bluuebunny/crossref_metadata_2025 huggingface dataset:
Reversible Inhibitory Effects of Interferon‐γ and Tumour Necrosis Factor‐α on Oligodendroglial Lineage Cell Proliferation and Differentiation In Vitro
Authors: Agresti Cristina , D'Urso Donatella , Levi Giulio
Published: April 2006

We have investigated the effects of the two prominent inflammatory cytokines, interferon‐γ (IFN‐γ) and tumour necrosis factor‐α (TNF‐α), on oligodendroglial lineage cell development and survival. Purified oligodendrocytes and oligodendrocyte precursors obtained from neonatal rat brain primary cultures were subcultured in a defined, serum‐free medium and exposed to IFN‐γ (1‐100 U/ml), TNF‐α (25‐100 ng/ml) or both (100 U/ml and 50 ng/ml respectively) from day 1 to day 3 or from day 3 to day 6. While cell survival was not affected in any of the conditions tested, IFN‐γ dose‐dependently inhibited [3H]thymidine or bromodeoxyuridine incorporation (by up to 50%) and the reduction of the tetrazolium salt 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT; by up to 33%). TNF‐α synergized with IFN‐γ, but was ineffective by itself. Moreover, IFN‐γ totally antagonized the induction by basic fibroblast growth factor and platelet‐derived growth factor of the proliferation of the oligodendroglial lineage cell population under study. IFN‐γ also blocked the differentiation of oligodendrocyte precursors, as evidenced by cell morphology, immunostaining for early and late differentiation markers (galactocerebroside and myelin basic protein respectively) and activity of ceramide galactosyl transferase. Again, the effect of IFN‐γ was potentiated by TNF‐α, which was ineffective when tested alone. The inhibitory activity of IFN‐γ was rapidly reversible: 3 days after removal of the cytokine, administered from day 1 to day 3, complete recovery of cell proliferation and differentiation could be documented. The cytokine‐induced arrest in the expression of differentiation antigens was accompanied by perturbations in the expression of the corresponding mRNAs, revealed by a semiquantitative reverse transcription‐polymerase chain reaction method. In particular, the message for myelin basic protein (and, in the case of treatment from days 3 to 6, also that for myelin associated glycoprotein) was decreased in cultures exposed to IFN‐γ, and further depressed in cultures treated with IFN‐γ and TNF‐α, while TNF‐α alone was ineffective. The above observations may help explain the role of IFN‐γ and TNF‐α in the pathogenesis of inflammatory demyelinating diseases, in which increases in the levels of these substances have been described. In particular, in the case of multiple sclerosis, our results may bear on the problem of defective remyelination and are consistent with the frequent relapsing‐remitting course of the disease.
The Distribution of Brain‐derived Neurotrophic Factor and its Receptor trkB in Parvlbumin‐containing Neurons of the Rat Visual Cortex
Authors: Cellerino Alessandro , Maffei Lamberto , Domenici Luciano
Published: April 2006

We analysed the distribution of brain‐derived neurotrophic factor (BDNF) and its receptor trkB in the adult rat visual cortex, paying particular attention to a GABAergic neuronal subpopulation—the parvalburnin‐positive cells. We found expression of trkB in the cell body and apical dendrite of pyramidal neurons and in the cell body of non‐pyramidal neurons. Double labelling experiments revealed extensive colocalization of parvalbumin and trkB immunoreactivity in non‐pyramidal neurons. Interestingly, the trkB‐positive pyramidal neurons appeared surrounded by parvalbumin‐labelled boutons. The use of double immunohistochemistry and in situ hybridization histochemistry showed that parvalbumin‐positive neurons express trkB mRNA. BDNF rnRNA was found in several cells. Coexpression of BDNF mRNA and parvalbumin immunoreactivity was extremely rare. These data strongly suggest that BDNF synthesized by cortical neurons acts as a postsynaptically derived factor for parvalbumin‐positive neurons in the adult rat visual cortex.
Glial Cell Line‐derived Neurotrophic Factor: the Lateral Cerebral Ventricle as a Site of Administration for Stimulation of the Substantia Nigra Dopamine System in Rats
Authors: Martin D. , Miller G. , Fischer N. , Dix D. , Cullen T. , Russell D.
Published: April 2006

The direct application of recombinant human glial cell line‐derived neurotrophic factor (rhGDNF) to the deep structures of the nigrostriatum has been shown previously to augment dopamine function and inhibit loss of substantia nigra neurons in rodent models of Parkinson's disease. The present studies were designed to determine whether administration of rhGDNF into the lateral ventricle, a more clinically accessible intracranial target, is capable of augmenting dopamine function of the nigrostriatal pathway in normal rats. Single bolus intracerebroventricular (i.c.v.) injections of rhGDNF increased locomotor activity and decreased food and water consumption and body weight gain in a dose‐dependent manner. rhGDNF increased concentrations of dopamine and dopamine metabolites in the substantia nigra, ventral tegmental area and hypothalamus, but had no significant effects in the striatum. rhGDNF had no effect on striatal or substantia nigral serotonin (5‐HT) and 5‐hydroxyindoleacetic acid levels, but these levels were significantly increased in the ventral tegmental area and hypothalamus respectively. The augmentation of the dopamine and 5‐HT systems was detected 2 weeks but not 3 days or 6 weeks after rhGDNF administration. After a repeat injection of i.c.v. rhGDNF (6 weeks after the initial injection), substantia nigral dopamine, 5‐HIAA and noradrenalin levels were increased. These results indicate that i.c.v. administration of rhGDNF has an influence on adult rat dopamine neurons. This route of administration may be useful for stimulating dopamine neurons in Parkinson's disease.
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

Regulated 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

Expression 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

The 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

It 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

The 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

We 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

Supranigral 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

In 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

In 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

Inferior 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

The 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

New 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

Recently, 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.
Differential Damage to Auditory Neurons and Hair Cells by Ototoxins and Neuroprotection by Specific Neurotrophins in Rat Cochlear Organotypic Cultures
Authors: Zheng J. Lisa , Gao Wei‐Qiang
Published: April 2006

Therapeutic ototoxic drugs are one of the major causes of damage in the peripheral auditory system, leading to hearing loss. In this study, we have examined the toxic actions of three classes of ototoxins (sodium salicylate, gentamicin and cisplatin) in organotypic cultures of postnatal cochlear explants. In these cultures, afferent innervation of hair cells by primary auditory neurons remained intact. Double labelling with a monoclonal antibody against neurofilament protein and a phalloidin‐fluorescein isothiocyanate conjugate revealed that the three types of drugs induced differential damage to auditory neurons and hair cells in the cochlea. While gentamicin preferentially caused hair cell death, sodium salicylate specifically induced degeneration of auditory neurons. In contrast, cisplatin resulted in destruction of both auditory neurons and hair cells. Neuronal degeneration was largely prevented by the addition of neurotrophin‐4/5, brain‐derived neurotrophic factor and neurotrophin‐3 to the culture media together with the ototoxins, while nerve growth factor and other growth factors had no effect. In contrast, the hair cell loss caused by cisplatin or gentamicin was not attenuated by the presence of neurotrophins. These results suggest that ototoxic mechanisms of salicylates, aminoglycosides and chemotherapeutic agents are different. Auditory neuronal loss induced by ototoxins may be prevented by specific neurotrophins.
Phenotype of Striatal Cells Expressing c‐Fos Following Amphetamine Treatment of Rats with Intrastriatal Dopaminergic Grafts
Authors: Abrous D. N. , Bernard V. , Le Moal M. , Bloch B. , Herman J. P.
Published: April 2006

Activation of the nigrostriatal dopaminergic system by psychostimulants such as amphetamine increases c‐Fos expression in the striatum, mostly in the striatonigral substance P‐ergic pathway. This effect is greatly reduced in the neostriatum deprived of dopaminergic afferents. Dopaminergic grafts implanted into the denervated neostriatum restore the reactivity of the striatum to amphetamine. However, the number of striatal neurons expressing c‐Fos is greatly increased in the graft‐bearing striatum compared with the normal striatum. We examined whether this increase in the number of c‐Fos‐expressing neurons corresponds to the recruitment of a new neuronal population, or whether it reflects an increase in the proportion of substance P‐ergic neurons exhibiting activation of c‐Fos. Adult rats received a unilateral 6‐hydroxydopamine lesion of the ascending dopaminergic mesotelencephalic pathway, and a suspension of embryonic mesencephalic neurons was subsequently implanted into the denervated neostriatum. Three months after implantation, animals were injected with d‐amphetamine (5 mg/kg) and killed 2 h later. In the first experiment, striatal sections were processed to visualize both c‐Fos protein, by immunohistochemistry, and preproenkephalin A or substance P, by in situ hybridization. In the second experiment, c‐Fos and neuropeptide Y were visualized on the same sections. In addition, some sections incubated with anti‐c‐Fos antibody were counterstained with toluidine blue in order to determine whether cholinergic neurons were expressing c‐Fos following amphetamine treatment. The density of neurons expressing c‐Fos following amphetamine treatment was three‐fold higher in the graft‐bearing striata than in the striata of control animals. Approximately 75% of the c‐Fos expressing cells were substance P‐ergic in control animals whereas 6% were enkephalinergic and only a few were neuropeptide Y‐ergic or cholinergic. Similar proportions were found in the graft‐bearing striatum, signifying that the pattern of activation of c‐Fos following amphetamine administration is not changed by the graft. Thus, the increased expression of c‐Fos predominantly reflects a graft‐induced increase in the proportion of neurons expressing c‐Fos within the same population of neurons which normally expresses c‐Fos in the striatum, i.e. the striatonigral substance P‐ergic neurons; there is no recruitment of a new neuronal population. This increased activation of the striatonigral substance P‐ergic pathway may underlie the abnormal behavioural reactions brought about by amphetamine‐induced stimulation of the implanted dopaminergic neurons.
Synapsin‐like Molecules in Aplysia punctata and Helix pomatia: Identification and Distribution in the Nervous System and During the Formation of Synaptic Contacts In Vitro
Authors: Cibelli Giuseppe , Ghirardi Mirella , Onofri Franco , Casadio Andrea , Benfenati Fabio , Montarolo Pier Giorgio , Vitiello Francesco
Published: April 2006

The distribution and biochemical features of the synapsin‐like peptides recognized in Aplysia and Helix by various antibodies directed against mammalian synapsins were studied. The peptides can be extracted at low pH and are digested by collagenase; further, they can be phosphorylated by both protein kinase A and Ca2+/calmodulin‐dependent protein kinase II. In the ganglia of both snails, they are associated with the soma of most neurons and with the neuropil; punctate immunostaining is present along the neurites. Using cocultures of a Helix serotoninergic neuron and of its target cell, we analysed the redistribution of the synapsin‐like peptides during the formation of active synaptic contacts. When the presynaptic neuron is plated in isolation, both synapsin and serotonin immunoreactivities are restricted to the distal axonal segments and to the growth cones; in the presence of the target, the formation of a chemical connection is accompanied by redistribution of the synapsin and serotonin immunoreactivities that concentrate in highly fluorescent round spots scattered along the newly grown neurites located close to the target cell. Almost every spot that is stained for serotonin is also positive for synapsin. In the presynaptic cell plated alone, the number of these varicosity‐like structures is substantially stable throughout the whole period; by contrast, when the presynaptic cell synapses the target, their number increases progressively parallel to the increase in the mean amplitude of cumulative excitatory postsynaptic potentials recorded at the same times. The data indicate that mollusc synapsin‐like peptides to some extent resemble their mammalian homologues, although they are not exclusively localized in nerve terminals and their expression strongly correlates with the formation of active synaptic contacts.
Effects of High Helium Pressure on Intracellular and Field Potential Responses in the CA1 Region of the In Vitro Rat Hippocampus
Authors: Southan A. P. , Wann K. T.
Published: April 2006

We have investigated the effects of high helium pressure (up to 13.3 MPa) on the electrophysiological responses of CA1 neurons in rat hippocampal slices using a purpose built pressure chamber, designed to facilitate field potential and intracellular recording. In field potential experiments, near threshold orthodromic responses were depressed by modest pressure (0.4 MPa). At higher stimulus intensities, orthodromic and antidromic population spike amplitudes were not increased at 5 MPa but were significantly enhanced at 10 MPa, and multiple population spikes were observed in some experiments. Orthodromic paired pulse potentiation was not affected by pressure up to 10 MPa. In intracellular experiments there were no significant differences between mean values obtained for resting membrane potential and input resistance at atmospheric pressure and pressures of up to 10 MPa. However, spontaneous depolarizing membrane potential excursions, decreased slow after‐hyperpolarization responses and reduced accommodation properties were observed at pressure (5–10 MPa). One possibility is that the SK and M potassium channel systems may be more sensitive to high pressure than other membrane ion channels. These effects may contribute towards the high pressure neurological syndrome observed in vivo.
7‐OH‐DPAT Differentially Reverses Clozapine‐ and Haloperidol‐induced Increases in Fos‐like Immunoreactivity in the Rodent Forebrain
Authors: Vahid‐Ansari F. , Robertson G. S.
Published: April 2006

The pattern of neurons which display haloperidol‐induced Fos‐like immunoreactivity closely matches the distribution of striatal D2 dopamine receptors, whereas clozapine‐induced Fos‐like immunoreactivity occurs primarily in regions that contain high levels of the D3 dopamine receptor. These neuroanatomical correlations suggest that haloperidol and clozapine may elevate Fos‐like immunoreactivity by blocking D2 and D3 receptors respectively. In order to test this hypothesis, the abilities of prior administration of the D3 receptor‐preferring agonist 7–hydroxy‐N, N′‐di‐n‐propyl‐2‐aminotetraline (7–OH‐DPAT) to competitively reverse haloperidol‐ and clozapine‐induced increases in Fos‐like immunoreactivity were compared. Administration of 7–OH‐DPAT (0.05 mg/kg, s.c.) 30 min before clozapine (20 mg/kg, s.c.) produced a 60% reduction in the number of neurons that displayed clozapine‐induced Fos‐like immunoreactivity in the major island of Calleja, nucleus accumbens and medial aspect of the striatum, while prior administration of 0.5 mg/kg (s.c.) of 7‐OH‐DPAT completely reversed these increases in Fos‐like immunoreactivity. In contrast, the increases in Fos‐like immunoreactivity in the major island of Calleja, nucleus accumbens and striatum (medial and dorsal aspects) induced by haloperidol (0.1 mg/kg, s.c.) were only reduced by the high dose of 7‐OH‐DPAT (0.5 mg/kg, s.c.). Hence, clozapine‐induced increases in Fos‐like immunoreactivity were more readily reversed by 7‐OH‐DPAT than elevations in Fos‐like immunoreactivity produced by haloperidol. These results suggest that D3 receptor blockade plays a larger role in mediating clozapine‐ than haloperidol‐induced increases in Fos‐like immunoreactivity.
Altered Gene Expression of the N‐Methyl‐d‐Aspartate Receptor Channel Subunits in Purkinje Cells of the Staggerer Mutant Mouse
Authors: Nakagawa Shin , Watanabe Masahiko , Inoue Yoshiro
Published: April 2006

The gene expression of five NMDA receptor channel subunits, the ɛ1 ɛ2, epsiv;3, ɛ4 and ζ1 subunits, was examined in cerebellar Purkinje cells of the staggerer mouse at postnatal day 21. In the midline region of the staggerer cerebellum, signals for the ɛ1, ɛ4, and ζ1 subunit mRNAs were distributed in Purkinje cells, which have a large cell body aligned in a monolayer between the granular and molecular layers. In addition to the midline region, labelled neurons in the intermediate cerebellar region were, though at lower levels, aligned almost in a monolayer between the granular and molecular layers. In the hemisphere, most labelled neurons occurred in various locations in the granular layer and the cerebellar medulla. These regions, populated with Purkinje cells expressing the ɛl, ɛ4, and ζ1 subunit mRNAs, were separated from each other by narrow gap regions that contained neurons without any detectable NMDA receptor channel subunit mRNAs. These results suggest that there is discrete mediolateral heterogeneity in staggerer Purkinje cell populations, in terms of expression properties of the NMDA receptor channel subunits. When compared with wild‐type Purkinje cells that express the ζ1 subunit alone, additional expression of the E subunits presumably explains the persistence of NMDA responses in adult staggerer Purkinje cells (Dupont et al Neuroscience, 12, 613‐619, 1984).
Injury‐induced Synthesis and Release of Apolipoprotein E and Clusterin from Rat Neural Cells
Authors: Messmer‐Joudrier S. , Sagot Y. , Mattenberger L. , James R. W. , Kato A. C.
Published: April 2006

Apolipoproteins in the brain have assumed major clinical importance since it was shown that one of the allelic forms of apolipoprotein E, apoE‐4, is a risk factor for Alzheimer's disease. Using tissue culture of embryonic rat spinal cord, we examined the effect of neuronal injury on the up‐regulation of two s apolipoproteins, apolipoprotein E and clusterin (apoJ). In order to study the influence of neuronal cells, we exploited the specific neurotoxic effect of elevated glutamate on these cells. Overstimulation by excess glutamate induced neuronal degeneration as assessed by morphological and biochemical criteria, notably the activity of choline acetyltransferase, which serves as a marker for cholinergic neurons. High concentrations of glutamate increased mRNA synthesis and the production and secretion of both apolipoprotein E and clusterin protein. Both neuronal cell death and release of the peptides were calcium‐dependent and could be blocked by the NMDA receptor antagonist MK‐801. Immunohistochemical data revealed the presence of clusterin in both neuronal and non‐neuronal cells whereas apolipoprotein E was mainly expressed in non‐neuronal cells. The results are suggestive of concerted up‐regulation of apolipoprotein E and clusterin when neural cells are subjected to injury.
Postsynaptic Currents and Short‐term Synaptic Plasticity in Purkinje Cells Grafted onto an Uninjured Adult Cerebellar Cortex
Authors: Tempia Filippo , Bravin Monica , Strata Piergiorgio
Published: April 2006

It has been shown recently that embryonic Purkinje cells grafted extraparenchymally into an intact cerebellum, in the absence of any sign of damage, are able to migrate into the host molecular layer where they receive a climbing fibre innervation. Using the same technique, we investigated the development of the electrophysiological properties of the synapses between the grafted cells and their main afferents. Purkinje cells either in the graft or having migrated into the molecular layer of the host were recorded using the whole‐cell patch‐clamp method in acutely prepared slices 17–112 days after grafting. Spontaneous postsynaptic currents with a single‐exponential decay and mediated by GABAA receptors were very similar to those described in normal Purkinje cells. Excitatory postsynaptic currents (EPSCs) evoked by climbing fibre and by parallel fibre stimulation were blocked by an α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole‐propionic acid (AMPA)/kainate antagonist, and displayed the linear current‐voltage relation typical of postnatal Purkinje cells. The attainment of normal functional properties by the adult axons at the newly formed synaptic sites was shown by the expression of short‐term facilitation of parallel fibre EPSCs and of short‐term depression of climbing fibre EPSCs. The grafted Purkinje cells showed climbing fibre polyinnervation 17‐20 days after grafting which evolved to monoinnervation at 23‐45 days, confirming the completion of the developmental programme up to maturation. Our experiments support the view that the adult intact brain is able to accept and integrate an additional number of neurons which show fully mature electrophysiological properties which are electrophysiologically indistinguishable from those of the host neurons.
Status Epilepticus Causes Selective Regional Damage and Loss of GABAergic Neurons in the Rat Amygdaloid Complex
Authors: Tuunanen Jarkko , Halonen Toivo , Pitkänen Asla
Published: April 2006

In human epilepsy, the amygdala is often a primary focus for seizures. To analyse the status epilepticus‐induced alterations in the amygdaloid circuitries which may later underlie epileptogenesis, we studied the amygdaloid damage in kainic acid and perforant pathway stimulation models of status epilepticus in the rat. We also studied the damage to inhibitory GABAergic neurons. In both models, the medial division of the lateral nucleus, the parvicellular division of the basal nucleus and portions of the anterior cortical and medial nuclei were damaged. In the kainate model, where the seizure activity was more severe, the accessory basal nucleus, amygdalohippocampal area, posterior cortical nucleus and periamygdaloid cortex were also damaged. Two weeks after kainate‐induced seizures, 56% of the GABA‐immunoreactive neurons remained in the lateral nucleus (P < 0.05) and 25% in the basal nucleus (P < 0.01). Further analysis showed that one subpopulation of damaged GABAergic neurons was immunoreactive for somatostatin (48% remaining in the lateral nucleus, P < 0.01; 33% in the basal nucleus, P < 0.01). In the perforant pathway stimulation model, the damage to somatostatin neurons was milder. According to our data, the initial insult, such as status epilepticus, selectively damages amygdaloid nuclei. The loss of inhibition may underlie the spontaneous generation of seizures and epileptogenesis. On the other hand, many amygdaloid output nuclei (magnocellular and intermediate division of the basal nucleus, the central nucleus) remained relatively undamaged, providing pathways for seizure spread and generation of seizure‐related behavioural manifestations such as motor convulsions and fear response.
Micro‐Organization of Olivocerebellar and Corticonuclear Connections of the Paravermal Cerebellum in the Cat
Authors: Garwicz M. , Apps R. , Trott J. R.
Published: April 2006

The olivocerebellar and corticonuclear connections of the forelimb area of the paravermal medial C3 zone were studied in the cat using a combined electrophysiological and fluorescent tracer technique. During an initial operation under barbiturate anaesthesia, lobules IV/V of the cerebellar anterior lobe were exposed and small injections of dextran amines tagged with rhodamine or fluorescein were made into areas selected from four different electrophysiologically defined parts of the zone. The inferior olive and the deep cerebellar nuclei were then scrutinized for retrogradely labelled cells and anterogradely labelled axon terminals respectively. The findings demonstrate a detailed topographical organization within the olivocerebellar projection to the medial C3 zone and provide some evidence for a topographical organization of its projection to nucleus interpositus anterior. Both projections are described at a level of resolution not previously attained in neuroanatomical studies and the results strongly support the notion of a micro‐compartmentalization of cerebellar olivo‐corticonuclear circuits.