless plastic changes involving sprouting of nerve terminals occur in several brain regions of adult animals after partial lesions. In this study we have tried to correlate the plastic potential of CNS regions with the degree of their myelination. The expression of the growth‐associated protein GAP‐43 was used as an indicator of the potential for plastic changes, and a histological myelin stain was used to assess myelination. We have found that myelination and GAP‐43 expression have strikingly inverse expression patterns in the majority of CNS gray matter areas. Densely myelinated regions, that is, most brainstem nuclei, the tegmentum, and the inferior colliculus, are low in GAP‐43. In contrast, unmyelinated or lightly myelinated areas, such as the substantia gelatinosa of the spinal cord, the nucleus of the solitary tract, or the septum, express high levels of GAP‐43. Areas known to show lesion‐induced sprouting are typically high in GAP‐43 and only lightly myelinated. During postnatal development the myelination pattern precedes the GAP‐43 pattern, a sequence that is consistent with a role of myelin and the associated neurite growth inhibitors in modifying GAP‐43 expression.Our results support the hypothesis that myelin‐associated neurite growth inhibitors are involved in regulating the stability of neural connections

ISSN:0092-7317    

DOI:10.1002/cne.903400206

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractPrevious studies indicate that vibrissa, nonvibrissa, guard hair, hairy skin, and periodontal ligament afferents give rise to morphologically distinct terminal arbors in the trigeminal nuclei principalis (Vp) and oralis (Vo) in the cat. The present study describes the extent to which morphological and functional relationships exist in the nuclei interpolaris (Vi) and caudalis (Vc). Twenty‐two fibers were physiologically characterized and stained by intra‐axonal HRP injection techniques. The fast adapting (FA) vibrissa (VF) afferents gave rise to compact and circumscribed arbors in Vj and Vc. These tended to be larger in Vc than in Vi. The slowly adapting (SA) vibrissa (VS) afferents in Vi and Vc had more widespread and larger arbors than those of the VF afferents. The VS arbors in Vc tended to be larger and less circular than those in Vi. Guard hair (GH) afferents gave rise to circumscribed arbors in both nuclei, but those in Vc tended to have larger and more circular arbors than those in Vi. Down hair (DH) afferents gave rise to small, circumscribed arbors or a few distinct patches of boutons within a small area in Vi; arbors in Vc were less extensive and “stringy.” Unlike other afferents, DH arbors were larger in Vi than in Vc, but smaller than those of GH afferents in either nuclei. The SA hairy skin (SS) afferents had arbors that were widespread with a few distinct patches of boutons; the arbors in Vc were larger than those in Vi. The arbors of SS afferents were smaller than those of VS and GH afferents in both nuclei. Like GH afferents, FA periodontal ligament (PF) afferents gave rise to large and circumscribed arbors in Vi, although the arbors in Vc were smaller and less dense. The present study demonstrated significant functional and morphological relationships for primary afferents in Vi and Vc, thus suggesting that sensory information from each of the distinct fiber or functional classes is processed in a characteristic manner in the individual nuclei. © Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903400207

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe distribution of tenascin was examined in the lesioned adult rat optic nerve and central nervous system (CNS) non‐neuronal cells in vitro, by means of a double immunofluorescence technique. Tenascin‐like immunoreactivity is localized to the leptomeninges and astrocytes that border the site of optic nerve transection. Anti‐tenascin labeling was observed as early as 24 hours after transection, when it appeared as a fine interface between leptomeninges and neural tissue. The anti‐tenascin labeling increased in the cells at this border zone during the next 2 weeks, and disappeared 18–21 days after transection. In vitro studies further confirmed that both astrocytes and leptomeningeal cells express tenascin as detected by immunofluorescence labeling with anti‐tenascin antibodies. However, the pattern of immunolabeling associated with the two cell types differed. Astrocytes showed exclusively punctate labeling of the cell surface, while leptomeningeal cells showed mainly coarse, fibrillary, matrix‐like deposits. Astrocytes and leptomeningeal cells remained segregated when cocultured. In these cultures, an increased amount of the fibrillary, matrix‐like deposits of tenascin was also observed in the region of the interface between astrocytes and leptomeningeal cells when these two cell types contact each other. Given the antiadhesive and antispreading properties of tenascin, these in vivo and in vitro results suggest that tenascin might playa role in the initial segregation of leptomeningeal cells from neural tissue at the site of CNS trauma during the first 2 weeks after injury, i.e., prior to the formation of a fully differentiated glia limitans. Therefore, tenascin may influence the early stages in the formation of the glia limitans, and thus prevent the indiscriminate migration of leptomeningeal cells into CNS tissue after injury. ©

ISSN:0092-7317    

DOI:10.1002/cne.903400208

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractSecretoneurin is a peptide of 33 amino acids generated in brain by proteolytic processing of secretogranin II. The distribution of this newly characterized peptide was investigated by means of immunocytochemistry and in situ hybridization in the spinal cord and lower brainstem of the rat. The staining pattern of secretoneurin immunoreactivity (IR) was compared to that of substance P (SP) and calcitonin gene‐related peptide (CGRP) in adjacent sections. A high density of secretoneurin‐IR fibers and terminals was found in lamina I and outer lamina II of the caudal trigeminal nucleus and of the spinal cord at all levels, around the central canal, and in the sympathetic and parasympathetic areas of the lateral cell columns. The ventral horn displayed a low to moderate density of secretoneurin‐IR. The highest number of secretogranin II mRNA‐containing cells was found in lamina II of the dorsal horn and in neurons of the dorsal root ganglia. In the white matter, secretoneurin‐IR was most prominent in the dorsolateral part of the lateral funiculus and in the tract of Lissauer. The distributions of secretoneurin‐IR and SP‐IR were strikingly similar. CGRP‐IR and secretoneurin‐IR overlapped in the outer laminae of the dorsal horn, in the lateral cell column, and probably in some motoneurons. This study establishes that, like SP and CGRP, secretoneurin is a peptide highly concentrated in the terminal field of primary afferents and in sympathetic and parasympathetic areas. Thus secretoneurin might be involved in the modulation of afferent transmission.

ISSN:0092-7317    

DOI:10.1002/cne.903400209

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

Abstract3H‐2‐deoxyglucose (2‐DG) is used as a histological marker to study the spatial distribution of neuronal activity in the central brain ofDrosophila melanogasterunder controlled stimulus conditions. Tethered flies injected with the label are kept for 45–90 minutes in the center of a rotating drum carrying on its periphery a singe black vertical stripe or a periodic grating. In either stimulus situation, one‐half of the flies walk on top of a small black styrofoam ball floating on ajet of air, and one‐half are kept flying 1.5 mm above the ball. (1) During walking on the styrofoam ball little 2‐DG accumulates in the central brain. The area in and around the ellipsoid body as well as several tracts are weakly labeled. (2) After flight, labeling patterns are more distinct. The following labeled structures can be identified: ventral bodies, ring neurons of the ellipsoid body, the region of the inferior bridge, fiber tracts connecting the central complex to other parts of the protocerebrum, and tracts in the subesophageal and dorsal brain. These contrast with fan‐shaped body and protocerebral lobes, which are only weakly labeled. (3) Not only flight and walking lead to distinct staining patterns but also the two visual stimuli. With the single stripe, in most flies the caudal layers of the ellipsoid body accumulate more 2‐DG than the rostral ones. With the striped drum, the ellipsoid body is uniformly labeled. (4) Other stimulus‐related features are found less regularly: Unilateral distribution of 2‐DG in or around the noduli was observed in several flies that had been exposed to a rotating single stripe. In one preparation, two strongly marked individual neurons of the protocerebral bridge can be tentatively identified. The labeling patterns support earlier notions that the central complex is involved in the initiation and organization of behavior and that it integrates visual data of the two brain hemispher

ISSN:0092-7317    

DOI:10.1002/cne.903400210

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractKeratins are the predominant intermediate filament proteins in the nonneuronal cells of the goldfish optic nerve. At least three different keratin pairs are expressed in this tissue, indicating an unexpected complexity. Expression of the type II keratin ON3in goldfish opticnerve astrocytes predicts the expression of a type I keratin partner. Here we report the cDNA sequence and predicted amino acid sequence of two type I keratins from the goldfish optic nerve, designated GK48 and GK49. The GK48 protein is the goldfish equivalent of mammalian keratin 18 (K18) and is the most likely type I keratin partner to the ON3protein. The GK49 protein is similar to the GK50 protein, a type I keratin characterized previously from the goldfish optic nerve. The GK48 and ON3mRNAs are expressed in a variety of goldfish tissues, whereas the expression of GK49 mRNA has a more limited expression. In addition, in situ hybridization experiments show that the expression of the GK48 and ON3mRNAs are evenly distributed throughout the optic nerve, while the GK49 mRNA is expressed along longitudinal lines. These results show that there is a diversity of keratin expression within different cell types in the goldfish optic nerve. © Wiley‐Liss, I

ISSN:0092-7317    

DOI:10.1002/cne.903400211

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY