bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mutational scanning of the human serotonin transporter reveals fast translocating serotonin transporter mutants
Authors: Kristensen Anders S. , Larsen Mads B. , Johnsen Laust B. , Wiborg Ove 
Published: April 2004

AbstractThe serotonin transporter (SERT) belongs to a family of sodium–chloride‐dependent transporters responsible for uptake of amino acids and biogenic amines from the extracellular space. SERT represents a major pharmacological target in the treatment of several clinical conditions, including depression and anxiety. In the present study we have undertaken a mutational scanning of human SERT in order to identify residues that are responsible for individual differences among related monoamine transporters. One mutant, G100A, was inactive in transport. However, ligand binding affinity was similar to wild‐type, suggesting that G100A amongst different possible SERT conformations is restrained to a binding conformation. We suggest that the main role of glycine‐100 is to confer structural flexibility during substrate translocation. For the two single mutants, T178A and F263C, uptake rates and Km values were both several‐fold higher than wild‐type while binding affinities and inhibitory potencies decreased considerably for several drugs. Ion dependency increased and only at hyperosmotic concentrations were Km values partly restored. For the double mutant, T178A/F263C, shifts in uptake kinetics and ligand affinities, as well as ion dependencies, were drastic. Effects were synergistic compared to the corresponding single mutants. In conclusion, we suggest that mutating threonine‐178 to an alanine and phenylalanine‐263 to a cysteine mainly alter the overall uptake kinetics of SERT by affecting the conformational equilibrium of different transporter conformations.
PACAP inhibits delayed rectifier potassium current via a cAMP/PKA transduction pathway: evidence for the involvement of IK in the anti‐apoptotic action of PACAP
Authors: Mei Y. A. , Vaudry D. , Basille M. , Castel H. , Fournier A. , Vaudry H. , Gonzalez B. J. 
Published: April 2004

AbstractActivation of potassium (K+) currents plays a critical role in the control of programmed cell death. Because pituitary adenylate cyclase‐activating polypeptide (PACAP) has been shown to inhibit the apoptotic cascade in the cerebellar cortex during development, we have investigated the effect of PACAP on K+ currents in cultured cerebellar granule cells using the patch‐clamp technique in the whole‐cell configuration. Two types of outward K+ currents, a transient K+ current (IA) and a delayed rectifier K+ current (IK) were characterized using two different voltage protocols and specific inhibitors of K+ channels. Application of PACAP induced a reversible reduction of the IK amplitude, but did not affect IA, while the PACAP‐related peptide vasoactive intestinal polypeptide had no effect on either types of K+ currents. Repeated applications of PACAP induced gradual attenuation of the electrophysiological response. In the presence of guanosine 5′‐[γthio]triphosphate (GTPγS), PACAP provoked a marked and irreversible IK depression, whereas cell dialysis with guanosine 5′‐[βthio]diphosphate GDPβS totally abolished the effect of PACAP. Pre‐treatment of the cells with pertussis toxin did not modify the effect of PACAP on IK. In contrast, cholera toxin suppressed the PACAP‐induced inhibition of IK. Exposure of granule cells to dibutyryl cyclic adenosine monophosphate (dbcAMP) mimicked the inhibitory effect of PACAP on IK. Addition of the specific protein kinase A inhibitor H89 in the patch pipette solution prevented the reduction of IK induced by both PACAP and dbcAMP. PACAP provoked a sustained increase of the resting membrane potential in cerebellar granule cells cultured either in high or low KCl‐containing medium, and this long‐term depolarizing effect of PACAP was mimicked by the IK specific blocker tetraethylammonium chloride (TEA). In addition, pre‐incubation of granule cells with TEA suppressed the effect of PACAP on resting membrane potential. TEA mimicked the neuroprotective effect of PACAP against ethanol‐induced apoptotic cell death, and the increase of caspase‐3 activity observed after exposure of granule cells to ethanol was also significantly inhibited by TEA. Taken together, the present results demonstrate that, in rat cerebellar granule cells, PACAP reduces the delayed outward rectifier K+ current by activating a type 1 PACAP (PAC1) receptor coupled to the adenylyl cyclase/protein kinase A pathway through a cholera toxin‐sensitive Gs protein. Our data also show that PACAP and TEA induce long‐term depolarization of the resting membrane potential, promote cell survival and inhibit caspase‐3 activity, suggesting that PACAP‐evoked inhibition of IK contributes to the anti‐apoptotic effect of the peptide on cerebellar granule cells.
BDNF and NT‐3 promote thalamocortical axon growth with distinct substrate and temporal dependency
Authors: Hanamura Kenji , Harada Akiko , Katoh‐Semba Ritsuko , Murakami Fujio , Yamamoto Nobuhiko 
Published: April 2004

AbstractThe role of neurotrophins in thalamic axon growth was studied by culturing embryonic rat thalamus on collagen‐coated substrate or fixed cortical slices in the presence of either brain‐derived neurotrophic factor (BDNF) or neurotrophin‐3 (NT‐3). Both BDNF and NT‐3 promoted axonal growth, but the axonal growth‐promoting activity depended on culture substrates. Axonal growth on collagen‐coated membrane was accelerated by BDNF, but not by NT‐3. In contrast, axonal outgrowth on fixed cortex was significantly enhanced by NT‐3, but not by BDNF. Semi‐quantitative reverse transcription‐polymerase chain reaction (RT‐PCR) analysis of cultured thalamic cells demonstrated that culture substrates did not alter the expression of their receptors, trkB and trkC. Terminal deoxynucleotidyl transferase‐mediated dUTP nick end labelling (TUNEL) staining further demonstrated that axonal growth promoted by neurotrophins was not due to reduction of cell death. Measurement of the developmental changes in BDNF and NT‐3 levels revealed that, in contrast to the rapid elevation of BDNF after the arrival of thalamocortical axons to their target layer, the regulation of NT‐3 protein accompanies the phase of their outgrowth in neocortex. These findings suggest that BDNF and NT‐3 promote thalamic axon growth in different manners in terms of substrate dependency and developmental stage.
Repeated acetyl‐l‐carnitine administration increases phospho‐Thr34 DARPP‐32 levels and antagonizes cocaine‐induced increase in Cdk5 and phospho‐Thr75 DARPP‐32 levels in rat striatum
Authors: Scheggi Simona , Rauggi Riccardo , Nanni Giulio , Tagliamonte Alessandro , Gambarana Carla 
Published: April 2004

AbstractAcute cocaine administration increases phosphorylation of dopamine and cAMP‐regulated phosphoprotein (Mr 32 kDa) (DARPP‐32) at threonine (Thr)‐34, whereas repeated cocaine administration increases DARPP‐32 phosphorylation at Thr‐75 in Sprague–Dawley rat striatum. Repeated acetyl‐l‐carnitine (ALCAR) administration persistently increases dopamine outflow in the nucleus accumbens. The present study examined the effect of repeated ALCAR administration on the DARPP‐32 phosphorylation pattern in the nucleus accumbens and caudate‐putamen. ALCAR increased phosphoThr‐34 DARPP‐32 levels and decreased phosphoThr‐75 DARPP‐32 levels, after 1 and 10 days of washout. We compared the effects of repeated cocaine and repeated ALCAR administrations on the behavioural response to cocaine challenge and on the DARPP‐32 phosphorylation pattern and cyclin‐dependent kinase 5 (Cdk5) levels in the striatum. We also studied whether ALCAR administered daily during or after cocaine sensitization procedure would interfere with the effects of cocaine. When the response to the cocaine challenge was assessed, cocaine‐ and ALCAR‐treated rats showed a similar sensitized behavioural response, and rats receiving combined cocaine and ALCAR treatments, irrespective of treatment order, also showed a sensitized response. A week after the cocaine challenge, the two drugs had induced opposite modifications in DARPP‐32 phosphorylation, as cocaine increased phosphorylation at Thr‐75, while ALCAR increased phosphorylation at Thr‐34. In cocaine plus ALCAR treated rats, irrespective of treatment order, ALCAR administration antagonized cocaine effects on DARPP‐32 phosphorylation. Moreover, cocaine, but not ALCAR, increased ΔFosB and Cdk5 expression, and the increase in Cdk5 was antagonized by ALCAR administration in rats receiving combined treatments. These effects were relatively persistent, as they were still present 7 days after the last treatment.
Heterozygous PAX6 mutation, adult brain structure and fronto‐striato‐thalamic function in a human family
Authors: Ellison‐Wright Zoë , Heyman Isobel , Frampton Ian , Rubia Katya , Chitnis Xavier , Ellison‐Wright Ian , Williams Steve C. R. , Suckling John , Simmons Andrew , Bullmore Edward 
Published: April 2004

AbstractRecent progress in developmental neurobiology and neuroimaging can be drawn together to provide new insight into the links between genetically specified processes of embryonic brain development and adult human brain structure and function. We used magnetic resonance imaging (MRI) to show that individuals with aniridia and deficits in executive and social cognition, due to heterozygous mutation of the neurodevelopmental control gene PAX6, have structural abnormalities of grey matter in anterior cingulate cortex, cerebellum and medial temporal lobe, as well as white matter deficits in corpus callosum. Functional MRI demonstrated reduced activation of fronto‐striato‐thalamic systems during performance of overt verbal fluency and nonsense sentence completion; the most consistent abnormality of verbal executive activation was located in the thalamus. These results provide the first evidence for brain functional differences in humans with PAX6 mutation that are compatible both with anatomical abnormalities in the same subjects and, more circumstantially, with the known roles of murine Pax6 in regional differentiation, axonal guidance and other aspects of early forebrain development. Highly conserved homeobox genes may be critical for normal ontogenesis of large‐scale neurocognitive networks supporting phylogenetically advanced mental functions.
NGF and GDNF ameliorate the increase in ATF3 expression which occurs in dorsal root ganglion cells in response to peripheral nerve injury
Authors: Averill Sharon , Michael Gregory J. , Shortland Peter J. , Leavesley Rachel C. , King Von R. , Bradbury Elizabeth J. , McMahon Stephen B. , Priestley John V. 
Published: April 2004

AbstractActivating transcription factor‐3 (ATF3) is a member of the ATF/CREB transcription factor superfamily and is induced in dorsal root ganglion (DRG) cells after nerve injury. In order to study the regulation of ATF3, we have examined the effect of nerve growth factor (NGF) and glial cell line‐derived neurotrophic factor (GDNF) on ATF3 expression. In untreated rats, sciatic nerve transection induced ATF3 immunoreactivity in 82% of L4 DRG cells at 14 days after axotomy. Intrathecal delivery of NGF or GDNF for 2 weeks commencing immediately after injury reduced the ATF3 expression to 35 and 23% of DRG cells, respectively. Cell size analysis indicated that NGF had protected a population of mainly small‐ to medium‐sized cells, but that the GDNF had protected a population of both small and large cells. This effect was confirmed by double labelling for P2X3, CGRP and 200 kDa neurofilament, markers for small peptide‐poor cells, peptide‐rich cells and large cells, respectively. Thus GDNF reduced the percentage of ATF3‐immunoreactive P2X3 cells from 70 to 4%, and the percentage of ATF3‐immunoreactive neurofilament cells from 63 to 24%. NGF was less effective than GDNF in reducing ATF3 expression in these cell types, but reduced the percentage of ATF3‐immunoreactive CGRP cells from 10% to < 1%. These results show that ATF3 expression in specific populations of DRG cells can be modulated by exogenous supplementation of specific trophic factors, and suggest that ATF3 expression may normally be induced by the loss of target‐derived NGF and GDNF.
Enhanced mismatch negativity brain response after binaural word presentation
Authors: Endrass Tanja , Mohr Bettina , Pulvermüller Friedemann 
Published: April 2004

AbstractAn oddball paradigm was used to investigate brain processes elicited by spoken words and pseudowords played monaurally, to the left or right ear, or simultaneously to both ears of human subjects instructed to ignore acoustic stimuli but watch a silent video film. The mismatch negativity (MMN), a neurophysiological index of the automatic activation of cortical memory traces, was calculated as the difference between the event‐related potential elicited by an infrequent deviant stimulus and the event‐related potential to the same item presented as a frequent standard stimulus. Consistent with earlier reports, the MMN to words was larger than that to pseudowords, possibly reflecting the existence of memory traces for spoken words. Bilateral redundant stimulus presentation led to a further increase of the MMN to words relative to both unilateral stimulation modes. This bilateral redundancy gain was absent for pseudowords. We interpret the neurophysiological manifestation of a word‐specific bilateral redundancy gain as evidence for interhemispheric cooperation in the automatic access to memory traces for spoken words. Accordingly, word‐related cortical networks distributed over both hemispheres allow summation of neural activity between and within hemispheres, thereby potentiating the word‐related MMN.
Effects of brain‐derived neurotrophic factor on cell survival, differentiation and patterning of neuronal connections and Müller glia cells in the developing retina
Authors: Pinzón‐Duarte Germán , Arango‐González Blanca , Guenther Elke , Kohler Konrad 
Published: April 2004

AbstractThe aim of the present study was to determine the influence of brain‐derived neurotrophic factor (BDNF) on survival, phenotype differentiation and network formation of retinal neurons and glia cells. To achieve a defined concentration and constant level of BDNF over several days, experiments were performed in an organotypic culture of the developing rat retina. After 6 days in vitro, apoptosis in the different cell layers was determined by TUNEL staining and cell‐type‐specific antibodies were used to identify distinct neuronal cell types and Müller cells. Cultured retinas treated with BDNF (100 ng BDNF/mL medium) were compared with untreated as well as with age‐matched in vivo retinas. Quantitative morphometry was carried out using confocal microscopy. BDNF promoted the in vitro development and differentiation of the retina in general, i.e. the number of cells in the nuclear layers and the thickness of the plexiform layers were increased. For all neurons, the number of cells and the complexity of arborizations in the synaptic layers were clearly up‐regulated by BDNF. In control cultures, the synaptic stratification of cone bipolar cells within the On‐ and Off‐layer of the inner plexiform layer was disturbed and a strong reactivity of Müller cell glia was observed. These effects were not present in BDNF‐treated cultures. Our data show that BDNF promotes the survival of retinal interneurons and plays an important role in establishing the phenotypes and the synaptic connections of a large number of neuronal types in the developing retina. Moreover, we show an effect of BDNF on Müller glia cells.
Neuroprotective effects of vascular endothelial growth factor (VEGF) upon dopaminergic neurons in a rat model of Parkinson's disease
Authors: Yasuhara Takao , Shingo Tetsuro , Kobayashi Kazuki , Takeuchi Akira , Yano Akimasa , Muraoka Kenichiro , Matsui Toshihiro , Miyoshi Yasuyuki , Hamada Hirofumi , Date Isao 
Published: April 2004

AbstractVascular endothelial growth factor (VEGF) has previously been shown to display neuroprotective effects following ischemia, suggesting that VEGF may potentially be applied as a neuroprotective agent for the treatment of other neurological diseases. In this study, we investigated the neuroprotective capacity of VEGF in a model of Parkinson's disease. VEGF was found to be neuroprotective against cell death of primary E14 murine ventral mesencephalic neurons induced by 6‐hydroxydopamine (6‐OHDA) treatment in vitro. Further, rats receiving a continuous infusion of VEGF into the striatum via encapsulated hVEGF‐secreting cells (baby hamster kidney‐VEGF) displayed a significant decrease in amphetamine‐induced rotational behavior and a significant preservation of tyrosine hydroxylase‐positive neurons and fibers compared with control animals. VEGF likely functions via direct mechanisms by signaling through the neuropilin receptor expressed upon dopaminergic neurons in response to 6‐OHDA treatment. Further, VEGF is likely to promote neuroprotection indirectly by activating the proliferation of glia and by promoting angiogenesis. Our results support a potential neuroprotective role for VEGF in the treatment of Parkinson's disease.
Glutamate release increases during mossy‐CA3 LTP but not during Schaffer‐CA1 LTP
Authors: Kawamura Yoshinobu , Manita Satoshi , Nakamura Takeshi , Inoue Masashi , Kudo Yoshihisa , Miyakawa Hiroyoshi 
Published: April 2004

AbstractIt is still a matter of dispute whether the expression of hippocampal long‐term potentiation (LTP) is due to enhanced transmitter release or enhanced postsynaptic sensitivity. Recently we developed a novel method to monitor synaptically released glutamate. In this method, brain slice preparations are stained with a voltage‐sensitive dye RH155 which preferentially stains glial cells, and synaptically induced glial depolarization (SIGD) are optically detected in the presence of the blockers for ionotropic glutamate receptors. We have previously shown that SIGD is due to uptake of synaptically released glutamate by glial glutamate transporters. Here we applied this method to examine change in glutamate release during hippocampal LTP. To examine mossy‐CA3 LTP, stimulating electrodes were placed in dentate gyrus and tetanic stimulation was delivered in the presence of 50 µm APV. The amplitude of SIGD after inducing LTP was significantly greater than that in control experiments in which tetanus was not delivered. The amplitude of SIGD after inducing LTP by a brief (3–5 min) application of 50 µm forskolin was also significantly greater than that in control experiments. At the Schaffer‐CA1 synapse, the change in the amplitude of SIGD during LTP induced either by 100 Hz tetanus LTP or 200 Hz tetanus was not significantly greater than that of control experiments. These results provide evidence for increased glutamate release from the presynaptic terminals as the expression mechanism for both tetanus‐induced and forskolin‐induced LTP at mossy‐CA3 synapses, and evidence supporting a postsynaptic expression mechanism at Schaffer‐CA1 synapses.
Neurogenic and intact or apoptotic non‐neurogenic areas of adult brain release diffusible molecules that differentially modulate the development of subventricular zone cell cultures
Authors: Agasse Fabienne , Roger Michel , Coronas Valérie 
Published: April 2004

AbstractIn the adult mammalian brain, neurogenic activity is maintained in the subventricular zone (SVZ). Damage to non‐neurogenic areas can stimulate SVZ cell proliferation and trigger addition of new neurons in the affected areas. We therefore examined the possible control exerted by specific microenvironment cues on SVZ neurogenic activity. To this end, neonatal SVZ neurospheres were maintained in the presence of diffusible signals derived from the adult neurogenic SVZ or from the non‐neurogenic cerebral cortex either previously treated (apoptotic cortex) or not (untreated cortex) with staurosporine, a known apoptosis inducer. To restrict interactions to soluble signals, the explants were separated from the SVZ neurospheres by a microporous membrane. The results indicated that molecules released by the SVZ itself promoted the expansion of SVZ cell population through increased proliferation and reduced apoptosis. In contrast, untreated cortex factors reduced the expansion of SVZ cell population by decreasing proliferation. In addition, SVZ or untreated cortex factors, respectively, promoted or inhibited neuronal differentiation. Following apoptotic damage, cortex factors no longer inhibited and instead promoted the expansion of the SVZ cell population by increasing proliferation. These effects on cell numbers were replicated following use of culture media conditioned with the different explants but were no longer present following heat inactivation, which indicates that proteins were involved. These findings indicate that the neurogenic SVZ delivers autocrine/paracrine signals that promote neurogenesis whereas the non‐neurogenic cerebral cortex releases signals that inhibit proliferation and neuronal differentiation. Interestingly, this constitutive growth inhibitory effect of the cerebral cortex is inverted following apoptotic lesion.
CD81‐induced behavioural changes during chronic cocaine administration: in vivo gene delivery with regulatable lentivirus
Authors: Bahi Amine , Boyer Frederic , Kafri Tal , Dreyer Jean‐Luc 
Published: April 2004

AbstractCD81, a tetraspanin transmembrane protein involved in cell adhesion, is up‐regulated in the mesolimbic dopaminergic pathway 24 h following acute administration of high doses of cocaine [Brenz‐Verca et al., (2001) Mol. Cell. Neurosci., 17, 303–316]. Further evidence consecutive with this observation and based on microarray analysis are presented here. In addition, a regulatable lentivirus was developed bearing the rat CD81 gene under the control of a tetracycline inducible system. This lentivirus vector was stereotaxically injected into the ventral tegmental area (VTA) of two groups of animals, one fed water (expressing CD81) and the other Doxycycline solution (which down‐regulates CD81 expression) and locomotor activity after chronic cocaine administration (10 mg/kg daily) was monitored. After 2 weeks, the groups were inverted, animals receiving water were placed on Doxycycline and the second group was placed on water. In all cases highly a significant increase (3.2‐fold) in locomotor activity was observed in animals expressing CD81 in the VTA vs. animals placed on Doxycycline. Similar studies where CD81 was delivered into the nucleus accumbens (NAcc) resulted in significantly higher effects (30%), in accordance with microarray data and our previous reports, yielding a 4.2‐fold increase in locomotor activity. No change was observed under similar conditions in control animals, which were injected a regulatable lentivirus expressing GFP. These findings suggest that CD81 expression in the mesolimbic dopaminergic pathway contributes to behavioural changes associated with cocaine sensitization. This study provides a powerful approach for evaluating a gene function in vivo in a single animal under various paradigms, even on gene candidates, which display small changes of expression.