bluuebunny/crossref_metadata_2025_split huggingface dataset:
Excitable properties in astrocytes derived from human embryonic CNS stem cells
Authors: Gritti Angela , Rosati Barbara , Lecchi Marzia , Vescovi Angelo L. , Wanke Enzo 
Published: March 2003

AbstractAlthough it is widely believed that astrocytes lack excitability in adult tissue, primitive action potential‐like responses have been elicited from holding potentials negative to −80 mV, in cultured and injury‐induced gliotic rodent astrocytes and in human glia under pathological conditions such as glioblastomas and temporal lobe epilepsy. The present study was designed to investigate the properties of astrocytes (identified by immunoreactivity for glial fibrillary acidic protein) derived from multipotent human embryonic CNS stem cells and cultured for 12–25 days in differentiating conditions. We describe here for the first time that brief (1 ms) current pulses elicit spikes from a resting potential (VREST) of ≈ −37 mV and, more interestingly, that spontaneous firing can be occasionally recorded in human astrocytes. A voltage‐clamp study revealed that in these cells: (i) the half‐inactivation of the tetrodotoxin (TTX)‐sensitive Na+ channels is around VREST; (ii) the delayed rectifier K+ current is very small; (iii) the ever‐present transient outward A‐type K+ channels are paradoxically capable of inhibiting the action potentials elicited from a negative membrane potential (−55 to −60 mV); and (iv) inwardly rectifying currents are not present. The responses predicted from a simulation model are in agreement with the experiments. As suggested by recent studies, the decrease of Na+ channel expression and the changes of the electrophysiological properties during the postnatal maturation of the CNS seem to exclude the possibility that astrocytes may play an excitable role in adult tissue. Our data show that excitability and firing should be considered an intrinsic attribute of human astrocytes during CNS development. This is likely to have physiological importance because the role of astrocytes during development is different from the [K+]o‐buffering role played in adult CNS, namely the glutamate release and/or the guiding of migrating neurons.
Differential modulation of rod and cone calcium currents in tiger salamander retina by D2 dopamine receptors and cAMP
Authors: Stella Salvatore L. , Thoreson Wallace B. 
Published: March 2003

AbstractSynaptic transmission from vertebrate photoreceptors involves activation of L‐type calcium currents (ICa). Dopamine is an important circadian neuromodulator in the retina and photoreceptors possess D2 dopamine receptors. We examined modulation of ICa by dopamine and cAMP in retinal slices and isolated cells of larval tiger salamander. Results show that dopamine and a D2 agonist, quinpirole, enhanced ICa in rods and red‐, blue‐ and UV‐sensitive small single cones but inhibited ICa in red‐sensitive large single cones. A D1 agonist, SKF‐38393, was without effect. Quinpirole effects were blocked by pertussis toxin (PTx) pretreatment indicating involvement of PTx‐sensitive G‐proteins. Like dopamine, inhibition of cAMP‐dependent protein kinase (PKA) by Rp‐cAMPS enhanced ICa in rods and small single cones, but inhibited ICa in large single cones. In contrast, forskolin and Sp‐cAMPS, which stimulate PKA, inhibited ICa in rods and small single cones but enhanced ICa in large single cones. Sp‐cAMPS also occluded effects of quinpirole. These results suggest that D2 receptors modulate ICa via inhibition of cAMP. Differences among the responses of photoreceptors to cAMP are consistent with the possibility that small single cones and rods may possess different Ca2+ channel subtypes than large single cones. The results with dopamine and quinpirole showing inhibition of ICa in large single cones and enhancement of rod ICa were unexpected because previous studies have shown that dopamine suppresses rod inputs and enhances cone inputs into second‐order neurons. The present results therefore indicate that the dopaminergic enhancement of cone inputs does not arise from modulation of photoreceptor ICa.
Experience‐dependent plasticity of visual acuity in rats
Authors: Prusky Glen T. , West Paul W. R. , Douglas Robert M. 
Published: March 2003

AbstractRats have become a popular model for investigating the mechanisms underlying ocular dominance plasticity; however, no quantitative assessment of the effects of visual deprivation on behavioural acuity has been reported in this species. We measured the spatial acuity of monocularly and binocularly deprived rats with a visual discrimination task. The average spatial acuity of normal rats and rats deprived of vision after postnatal day 40 was ≈ 1 cycle/degree. Monocular deprivation up to postnatal day 40 resulted in a 30% decrease in acuity and there was no recovery after 8 months. Identical binocular deprivation produced a comparable but significantly smaller reduction in acuity. The deleterious effects of monocular and binocular deprivation on visual acuity indicate that the development of cortical receptive field properties related to spatial tuning are affected by both monocular and binocular deprivation. The similarities in the effects of visual deprivation on visual acuity between rats and other mammals confirm that rats are a good model system for studying the cellular and molecular mechanisms underlying experience‐dependent visual plasticity.
GABAB receptor protein and mRNA distribution in rat spinal cord and dorsal root ganglia
Authors: Towers S. , Princivalle A. , Billinton A. , Edmunds M. , Bettler B. , Urban L. , Castro‐Lopes J. , Bowery N. G. 
Published: March 2003

AbstractThe presence of metabotropic receptors for GABA, GABAB, on primary afferent terminals in mammalian spinal cord has been previously reported. In this study we provide further evidence to support this in the rat and show that the GABAB receptor subunits GABAB1 and GABAB2 mRNA and the corresponding subunit proteins are present in the spinal cord and dorsal root ganglion. We also show that the predominant GABAB1 receptor subunit mRNA present in the afferent fibre cell body appears to be the 1a form. In frozen sections of lumbar spinal cord and dorsal root ganglia (DRG) GABAB receptors were labelled with [3H]CGP 62349 or the sections postfixed with paraformaldehyde and subjected to in situ hybridization using oligonucleotides designed to selectively hybridize with the mRNA for GABAB(1a), GABAB(1b) or GABAB2. For immunocytochemistry (ICC), sections were obtained from rats anaesthetized and perfused‐fixed with paraformaldehyde. The distribution of binding sites for [3H]CGP 62349 mirrored that previously observed with [3H]GABA at GABAB sites. The density of binding sites was high in the dorsal horn but much lower in the ventral regions. By contrast, the density of mRNA (pan) was more evenly distributed across the laminae of the spinal cord. The density of mRNA detected with the pan probe was high in the DRG and distributed over the neuron cell bodies. This would accord with GABAB receptor protein being formed in the sensory neurons and transported to the primary afferent terminals. Of the GABAB1 mRNA in the DRG, ≈ 90% was of the GABAB(1a) form and ≈ 10% in the GABAB(1b) form. This would suggest that GABAB(1a) mRNA may be responsible for encoding presynaptic GABAB receptors on primary afferent terminals in a manner similar to that we have previously observed in the cerebellar cortex. GABAB2 mRNA was also evenly distributed across the spinal cord laminae at densities equivalent to those of GABAB1 in the dorsal horn. GABAB2 mRNA was also detected to the same degree within the DRG. Immunocytochemical analysis revealed that GABAB(1a), GABAB(1b) and GABAB2 were all present in the spinal cord. GABAB(1a) labelling appeared to be more dense than GABAB(1b) and within the superficial dorsal horn GABAB(1a) was present in the neuropil whereas GABAB(1b) was associated with cell bodies in this region. Both 1a and 1b immunoreactivity was expressed in motor neurons in lamina IX. GABAB2 immunoreactivity was expressed throughout the spinal cord and was evident within the neuropil of the superficial laminae.
Deficit in conditional visuomotor learning by local infusion of bicuculline into the ventral prefrontal cortex in monkeys
Authors: Wang Min , Zhang Hui , Li Bao‐Ming 
Published: March 2003

AbstractTo explore the role of the ventral prefrontal cortex (PFv) in conditional visuomotor learning, we infused locally bicuculline, a GABAergic antagonist, into the PFv of two monkeys, well trained on a two‐problem visuomotor task. The task required the monkeys to execute one of two motor actions (moving a handle to the left or to the right) in response to one of two familiar visual patterns (circle or triangle). The two patterns mapped 1 : 1 onto the two motor actions: for each pattern one and only one motor action was scored, correct and reinforced. In contrast to these sessions with familiar patterns, in the learning sessions the monkeys were presented with one or two novel patterns and required to learn the arbitrarily determined associations between these patterns and the two motor actions. We found that bilateral infusion of bicuculline into PFv dramatically impaired the monkeys' ability to learn novel pattern–response associations: the trials and errors to criterion (90% correct) increased significantly. The errors were mainly an inability to apply ‘Win‐Stay’, ‘Lose‐Shift’ and ‘Change‐Shift’ strategies. There was no effect on the monkeys' performance in responding to familiar patterns. Similar infusion of bicuculline into the dorsal prefrontal cortex was without effect on either novel‐pattern learning or familiar‐pattern performance. We conclude that the ventral prefrontal cortex is necessary for learning new visuomotor associations, but has less importance, if any, for performing pre‐established ones.
Inhibition of brain‐derived neurotrophic factor and glial cell line‐derived neurotrophic factor expression reduces dopaminergic sprouting in the injured striatum
Authors: Batchelor P. E. , Liberatore G. T. , Porritt M. J. , Donnan G. A. , Howells D. W. 
Published: March 2003

AbstractAfter striatal injury, sprouting dopaminergic fibres grow towards and intimately surround wound macrophages which, together with microglia, express the dopaminergic neurotrophic factors glial cell line‐derived neurotrophic factor (GDNF) and brain derived neurotrophic factor (BDNF). To evaluate the importance of these endogenously secreted neurotrophic factors in generating striatal peri‐wound dopaminergic sprouting, the peri‐wound expression of BDNF or GDNF was inhibited by intrastriatal infusion of antisense oligonucleotides for 2 weeks in mice. Knock‐down of both BDNF and GDNF mRNA and protein levels in the wounded striatum were confirmed by in situ hybridization and enzyme‐linked immunosorbent assay, respectively. Dopamine transporter immunohisto‐chemistry revealed that inhibition of either BDNF or GDNF expression resulted in a marked decrease in the intensity of peri‐wound sprouting. Quantification of this effect using [H3]‐mazindol autoradiography confirmed that peri‐wound sprouting was significantly reduced in mice receiving BDNF or GDNF antisense infusions whilst control infusions of buffered saline or sense oligonucleotides resulted in the pronounced peri‐wound sprouting response normally associated with striatal injury. BDNF and GDNF thus appear to be important neurotrophic factors inducing dopaminergic sprouting after striatal injury.
Soluble TNF receptors partially protect injured motoneurons in the postnatal CNS
Authors: Terrado José , Monnier Dominique , Perrelet Daniel , Vesin Dominique , Jemelin Stéphane , Buurman Wim A. , Mattenberger Louise , King Béatrice , Kato Ann C. , Garcia Irene 
Published: March 2003

AbstractThere is accumulating evidence that cytokines are involved in the functioning of the brain and the spinal cord. However, it has been controversial whether they exert a neurotoxic or a neuroprotective effect. To address this question in vivo, we have examined the survival of injured motoneurons in a line of transgenic mice that overexpress the soluble form of tumour necrosis factor receptor‐1 (sTNFR1). In these animals, all of the circulating TNF and lymphotoxin‐α are neutralized by the continuous expression of the soluble receptor. Following axotomy of the facial nerve in 7‐day‐old control mice, we observed a loss of approximately 90% of the motoneurons at two weeks survival. In the transgenic mice under the same conditions, the percentage of motoneuron survival was increased two‐fold (515 vs. 224) and varied as a function of the level of the circulating receptor. These results indicate that neutralization of endogenous TNF and lymphotoxin‐α by means of overexpression of the soluble receptor can decrease cell death of injured motoneurons and suggest that these cytokines may play an important role in neuronal degeneration in the CNS following a lesion.
Caspase‐3 is activated following axotomy of neonatal facial motoneurons and caspase‐3 gene deletion delays axotomy‐induced cell death in rodents
Authors: Vanderluit Jacqueline L. , McPhail Lowell T. , Fernandes Karl J. L. , McBride Christopher B. , Huguenot Claire , Roy Sophie , Robertson George S. , Nicholson Donald W. , Tetzlaff Wolfram 
Published: March 2003

AbstractIn this report, we examined the possible functions of the cell death protease, caspase‐3, in the axotomy‐induced apoptosis of facial motoneurons in newborn rodents. Using in situ hybridization and Western blot, we found higher levels of caspase‐3 mRNA and pro‐caspase‐3 protein expression in motoneurons of neonatal and 2‐week‐old rats than adult rats. Following facial motoneuron axotomy, caspase‐3 mRNA and protein expression increased in motoneurons of both neonatal and adult rats. However, using an antibody directed to the activated form of the caspase‐3 protease, we found that catalytically active caspase‐3 was present only in axotomized neonatal motoneurons. As motoneurons in neonatal but not adult rodents are susceptible to axotomy‐induced apoptosis, we hypothesized that caspase‐3 may play a role in their demise. To determine the necessity of caspase‐3 activation in axotomy‐induced apoptosis, we counted the number of surviving motoneurons at 4 and 7 days following axotomy in wild type mice and caspase‐3 gene‐deleted mice. There were nearly three times more surviving motoneurons in caspase‐3 gene‐deleted mice than in wild type mice at both 4 days (mean 1074 vs. 464, P < 0.005) and 7 days (mean 469 vs. 190, P < 0.005) following injury, indicating a slower rate of death. Examination of the dying motoneurons using TUNEL staining (for fragmented DNA) and bisbenzimide staining (for nuclear morphology) revealed incomplete nuclear condensation in caspase‐3‐deficient motoneurons. These results demonstrate that caspase‐3 activation plays important roles in the rapid demise of axotomized neonatal motoneurons.
Riluzole inhibits the persistent sodium current in mammalian CNS neurons
Authors: Urbani Andrea , Belluzzi Ottorino 
Published: March 2003

AbstractThe effects of 0.1–100 μm riluzole, a neuroprotective agent with anticonvulsant properties, were studied on neurons from rat brain cortex. Patch‐clamp whole‐cell recordings in voltage‐clamp mode were performed on thin slices to examine the effects of the drug on a noninactivating (persistent) Na+ current (INa,p). INa,p was selected because it enhances neuronal excitability near firing threshold, which makes it a potential target for anticonvulsant drugs. When added to the external solution, riluzole dose‐dependently inhibited INa,p up to a complete blocking of the current (EC50 2 μm), showing a significant effect at therapeutic drug concentrations. A comparative dose‐effect study was carried out in the same cells for the other main known action of riluzole, the inhibitory effect on the fast transient sodium current. This effect was confirmed in our experiments, but we found that it was achieved at levels much higher than putative therapeutic concentrations. Only the effect on INa,p, and not that on fast sodium current, can account for the reduction in neuronal excitability observed in cortical neurons following riluzole treatment at therapeutic concentrations, and this might represent a novel mechanism accounting for the anticonvulsant and neuroprotective properties of riluzole.
Acute transcranial magnetic stimulation of frontal brain regions selectively modulates the release of vasopressin, biogenic amines and amino acids in the rat brain
Authors: Keck Martin E. , Sillaber Inge , Ebner Karl , Welt Tobias , Toschi Nicola , Kaehler Stefan T. , Singewald Nicolas , Philippu Athineos , Elbel Gregor K. , Wotjak Carsten T. , Holsboer Florian , Landgraf Rainer , Engelmann Mario 
Published: March 2003

AbstractUsing intracerebral microdialysis in urethane‐anaesthetized adult male Wistar rats, we monitored the effects of acute repetitive transcranial magnetic stimulation (rTMS; 20 trains of 20 Hz, 2.5 s) on the intrahypothalamic release of arginine vasopressin (AVP) and selected amino acids (glutamate, glutamine, aspartate, serine, arginine, taurine, γ‐aminobutyric acid) and the intrahippocampal release of monoamines (dopamine, noradrenaline, serotonin) and their metabolites (homovanillic acid, 3,4‐dihydroxyphenylacetic acid, 5‐hydroxyindoleacetic acid). The stimulation parameters were adjusted according to the results of accurate computer reconstructions of the current density distributions induced by rTMS in the rat and human brains, ensuring similar stimulation patterns in both cases. There was a continuous reduction in AVP release of up to 50% within the hypothalamic paraventricular nucleus in response to rTMS. In contrast, the release of taurine, aspartate and serine was selectively stimulated within this nucleus by rTMS. Furthermore, in the dorsal hippocampus the extracellular concentration of dopamine was elevated in response to rTMS. Taken together, these data provide the first in vivo evidence that acute rTMS of frontal brain regions has a differentiated modulatory effect on selected neurotransmitter/neuromodulator systems in distinct brain areas.
Regional and cellular expression of the parkin gene in the rat cerebral cortex
Authors: D'agata Velia , Grimaldi Maurizio , Pascale Alessia , Cavallaro Sebastiano 
Published: March 2003

AbstractA mutation in the parkin gene has been identified as the cause for an autosomal recessively inherited form of early onset Parkinson's disease. We have recently isolated the mRNA coding for the rat homologue of parkin and showed its widespread expression in the central nervous system (CNS) by in situ hybridization. In the present study we investigated the distribution of parkin in the rat cerebral cortex with a polyclonal antibody that reacts with a single ∼ 52‐kDa protein, corresponding to the predicted molecular mass of parkin. Conventional light microscopic studies revealed intense parkin immunoreactivity (IR) throughout the cortex. Examination of mixed cortical neuro‐glial cultures by indirect immunofluorescence technique coupled to traditional epifluorescence and confocal microscopy analysis demonstrated the expression of parkin in the cytoplasm and neurites of neurons, and its absence in glial fibrillary acidic protein (GFAP)‐positive astrocytes. The predominant neuronal parkin‐IR and ‐mRNA expression was confirmed by Western blot analysis and reverse transcription‐polymerase chain reaction (RT‐PCR), respectively, performed on highly enriched neuronal and type I astrocytes cultures. The information gathered in our study about the cellular and subcellular distribution of parkin should facilitate further research on its physiological role in the nervous system.
Functional connections are established in the deafferented rat spinal cord by peripherally transplanted human embryonic sensory neurons
Authors: Levinsson Anders , Holmberg Hans , Schouenborg Jens , Seiger Åke , Aldskogius Håkan , Kozlova Elena N. 
Published: March 2003

AbstractFunctionally useful repair of the mature spinal cord following injury requires axon growth and the re‐establishment of specific synaptic connections. We have shown previously that axons from peripherally grafted human embryonic dorsal root ganglion cells grow for long distances in adult host rat dorsal roots, traverse the interface between the peripheral and central nervous system, and enter the spinal cord to arborize in the dorsal horn. Here we show that these transplants mediate synaptic activity in the host spinal cord. Dorsal root ganglia from human embryonic donors were transplanted in place of native adult rat ganglia. Two to three months after transplantation the recipient rats were examined anatomically and physiologically. Human fibres labelled with a human‐specific axon marker were distributed in superficial as well as deep laminae of the recipient rat spinal cord. About 36% of the grafted neurons were double labelled following injections of the fluorescent tracers MiniRuby into the sciatic and Fluoro‐Gold into the lower lumbar spinal cord, indicating that some of the grafted neurons had grown processes into the spinal cord as well as towards the denervated peripheral targets. Electrophysiological recordings demonstrated that the transplanted human dorsal roots conducted impulses that evoked postsynaptic activity in dorsal horn neurons and polysynaptic reflexes in ipsilateral ventral roots. The time course of the synaptic activation indicated that the human fibres were non‐myelinated or thinly myelinated. Our findings show that growing human sensory nerve fibres which enter the adult deafferentated rat spinal cord become anatomically and physiologically integrated into functional spinal circuits.
The role of 5‐HT1A receptors in mediating the anxiogenic effects of nicotine following lateral septal administration
Authors: Cheeta Survjit , Kenny Paul J. , File Sandra E. 
Published: March 2003

AbstractThe purpose of the present study was to determine the role of the 5‐HT1A receptors in the lateral septum in the mediation of the anxiogenic effects of nicotine in the social interaction and elevated plus maze tests of anxiety in the rat. Bilateral infusion of (–)‐nicotine (4 and 8 μg) and of the 5‐HT1A receptor agonist 8‐OH‐DPAT (200 and 500 ng) into the lateral septum decreased the time spent in social interaction, indicating anxiogenic effects. The anxiogenic effect of 8‐OH‐DPAT (500 ng) was completely reversed by coadministration of a behaviourally inactive dose of the 5‐HT1A receptor antagonist, WAY 100635 (200 ng). The anxiogenic effect of the lower dose of (–)‐nicotine (4 μg) was completely reversed by WAY 100635 (200 ng), but the reversal was only partial following administration of 8 μg nicotine. In a second test of anxiety, the elevated plus maze, lateral septal administration of 8‐OH‐DPAT (500 ng) and nicotine (4 μg) induced anxiogenic effects. In this test, the anxiogenic effect of nicotine (4 μg) was completely reversed by coadministration of WAY 100635 (200 ng). The effects of 8‐OH‐DPAT demonstrate that stimulation of 5‐HT1A receptors in the lateral septum has anxiogenic effects in two animal tests and that the anxiogenic effects of nicotine are mediated at least in part by these 5‐HT1A receptors.