bluuebunny/crossref_metadata_2025_split huggingface dataset:
Trimeric G Proteins Control Regulated Exocytosis in Bovine Chromaffin Cells: Sequential Involvement of Go Associated With Secretory Granules and Gi3 Bound to the Plasma Membrane
Authors: Vitale Nicolas , Gensse Marc , Chasserot‐Golaz Sylvette , Aunis Dominique , Bader Marie‐France 
Published: April 2006

AbstractRegulated secretion requires both calcium and MgATP. Studies in diverse secretory systems indicate that ATP is required to prime the exocytotic apparatus whereas Ca2+ triggers the final ATP‐independent fusion event. In this paper, we examine the possible role of trimeric G proteins in these two steps of exocytosis in chromaffin cells. We show that in the presence of low concentrations of Mg2+, mastoparan selectively stimulates G proteins associated with purified chromaffin granule membranes. Under similar conditions in permeabilized chromaffin cells, mastoparan inhibits ATP‐dependent secretion but is unable to trigger ATP‐independent release. This inhibitory effect of mastoparan on secretion was specifically reversed by anti‐Gαo antibodies and a synthetic peptide corresponding to the carboxyl terminus of Gαo. In contrast, mastoparan required millimolar Mg2+ for the activation of plasma membrane‐bound G proteins and stimulation of ATP‐independent secretion in permeabilized chromaffin cells. The latter effect was completely inhibited by anti‐Gαi3 antibodies and a synthetic peptide corresponding to the carboxyl terminus of Gαi3. By confocal immunofluorescence and immunoreplica analysis, we provide evidence that in chromaffin cells Go is preferentially associated with secretory granules, while Gi3 is essentially present on the plasma membrane. Our findings suggest that these two trimeric G proteins act in series in the exocytotic pathway in chromaffin cells: a secretory granule‐associated Go protein controls the ATP‐dependent priming reaction, whereas a plasma membrane‐bound Gi3 protein is involved in the late calcium‐dependent fusion step, which does not require ATP.
Naturally Occurring (Programmed) and Radiation‐induced Apoptosis are Associated with Selective c‐Jun Expression in the Developing Rat Brain
Authors: Ferrer Isidre , Olivé Montserrat , Ribera Joan , Planas Anna M. 
Published: April 2006

AbstractExpression of the different members of transcription factors Fos and Jun was examined in the developing rat brain. Constitutive expression of c‐Fos, Fos‐related antigens, Jun B and Jun D, as revealed with immunohistochemistry, is higher and more widely distributed in the developing rat brain than in the adult. Selective strong c‐Jun expression is observed in the cytoplasm and nuclei of apoptotic cells during the whole process of naturally occurring (programmed) cell death. Cells expressing strong c‐Jun immunoreactivity are undetermined cells, neurons and astrocytes. Selective c‐Jun expression is also observed following ionizing radiation in rats aged 3 days. Induction of c‐jun mRNA, as revealed with in situ hybridization, occurs between 5 and 15 min following gamma‐irradiation. Strong c‐Jun protein expression appears at 2 h, peaks at 6 h and decreases thereafter to reach normal levels 48 h after gamma‐ray exposure. Strong c‐Jun protein expression is coincidental with endonuclease activation, as revealed with the method of in situ labelling of nuclear DNA fragmentation, and is restricted to apoptotic cells. Cycloheximide injection at the time of irradiation blocks c‐Jun expression, indicating that c‐Jun immunoreactivity is attributable to de novo protein synthesis. These observations demonstrate in vivo selective strong c‐Jun expression associated with programmed cell death and ionizing radiation‐induced apoptosis in the developing rat brain.
Effects of Thyrotropin‐releasing Hormone on GABAergic Synaptic Transmission of the Rat Hippocampus
Authors: Atzori Marco , Nistri Andrea 
Published: April 2006

AbstractThe effect of thyrotropin‐releasing hormone (TRH), a neuropeptide physiologically present in the mammalian hippocampus, on spontaneous, miniature and evoked GABAergic postsynaptic currents was investigated using whole‐cell patch‐clamp recording from pyramidal cells and interneurons of the rat hippocampal thin slice preparation. Bath application of 10 μM TRH induced an increase in the frequency of spontaneous postsynaptic currents from 1.07 ± 0.68 to 3.16 ± 0.73 Hz in pyramidal neurons and interneurons of the stratum lacunosum‐moleculare (SL‐M). In tetrodotoxin solution TRH did not change miniature postsynaptic currents. Application of TRH to minislices containing only the CA1 region still produced an increase in the spontaneous postsynaptic current frequency, indicative of an action by TRH upon a local GABAergic circuitry. Paired recordings from one pyramidal cell and one stratum lacunosum moleculare interneuron displayed synchronous events whose frequency rose after TRH application, suggestive of a common, TRH‐sensitive input. In a small subset of cells TRH induced the appearance of highly rhythmic large postsynaptic currents at a frequency of ∼2 Hz, as confirmed by autocorrelation analysis. Postsynaptic currents electrically evoked by focal stimulation of stratum lacunosum‐moleculare were depressed from 90 ± 27 to 44 ± 15 pA after application of TRH. This phenomenon was solely due to an increase in the number of synaptic failures. It is proposed that the effect of TRH on the GABAergic system was primarily exerted on a subset of interneurons controlling the activity of pyramidal cells as well as stratum lacunosum‐moleculare interneurons.
Spectral Plasticity of H1 Horizontal Cells in Carp Retina: Independent Modulation by Dopamine and Light‐adaptation
Authors: Djamgoz Mustafa B. A. , Fitzgerald Elizabeth M. , Yamada Masahiro 
Published: April 2006

AbstractIt was shown previously that the spectral sensitivity of luminosity/H1 ‐type horizontal cells (HCs) in carp retinae reflects the absorption spectrum of red‐sensitive cones for long wavelengths but can appear highly variable and‘truncated’in the short‐wavelength region of the spectrum. We have found that light‐adaptation sharpened the red‐sensitive spectral peak and decreased the blue/red response amplitude ratio (B/R ratio), mainly by decreasing the response to short‐wavelength stimuli. The adaptation effect was more pronounced for red background light than for blue. During dark adaptation, the B/R ratio increased steadily. Exogenous dopamine (DA; 5 μM) changed the spectral response profile in a similar way to light‐adaptation. However, the effect of light‐adaptation in reducing the B/R ratio was still seen in retinae bathed in 5 μM DA. This effect of background adaptation was also recorded in retinae bathed in 37 μM haloperidol, as well as in retinae pretreated with 6‐hydroxydopamine (i.e. DA‐depleted). The results suggest that (i) short‐wavelength‐sensitive cones play a dynamic role in determining the spectral response profile of H1 HCs and (ii) spectral response characteristics are modulated independently by exogenous DA and an unknown endogenous neuromodulator which is activated by light‐adaptation.
Expression of AMPA‐glutamate Receptor B Subunit in Rat Hippocampal GABAergic Neurons
Authors: Racca Claudia , Catania Maria Vincenza , Monyer Hannah , Sakmann Bert 
Published: April 2006

AbstractThe physiological properties of α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole propionic acid (AMPA)‐type glutamate receptor (GluR) channels are determined by their subunit composition. In particular, the expression of the GluR‐B subunit determines the divalent ion selectivity of the channel. We studied the distribution of GluR‐B mRNA and protein in adult rat hippocampal GABAergic neurons combining non‐radioactive in situ hybridization with immunocytochemistry. The majority of GABAergic hippocampal neurons were GluR‐B mRNA‐positive, but overall the levels of GluR‐B transcript were lower than in pyramidal and granule cells, which showed the highest hybridization signal. The different GluR‐B mRNA expression levels in GABAergic versus principal neurons were also observed at the protein level. There was a paucity of GluR‐B/C immunoreactivity in the vast majority of somata of the GABAergic neurons studied, which contrasted with the strong expression of GluR‐B/C proteins in the hippocampal principal neurons. Our results demonstrate the general low expression of the GluR‐B subunit mRNA and GluR‐B/C proteins in GABAergic hippocampal neurons. Considering the dominant role of the GluR‐B subunit in determining the divalent ion permeability of the receptor, it is likely that most GABAergic neurons express AMPA receptor channels with different calcium permeabilities.
Maintenance of Modality‐specific Connections in the Spinal Cord after Neonatal Nerve Growth Factor Deprivation
Authors: Lewin Gary R. , Mendell Lorne M. 
Published: April 2006

AbstractWe have investigated the properties of antidromically identified lamina I neurons in the rat dorsal horn (in vivo) after neonatal administration of antibody to nerve growth factor (anti‐NGF). Treatment from postnatal day (P) 2 to P9 yielded normal lamina I cell physiology; most cells responded to mechanical nociception and the remainder had a wide dynamic range (WDR). Extending anti‐NGF treatment to P14 reduced the proportion of cells responding to mechanical nociception, increased the proportion of WDR cells, and caused the emergence of cells not driven by cutaneous inputs. Both nociceptive‐specific and WDR cells had larger receptive fields, suggestive of enhanced central action of the remaining nociceptive afferents. These findings cannot be explained by direct action of anti‐NGF on spinal cord neurons since both P2‐9 and P2‐14 treatments should have had similar effects given the time course of development of the blood‐brain barrier. The results are discussed in terms of previous findings indicating normal numbers of D‐hairs and high‐threshold mechanoreceptors (HTMRs) after anti‐NGF treatment from P2 to P9, but a decline in the number of HTMRs and an increase in the number of D‐hairs after treatment from P2 to P14. It is suggested that the reduction in nociceptive neurons and the appearance of neurons not driven by cutaneous stimulation in lamina I results from the reduction in HTMR input. However, D‐hair input to lamina I did not increase despite the larger number of these afferents, suggesting that their central action was regulated to maintain appropriate modality relationships between periphery and centre.
Effects of BDNF and NT‐4/5 on Striatonigral Neuropeptides or Nigral GABA Neurons In Vivo
Authors: Arenas Ernest , Åkerud Peter , Wong Vivien , Boylan Carolyn , Person Håkan , Lindsay Ronald M. , Altar C. Anthony 
Published: April 2006

AbstractSupranigral infusions of the TrkB‐receptor‐preferring neurotrophins BDNF or NT‐4/5 augment locomotor behaviours, pars compacta firing rates and striatal dopamine metabolism. However these actions of BDNF or NT‐4/5 may involve other neurotransmitter systems in addition to dopamine neurons in the substantia nigra. We thus investigated the effects of 2‐week supranigral infusions of BDNF or NT‐4/5 on rat peptidergic striatonigral neurons and nigral GABAergic neurons. Radioimmunoassay revealed that BDNF and NT‐4/5 elevated substantia nigra levels of substance P (by 46 and 57% respectively) and substance K (by 64 and 81%). In addition, BDNF elevated substance K by 59% in a nigral projection area, the superior colliculus. NT‐4/5 elevated dynorphin A in the substantia nigra (by 52%) and met‐enkephalin in substantia nigra and globus pallidus (by 89%). None of these neuropeptides were altered in the striatum. Consistent with these findings, supranigral infusions of BDNF elevated the mRNA for preprotachykinin A in striatal neurons. In the same animals, glutamic acid decarboxylase (GAD)67 mRNA was increased by 48% in the substantia nigra. The cross‐sectional area of GAD67‐positive neuronal somata in the BDNF‐infused nigra was increased by 59%, and 70% of nigral GABAergic neurons had a cross‐sectional area >550 μm2, whereas 95% of the neurons in vehicle‐infused animals had cross‐sectional areas <550 μm2. Thus, supranigral infusions of BDNF or NT‐4/5 increase tachykinin mRNA and protein levels within striatonigral neurons and increase the size and GAD67 mRNA expression levels of nigral GABAergic neurons. These results suggest that BDNF or NT‐4/5 may modify the output of the basal ganglia not only through effects on dopamine neurons but also by increasing neurotransmission in striatonigral peptidergic and nigral GABAergic pathways.
Sex Differentiation of Rat Hippocampal GABAergic Neurons
Authors: Reisert Ingrid , Lieb Klaus , Beyer Cordian , Pilgrim Christof 
Published: April 2006

AbstractIn order to analyse mechanisms of sex differentiation of the hippocampus at the cellular level, the differentiation of hippocampal GABAergic neurons was studied in vitro. Serum‐supplemented and serum‐free dissociated cell cultures were raised from the hippocampus of embryonic day 17 male and female rat embryos for up to 14 days in vitro. This time period roughly corresponds to the critical phase for sex differentiation of the rat brain as determined in vivo. Serum‐free cultures were treated with testosterone and/or 17β‐oestradiol for the entire culture period. Control cultures from male donors contained twice as many GABA‐immunoreactive neurons as those from female donors, while there was no sex difference in overall counts of neurons stained for microtubule‐associated protein 5. Measurements of high‐affinity uptake of [3H]GABA essentially confirmed this sex difference. The development of the sex difference could not be influenced by long‐term treatment with androgen or oestrogen. It is concluded that sex differentiation of a specific subpopulation of hippocampal neurons may take place independently of the environment provided by gonadal steroids and in the absence of extrinsic connections with the hypothalamus or other relays of the limbic circuit.
Production of Monocyte Chemotactic Protein‐1 By Rat Brain Macrophages
Authors: Calvo Charles‐Félix , Yoshirnura Teizo , Gelrnan Michèle , Mallat Michel 
Published: April 2006

AbstractIn the present study, we show that cultured rat brain macrophages release a soluble factor that stimulates the migration of bone marrow‐derived macrophages, as determined by an in vitro chemotaxis assay. A checkerboard analysis indicated that most of this effect resulted from a polarized migration of the cells (chemotactic phenomenon), rather than in an increase in cell motility (chemokinesis). This activity was significantly decreased by an immune serum directed against the rat monocyte chemoattractant protein‐1 (chernokine MCP‐1). Northern blot analysis demonstrated expression of the MCP‐1 gene in cultured brain macrophages, but its absence in unstimulated bone marrow‐derived macrophages. Up‐regulation of MCP‐1 expression was observed when lipopolysaccharide was added to cultured brain macrophages, a peak occurring after a 6 h period of stimulation. Also, inflammatory cytokines such as interleukin (IL)‐1β, colony stimulating factor‐1, tumour necrosis factor‐α and IL‐6 individually increased the basal level of MCP‐1 mRNA. Subsequently, we demonstrated the in vivo production of MCP‐1 in the adult rat brain following injury induced by a local injection of kainic acid. MCP‐1 synthesis was localized in both astrocytes and brain macrophages. These results suggest that the activation of resting microglial cells into brain macrophages and their subsequent secretion of chemokines could contribute to the mechanism(s), leading to the infiltration of the CNS by blood‐derived monocytes, as observed in several pathologies.
Relation Between Cutaneous Receptive Fields and Muscle Afferent Input to Climbing Fibres Projecting to the Cerebellar C3 Zone in the Cat
Authors: Jörntell H. , Garwicz M. , Ekerot C.‐F. 
Published: April 2006

AbstractInferior olivary cells projecting as climbing fibres to the forelimb area of the cerebellar C3 zone were investigated with respect to their cutaneous and muscle afferent input in barbiturate‐anaesthetized cats. Climbing fibre responses were recorded from single cerebellar cortical Purkinje cells on natural stimulation of the skin and on electrical stimulation of nerves to m. biceps brachii, m. triceps brachii and to nine muscles acting as dorsal or palmar flexors of the paw (and, in some cases, the digits). The analysis was focused on the functional organization of convergence between cutaneous and muscle afferents onto single olivary neurons. Cutaneous receptive fields on the dorsal side of the paw and on the digits were generally associated with moderate to strong input from dorsal flexors, but little or no input from palmar flexors or proximal muscles. Receptive fields on the ventral side of the paw and forearm were associated with relatively strong input from biceps and palmar flexors. Climbing fibres with cutaneous receptive fields extending on the ulnar side of the paw and forearm usually received strong input from the triceps and moderate to strong input from dorsal flexors, whereas input from the palmar flexors was weak or lacking. In conclusion, the results indicate that the cutaneous receptive fields in many cases are associated with input from muscles the action of which would tend to move the receptive field towards a stimulus applied to the skin.
Effects of NMDA Receptor Blockade in the Developing Rat Somatosensory Cortex on the Expression of the Glia‐derived Extracellular Matrix Glycoprotein Tenascin‐C
Authors: Mitrovic Nadia , Mohajeri Hasan , Schachner Melitta 
Published: April 2006

AbstractThe patterning of synaptic connections during development is thought to be influenced by the correlation of neuronal impulse activity. N‐methyl‐D‐aspartate (NMDA) receptors have been implicated in the reorganization of thalamocortical afferents in the visual system. The topographic mapping of the periphery of sensory systems onto the somatosensory cortex in the whisker‐barrel field of rodents has served as another important paradigm in the study of extrinsic influences on synaptic rearrangements. In a search for the molecular cues that may contribute to synaptic plasticity, we have investigated the distribution of the glia‐derived extracellular matrix glycoprotein tenascin‐C, which is highly expressed during the formation of the barrel field map around birth and delineates the boundaries between barrel fields after segregation of afferent inputs. Here we show that systemic and local application of NMDA receptor antagonists at postnatal day 2 inhibited the down‐regulation of tenascin mRNA and protein by postnatal day 6 and prevented the appearance of tenascin‐positive barrel field boundaries. Furthermore, barrels were not distinguishable by Nissl staining, and segregation of thalamocortical afferents as monitored by anterograde Dil tracing and acetylcholinesterase histochemistry was not complete. These observations indicate that expression of tenascin‐C and segregation of afferent inputs are modified by NMDA receptor‐dependent neuronal activity.
Chronic Infusion of Nerve Growth Factor into Rat Striatum Increases Cholinergic Markers and Inhibits Striatal Neuronal Discharge Rate
Authors: Förander Petter , Söderström Stine , Humpel Christian , Strömberg Ingrid 
Published: April 2006

AbstractNew strategies have recently been developed where infusion of neurotrophic factors into the brain can rescue different populations of neurons. Infusion of nerve growth factor (NGF) has been used in combination with transplants of chromaffin tissue to the striatum in the rat model of Parkinson's disease as well as to patients suffering from Alzheimer's disease. In this study we have evaluated the distribution of recombinant human NGF (rhNGF) in different brain areas and evaluated morphological and electrophysiological effects after continuous infusion for 2 weeks of rhNGF (500 μg/ml) into the striatum of normal rats. One week after termination of rhNGF infusion, NGF levels in the infused striata were 10‐fold increased while in contralateral striata normal levels were found. Extracellular recordings from striatal neurons revealed a significantly decreased spontaneous firing rate (0.76 ± 0.07 Hz) in rats infused with rhNGF compared to vehicle‐infused control animals (1.36 ± 0.16 Hz). Local application of rhNGF during recordings showed no direct inhibitory effect of NGF on neuronal discharge rate. Immunohistochemistry, using antibodies against acetyl cholinesterase (AChE) and glial fibrillary acidic protein (GFAP), revealed a 38.7 ± 7.0% increase in optical density of AChE immunoreactivity close to the NGF source and an increase in GFAP‐positive profiles that was restricted close to the implanted dialysis fibre. In situ hybridization showed an increase in mRNAs for choline acetyltransferase, trkA, p75 and muscarinic m2 receptor in the large neurons of rhNGF‐infused striatum. Messenger RNAs for m1 and m4 receptors in striatal neurons were not changed. Thus, chronic infusion of rhNGF into the striatum caused a cholinergic hyperinnervation and reduced spontaneous activity of striatal neurons.
Cerebellar Contribution to Spatial Event Processing: Morris Water Maze and T‐maze
Authors: Petrosini Laura , Molinari Marco , Dell'Anna Maria E. 
Published: April 2006

AbstractRecently, a cognitive function of cerebellar networks has been challenging the traditional view of the cerebellum as a motor control centre. Among the cognitive abilities reported to be affected by cerebellar deficits is the capacity to solve a spatial problem. We investigated the influence of a cerebellar lesion on spatial abilities by behavioural analysis of rats that had undergone surgical hemicerebellectomy (HCb; HCbed rats). Experiments were performed with a Morris water maze (MWM) and a water T‐maze in both cue and place versions (visible or hidden platform respectively). Results indicate a severe impairment in coping with spatial information in all phases of MWM testing as well as in the T‐maze paradigm. However, if the MWM cue phase was prolonged, HCbed rats displayed some ability to learn platform position, although at a level significantly different from controls. They succeeded in finding the platform, even in a pure place paradigm, such as finding a hidden platform with the starting points sequentially changed. Retention testing was also performed, demonstrating that HCb affects acquisition but not retention of spatial information. HCbed animals exhibit such disrupted exploration behaviour that they can display only peripheral circling, and they can acquire spatial relations only when proximal cues are available. Furthermore, in all phases of testing, platform finding for HCbed animals is essentially based on place strategies. Thus, a specific pattern of spatial behaviour, markedly different from that displayed following hippocampal or cortical lesions, characterizes cerebellar lesioned rats. These results are discussed taking into account the role in procedural learning recently assigned to cerebellar networks, demonstrating that the cerebellar circuits represent the keystone of the procedural components of spatial event processing.