bluuebunny/crossref_metadata_2025_split huggingface dataset:
Alternative Splicing at the C‐terminal but not at the N‐terminal Domain of the NMDA Receptor NR1 is Altered in the Kindled Hippocampus
Authors: Vezzani Annamaria , Speciale Carmela , Vedova Franco Della , Tamburin Monica , Benatti Luca 
Published: April 2006

AbstractSeveral lines of evidence suggest that N‐methyl‐D‐aspartate (NMDA) receptors significantly contribute to the development of kindling. In addition, a lasting enhancement of the NMDA receptor function has been suggested to play a significant role in the chronic hyperexcitability occurring in the hippocampus after kindling epileptogenesis. We have investigated whether hippocampal kindling induces changes in the NMDA receptor at the molecular level by assessing the expression of mRNAs of the different spliced variants at the N‐terminal (exon 5) and C‐terminal (exon 21) position of the NMDA receptor 1 (NR1) gene by means of the reverse transcription‐polymerase chain reaction. Alternative splicing at exon 5 confers different sensitivity of the NMDA receptor to polyamines while exon 21 encodes a 37‐amino acid insert containing the major phosphorylation sites for protein kinase C. One week after the acquisition of stage 5 of kindling in rats (generalized tonic‐clonic seizures), the relative abundance of the two alternatively spliced forms at the C‐terminal domain, respectively containing (+) or lacking (−) exon 21, was reversed compared to controls (implanted with electrodes but not stimulated) in the dorsal hippocampus ipsilateral and contralateral to the electrical stimulation. The exon 21+/exon 21− mRNA ratio for controls was 1.3 ± 0.04 (mean ± SE); for ipsilaterally kindled rats it was 0.64 ± 0.05 (P < 0.05), and for contralaterally kindled rats it was 0.48 ± 0.07 (P < 0.01). Similar bilateral effects were observed in the ventral hippocampus (temporal pole). No changes were found 4 weeks after stage 5 seizures and 1 week after the induction of a single afterdischarge. No significant alterations were induced by kindling in the relative abundance of the spliced variants containing or lacking exon 5. Our findings show selective changes in alternative splicing of the NR1 gene after repeated application of an epileptogenic stimulus. This may generate receptors with different functional properties, which may contribute to the increased sensitivity for the induction of generalized seizures during kindling.
Regional Hypometabolism in an Acute Model of Focal Epileptic Activity in the Rat
Authors: Brueh C. , Kloiber O. , Hossman K. A. , Dorn T. , Witte O. W. 
Published: April 2006

AbstractFocal epileptic activity can be expected to influence distant brain areas via far reaching connections. To investigate such interactions the effects of focal epileptic activity on the metabolism of the brain were investigated in the rat cortex. Focal epileptic activity was induced by the application of penicillin onto the motor cortex. The focus, and to a lesser extent homotopic contralateral brain areas, showed an increase in the regional cerebral metabolic rate of glucose (rCMRGIc) as measured by [14C]deoxyglucose autoradiography. This focal hypermetabolism was accompanied by widespread hypometabolism lateral to the focus. The decrease of rCMRGIc occurred in somatosensory cortical areas but not in the motor cortex behind or in front of the focus, the perirhinal cortex or the occipital cortex. It was associated with an increase in metabolic rate in the ventrolateral, ventroposteromedial, ventroposterolateral and, in particular, posterior nuclei of the thalamus. It is hypothesized that the widespread reduction of rCMRGIc in the somatosensory cortical areas is due to inhibition via thalamic nuclei caused by activity in the motor cortex.
The NeurotroDhins BDNF, NT‐3 and NT‐4/5 Promote Survival and Morphological and Biochemical Differentiation of Striatal Neurons In Vitro
Authors: Ventimiglia Roseann , Mather Pamela E. , Jones Bruce Edward , Lindsay Ronald M. 
Published: April 2006

AbstractThe neurotrophins, brain‐derived neurotrophic factor (BDNF), neurotrophin‐3 (NT‐3), neurotrophin 4/5 (NT‐4/5) and nerve growth factor (NGF), were compared for their effects on the survival and differentiation of embryonic rat striatal neurons grown in low‐density cultures. Treatment with BDNF for 8 days resulted in a 40% increase in overall neuronal survival, a 3‐ to 5‐fold increase in the number of calbindin‐immunoreactive neurons, and an 80% increase in GABA‐positive neurons. Treatment with NT‐3 or NT‐4/5 produced a 2‐ to 3‐fold increase in the number of calbindin‐positive neurons and an increase in GABA‐positive cell number similar to that induced by BDNF. BDNF treatment produced a striking morphological differentiation of striatal GABAergic neurons, which was characterized by a doubling of the number of neurite branch points, the total area of arborization and the perikaryal area compared to control cultures. All three of these factors increased high‐affinity GABA uptake 2‐fold. NGF had no effect on any of the parameters examined. Our results show that BDNF, NT‐3 and NT‐4/5 promote the survival and/or differentiation of calbindin‐immunopositive and GABAergic striatal neurons.
Comparison of the Effects of the Neurotrophins on the Morphological Structure of Dopaminergic Neurons in Cultures of Rat Substantia Nigra
Authors: Studer Lorenz , Spenger Christian , Seiler Rolf W. , Altar C. Anthony , Lindsay Ronald M. , Hyman Carolyn 
Published: April 2006

AbstractThe effect of the various neurotrophin family members on the morphological structure of dopaminergic neurons was compared in dissociated cultures of embryonic rat ventral mesencephalon. Cultures were maintained in vitro in the presence of brain‐derived neurotrophic factor (BDNF), neurotrophin‐3 (NT‐3), neurotrophin‐4/5 (NT‐4/5), nerve growth factor (NGF) or no added growth factors. Three‐dimensional reconstructions of 48 neurons were made in each of the experimental groups following immunocytochemical staining for tyrosine hydroxylase to detect dopaminergic neurons. In addition [3H]mazindol binding analyses were carried out in replicate cultures in order to quantify the effects of the neurotrophins on the number of dopamine uptake sites. Among the neurotrophins tested, NT‐4/5 influenced the proximal morphological parameters most, as determined by a 36% increase in the soma profile area and 35% in the number of stem neurites. Analysis of neuritic size and complexity in these cultures revealed that combined neuritic length and number of segments/cell were increased by 45 and 40% respectively. A change in neurite complexity in the NT‐4/5 treated cultures was further confirmed using Scholl's concentric sphere analysis. In addition, relative to the control, NT‐4/5 increased the neuronal differentiation as evidenced by increases in varicosity density and [3H]mazindol binding by 114 and 101% respectively. BDNF and, to a lesser extent, NT‐3 also increased both proximal parameters and parameters of differentiation, but were without effect on parameters of neuritic size and Complexity. No effects on neuronal structure were observed in NGF treated cultures. These findings demonstrate that BDNF, NT‐3 and NT‐4/5 influence the morphological differentiation of dopaminergic neurons in vitro, suggesting they may play a role in the structural development and plasticity of these neurons in the mesencephalon.
Synergistic Differentiation by Chronic Exposure to Cyclic AMP and Nerve Growth Factor Renders Rat Phaeochromocytoma PC12 Cells Totally Dependent upon Trophic Support for Survival
Authors: Michel Patrick P. , Vyas Sheela , Agid Yves 
Published: April 2006

AbstractChronic dibutyryl cAMP (dbcAMP) treatment was observed not only to potentiate the differentiating actions of nerve growth factor (NGF) in PC12 cells, but to render them completely dependent on trophic support for survival even in the presence of serum proteins. When both NGF and dbcAMP were withdrawn from doubly differentiated PC12 cultures, degenerative events occurred after a lag period of 12–18 h, and by 48 h ≤ 5–10% of the cells remained viable. Reduction in [3H]dopamine uptake, an index of cell function and neurite integrity, paralleled cell demise. At the cellular level, ∼20–30% of the nuclei exhibited clear signs of chromatin fragmentation, as characterized by propidium iodide staining, suggesting that degeneration occurred by apoptosis. The cells could be rescued completely from degeneration by dbcAMP or by other cAMP analogues, whereas NGF and depolarization were also effective, but only partially. Phorbol 12‐myristate‐13‐acetate failed to afford protection. If deprivation was interrupted, cell demise could be stopped by restoration of initial culture conditions. Degenerative changes produced by deprivation and recovery processes were not inhibited by macromolecular synthesis inhibitors, e.g. cycloheximide and actinomycin‐D. However, chronic addition of cycloheximide prior to deprivation greatly impaired the differentiation of NGF/dbcAMP cells, allowing these cells to withstand trophic support withdrawal. Altogether our results indicate that the cAMP transduction pathway plays a crucial role not only in the differentiation but also in the survival of NGF/dbcAMP PC12 cells.
Accelerated Structural Maturation Induced by Synapsin I at Developing Neuromuscular Synapses of Xenopus laevis
Authors: Valtorta Flavia , Lezzi Numa , Benfenati Fabio , Lu Bai , Poo Mu‐ming , Greengard Paul 
Published: April 2006

AbstractThe role of synapsin I, a synaptic vesicle‐associated phosphoprotein, in the maturation of nerve–muscle synapses was investigated in nerve–muscle co‐cultures prepared from Xenopus embryos loaded with the protein by the early blastomere injection method. The stage of maturation of the synapses was analysed by electron microscopy as well as by whole‐cell patch‐clamp recording. The acceleration in the functional maturation of neuromuscular synapses induced by synapsin I was accompanied by a profound rearrangement in the ultrastructure of the nerve terminal. Nerve terminals formed by synapsin I‐loaded neurons were characterized by a higher number of small synaptic vesicles organized in clusters and predominantly localized close to the nerve terminal plasma membrane, a smaller number of large dense‐core vesicles and no significant change in the number of coated vesicles. Precocious development of active zone‐like structures as well as deposition of basal lamina into the synaptic cleft were also observed at these synapses. These results support a role for synapsin I in the architectural changes which occur during synaptogenesis and lead to the maturation of quantal neurotransmitter release mechanisms.
Kainic Acid‐induced Heat Shock Protein‐70, mRNA and Protein Expression is Inhibited by MK‐801 in Certain Rat Brain Regions
Authors: Planas Anna M. , Soriano Marc A. , Ferrer Isidre , Farré Eduard Rodríguez 
Published: April 2006

AbstractThe regional expression of inducible 72 kDa heat shock protein (HSP‐70), HSP‐70 mRNA and the neuropathological outcome of their expression were examined in the rat brain following systemic administration of kainic acid (9 mg/kg), and also after pretreatment with the non‐competitive N‐methyl‐D‐aspartate antagonist MK‐801 (1 mg/kg). Five hours after administration of kainic acid alone, dense expression of HSP‐70 mRNA was found within the limbic system, mainly in the hippocampus, piriform and entorhinal cortices, amygdaloid complex, thalamic nuclei, subiculum and in other cortical areas in rats that had shown convulsive behaviour. At 24 h, HSP‐70 immunoreactivity was seen in most areas previously expressing HSP‐70 mRNA, except the piriform and entorhinal cortices and several ventral nuclei of the amygdaloid complex. Histopathological examination at 24 h revealed marked cell loss in these latter regions and less severe histopathological changes in other areas of the limbic system in brains of convulsive rats. No alterations were apparent in non‐convulsive rats. The percentage of rats showing convulsive behaviour with kainic acid was reduced from 74 to 4% following pretreatment with MK‐801. In addition, MK‐801 inhibited the kainic acid‐induced expression of HSP‐70 mRNA and protein in certain brain regions, notably the cortex, the pyramidal cell layer of CA1, and discrete thalamic nuclei. However, HSP‐70 mRNA induction was sustained in the pyramidal cell layer of CA3, the amygdaloid complex and the subiculum, despite the fact that none of these rats convulsed. MK‐801 prevented necrosis in all rats examined except the single rat that had shown convulsive behaviour. These results show that early regional expression of inducible HSP‐70 mRNA allows the visualization of regions affected by kainic acid and maps regions inhibited by MK‐801. In addition, the results identify brain regions putatively involved in the manifestation of limbic convulsions. Furthermore, these data illustrate that the induction of HSP‐70 mRNA is not predictive of cell death or survival.
Evidence for Glutamate as Neurotransmitter in Trigemino‐ and Spinothalamic Tract Terminals in the Nucleus Submedius of Cats
Authors: Ericson Ann‐Charlott , Blomqvist Anders , (Bud) Craig A. D. , Ottersen Ole P. , Broman Jonas 
Published: April 2006

AbstractThe nucleus submedius in the medial thalamus of cats is an important termination site for lamina I trigemino‐ and spinothalamic tract (TSTT) neurons, many of which are nociceptive‐specific, and the nucleus submedius has been proposed to be a dedicated nociceptive substrate involved in the affective aspect of pain. In the present study, the distribution of glutamate was examined by immunocytochemical methods in order to evaluate the possible role of this amino acid as a neurotransmitter in TSTT terminals in the nucleus submedius. TSTT terminals were identified by anterograde transport of horseradish peroxidase and wheatgerm agglutinin‐horseradish peroxidase conjugate from the spinal cord or the medullary dorsal horn. Quantitative analysis of immunogold labelling revealed that TSTT terminals contain about twice the tissue average of glutamate‐like immunoreactivity. A strong positive correlation was found between the density of synaptic vesicles and the density of gold particles in these terminals, whereas no relationship was seen between these variables in GABAergic presynaptic dendrites. Enrichment of glutamate‐like immunoreactivity (∼250% of the tissue average) was also observed in terminals of presumed cortical origin. Presynaptic dendrites and neuron cell bodies in the nucleus submedius were found to contain relatively low levels of glutamate‐like immunoreactivity, at or below the tissue average. These observations provide evidence that glutamate is a neurotransmitter in lamina I TSTT terminals in the nucleus submedius. The findings also suggest glutamatergic neurotransmission between cortical afferents and nucleus submedius neurons. Glutamate is therefore likely to be an important mediator of nociceptive processing in the medial thalamus.
The Stimulation of Thalamic Neurite Outgrowth by Cortex‐derived Growth Factors In Vitro: The Influence of Cortical Age and Activity
Authors: Lotto R. Beau , Price David J. 
Published: April 2006

AbstractRecent in vitro experiments have provided useful insights into the development of connections between the thalamus and the cortex. While most of these previous studies focused on neurite guidance and target recognition, our experiments used a serum‐free culture system to examine the possible roles of unidentified diffusible cortex‐derived growth factors. We demonstrated that occipital cortical explants release diffusible growth factors that enhance neurite outgrowth from explants of the posterior thalamus (the region around the developing lateral geniculate nucleus). The amount of thalamic outgrowth was dependent on the age of the cocultured cortical slices. Our results suggest that there is an overall increase in the release of cortex‐derived growth factors during the first three postnatal weeks in mice; this parallels known postnatal increases in the production of several identified growth factors. We found evidence for two peaks in the release of cortex‐derived growth factors during the general upward trend, the first at around postnatal day 6 (shortly after thalamocortical innervation of layer 4) and a second between postnatal days 14 and 18 (just after eye‐opening). The increased release of cortex‐derived growth factors was not found when cortical slices were from mice that had been dark‐reared from birth, suggesting that neural activity may be important for enhancing release. Other regions of the central nervous system, including the cerebellum and medulla, were also capable of stimulating some thalamic outgrowth; neither additional explants of the thalamus nor hepatic explants enhanced outgrowth. Fibroblast growth factor is one substance that is distributed preferentially among those tissues that were stimulatory in our experiments. Its level of transcription is known to increase in the brain during the first three postnatal weeks and to be influenced by neural activity. At low doses, fibroblast growth factor greatly increased outgrowth from isolated posterior thalamic explants. Nerve growth factor, another candidate molecule, was less effective. Overall, our results complement the in vivo observations of others on the synthesis of identified growth factors in the cortex and the factors that influence their production. They suggest that growth factors may influence thalamic neurons, and indicate that fibroblast growth factor, and possibly nerve growth factor, are two candidates for molecules mediating the in vitro effects.
Selective Lesioning of the Basal Forebrain Cholinergic System by Intraventricular 192 IgG–saporin: Behavioural, Biochemical and Stereological Studies in the Rat
Authors: Leanza G. , Nilsson O. G. , Wiley R. G. , Björklund A. 
Published: April 2006

AbstractThe elucidation of the functional role of the basal forebrain cholinergic system will require access to a highly specific and efficient cholinergic neurotoxin. Recently, selective depletion of the nerve growth factor (NGF) receptor‐bearing cholinergic neurons in the rat basal forebrain and a dramatic loss of cholinergic innervation in the related cortical regions have been obtained following intraventricular injection of a newly introduced immunotoxin, 192 IgG‐saporin. Here we extend these initial findings and report that administration of increasing doses (1.25, 2.5, 5.0 or 10 μg) of the 192 IgG‐saporin conjugate into the lateral ventricles of adult rats induced dose‐dependent impairments in the water maze task and passive avoidance retention, but only weak and inconsistent effects on locomotor activity. These behavioural changes were paralleled by a reduction in choline acetyltransferase activity in hippocampus and several cortical areas (up to 97%) and selective depletions of NGF receptor‐positive cholinergic neurons in the septal‐diagonal band area and nucleus basalis magnocellularis (up to 99%). By contrast, the non‐cholinergic parvalbumin‐containing neurons in the septum were completely spared, and other cholinergic projection systems (such as in the striatum, thalamus, brainstem and spinal cord) were unaffected even at the highest dose. The observed changes in the water maze and passive avoidance tasks, as well as the cholinergic cell loss, were maintained up to at least 8 months following the intraventricular injection of a single dose (5 μg) of the immunotoxin. The results confirm the usefulness of the 192 IgG‐saporin toxin for selective and profound lesions of the basal forebrain cholinergic neurons and provide further support for a role of the basal forebrain cholinergic system in cognitive functions.
Neutralizing Anti‐p21ras Fabs Suppress Rat Sympathetic Neuron Survival Induced by NGF, LIF, CNTF and cAMP
Authors: Nobes Catherine D. , Tolkovsky Aviva M. 
Published: April 2006

AbstractIn purified cultures of newly isolated rat sympathetic neurons plated on laminin, apoptosis is suppressed by the cytokines leukaemia inhibitory factor (LIF) and ciliary neurotrophic factor (CNTF), by the permeant cAMP analogue 8‐(4‐chlorophenylthio)cAMP, and by nerve growth factor. Whilst nerve growth factor, 8‐(4‐chlorophenylthio) cAMP and LIF/CNTF initiate survival by using different kinases, in each case survival is inhibited by a Fab fragment of Y13‐259, a neutralizing antibody to p2lras proteins, but not by rat IgG Fab. The inhibitory effect of Y13‐259 could be partially attenuated by cotrituration of the Fab with T′24(inactive)ras. Thus, prevention of apoptosis in rat sympathetic neurons by several different survival factors appears to be critically dependent on p21 ras protein activity.
Divalent Cation Entry in Cultured Rat Cerebellar Granule Cells Measured Using Mn2+ Quench of Fura 2 Fluorescence
Authors: Simpson P. B. , Challiss R. A. J. , Nahorski S. R. 
Published: April 2006

AbstractIn this study the rate of Mn2+ quench of fura‐2 fluorescence evoked by glutamatergic and cholinergic agonists, depolarization and Ca2+ store modulators was measured in cultured cerebellar granule cells, in order to study their effects on Ca2+ entry in isolation from effects on Ca2+ store release. The rate of fluorescence quench by 0.1 mM Mn2+ was markedly increased by 25 mM K+‐ evoked depolarization or by 200 μM N‐methyl‐D‐aspartate (NMDA), with a significantly greater increase occurring during the rapid‐onset peak phase compared to the plateau phase of the K+‐ or NMDA‐evoked [Ca2+]i response. The stimulatory effect of NMDA on Mn2+ quench was abolished by dizocilpine (10 μM), but nitrendipine (2 μM), while decreasing the rate of basal quench, did not affect NMDA‐stimulated Mn2+ entry. This suggests that nitrendipine may not act on NMDA channels in granule cells, at least under these conditions, and that voltage‐operated Ca2+ channels are involved in control quench whereas the NMDA‐evoked quench is dependent on entry through the receptor channel. The t1/2 of quench was unaffected by α‐amino‐hydroxyisoxazole propionic acid (200 μM) and carbamyl choline (1 mM). Neither thapsigargin (10 μM) nor dantrolene (30 μM) significantly affected the rate of quench under control or NMDA‐ or K+‐stimulated conditions, which confirms that the previously reported inhibitory effects on [Ca2+]i elevations evoked by these agents are due to actions on Ca2+ stores. However, thapsigargin elevated [Ca2+Ii in the presence of normal [Ca2+]i, but not in nominally Ca2+‐free medium, indicating that it evokes Ca2+ entry in cerebellar granule cells, probably subsequent to store depletion, which appears to be either too small to be detected by Mn2+ quench or to occur via Mn2+‐impermeant channels.