bluuebunny/crossref_metadata_2025 huggingface dataset:
The SP1 Antigen in Subplate Neurons of the Developing Cat Cortex is an Immunoglobulin‐like Molecule
Authors: Henschel Reinhard , Wahle Petra
Published: April 2006

Monoclonal antibody subplate‐l (mAb SP1) specifically stains somata, dendrites and axons of spiny inverted pyramidal neurons in the subplate zone in the early postnatal kitten neocortex. The SP1 antigen has been previously identified as a cytosolic protein of apparent molecular weight 56 kDa. We have now employed immune‐affinity chromatography to further characterize this antigen. An antigen with SP1‐like immunoreactivity (ir) is present in various organs, and is particularly enriched in blood plasma. Exsanguination of the organs prior to protein extraction reduces the SP1‐ir band dramatically, indicative of a blood‐borne molecule. The 56 kDa SP1‐ir antigen was purified from plasma by affinity chromatography and subjected to Edman degradation. The first 20 N‐terminal amino acids show 80% homology to the N‐terminus of immunoglobulin heavy chain of man, the mouse and the dog. If the 56 kDa SP1‐ir antigen in plasma is an immunoglobulin, and if an immunoglobulin‐like molecule is present in the subplate, then antisera against cat immunoglobulins should stain subplate neurons. A polyclonal antiserum against cat IgG intensely stains the somata and dendrites of subplate neurons. On protein blots, this antiserum recognizes the 56 kDa band, and an additional band of ∼27 kDa, corresponding in size to immunoglobulin light chains. Preabsorbing mAb SP1 with cat immunoglobulin G abolishes the immunoreactivity in sections of kitten cortex. Further, it dramatically reduces the reactivity on protein blots. The results suggest that the 56 kDa SP1‐ir antigen in cortical subplate neurons belongs to the immunoglobulin superfamily.
Pharmacology and Biophysical Properties of α7 and α7 ‐ α8 α‐Bungarotoxin Receptor Subtypes Immunopurified from the Chick Optic Lobe
Authors: Gotti C. , Hanke W. , Maury K. , Moretti M. , Ballivet M. , Clementi F. , Bertrand D.
Published: April 2006

Two chick optic lobe α‐bungarotoxin receptor subtypes (α7 and α7 ‐ α8) were immunopurified using polyclonal antibodies raised against synthetic peptides of chick α7 and α8 α‐bungarotoxin receptor subunits. The α7 subtype contained the Mr 57 000 α7 subunit, and represented 60 ‐ 70% of the α‐bungarotoxin receptors; the α7‐α8 subtype contained the Mr 57 000 α7 and α8 subunits, and represented only 20 ‐ 25% of the receptors. Both subtypes also had an additional Mr 52 000 subunit. The affinity of these subtypes for α‐bungarotoxin as well as antagonists was similar. However, the α7 ‐ α8 subtype displayed consistently higher affinities for agonists. When reconstituted in planar lipid bilayers, the α7 ‐ α8 subtype displayed several conductance states of 10 ‐ 50 pS; the α7 subtype had only one conductance state of 45 pS. The α7 ‐α8 subtype was activated by lower agonist concentrations than the α7 subtype. When expressed in Xenopus oocytes, the α8 subunit formed functional homomeric receptors that desensitized rapidly. These channels were blocked by α‐bungarotoxin and displayed a higher affinity for agonists than the α7 homomeric receptor. Taken together, these data indicate that at least two α‐bungarotoxin subtypes are present in the chick optic lobe. They operate as ligand‐gated channels and display different agonist sensitivities and kinetics/conductance properties.
Eye Saccade Dynamics During Paradoxical Sleep in the Cat
Authors: Vanni‐Mercier G. , Pelisson D. , Goffart L. , Sakai K. , Jouvet M.
Published: April 2006

Cat eye movements were recorded during wakefulness and paradoxical sleep with the technique of the scleral search coil in a magnetic field. During waking, eye movements consisted of a succession of saccades and fixation phases. During paradoxical sleep, the pattern of eye movements displayed drifts of variable velocity and direction and short fixation phases, upon which saccades superimposed. These saccades displayed a repetitive, stereotyped, asymmetrical pattern. The maximum velocity/amplitude relationships, i.e. the main sequences, were determined for spontaneous and visually induced saccades of waking and for the following types of saccades during paradoxical sleep: (i) isolated saccades accompanied by ponto‐geniculo‐occipital (PGO) waves, (ii) isolated saccades accompanied by eye movement potentials (EMP), and (iii) saccades in bursts accompanied by PGO waves. The slope of the main sequence relationship of any type of paradoxical sleep saccade (from 21.7°/° for isolated saccades to 35.6°/s° for saccades in bursts) was higher than that of any type of waking saccade (11.2°/s° for spontaneous saccades to 14.7°/s° for visually elicited ones). Furthermore, during paradoxical sleep, saccades in bursts were faster than isolated ones. This demonstrates that different neurophysiological mechanisms subserve the generation of waking saccades, paradoxical sleep isolated saccades and paradoxical sleep saccades in bursts, or that the oculomotor system is in a different state of excitation during these different sets of saccades. These findings throw new light on the functioning of the oculomotor system during paradoxical sleep and are discussed in terms of the functional significance of paradoxical sleep saccades and PGO waves.
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

Superior 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

The 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

The 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

The 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

A 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

To 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

Kainate, 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

Axonal 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

Activation 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

The 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

Cultures 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

We 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.
Low Doses of the Glycine/NMDA Receptor Antagonist R‐(+)‐HA‐966 but not d‐Cycloserine Induce Paroxysmal Activity in Limbic Brain Regions of Kindled Rats
Authors: Wlaź Piotr , Ebert Ulrich , Löscher Wolfgang
Published: April 2006

(+)‐HA‐966 [R‐(+)‐3‐amino‐1‐hydroxypyrrolid‐2‐one], a functional antagonist at the glycine modulatory site on the W‐methyl‐D‐aspartate (NMDA) receptor/ion channel complex, was evaluated in amygdala‐kindled rats, a model of epilepsy recently shown to exhibit enhanced susceptibility to the adverse effects of competitive and non‐competitive NMDA receptor antagonists. Since (+)‐HA‐966 displays weak partial agonistic effects at the glycine site (−10% efficacy of glycine), D‐cycloserine, a glycine ligand with much higher intrinsic activity, was evaluated in kindled rats for comparison. Following drug administration, electrographic activity was recorded from the basolateral amygdala (i.e. the focal site) as well as the ipsilateral piriform cortex, ventral hippocampus and nucleus accumbens. In addition to the evaluation of original recordings, power spectrum analysis was used to delineate drug effects. (+)‐HA‐966 (20–40 mg/kg i.p.) induced marked alterations in electrographic recordings, including increases in amplitude and isolated spiking, i.e. signs of paroxysmal activity. The severity or duration of fully kindled seizures was not changed by (+)‐HA‐966, but the drug dramatically increased the duration of immobilization and limbic seizure activity following a kindled motor seizure. In contrast to (+)‐HA‐966, D‐cycloserine did not induce any electrographic changes, even when administered in much higher doses than (+)‐HA‐966. The changes in electrographic recordings seen after administration of (+)‐HA‐966 in kindled rats were almost absent in non‐kindled rats, indicating that kindling had increased the sensitivity to the paroxysmal effects of the glycine/NMDA receptor ligand. The data indicate that functional glycine/NMDA antagonists with low intrinsic efficacy may bear the risk of proconvulsant activity.
Differential Effects of Serotonin and Raphe Grafts in the Hippocampus and Hypothalamus: A Combined Behavioural and Anatomical Study in the Rat
Authors: Richter‐Levin G. , Acsády L. , Freund T. F. , Segal M.
Published: April 2006

Combined with a partial cholinergic deficiency, serotonergic lesions induce severe spatial learning deficits. Serotonergic lesions, however, have additional effects, such as reduced body weight and disruption of thermoregulation, which may be the cause of the observed learning deficits. Restoration of the serotonergic innervation of the hippocampus by raphe grafts reduces these learning deficits. The effects of the grafts may result from a direct support of spatial learning but may also be an indirect result of preventing some of the other effects of serotonergic lesions. In the present study we used raphe grafts to examine the selectivity and specificity of the effects of serotonergic lesions in the rat, and used the behavioural effects as an indication of successful transplantation in order to examine the fine details of such grafts. Raphe grafts in the hippocampus did not prevent the effects of the lesions on body weight, thermoregulation and exploratory behaviour but did minimize the effects of the lesions on spatial learning. In contrast, raphe grafts in the hypothalamus reduced the effects of the lesions on thermoregulation but failed to support learning. The grafted fibres showed termination specificity with the interneurons, which is typical of the serotonergic innervation of the normal hippocampus. The results indicate that the serotonergic innervation of the hippocampus functions locally to support spatial learning. This role of serotonin is independent of its involvement in modulation of body weight, thermoregulation or exploratory behaviour. The results confirm that the modes of serotonergic action in the hippocampus include the selective innervation of specific interneuron subpopulations.
HIV‐1 Envelope Protein gp120 Potentiates NMDA‐evoked Noradrenaline Release by a Direct Action at Rat Hippocampal and Cortical Noradrenergic Nerve Endings
Authors: Pittaluga A. , Raiteri M.
Published: April 2006

Exposure of rat or human neocortical or hippocampal tissue to glutamate receptor agonists elicits a Ca2+‐dependent, exocytotic‐like release of previously accumulated [3H]noradrenaline through activation of both N‐methyl‐d‐aspartate (NMDA) and α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA) receptors colocalized on the noradrenergic axon terminals. Here we show that the NMDA (100 μM)‐evoked release of [3H]noradrenaline from superfused thin layers of isolated rat hippocampal or cortical nerve endings was potentiated when the human immunodeficiency virus type 1 coat protein gp120 was added to the superfusion medium concomitantly with NMDA. The effect of gp120 (10 pM to 3 nM) on the 100 μM NMDA‐evoked release of [3H]noradrenaline was concentration‐dependent; the maximal effect (‐140% potentiation) was reached at 100 pM of gp120. The protein was inactive on its own. The [3H]noradrenaline release evoked by NMDA (100 μM) + gp120 (100 μM) was prevented by classical NMDA receptor antagonists, as well as by 10 μM memantine. Neither the release evoked by NMDA nor that elicited by NMDA + gp120 was sensitive to the nitric oxide synthase inhibitor NG ‐nitro‐l‐arginine, suggesting no involvement of nitric oxide. The [3H]noradrenaline release elicited by 100 nM AMPA was unaffected by gp120. The protein potentiated the release evoked by 100 nM glutamate; the effect of 100 pM gp120 was quantitatively identical to that of 1 μM glycine, with no apparent additivity between gp120 and glycine. The antagonism by 1 μM 7‐chloro‐kynurenic acid of the NMDA‐induced [3H]noradrenaline release was reversed by glycine or gp120. The data are compatible with gp120 acting directly as a powerful positive allosteric modulator at a neuronal NMDA receptor.
Differential Expression of Synaptophysin and Synaptoporin During Pre‐ and Postnatal Development of the Rat Hippocampal Network
Authors: Grabs D. , Bergmann M. , Schuster Th. , Fox P. A. , Brich M. , Gratzl M.
Published: April 2006

The closely related synaptic vesicle membrane proteins synaptophysin and synaptoporin are abundant in the hippocampal formation of the adult rat. But the prenatal hippocampal formation contains only synaptophysin, which is first detected at embryonic day 17 (E17) in perikarya and axons of the pyramidal neurons. At E21 synaptophysin immunoreactivity extends into the apical dendrites of these cells and in newly formed terminals contacting these dendrites. The transient presence of synaptophysin in axons and dendrites suggests a functional involvement of synaptophysin in fibre outgrowth of developing pyramidal neurons. Synaptoporin expression parallels the formation of dentate granule cell synaptic contacts with pyramidal neurons: the amount of hippocampal synaptoporin, determined in immunoblots and by synaptoporin immunostaining of developing mossy fibre terminals, increases during the first postnatal week. Moreover, in the adult, synaptoporin is found exclusively in the mossy fibre terminals present in the hilar region of the dentate gyrus and the regio inferior of the cornu ammonis. In contrast, synaptophysin is present in all synaptic fields of the hippocampal formation, including the mossy fibre terminals, where it colocalizes with synaptoporin in the same boutons. Our data indicate that granule neuron terminals differ from all other terminals of the hippocampal formation by the presence of both synaptoporin and synaptophysin. This difference, observed in the earliest synaptic contacts in the postnatal hippocampus and persisting into adult life, suggests distinct functions of synaptoporin in these nerve terminals.
Role of Dopamine in the Plasticity of Glutamic Acid Decarboxylase Messenger RNA in the Rat Frontal Cortex and the Nucleus Accumbens
Authors: Rétaux Sylvie , Trovero Fabrice , Besson Marie‐Jo
Published: April 2006

The modulatory role of dopamine (DA) on the expression of mRNA encoding the large isoform of glutamic acid decarboxylase (GAD67), the biosynthesis enzyme of gamma aminobutyric acid (GABA), was examined in GABA neurons of two structures innervated by DA neurons originating from the ventral tegmental area (VTA): the medial frontal cortex (MFC) and the nucleus accumbens (NAcc). A bilateral electrolytic lesion of VTA was performed in rats to produce a DA denervation of both the MFC and NAcc. The efficacy of VTA lesions was verified by measurement of locomotor activity and by immunohistochemical detection of tyrosine hydroxylase in the mesencephalon. GAD67 mRNA was detected by in situ hybridization histochemistry using a 35S‐labelled cDNA probe. Densitometric analysis of GAD67 mRNA hybridization signals revealed in VTA‐lesioned rats a significant decrease (‐24%) in GAD67 mRNA levels in the prelimbic area of the MFC and no significant effect in the anterior cingulate area or the frontoparietal cortex. Single cell analyses by computer‐assisted grain counting showed that the decrease in GAD67 mRNA levels in prelimbic MFC was due to a change in GAD67 mRNA expression in a subpopulation of GABA interneurons located in the deep cortical layers (V‐VI). By contrast, in the NAcc of VTA‐lesioned rats, GAD67 mRNA levels were significantly increased in the anterior part and in the core but were unchanged in the shell part. These results suggest that in two target structures of VTA DA neurons, GAD67 mRNA expression is, in normal conditions, under a tonic stimulatory and a tonic inhibitory DA control in the MFC and the NAcc respectively. A schematic diagram is proposed for functional interactions between these structures.
Activity‐dependent Regulation of N‐Methyl‐d‐aspartate Receptor Subunit Expression in Rat Cerebellar Granule Cells
Authors: Audinat Etienne , Lambolez Bertrand , Rossier Jean , Crépel Francis
Published: April 2006

The glutamate receptor channels of the N‐methyl‐d‐aspartate (NMDA) subtype are composed of different subunits named NR1 and NR2A‐D. These subunits can combine in different oligomers with diverging properties and their expression is developmentally regulated. We have used rat cerebellar slice cultures to test the involvement of bioelectrical activity and synaptic transmission in the changes in NR2A‐C expression observed in developing granule cells. A correlation between the functional properties of the NMDA receptors and expression of the NR2A‐C mRNAs was obtained in single granule cells by coupling patch‐clamp recording and reverse transcription followed by polymerase chain reaction. Granule cells grown under standard culture conditions expressed mainly NR2A mRNA when examined after 15–40 days in vitro. Consistent with this observation, their responses to NMDA were only weakly reduced by 3 μM ifenprodil, a non‐competitive antagonist which discriminates between NR2A and NR2B subunits in expression systems. In cerebellar cultures chronically exposed to tetrodotoxin to eliminate spontaneous electrical activity, granule cells maintained a predominant expression of NR2B subunits and their responses to NMDA were largely inhibited by 3 μM ifenprodil. These results provide evidence that the expression of the NR2A and B subunits is regulated through an activity‐dependent mechanism leading to the formation of NMDA receptors with different pharmacological properties. Finally, the NR2C subunit, abundantly expressed in vivo by adult granule cells, was only rarely detected in slice cultures, even when excitatory synapses were formed between granule cells and fibres originating from co‐cultured brainstem explants. These data suggest that the induction of NR2C expression observed in vivo requires an additional factor(s) that remains to be identified.
Insulin and Insulin‐like Growth Factor System Components Gene Expression in the Chicken Retina From Early Neurogenesis Until Late Development and Their Effect on Neuroepithelial Cells
Authors: de La Rosa Enrique J. , Bondy Carolyn A. , Hernández‐Sánchez Catalina , Wu Xin , Zhou Jian , López‐Carranza Ana , Scavo Louis M. , Pablo Flora de
Published: April 2006

To better understand the role of insulin‐related growth factors in neural development, we have characterized by in situ hybridization in chicken embryonic retina the patterns of gene expression for insulin, insulin‐like growth factor I (IGF‐I), their respective receptors and the IGF binding protein 5 (IGFBP5) from early stages (E6) until late stages (E18)‐an analysis not performed yet in any species. In addition, we studied the effect of insulin and IGF‐I on cultured neuroepithelial cells. Insulin receptor mRNA and IGF‐I receptor mRNA were both present and showed a similar, widespread pattern throughout retina development. Insulin mRNA could be detected only by reverse transcription coupled to polymerase chain reaction. IGF‐I mRNA was concentrated in the ciliary processes and extraocular muscles early in development (embryonic day 6; E6) and in maturing retinal ganglion cells subsequently (E9–15). IGFBP5 mRNA was preferentially localized in the more differentiated central retinal zone and was maximally concentrated in the inner nuclear and ganglion cell layers at E9. These findings suggest a near constitutive expression of insulin receptor and IGF‐I receptor genes, while IGF‐I and IGFBP5 showed a highly focal spatiotemporal regulation of gene expression. Insulin and IGF‐I, already at 10−8 M, increased the proportion of PM1‐positive neuroepithelial cells found in E5 retinal cultures without affecting significantly the total number of proliferating cells. Together, these data support the finding that, during early neurogenesis in chicken retina, insulin and IGF‐I have a specific paracrine/autocrine action. This action, as well as possible effects elicited subsequently, may be dictated by restricted local synthesis of the ligands and limited access to the factors contained in the vitreous humour. In the case of IGF's role, local IGFBPs expression can contribute to the fine modulation.
Processing and Analysis of Form, Colour and Binocular Disparity in the Human Brain: Functional Anatomy by Positron Emission Tomography
Authors: Gulyás Balázs , Roland Per E.
Published: April 2006

With the purpose of mapping those anatomical structures participating in the processing and analysis of form, colour and disparity information, we have measured, with positron emission tomography and [15O]butanol, regional cerebral blood flow (rCBF) as an indicator of regional cerebral metabolic activity in 13 right‐handed male volunteers during visual discrimination of colour, form and disparity information. The brain images were anatomically standardized using a computerized brain atlas and statistically significant changes were localized by cluster analysis. The changes in rCBF between specific activation and reference states were measured and the volumes of changes were determined, as were the loci and volumes of areas commonly activated by two or three different tasks. Each of the tasks activated over a dozen distinct and separate fields in the cortex–in the occipital, parietal, temporal and frontal lobes as well as the cerebellum. A number of overlapping fields were commonly activated in two tasks (four in the form and colour tasks, five in the form and disparity tasks, and eleven in the colour and disparity tasks), and two field overlaps were present in all three tasks (in the right superior frontal and left lingual gyri). These findings indicate that, in a visual discrimination task, the processing and analysis of single visual submodalities take place in a number of cortical fields in the human brain. As the same visual submodality is processed and analysed by numerous fields and the same field may participate in the processing of different submodalities, a divergence‐convergence pattern of information processing is present in the human brain. This observation supports a hypothesis based on earlier studies in primates, namely that information processing in the visual system requires the concerted activation of a relatively large number of fields of functional networks in the brain.
Deficient Sensorimotor Gating After 6‐Hydroxydopamine Lesion of the Rat medial Prefrontal Cortex is Reversed by Haloperidol
Authors: Koch Michael , Bubser Michael
Published: April 2006

The present study sought to test the hypothesis that dopamine in the prefrontal cortex exerts an inhibitory influence on subcortical dopamine systems and that depletion of prefrontal dopamine may affect behaviour via an increase in dopamine release in the basal ganglia. We used prepulse inhibition of the acoustic startle response, i.e. the inhibition of the acoustic startle response by a preceding non‐startling stimulus, as the behavioural test, because this phenomenon of sensorimotor gating is modified in opposite directions by dopamine in the prefrontal cortex and in the basal ganglia. Rats were tested for prepulse inhibition before and after injections of the neurotoxin 6‐hydroxydopamine into the medial prefrontal cortex. We attempted to differentiate the contributions of prefrontal dopamine and noradrenaline by pretreating the animals with desipramine (6‐OHDADMI rats) or bupropion (6‐OHDABUP rats), selective inhibitors of noradrenaline and dopamine reuptake respectively. 6‐Hydroxydopamine lesion reduced prefrontal dopamine by 90% and noradrenaline by 80% in 6‐OHDADMI rats, while prefrontal dopamine was reduced by 54% and noradrenaline by 95% in 6‐OHDABUP rats. The ability of an acoustic prepulse (75 dB, 10 kHz) to inhibit the response to a startle pulse (100 dB noise burst) was maintained in sham‐lesioned rats and in 6‐OHDABUP rats. However, there was a marked reduction of prepulse inhibition (by 26%) in the 6‐OHDADMI rats. Systemic administration of the dopamine antagonist haloperidol (0.05 mg/kg), which did not affect prepulse inhibition in sham‐lesioned and in 6‐OHDABUP rats, antagonized the lesion‐induced deficit in prepulse inhibition in 6‐OHDADMI rats. These results suggest that prefrontal dopamine is involved in prepulse inhibition of the acoustic startle response. The haloperidol‐induced antagonism of the deficit in prepulse inhibition observed in 6‐OHDADMI rats is compatible with the view that prefrontal dopamine depletion led to overactivity of subcortical dopamine systems involved in prepulse inhibition, i.e. in the nucleus accumbens and/or anteromedial striatum. The significance of prefrontal noradrenaline depletion, which may have partially counteracted the effects of dopamine depletion on prepulse inhibition, is also discussed. Since prepulse inhibition is impaired in schizophrenics, the present findings lend support to the theory of prefrontal dopamine hypofunction in the aetiology of schizophrenia.