bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ca2+/Calmodulin‐dependent Nitric Oxide Synthase in Apis mellifera and Drosophila melanogaster
Authors: Müller Uli 
Published: April 2006

AbstractNADPH diaphorase (NADPHd) is a marker enzyme for nitric oxide (NO)‐producing cells in vertebrates. This paper investigates the relationship between NADPHd and the NO‐producing enzyme NO synthase (NOS) in neuronal tissue of Apis and Drosophila, two insects used for studying learning. First, the NOS and the NADPHd in both species were characterized biochemically. The fixation‐insensitive NADPHd activity, which accounts for the staining in NADPHd histochemistry, co‐purifies with the insect Ca2+/calmodulin‐dependent NOS. Formation of NO from l‐arginine depends on NADPH, and half‐maximal stimulation is observed with 0.3 μM Ca2+. NOS is competitively inhibited by methyll‐arginine and nitro‐l‐arginine, with Kiof 1.7 and 1.9 μM, respectively. The co‐purification and the competitive inhibition of NOS by the NADPHd substrate, nitro blue tetrazolium (NBT), are proof that in insects the enzyme responsible for fixation‐insensitive NADPHd activity is nitric oxide synthase. Second, the NOS activity was quantified in distinct neuropiles and the NO‐producing neuropiles were visualized using NADPHd histochemistry. In both species the highest NOS activity is found in the chemosensory neuropiles of the antenna1 lobes, intermediate activity in the neuropiles of the central brain and by far the lowest NOS activity in the visual neuropiles. Although in both species the Kenyon cell somata of the mushroom bodies show no detectable staining, the neuropiles of the mushroom bodies of Drosophila and Apis show a distinct staining. The staining pattern of NOS in both species is different to that of all known neurotransmitters.
Opposing Roles for Dopamine D2 and D3 Receptors on Neurotensin mRNA Expression in Nucleus Accumbens
Authors: Diaz J. , Lévesque D. , Griffon N. , Lammers C.H. , Martres M.‐P. , Sokoloff P. , Schwartz J.‐C. 
Published: April 2006

AbstractUsing in situ hybridization histochemistry in rat nucleus accumbens, we show that the dopamine D3 receptor mRNA is expressed in the ventromedial part of the shell subdivision, where its gross distribution matches that of neurotensin mRNA. In addition, hybridization studies at the cellullar level show that a large fraction of the neurotensin neurons co‐express the D3 receptor mRNA in this restricted area. In contrast, the dopamine D2 receptor mRNA is expressed mainly in the core and marginally in the shell, at the level of the cone. In rats treated by haloperidol and sulpiride, two D2‐like receptor antagonists, but not by SCH 23390, a D1‐like receptor antagonist, proneurotensin mRNA was increased in the D2 receptor mRNA‐rich areas but decreased in the D3 receptor mRNA‐rich areas. This suggests that the D2 and D3 receptors control neurotensin mRNA expression negatively and positively, respectively.
Electrotonic Clusters in the Dendritic Arborization of Abducens Motoneurons of the Rat
Authors: Korogod S. , Bras H. , Sarana V. N. , Gogan P. , Tyc‐Dumont S. 
Published: April 2006

AbstractFollowing reconstruction with high spatial resolution of the 3‐D geometry of the dendritic arborizations of two abducens motoneurons, we simulated the distribution of electrotonic voltage over the whole dendritic tree. Here, we demonstrate that the complex stochastic electrotonic structure of both motoneurons can be reduced to a statistically significant small set of well discriminated clusters. These clusters are formed by dendritic branches belonging to different dendrites of the neuron but with similar electrotonic properties. A cluster analysis was performed to estimate quantitatively the partition of the branches between the dendritic clusters. The contents of the clusters were analysed in relation to their stability under different values of specific membrane resistivity (Rm), to their remoteness from the soma and their location in 3‐D space. The cluster analysis was executed in a 2‐D parameter space in which each dendritic branch was described by the mean electrotonic voltage and gradient. The number of clusters was found to be four for each motoneuron when computations were made with Rm= 3 kΩ.cm2. An analysis of the cluster composition under different Rm revealed that each cluster contained invariant and variant branches. Mapping the clusters upon the dendritic geometry of the arborizations allowed us to describe the cluster distribution in terms of the 3‐D space domain, the 2‐D path distance domain and the total surface area of the tree. As the cluster behaviour reflects both the geometry and the changes in the neuronal electrotonic structure, we conclude that cluster analysis provides a tool to handle the functional complexity of the arborizations without losing relevant information. In terms of synaptic activities, the stable dendritic branches in each cluster may process the synaptic inputs in a similar manner. The high percentage of stable branches indicates that geometry is a major factor of stability for the electrotonic clusters. Conversely, the variant branches introduce the conditions for mechanisms of functional postsynaptic plasticity.
Distribution of Nicotinic Receptors in the Human Hippocampus and Thalamus
Authors: Rubboli F. , Court J. A. , Sala C. , Morris C. , Chini B. , Perry E. , Clementi F. 
Published: April 2006

AbstractNeuronal nicotinic acetylcholine receptors consist of different subunits, α and β, with different subtype arrangement corresponding to distinct pharmacological and functional properties. The expression of α3, α7 and β2 mRNA in the human brain was studied by in situ hybridization and compared to [3H]nicotine, [3H]cytisine and [125l]α‐bungarotoxin binding in contiguous sections. The β2 probe showed a strong hybridization signal in the granular layer of the dentate gyrus and in the CA2/CA3 region of the hippocampus and in the insular cortex, and a signal of lower intensity in the subicular complex and entorhinal cortex. The α3 probe showed strong hybridization in the dorsomedial, lateral posterior, ventroposteromedial and reticular nuclei of the thalamus, and a weak signal in the hippocampal region and in the entorhinal, insular and cingular cortex. The amount of α7 mRNA was high at the level of the dentate granular layer and the CA2/CA3 region of the hippocampus, in the caudate nucleus and in the pulvinar and ventroposterolateral nuclei of the thalamus. [3H]Nicotine and [3H]cytisine binding appeared to be identical in anatomical distribution and relative intensity. It was high in the thalamic nuclei, the putamen and in the hippocampal formation in the subicular complex and the stratum lacunosum moleculare. The level of [125l]α‐bungarotoxin binding was particularly high in the hippocampus and in the pyramidal cells of the CA1 region, but was relatively low in the subicular complex. Our data indicate that in the human brain nicotinic receptor subtypes have discrete distributions, which are in part different from those of other species.
Cholera Toxin β Subunit Induces the Differentiation of Human Medulloblastoma Cell Line DEV in a Neuronal Pathway
Authors: Dufay Natalie , Belin Marie‐Françoise , Confavreux Christian , Touraine‐Moulin Françoise , Derrington Edmund A. 
Published: April 2006

AbstractMedulloblastomas are primitive neuroectodermal tumours that are thought to arise from multipotent precursor cells in the cerebellum. Medulloblastoma cells may be undifferentiated or exibit glial, neuronal or ependymal characteristics, suggesting that they may conserve their ability to differentiate in appropriate circumstances. Medulloblastoma cell lines may thus provide models to study the commitment and differentiation of multipotent CNS progenitor cells. A human medulloblastoma cell line, DEV, has previously been shown to differentiate in an astrocytic pathway after infection by the retrovirus HTLV‐1. In this study immunofluorescence flow cytometry shows that cholera toxin β subunit (CTβ), which binds to the ganglioside GM1, induces a twofold increase in the number of DEV cells differentiating towards a neuronal pathway, as shown by the increased proportion and labelling intensity of cells stained by an anti‐neurofilament antibody. Immunocytochemistry shows that after 3 days in culture with CTβ, DEV cells develop processes which stain positive for neurofilaments and MAP‐1. This suggests that CTβ induces DEV cells to express a more neuronal phenotype.
The Contribution of GABA‐mediated Inhibition to Response Properties of Neurons in the Nucleus of the Optic Tract in the Rat
Authors: Schmidt Matthias , Lewald Jörg , van der Togt Chris , Hoffmann Klaus‐Peter 
Published: April 2006

AbstractThe contribution of GABA‐mediated inhibition to the generation of directional selectivity of neurons in the nucleus of the optic tract (NOT) and the dorsal terminal nucleus of the accessory optic system (DTN) was examined in anaesthetized rats by iontophoretic application of the GABAA receptor antagonist bicuculline methiodide. Spontaneous and visually evoked NOT‐DTN cell activities were always increased by bicuculline application. The directional selectivity of NOT‐DTN cells to slowly moving whole‐field stimuli, expressed as the direction index, was reduced for most neurons. However, the difference between firing rates during stimulus movements in the preferred and in the non‐preferred direction did not change systematically. On average, this difference was not significantly affected in the majority of the neurons, although bicuculline more strongly increased the activity during movement in the preferred or non‐preferred direction in some of the neurons. These results indicate that directionally selective neurons in the rat NOT‐DTN receive GABAergic inhibition which is most likely tonic and independent of the stimulus direction.
Involvement of AMPA Receptors in Trigeminal Post‐synaptic Potentials Recorded in Rat Abducens Motoneurons In Vivo
Authors: Ouardouz Mohamed , Durand Jacques 
Published: April 2006

AbstractThe pharmacology of trigeminal excitatory postsynaptic potentials (EPSPs) evoked by electrical stimulation of the vibrissal pad was investigated in vivo in rat abducens motoneurons using intracellular recordings combined with microionophoretic applications of excitatory amino acid agonists [α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionate (AMPA), NMDA, kainate] and a selective non‐NMDA receptor antagonist (GYKI‐52466). Intravenous applications of GYKI‐52466 were also performed during synaptic and amino acid excitations. GYKI‐52466, applied intravenously or microionophoretically, reversibly antagonized AMPA‐induced depolarizations and trigeminal EPSPs in rat abducens motoneurons without affecting NMDA and kainate responses. The inhibition of AMPA‐induced depolarizations was similar following i.v. and ionophoretic applications of GYKI‐52466. Intravenous applications of GYKI‐52466 (0.3–4 mg/kg) reversibly and dose‐dependently reduced trigeminal EPSPs, which could be totally suppressed at the highest doses of GYKI‐52466 (2–4 mg/kg). The antagonist effect, which developed very quickly, could last several minutes and recovered gradually. The effect of GYKI‐52466 on the EPSPs and AMPA responses were compared in the same motoneurons. The partial inhibition of trigeminal EPSPs during microionophoretic applications of GYKI‐52466 was probably due to the distribution of the synapses in the dendritic arborization of abducens motoneurons. Our results show that AMPA receptors are involved in the generation of trigeminal EPSPs in rat abducens motoneurons in vivo.
Cultured Neurons from Mouse Brain Reproduce the Muscarinic Receptor Profile of Their Tissue of Origin
Authors: André C. , Santos G. Dos , Koulakoff A. 
Published: April 2006

AbstractThese studies investigate the regional variations in the muscarinic acetylcholine receptor (mAChR) profiles in neuron populations of the CNS using primary neuron cultures derived from three areas of the mouse brain–the cerebral hemispheres, the mesencephalon and the medulla‐pons–that have distinct mAChR systems. We first assessed the extent to which neurons reproduced their in vivo properties in culture by monitoring the binding capacity, the pharmacological profiles and the levels of mAChR transcripts in neuron cultures and their tissues of origin. We showed that the primary neuron cultures accumulated mAChRs with initial rates similar to those in vivo, had pharmacological profiles very close to those of their area of origin, and accumulated m1, m2, m3, m4 and m5 receptor transcripts according to patterns resembling those in the tissues. We conclude that most of the characteristics of the mAChRs in a given area are proper to the neuron population of that area, that the pattern is established early in ontogenesis, and that it is reproduced in vitro. We also show that the stimulation of phosphoinositide turnover is mediated by mAChRs with distinct pharmacological profiles in neuron cultures from the three brain areas.
Ultrastructural Evidence for Synaptic Interactions between Thalamocortical Axons and Subplate Neurons
Authors: Herrmann Kathrin , Antonini Antonella , Shatz Carla J. 
Published: April 2006

AbstractThalamic axons are known to accumulate in the subplate for a protracted period prior to invading the cortical plate and contacting their ultimate targets, the neurons of layer 4. We have examined the synaptic contacts made by visual and somatosensory thalamic axons during the transition period in which axons begin to leave the subplate and invade the cortical plate in the ferret. We first determined when geniculocortical axons leave the subplate and begin to grow into layer 4 of the visual cortex by injecting 1,1′‐dioctadecyl‐3, 3, 3′, 3′‐tetramethyl indocarbocyanine (Dil) into the lateral geniculate nucleus (LGN). By birth most LGN axons are still confined to the subplate. Over the next 10 days LGN axons grow into layer 4, but many axons retain axonal branches within the subplate. To establish whether thalamic axons make synaptic contacts within the subplate, the anterograde tracer PHA‐L was injected into thalamic nuclei of neonatal ferrets between postnatal day 3 and 12 to label thalamic axons at the electron microscope level. The analysis of the PHA‐L injections confirmed the Dil data regarding the timing of ingrowth of thalamic axons into the cortical plate. At the electron microscope level, PHA‐L‐labelled axons were found to form synaptic contacts in the subplate. The thalamic axon terminals were presynaptic primarily to dendritic shafts and dendritic spines. Between postnatal days 12 and 20 labelled synapses were also observed within layer 4 of the cortex. The ultrastructural appearance of the synapses did not differ significantly in the subplate and cortical plate, with regard to type of postsynaptic profiles, length of postsynaptic density or presynaptic terminal size. These observations provide direct evidence that thalamocortical axons make synaptic contacts with subplate neurons, the only cell type within the subplate possessing mature dendrites and dendritic spines; they also suggest that functional interactions between thalamic axons and subplate neurons could play a role in the establishment of appropriate thalamocortical connections.
Fast Inhibition of Inwardly Rectifying K+ Channels by Multiple Neurotransmitter Receptors in Oligodendroglia
Authors: Karschin Andreas , Wischmeyer Erhard , Davidson Norman , Lester Henry A. 
Published: April 2006

AbstractAn essential function of myelinating oligodendroglia in the mammalian central nervous system is the regulation of extracellular potassium levels by means of a prominent inwardly rectifying K+ current. Cardiac and neuronal K+ inward rectifiers are either activated by hyperpolarizing voltages or controlled by neurotransmitters through the action of receptor‐activated G proteins. Neuromodulation of inward rectifiers has not previously been considered as a way to regulate oligodendrocyte function. Here we report the expression of serotonin, somatostatin and muscarinic acetylcholine G protein‐coupled receptors in rat brain oligodendrocytes. Activation of these receptors leads to pertussis toxin‐sensitive inhibition of inwardly rectifying K+ channels within <1 s. By contrast, in the heart and in neurons, similar pathways activate an inwardly rectifying conductance. Thus, transmitter‐mediated blockade of inward rectifiers appears to be an oligodendrocyte‐specific variation of a common motif for convergent signalling pathways. In vivo, expression of this mechanism, which may be dependent on neuron‐glia signalling, may have a regulatory role in K+ homeostasis during neuron activity in the central nervous system.
The L2/HNK‐1 Carbohydrate is Carried by the Myelin Associated Glycoprotein and Sulphated Glucuronyl Glycolipids in Muscle but not Cutaneous Nerves of Adult Mice
Authors: Löw Karin , Orberger Georg , Schmitz Brigitte , Martini Rudolf , Schachner Melitta 
Published: April 2006

AbstractWe have previously shown that myelinating Schwann cells associated with motor, but not sensory, axons in peripheral nerves of adult mice express the L2/HNK‐1 carbohydrate epitope. This carbohydrate structure carried by glycolipids and neural cell adhesion molecules has been suggested to specifically foster regrowth of motor as opposed to sensory axons after infliction of a lesion. To determine which molecular components may be the carriers of the L2 carbohydrate in motor axon‐associated myelinating Schwann cells, we have isolated the purely sensory, cutaneous branch and the mixed sensory and motor muscle branch of the femoral nerve of adult mice, isolated the myelin fraction thereof and analysed the molecules expressing the L2 carbohydrate by several immunochemical methods. L2 immunoreactivity in myelin of the muscle branch was four to five times higher than that of the cutaneous branch. The 110 kDa L2‐immunoreactive glycoprotein in myelin of the muscle branch, which is not L2‐immunoreactive in the cutaneous branch, was identified as the myelin‐associated glycoprotein by a combination of immunoprecipitation and Western blot analysis. Myelin extraction with organic solvents additionally revealed the two L2‐carrying glycolipids, which amounted to‐40 ng glycolipid/mg dry weight in myelin of the muscle branch, whereas no significant amounts of the L2 glycolipids were found in myelin of the cutaneous branch. These observations suggest an astonishing degree of differential regulation of carbohydrate‐synthesizing activities in myelinating Schwann cells.
Evidence For Two Neurochemical Divisions in the Human Nucleus Accumbens
Authors: Voorn Pieter , Brady Linda S. , Schotte Alain , Berendse Henk W. , Richfield Eric K. 
Published: April 2006

AbstractThe neurochemical anatomy of the human nucleus accumbens was studied by comparing the distributional patterns of [3H]DAMGE (μ opioid receptor), [3H]bremazocine (κ opioid receptor), [3H]SCH‐23390 (D1‐like dopamine receptor), [3H]7‐OH‐DPAT (D3 dopamine receptor) binding, preproenkephalin mRNA and acetylcholinesterase activity in sections of post mortem human striatum. Our results demonstrate the presence of at least two neurochemically distinct divisions within the human nucleus accumbens, which may be homologous to the 'shell’and‘core’divisions of the nucleus as found in the rat.
Ciliary Neurotrophic Factor Enhances the Survival of Purkinje Cells In Vitro
Authors: Lärkfors Lena , Lindsay Ronald M. , Alderson Ralph F. 
Published: April 2006

AbstractWe have examined the effects of ciliary neurotrophic factor (CNTF) on the development of rat Purkinje cells in vitro. Cerebellar cells, derived from embryonic day 16 rat fetuses, were found to respond rapidly to CNTF treatment by induction of c‐Fos protein, such that 40% of the cells were immunopositive after 60 min. Treatment with low doses of CNTF (10‐100 pg/ml) for 8 days resulted in an ∼ 1.6‐fold increase in the number of Purkinje cells, identified by immunohistochemical staining for calbindin. Immunohistochemical staining for other Purkinje cell markers‐cyclic‐GMP‐dependent protein kinase and the low‐affinity nerve growth factor receptor‐verified increased Purkinje cell survival following CNTF treatment. In addition, CNTF increased specific high‐affinity GABA uptake by 45%, and the number of GABAergic neurons by 70%. A maximal increase in the number of Purkinje cells and GABA‐uptake was only achieved if CNTF was added within 48 h of plating the cells, further suggesting that CNTF enhances Purkinje cell survival in vitro. These results taken together strongly support a direct effect of CNTF in promoting the survival of Purkinje cells and possibly other GABAergic cerebellar neurons.
Long‐term Depression in the Hippocampal CA1 Region is Associated with Equal Changes in AMPA and NMDA Receptor‐mediated Synaptic Potentials
Authors: Xiao M.‐Y. , Wigström H. , Gustafsson B. 
Published: April 2006

AbstractIn the CA1 hippocampal region low‐frequency (1‐2 Hz) afferent activation leads to a long‐term depression of excitatory synaptic potentials that is induced by calcium influx through postsynaptic N‐methyl‐d‐aspartate receptor channels. In the present experiments using 2‐ to 3‐week‐old rats, long‐term depressions of field excitatory postsynaptic potentials mediated by amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA) and by N‐methyl‐d‐aspartate receptor channels were examined in parallel, using a perfusion solution containing low concentrations of an AMPA receptor antagonist and of magnesium (0.1 mM). These experiments revealed that long‐term depression was associated with equal relative changes in the two components of the field potential, compatible with a presynaptic location of the expression mechanism for the long‐term depression.
Effects of Monoamines on Transmission from Group II Muscle Afferents in Sacral Segments in the Cat
Authors: Jankowska E. , Läckberg Z. Szabo , Dyrehag L. E. 
Published: April 2006

AbstractThe effects of one 5‐HT1A serotonin agonist (8‐OH‐DPAT) and of two α2 noradrenaline agonists (tizanidine and B‐HT 933) were tested on the transmission between group II muscle afferents and spinal neurons in the sacral segments of the spinal cord in the cat. These agonists have previously been found to depress transmission from group II muscle afferents either in the dorsal horn or in the intermediate zone of midlumbar segments, and this study addressed the question of whether their actions in the sacral segments are similarly selective. The drugs were applied ionophoretically and their effects were tested on field potentials evoked from group II muscle afferents. As judged by changes in the amplitude of the early components of these field potentials, the transmission is effectively depressed by the serotonin agonist (to 56 ± 26% after 2 min of ionophoresis of 8‐OH‐DPAT) but not by the noradrenaline agonists (to 97 ± 12% after 6 min of ionophoresis of B‐HT 933 and to 95 ± 17% after 6 min of ionophoresis of tizanidine). These data suggest that transmission from group II muscle spindle afferents in the sacral segments is under control of serotonin releasing neurons, as in the dorsal horn of midlumbar segments, but leave open the question of the similarities or differences in the mechanisms (pre‐and/or postsynaptic) of this control.