Brain Slices (brain + slice)

Distribution by Scientific Domains
Distribution within Life Sciences

Kinds of Brain Slices

  • acute brain slice
  • hippocampal brain slice
  • rat brain slice

  • Terms modified by Brain Slices

  • brain slice preparation

  • Selected Abstracts


    Mechanisms underlying the inability to induce area CA1 LTP in the mouse after traumatic brain injury

    HIPPOCAMPUS, Issue 6 2006
    E. Schwarzbach
    Abstract Traumatic brain injury (TBI) is a significant health issue that often causes enduring cognitive deficits, in particular memory dysfunction. The hippocampus, a structure crucial in learning and memory, is frequently damaged during TBI. Since long-term potentiation (LTP) is the leading cellular model underlying learning and memory, this study was undertaken to examine how injury affects area CA1 LTP in mice using lateral fluid percussion injury (FPI). Brain slices derived from FPI animals demonstrated an inability to induce LTP in area CA1 7 days postinjury. However, area CA1 long-term depression could be induced in neurons 7 days postinjury, demonstrating that some forms of synaptic plasticity can still be elicited. Using a multidisciplined approach, potential mechanisms underlying the inability to induce and maintain area CA1 LTP were investigated. This study demonstrates that injury leads to significantly smaller N -methyl- D -aspartate potentials and glutamate-induced excitatory currents, increased dendritic spine size, and decreased expression of ,-calcium calmodulin kinase II. These findings may underlie the injury-induced lack of LTP and thus, contribute to cognitive impairments often associated with TBI. Furthermore, these results provide attractive sites for potential therapeutic intervention directed toward alleviating the devastating consequences of human TBI. © 2006 Wiley-Liss, Inc. [source]


    Neuroprotective effect of chronic lithium treatment against hypoxia in specific brain regions with upregulation of cAMP response element binding protein and brain-derived neurotrophic factor but not nerve growth factor: comparison with acute lithium treatment

    BIPOLAR DISORDERS, Issue 3 2008
    N Omata
    Objectives:, We evaluated the neuroprotective effect of chronically or acutely administered lithium against hypoxia in several brain regions. Furthermore, we investigated the contribution of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), and cAMP response element binding protein (CREB) to the neuroprotective effect of lithium. Methods:, Brain slices were prepared from rats that had been treated chronically or acutely with lithium. The cerebral glucose metabolic rate (CMRglc) before and after hypoxia loading to brain slices was measured using the dynamic positron autoradiography technique with [18F]2-fluoro-2-deoxy- d -glucose. The changes of expression of proteins were investigated using Western blot analysis. Results:, Before hypoxia loading, the CMRglc did not differ between the lithium-treated and untreated groups. After hypoxia loading, the CMRglc of the untreated group was significantly lower than that before hypoxia loading. However, the CMRglc of the chronic lithium treatment group recovered in the frontal cortex, caudate putamen, hippocampus and cerebellum, but not in the thalamus. In contrast, the CMRglc of the acute lithium treatment group did not recover in any analyzed brain regions. After chronic lithium treatment, the levels of expression of BDNF and phospho-CREB were higher than those of untreated rats in the frontal cortex, but not in the thalamus. However, the expression of NGF did not change in the frontal cortex and thalamus. Conclusions:, These results demonstrated that lithium was neuroprotective against hypoxia only after chronic treatment and only in specific brain regions, and that CREB and BDNF might contribute to this effect. [source]


    Blood,brain barrier damage and brain penetration of antiepileptic drugs: Role of serum proteins and brain edema

    EPILEPSIA, Issue 4 2009
    Nicola Marchi
    Summary Purpose:, Increased blood,brain barrier (BBB) permeability is radiologically detectable in regions affected by drug-resistant epileptogenic lesions. Brain penetration of antiepileptic drugs (AEDs) may be affected by BBB damage. We studied the effects of BBB damage on brain distribution of hydrophilic [deoxy-glucose (DOG) and sucrose] and lipophilic (phenytoin and diazepam) molecules. We tested the hypothesis that lipophilic and hydrophilic drug distribution is differentially affected by BBB damage. Methods:, In vivo BBB disruption (BBBD) was performed in rats by intracarotid injection of hyperosmotic mannitol. Drugs (H3-sucrose, 3H-deoxy-glucose, 14C-phenytoin, and C14-diazepam) or unlabeled phenytoin was measured and correlated to brain water content and protein extravasation. In vitro hippocampal slices were exposed to different osmolarities; drug penetration and water content were assessed by analytic and densitometric methods, respectively. Results:, BBBD resulted in extravasation of serum protein and radiolabeled drugs, but was associated with no significant change in brain water. Large shifts in water content in brain slices in vitro caused a small effect on drug penetration. In both cases, total drug permeability increase was greater for lipophilic than hydrophilic compounds. BBBD reduced the amount of free phenytoin in the brain. Discussion:, After BBBD, drug binding to protein is the main controller of total brain drug accumulation. Osmotic BBBD increased serum protein extravasation and reduced free phenytoin brain levels. These results underlie the importance of brain environment and BBB integrity in determining drug distribution to the brain. If confirmed in drug-resistant models, these mechanisms could contribute to drug brain distribution in refractory epilepsies. [source]


    Neuroprotective Strategies to Avert Seizure-Induced Neurodegeneration in Epilepsy

    EPILEPSIA, Issue 2007
    Janice R. Naegele
    Summary:, Neurodegeneration in limbic circuits is a hallmark feature of chronic temporal lobe epilepsy (TLE). Studies in experimental animal models and human patients indicate that seizure-induced neuronal injury involves some active, as well as passive cell death processes. Experimental approaches that inhibit active steps in cell death programs have been shown to reduce neuronal cell death and sclerosis, but not to prevent epileptogenesis in animal models of TLE. These findings suggest that we need additional research using both animal models and brain slices from human patients to understand the pathological mechanisms underlying seizure generation. Such comparative studies will also aid in evaluating the potential therapeutic value of inhibiting cell death in seizure disorders. [source]


    Epileptiform Activity Induced by Pharmacologic Reduction of M-Current in the Developing Hippocampus in Vitro

    EPILEPSIA, Issue 1 2006
    Fernando Peña
    Summary:,Purpose: Benign familial neonatal convulsions (BFNCs), an inheritable epilepsy that occurs in neonates but not in adults, is caused by hypofunctional mutations in genes codifying for the M-type K+ current. In an attempt to develop an in vitro model of this disease, we tested whether blocking M-current with linopirdine induces epileptiform activity in brain slices from animals of different ages. Methods: Horizontal hippocampus,entorhinal cortex slices were obtained from neonatal (1,2 weeks after birth) and adult (8,9 weeks after birth) rats. Extracellular field recordings of the CA1 region were performed. After recording control conditions, linopirdine was added to the bath, and field activity was recorded continuously for 3 h. 4-Aminopyridine, a drug commonly used to induce epileptiform activity in vitro, was used as a control for our experimental conditions. Results: Bath perfusion of linopirdine induced epileptiform activity only in slices from neonatal rats. Epileptiform activity consisted of interictal-like and ictal-like activity. In slices from adult rats, linopirdine induced erratic interictal-like activity. In contrast, 4-aminopyridine was able to induce epileptiform activity in slices from both neonatal and adult rats. Conclusions: We demonstrated that blockade of M-current in vitro produces epileptiform activity with a developmental pattern similar to that observed in BNFCs. This could be an in vitro model that can be used to study the cellular mechanisms of epileptogenesis and the developmental features of BFNCs, as well as to develop some therapeutic strategies. [source]


    Distribution and Initiation of Seizure Activity in a Rat Brain with Subcortical Band Heterotopia

    EPILEPSIA, Issue 5 2000
    Zong-Fu Chen
    Summary: Purpose: Misplaced (heterotopic) cortical neurons are a common feature of developmental epilepsies. To better understand seizure disorders associated with cortical heterotopia, the sites of aberrant discharge activity were investigated in vivo and in vitro in a seizure-prone mutant rat (tish) exhibiting subcortical band heterotopia. Methods: Depth electrode recordings and postmortem assessment of regional c- fos mRNA levels were used to characterize the distribution of aberrant discharge activity during spontaneous seizures in vivo. Electrophysiologic recordings of spontaneous and evoked activity also were performed by using in vitro brain slices from the tish rat treated with proconvulsant drugs (penicillin and 4-aminopyridine). Results: Depth electrode recordings demonstrate that seizure activity begins almost simultaneously in the normotopic and heterotopic areas of the tish neocortex. Spontaneous seizures induce c- fos mRNA in normotopic and heterotopic neocortical areas, and limbic regions. The threshold concentrations of proconvulsant drugs for inducing epileptiform spiking were similar in the normotopic and heterotopic areas of tish brain slices. Manipulations that blocked communication between the normotopic and heterotopic areas of the cortex inhibited spiking in the heterotopic, but not the normotopic, area of the cortex. Conclusions: These findings indicate that aberrant discharge activity occurs in normotopic and heterotopic areas of the neocortex, and in certain limbic regions during spontaneous seizures in the tish rat. Normotopic neurons are more prone to exhibit epileptiform activity than are heterotopic neurons in the tish cortex, and heterotopic neurons are recruited into spiking by activity initiated in normotopic neurons. The findings indicate that seizures in the tish brain primarily involve telencephalic structures, and suggest that normotopic neurons are responsible for initiating seizures in the dysplastic neocortex. [source]


    Lanthanide-Based Conjugates as Polyvalent Probes for Biological Labeling

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2008
    Stéphanie Claudel-Gillet
    Abstract A series of lanthanide complexes of [LnL(H2O)] composition, suitable for biological labeling has been studied, in which L is a strongly chelating ligand containing chromophoric bipyridylcarboxylate units and Ln = Sm, Eu, Gd, Tb, and Dy. For the Gd complex, a combined 17O NMR and 1H NMRD study has been performed. The water exchange rate obtained, kex298 = (5.2,±,0.6),×,106 s,1, is slightly higher than those for [Gd(dota)(H2O)], or [Gd(dtpa)(H2O)]2,. Transformation of the uncoordinated carboxylate function of the ligand into an activated ester ensures covalent linking of the complex to bovine serum albumine (BSA). The relaxivity properties of the Gd complex labeled on BSA revealed a limited increase of both longitudinal and transversal relaxivities. This can be related to the partial replacement of the inner-sphere water molecules by coordinating functions of the protein. Additionally, the Sm and Dy complexes are described and chemically characterized. Their photophysical properties were investigated by means of absorption, steady-state and time-resolved spectroscopy, evidencing efficient photosensitization of the lanthanide emission by ligand excitation (antenna effect). Luminescence lifetime measurements confirmed the presence of a water molecule in the first coordination sphere that partly explained the relatively poor luminescence properties of the Dy and Sm complexes in aqueous solutions. The spectroscopic properties of the series of complexes are questioned in terms of time-resolved acquisition techniques. Finally, their availability for use in time-resolved luminescence microscopy is demonstrated by staining experiments of rat brain slices, where the complex showed enhanced localization in some hydrophilic regions of the blood,brain barrier (BBB).(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]


    Tissue-type plasminogen activator-plasmin-BDNF modulate glutamate-induced phase-shifts of the mouse suprachiasmatic circadian clock in vitro

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2009
    Xiang Mou
    Abstract The mammalian circadian clock in the suprachiasmatic nucleus (SCN) maintains environmental synchrony through light signals transmitted by glutamate released from retinal ganglion terminals. Brain-derived neurotrophic factor (BDNF) is required for light/glutamate to reset the clock. In the hippocampus, BDNF is activated by the extracellular protease, plasmin, which is produced from plasminogen by tissue-type plasminogen activator (tPA). We provide data showing expression of proteins from the plasminogen activation cascade in the SCN and their involvement in circadian clock phase-resetting. Early night glutamate application to SCN-containing brain slices resets the circadian clock. Plasminogen activator inhibitor-1 (PAI-1) blocked these shifts in slices from wild-type mice but not mice lacking its stabilizing protein, vitronectin (VN). Plasmin, but not plasminogen, prevented inhibition by PAI-1. Both plasmin and active BDNF reversed ,2 -antiplasmin inhibition of glutamate-induced shifts. ,2 -Antiplasmin decreased the conversion of inactive to active BDNF in the SCN. Finally, both tPA and BDNF allowed daytime glutamate-induced phase-resetting. Together, these data are the first to demonstrate expression of these proteases in the SCN, their involvement in modulating photic phase-shifts, and their activation of BDNF in the SCN, a potential ,gating' mechanism for photic phase-resetting. These data also demonstrate a functional interaction between PAI-1 and VN in adult brain. Given the usual association of these proteins with the extracellular matrix, these data suggest new lines of investigation into the locations and processes modulating mammalian circadian clock phase-resetting. [source]


    Vasopressin modulates lateral septal network activity via two distinct electrophysiological mechanisms

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 9 2007
    G. Allaman-Exertier
    Abstract The lateral septal area is rich in vasopressin V1A receptors and is densely innervated by vasopressinergic axons, originating mainly from the bed nucleus of the stria terminalis and the amygdala. Genetic and behavioral studies provide evidence that activation of vasopressin receptors in this area plays a determinant role in promoting social recognition. What could be the neuronal mechanism underlying this effect? Using rat brain slices and whole-cell recordings, we found that lateral septal neurons are under the influence of a basal GABAergic inhibitory input. Vasopressin, acting via V1A but not V1B receptors, greatly enhanced this input in nearly all neurons. The peptide had no effect on miniature inhibitory postsynaptic currents, indicating that it acted on receptors located in the somatodendritic membrane, rather than on axon terminals, of GABAergic interneurons. Cell-attached recordings showed that vasopressin can cause a direct excitation of a subpopulation of lateral septal neurons by acting via V1A but not V1B receptors. The presence in the lateral septum of V1A but not of V1B receptors was confirmed by competition binding studies using light microscopic autoradiography. In conclusion, vasopressin appears to act in the lateral septum in a dual mode: (i) by causing a direct excitation of a subpopulation of neurons, and (ii) by causing an indirect inhibition of virtually all lateral septal neurons. This modulation by vasopressin of the lateral septal circuitry may be part of the neuronal mechanism by which the peptide, acting via V1A receptors, promotes social recognition. [source]


    Estrogen modulates neuronal movements within the developing preoptic area,anterior hypothalamus

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 5 2007
    John Gabriel Knoll
    Abstract The preoptic area,anterior hypothalamus (POA-AH) is characterized by sexually dimorphic features in a number of vertebrates and is a key region of the forebrain for regulating physiological responses and sexual behaviours. Using live-cell fluorescence video microscopy with organotypic brain slices, the current study examined sex differences in the movement characteristics of neurons expressing yellow fluorescent protein (YFP) driven by the Thy-1 promoter. Cells in slices from embryonic day 14 (E14), but not E13, mice displayed significant sex differences in their basal neuronal movement characteristics. Exposure to 10 nm estradiol-17, (E2), but not 100 nm dihydrotestosterone, significantly altered cell movement characteristics within minutes of exposure, in a location-specific manner. E2 treatment decreased the rate of motion of cells located in the dorsal POA-AH but increased the frequency of movement in cells located more ventrally. These effects were consistent across age and sex. To further determine whether early-developing sex differences in the POA-AH depend upon gonadal steroids, we examined cell positions in mice with a disruption of the steroidogenic factor-1 gene, in which gonads do not form. An early-born cohort of cells were labelled with the mitotic indicator bromodeoxyuridine (BrdU) on E11. More cells were found in the POA-AH of females than males on the day of birth (P0) regardless of gonadal status. These results support the hypothesis that estrogen partially contributes to brain sexual dimorphism through its influence on cell movements during development. Estrogen's influence may be superimposed upon a pre-existing genetic bias. [source]


    Muscarine activates the sodium,calcium exchanger via M3 receptors in basal forebrain neurons

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2006
    Changqing Xu
    Abstract Neurons of the medial septum/diagonal band of Broca (MSDB) project to the hippocampus. Muscarinic cholinergic mechanisms within the MSDB are potent modulators of hippocampal functions; intraseptal scopolamine disrupts and intraseptal carbachol facilitates hippocampus-dependent learning and memory tasks, and the associated hippocampal theta rhythm. In earlier work, we demonstrated that, within the MSDB, the septohippocampal GABAergic but not cholinergic neurons are the primary target of muscarinic manipulations and that muscarinic activation of septohippocampal GABAergic neurons is mediated directly via M3 receptors. In the present study, we examined the ionic mechanism(s) underlying the excitatory actions of muscarine in these neurons. Using whole-cell patch-clamp recording techniques in rat brain slices, we demonstrated that M3 receptor-mediated muscarinic activation of MSDB neurons is dependent on external Na+ and is also reduced by bath-applied Ni2+ and KB-R7943 as well as by replacing external Na+ with Li+, suggesting a primary involvement of the Na+,Ca2+ exchanger. We conclude that the M3 receptor-mediated muscarinic activation of MSDB septohippocampal GABA-type neurons, that is important for cognitive functioning, is mediated via activation of the Na+,Ca2+ exchanger. [source]


    Melatonin inhibits hippocampal long-term potentiation

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 9 2005
    Louisa M. Wang
    Abstract The goal of this study is to investigate the effect of the hormone melatonin on long-term potentiation and excitability measured by stimulating the Schaffer collaterals and recording the field excitatory postsynaptic potential from the CA1 dendritic layer in hippocampal brain slices from mice. Application of melatonin produced a concentration-dependent inhibition of the induction of long-term potentiation, with a concentration of 100 nm producing an ,,50% inhibition of long-term potentiation magnitude. Long-duration melatonin treatments of 6 h were also effective at reducing the magnitude of long-term potentiation. Melatonin (100 nm) did not alter baseline evoked responses or paired-pulse facilitation recorded at this synapse. The inhibitory actions of melatonin were prevented by application of the melatonin (MT) receptor antagonist luzindole as well as the MT2 receptor subtype antagonist 4-phenyl-2-propionamidotetraline. These inhibitory actions of melatonin were lost in mice deficient in MT2 receptors but not those deficient in MT1 receptors. In addition, application of the protein kinase A inhibitor H-89 both mimicked the effects of melatonin and precluded further inhibition by melatonin. Finally, the application an activator of adenylyl cyclase, forskolin, overcame the inhibitory effects of melatonin on LTP without affecting the induction of long-term potentiation on its own. These results suggest that hippocampal synaptic plasticity may be constrained by melatonin through a mechanism involving MT2-receptor-mediated regulation of the adenylyl cyclase,protein kinase A pathway. [source]


    Somatodendritic autoreceptor regulation of serotonergic neurons: dependence on l -tryptophan and tryptophan hydroxylase-activating kinases

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2005
    Rong-Jian Liu
    Abstract The somatodendritic 5-HT1A autoreceptor has been considered a major determinant of the output of the serotonin (5-HT) neuronal system. However, recent studies in brain slices from the dorsal raphe nucleus have questioned the relevance of 5-HT autoinhibition under physiological conditions. In the present study, we found that the difficulty in demonstrating 5-HT tonic autoinhibition in slice results from in vitro conditions that are unfavorable for sustaining 5-HT synthesis. Robust, tonic 5-HT1A autoinhibition can be restored by reinstating in vivo 5-HT synthesizing conditions with the initial 5-HT precursor l -tryptophan and the tryptophan hydroxylase co-factor tetrahydrobiopterin (BH4). The presence of tonic autoinhibition under these conditions was revealed by the disinhibitory effect of a low concentration of the 5-HT1A antagonist WAY 100635. Neurons showing an autoinhibitory response to l -tryptophan were confirmed immunohistochemically to be serotonergic. Once conditions for tonic autoinhibition had been established in raphe slice, we were able to show that 5-HT autoinhibition is critically regulated by the tryptophan hydroxylase-activating kinases calcium/calmodulin protein kinase II (CaMKII) and protein kinase A (PKA). In addition, at physiological concentrations of l -tryptophan, there was an augmentation of 5-HT1A receptor-mediated autoinhibition when the firing of 5-HT cells activated with increasing concentrations of the ,1 adrenoceptor agonist phenylephrine. Increased calcium influx at higher firing rates, by activating tryptophan hydroxylase via CaMKII and PKA, can work together with tryptophan to enhance negative feedback control of the output of the serotonergic system. [source]


    Blockade of the NPY Y5 receptor potentiates circadian responses to light: complementary in vivo and in vitro studies

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2004
    P. C. Yannielli
    Abstract Neuropeptide Y (NPY) is delivered to the suprachiasmatic nuclei (SCN) circadian pacemaker via an input from the thalamic intergeniculate leaflet. NPY can inhibit light-induced responses of the circadian system of Syrian hamsters. Here we studied whether an antagonist to NPY receptors can be used to potentiate photic phase shifts late in the subjective night. First we determined by in situ hybridization that both NPY Y1 and Y5 receptor mRNA are expressed in the SCN of Syrian hamsters. Second, similar to our previous findings at Zeitgeber time 14 (ZT 14, where ZT 12 was the time of lights off), we found that NPY applied at ZT 18.5 onto the SCN region of brain slices maintained in vitro could block NMDA-induced phase advances of the spontaneous firing rate rhythm, and this blocking effect was probably mediated by the Y5 receptor, since co-application of Y5 receptor antagonists completely reversed the effect of NPY, while application of a Y1 receptor antagonist had no effect under the same conditions. Third, we found that co-treatment with a Y5 receptor antagonist in vivo (s.c., 10 mg/kg) not only reversed the effect of NPY applied to the SCN in vivo through a cannula but also significantly potentiated the light-induced phase advance in the absence of NPY. This is the first report of a NPY receptor antagonist having such an effect, and indicates that NPY Y5 receptor antagonists could be clinically useful for potentiating circadian system responses to light. [source]


    Cellular mechanisms of the trigeminally evoked startle response

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2003
    Susanne Schmid
    Abstract The startle response is an important mammalian model for studying the cellular mechanisms of emotions and of learning. It consists of contractions of facial and skeletal muscles in response to sudden acoustic, tactile or vestibular stimuli. Whereas the acoustic startle pathway is well described, only a few recent studies have investigated the tactile startle pathway. It was proposed that there is a direct projection from the principal sensory nucleus to the central sensorimotor interface of the startle response, which is formed by the giant neurons in the caudal pontine reticular formation. We explored this projection in greater detail in vitro. Anterograde tracing in rat brain slices confirmed projections with large axon terminals from the ventral part of the principal sensory nucleus to the lateral caudal pontine reticular formation. Electrophysiological studies revealed a monosynaptic glutamatergic connection between principal sensory nucleus neurons and caudal pontine reticular formation giant neurons. The synapses displayed paired-pulse facilitation at high-frequency stimulation, and homosynaptic depression at 1 Hz stimulation. The latter form of plasticity is thought to underlie habituation of the startle response. Furthermore, postsynaptic currents in caudal pontine reticular formation giant neurons evoked by principal sensory nucleus neuron stimulation summed in a linear way with signals evoked by stimulation of auditory afferents. Synaptic plasticity and summation of synaptic currents correspond well with in vivo data previously published by other groups. We thus presume that these synapses mediate trigeminal input to the startle pathway. [source]


    Bidirectional modulation of visual plasticity by cholinergic receptor subtypes in the frog optic tectum

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 6 2003
    Chuan-Jiang Yu
    Abstract Cholinergic input to the optic tectum is necessary for visual map maintenance. To understand why, we examined the effects of activation of the different cholinergic receptor subtypes in tectal brain slices and determined whether the retinotectal map was affected by manipulations of their activity in vivo. Both ,-bungarotoxin sensitive and insensitive nicotinic receptor agonists increased spontaneous postsynaptic currents (sPSCs) in a subpopulation of patch-clamped tectal cells; application of subtype selective receptor antagonists reduced nicotine-induced increases in sPSCs. Activation of ,-bungarotoxin insensitive nicotinic receptors also induced substantial inward current in some cells. Muscarinic receptor mediated outward current responses were blocked by the M2-like muscarinic receptor antagonists himbacine or AF-DX 384 and mimicked by application of the M2-like agonist oxotremorine. A less frequently observed muscarinic response involving a change in sPSC frequency appeared to be mediated by M1-like muscarinic receptors. In separate experiments, pharmacological manipulation of cholinergic receptor subtype activation led to changes in the activity-dependent visual map created in the tectum by retinal ganglion cell terminals. Chronic exposure of the tectum to either ,-bungarotoxin insensitive, ,-bungarotoxin sensitive or M1-like receptor antagonists resulted in map disruption. However, treatment with the M2-like receptor antagonist, AF-DX 384, compressed the map. We conclude that nicotinic or M1-like muscarinic receptors control input to tectal cells while ,-bungarotoxin insensitive nicotinic receptors and M2-like muscarinic receptors change tectal cell responses to that input. Blockade of the different cholinergic receptor subtypes can have opposing effects on map topography that are consistent with expected effects on tectal cell activity levels. [source]


    The effects of nitric oxide on magnocellular neurons could involve multiple indirect cyclic GMP-dependent pathways

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2003
    C. M. Vacher
    Abstract Nitric oxide (NO) is known to regulate the release of arginine-vasopressin (AVP) and oxytocin (OT) by the paraventricular nucleus (PVN) and the supraoptic nucleus (SON). The aim of the current study was to identify in these nuclei the NO-producing neurons and the NO-receptive cells in mice. The determination of NO-synthesizing neurons was performed by double immunohistochemistry for the neuronal form of NO synthase (NOS), and AVP or OT. Besides, we visualized the NO-receptive cells by detecting cyclic GMP (cGMP), the major second messenger for NO, by immunohistochemistry on hypothalamus slices. Neuronal NOS was exclusively colocalized with OT in the PVN and the SON, suggesting that NO is mainly synthesized by oxytocinergic neurons in mice. By contrast, cGMP was not observed in magnocellular neurons, but in GABA-, tyrosine hydroxylase- and glutamate-positive fibers, as well as in GFAP-stained cells. The cGMP-immunostaining was abolished by incubating brain slices with a NOS inhibitor (L-NAME). Consequently, we provide the first evidence that NO could regulate the release of AVP and OT indirectly by modulating the activity of the main afferents to magnocellular neurons rather than by acting directly on magnocellular neurons. Moreover, both the NADPH-diaphorase activity and the mean intensity of cGMP-immunofluorescence were increased in monoamine oxidase A knock-out mice (Tg8) compared to control mice (C3H) in both nuclei. This suggests that monoamines could enhance the production of NO, contributing by this way to the fine regulation of AVP and OT release and synthesis. [source]


    Altered presynaptic function in monoaminergic neurons of monoamine oxidase-A knockout mice

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 9 2002
    Catarina Å. Owesson
    Abstract Monoamine oxidase-A knockout (MAO-A KO) mice have elevated brain serotonin (5-HT) and noradrenaline (NA) levels, and one would therefore anticipate increased monoamine release and compensatory changes in other aspects of presynaptic monoamine function. In this study we used voltammetry in brain slices from the locus coeruleus (LC), dorsal raphe (DRN) and striatum (CPu) in 7-week-old MAO-A KO and C3H control mice to measure stimulated monoamine efflux and its control by amine transporters and autoreceptors. In LC, peak NA efflux on stimulation (99 pulses, 100 Hz) was higher in MAO-A KO than C3H mice (938 ± 58 nm cf. 511 ± 42 nm; P < 0.001). The NA uptake half time (t½) was longer in MAO-A KO than in C3H mice (6.0 ± 0.9 s cf. 1.9 ± 0.3 s; P < 0.001) and the selective NA reuptake inhibitor desipramine (50 nm) had a smaller effect in MAO-A KO mice. NA transporter binding was significantly lower in the LC of MAO-A KO mice compared to C3H controls (P < 0.01) but not in the DRN. The ,2 agonist dexmedetomidine (10 nm) decreased stimulated NA efflux more in C3H than in MAO-A KO mice (73.3% cf. 29.6% inhibition, P < 0.001). In DRN, peak 5-HT efflux on stimulation (99 pulses, 100 Hz) was greater (P < 0.01) in MAO-A KO (262 ± 44 nm) than C3H mice (157 ± 16 nm). Moreover, 5-HT uptake t½ was longer (P < 0.05) in MAO-A KO than in C3H mice (8.8 ± 1.1 s cf. 4.9 ± 0.6 s, P < 0.05) and the effect of citalopram (75 nm) was attenuated in MAO-A KOs. Serotonin transporter binding was also lower in both the DRN and LC of MAO-A KO mice. The 5-HT1A agonist 8-OH-DPAT (1 µm) decreased 5-HT efflux more in C3H than in MAO-A KO mice (38.3% inhibition cf. 21.6%, P < 0.001). In contrast, there were no significant differences between MAO-A KO and C3H mice in CPu dopamine efflux and uptake and the effect of the D2/3 agonist quinpirole was similar in the two strains. In summary, MAO-A KO mice show major dysregulation of monoaminergic presynaptic mechanisms such as autoreceptor control and transporter kinetics. [source]


    Astrocytes in the hippocampus of patients with temporal lobe epilepsy display changes in potassium conductances

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 6 2000
    Stefan Hinterkeuser
    Abstract Functional properties of astrocytes were investigated with the patch-clamp technique in acute hippocampal brain slices obtained from surgical specimens of patients suffering from pharmaco-resistant temporal lobe epilepsy (TLE). In patients with significant neuronal cell loss, i.e. Ammon's horn sclerosis, the glial current patterns resembled properties characteristic of immature astrocytes in the murine or rat hippocampus. Depolarizing voltage steps activated delayed rectifier and transient K+ currents as well as tetrodotoxin-sensitive Na+ currents in all astrocytes analysed in the sclerotic human tissue. Hyperpolarizing voltages elicited inward rectifier currents that inactivated at membrane potentials negative to -130 mV. Comparative recordings were performed in astrocytes from patients with lesion-associated TLE that lacked significant histopathological hippocampal alterations. These cells displayed stronger inward rectification. To obtain a quantitative measure, current densities were calculated and the ratio of inward to outward K+ conductances was determined. Both values were significantly smaller in astrocytes from the sclerotic group compared with lesion-associated TLE. During normal development of rodent brain, astroglial inward rectification gradually increases. It thus appears reasonable to suggest that astrocytes in human sclerotic tissue return to an immature current pattern. Reduced astroglial inward rectification in conjunction with seizure-induced shrinkage of the extracellular space may lead to impaired spatial K+ buffering. This will result in stronger and prolonged depolarization of glial cells and neurons in response to activity-dependent K+ release, and may thus contribute to seizure generation in this particular condition of human TLE. [source]


    The serotonin 5-HT2 receptor,phospholipase C system inhibits the induction of long-term potentiation in the rat visual cortex

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2000
    Yoshikuni Edagawa
    Abstract The effect of serotonin 5-HT2 receptor stimulation on long-term potentiation (LTP) in the primary visual cortex was investigated by using rat brain slices in vitro. Field potentials evoked by stimulation of layer IV were recorded in layer II/III. The 5-HT2 receptor agonist 1-(2,5-dimethyl-4-iodophenyl)-2-aminopropane (DOI) did not affect baseline synaptic potentials evoked by single-pulse test stimulation, but significantly inhibited the induction of LTP in a concentration-dependent manner (0.1,10 ,m). The LTP-inhibiting effect of DOI (10 ,m) was blocked by the 5-HT2,7 receptor antagonist ritanserin (10 ,m), but not by the 5-HT1A receptor antagonist NAN-190 (10 ,m) nor by the 5-HT3,4 receptor antagonist MDL72222 (10 ,m). The inhibitory effect of DOI was also blocked by the phospholipase C inhibitor U73122, but not by its inactive analogue U73343. These results suggest that visual cortex LTP is inhibited by activation of the 5-HT2 receptor,phospholipase C system. In addition, the LTP-inhibiting effect of DOI was abolished by the presence of the GABAA receptor antagonist bicuculline (10 ,m), suggesting that 5-HT2 receptor-mediated inhibition of visual cortex LTP is dependent on GABAergic inhibition. [source]


    Neuronal activity-related coupling in cortical arterioles: involvement of astrocyte-derived factors

    EXPERIMENTAL PHYSIOLOGY, Issue 1 2005
    T. A. Lovick
    Neuronal activity-evoked dilatation was investigated in cortical arterioles in brain slices from mature rats maintained in vitro at 31,33°C. In the presence of the thromboxane A2 agonist U46619 (75 nm) to preconstrict vessels, internal diameter decreased by 14.2% and rhythmic contractile activity (vasomotion) developed. Addition of the epoxygenase inhibitor miconazole (20 ,m) produced a further decrease in diameter and increase in the frequency of vasomotion, suggesting that tonic release of epoxygenase products maintains a level of cerebrovascular dilator tone. Addition of 1 ,m AMPA for 5 min evoked a 15.4 ± 3.7% increase in diameter and the frequency of vasomotion decreased by ,6.7 ± 1.4 contractions min,1. The response persisted in the presence of 1 ,m TTX, indicating that it was independent of neuronal activity and thus likely to have been evoked by activation of AMPA receptors on astrocytes rather than neurones. The response to the brief (5 min) application of AMPA remained unchanged in the presence of miconazole (20 ,m). Prolonged (30 min) application of AMPA produced a +12.1 ± 1.5% increase in internal diameter and reduction in vasomotion (,8.4 ± 1.7 contractions min,1) that were sustained throughout the stimulation period. However, when AMPA was applied in the presence of miconazole (20 ,m) it evoked only a transient increase in diameter (+9.8 ± 3.1%) and decrease in vasomotion (,6.6 ± 1.5 contractions min,1) that lasted for less than 10 min despite continued application of AMPA. The results suggest that products of epoxygenase activity, probably epoxyeicosatrienoic acids (EETs) are involved in activity-related dilatation in cortical arterioles. Whilst epoxygenase activity is not required to initiate dilatation, it appears to be involved in sustaining the response. Thus EETs released from membrane stores could contribute to the initial stages, but once these have been depleted de novo synthesis of EETs is required to maintain the effect. [source]


    Dynamics of a Transgene Expression in Acute Rat Brain Slices Transfected with Adenoviral Vectors

    EXPERIMENTAL PHYSIOLOGY, Issue 4 2003
    C. E. L. Stokes
    We present a quantitative account of the expression dynamics of a transgene (enhanced green fluorescent protein, EGFP) in acute brain slices transfected with an adenoviral vector (AVV) under control of the human cytomegalovirus (HCMV) promoter. Micromolar concentrations of EGFP could be detected in brainstem and hippocampal slices as early as 7 h after in vitro transfection with a viral titre of 4.4 × 109 plaque-forming units (pfu) ml,1. Although initially EGFP appeared mainly in glia, it could be detected in neurones with longer incubation times of 10-12 h. However, fluorescence was never detected within some populations of neurones, such as hippocampal pyramidal cells, or within the hypoglossal motor nucleus. The density of cells expressing EGFP peaked at 10 h and then decreased, possibly suggesting that high concentrations of EGFP are toxic. The age of the animal significantly affected the speed of EGFP accumulation: after 10 h of incubation in 30-day-old rats only 4.88 ± 0.51 cells/10 000 ,m2 were fluorescent compared to 7.28 ± 0.39 cells/10 000 ,m2 in 12-day-old rats (P < 0.05). HCMV promoter-driven transgene expression depended on the activity of protein kinase A, and was depressed with a cAMP/protein kinase A antagonist (20 ,M Rp-cAMPS; P < 0.0005). This indicates that expression of HCMV-driven constructs is likely to be skewed towards cellular populations where cAMP-dependent signalling pathways are active. We conclude that acute transfection of brain slices with AVVs within hours causes EGFP expression in micromolar concentrations and that such transfected cells may remain viable for use in physiological experiments. [source]


    Ca2+ - and thromboxane-dependent distribution of MaxiK channels in cultured astrocytes: From microtubules to the plasma membrane

    GLIA, Issue 12 2009
    J. W. Ou
    Abstract Large-conductance, voltage- and Ca2+ -activated K+ channels (MaxiK) are broadly expressed ion channels minimally assembled by four pore-forming ,-subunits (MaxiK,) and typically observed as plasma membrane proteins in various cell types. In murine astrocyte primary cultures, we show that MaxiK, is predominantly confined to the microtubule network. Distinct microtubule distribution of MaxiK, was visualized by three independent labeling approaches: (1) MaxiK,-specific antibodies, (2) expressed EGFP-labeled MaxiK,, and (3) fluorophore-conjugated iberiotoxin, a specific MaxiK pore-blocker. This MaxiK, association with microtubules was further confirmed by in vitro His-tag pulldown, co-immunoprecipitation from brain lysates, and microtubule depolymerization experiments. Changes in intracellular Ca2+ elicited by general pharmacological agents, caffeine or thapsigargin, resulted in increased MaxiK, labeling at the plasma membrane. More notably, U46619, an analog of thromboxane A2 (TXA2), which triggers Ca2+ -release pathways and whose levels increase during cerebral hemorrhage/trauma, also elicits a similar increase in MaxiK, surface labeling. Whole-cell patch clamp recordings of U46619-stimulated cells develop a ,3-fold increase in current amplitude indicating that TXA2 stimulation results in the recruitment of additional, functional MaxiK channels to the surface membrane. While microtubules are largely absent in mature astrocytes, immunohistochemistry results in brain slices show that cortical astrocytes in the newborn mouse (P1) exhibit a robust expression of microtubules that significantly colocalize with MaxiK,. The results of this study provide the novel insight that suggests that Ca2+ released from intracellular stores may play a key role in regulating the traffic of intracellular, microtubule-associated MaxiK, stores to the plasma membrane of developing murine astrocytes. © 2009 Wiley-Liss, Inc. [source]


    Plasticity of perisynaptic astroglia during synaptogenesis in the mature rat hippocampus

    GLIA, Issue 1 2007
    Mark R. Witcher
    Abstract Astroglia are integral components of synapse formation and maturation during development. Less is known about how astroglia might influence synaptogenesis in the mature brain. Preparation of mature hippocampal slices results in synapse loss followed by recuperative synaptogenesis during subsequent maintenance in vitro. Hence, this model system was used to discern whether perisynaptic astroglial processes are similarly plastic, associating more or less with recently formed synapses in mature brain slices. Perisynaptic astroglia was quantified through serial section electron microscopy in perfusion-fixed or sliced hippocampus from adult male Long-Evans rats that were 65,75 days old. Fewer synapses had perisynaptic astroglia in the recovered hippocampal slices (42.4% ± 3.4%) than in the intact hippocampus (62.2% ± 2.6%), yet synapses were larger when perisynaptic astroglia was present (0.055 ± 0.003 ,m2) than when it was absent (0.036 ± 0.004 ,m2) in both conditions. Importantly, the length of the synaptic perimeter surrounded by perisynaptic astroglia and the distance between neighboring synapses was not proportional to synapse size. Instead, larger synapses had longer astroglia-free perimeters where substances could escape from or enter into the synaptic clefts. Thus, smaller presumably newer synapses as well as established larger synapses have equal access to extracellular glutamate and secreted astroglial factors, which may facilitate recuperative synaptogenesis. These findings suggest that as synapses enlarge and release more neurotransmitter, they attract astroglial processes to a discrete portion of their perimeters, further enhancing synaptic efficacy without limiting the potential for cross talk with neighboring synapses in the mature rat hippocampus. © 2006 Wiley-Liss, Inc. [source]


    Switching between "On" and "Off" states of persistent activity in lateral entorhinal layer III neurons,

    HIPPOCAMPUS, Issue 4 2007
    Babak Tahvildari
    Abstract Persistent neural spiking maintains information during a working memory task when a stimulus is no longer present. During retention, this activity needs to be stable to distractors. More importantly, when retention is no longer relevant, cessation of the activity is necessary to enable processing and retention of subsequent information. Here, by means of intracellular recording with sharp microelectrode in in vitro rat brain slices, we demonstrate that single principal layer III neurons of the lateral entorhinal cortex (EC) generate persistent spiking activity with a novel ability to reliably toggle between spiking activity and a silent state. Our data indicates that in the presence of muscarinic receptor activation, persistent activity following an excitatory input may be induced and that a subsequent excitatory input can terminate this activity and cause the neuron to return to a silent state. Moreover, application of inhibitory hyperpolarizing stimuli is neither able to decrease the frequency of the persistent activity nor terminate it. The persistent activity can also be initiated and terminated by synchronized synaptic stimuli of layer II/III of the perirhinal cortex. The neuronal ability to switch "On" and "Off" persistent activity may facilitate the concurrent representation of temporally segregated information arriving in the EC and being directed toward the hippocampus. © 2007 Wiley-Liss, Inc. [source]


    Mesencephalic human neural progenitor cells transplanted into the neonatal hemiparkinsonian rat striatum differentiate into neurons and improve motor behaviour

    JOURNAL OF ANATOMY, Issue 6 2006
    Marine Hovakimyan
    Abstract Neural stem cell transplantation is a promising strategy for the treatment of neurodegenerative diseases. To evaluate the differentiation potential of human neural progenitor cells (hNPCs) as a prerequisite for clinical trials, we intracerebrally transplanted in vitro expanded fetal mesencephalic hNPCs into hemiparkinsonian rats. On postnatal day one (P1), 17 animals underwent a unilateral intraventricular 6-hydroxydopamine injection into the right lateral ventricle. At P3, animals (n = 10) received about 100 000 hNPCs (1 µL) in the right striatum. Five weeks after birth, animals underwent behaviour tests prior to fixation, followed by immunohistochemistry on brain slices for human nuclei, glial fibrillary acidic protein, S100,, neuronal nuclei antigen, neuron-specific enolase and tyrosine hydroxylase. Compared with the apomorphine-induced rotations in the lesioned-only group (7.4 ± 0.5 min,1), lesioned and successfully transplanted animals (0.3 ± 0.1 min,1) showed a significant therapeutic improvement. Additionally, in the cylinder test, the lesioned-only animals preferred to use the ipsilateral forepaw. Conversely, the lesioned and transplanted animals showed no significant side bias similar to untreated control animals. Transplanted human nuclei-immunoreactive cells were found to survive and migrate up to 2000 µm into the host parenchyma, many containing the pan-neuronal markers neuronal nuclei antigen and neuron-specific enolase. In the striatum, tyrosine hydroxylase-immunoreactive somata were also found, indicating a dopaminergic differentiation capacity of transplanted hNPCs in vivo. However, the relative number of tyrosine hydroxylase-immunoreactive neurons in vivo seemed to be lower than in corresponding in vitro differentiation. To minimize donor tissue necessary for transplantation, further investigations will aim to enhance dopaminergic differentiation of transplanted cells in vivo. [source]


    Neural stem cells improve neuronal survival in cultured postmortem brain tissue from aged and Alzheimer patients

    JOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 5a 2008
    L. Wu
    Abstract Neurodegenerative diseases are progressive and incurable and are becoming ever more prevalent. To study whether neural stem cell can reactivate or rescue functions of impaired neurons in the human aging and neurodegenerating brain, we co-cultured postmortem slices from Alzheimer patients and control participants with rat embryonic day 14 (E14) neural stem cells. Viability staining based on the exclusion of ethidium bromide by intact plasma membranes showed that there were strikingly more viable cells and fewer dead cells in slices co-cultured with neural stem cells than in untreated slices. The presence of Alzheimer pathology in the brain slices did not influence this effect, although the slices from Alzheimer patients, in general, contained fewer viable cells. Co-culturing with rat E14 fibroblasts did not improve the viability of neurons in the human brain slices. Since the human slices and neural stem cells were separated by a membrane during co-culturing our data show for the first time that neural stem cells release diffusible factors that may improve the survival of aged and degenerating neurons in human brains. [source]


    Catecholamine exocytosis is diminished in R6/2 Huntington's disease model mice

    JOURNAL OF NEUROCHEMISTRY, Issue 5 2007
    Michael A. Johnson
    Abstract In this work, the mechanisms responsible for dopamine (DA) release impairments observed previously in Huntington's disease model R6/2 mice were evaluated. Voltammetrically measured DA release evoked in striatal brain slices from 12-week old R6/2 mice by a single electrical stimulus pulse was only 19% of wild-type (WT) control mice. Iontophoresis experiments suggest that the concentration of released DA is not diluted by a larger striatal extracellular volume arising from brain atrophy, but, rather, that striatal dopaminergic terminals have a decreased capacity for DA release. This decreased capacity was not due to an altered requirement for extracellular Ca2+, and, as in WT mice, the release in R6/2 mice required functioning vesicular transporters. Catecholamine secretion from individual vesicles was measured during exocytosis from adrenal chromaffin cells harvested from R6/2 and WT mice. While the number of exocytotic events was unchanged, the amounts released per vesicle were significantly diminished in R6/2 mice, indicating that vesicular catecholamines are present in decreased amounts. Treatment of chromaffin cells with 3-nitropropionic acid decreased the vesicular release amount from WT cells by 50%, mimicking the release observed from untreated R6/2 cells. Thus, catecholamine release from tissues isolated from R6/2 mice is diminished because of impaired vesicle loading. [source]


    Neuroprotective role of bradykinin because of the attenuation of pro-inflammatory cytokine release from activated microglia

    JOURNAL OF NEUROCHEMISTRY, Issue 2 2007
    Mami Noda
    Abstract Bradykinin (BK) has been reported to be a mediator of brain damage in acute insults. Receptors for BK have been identified on microglia, the pathologic sensors of the brain. Here, we report that BK attenuated lipopolysaccharide (LPS)-induced release of tumor necrosis factor-alpha (TNF-,) and interleukin-1, from microglial cells, thus acting as an anti-inflammatory mediator in the brain. This effect was mimicked by raising intracellular cAMP or stimulating the prostanoid receptors EP2 and EP4, while it was abolished by a cAMP antagonist, a prostanoid receptor antagonist, or by an inhibitor of the inducible cyclooxygenase (cyclooxygenase-2). BK also enhanced formation of prostaglandin E2 and expression of microsomal prostaglandin E synthase. Expression of BK receptors and EP2/EP4 receptors were also enhanced. Using physiological techniques, we identified functional BK receptors not only in culture, but also in microglia from acute brain slices. BK reduced LPS-induced neuronal death in neuron,microglia co-cultures. This was probably mediated via microglia as it did not affect TNF-,-induced neuronal death in pure neuronal cultures. Our data imply that BK has anti-inflammatory and neuroprotective effects in the central nervous system by modulating microglial function. [source]


    Characterization of two novel proteins, NgRH1 and NgRH2, structurally and biochemically homologous to the Nogo-66 receptor

    JOURNAL OF NEUROCHEMISTRY, Issue 3 2003
    V. Pignot
    Abstract Nogo-66 receptor (NgR) has recently been identified as the neuronal receptor of the myelin-associated proteins Nogo-A, oligodendrocyte protein (OMgp) and myelin-associated glycoprotein (MAG), and mediates inhibition of axonal regeneration both in vitro and in vivo. Through database searches, we have identified two novel proteins (NgRH1 and NgRH2) that turned out to be homologous in their primary structures, biochemical properties and expression patterns to NgR. Like NgR, the homologues contain eight leucine-rich repeats (LRR) flanked by a leucine-rich repeat C-terminus (LRRCT) and a leucine-rich repeat N-terminus (LRRNT), and also have a C-terminal GPI signal sequence. Northern blot analysis showed predominant expression of NgRH1 and NgRH2 mRNA in the brain. In situ hybridization and immunohistochemistry on rat brain slices revealed neuronal expression of the genes. NgRH1 and NgRH2 were detected on the cell surface of recombinant cell lines as N-glycosylated GPI anchored proteins and, consistent with other GPI anchored proteins, were localized within the lipid rafts of cellular membranes. In addition, an N-terminal proteolytic fragment of NgR comprising the majority of the ectodomain was found to be constitutively secreted from cells. Our data indicate that NgR, NgRH1 and NgRH2 constitute a novel receptor protein family, which may play related roles within the CNS. [source]