摘要:

AbstractThe retinal photoreceptors of the mutantrdsmouse are unable to form normal outer segments. Eventually the abnormal cells die in the months following birth. The genetic defect in therdsmouse was recently localized to the peripherin gene that encodes a protein in the outer segment disc margin. Although this mutation may explain the morphogenetic defect, i.e., the failure to form outer segments, the reason for subsequent cell death is not clear. Previously, we demonstrated that the capability to synthesize opsin, an outer segment integral membrane protein, is not compromised by the morphogenetic defect although the opsin steady‐state content is considerably reduced, since it is not incorporated into an organized outer segment. We have now studied arrestin, a cytoplasmic protein that is part of the phototransduction cascade and appears to shuttle between the inner and outer segment during the light/dark cycle. Sincerdsmice lack outer segments, it was of interest to determine the effects of the photoreceptor abnormality on arrestin gene expression. Arrestin mRNA levels and protein synthetic rates were high in youngrdsretinas. When corrected for cell loss, the steady‐state arrestin content per cell in therdsretina was comparable to normal. However, in the absence of an outer segment, the total amount of arrestin is concentrated in the remaining inner segment. Consequently, a relatively high level of arrestin is present in therdsinner segment throughout the light/dark cycle. We suggest that the morphogenetic defect indirectly precipitates secondary effects such as the persistent presence of high levels of arrestin or other soluble proteins in the abnormal photoreceptor inner segment, nucleus, and synaptic terminal. This condition, if toxic to the cells, may compromise photoreceptor viability in therdsret

ISSN:0092-7317    

DOI:10.1002/cne.903080102

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

年代:1991

数据来源: WILEY

摘要:

AbstractAndrogen‐sensitive motoneurons in the spinal nucleus of the bulbocavernosus (SNB) in adult male rats were labeled after intracellular iontophoresis of horseradish peroxidase, after which they were fully reconstructed in three dimensions in order to measure their dendritic trees. Three groups of rats were compared: intact adult male rats and male rats castrated as adults and given Silastic tube implants containing either testosterone or nothing. In the high‐androgen groups (intact males and testosterone‐treated castrates), soma size and the diameter of the first‐order dendrites were larger than in blank‐treated castrates. Moreover, the terminal dendrites in all groups possessed growth cones, implying that the dendrites of these motoneurons are capable of growth in adulthood. However, there were no statistically significant group differences in the length, membrane surface area, or volume of the dendritic trees, or in the orientation or branching symmetry of dendrites. In general, there were positive correlations between the size of the motoneuronal soma and various measures of the size of the dendritic tree and between the diameter of individual stem (first‐order) dendritic branches and the size of remainder of that dendrite. These data suggest that there may be a modest effect of androgen on the size of the dendritic trees of SNB motoneurons in adulthood, although the effect is much smaller than has previously be

ISSN:0092-7317    

DOI:10.1002/cne.903080103

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

年代:1991

数据来源: WILEY

摘要:

AbstractAnatomical studies using retrograde neuronal tracers were carried out to identify pudendal motoneurons and putative lumbosacral interneurons involved in the generation of penile reflexes in the adult male rat (Sprague‐Dawley). In agreement with previous studies, injection of the direct neuronal tracers, horseradish peroxidase or fluoro‐gold, into the left M. bulbospongiosus (dorsal division) resulted in direct retrograde labeling of motoneurons only in the ipsilateral dorsomedial (DM) nucleus. In contrast, similar injections of the transneuronal tracer, wheat germ agglutinin (WGA), resulted in direct retrograde labeling of ipsilateral DM motoneurons as well as transneuronal labeling of contralateral DM motoneurons and of bilaterally located putative spinal interneurons. The WGA‐labeling was determined to be transneuronal by a series of nerve cut experiments.The direct retrograde WGA‐labeling of ipsilateral DM motoneurons and the transneuronal WGA‐labeling of contralateral DM motoneurons and bilateral putative spinal interneurons occurred with different time courses. Direct retrograde labeling of ipsilateral DM motoneurons was seen at 20 hours survival and persisted up to 7 days survival. The shortest survival period for detecting transneuronal labeling of contralateral DM motoneurons and putative interneurons was 2 days. Transneuronal WGA‐labeling of contralateral DM motoneurons was transient in that the intensity of label increased from 2 to 3 days survival but was markedly reduced at 7 days survival. At the same time, the number of WGA‐labeled putative interneurons increased with longer survival times up to 7 days.WGA‐labeled putative interneurons were located primarily in regions receiving dendritic projections from WGA‐labeled DM motoneurons and, in particular, (1) the ventral gray matter between the DM and dorsolateral nuclei and (2) near the central canal and extending dorsally to the dorsal gray commissure. The rapid and extensive transneuronal transport between DM nuclei suggests that direct synaptic coupling may mediate coordinated, bilateral activation

ISSN:0092-7317    

DOI:10.1002/cne.903080104

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

年代:1991

数据来源: WILEY

摘要:

AbstractIt has been proposed that the pontine parabrachial nucleus (PBN) participates in the regulation of body fluid balance and the release of vasopressin from the neurohypophysis, although the pathways mediating the latter response are uncertain. This study in the rat, utilizing anatomical and electrophysiological methods, describes a projection from the lateral PBN towards the hypothalamic supraoptic nucleus (SON). Rats received iontophoretic injections of the anterograde tracerPhaseolus vulgarisleucoagglutinin (PHA‐L, 2% solution). After 14–17 days, rats were sacrificed and their brains prepared for immunofluorescent visualization of projections to the SON region. PHA‐L‐labelled terminals were found primarily in perinuclear regions immediately dorsal to the SON. In contrast, injections within the medial PBN and the nearby Kölliker‐Fuse nucleus did not reveal labelling in or around the SON. Extracellular recordings from 86 of 118 antidromically identified neurons in anaesthetized rats revealed a set of complex synaptic responses after stimulation in the PBN. Excitatory responses (in 82 of 86 cells) of short (100 msec, 43/82) duration were observed in both vasopressin‐ and oxytocin‐secreting cells of the SON, while 4/86 cells displayed a depressant response to PBN stimulation. In the adjacent perinuclear zone, 22/39 nonneurosecretory cells responded with an increase in their excitability consequent to an identical stimulus. These data suggest a predominantly facilitatory influence of lateral PBN neurons on SON neurosecretory cells in the rat, and that the PBN‐SON projection is an indirect one that utilizes an interneuronal network located in the perinuclear zone adj

ISSN:0092-7317    

DOI:10.1002/cne.903080105

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe central projections of the ethmoidal, glossopharyngeal, and superior laryngeal nerves were determined in the muskrat by use of the transganglionic transport of a mixture of horseradish peroxidase (HRP) and wheat germ agglutinin (WGA)‐HRP. The ethmoidal nerve projected to discrete areas in all subdivisions of the ipsilateral trigeminal sensory complex. Reaction product was focused in ventromedial portions of the principal nucleus, subnucleus oralis, and subnucleus interpolaris. The subnucleus oralis also contained sparse reaction product in its dorsomedial part. Projections were dense to ventrolateral parts of laminae I and II of the rostral medullary dorsal horn, with sparser projections to lamina V. Label in laminae I and V extended into the cervical dorsal horn. A few labeled fibers were followed to the contralateral dorsal horn. The interstitial neuropil of the ventral paratrigeminal nucleus was densely labeled.Extratrigeminal primary afferent projections in ethmoidal nerve cases involved the Kölliker‐Fuse nucleus and ventrolateral part of the parabrachial nucleus, the reticular formation surrounding the rostral ambiguus complex, and the dorsal reticular formation of the closed medulla. Retrograde labeling in the brain was observed in only the mesencephalic trigeminal nucleus in these cases.The cervical trunk of the glossopharyngeal and superior laryngeal nerves also projected to the trigeminal sensory complex, but almost exclusively to its caudal parts. These nerves terminated in the dorsal and ventral paratrigeminal nuclei as well as lamina I of the medullary and cervical dorsal horns. Lamina V received sparse projections.The glossopharyngeal and superior laryngeal nerves projected to the ipsilateral solitary complex at all levels extending from the caudal facial nucleus to the cervical spinal cord. At the level of the obex, these nerves projected densely to ipsilateral areas ventral and ventromedial to the solitary tract. Additional ipsilateral projections were observed along the dorsolateral border of the solitary complex. Near the obex and caudally, the commissural area was labeled bilaterally. Labeled fibers from the solitary tract projected into the caudal reticular formation bilaterally, especially when the cervical trunk of the glossopharyngeal nerve received tracer. Labeled fibers descending further in the solitary tract gradually shifted toward the base of the cervical dorsal horn. The labeled fibers left the solitary tract and entered the spinal trigeminal tract at these levels.Retrogradely labeled cells were observed in the ambiguus complex, especially rostrally, and in the rostral dorsal vagal nucleus after application of HRP and WGA‐HRP to either the glossopharyngeal or superior laryngeal nerves. In glossopharyngeal nerve cases, retrogradely labeled neurons also were seen in the inferior salivatory nucleus.These results suggest convergence of primary afferent fibers innervating the upper respiratory tract of the muskrat into the paratrigeminal nuclei and lamina I of the medullary dorsal horn. These data show that the cervical branch of the glossopharyngeal nerve and the superior laryngeal nerve have robust projections into the solitary complex but the ethmoidal nerve has no such proje

ISSN:0092-7317    

DOI:10.1002/cne.903080106

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

年代:1991

数据来源: WILEY

摘要:

AbstractEvidence for survival and growth of fetal substantia nigra grafts in host striatum and partial reversal of behavioural and biochemical deficits in the host animal is well documented. Afferent synaptic connections arising from the graft and contacting host structures have also been reported; however, the properties of the neurons receiving this input is less clear. The purpose of this study was to determine if substance P‐containing neostriatal neurons receive a dopaminergic input from nigral grafts. Fetal substantia nigra cell suspensions were stereotaxically implanted in the deafferented neostriatum of Wistar rats 2 weeks after a unilateral 6‐hydroxydopamine (6‐OHDA) lesion in the ipsilateral substantia nigra or medial forebrain bundle. The ultrastructural features of the graft‐host synaptic interactions were analysed by employing an electron microscope immunocytochemical double‐labeling technique. Tyrosine hydroxylase (TH) and substance P‐immunoreactive structures were simultaneously demonstrated by means of the peroxidase‐antiperoxidase method using two different chromogens with distinct reaction products easily differentiated at the light and electron microscope levels. TH‐immunoreactive sites were first demonstrated using 3,3′‐diaminobenzidine tetrahydrochloride (DAB); then substance P immunoreactivity was localized using benzidine dihydrochloride (BDHC). TH‐immunoreactive terminals of axons originating from the graft made synaptic contacts with substance P‐positive cell bodies and dendrites from the host. These results indicate that at least partial restoration of the normal nigrostriatal circuitry can be achieved following nigral grafts. The demonstration of specific synaptic input on host substance P neurons provides an anatomical basis for direct functional modulation of the deafferented host neostria

ISSN:0092-7317    

DOI:10.1002/cne.903080107

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

年代:1991

数据来源: WILEY

摘要:

AbstractCapsaicin is a neurotoxin capable of causing degeneration in specific sites throughout the neuraxis, including the suprachiasmatic nucleus (SCh), the ventrolateral geniculate nucleus (VLG), the intergeniculate leaflet (IGL), and the olivary and medial pretectal nuclei (OPT and MPT). In this experiment, we tested the hypothesis that capsaicin‐induced terminal degeneration in the SCh, VLG, IGL, OPT, and MPT results from destruction of retinal ganglion cells and their axonal projections to these sites. In the first experiment, silver stains were used to examine degeneration in the retina induced by systemic capsaicin treatment. Capsaicin caused degeneration of ganglion cells, bipolar cells, and nerve terminals in the retina, which could be observed between 2 and 24 hours after treatment. In the second experiment, 15‐day‐old rat pups were enucleated unilaterally. Five days or 2, 5, or 10 months later, they were injected systemically with capsaicin and killed 6 hours (pups) or 18 hours (adults) later for analysis with a cupric silver stain. In rats of all ages, prior monocular enucleation reduced or eliminated capsaicin‐induced degeneration in the contralateral SCh, VLG, IGL, OPT, and MPT. In the third experiment, rat pups were treated systemically with capsaicin or vehicle solution at 12 days of age and given unilateral intravitreal injections of cholera toxin conjugated to horseradish peroxidase (CT‐HRP) 3 days prior to sacrifice at 20 days of age. Transport of CT‐HRP to the SCh, VLG, IGL, MPT, and OPT was attenuated but not abolished by capsaicin pretreatment. Results suggest that capsaicin causes degeneration in the SCh, VLG, IGL, MPT, and OPT by selective destruction of a subpopulation of retinal ganglion cells with axonal projections to

ISSN:0092-7317    

DOI:10.1002/cne.903080108

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe tree shrew (Tupaia belangeri) has a cone‐dominated retina with a rod proportion of only 5%. This is in contrast to the usual mammalian pattern of rod‐dominated retinae. Rod bipolar cells are present at relatively low densities in the tree shrew retina, suggesting that a reduced, but normal, rod pathway might be preserved. The present study investigated another common constituent of the rod pathway, the dopaminergic amacrine cells, and analysed their morphology and distribution by light and electron microscopy.Catecholaminergic (presumed dopaminergic) amacrine cells were labelled with an antibody against tyrosine hydroxylase (TH). Intense TH‐immunoreactivity was found in perikarya and dendrites of a uniform amacrine, cell population. TH‐immunoreactive amacrine cell density varies across the retina from 10 cells/mm2in the periphery to 40 cells/mm2in more central regions (mean cell density about 25 cells/mm2). The relatively large cell bodies are located exclusively in the innermost part of the inner nuclear layer. The dendrites form a dense plexus at the border between the inner plexiform layer and the inner nuclear layer. The finer dendritic processes contain many varicosities and form characteristic dendritic “rings” like those seen in other mammals. TH‐immunoreactive processes also run between cell bodies in the vitread inner nuclear layer; a few extend into the sclerad inner nuclear layer and occasionally reach the outer plexiform layer (possible interplexiform cells). A few TH‐immunoreactive processes are seen in the middle of the inner plexiform layer. Electron microscopy of TH‐immunoreactive processes revealed conventional synapses onto somata and processes of unlabell

ISSN:0092-7317    

DOI:10.1002/cne.903080109

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

年代:1991

数据来源: WILEY

摘要:

AbstractTract tracing techniques combined with immunohistochemistry in rats and guinea pigs have demonstrated the existence of a hypothalamo‐lateral septum enkephalinergic pathway. Numerous enkephalinergic nerve endings encompass cell bodies located in the lateral septum. The present immunocytochemical study, at light and electron microscopic levels, was undertaken in the guinea pig brain to determine whether the contacted perikarya contain γ‐aminobutyric acid (GABA).The antisera against GABA revealed the presence of immunoreactive cell bodies throughout the lateral septum. At the light microscopic level, most GABA neurons appeared round while others were oval with one or two emerging dendrites. Ultrastructurally, cell bodies displayed a moderate number of organelles and a pale nucleus with frequent indentations of the nuclear envelope.The precise relationship between GABA neurons and enkephalinergic terminals was examined by means of a double‐immunostaining method showing that 60% of cell bodies receiving synaptic inputs from enkephalinergic afferents contained GABA.These results show that the hypothalamo‐septal enkephalinergic pathway prominently innervates GABA‐containing neurons and also provide anatomical basis suggesting a disinhibitory role for this enkephaline

ISSN:0092-7317    

DOI:10.1002/cne.903080110

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe distribution of galanin‐like immunoreactivity (GAL‐LI) in the spinal cord of the cat was studied by use of indirect histochemistry and the peroxidase‐antiperoxidase (PAP) technique. In the ventral horn GAL‐immunoreactive (IR) axonal fibers and terminals were most frequent in the ventral part of the motor nucleus. The GAL‐IR axons also contained 5‐hydroxytryptamine (5‐HT)‐LI, and they disappeared after spinal cord transection. It was concluded that these GAL‐IR fibers belong to the serotoninergic bulbospinal pathway. In the medulla oblongata from normal cats, scattered GAL‐IR cell bodies were encountered within the nucleus raphe obscurus and nucleus raphe pallidus. Electron microscopic observations revealed that the fine structure of the GAL‐IR axonal boutons in the motor nucleus was similar to that of 5‐HT‐IR boutons with a varying number of immunoreactive large dense core vesicles. The postsynaptic element in all cases studied was a dendrite.A dense GAL‐IR axonal plexus was found in the superficial laminae I‐II of the dorsal horn. Coexistence was found between the GAL‐ and substance P‐LI in fibers within the dorsal horn plexus. Spinal cord transection did not alter the pattern of GAL‐LI in the dorsal horn, while the vast majority of GAL‐IR axonal swellings disappeared following dorsal root sectioning. Electron microscopic observations in lamina II (substantia gelatinosa) revealed that the GAL‐IR axonal terminals could be divided into two main groups. One with small to medium‐sized axonal buttons formed synaptic contacts with both dendritic and axonal profiles. The other formed the central axon terminals of glomeruli, suggesting that GAL‐LI may be present in C‐type primary afferents. Numerous small GAL‐IR cell bodies were encountered in laminae II and III. GAL‐IR cell bodies were also observed in lamina X.The dorsal root ganglia contained a low but consistent number of small to medium‐sized GAL‐IR cell bodies, which all contained immunoreactive calcitonin gene‐related peptide (CGRP). Following peripheral sciatic nerve transection, the number and the labeling intensity of GAL‐IR cell bodies in the corresponding dorsal root ganglia showed a moderate increase.Radioimmunoassay revealed that the concentration of GAL‐LI increased along the rostrocaudal axis of the normal spinal cord, and was about three times higher in the dorsal than in the ventral regions. The concentration in the dorsal root ganglia was intermediate to those seen in the corresponding dorsal and ventral cord regions. Autoradiography showed a high density of125I‐GAL binding sites in the supe

ISSN:0092-7317    

DOI:10.1002/cne.903080111

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

年代:1991

数据来源: WILEY