摘要:

AbstractTwo identified cricket: auditory interneurones, AN1 and AN2, were intracellularly labelled with horseradish peroxidase following physiological characterisation. The neurones, which have some structural similarities, have their somata in the prothoracic ganglion and axons that project to the brain. Although both carry auditory information, they have different response properties and participate in different types of phonotactic behaviour. Ultrathin sections from selected regions of their Prothoracic arborisations were examined in the electron microscope after postembbdding immunostaining for the inhibitory transmitter GABA. In the prothoracic ganglion AN1 branches only in the medial ventral association centre (mVAC) contralateral to the soma, and receives only input synapses. Twenty‐seven percent of these were made by processes ‐immunoreactive for GABA. AN2 branches not only in mVAC on both sides of the ganglion but also in several other areas. It makes output synapses from large diameter neurites in mVAC on both sides of the ganglion as well as from neurites in more posterior regions of the neuropile. Most input synapses are received onto branches in the contralateral mVAC where about 19% were made from GABA‐immunoreactive processes. © 1994 Wiley‐L

ISSN:0092-7317    

DOI:10.1002/cne.903450402

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractNeurotensin (NT) neurons in the rat preoptic area are implicated in female‐specific regulation of reproduction. Estrogen markedly increases expression of mRNA encoding the neurotensin/neuromedin N (NT/N) precursor in several cell groups of the preoptic area, including the anteroventral periventricular nucleus, periventricular preoptic nucleus, and medial preoptic nucleus. In the present study, immunohistochemistry was performed on tissue from ovariectomized females with or without estradiol treatment to test the hypothesis that increased levels of NT accompany hormonal induction of NT/N mRNA in these cell groups. Since colchicine treatment is required for visualization of NT‐immunoreactive cell bodies, an additional objective of this study was to determine whether colchicine alters expression of NT/N mRNA in this area. Estradiol caused a pronounced increase in the number of NT‐immunoreactive cell bodies in the anteroventral periventricular nucleus, as well as adjacent parts of the periventricular preoptic nucleus and medial preoptic nucleus. In the absence of colchicine, estradiol increased the number of NT‐immunoreactive fibers in these same regions. Surprisingly, NT‐immunoreactive cell bodies with intense staining were abundant in certain parts of the medial preoptic nucleus regardless of hormonal condition. NT‐immunoreactive cell bodies were also numerous in certain regions where NT/N mRNA‐expressing cells are scarce, and in two of these regions, the median preoptic nucleus and vascular organ of the lamina terminalis, estradiol substantially reduced the number of immunoreactive cell bodies. Treatment of ovariectomized females with colchicine induced expression of NT/N mRNA in the same regions where NT‐immunoreactive cell bodies were unexpectedly numerous, thus providing a compelling explanation for the discordant distributions of the mRNA and peptide. Together with previous findings, the present results indicate that increased levels of NT accompany hormonal induction of NT/N mRNA in the anteroventral periventricular nucleus, as well as adjacent parts of the periventricular preoptic nucleus and medial preoptic nucleus. In other regions of the preoptic area, colchicine‐inducible expression of NT/N mRNA confounds assessment of hormonal influences on NT synthesis. Multiple populations of neurons capable of NT synthesis can be distinguished in the rostral preoptic area on the basis of differential responsiveness to estrogen or colchicine, thereby providing additional evidence for functional heterogeneity among NT‐synthesizing neurons in this region. ©

ISSN:0092-7317    

DOI:10.1002/cne.903450403

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe present study establishes that populations of neurons in the lumbosacral cord, which innervate pelvic striated muscles, express p75NGFRthroughout their life spans. These neuronal groups comprise the Onuf's nucleus in humans and its principal rat homologues, dorsolateral (DL) and dorsomedial (DM) nuclei, as well as the cremasteric (CRE) nucleus. The p75NGFRin these neurons is localized in the rough endoplasmic reticulum, Golgi complex, and lysosomes. Almost all neurons that project to striated perineal muscles in the male rat express p75NGFR; very low levels of p75NGFRare detected in neurons that innervate perineal sphincters of the female. In the female rat, p75NGFRexpression is masculinized with perinatal androgen treatment. In addition, the expression of p75NGFRin DM and DL neurons in the adult is up‐regulated by injury (i. e., pudendal axotomy) but is not influenced by gonadectomy. The results of this study establish that neurons of Onuf s nucleus and its rat homologues differ from general somatic motor neurons in that they express p75NGFRfrom early postnatal life (i. e., when all motor neurons express p75NGFR) into the adult (when the former, but not the latter, express the receptor). In view of growing evidence for the role of neurotrophins in the physiology of motor neurons, the above differentiating feature between general somatic and sexually dimorphic motor neurons suggests that p75NGFRmay be involved in motor neuron plasticity and may participate in mechanisms by which neurons can protect themselves from degenerative insults. © 1994 Wiley‐Liss,

ISSN:0092-7317    

DOI:10.1002/cne.903450404

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe amino acid gamma‐aminobutyric acid (GABA) is an important inhibitory neurotransmitter in both vertebrates and invertebrates. Despite this, no reports of GABA in flatworms have to date been published. We have studied the presence of GABA in the planarianDugesia tigrinawith immunocytochemical methods and high‐pressure liquid chromatography. Fibers showing GABA‐like immunoreactivity (GABA‐IR) were present in abundance in the longitudinal nerve cords and lateral nerves. GABA‐IR was revealed in fibers forming commissures in the brain. The ventral part of the subepidermal plexus showed GABA‐IR. No cell somata containing GABA‐IR could be identified with certainty.The chromatographic analysis showed that the average GABA concentration inD. tigrinais 533.6 pmol/mg protein. This is substantially higher than the concentrations of dopamine (62.87 pmol/mg) and serotonin (233.20 pmol/mg). An enzyme assay confirmed the capacity for GABA‐synthesis inD. tigrina. The results indicate that GABA‐containing neurons appeared earlier in evolution than was previously thought and that GABA may serve an important role already in the flatworms. © 19

ISSN:0092-7317    

DOI:10.1002/cne.903450405

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe avian hippocampal formation has previously been shown to contain many of the same neurotransmitters and related enzymes that are found in mammals. In order to determine whether the relatively delayed development of the mammalian hippocampus is typical of other vertebrates, we investigated the maturation of a variety of heuroactive substances in the hippocampal formation of the homing pigeon. The distribution of two transmitter‐related enzymes, choline acetyltransferase (ChAT) and tyrosine hydroxylase (TH), the neurotransmitter GABA, and four neuropeptides (substance P, enkephalin, neuropeptide Y, and somatostatin) was studied by immniunohistochemistry in the developing hippocampal complex. The pattern and/or the time course of changes in the distribution of immunoreactivity varied among the different neuroactive substances examined. Immunoreactivity to ChAT and TH was found exclusively in fibers and terminal‐like processes, whereas GABA and peptide immunoreactivity was seen in cells and neuropil. Quantitative differences in the density, number, and size of stained cells were assessed by a computer‐assisted image analyzer. For the majority of the substances, developmental patterns in the distribution of immunoreactivity differ between the hippocampus proper and the area parahippocampalis, the two major areas that together make up the avian hippocampal complex. The adult pattern of immunoreactivity was generally attained by 3 weeks after hatching. For many of the neuroactive substances found in cell bodies, there was a gradual decrease in the density of immunoreactive cells with a concomitant increase in the density of immunoreactive neuropil. The actual number of stained cells usually increased to a peak at 9 days posthatching and then declined until 3 weeks posthatching, when the adult value was reached. These results are discussed in relation to the advantages that the pigeon hippocampal complex may provide in the study of developmental processes. Parallels with the distribution of the same neuroactive substances in the mammalian hippocampus are used to suggest possible functional similarities between the avian and mammalian hippocampal regions. © 1994 Wiley‐L

ISSN:0092-7317    

DOI:10.1002/cne.903450406

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe striatum receives topographic cortical inputs with the limbic lobe terminating in the ventral striatum and sensorimotor cortical regions terminating in the dorsolateral striatum. The organization of striatonigral projections originating from these different striatal territories was examined in primate by using several anterograde tracers.The ventral striatum innervates a large area of the substantia nigra, including the medial pars reticulata and much of the pars compacta. Moreover, projections from separate areas of the ventral striatum overlap considerably in the substantia nigra. No mediolateral or rostrocaudal topographic order is apparent, and the area of the substantia nigra associated with the ventral striatum is extensive. In contrast, the sensorimotor‐related striatum innervates a limited region of the ventrolateral substantia nigra. Similar to ventral striatonigral projections, projections originating from different areas of the sensorimotor‐related striatum send converging inputs to the substantia nigra. Sensorimotor‐related striatonigral projections avoid the region of the dopaminergic neurons in the dorsal pars compacta. Striatonigral projections from the sensorimotor‐related and ventral striatum do not overlap in the substantia nigra. Examination of the outputs of discrete striatal loci indicates that the organization of striatonigral projections is more related to corticostriatal inputs than to a simple rostrocaudal, dorsoventral, or mediolateral tpography of the striatum.Striatal projections that originate from different striatal territories are distinct and nonoverlapping, thus supporting the concept of segregated striatonigral circuits. However, areas of the striatum that receive common cortical inputs send converging inputs to the substantia nigra. This suggests that the substantia nigra is also an important link for integrating information between functionally related (sub)circuits. © 1994 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903450407

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractAnatomical and electrophysiological studies have indicated that a reciprocal projection from the ventral pallidum back to the nucleus accumbens exists and has functional relevance. In this study, the topographical projection from the ventral pallidum to the nucleus accumbens was examined by using retrograde tracing with fluoro‐gold iontophoresed in subcompartments of the nucleus accumbens in rats combined with either in situ hybridization for glutamic acid decarboxylase and preproenkephalin mRNA or substance P immunoreactivity. Deposits made into the medial nucleus accumbens preferentially labeled neurons in the medial ventral pallidum, while deposits into the dorsolateral nucleus accumbens, at or lateral to the anterior commissure, labeled primarily cells in the dorsal and lateral ventral pallidum. A mediolateral to rostrocaudal topography was also observed, with the medial deposits preferentially labeling cells in rostral ventral pallidum and the lateral deposits resulting in retrogradely labeled cells in the ventral pallidum below the crossing of the posterior anterior commissure (subcommissural) as well as below the globus pallidus (sublenticular). The majority of cells retrogradely labeled with fluoro‐gold were double‐labeled for glutamic acid decarboxylase mRNA. In contrast, very few retrogradely labeled neurons in the ventral pallidurn were double labeled for mRNA for preproenkephalin. These data demonstrate a topographically organized projection from the ventral pallidum, to the nucleus accumbens that is primarily γ‐aminobutyric acid (GABA)‐ergic and reciprocal to the GABAergic projection from the nucleus accumbens to the ventral pallidum. © 1994 Wile

ISSN:0092-7317    

DOI:10.1002/cne.903450408

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe goal of this study was to determine the pattern of gamma‐aminobutyric acid (GABA) expression in the retina and optic nerve of the zebrafish (Brachydanio rerio) during embryonic development. Zebrafish embryos were fixed at intervals between 1 and 4 days postfertilization, and semithin plastic sections were prepared for postembedding immunocytochemistry with antisera, against GABA. Sections were also prepared from several adult zebrafish eyes for comparison. GABA immunoreactivity first appeared in the optic nerve at 2 days postfertilization, and by 2.5 days the inner nuclear layer (INL), inner plexiform layer (IPL), retinal ganglion cell layer, and optic nerve were all positive for GABA. The GABA expression in the retinal ganglion cell layer and optic nerve was transient, however, and these structures were largely unlabeled by 4 days postfertilization. The pattern of GABA immunoreactivity at 4 days resembled that seen in the adult zebrafish: A large population of presumptive amacrine cells was labeled at the base of the INL, and the IPL was positive for GABA, as were occasional cells in the ganglion cell layer. Horizontal cells, particularly at the retinal margins, were also GABA positive beginning at about 3 days postfertilization. The transient expression of GABA in retinal ganglion cells and their axons during the period when synaptic contacts are being established both within the retina and between the retina and central targets suggests that GABA may have a role in the development of this system, in addition to serving as a classical neurotransmitter. © 1994 Wiley‐Liss,

ISSN:0092-7317    

DOI:10.1002/cne.903450409

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractGamma‐aminobutyric acid (GABA) plasma membrane transporters influence synaptic transmission by high‐affinity, Na+‐dependent transport processes. The cDNA clone, GAT‐1, encodes a high‐affinity Na+‐ and Cl−‐dependent GABA plasma membrane transporter, which has kinetic and pharmacological properties similar to those of high‐affinity GABA uptake systems associated with neurons. The present study evaluates the distribution and cellular localization of this putative neuronal GABA transporter by RNA blot hybridization and in situ hybridization histochemistry in the rat retina. Northern blot hybridization analysis of total retinal and cerebellar RNA extracts demonstrated a single band of hybridization at 4.2 kilobases. GABA transporter mRNA is expressed by numerous cells that are distributed to the proximal inner nuclear layer and the ganglion cell layer and by a few cells located in the inner plexiform layer. Double label studies combining the retrograde transport of the fluorescent dye Fluorogold from the superior colliculus to identify ganglion cells and in situ hybridization histochemistry demonstrated that most GAT‐1 mRNA‐containing cells in the ganglion cell layer are displaced amacrine cells, although some ganglion cells containing GAT‐1 mRNA were visualized. In freshly dissociated retinal cell preparations, the GAT‐1 RNA signal is strong in neurons and weak to moderate in specialized glial cells called Müller cells. Müller cells were identified by both their morphology and the presence of the selective Müller cell marker cellular retinaldehyde‐binding protein. Only background labeling is seen with the sense GAT‐1 RNA probe in both tissue sections and dissociated retinal cell preparations. These findings demonstrate that GAT‐1 mRNA is expressed in both the retina and brain. In the retina, this transporter is predominantly localized to amacrine, displaced amacrine and interplexiform cells, and some ganglion cells. This transporter mRNA is also expressed by Müller cells but at a lower level than by neurons. These observations indicate that GABA transport by GAT‐1 plasma membrane transporters in the retina is mediated by both neurons a

ISSN:0092-7317    

DOI:10.1002/cne.903450410

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe ventral nerve cord of crayfish contains axons of five pairs of excitatory interneurons, each of which can activate the swimmeret system. Perfusion of the ventral nerve cord with the neuropeptide proctolin also activates the swimmeret system. The experiments reported here were conducted to test the hypothesis that one or more of these excitatory interneurons uses proctolin as a transmitter.Each of the five excitatory axons was located and stimulated separately in an individual crayfish, and similar motor activity was elicited by stimulating each of them. Quantitative comparison of spontaneous swimmeret motor patterns with activity caused by stimulating one of these excitatory axons, EC, or by perfusing with proctolin solutions showed that the motor patterns produced under these three conditions were not significantly different (P>0.05).By using a new, affinity‐purified proctolin antiserum, we labeled axons in the connective tissue between the last thoracic and first abdominal ganglion and compared the positions of labeled axons with the previously described positions of the excitatory axons. About 0.3% of the axons in these connective tissues showed proctolin‐like immunoreactivity, but heavily labeled pairs of axons did occur bilaterally in the regions of excitatory swimmeret axons. The projections of these labeled axons into the abdominal ganglia were traced in serial plastic sections. Labeled processes were abundant in the lateral neuropils, the loci of the swimmeret pattern‐generating circuitry.From this evidence, we propose that three of these excitatory swimmeret interneurons use proctolin as a transmitter, but that a fourth does not. The evidence for the fifth axon is ambiguous. © 1994 Wiley‐L

ISSN:0092-7317    

DOI:10.1002/cne.903450411

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY