bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential Activation of Extracellular Signal-Regulated Protein Kinase in Primary Afferent Neurons Regulates Brain-Derived Neurotrophic Factor Expression after Peripheral Inflammation and Nerve Injury
Authors: Obata Koichi , Yamanaka Hiroki , Dai Yi , Tachibana Toshiya , Fukuoka Tetsuo , Tokunaga Atsushi , Yoshikawa Hideki , Noguchi Koichi
Published: April 2018

To investigate the intracellular signal transduction pathways involved in regulating the gene expression of brain-derived neurotrophic factor (BDNF) in primary afferent neurons, we examined the activation of extracellular signal-regulated protein kinase (ERK) in dorsal root ganglion (DRG) neurons after peripheral inflammation and sciatic nerve transection. Peripheral inflammation induced an increase in the phosphorylation of ERK, mainly in tyrosine kinase A-containing small-to-medium-diameter DRG neurons. The treatment of the mitogen-activated protein kinase (MAPK) kinase 1/2 inhibitor U0126 reversed the pain hypersensitivity and the increase in phosphorylated-ERK (p-ERK) and BDNF in DRG neurons induced by complete Freund's adjuvant. On the other hand, axotomy induced the activation of ERK mainly in medium-and large-sized DRG neurons and in satellite glial cells. U0126 suppressed the axotomy-induced autotomy behavior and reversed the increase in p-ERK and BDNF. The intrathecal application of nerve growth factor (NGF) induced an increase in the number of p-ERK-and BDNF-labeled cells, mainly small neurons, and the application of anti-NGF induced an increase in p-ERK and BDNF in some medium-to-large-diameter DRG neurons. The activation of MAPK in the primary afferents may occur in different populations of DRG neurons after peripheral inflammation and axotomy, respectively, through alterations in the target-derived NGF. These changes, including the changes in BDNF expression, might be involved in the pathophysiological changes in primary afferent neurons.
Expression and Function of Chloride Transporters during Development of Inhibitory Neurotransmission in the Auditory Brainstem
Authors: Balakrishnan Veeramuthu , Becker Michael , Löhrke Stefan , Nothwang Hans Gerd , Güresir Erdem , Friauf Eckhard
Published: April 2018

Glycine and GABA, the dominant inhibitory neurotransmitters in the CNS, assume a depolarizing role in early development, leading to increased cytoplasmic Ca2+levels and action potentials. The effect is thought to be of some significance for maturation. The depolarization is caused by Cl−efflux, and chloride transporters contribute to the phenomenon by raising the intracellular Cl−concentration ([Cl−]i) above equilibrium, thereby generating an outward-directed electrochemical gradient for Cl−. In mature neurons, the [Cl−]iis reduced below equilibrium, thus rendering glycine activity hyperpolarizing. Here, we investigated the temporal expression of the K-Cl cotransporter KCC2 and the Na-K-Cl cotransporter NKCC1 in the lateral superior olive (LSO) of rats and mice. The two cation cotransporters normally extrude and accumulate Cl−, respectively. As evidenced by several methods, KCC2 mRNA was present in LSO neurons during both the depolarizing and hyperpolarizing periods. Western blots confirmed a constant level of KCC2 in the brainstem, and immunohistochemistry showed that the protein is diffusely distributed within neonatal LSO neurons, becoming integrated into the plasma membrane only with increasing age. The glycine reversal potential inKCC2knock-out mice differed significantly from that determined in wild-type controls at postnatal day 12 (P12) but not at P3, demonstrating that KCC2 is not active in neonates, despite its early presence. NKCC1 mRNA was not detected during the depolarizing phase in the LSO, implying that this transporter does not contribute to the high [Cl−]i. Our results reveal major differences in the development of [Cl−]iregulation mechanisms seen in brainstem versus forebrain regions.
Increased Expression of Brain-Derived Neurotrophic Factor Preserves Retinal Function and Slows Cell Death from Rhodopsin Mutation or Oxidative Damage
Authors: Okoye Godwin , Zimmer Joelle , Sung Jennifer , Gehlbach Peter , Deering Tye , Nambu Hiroyuki , Hackett Sean , Melia Michele , Esumi Noriko , Zack Donald J. , Campochiaro Peter A.
Published: April 2018

There are no effective treatments for inherited retinal degenerations, which are prevalent causes of visual disability. Several proteins promote the survival of various types of neurons, and increasing expression of one or more of these survival factors is a promising strategy for a new treatment. Studies examining the effects of intravitreous injections of brain-derived neurotrophic factor (BDNF) in models of inherited retinal degenerations have suggested that BDNF has little survival-promoting activity for photoreceptors. In this study, we generated double transgenic mice with doxycycline-inducible expression of BDNF in the retina. In a model of primary rod photoreceptor degeneration, expression of BDNF resulted in significant delay in photoreceptor cell death and maintenance of retinal function assessed by electroretinogram recordings. Expression of BDNF also caused strong protection of photoreceptors from oxidative damage-induced cell death. These data suggest that continuous expression of BDNF, unlike intravitreous injections, results in morphologic and functional benefit in animal models of inherited retinal degeneration. Double transgenic mice with inducible expression of survival factors provide valuable tools for selection of survival factor candidates for gene therapy.
Location and Size of Dopaminergic and Serotonergic Cell Populations Are Controlled by the Position of the Midbrain–Hindbrain Organizer
Authors: Brodski Claude , Weisenhorn Daniela M. Vogt , Signore Massimo , Sillaber Inge , Oesterheld Matthias , Broccoli Vania , Acampora Dario , Simeone Antonio , Wurst Wolfgang
Published: April 2018

Midbrain dopaminergic and hindbrain serotonergic neurons play an important role in the modulation of behavior and are involved in a series of neuropsychiatric disorders. Despite the importance of these cells, little is known about the molecular mechanisms governing their development. During embryogenesis, midbrain dopaminergic neurons are specified rostral to the midbrain–hindbrain organizer (MHO), and hindbrain serotonergic neurons are specified caudal to it. We report that in transgenic mice in whichOtx2and accordingly the MHO are shifted caudally, the midbrain dopaminergic neuronal population expands to the ectopically positioned MHO and is enlarged. Complementary, the extension of the hindbrain serotonergic cell group is decreased. These changes are preserved in adulthood, and the additional, ectopic dopaminergic neurons project to the striatum, which is a proper dopaminergic target area. In addition, in mutants in whichOtx2and the MHO are shifted rostrally, dopaminergic and serotonergic neurons are relocated at the newly positioned MHO. However, in these mice, the size ratio between these two cell populations is changed in favor of the serotonergic cell population. To investigate whether the position of the MHO during embryogenesis is also of functional relevance for adult behavior, we tested mice with a caudally shifted MHO and report that these mutants show a higher locomotor activity. Together, we provide evidence that the position of the MHO determines the location and size of midbrain dopaminergic and hindbrain serotonergic cell populationsin vivo. In addition, our data suggest that the position of the MHO during embryogenesis can modulate adult locomotor activity.
Vasopressin-Induced Cytoplasmic and Nuclear Calcium Signaling in Embryonic Cortical Astrocytes: Dynamics of Calcium and Calcium-Dependent Kinase Translocation
Authors: Zhao Lixia , Brinton Roberta Diaz
Published: April 2018

The present study sought to determine the downstream consequences of V1avasopressin receptor (V1aR) activation of Ca2+signaling in cortical astrocytes. Results of these analyses demonstrated that V1aR activation led to a marked increase in both cytoplasmic and nuclear Ca2+. We also investigated V1aR activation of Ca2+-activated signaling kinases, protein kinase C (PKC), Ca2+/calmodulin-dependent protein kinase II (CaMKII), and the mitogen-activated protein (MAP) kinases [MAPK and extracellular signal-regulated kinases 1 and 2 (ERK1/2)], their localization within cytoplasmic and nuclear compartments, and activation of their downstream nuclear target, the transcription factor cAMP response element-binding protein (CREB). Results of these analyses demonstrated that V1aR activation led to a significant rise in PKC, CaMKII, and ERK1/2 activation, with CaMKII and ERK1/2 demonstrating dynamic transport between cytoplasmic and nuclear compartments. Although no evidence of PKC translocation was apparent, PKC and CaMKs were required for activation and nuclear translocation of ERK1/2. Subsequent to CaMKII and ERK1/2 translocation to the nucleus, CREB activation occurred and was found to be dependent on upstream activation of ERK1/2 and CaMKs. These data provide the first systematic analysis of the V1aR-induced Ca2+signaling cascade in cortical astrocytes. In addition, results of this study introduce a heretofore unknown effect of vasopressin, dynamic Ca2+signaling between the cytoplasm and nucleus that leads to comparable dynamics of kinase activation and shuttling between cytoplasmic and nuclear compartments. Implications for development and regeneration induced by V1aR activation of CREB-regulated gene expression in cortical astrocytes are discussed.
Multiple Cell Populations in the Early Postnatal Subventricular Zone Take Distinct Migratory Pathways: A Dynamic Study of Glial and Neuronal Progenitor Migration
Authors: Suzuki Satoshi O. , Goldman James E.
Published: April 2018

Neural progenitors in the subventricular zone (SVZ) of the postnatal rat forebrain give rise to either olfactory interneurons or glia. To investigate the overall patterns of progenitor movement, we labeled neonatal rat SVZ cells by stereotactic injection of a GFP-encoding retrovirus into the SVZ at various coronal levels. We then studied the movements of labeled cells by time-lapse videomicroscopy in living brain slices cut in different orientations. We observed two migration patterns: (1) progenitors migrated radially into the overlying white matter and cortex, but only at the level of viral injection; these were previously shown to give rise to astrocytes and oligodendrocytes, (2) progenitors migrated in a bidirectional, rostrocaudal pattern along the entire extent of the SVZ; many of these cells eventually migrated into the olfactory bulb and developed into interneurons, but they did not turn to migrate radially out of the SVZ until they reached the olfactory bulb. Video imaging showed apparent boundaries to migration between the SVZ and adjacent structures. These observations indicate that there are at least two distinct migratory pathways within the SVZ used differentially by immature neurons and glia.
Recovery of Amiloride-Sensitive Neural Coding during Regeneration of the Gustatory Nerve: Behavioral–Neural Correlation of Salt Taste Discrimination
Authors: Yasumatsu Keiko , Katsukawa Hideo , Sasamoto Kazushige , Ninomiya Yuzo
Published: April 2018

The chorda tympani (CT) nerve innervating the anterior tongue contains two types of NaCl-responsive fibers: one, the N-type, receives input from receptor cells, the NaCl responses of which are strongly inhibited by amiloride, whereas the other, the E-type, receives input from cells poorly sensitive or insensitive to amiloride. To investigate the formation of this differentially responsive neural system, we crushed the mouse CT nerve and examined the subsequent recovery of NaCl responses and amiloride sensitivity of the regenerated nerve and behavioral discrimination between NaCl and KCl. At 2 weeks after the nerve crush, no significant response of the nerve to chemical stimuli was observed. At 3 weeks, responses to salts gradually reappeared. In this period, almost all single fibers responding to NaCl were insensitive to amiloride (E-type). At 4 weeks, some of the single fibers showed amiloride sensitivity (N-type) and behavioral discrimination between NaCl and KCl reappeared. After ≥5 weeks, the number of N-type fibers had reached the control level and became approximately equal to that of E-type fibers. During the course of recovery, N-type and E-type fibers were clearly distinguishable on the basis of their amiloride sensitivities, their KCl/NaCl response ratios, and their concentration–response relationships to NaCl. These results suggest that two salt-responsive systems are independently reformed after the nerve crush. The selective synapse reformation may account for recovery of behavioral discrimination between NaCl and KCl after taste nerve crush and regeneration. It may also explain stable sensory coding for taste quality during the continuous turnover of receptor cells in the healthy animal.
ATP Acts via P2Y1Receptors to Stimulate Acetylcholinesterase and Acetylcholine Receptor Expression: Transduction and Transcription Control
Authors: Choi Roy C. Y. , Siow Nina L. , Cheng Anthony W. M. , Ling Karen K. Y. , Tung Edmund K. K. , Simon Joseph , Barnard Eric A. , Tsim Karl W. K.
Published: April 2018

At the vertebrate neuromuscular junction ATP is known to stabilize acetylcholine in the synaptic vesicles and to be co-released with it. We have shown previously that a nucleotide receptor, the P2Y1receptor, is localized at the junction, and we propose that this mediates a trophic role for synaptic ATP there. Evidence in support of this and on its mechanism is given here. With the use of chick or mouse myotubes expressing promoter–reporter constructs from genes of acetylcholinesterase (AChE) or of the acetylcholine receptor subunits, P2Y1receptor agonists were shown to stimulate the transcription of each of those genes. The pathway to activation of theAChEgene was shown to involve protein kinase C and intracellular Ca2+release. Application of dominant-negative or constitutively active mutants, or inhibitors of specific kinases, showed that it further proceeds via some of the known intermediates of extracellular signal-regulated kinase phosphorylation. In both chick and mouse myotubes this culminates in activation of the transcription factor Elk-1, confirmed by gel mobility shift assays and by the nuclear accumulation of phosphorylated Elk-1. All of the aforementioned activations by agonist were amplified when the content of P2Y1receptors was boosted by transfection, and the activations were blocked by a P2Y1-selective antagonist. Two Elk-1 binding site sequences present in theAChEgene promoter were jointly sufficient to drive ATP-induced reporter gene transcription. Thus ATP regulates postsynaptic gene expression via a pathway to a selective transcription factor activation.
Serotonin Drives a Novel GABAergic Synaptic Current Recorded in Rat Cerebellar Purkinje Cells: A Lugaro Cell to Purkinje Cell Synapse
Authors: Dean Isabel , Robertson Susan J. , Edwards Frances A.
Published: April 2018

We recorded a novel fast GABAergic synaptic current in cerebellar Purkinje cells in rat brain slices using patch-clamp techniques. Because of a relatively low sensitivity to bicuculline, these currents can be recorded under conditions in which basket and stellate cell inputs are blocked. The observations that the novel synaptic currents occur spontaneously only in the presence of serotonin, and the specific limited positions in the slice from which they can be electrically evoked, suggest that the presynaptic cell is the Lugaro cell. Cell-attached recordings confirm that the Lugaro cell is the only interneuron in the cerebellar cortex with firing behavior consistent with the spontaneous activity recorded in Purkinje cells. The input shows a strong presynaptic modulation mediated by GABAAreceptors, resulting in a dynamic range from almost 0 to >90% release probability. Modeling GABAAreceptor responses to different GABA transients suggests that the relatively low sensitivity of the synaptic currents to bicuculline, compared with the higher affinity GABAAreceptor antagonist SR-95531 (2-(3-carboxypropyl)-3-amino-6-(4-methoxyphenyl) pyridazinium), is attributable to an unusually long GABA dwell time and/or high GABA concentration in the synaptic cleft. The significance of this novel input is discussed in relation to other GABAergic synapses impinging on Purkinje cells. We suggest that the release of GABA onto Purkinje cells from Lugaro cells would primarily occur during motor activity under conditions in which the activity of basket and stellate cells might be inhibited.
A Role for the Basal Forebrain Cholinergic System in Estrogen-Induced Disinhibition of Hippocampal Pyramidal Cells
Authors: Rudick Charles N. , Gibbs Robert B. , Woolley Catherine S.
Published: April 2018

Estrogen transiently disinhibits hippocampal CA1 pyramidal cells in adult female rats and prolongs the decay time of IPSCs in these cells. Estrogen-induced changes in synaptic inhibition are likely to be causally related to subsequent enhancements in excitatory synaptic function in CA1 pyramidal cells. Currently, it is unknown how or on what cells estrogen acts to regulate synaptic inhibition in the hippocampus. We used whole-cell voltage-clamp recording of synaptically evoked IPSCs, spontaneous IPSCs, and miniature IPSCs in CA1 pyramidal cells to evaluate estrogen-induced changes in synaptic inhibition in ovariectomized rats that either were pretreated with the estrogen receptor (ER) antagonist tamoxifen or in which basal forebrain cholinergic neurons were eliminated by previous infusion of 192IgG-saporin toxin into the medial septum. We found that estrogen-induced disinhibition and prolongation of IPSCs are entirely dependent on a tamoxifen-sensitive ER. Estrogen-induced disinhibition is partially dependent on basal forebrain cholinergic neurons, but the prolongation of IPSCs is not at all dependent on these cells. Paired-pulse experiments and recordings of action potential-related spontaneous IPSCs suggest that estrogen-induced disinhibition is associated with a decrease in probability of release at GABAergic synapses, which decreases the amplitude of IPSCs produced by inhibitory neuron action potentials. Our findings lend novel insights into estrogen regulation of inhibitory synapses in the hippocampus and point to estrogen action on basal forebrain cholinergic neurons as critically involved in mediating the effects of estrogen in the hippocampus.
Kv3.1b Is a Novel Component of CNS Nodes
Authors: Devaux Jérôme , Alcaraz Gisèle , Grinspan Judith , Bennett Vann , Joho Rolf , Crest Marcel , Scherer Steven S.
Published: April 2018

We herein demonstrate that Kv3.1b subunits are present at nodes of Ranvier in the CNS of both rats and mice. Kv3.1b colocalizes with voltage-gated Na+channels in a subset of nodes in the spinal cord, particularly those of large myelinated axons. Kv3.1b is abundantly expressed in the gray matter of the spinal cord, but does not colocalize with Na+channels in initial segments. In the PNS, few nodes are Kv3.1b-positive. During the development of the CNS, Kv3.1b clustering at nodes occurs later than that of Na+channels, but precedes the juxtaparanodal clustering of Kv1.2. Moreover, in myelin-deficient rats, which have severe CNS dysmyelination, node-like clusters of Kv3.1b and Na+channels are observed even in regions devoid of oligodendrocytes. Ankyrin G coimmunoprecipitates Kv3.1bin vivo, indicating that these two proteins may interact in the CNS at nodes. 4-Aminopyridine, a K+channel blocker, broadened the compound action potential recorded from adult rat optic nerve and spinal cord, but not from the sciatic nerve. These effects were also observed in Kv3.1-deficient mice. In conclusion, Kv3.1b is the first K+channel subunit to be identified in CNS nodes; but Kv3.1b does not account for the effects of 4-aminopyridine on central myelinated tracts.
Connexin 47 (Cx47)-Deficient Mice with Enhanced Green Fluorescent Protein Reporter Gene Reveal Predominant Oligodendrocytic Expression of Cx47 and Display Vacuolized Myelin in the CNS
Authors: Odermatt Benjamin , Wellershaus Kerstin , Wallraff Anke , Seifert Gerald , Degen Joachim , Euwens Carsten , Fuss Babette , Büssow Heinrich , Schilling Karl , Steinhäuser Christian , Willecke Klaus
Published: April 2018

To further characterize the recently described gap junction gene connexin 47 (Cx47), we generated Cx47-null mice by replacing the Cx47 coding DNA with an enhanced green fluorescent protein (EGFP) reporter gene, which was thus placed under control of the endogenous Cx47 promoter. Homozygous mutant mice were fertile and showed no obvious morphological or behavioral abnormalities. Colocalization of EGFP fluorescence and immunofluorescence of cell marker proteins revealed that Cx47 was mainly expressed in oligodendrocytes in highly myelinated CNS tissues and in few calcium-binding protein S100β subunit-positive cells but not in neurons or peripheral sciatic nerve. This corrects our previous conclusion that Cx47 mRNA is expressed in brain and spinal cord neurons (Teubner et al., 2001). Cx47 protein was detected by Western blot analysis after immunoprecipitation in CNS tissues of wild-type mice but not in heart or Cx47-deficient tissues. Electron microscopic analysis of CNS white matter in Cx47-deficient mice revealed a conspicuous vacuolation of nerve fibers, particularly at the site of the optic nerve where axons are first contacted by oligodendrocytes and myelination starts. Initial analyses of Cx32/Cx47-double-deficient mice showed that these mice developed an action tremor and died on average at 51 d after birth. The central white matter of these double-deficient mice exhibited much more abundant vacuolation in nerve fibers than mice deficient only in Cx47.
The Chemokine Stromal Cell-Derived Factor-1 Promotes the Survival of Embryonic Retinal Ganglion Cells
Authors: Chalasani Sreekanth H. , Baribaud Frédéric , Coughlan Christine M. , Sunshine Mary J. , Lee Virginia M. Y. , Doms Robert W. , Littman Dan R. , Raper Jonathan A.
Published: April 2018

The chemokine receptor CXCR4 is expressed in the embryonic and mature CNS, yet its normal physiological function in neurons remains obscure. Here, we show that its cognate chemokine, stromal cell-derived factor-1 (SDF-1), promotes the survival of cultured embryonic retinal ganglion cell neurons even in the absence of other neurotrophic factors. This survival effect is mediated primarily through a cAMP-dependent pathway that acts through protein kinase A and MAP kinase. Addition of SDF-1 to a human neuronal cell line induces phosphorylation of p44/p42 MAP kinase and GSK3β. Mouse embryos lacking the CXCR4 receptor have a reduced number of retinal ganglion cells. The ligand of CXCR4, SDF-1, may therefore provide generalized trophic support to neurons during their development and maturation.
The Distribution of Climbing and Mossy Fiber Collateral Branches from the Copula Pyramidis and the Paramedian Lobule: Congruence of Climbing Fiber Cortical Zones and the Pattern of Zebrin Banding within the Rat Cerebellum
Authors: Voogd Jan , Pardoe Joanne , Ruigrok Tom J. H. , Apps Richard
Published: April 2018

Individual cerebellar cortical zones defined by the somatotopy of climbing fiber responses and by their olivo-cortico-nuclear connections located in the paramedian lobule and the copula pyramidis of the rat cerebellum were microinjected with cholera toxin B subunit. Collateral branches of climbing and mossy fibers were mapped and related to the pattern of zebrin-positive and -negative bands of Purkinje cells. Climbing fiber collaterals from the copula distribute to the anterior lobe: from the paramedian lobule mainly to lobulus simplex and rostral crus I. Climbing fibers terminating in particular zones (X, A2, C1, CX, C2, C3, D1, and D2) in the paramedian lobule or the copula collateralize to one or two corresponding zones in lobulus simplex, crus I and II, the paraflocculus, and/or the anterior lobe. These zones can be defined by their relationship to the pattern of zebrin banding. Collaterals from mossy fibers, labeled from the same injection sites in the copula and paramedian lobule, often distribute bilaterally in a symmetrical pattern of multiple but ill-defined longitudinal strips in the anterior lobe and/or lobulus simplex. One or more of these longitudinal aggregates of mossy fiber collaterals was always found subjacent to the strip(s) of labeled climbing fiber collaterals arising from the same locus in the paramedian lobule or the copula. Corticonuclear projections focused on the target nucleus of each zone, although a bilateral plexus of thinner axons, presumably of mossy fiber collateral origin, was sometimes also present in several other regions of the cerebellar nuclei. Overall, these results suggest that climbing fiber zones and zebrin banding reflect a common organizational scheme within the cerebellar cortex.
Functional Reorganization of the Motor Cortex in Adult Rats after Cortical Lesion and Treatment with Monoclonal Antibody IN-1
Authors: Emerick April J. , Neafsey Edward J. , Schwab Martin E. , Kartje Gwendolyn L.
Published: April 2018

We previously reported anatomical plasticity in the adult motor cortex after a unilateral sensorimotor cortex (SMC) lesion and treatment with monoclonal antibody (mAb) IN-1, which permits neurite outgrowth from the intact, opposite cortex into deafferented subcortical targets. This study was designed to investigate whether treatment with the mAb IN-1 after SMC lesion in the adult leads to functional reorganization of the intact, opposite motor cortex. Adult rats underwent unilateral SMC aspiration lesion and treatment with either mAb IN-1 or control antibody, or no treatment. After a 6 week survival period, the intact, opposite forelimb motor cortex was explored using intracortical microstimulation to evoke forelimb movements. A dramatic increase in ipsilateral movements of the lesion-impaired forelimb was found in animals treated with mAb IN-1 compared with control animals. These results resembled our previous findings of cortical reorganization in the spared hemisphere after neonatal cortical lesion and without any additional treatment. These results show that, after adult cortical lesion, treatment with mAb IN-1 induces a functional reorganization of the intact, opposite motor cortex.
Increased Susceptibility of Striatal Mitochondria to Calcium-Induced Permeability Transition
Authors: Brustovetsky Nickolay , Brustovetsky Tatiana , Purl Kevin J. , Capano Michela , Crompton Martin , Dubinsky Janet M.
Published: April 2018

Mitochondria were simultaneously isolated from striatum and cortex of adult rats and compared in functional assays for their sensitivity to calcium activation of the permeability transition. Striatal mitochondria showed an increased dose-dependent sensitivity to Ca2+compared with cortical mitochondria, as measured by mitochondrial depolarization, swelling, Ca2+uptake, reactive oxygen species production, and respiration. Ratios of ATP to ADP were lower in striatal mitochondria exposed to calcium despite equal amounts of ADP and ATP under respiring and nonrespiring conditions. The Ca2+-induced changes were inhibited by cyclosporin A or ADP. These responses are consistent with Ca2+activation of both low and high permeability pathways constituting the mitochondrial permeability transition. In addition to the striatal supersensitivity to induction of the permeability transition, cyclosporin A inhibition was less potent in striatal mitochondria. Immunoblots indicated that striatal mitochondria contained more cyclophilin D than cortical mitochondria. Thus striatal mitochondria may be selectively vulnerable to the permeability transition. Subsequent mitochondrial dysfunction could contribute to the initial toxicity of striatal neurons in Huntington's disease.
ATP Inhibits NMDA Receptors after Heterologous Expression and in Cultured Hippocampal Neurons and Attenuates NMDA-Mediated Neurotoxicity
Authors: Ortinau Stefanie , Laube Bodo , Zimmermann Herbert
Published: April 2018

We investigated the potential of ATP to inhibit heterologously expressed NMDA receptor subunit combinations, NMDA-induced currents in cultured hippocampal cells, and NMDA-induced neurotoxicity. The effect of ATP on diheteromeric NR1a/NR2A-D NMDA receptor (NR) combinations expressed inXenopus laevisoocytes was studied by voltage-clamp recording. ATP strongly inhibited NMDA-induced inward currents only at the NR1a/NR2B receptor combination. At NMDA concentrations corresponding to the EC50value (20 μm), ATP revealed an IC50value of 135 μm. Mutation studies suggest that ATP exerts its inhibition via the glutamate-binding pocket of the NR2B subunit. Inosine 5′-triphosphate (ITP), GTP, and AMP also inhibited the recombinant NR1a/NR2B receptor, whereas UTP and CTP, ADP, or adenosine had no or only a small effect. Correspondingly, ATP inhibited NMDA-induced but not kainate-induced currents at cultured hippocampal neurons. An abundant expression of the NR2B subunit in the cultured neurons was verified by immunocytochemistry and blockade of NMDA-induced currents by the NR2B-selective antagonist ifenprodil. In addition we studied the role of ATP in NMDA-mediated neurotoxicity using cultured rat hippocampal cells. ATP exhibited a dose-dependent rescue effect when coapplied with the excitotoxicant NMDA, in contrast to ADP, AMP, and adenosine. The effect of ATP was mimicked by GTP and ITP but not by UTP and CTP. ATP had no effect on kainate-elicited neurotoxicity. Our results suggest that ATP can act as an inhibitor of NMDA receptors depending on receptor subunit composition and that it can attenuate NMDA-mediated neurotoxicity that is mediated neither by ATP nor by adenosine receptors.
Layer Specification of Transplanted Interneurons in Developing Mouse Neocortex
Authors: Valcanis Helen , Tan Seong-Seng
Published: April 2018

The six-layered neocortex is composed of excitatory projection neurons and inhibitory interneurons. Recent studies have established separate embryological origins for these two cellular populations. However, it remains uncertain how interneurons arising from the subcortical ganglionic eminences are able to participate in the orderly stratification of the cortical layers. A related question concerns whether or not early and late interneuron progenitors have equivalent developmental potentials. To address these issues, we performed transplantation experiments to test the fates of early-versus late-born interneuron populations using cells labeled with a genetic marker. Our results indicate that transplanted interneurons from the medial ganglionic eminence give rise to specific layers of the neocortex in an inside-out order. To test the potency of interneurons born at different ages, heterochronic transplantations were also performed. Both early- and late-born progenitors were able to switch their fates in the new environment, and, similar to projection neurons, fate-switching was dependent on progenitor receptivity to environmental cues during their last round of cell division. Our data also demonstrate, for the first time, that interneuron-layering cues are present within the medial ganglionic eminence, suggesting that, before the commencement of long-distance tangential migration, interneurons are already specified with respect to their future layer addresses. So, although the generation of diverse neuronal phenotypes in separate locations is an effective strategy to pursue separate developmental programs, our results indicate that excitatory and inhibitory neurons share similar mechanisms for integrating sequentially born neurons from two places into a single layered structure.
Human Embryonic Germ Cell Derivatives Facilitate Motor Recovery of Rats with Diffuse Motor Neuron Injury
Authors: Kerr Douglas A. , Lladó Jerònia , Shamblott Michael J. , Maragakis Nicholas J. , Irani David N. , Crawford Thomas O. , Krishnan Chitra , Dike Sonny , Gearhart John D. , Rothstein Jeffrey D.
Published: April 2018

We have investigated the potential of human pluripotent cells to restore function in rats paralyzed with a virus-induced motor neuronopathy. Cells derived from embryonic germ cells, termed embryoid body-derived (EBD) cells, introduced into the CSF were distributed extensively over the rostrocaudal length of the spinal cord and migrated into the spinal cord parenchyma in paralyzed, but not uninjured, animals. Some of the transplanted human cells expressed the neuroglial progenitor marker nestin, whereas others expressed immunohistochemical markers characteristic of astrocytes or mature neurons. Rare transplanted cells developed immunoreactivity to choline acetyltransferase (ChAT) and sent axons into the sciatic nerve as detected by retrograde labeling. Paralyzed animals transplanted with EBD cells partially recovered motor function 12 and 24 weeks after transplantation, whereas control animals remained paralyzed. Semi-quantitative analysis revealed that the efficiency of neuronal differentiation and extension of neurites could not account for the functional recovery. Rather, transplanted EBD cells protected host neurons from death and facilitated reafferentation of motor neuron cell bodies.In vitro, EBD cells secrete transforming growth factor-α (TGF-α) and brain-derived neurotrophic factor (BDNF). Neutralizing antibodies to TGF-α and to BDNF abrogated the ability of EBD-conditioned media to sustain motor neuron survival in culture, whereas neutralizing antibodies to BDNF eliminated the axonal outgrowth from spinal organotypics observed with direct coculture of EBD cells. We conclude that cells derived from human pluripotent stem cells have the capacity to restore neurologic function in animals with diffuse motor neuron disease via enhancement of host neuron survival and function.
Endogenously Produced Neurotrophins Regulate Survival and Differentiation of Cortical Progenitors via Distinct Signaling Pathways
Authors: Barnabé-Heider Fanie , Miller Freda D.
Published: April 2018

Cultured embryonic cortical progenitor cells will mimic the temporal differentiation pattern observedin vivo, producing neurons first and then glia. Here, we investigated the role of two endogenously produced growth factors, the neurotrophins brain-derived neurotrophic factor and neurotrophin-3 (NT-3), in the early progenitor-to-neuron transition. Cultured cortical progenitors express BDNF and NT-3, as well as their receptors TrkB (tyrosine kinase receptor B) and TrkC. Inhibition of these endogenously expressed neurotrophins using function-blocking antibodies resulted in a marked decrease in the survival of cortical progenitors, accompanied by decreased proliferation and inhibition of neurogenesis. Inhibition of neurotrophin function also suppressed the downstream Trk receptor signaling pathways, PI3-kinase (phosphatidyl inositol-3-kinase) and MEK—ERK (MAP kinase kinase—extracellular signal-regulated kinase), indicating the presence of autocrine—paracrine neurotrophin:Trk receptor signaling in these cells. Moreover, specific inhibition of these two Trk signaling pathways led to distinct biological effects; inhibition of PI3-kinase decreased progenitor cell survival, whereas inhibition of MEK selectively blocked the generation of neurons, with no effects on survival or proliferation. Thus, neurotrophins made by cortical progenitor cells themselves signal through the TrkB and TrkC receptors to mediate cortical progenitor cell survival and neurogenesis via two distinct downstream signaling pathways.
“Hey John”: Signals Conveying Communicative Intention toward the Self Activate Brain Regions Associated with “Mentalizing,” Regardless of Modality
Authors: Kampe Knut K. W. , Frith Chris D. , Frith Uta
Published: April 2018

Successful communication between two people depends first on the recognition of the intention to communicate. Such intentions may be conveyed by signals directed at the self, such as calling a person's name or making eye contact. In this study we use functional magnetic resonance imaging to show that the perception of these two signals, which differ in modality and sensory channel, activate common brain regions: the paracingulate cortex and temporal poles bilaterally. These regions are part of a network that has been consistently activated when people are asked to think about the mental states of others. Activation of this network is independent of arousal as measured by changes in pupil diameter.
Functional Disconnection of the Medial Prefrontal Cortex and Subthalamic Nucleus in Attentional Performance: Evidence for Corticosubthalamic Interaction
Authors: Chudasama Yogita , Baunez Christelle , Robbins Trevor W.
Published: April 2018

The present study used a disconnection procedure to test whether the medial prefrontal cortex (mPFC) and the subthalamic nucleus (STN) were functional components in a common neural system that controlled continuous performance in a test of sustained and divided visual attention. Animals with disconnected lesions of the mPFC and STN in contralateral hemispheres were severely impaired in several aspects of performance, including discriminative accuracy, increased perseveration, and slowed response latencies during postoperative testing. These deficits persisted throughout the entire experimental test period. Increasing the stimulus duration alleviated the accuracy deficit but failed to improve speed of responding or reduce perseverative responses. These deficits were in marked contrast to animals with combined mPFC and STN lesions made on the ipsilateral side, which produced behavior not different from that of sham controls. Rats with unilateral lesions of either structure alone were also impaired in terms of accuracy and perseveration. These data suggest that some of the deficits observed after bilateral STN lesions (attention and perseveration) may be attributable to a disrupted corticosubthalamic projection. This study provides direct evidence that performance in tasks that require optimal attentional and executive control relies on a corticosubthalamic interaction within the neural circuitry of the basal ganglia.
Evidence for Altered NMDA Receptor Function as a Basis for Metaplasticity in Visual Cortex
Authors: Philpot Benjamin D. , Espinosa Juan S. , Bear Mark F.
Published: April 2018

Sensory deprivation alters the properties of synaptic plasticity induced in the superficial layers of the visual cortex, facilitating long-term potentiation and reducing long-term depression (LTD) across a range of stimulation frequencies. Available data are compatible with either a downregulation of the mechanisms of LTD or an upregulation of NMDA receptor function in the visual cortex of dark-reared animals. Here, we provide evidence for enhanced NMDA receptor function by showing that deprivation produces a horizontal shift in the frequency-response function, decreasing LTD in response to 1 Hz stimulation, but increasing LTD in response to 0.5 Hz stimulation. In addition, we show that the effects of dark-rearing on the frequency dependence of LTD can be reversed acutely by partial NMDA receptor blockade. Finally, we show that anin vivomanipulation that rapidly downregulates NMDA receptor function in the visual cortex, brief light exposure, also rapidly reverses the effect of dark-rearing on LTD.
D3Dopamine Autoreceptors Do Not Activate G-Protein-Gated Inwardly Rectifying Potassium Channel Currents in Substantia Nigra Dopamine Neurons
Authors: Davila Viviana , Yan Zhen , Craciun Liviu C. , Logothetis Diomedes , Sulzer David
Published: April 2018

Substantia nigra (SN) dopamine neurons express D2and D3dopamine autoreceptors. A physiological role for the D3receptor has not been identified, but an activation of G-protein-gated inwardly rectifying potassium (GIRK; also known as Kir3) channels is strongly implicated because D3receptors activate channels composed of GIRK2 subunits in cell lines. We confirmed that acutely dissociated SN dopamine neurons indeed contain D3and GIRK2 subunit mRNA using single-cell RT-PCR. We then tested whether D3receptors activate GIRK currents in SN dopamine neurons by comparing acutely dissociated neurons from D2–/– receptor knock-out and congenic wild-type mice. In nearly all (14 of 15) wild-type SN dopamine neurons, the D2/D3agonist quinpirole activated GIRK currents that were blocked by cesium. Quinpirole, however, elicited no GIRK currents in any SN dopamine neuron (0 of 13) derived from D2–/– receptor knock-out mice. The absence of quinpirole response was not caused by a lack of GIRK activity, because the GABABreceptor agonist baclofen continued to elicit these currents in the mutant neurons. Thus, it appears that D3activation of GIRK currents in SN neurons does not occur or is exceedingly rare.
Estrogen Receptor β Mediates Rapid Estrogen Actions on Gonadotropin-Releasing Hormone NeuronsIn Vivo
Authors: Ábrahám István M. , Han Seong-Kyu , Todman Martin G. , Korach Kenneth S. , Herbison Allan E.
Published: April 2018

The gonadal steroid estrogen exerts an important modulatory influence on the activity of multiple neuronal networks. In addition to classical genomic mechanisms of action, estrogen also exerts poorly understood rapid, nongenomic effects on neurons. To examine whether estrogen may exert rapid actions on intracellular signaling within gonadotropin-releasing hormone (GnRH) neuronsin vivo,we examined the phosphorylation status of cAMP response element-binding protein (CREB) in these cells after the administration of 17-β-estradiol to ovariectomized (OVX) mice. The percentage of GnRH neurons expressing phosphorylated CREB was increased more than sixfold (p< 0.05) in a time- and dose-dependent manner by estrogen, with the increase first observed 15 min after estrogen administration. A series ofin vitrostudies demonstrated that estrogen acted directly on native GnRH neurons to phosphorylate CREB, but that estrogen conjugated to bovine serum albumin was without effect. The role of classical estrogen receptors (ERs) was evaluated using ER knock-out micein vivo. The effect of estrogen on CREB phosphorylation in GnRH neurons was normal in ERα knock-out mice but completely absent in ERβ knock-out mice. Finally, studies in intact female mice revealed levels of CREB phosphorylation within GnRH neurons that were equivalent to those of estrogen-treated OVX mice. These observations demonstrate that ERβ mediates the rapid, direct effects of estrogen on the GnRH neuronal phenotype, and that these actions persist under physiological conditions. They also provide the first evidence for a role of ERβ in nongenomic estrogen signaling within the brainin vivo.
Distinct Mechanisms for Processing Spatial Sequences and Pitch Sequences in the Human Auditory Brain
Authors: Warren J. D. , Griffiths T. D.
Published: April 2018

Perception of the acoustic world requires the simultaneous processing of the acoustic patterns associated with sound objects and their location in space. In this functional magnetic resonance experiment, we investigated the human brain areas engaged in the analysis of pitch sequences and sequences of acoustic spatial locations in a paradigm in which both could be varied independently. Subjects were presented with sequences of sounds in which the individual sounds were regular interval noises with variable pitch. Positions of individual sounds were varied using a virtual acoustic space paradigm during scanning. Sound sequences with changing pitch specifically activated lateral Heschl's gyrus (HG), anterior planum temporale (PT), planum polare, and superior temporal gyrus anterior to HG. Sound sequences with changing spatial locations specifically activated posteromedial PT. These results demonstrate directly that distinct mechanisms for the analysis of pitch sequences and acoustic spatial sequences exist in the human brain. This functional differentiation is evident as early as PT: within PT, pitch pattern is processed anterolaterally and spatial location is processed posteromedially. These areas may represent human homologs of macaque lateral and medial belt, respectively.
During Fictive Locomotion, Graded Synaptic Currents Drive Bursts of Impulses in Swimmeret Motor Neurons
Authors: Mulloney Brian
Published: April 2018

During forward swimming, motor neurons that innervate each crayfish swimmeret fire periodic coordinated bursts of impulses. These bursts occur simultaneously in neurons that are functional synergists but alternate with bursts in their antagonists. These impulses ride on periodic oscillations of membrane potential that occur simultaneously in neurons of each type. A model of the local circuit that generates this motor pattern has been proposed. In this model, each motor neuron is driven alternately by excitatory and inhibitory synaptic currents from nonspiking local interneurons. I tested this model by perturbing individual interneurons and recording synaptic currents and changes in input resistance from each class of motor neuron. I also simulated the synaptic currents that would be observed in a cell subject to different patterns of presynaptic input.

When the CNS was actively expressing the swimming motor pattern, changes in the membrane potential of individual local interneurons controlled firing of whole sets of motor neurons. Membrane currents in these motor neurons oscillated in phase with the motor output from their own local circuit. The phases of these oscillations differed in different functional classes of motor neurons. In neurons that could be clamped at the reversal potential of their outward currents, the model predicted that large periodic inward currents would be recorded. I observed no signs of periodic inward currents, even when the outward currents clearly had reversed.

These results permit a simplification of the cellular model. They are discussed in the context of neural control of locomotion in crustacea and insects.
Connexins Are Critical for Normal Myelination in the CNS
Authors: Menichella Daniela M. , Goodenough Daniel A. , Sirkowski Erich , Scherer Steven S. , Paul David L.
Published: April 2018

Mutations in Cx32, a gap-junction channel-forming protein, result in X-linked Charcot–Marie–Tooth disease, a demyelinating disease of the peripheral nervous system. However, although oligodendrocytes express Cx32, central myelination is unaffected. To explore this discrepancy, we searched for additional oligodendrocyte connexins. We found Cx47, which is expressed specifically in oligodendrocytes, regulated in parallel with myelin genes and partially colocalized with Cx32 in oligodendrocytes. Mice lacking either Cx47 or Cx32 are viable. However, animals lacking both connexins die by postnatal week 6 from profound abnormalities in central myelin, characterized by thin or absent myelin sheaths, vacuolation, enlarged periaxonal collars, oligodendrocyte cell death, and axonal loss. These data provide the first evidence that gap-junction communication is crucial for normal central myelination.