bluuebunny/crossref_metadata_2025_split huggingface dataset:
Expression of the Cyclic AMP‐dependent Protein Kinase (PKA) Catalytic Subunit from a Herpes Simplex Virus Vector Extends the Survival of Rat Sympathetic Neurons in the Absence of NGF
Authors: Buckmaster E. Anne , Tolkovsky Aviva M. 
Published: April 2006

AbstractSuperior cervical ganglion neurons from neonatal rats are dependent on nerve growth factor for their survival both in vivo and in vitro. In culture this requirement can be largely replaced by cAMP or its analogues. Since activation of protein kinase A by cAMP is likely to be the pathway by which it exerts its survival‐promoting effect, we have tested the feasibility of using herpes simplex virus (HSV) as a vector for expressing survival‐promoting genes in neurons by cloning the catalytic subunit of the CAMP‐dependent protein kinase (PKAcat) with a metallothionein gene promoter into the HSV thymidine kinase gene by homologous recombination. About 95% of the neurons became infected using 2.5 p.f.u. per cell. When this construct was used to express PKAcat in superior cervical ganglion neurons, in the presence of nerve growth factor (NGF) increases of 1.9‐ to 2.4‐fold in PKA activity were found 8–10 h after infection; levels remained elevated (1.4‐ to 2.1‐fold) up to 18 h, returning to basal by 24 h. After infection in the absence of NGF, cumulative activity over 24 h was ∼3.5‐fold lower in the first 24 h. Although the level of the inhibitory regulatory subunit type I was raised by 18 h, this is unlikely to completely explain the transient activity of PKAcat. When neurons were induced to express maximum PKAcat levels in the presence of NGF and then deprived of NGF, survival was extended by up to 2 days, demonstrating a direct role for PKA in promoting survival. By this time, some neurite degeneration was beginning which appeared to be partly due to toxic effects of the virus. However, replenishment with NGF supported further survival, showing that at this time the neurons were still viable. Similar rates of survival were obtained using a tsK‐based PKAcat vector, but no significant survival was obtained with parental HSV or tsK virus strains. These data demonstrate the feasibility, and highlight some of the problems, of using HSV‐based vectors as tools for expressing functional survival proteins in sympathetic neurons.
Intracellular Messengers Contributing to Persistent Nociception and Hyperalgesia Induced by L‐Glutamate and Substance P in the Rat Formalin Pain Model
Authors: Coderre Terence J. , Yashpal Kiran 
Published: April 2006

AbstractThe contribution of the intracellular messengers nitric oxide, arachidonic acid and protein kinase C to persistent nociception in response to tissue injury in rats was examined following the subcutaneous injection of formalin into the hindpaw. Formalin injury‐induced nociceptive behaviours were reduced by intrathecal pretreatment with inhibitors of nitric oxide synthase (NG‐nitro‐L‐arginine methyl ester, L‐NAME), arachidonic acid (dexamethasone) or protein kinase C [protein kinase C (19–26) and 1–95‐(isoquinolinesulphonyl)‐2‐methylpiperazine dihydrochloride, H‐7]. Each of these agents affected the tonic, but not the acute, phase of the formalin response. Furthermore, none of these agents affected mechanical or thermal flexion reflex thresholds in rats not injected with formalin. Conversely, formalin‐induced nociceptive responses were enhanced by stimulators of nitric oxide (sodium nitroprusside), arachidonic acid metabolism (arachidonic acid) or protein kinase C [(±)‐1‐oleoyl‐2‐acetyl‐glycerol], and were slightly reduced by inositol trisphosphate. Mechanical flexion reflexes were also reduced by arachidonic acid, while thermal flexion reflexes were reduced after treatment with sodium nitroprusside, arachidonic acid or [(±)‐1 ‐oleoyl‐2‐acetyl‐glycerol]. The enhancement of formalin nociceptive behaviours (hyperalgesia) in rats treated with L‐glutamate or substance P was reversed by pretreatment with inhibitors of nitric oxide (L‐NAME), arachidonic acid (dexamethasone) or protein kinase C (H‐7). The results suggest that central sensitization and persistent nociception following formalin‐induced tissue injury, and the hyperalgesia in the formalin test induced by L‐glutamate and substance P, are dependent on the intracellular messengers nitric oxide, arachidonic acid and protein kinase C.
Prefrontal Corticostriatal Afferents Maintain Increased Enkephalin Gene Expression in the Dopamine‐denervated Rat Striatum
Authors: Campbell Kenneth , Björklund Anders 
Published: April 2006

AbstractThe cortical contribution to the maintenance of preproenkephalin (PPE) and preprotachykinin (PPT) mRNA levels in the rat striatum was investigated using quantitative in situ hybridization histochemistry. The effects of knifecut transections of the frontal cortical pole on the expression of PPE and PPT mRNA in rat striatal neurons was studied in intact striata and in striata previously denervated by a bhydroxydopamine (6‐OHDA) lesion of the mesencephalic dopamine pathways. Lesions of the dopaminergic striatal afferents resulted in marked increases in the mRNA encoding PPE throughout the striatum, including the ventral striatum and nucleus accumbens, while the levels of PPT mRNA were considerably reduced in these structures. Knife‐cut lesions of the frontal cortical pole, transecting the prefrontal corticostriatal projection at the level of the foreceps minor, displayed little or no effect on the expression of either PPE or PPT mRNA in the dopamineintact striatum. Conversely, frontal cortical transections performed 4 weeks after the 6‐OHDA lesions reversed the 6‐OHDA‐lesion‐induced increase in PPE mRNA in the striatum as well as in the ventral striaturn and nucleus accumbens. The down‐regulation of PPE mRNA in the dopaminergically denervated striatum was most pronounced in the medial part, which is the area most densely innervated by the frontal cortical pole. Here, the level of PPE mRNA expression per striatal cell was similar to the intact striatum. In contrast, the cellular expression of PPE mRNA remained up‐regulated in the lateral striatum, which receives more sparse innervation from the frontal cortical pole. Cortical transections did not significantly affect the 6‐OHDA‐lesion‐induced down‐regulation of PPT mRNA in any of the striatal regions analysed. The present results demonstrate that knifecut transections of the frontal corticostriatal pathway are capable of reversing the increased striatal PPE mRNA levels, but not the decreased PPT mRNA levels, induced by a 6‐OHDA lesion of the dopaminergic input. These observations suggest that in the absence of a functional striatal dopamine input, augmented glutamatergic transmission in corticostriatal afferents is necessary to maintain increased levels of PPE mRNA expression, and hence also enkephalin synthesis, in striatal projection neurons.
The Nitric Oxide ‐ Cyclic GMP Pathway and Synaptic Depression in Rat Hippocampal Slices
Authors: Boulton Caroline L. , Irving Andy J. , Southam Eric , Potier Brigitte , Garthwaite John , Collingridge Graham L. 
Published: April 2006

AbstractThe ability of exogenous nitric oxide (NO) to modify synaptic transmission was investigated in area CA1 of the rat hippocampal slice. The NO donors S‐nitroso‐N‐acetylpenicillamine (SNAP) and S‐nitrosoglutathione (SNOG) depressed field excitatory postsynaptic potentials evoked by low frequency stimulation of the Schaffer collateral ‐ commissural pathway. Upon washout of the NO donors, synaptic transmission rapidly returned to control levels. A similar reversible synaptic depression was produced by SNAP when tetanic stimulation (100 Hz; 1 s) was delivered in its presence. The effect of SNAP was not mimicked by its precursor or breakdown product and was blocked by haemoglobin, indicating that the effect involved NO. Roussin's black salt, a photolabile NO donor, also depressed transiently field excitatory postsynaptic potentials following photolysis. The depression was induced rapidly following a flash of UV light (20 s duration) focused onto the slice using a confocal microscope. The depressant effect of the NO donors on synaptic transmission was mimicked by zaprinast, a specific cGMP ‐ phosphodiesterase inhibitor. Zaprinast depressed to a similar extent both the α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole propionate and N‐methyl‐d‐aspartate receptor‐mediated components of excitatory postsynaptic currents without affecting passive membrane properties, indicating a presynaptic locus of action. SNAP, SNOG and zaprinast all elevated cGMP levels in rat hippocampal slices. Immunocytochemical staining revealed that the cGMP accumulation was mainly in a network of varicose fibres running throughout the CA1 region, consistent with a presynaptic site of action of NO. We conclude that NO, possibly through activation of guanylate cyclase, may be involved in transient presynaptic depression in the CA1 region of the hippocampus.
Plasticity of NMDA Receptor Expression During Mouse Cerebellar Granule Cell Development
Authors: Didier Michel , Mienville Jean‐Marc , Soubrié Philippe , Bockaert Joël , Berman Stephen , Bursztajn Sherry , Pin Jean‐Philippe 
Published: April 2006

AbstractA period of hypersensitivity to N‐methyl‐d‐aspartate (NMDA) has been described during the early development of different types of neuron. Since activation of NMDA receptors can also induce rapid neuron death, the hypersensitivity to NMDA may be tightly controlled. In the present study we show that mouse cerebellar granule neurons become transiently hypersensitive to NMDA between days 10 and 14 after plating in a culture medium containing 30 mM K+. The NMDA sensitivity is higher when cells are cultured in the presence of an NMDA receptor antagonist [30 mM K+ plus 100 μM 3‐((±)‐2‐carboxypiperazine‐4‐yl)‐propyl‐1‐phosphonic acid (CPP)], and no hypersensitivity is observed when cells are cultured in the continuous presence of NMDA (12.5 mM K+ plus 100 μM NMDA). The high NMDA sensitivity in control cells is associated with a higher density of NMDA receptors than that measured in NMDA‐treated cells, suggesting that the sensitivity to NMDA may be partly controlled by activity‐dependent NMDA receptor down‐regulation. We also examined the level of NMDA‐ζ1 mRNA and found no correlation between this parameter and the transient pattern of NMDA sensitivity. Such NMDA receptor plasticity may be of importance in the central nervous system, protecting developing cells from excitotoxicity at critical developmental stages.
Glycinergic Inhibitory Synaptic Currents and Related Receptor Channels in the Zebrafish Brain
Authors: Legendre P. , Korn H. 
Published: April 2006

AbstractTo extend our study of the inhibitory synaptic network we have developed an isolated whole‐brain preparation of the 52‐h‐old zebrafish(Brachydanio redo)in which the structural and functional integrity of the brain is preserved. We report the characterization of quantal inhibitory events and the correlation of their properties with those of the underlying activated channels. During whole‐cell recordings of the Mauthner cells, applications of 10−6M tetrodotoxin greatly reduced the frequency and amplitude of the spontaneously occurring synaptic events, which were dominated by Cl−‐dependent inhibitory postsynaptic currents (IPSCs). Lowering Ca2+and adding Mg2+to tetrodotoxin‐containing solutions resulted in a further decrease in amplitude of the recorded synaptic currents, the remaining ones being considered as miniature IPSCs (mISCs). Applications of 0.5–1 μMM strychnine in the presence of tetrodotoxin eliminated > 90% of the inhibitory currents in the preparation. The amplitude histograms of these mIPSCs exhibited two initial equally spaced peaks, followed by a skewed distribution for higher values. The first two components were well fitted by the sum of two Gaussian curves, giving a mean quantal amplitude of 35.7 pA (at a holding potential of‐50 mV) and a coefficient of variation of 0.25 for the first peak. Outside‐out recordings showed at least two classes of glycine receptor channels, one having multiple conductance levels with a main state of 81–86 pS and another displaying only one opening level of 41–43 pS. These two mean conductance states had similar mean open times, of 0.6–1 and 4.5–6 ms respectively. In addition, three mean closed times were observed for the 41–43 pS level. The shortest group (0.6–1 ms) was considered as representing gaps within bursts. Burst analysis revealed three mean burst durations, of 0.6, 4 and 35 ms. Comparisons of the amplitude of the first class of mIPSCs and of the open channel conductances indicated that one quantum opens 14–22 channels. Moreover, the correspondence between the mean decay time of mIPSCs and the mean open time or medium burst duration (4–5 ms) suggests that glycine‐activated channels open only once in response to a single exocytosis. The pre‐and postsynaptic origins of mIPSCs amplitude fluctuations are discussed in the context of multivesicular release versus the hypothesis of postsynaptic receptor saturation.
Dynamic Changes in the Composition of the AP‐1 Transcription Factor DNA‐binding Activity in Rat Brain Following Kainate‐induced Seizures and Cell Death
Authors: Kaminska Bozena , Filipkowski Robert K. , Zurkowska Grazyna , Lason Wladyslaw , Przewlocki Ryszard , Kaczmarek Leszek 
Published: April 2006

AbstractKainate, a potent excitatory and neurotoxic agent, has also proved useful in studies on other glutamate‐driven phenomena, such as neuronal plasticity. Long‐term effects of kainate are apparently dependent on its influence on the expression of various genes, including those encoding the AP‐1 transcription factor, consisting of proteins belonging to the Fos and Jun families. In our studies we analysed c‐fos, fos B, c‐jun, jun B and jun D mRNA levels as well as a functional feature of AP‐1, its DNA‐binding activity, in the rat brain following systemic injection of kainate. Two phases of elevated AP‐1 DNA‐binding activity were observed in the hippocampus and entorhinal cortex, and were correlated with period of seizures (2 and 6 h after kainate injection) and neuron damage (48–72 h). At 72 h after kainate treatment DNA fragmentation, believed to be diagnostic of apoptotic processes typical of programmed cell death phenomena, was noted. Two and six hours after the treatment, AP‐1 consisted predominantly of Fos B, c‐Fos, Fra‐2 and Jun B, while at 72 h Jun D constituted the major AP‐1 component in place of Jun B, and no c‐Fos was detected. Only a slight AP‐1 increase was seen 24 h after kainate treatment. In the sensory cortex, only the late phase of AP‐1 elevation was detected. Contrary to AP‐1, no effect of kainate on levels of two other transcription factors, CREB/ATF (cAMP‐responsive element binding proteins) and OCT (octamer element DNA‐binding activity) was seen. However, the level of OCT DNA‐binding activity was higher in the sensory cortex than in other two structures examined. These data point to a selective effect of kainate on AP‐1 in brain structures known to be particularly vulnerable to kainate, and suggest a role of AP‐1 transcription factor, and more selectively Jun D protein, in kainate‐driven programmed neuronal death.
The Survival of Transected Axonal Segments of Cultured Aplysia Neurons is Prolonged by Contact with Intact Nerve Cells
Authors: Benbassat Dorit , Spira Micha E. 
Published: April 2006

AbstractAxonal segments transected from their cell body in vivo commonly undergo degeneration within 3–4 days (Wallerian degeneration). In lower vertebrates and invertebrates, however, some transected axonal segments survive for long periods ranging between 30 and 200 days. To circumvent the technical complications of studying the mechanisms underlying long‐term survival of transected axons in vivo, we developed an in vitro system. We found previously that isolated axonal segments of cultured Aplysia neurons preserved their morphological integrity for an average duration of 7.6 days (range 2–14 days) and maintain their passive and excitable membrane properties. This survival occurred in the absence of de novo protein synthesis. In the present study we examined the influence of homologous neurons on the survival of transected axonal segments. We found that the average survival time of transected axons was doubled when co‐cultured in physical contact with intact homologous neurons (average 15.3 days, range 2–27 days). During this period, the transected axons extended neurites, maintained normal passive and excitable membrane properties, formed electrotonic junctions with the intact neurons and maintained normal free intracellular Ca2+ levels. Consistent with these observations, electron micrographs of the transected axon revealed that the cytoskeletal elements of the axon appeared normal even 20 days after transection. In contrast, the mitochondria and smooth endoplasmic reticulum appeared damaged. As the prolonged survival was conditional on physical contact between the transected axon and the surrounding intact neurons, we suggest that the prolongation of survival time is promoted by the direct transfer of material from the intact neurons to the transected axon. However, co‐culture of transected axons with homologous neurons did not fully mimic in vivo conditions, in which transected axons can survive for several months.
Inhibition of Posttraumatic Microglial Proliferation in a Genetic Model of Macrophage Colony‐Stimulating Factor Deficiency in the Mouse
Authors: Raivich Gennadij , Moreno‐Flores M. Teresa , Möller J. Carsten , Kreutzberg Georg W. 
Published: April 2006

AbstractActivation and proliferation of microglia are common cellular hallmarks in many different pathological processes of the central nervous system. Although a number of colony‐stimulating factors enhance microglial proliferation in vitro, little is known about the endogenous mitogens. In the present study we show a strong and selective inhibition of microglial proliferation in the facial nucleus of osteopetrotic (op/op) mice, with a genetic deficiency in biologically active macrophage colony‐stimulating factor (MCSF). Posttraumatic activation of adjacent axotomized neurons and reactive astrocytes was not affected, emphasizing the specificity of MCSF as a microglial growth factor.
Relationship Between Lateral Inhibitory Connections and the Topography of the Orientation Map in Cat Visual Cortex
Authors: Kisvárday Zoltán F. , Kim Dae‐Shik , Eysel Ulf T. , Bonhoeffer Tobias 
Published: April 2006

AbstractThe functional and structural topography of lateral inhibitory connections was investigated in visual cortical area 18 using a combination of optical imaging and anatomical tracing techniques in the same tissue. Orientation maps were obtained by recording intrinsic signals in regions of 8.4–19 mm2. To reveal the inhibitory connections provided by large basket cells, biocytin was iontophoretically injected at identified orientation sites guided by the pattern of surface blood vessels. The axonal and dendritic fields of two retrogradely labelled large basket cells were reconstructed in layer III. Their axonal fields extended up to 1360 μm from the parent somata. In addition to single basket cells, the population of labelled basket cell axons was also studied. For this analysis anterogradely labelled basket axons running horizontally over 460–1280 μm from the core of an injection site in layer III were taken into account. The distribution of large basket cell terminals according to orientation preferences of their target regions was quantitatively assessed. Using the same spatial resolution as the orientation map, a frequency distribution of basket cell terminals dependent on orientation specificity could be derived. For individual basket cells, the results showed that, on average, 43% of the terminals provided input to sites showing similar orientation preferences (±30°) to those of the parent somata. About 35% of the terminals were directed to sites representing oblique‐orientation [±(30–60)°], and 22% of them terminated at cross‐orientation sites [±(60–90)°]. Furthermore, the possible impact of large basket cells on target cells at different distances and orientation preferences was estimated by comparing the occurrence of orientation preferences with the occurrence of basket terminals on the distance scale. It was found that a basket cell could elicit iso‐orientation inhibition with a high impact between 100–400 and 800–1200 μm strong cross‐orientation inhibition at ∼400–800 μm, and oblique‐orientation inhibition between 300–500 and 700–900 μm from the parent soma. The non‐isotropic topography of large basket axons suggests a complex function for this cell class, possibly including inhibition related to orientation and direction selectivity depending on the location of the target cells and possible target selectivity.
Neurotrophin‐4/5 Promotes Survival and Differentiation of Rat Striatal Neurons Developing in Culture
Authors: Widmer Hans R. , Hefti Franz 
Published: April 2006

AbstractCultures of dissociated striatal neurons from fetal rats were prepared, and were grown in the presence of neurotrophin‐4/5 (NT‐4/5) as well as the other known neurotrophins, nerve growth factor (NGF), brain‐derived neurotrophic factor (BDNF) and neurotrophin‐3 (NT‐3). We found that acute administration of NT‐4/5 to 7‐day‐old cultures stimulates the hydrolysis of phosphatidylinositol, an event involved in neurotrophin signal transduction. Growth of striatal cultures in the presence of NT‐4/5 resulted in increased cell survival, as indicated by elevations in cell number, protein content, and a measure of mitochondrial enzyme activity (MTT assay). NT‐4/5 increased GABA uptake and staining intensity in these cultures, as indicated by GABA immunocytochemistry, indicating a trophic action on GABAergic neurons, the predominant neuron type in the striatum. To further identify responsive cell populations we analysed for calretinin, a calcium‐binding protein known to colocalize with GABA in a number of neuronal cells. In cultures prepared from rats of embryonic day 15, NT‐4/5 strongly increased the number of calretinin‐positive cells as well as calretinin levels, as determined by Western blot analysis. When the cultures were prepared from embryonic day 18 rats, NT‐4/5 very strongly increased the morphological differentiation of calretinin‐positive cells, whereas the increase in cell number was less prominent. All effects produced by NT‐4/5 were mimicked by BDNF with similar potency. NT‐3 was less effective than NT‐4/5 and BDNF, and its effects were limited to cultures prepared from embryonic day 15 rats, suggesting a role in the regulation of cell survival at early developmental stages. NGF did not affect any of the measured parameters. Our findings identify NT‐4/5 as potent neurotrophic factor for striatal neurons, able to promote their survival and differentiation.
Does Practice in Orientation Discrimination Lead to Changes in the Response Properties of Macaque Inferior Temporal Neurons?
Authors: Vogels Rufin , Orban Guy A. 
Published: April 2006

AbstractWe trained two rhesus monkeys in a task in which they had to judge whether or not two successively presented gratings differed in orientation. In a first experiment, we trained a monkey for only a restricted set of orientations and then recorded from the temporal cortical visual area (TE) while he made discriminations at trained and untrained orientations. Although this orientation‐selective practice induced a marked anisotropy in his behavioural performance, this was not matched by a similar anisotropy in single‐cell response properties. In a second experiment, we compared the response properties of TE cells in two monkeys before and after practice in the discrimination of small orientation differences. The training had no effect on either the responsiveness or the orientation tuning. We did, however, observe alterations in the pattern of response modulations induced by the behavioural context. However, these changes with practice, although present in both monkeys, were not consistent from animal to animal. The relevance of these findings for the functional significance of behavioural context dependencies of TE cells, as well as for the plasticity of TE responses, is discussed.