bluuebunny/crossref_metadata_2025 huggingface dataset:
Felisberto Hernández: escritor que filosofa, filósofo que escribe. Ecos entre la poética hernandiana y el pensamiento de Carlos Vaz Ferreira
Authors: Osorno Maldonado Víctor Manuel
Published: April 2018

En este artículo se analizan algunas afinidades entre la narrativa vanguardista de Felisberto Hernández y el pensamiento que, a propósito de la escritura y del arte literario, desarrolló el filósofo uruguayo Carlos Vaz Ferreira. El punto central del trabajo radica en las nociones movimiento y proceso, categorías temáticas y esté- ticas que permiten observar los cuentos de Felisberto como una serie de discursos en apariencia inconclusos, privilegiando el procedimiento escritural por encima de la obra terminada. De esta forma, la literatura se aleja de toda idea relacionada con el estatismo de la palabra escrita y se presenta como un acontecimiento de carácter filosófico en el que la obra se (re)crea a través de la lectura.
Patterned Sensory Stimulation Induces Plasticity in Reciprocal Ia Inhibition in Humans
Authors: Perez Monica A. , Field-Fote Edelle C. , Floeter Mary Kay
Published: April 2018

Training of spinal cord circuits using sensorimotor stimulation has been proposed as a strategy to improve movement after spinal injury. How sensory stimulation may lead to long-lasting changes is not well understood. We studied whether sensory stimulation might induce changes in the strength of a specific spinal interneuronal circuit: spinally mediated reciprocal Ia inhibition. In healthy humans, the strength of reciprocal inhibition between ankle flexor and extensor muscles was assessed before and after 30 min of peroneal nerve stimulation at motor threshold intensity. Three stimulation protocols were assessed: patterned nerve stimulation (10 pulses at 100 Hz every 1.5 sec), uniform nerve stimulation (one pulse every 150 msec), and combined stimulation of the peroneal nerve and the motor cortex with transcranial magnetic stimulation. Short-latency reciprocal inhibition from ankle flexor to extensor muscles was measured by conditioning the soleus H-reflex with stimulation of the common peroneal nerve. The strength of the reciprocal inhibition was measured at baseline and for 20 min after each stimulation session. Patterned stimulation, with or without motor cortex stimulation, enhanced reciprocal inhibition for at least 5 min afterward. The uniform pattern of stimulation was ineffective. These results demonstrate the presence of short-term plasticity within spinal inhibitory circuits. We conclude that the pattern of sensory input is a crucial factor for inducing changes in the spinal circuit for reciprocal inhibition in humans. These findings may have implications for the use of repetitive patterned sensory stimulation in rehabilitative efforts to improve walking ability in patients with spinal injury.
Coexistence of Excitatory and Inhibitory GABA Synapses in the Cerebellar Interneuron Network
Authors: Chavas Joël , Marty Alain
Published: April 2018

Functional GABA synapses are usually assumed to be inhibitory. However, we show here that inhibitory and excitatory GABA connections coexist in the cerebellar interneuron network. The reversal potential of GABAergic currents (EGABA) measured in interneurons is relatively depolarized and contrasts with the hyperpolarized value found in Purkinje cells (−58 and −85 mV respectively). This finding is not correlated to a specific developmental stage and is maintained in the adult animal.EGABAin interneurons is close to the mean membrane potential (−56.5 mV, as measured with a novel “equal firing potential” method), and both parameters vary enough among cells so that the driving force for GABA currents can be either inward or outward. Indeed, using noninvasive cell-attached recordings, we demonstrate inhibitory, excitatory, and sequential inhibitory and excitatory responses to interneuron stimulation [results obtained both in juvenile (postnatal days 12–14) and subadult (postnatal days 20–25) animals]. In hyperpolarized cells, single synaptic GABA currents can trigger spikes or trains of spikes, and subthreshold stimulations enhance the responsiveness to subsequent excitatory stimulation over at least 30 msec. We suggest that the coexistence of excitatory and inhibitory GABA synapses could either buffer the mean firing rate of the interneuron network or introduce different types of correlation between neighboring interneurons, or both.
Neurotrophin-Regulated Sorting of Opioid Receptors in the Biosynthetic Pathway of Neurosecretory Cells
Authors: Kim Kyung-Ah , von Zastrow Mark
Published: April 2018

Neurotrophins modulate the endogenous opioid system, but the underlying mechanisms are poorly understood. We observed an unexpected effect of neurotrophin signaling on the membrane trafficking of recombinant opioid receptors expressed in neurosecretory cells. Epitope-tagged δ opioid receptor (DOR) and μ opioid receptor (MOR) were differentially localized between surface and internal membrane pools, respectively, when expressed in primary cultured hippocampal neurons, consistent with previous studies by others of natively expressing neurons. Selective intracellular targeting of DOR was observed in nerve growth factor (NGF)-differentiated PC12 neurosecretory cells but not in PC12 cells cultured in the absence of NGF, where both DOR and MOR were localized in the plasma membrane. Surprisingly, NGF initiated intracellular targeting of DOR in PC12 cells acutely, within 60 min after initial activation of TrkA. The NGF-induced intracellular pool of DOR originated from a late stage of the biosynthetic pathway after exit from the endoplasmic reticulum and processing of N-linked glycans in the Golgi, resulting in the accumulation in cells of a biochemically mature “reserve” pool of intracellular DOR that exhibited depolarization-dependent insertion into the plasma membrane. The C-terminal cytoplasmic tail of DOR contains a signal determining the specificity of NGF-regulated intracellular targeting. These results indicate that cloned opioid receptors are differentially targeted when expressed heterologously in neurosecretory cells, establish a model system that facilitates mechanistic study of this process, and suggest a novel function of neurotrophins in modulating the anterograde membrane trafficking of opioid receptors.
Novel Isoforms of Dlg Are Fundamental for Neuronal Development inDrosophila
Authors: Mendoza Carolina , Olguı́n Patricio , Lafferte Gabriela , Thomas Ulrich , Ebitsch Susanne , Gundelfinger Eckart D. , Kukuljan Manuel , Sierralta Jimena
Published: April 2018

Drosophila discs-large(dlg) mutants exhibit multiple developmental abnormalities, including severe defects in neuronal differentiation and synaptic structure and function. These defects have been ascribed to the loss of a single gene product, Dlg-A, a scaffold protein thought to be expressed in many cell types. Here, we describe that additional isoforms arise as a consequence of different transcription start points and alternative splicing ofdlg. At least five differentdlggene products are predicted. We identified a subset ofdlg-derived cDNAs that include novel exons encoding a peptide homologous to the N terminus of the mammalian protein SAP97/hDLG (S97N). Dlg isoforms containing the S97N domain are expressed at larval neuromuscular junctions and within the CNS of both embryos and larvae but are not detectable in epithelial tissues. Strong hypomorphicdlgalleles exhibit decreased expression of S97N, which may account for neural-specific aspects of the pleiomorphicdlgmutant phenotype. Selective inhibition of the expression of S97N-containing proteins in embryos by double-strand RNA leads to severe defects in neuronal differentiation and axon guidance, without overt perturbations in epithelia. These results indicate that the differential expression ofdlgproducts correlates with distinct functions in non-neural and neural cells. During embryonic development, proteins that include the S97N domain are essential for proper neuronal differentiation and organization, acting through mechanisms that may include the adequate localization of cell fate determinants.
In VivoImaging of Reactive Oxygen Species Specifically Associated with Thioflavine S-Positive Amyloid Plaques by Multiphoton Microscopy
Authors: McLellan Megan E. , Kajdasz Stephen T. , Hyman Bradley T. , Bacskai Brian J.
Published: April 2018

Amyloid-β, the primary constituent of senile plaques in Alzheimer's disease, is hypothesized to cause neuronal damage and cognitive failure, but the mechanisms are unknown. Using multiphoton imaging, we show a direct association between amyloid-β deposits and free radical productionin vivoin live, transgenic mouse models of Alzheimer's disease and in analogousex vivoexperiments in human Alzheimer tissue. We applied two fluorogenic compounds, which become fluorescent only after oxidation, before imaging with a near infrared laser. We observed fluorescence associated with dense core plaques, but not diffuse plaques, as determined by subsequent addition of thioflavine S and immunohistochemistry for amyloid-β. Systemic administration ofN-tert-butyl-α-phenylnitrone, a free radical spin trap, greatly reduced oxidation of the probes. These data show directly that a subset of amyloid plaques produces free radicals in living, Alzheimer's models and in human Alzheimer tissue. Antioxidant therapy neutralizes these highly reactive molecules and may therefore be of therapeutic value in Alzheimer's disease.
A Noninvasive Genetic/Pharmacologic Strategy for Visualizing Cell Morphology and Clonal Relationships in the Mouse
Authors: Badea Tudor C. , Wang Yanshu , Nathans Jeremy
Published: April 2018

Analysis of cellular morphology is the most general approach to neuronal classification. With the increased use of genetically engineered mice, there is a growing need for methods that can selectively visualize the morphologies of specified subsets of neurons. This capability is needed both to define cell morphologic phenotypes and to mark cells in a noninvasive manner for lineage studies. To this end, we describe a bipartite genetic system based on a Cre-estrogen receptor (ER) fusion protein that irreversibly activates a plasma membrane-bound alkaline phosphatase reporter gene by site-specific recombination. Because the efficiency and timing of gene rearrangement is controlled pharmacologically, a sparse subset of labeled cells can be generated from the set of CreER-expressing cells at any time during development. Histochemical visualization of alkaline phosphatase activity reveals neuronal morphology with strong and uniform labeling of all processes.
Behavioral Transitions Modulate Hippocampal Electroencephalogram Correlates of Open Field Behavior in the Rat: Support for a Sensorimotor Function of Hippocampal Rhythmical Synchronous Activity
Authors: van Lier H. , Coenen A. M. L. , Drinkenburg W. H. I. M.
Published: April 2018

A clear relationship exists between moment-to-moment behavioral elements and hippocampal rhythmical synchronous activity (RSA) (theta rhythm). However, behavioral elements are not isolated events but are part of behavioral sequences in a context of behavioral activity. By concurrently monitoring open field behavior and hippocampal EEG, EEG correlates of open field behavior in relation to preceding and following behavior were studied in Sprague Dawley rats to determine whether the behavioral context influences EEG correlates of behavior. Results show that preceding and subsequent behavioral patterns influenced the spectral power correlates of behavior. RSA power was increased when a “type 1 behavior” (voluntary movement) preceded the behavior compared with when a “type 2 behavior” (automatic movement, awake immobility) preceded it. The modulating effect of behavioral transitions was shown for several types of behaviors, and systematic modulation of hippocampal EEG correlates of behavior was demonstrated. The present report shows that the strong and systematic relationship between hippocampal RSA and behavior is modulated by the behavioral–sequential context. Thus, in addition to the well established relationship between RSA and motor activity, a second nonmotor process seems to contribute to hippocampal RSA. A likely candidate is a sensory process, which is in accordance with theories on the sensorimotor function of hippocampal RSA.
Midbrain Raphe Modulation of Nonphotic Circadian Clock Resetting and 5-HT Release in the Mammalian Suprachiasmatic Nucleus
Authors: Glass J. David , Grossman Gregory H. , Farnbauch Laure , DiNardo Lisa
Published: April 2018

Serotonin (5-HT) is an important regulator of the mammalian circadian clock of the suprachiasmatic nucleus (SCN); however, critical questions remain concerning the control of serotonergic activity in the SCN and how this relates to the putative clock-resetting actions of 5-HT. Previously, we reported that electrical stimulation of the dorsal raphe nucleus (DRN) or median raphe nucleus (MRN) in hamsters evoked 5-HT release in the SCN. This DRN-stimulated 5-HT release was blocked by systemic injection of 5-HT antagonists, indicating a 5-HT receptor-mediated pathway from the DRN to the SCN. In the present study, targeted injections of the 5-HT1,2,7antagonist metergoline or the selective 5-HT7antagonist DR4004 into the DRN or MRN attenuated DRN-electrically stimulated SCN 5-HT release, supporting a multisynaptic DRN→MRN→SCN route. Intra-DRN and intra-MRN injections of the GABAAantagonist bicuculline significantly stimulated SCN 5-HT release, whereas intra-DRN or intra-MRN injections of the GABAAagonist muscimol suppressed this release. The 5-HT release induced by intra-DRN bicuculline was also blocked by co-injection of DR4004. In complementary behavioral trials, SCN 5-HT release associated with a phase-advancing sleep deprivation stimulus at midday was prevented by intra-DRN injection of metergoline. Also, phase-advance shifts induced by novel wheel access at midday were suppressed, but not blocked, by intra-DRN injection of DR4004 or muscimol. These results indicate that 5-HT7and GABAergic receptors of the DRN and MRN regulate behaviorally induced 5-HT release in the SCN, and that DRN output modulates nonphotic phase-resetting responses.
The Glycine Transporter Type 1 InhibitorN-[3-(4′-Fluorophenyl)-3-(4′-Phenylphenoxy)Propyl]Sarcosine Potentiates NMDA Receptor-Mediated ResponsesIn Vivoand Produces an Antipsychotic Profile in Rodent Behavior
Authors: Kinney Gene G. , Sur Cyrille , Burno Maryann , Mallorga Pierre J. , Williams Jacinta B. , Figueroa David J. , Wittmann Marion , Lemaire Wei , Conn P. Jeffrey
Published: April 2018

Glycine acts as a necessary coagonist for glutamate at the NMDA receptor (NMDAR) complex by binding to the strychnine-insensitive glycine-B binding site on the NR1 subunit. The fact that glycine is normally found in the brain and spinal cord at concentrations that exceed those required to saturate this site has led to the speculation that glycine normally saturates NMDAR-containing synapsesin vivo. However, additional lines of evidence suggest that synaptic glycine may be efficiently regulated in synaptic areas by the glycine transporter type 1 (GlyT1). The recent description of a potent and selective GlyT1 inhibitor (N-[3-(4′-fluorophenyl)-3-(4′-phenylphenoxy)propyl]sarcosine [NFPS]) provides a tool for evaluation of the hypothesis that inhibition of GlyT1 may increase synaptic glycine and thereby potentiate NMDAR functionin vivo. In the present study, we found that (+)-NFPS demonstrated >10-fold greater activity in anin vitrofunctional glycine reuptake assay relative to the racemic compound.In vivo, (+/-)-NFPS significantly enhanced long-term potentiation in the hippocampal dentate gyrus induced by high-frequency electrical stimulation of the afferent perforant pathway. Furthermore, (+)-NFPS induced a pattern of c-Fos immunoreactivity comparable with the atypical antipsychotic clozapine and enhanced prepulse inhibition of the acoustic startle response in DBA/2J mice, a strain with low basal levels of prepulse inhibition. Collectively, these data suggest that selective inhibition of GlyT1 can enhance NMDAR-sensitive activityin vivoand also support the idea that GlyT1 may represent a novel target for developing therapeutics to treat disorders associated with NMDAR hypofunction.
Macaque Middle Temporal Neurons Signal Depth in the Absence of Motion
Authors: Palanca Ben J. A. , DeAngelis Gregory C.
Published: April 2018

The middle temporal (MT) visual area is widely accepted to play important roles in motion processing. It is unclear, however, whether MT contributes to visual perception during the viewing of static scenes, when there is little retinal image motion during the interval between saccades. Some previous studies suggest that MT neurons give little or no response to stationary stimuli that are flashed onto the receptive field, but no previous study has directly examined the fidelity with which MT neurons code visual information in moving versus stationary stimuli. In this study, we compare the ability of MT neurons to signal binocular disparity in moving versus stationary random-dot stereograms. Although responses to moving stimuli are typically stronger, many MT neurons give robust responses to stationary stereograms, and some MT neurons actually prefer stationary patterns to those moving at any tested speed. These responses to stationary stimuli are not caused by monitor refresh or microsaccades. Disparity tuning curves for moving and stationary stimuli are nearly identical in shape for most neurons. Although the disparity discriminability of MT neurons is generally higher for moving stereograms when responses are averaged over the entire 1.5 sec trial epoch, discriminability is comparable for moving and stationary stimuli during the first 200-300 msec of the response. Thus, in a normal time interval between saccades, MT neurons signal the binocular disparity of stationary stimuli with high fidelity. These findings show that MT can be a reliable source of visual information during the viewing of static scenes.
Transplanted Olfactory Ensheathing Cells Promote Regeneration of Cut Adult Rat Optic Nerve Axons
Authors: Li Ying , Sauvé Yves , Li Daqing , Lund Raymond D. , Raisman Geoffrey
Published: April 2018

Transplantation of olfactory ensheathing cells into spinal cord lesions promotes regeneration of cut axons into terminal fields and functional recovery. This repair involvesthe formation of a peripheral nerve-like bridge in which perineurial-like fibroblasts are organized into a longitudinal stack of parallel tubular channels, some of which contain regenerating axons enwrapped by Schwann-like olfactory ensheathing cells. The present study examines whether cut retinal ganglion cell axons will also respond to these cells, and if so, whether they form the same type of arrangement. In adult rats, the optic nerve was completely severed behind the optic disc, and a matrix containing cultured olfactory ensheathing cells was inserted between the proximal and distal stumps. After 6 months, the transplanted cells had migrated for up to 10 mm into the distal stump. Anterograde labeling with cholera toxin B showed that cut retinal ganglion cell axons had regenerated through the transplants, entered the distal stump, and elongated for 10 mm together with the transplanted cells. Electron microscopy showed that a peripheral nerve-like tissue had been formed, similar to that seen in the spinal cord transplants. However, in contrast to the spinal cord, the axons did not reach the terminal fields, but terminated in large vesicle-filled expansions beyond which the distal optic nerve stump was reduced to a densely interwoven mass of astrocytic processes.
Differential Roles of Engrailed Paralogs in Determining Sensory Axon Guidance and Synaptic Target Recognition
Authors: Marie Bruno , Blagburn Jonathan M.
Published: April 2018

The transcription factor Engrailed (En) controls axon pathfinding and synaptic target choice in an identified neuron (6m) of the cockroach cercal sensory system. Knock-out of En using double-stranded RNA interference (dsRNAi) transforms 6m so that it resembles a neighboring neuron that normally does not express theengene, has a different arbor anatomy, and makes different connections. Like many animals, the cockroach has two En paralogs, Pa-En1 and Pa-En2. In this study we tested the hypothesis that the paralogs have different effects on axon guidance and synaptic target recognition, using RNAi to knock out each one individually. Using dye injections into 6m and intracellular recordings from target interneurons, we obtained evidence that both Pa-En1 and Pa-En2 determine the axonal arborization, but only Pa-En1 controls synaptic connections. However, because immunocytochemical quantification of En protein in 6m after RNAi showed that Pa-En1 represents 65% of the total En activity and Pa-En2 only 35%, our results could be caused by dosage effects. We measured the effects of diluting the mixture of both dsRNAs on the amounts of En protein. From this dose-response curve, we calculated the appropriate dilutions of the dsRNA mixture that would titrate total En protein to levels equivalent to knock-out of either paralog. RNAi using these dilutions showed that Pa-En1 and Pa-En2 both contribute toward the control of axonal guidance and confirmed that Pa-En1 has the paralog-specific function of controlling synaptic target recognition.
Specific and Somatotopic Functional Magnetic Resonance Imaging Activation in the Trigeminal Ganglion by Brush and Noxious Heat
Authors: Borsook David , DaSilva Alexandre F. M. , Ploghaus Alex , Becerra Lino
Published: April 2018

We used functional magnetic resonance imaging (fMRI) to assess activation in the trigeminal ganglion during innocuous mechanical (brush) and noxious thermal (46°C) stimulation of the face within the receptive fields of each of the three divisions of the trigeminal nerve in healthy volunteers. For both stimulus types, we observed signal changes only in the ipsilateral ganglion, and activation occurred somatotopically, as predicted by the known anatomical segregation of the neurons comprising the ophthalmic (V1), maxillary (V2), and mandibular (V3) divisions of the nerve. Signal decreased after brush stimuli and increased after the application of noxious heat. The abilities to detect somatotopic activation within the ganglion and to segregate non-noxious mechanical from noxious thermal stimuli suggest that fMRI will be valuable for measuring changes in the trigeminal ganglion in human models of neuropathic pain and in the clinical condition itself and may also be useful in the evaluation of pain therapies.
Distribution of Kainate Receptor Subunits at Hippocampal Mossy Fiber Synapses
Authors: Darstein Melanie , Petralia Ronald S. , Swanson Geoffrey T. , Wenthold Robert J. , Heinemann Stephen F.
Published: April 2018

Kainate receptors function as mediators of postsynaptic currents and as presynaptic modulators of synaptic transmission at mossy fiber synapses. Despite intense research into the physiological properties of mossy fiber kainate receptors, their subunit composition in the presynaptic and postsynaptic compartments is unclear. Here we describe the distribution of kainate receptor subunits in mossy fiber synapses using subunit-selective antibodies and knock-out mice. We provide morphological evidence for the presynaptic localization of KA1 and KA2 receptor subunits at mossy fiber synapses. Immunogold staining for KA1 and KA2 was commonly seen at synaptic contacts and in vesicular structures. Postsynaptic labeling in dendritic spines was also observed. Although KA1 predominantly showed presynaptic localization, KA2 was concentrated to a greater degree on postsynaptic membranes. Both subunits coimmunoprecipitated from hippocampal membrane extracts with GluR6 but not GluR7 subunits. These results demonstrate that KA1 and KA2 subunits are localized presynaptically and postsynaptically at mossy fiber synapses where they most likely coassemble with GluR6 subunits to form functional heteromeric kainate receptor complexes.
Reconsolidation of a Long-Term Memory inLymnaeaRequires New Protein and RNA Synthesis and the Soma of Right Pedal Dorsal 1
Authors: Sangha Susan , Scheibenstock Andi , Lukowiak Ken
Published: April 2018

Reconsolidation of a long-term memory (LTM) in the snailLymnaea stagnaliscan be disrupted by cooling, an RNA synthesis blocker (actinomycin D), and by specifically ablating the soma of a cell we know is a site of LTM consolidation (right pedal dorsal 1, RPeD1). Aerial respiratory behavior was conditioned operantly by applying a gentle tactile stimulus to the pneumostome area (the respiratory orifice) every time the snail began to open its pneumostome to perform aerial respiration. This resulted in a reduction of this behavior while leaving cutaneous respiration intact. One week after training one-half of the animals received a memory reactivation session, which was similar to the original training (i.e., animals received reinforcement). All animals then received 1 hr of cooling, an injection of actinomycin D or saline, or the soma ablation procedure. This was followed by a test for savings 4 hr or 4 d later, which was also similar to the original training. Only those animals that received both the memory reactivation session and the treatment showed memory impairment during the test for savings. That is, the impairment was contingent on memory reactivation. These data indicate that reconsolidation requires both new RNA and protein synthesis to stabilize a reactivated memory, and it demonstrates that the soma of RPeD1, a cell that we have shown previously to be required in the consolidation of an LTM, is necessary for reconsolidation. These data suggest that the critical molecular processes occurring during both consolidation and reconsolidation transpire in the same cell inLymnaea.
The Biological Clock Nucleus: A Multiphasic Oscillator Network Regulated by Light
Authors: Quintero Jorge E. , Kuhlman Sandra J. , McMahon Douglas G.
Published: April 2018

The circadian clock nucleus of the mammalian brain is composed of thousands of oscillator neurons, each driven by the cell-autonomous action of a defined set of circadian clock genes. A critical question is how these individual oscillators are organized into an internal clock that times behavior and physiology. We examined the neural organization of the suprachiasmatic nucleus (SCN) through time-lapse imaging of a short-half-life green fluorescent protein (GFP) reporter of the circadian clock genePeriod 1(Per1). Using brain slice preparations,Per1promoter rhythms were resolved at the level of the SCN, and in individual neurons within the SCN, to determine the temporal patterns of rhythmicity resulting from exposure of mice to light/dark cycle (LD) and constant darkness (DD) conditions. Quantitative imaging and patch-clamp electrophysiology were used to define the relationship ofPer1gene expression to neurophysiological output on an individual neuron basis. We found that in both LD and DD, the overall rhythm of the clock nucleus is composed of individual cellular rhythms that peak in distinct phase groups at 3-4 hr intervals. However, the phase relationships ofPer1oscillations to locomotor activity and the phase relationships among individual neuronal oscillators within the SCN are different in LD and DD. There was a positive, linear correlation ofPer1transcription with neuronal spike frequency output, thusPer1::GFP rhythms are representative of physiological rhythmicity. Our results reveal multiple phase groupings of SCN oscillators and suggest that light regulation of oscillator interactions within the SCN underlies entrainment to the photoperiod.
Role of Thalamic Phospholipase Cβ4 Mediated by Metabotropic Glutamate Receptor Type 1 in Inflammatory Pain
Authors: Miyata Mariko , Kashiwadani Hideki , Fukaya Masahiro , Hayashi Takayuki , Wu Dianqing , Suzuki Tutomu , Watanabe Masahiko , Kawakami Yoriko
Published: April 2018

Phospholipase C (PLC) β4, one of the four isoforms of PLCβs, is the sole isoform expressed in the mouse ventral posterolateral thalamic nucleus (VPL), a key station in pain processing. The mouse thalamus also has been shown to express a high level of metabotropic glutamate receptor type 1 (mGluR1), which stimulates PLCβs through activation of Gαq/11 protein. It is therefore expected that the thalamic mGluR1-PLCβ4 cascade may play a functional role in nociceptive transmission. To test this hypothesis, we first studied behavioral responses to various nociceptive stimuli in PLCβ4 knock-out mice. We performed the formalin test and found no difference in the pain behavior in the first phase of the formalin test, which is attributed to acute nociception, between PLCβ4 knock-out and wild-type mice. Consistent with this result, acute pain responses in the hot plate and tail flick tests were also unaffected in the PLCβ4 knock-out mice. However, the nociceptive behavior in the second phase of the formalin test, resulting from the tissue inflammation, was attenuated in PLCβ4 knock-out mice. In the dorsal horn of the spinal cord where PLCβ1 and PLCβ4 mRNAs are expressed, no difference was found between the wild-type and knock-out mice in the number of Fos-like immunoreactive neurons, which represent neuronal activity in the second phase in the formalin test. Thus, it is unlikely that spinal PLCβ4 is involved in the formalin-induced inflammatory pain. Next, we found that pretreatment with PLC inhibitors, mGluR1 antagonists, or both, by either intracerebroventricular or intrathalamic injection, attenuated the formalin-induced pain behavior in the second phase in wild-type mice. Furthermore, activation of mGluR1 at the VPL enhanced pain behavior in the second phase in the wild-type mice. In contrast, PLCβ4 knock-out mice did not show such enhancement, indicating that mGluR1 is connected to PLCβ4 in the VPL. Finally, in parallel with the behavioral results, we showed in an electrophysiological study that the time course of firing discharges in VPL corresponds well to that of pain behavior in the formalin test in both wild-type and PLCβ4 knock-out mice. These findings indicate that the thalamic mGluR1-PLCβ4 cascade is indispensable for the formalin-induced inflammatory pain by regulating the response of VPL neurons.
The Contribution of NMDA and AMPA Conductances to the Control of Spiking in Neurons of the Deep Cerebellar Nuclei
Authors: Gauck Volker , Jaeger Dieter
Published: April 2018

We performed whole-cell patch-clamp recordingsin vitroto investigate the integration of excitatory and inhibitory inputs in neurons of the deep cerebellar nuclei (DCN) by applying synthetic synaptic input patterns with dynamic clamping. We explored an input regime in which excitation and inhibition had an ongoing baseline rate because both input pathways show ongoing activityin vivo. We found that spiking was time-locked to transients in the inputs, consisting of brief decreases in inhibitory or increases in excitatory conductance. Such input transients were caused by synchronization among multiple inputs. However, we found that temporal synchrony in the inhibitory input pathway had preferential access to the control of DCN spiking, because the large NMDA component of the excitatory inputs smoothed out temporal transients in this pathway. Thus, synaptic integration in the DCN appears to be tuned to allow the cerebellar cortical output from Purkinje cells preferential access to the control of DCN spiking. The effect of temporal modulations in the inhibition was further enhanced by the voltage dependence of the NMDA inputs. Thus, the presence of a baseline of mossy and climbing fiber inputs boosted depolarizing responses caused by reduced inhibition by the voltage-dependent increase in inward NMDA current. Overall, our results show that correlated activity or pauses in populations of Purkinje cells are well suited to the dynamic control of DCN spiking. In addition, strong transients in excitation can directly drive DCN responses that bypass cerebellar cortical processing.
Responses of Tonically Active Neurons in the Monkey Striatum Discriminate between Motivationally Opposing Stimuli
Authors: Ravel Sabrina , Legallet Eric , Apicella Paul
Published: April 2018

The striatum is involved in the control of appetitively motivated behavior. We found previously that tonically active neurons (TANs) in the monkey striatum show discriminative responses to different stimuli that are appetitive or aversive. However, these differential responses may reflect the sensory qualities of the stimulus rather than its motivational value. In the present study, we sought to define more precisely the relationship between the particular aspect of the response of TANs and the motivational value of stimuli. For this purpose, three monkeys were presented with two types of aversive stimuli (loud sound and air puff) and one appetitive stimulus (fruit juice). In most instances, the TAN responses to the loud sound and the air puff were similar, in terms of response pattern and duration, whereas responses to the liquid reward showed distinct features. Using classical appetitive conditioning, we reversed the motivational value of a stimulus so that a previously aversive stimulus was now associatively paired with a reward and found that this manipulation selectively modifies the expression of TAN responses to the stimulus. These data indicate that the characteristics of neuronal responses undergo modifications when the valence of the stimulus is changed from aversive to appetitive during associative learning, suggesting that TANs may contribute to a form of stimulus encoding that is dependent on motivational attributes. The adaptation of TAN responses such as observed in the present study likewise reflects a neuronal system that adjusts to the motivational information about environmental events.
Presynaptic Remodeling Contributes to Activity-Dependent Synaptogenesis
Authors: Nikonenko Irina , Jourdain Pascal , Muller Dominique
Published: April 2018

Induction of long-term potentiation and application of short periods of anoxia/hypoglycemia result in the growth of dendritic filopodia and formation of new spines. Here we investigated whether these conditions also affected the morphology of presynaptic structures. Using confocal imaging of DiI-labeled axons, electron microscopy, and stereological analyses, we show that short anoxia/hypoglycemia and theta burst stimulation induced rapid, calcium-dependent growth of presynaptic filopodia-like protrusions and remodeling of presynaptic varicosities. Three-dimensional reconstruction of axonal outgrowths revealed that, within 30 min, they made contacts and triggered the formation of a postsynaptic density on the target cell. Interestingly, these axonal filopodia first established synapses with the dendritic shaft and later mostly with spines. They also contributed to the formation of multi-innervated spines. Because these presynaptic growth mechanisms depended on NMDA receptor activation, we investigated whether a diffusing messenger could be involved. We found that blockade of nitric oxide synthase prevented these changes, and conversely, a nitric oxide donor could reproduce them. A model is presented that proposes that activation of NMDA receptors and subsequent release of nitric oxide could trigger the growth of presynaptic filopodia, which, in turn, play an active role in synaptogenesis and spine formation.
Distinct Roles of D1and D5Dopamine Receptors in Motor Activity and Striatal Synaptic Plasticity
Authors: Centonze Diego , Grande Cristina , Saulle Emilia , Martín Ana B. , Gubellini Paolo , Pavón Nancy , Pisani Antonio , Bernardi Giorgio , Moratalla Rosario , Calabresi Paolo
Published: April 2018

Stimulation of dopamine (DA) receptors in the striatum is essential for voluntary motor activity and for the generation of plasticity at corticostriatal synapses. In the present study, mice lacking DA D1receptors have been used to investigate the involvement of the D1-like class (D1and D5) of DA receptors in locomotion and corticostriatal long-term depression (LTD) and long-term potentiation (LTP). Our results suggest that D1and D5receptors exert distinct actions on both activity-dependent synaptic plasticity and spontaneous motor activity. Accordingly, the ablation of D1receptors disrupted corticostriatal LTP, whereas pharmacological blockade of D5receptors prevented LTD. On the other side, genetic ablation of D1receptors increased locomotor activity, whereas the D1/D5receptor antagonist SCH 23390 decreased motor activity in both control mice and mice lacking D1receptors.

Endogenous DA stimulated D1and D5receptors in distinct subtypes of striatal neurons to induce, respectively, LTP and LTD. In control mice, in fact, LTP was blocked by inhibiting the D1–protein kinase A pathway in the recorded spiny neuron, whereas the striatal nitric oxide-producing interneuron was presumably the neuronal subtype stimulated by D5receptors during the induction phase of LTD.

Understanding the role of DA receptors in striatal function is essential to gain insights into the neural bases of critical brain functions and of dramatic pathological conditions such as Parkinson's disease, schizophrenia, and drug addiction.
Amyloid-β Immunization Effectively Reduces Amyloid Deposition in FcRγ-/-Knock-Out Mice
Authors: Das Pritam , Howard Victor , Loosbrock Nicole , Dickson Dennis , Murphy M. Paul , Golde Todd E.
Published: April 2018

Direct immunization with amyloidβ protein (Aβ) and passive transfer of anti-Aβ antibodies reduce Aβ accumulation and attenuate cognitive deficits in transgenic models of Alzheimer's disease (AD). The reduction in Aβ deposition has been proposed to involve microglial phagocytosis of Aβ immune complexes via Fc receptors (FcRs). We have examined the efficacy of Aβ immunization in amyloid precursor protein (APP) transgenic mice crossed into FcR-γ chain knock-out mice (FcRγ-/-). As might be expected from previous studies on macrophages, phagocytosis of Aβ immune complexes via FcR was completely impaired in microglia cells isolated from FcRγ-/-mice. Thus, we immunized APP Tg2576 transgenic mice that were crossed in the FcRγ-/-background with Aβ1–42 and then analyzed the effect on Aβ accumulation. In APP Tg2576 transgenic mice crossed to FcRγ-/-, Aβ1–42 immunization significantly attenuated Aβ deposition, as assessed by both biochemical and immunohistological methods. The reduction in Aβ accumulation was equivalent to the reduction in deposition seen in Aβ1–42 immunized, age-matched, FcR-sufficient Tg2576 mice. We conclude that after Aβ immunization, the effects of anti-Aβ antibodies on Aβ deposition in APP Tg2576 transgenic mice are not dependent on FcR-mediated phagocytic events.
Reciprocal Inhibition of p53 and Nuclear Factor-κB Transcriptional Activities Determines Cell Survival or Death in Neurons
Authors: Culmsee Carsten , Siewe Jan , Junker Vera , Retiounskaia Marina , Schwarz Stephanie , Camandola Simonetta , El-Metainy Shahira , Behnke Hagen , Mattson Mark P. , Krieglstein Josef
Published: April 2018

The tumor suppressor and transcription factor p53 is a key modulator of cellular stress responses, and activation of p53 precedes apoptosis in many cell types. Controversial reports exist on the role of the transcription factor nuclear factor-κB (NF-κB) in p53-mediated apoptosis, depending on the cell type and experimental conditions. Therefore, we sought to elucidate the role of NF-κB in p53-mediated neuron death. In cultured neurons DNA damaging compounds induced activation of p53, whereas NF-κB activity declined significantly. The p53 inhibitor pifithrin-α (PFT) preserved NF-κB activity and protected neurons against apoptosis. Immunoprecipitation experiments revealed enhanced p53 binding to the transcriptional cofactor p300 after induction of DNA damage, whereas binding of p300 to NF-κB was reduced. In contrast, PFT blocked the interaction of p53 with the cofactor, whereas NF-κB binding to p300 was enhanced. Most interestingly, similar results were observed after oxygen glucose deprivation in cultured neurons and in ischemic brain tissue. Ischemiainduced repression of NF-κB activity was prevented and brain damage was reduced by the p53 inhibitor PFT in a dose-dependent manner. It is concluded that a balanced competitive interaction of p53 and NF-κB with the transcriptional cofactor p300 exists in neurons. Exposure of neurons to lethal stress activates p53 and disrupts NF-κB binding to p300, thereby blocking NF-κB-mediated survival signaling. Inhibitors of p53 provide pronounced neuroprotective effects because they block p53-mediated induction of cell death and concomitantly enhance NF-κB-induced survival signaling.
A Peptide Inhibitor of c-Jun N-Terminal Kinase Protects against Both Aminoglycoside and Acoustic Trauma-Induced Auditory Hair Cell Death and Hearing Loss
Authors: Wang J. , Van De Water T. R. , Bonny C. , de Ribaupierre F. , Puel J. L. , Zine A.
Published: April 2018

Hearing loss can be caused by a variety of insults, including acoustic trauma and exposure to ototoxins, that principally effect the viability of sensory hair cells via the MAP kinase (MAPK) cell death signaling pathway that incorporates c-Jun N-terminal kinase (JNK).

We evaluated the otoprotective efficacy of D-JNKI-1, a cell permeable peptide that blocks the MAPK–JNK signal pathway. The experimental studies included organ cultures of neonatal mouse cochlea exposed to an ototoxic drug and cochleae of adult guinea pigs that were exposed to either an ototoxic drug or acoustic trauma. Results obtained from the organ of Corti explants demonstrated that the MAPK–JNK signal pathway is associated with injury and that blocking of this signal pathway prevented apoptosis in areas of aminoglycoside damage. Treatment of the neomycin-exposed organ of Corti explants with D-JNKI-1 completely prevented hair cell death initiated by this ototoxin. Results fromin vivostudies showed that direct application of D-JNKI-1 into the scala tympani of the guinea pig cochlea prevented nearly all hair cell death and permanent hearing loss induced by neomycin ototoxicity. Local delivery of D-JNKI-1 also prevented acoustic trauma-induced permanent hearing loss in a dose-dependent manner. These results indicate that the MAPK–JNK signal pathway is involved in both ototoxicity and acoustic trauma-induced hair cell loss and permanent hearing loss. Blocking this signal pathway with D-JNKI-1 is of potential therapeutic value for long-term protection of both the morphological integrity and physiological function of the organ of Corti during times of oxidative stress.
Sedation and Anesthesia Mediated by Distinct GABAAReceptor Isoforms
Authors: Reynolds David S. , Rosahl Thomas W. , Cirone Jennifer , O'Meara Gillian F. , Haythornthwaite Alison , Newman Richard J. , Myers Janice , Sur Cyrille , Howell Owain , Rutter A. Richard , Atack John , Macaulay Alison J. , Hadingham Karen L. , Hutson Peter H. , Belelli Delia , Lambert Jeremy J. , Dawson Gerard R. , McKernan Ruth , Whiting Paul J. , Wafford Keith A.
Published: April 2018

The specific mechanisms underlying general anesthesia are primarily unknown. The intravenous general anesthetic etomidate acts by potentiating GABAAreceptors, with selectivity for β2 and β3 subunit-containing receptors determined by a single asparagine residue. We generated a genetically modified mouse containing an etomidate-insensitive β2 subunit (β2 N265S) to determine the role of β2 and β3 subunits in etomidate-induced anesthesia. Loss of pedal withdrawal reflex and burst suppression in the electroencephalogram were still observed in the mutant mouse, indicating that loss of consciousness can be mediated purely through β3-containing receptors. The sedation produced by subanesthetic doses of etomidate and during recovery from anesthesia was present only in wild-type mice, indicating that the β2 subunit mediates the sedative properties of anesthetics. These findings show that anesthesia and sedation are mediated by distinct GABAAreceptor subtypes.
Development of the Spatial Organization and Dynamics of Lateral Interactions in the Human Visual System
Authors: Hou Chuan , Pettet Mark W. , Sampath Vanitha , Candy T. Rowan , Norcia Anthony M.
Published: April 2018

Psychophysical thresholds and neuronal responses for isolated stimuli are strongly modified by nearby stimuli in the visual field. We studied the orientation and position specificity of these contextual interactions using a dual-frequency visual-evoked potential technique in developing human infants and adults. One set of small, oriented stimulus elements (targets) was tagged with a temporal frequencyf1of 4.52 Hz. The addition of an abutting second set of similar patches (flankers) tagged atf2= 2.58 Hz had three effects: (1) The flankers reduced the second and fourth harmonic responses to the targets. This reduction was independent of flanker orientation or position and age. (2) The response to the combination of targets and flankers also contained nonlinear interaction terms (1f1± 1f2) that were tuned for flanker orientation and position in adults, but only for flanker orientation in infants 8-31 weeks of age. (3) Nonlinear interaction terms recorded at 2f1± 2f2were large and untuned for flanker orientation and position in adults but were nearly absent in the youngest infants. The three forms of nonlinear interaction, thus, have differences in sensitivity to flanker orientation and position and differential growth trends, indicating that they are generated by different mechanisms. These three forms of interaction could serve different functional roles. The first process provides a nonselective gain control that is fully functional in early infancy. The second process, which develops slowly, is selective for the specific form of the stimuli. The third process, which is also immature, pools across orientation.
Disregulated RhoGTPases and Actin Cytoskeleton Contribute to the Migration Defect in Lis1-Deficient Neurons
Authors: Kholmanskikh Stanislav S. , Dobrin Joseph S. , Wynshaw-Boris Anthony , Letourneau Paul C. , Ross M. Elizabeth
Published: April 2018

Lissencephaly is a severe brain malformation caused by impaired neuronal migration.Lis1, a causative gene, functions in an evolutionarily conserved nuclear translocation pathway regulating dynein motor and microtubule dynamics. Whereas microtubule contributions to neuronal motility are incompletely understood, the actin cytoskeleton is essential for crawling cell movement of all cell types investigated.Lis1haploinsufficiency is shown here to also result in reduced filamentous actin at the leading edge of migrating neurons, associated with upregulation of RhoA and downregulation of Rac1 and Cdc42 activity. Disruption of RhoA function through pharmacological inhibition of its effector kinase, p160ROCK, restores normal Rac1 and Cdc42 activity and rescues the motility defect inLis1+/- neurons. These data indicate a previously unrecognized role for Lis1 protein in neuronal motility by promoting actin polymerization through the regulation of Rho GTPase activity. This effect of Lis1 on GTPases does not appear to occur through direct Lis1 binding of Rho, but could involve Lis1 effects on Rho modulatory proteins or on microtubule dynamics.