bluuebunny/crossref_metadata_2025 huggingface dataset:
Transcription Factor Expression and Notch-Dependent Regulation of Neural Progenitors in the Adult Rat Spinal Cord
Authors: Yamamoto Shin-ichi , Nagao Motoshi , Sugimori Michiya , Kosako Hidetaka , Nakatomi Hirofumi , Yamamoto Naoya , Takebayashi Hirohide , Nabeshima Yo-ichi , Kitamura Toshio , Weinmaster Gerry , Nakamura Kozo , Nakafuku Masato
Published: April 2018

Recent studies have demonstrated that neural stem cells and other progenitors are present in the adult CNS. Details of their properties, however, remain poorly understood. Here we examined the properties and control mechanisms of neural progenitors in the adult rat spinal cord at the molecular level. Adult and embryonic progenitors commonly expressed various homeodomain-type (Pax6, Pax7, Nkx2.2, and Prox1) and basic helix–loop–helix (bHLH)-type (Ngn2, Mash1, NeuroD1, and Olig2) transcriptional regulatory factorsin vitro. Unlike their embryonic counterparts, however, adult progenitors could not generate specific neurons that expressed markers appropriate for spinal motoneurons or interneurons, including Islet1, Lim1, Lim3, and HB9. Cells expressing the homeodomain factors Pax6, Pax7, and Nkx2.2 also emergedin vivoin response to injury and were distributed in unique patterns in the lesioned spinal cord. However, neither the expression of the neurogenic bHLH factors including Ngn2, Mash1, and NeuroD1 nor subsequent generation of new neurons could be detected in injured tissue. Our results suggest that signaling through the cell-surface receptor Notch is involved in this restriction. The expression of Notch1in vivowas enhanced in response to injury. Furthermore, activation of Notch signalingin vitroinhibited differentiation of adult progenitors, whereas attenuation of Notch signals and forced expression of Ngn2 significantly enhanced neurogenesis. These results suggest that both the intrinsic properties of adult progenitors and local environmental signals, including Notch signaling, account for the limited regenerative potential of the adult spinal cord.
cAMP Response Element-Binding Protein Is Required for Dopamine-Dependent Gene Expression in the Intact But Not the Dopamine-Denervated Striatum
Authors: Andersson Malin , Konradi Christine , Cenci M. Angela
Published: April 2018

The cAMP response element-binding protein (CREB) is believed to play a pivotal role in dopamine (DA) receptor-mediated nuclear signaling and neuroplasticity. Here we demonstrate that the significance of CREB for gene expression depends on the experimental paradigm. We compared the role of CREB in two different but related models:l-DOPA administration to unilaterally 6-hydroxydopamine lesioned rats, and cocaine administration to neurologically intact animals. Antisense technology was used to produce a local knockdown of CREB in the lateral caudate–putamen, a region that mediates the dyskinetic or stereotypic manifestations associated withl-DOPA or cocaine treatment, respectively. In intact rats, CREB antisense reduced both basal and cocaine-induced expression of c-Fos, FosB/ΔFosB, and prodynorphin mRNA. In the DA-denervated striatum, CREB was not required forl-DOPA to induce these gene products, nor did CREB contribute considerably to DNA binding activity at cAMP responsive elements (CREs) and CRE-like enhancers. ΔFosB-related proteins and JunD were the main contributors to both CRE and AP-1 DNA–protein complexes inl-DOPA-treated animals. In behavioral studies, intrastriatal CREB knockdown caused enhanced activity scores in intact control animals and exacerbated the dyskinetic effects of acutel-DOPA treatment in 6-OHDA-lesioned animals. These data demonstrate that CREB is not required for the development ofl-DOPA-induced dyskinesia in hemiparkinsonian rats. Moreover, our results reveal an unexpected alteration of nuclear signaling mechanisms in the parkinsonian striatum treated withl-DOPA, where AP-1 transcription factors appear to supersede CREB in the activation of CRE-containing genes.
Impaired Spatial Cognition and Synaptic Potentiation in a Murine Model of Human Immunodeficiency Virus Type 1 Encephalitis
Authors: Zink Walter E. , Anderson Eric , Boyle Jeffrey , Hock Lynette , Rodriguez-Sierra Jorge , Xiong Huangui , Gendelman Howard E. , Persidsky Yuri
Published: April 2018

Injection of human immunodeficiency virus type 1 (HIV-1)-infected human monocyte-derived macrophages (MDMs) into the basal ganglia of severe combined immunodeficient mice recapitulates histopathologic features of HIV-1 encephalitis (HIVE). Here, we show that the neural damage in HIVE mice extends beyond the basal ganglia and is associated with cognitive impairment. Morris water maze tests showed impaired spatial learning 8 d after MDM injection. Moreover, impaired synaptic potentiation in the hippocampal CA1 subregion was demonstrated at 8 and 15 d. By day 15, post-tetanic, short-term, and long-term potentiation were reduced by 14.1, 29.5, and 45.3% in HIVE mice compared with sham-injected or control animals. Neurofilament (NF) and synaptophysin (SP) antigens were decreased significantly in the CA2 hippocampal subregion of HIVE mice with limited neuronal apoptosis. By day 15, the CA2 region of HIVE mice expressed 3.8- and 2.6-fold less NF and SP than shams. These findings support the notion that HIV-1-infected and immune-competent brain macrophages can cause neuronal damage at distant anatomic sites. Importantly, the findings demonstrate the value of the model in exploring the physiological basis and therapeutic potential for HIV-1-associated dementia.
Estrogen Protects against Global Ischemia-Induced Neuronal Death and Prevents Activation of Apoptotic Signaling Cascades in the Hippocampal CA1
Authors: Jover Teresa , Tanaka Hidenobu , Calderone Agata , Oguro Keiji , Bennett Michael V. L. , Etgen Anne M. , Zukin R. Suzanne
Published: April 2018

The importance of postmenopausal estrogen replacement therapy in affording protection against the selective and delayed neuronal death associated with cardiac arrest or cardiac surgery in women remains controversial. Here we report that exogenous estrogen at levels that are physiological for hormone replacement in postmenopausal women affords protection against global ischemia-induced neuronal death and prevents activation of apoptotic signaling cascades in the hippocampal CA1 of male gerbils. Global ischemia induced a marked increase in activated caspase-3 in CA1, evident at 6 hr after ischemia. Global ischemia induced a marked upregulation of the proapoptotic neurotrophin receptor p75NTRin CA1, evident at 48 hr. p75NTRexpression was induced primarily in terminal deoxynucleotidyl transferase-mediated UTP nick-end labeling-positive cells, indicating expression in neurons undergoing apoptosis. Global ischemia also induced a marked downregulation of mRNA encoding the AMPA receptor GluR2 subunit in CA1. Caspase-3, p75NTR, and GluR2 were not significantly changed in CA3 and dentate gyrus, indicating that the ischemia-induced changes in gene expression were cell specific. Exogenous estrogen attenuated the ischemia-induced increases in activated caspase-3 and blocked the increase in p75NTRin post-ischemic CA1 neurons but did not prevent ischemia-induced downregulation of GluR2. These findings demonstrate that long-term estrogen at physiological levels ameliorates ischemia-induced hippocampal injury and indicate that estrogen intervenes at the level of apoptotic signaling cascades to prevent onset of death in neurons otherwise “destined to die.”
Cell Cycle Proteins Exhibit Altered Expression Patterns in Lentiviral-Associated Encephalitis
Authors: Jordan-Sciutto Kelly L. , Wang Guoji , Murphey-Corb Michael , Wiley Clayton A.
Published: April 2018

Cell cycle proteins regulate processes as diverse as cell division and cell death. Recently their role in neuronal death has been reported in several models of neurodegeneration. We have reported previously that two key regulators of the cell cycle, the retinoblastoma susceptibility gene product (pRb) and transcription factor E2F1, exhibit altered immunostaining patterns in simian immunodeficiency virus encephalitis (SIVE). Here we show that E2F1 and the inactivated, hyperphosphorylated form of pRb (ppRb) also exhibit altered immunostaining patterns in human immunodeficiency virus encephalitis (HIVE). Quantification of E2F1 and ppRb staining by immunofluorescent confocal microscopy confirms a significant increase in E2F1 and ppRb in both HIVE and the simian model. This increase in E2F1 and ppRb staining correlates with an increase in the presence of activated macrophages, suggesting a link between changes in cell cycle proteins and the presence of activated macrophages. Changes in ppRb and E2F1 staining in SIVE also correlate with alterations in E2F/DNA binding complexes present in the nuclear and cytoplasmic fractions from both midfrontal cortex and basal ganglia. These findings suggest that changes in cell cycle proteins occur in both HIVE and the simian model and that these changes have functional implications for gene expression in neural cells under encephalitic conditions mediated by macrophage activation or infiltration.
Neuregulin Expression at Neuromuscular Synapses Is Modulated by Synaptic Activity and Neurotrophic Factors
Authors: Loeb Jeffrey A. , Hmadcha Abdelkrim , Fischbach Gerald D. , Land Susan J. , Zakarian Vaagn L.
Published: April 2018

The proper formation of neuromuscular synapses requires ongoing synaptic activity that is translated into complex structural changes to produce functional synapses. One mechanism by which activity could be converted into these structural changes is through the regulated expression of specific synaptic regulatory factors. Here we demonstrate that blocking synaptic activity with curare reduces synaptic neuregulin expression in a dose-dependent manner yet has little effect on synaptic agrin or a muscle-derived heparan sulfate proteoglycan. These changes are associated with a fourfold increase in number and a twofold reduction in average size of synaptic acetylcholine receptor clusters that appears to be caused by excessive axonal sprouting with the formation of new, smaller acetylcholine receptor clusters. Activity blockade also leads to threefold reductions in brain-derived neurotrophic factor and neurotrophin 3 expression in muscle without appreciably changing the expression of these same factors in spinal cord. Adding back these or other neurotrophic factors restores synaptic neuregulin expression and maintains normal end plate band architecture in the presence of activity blockade. The expression of neuregulin protein at synapses is independent of spinal cord and muscle neuregulin mRNA levels, suggesting that neuregulin accumulation at synapses is independent of transcription. These findings suggest a local, positive feedback loop between synaptic regulatory factors that translates activity into structural changes at neuromuscular synapses.
Activity of Thalamic Reticular Neurons during Spontaneous Genetically Determined Spike and Wave Discharges
Authors: Slaght Seán J. , Leresche Nathalie , Deniau Jean-Michel , Crunelli Vincenzo , Charpier Stéphane
Published: April 2018

This study reports the first intracellular recordings obtained during spontaneous, genetically determined spike and wave discharges (SWDs) in nucleus reticularis thalami (NRT) neurons from the genetic absence epilepsy rats from Strasbourg (GAERS), a model that closely reproduces the typical features of childhood absence seizures.

A SWD started with a large hyperpolarization, which was independent of the preceding firing, and decreased in amplitude but did not reverse in polarity up to potentials ≥ −90 mV. This hyperpolarization and the slowly decaying depolarization that terminated a SWD were unaffected by recording with KCl-filled electrodes. The prolonged (up to 15 action potentials), high-frequency bursts present during SWDs were tightly synchronized between adjacent neurons, correlated with the EEG spike component, and generated by a low-threshold Ca2+potential, which, in turn, was brought about by the summation of high-frequency, small-amplitude depolarizing potentials.

Fast hyperpolarizing IPSPs were not detected either during or in the absence of SWDs. Recordings with KCl-filled electrodes, however, showed a more depolarized resting membrane potential and a higher background firing, whereas the SWD-associated bursts had a longer latency to the EEG spike and a lower intraburst frequency. This novel finding demonstrates that spontaneous genetically determined SWDs occur in the presence of intra-NRT lateral inhibition.

The unmasking of these properties in the GAERS NRT confirms their unique association with spontaneous genetically determined SWDs and thus their likely involvement in the pathophysiological processes of the human condition.
Lower Sensitivity to Stress and Altered Monoaminergic Neuronal Function in Mice Lacking the NMDA Receptor ε4 Subunit
Authors: Miyamoto Yoshiaki , Yamada Kiyofumi , Noda Yukihiro , Mori Hisashi , Mishina Masayoshi , Nabeshima Toshitaka
Published: April 2018

NMDA receptors, an ionotropic subtype of glutamate receptors (GluRs), play an important role in excitatory neurotransmission, synaptic plasticity, and brain development. They are composed of the GluRζ subunit (NR1) combined with any one of four GluRε subunits (GluRε1–GluRε4; NR2A–NR2D). Although the GluRζ subunit exists in the majority of the CNS throughout all stages of development, the GluRε subunits are expressed in distinct temporal and spatial patterns. In the present study, we investigated neuronal functions in mice lacking the embryonic GluRε4 subunit. GluRε4 mutant mice exhibited reductions of [3H]MK-801 [(+)-5-methyl-10,11-dihydro-5H-dibenzo [a,d] cyclohepten-5,10-imine maleate] binding and45Ca2+uptake through the NMDA receptors. The expression of GluRζ subunit protein, but not GluRε1 and GluRε2 subunit proteins, was reduced in the frontal cortex and striatum of the mutant mice. A postmortem examination in GluRε4 mutant mice revealed that tissue contents of norepinephrine, dopamine, serotonin, and their metabolites were reduced in the hippocampus and that dopamine, as well as serotonin, metabolism was upregulated in the frontal cortex, striatum, hippocampus, and thalamus. To clarify the phenotypical influences of the alteration in neuronal functions, performances in various behavioral tests were examined. GluRε4 mutant mice showed reduced spontaneous locomotor activity in a novel environment and less sensitivity to stress induced by the elevated plus-maze, light–dark box, and forced swimming tests. These findings suggest that GluRε4 mutant mice have dysfunctional NMDA receptors and altered emotional behavior probably caused by changes in monoaminergic neuronal activities in adulthood.
Stimulus Encoding and Feature Extraction by Multiple Sensory Neurons
Authors: Krahe Rüdiger , Kreiman Gabriel , Gabbiani Fabrizio , Koch Christof , Metzner Walter
Published: April 2018

Neighboring cells in topographical sensory maps may transmit similar information to the next higher level of processing. How information transmission by groups of nearby neurons compares with the performance of single cells is a very important question for understanding the functioning of the nervous system. To tackle this problem, we quantified stimulus-encoding and feature extraction performance by pairs of simultaneously recorded electrosensory pyramidal cells in the hindbrain of weakly electric fish. These cells constitute the output neurons of the first central nervous stage of electrosensory processing. Using random amplitude modulations (RAMs) of a mimic of the fish's own electric field within behaviorally relevant frequency bands, we found that pyramidal cells with overlapping receptive fields exhibit strong stimulus-induced correlations. To quantify the encoding of the RAM time course, we estimated the stimuli from simultaneously recorded spike trains and found significant improvements over single spike trains. The quality of stimulus reconstruction, however, was still inferior to the one measured for single primary sensory afferents. In an analysis of feature extraction, we found that spikes of pyramidal cell pairs coinciding within a time window of a few milliseconds performed significantly better at detecting upstrokes and downstrokes of the stimulus compared with isolated spikes and even spike bursts of single cells. Coincident spikes can thus be considered “distributed bursts.” Our results suggest that stimulus encoding by primary sensory afferents is transformed into feature extraction at the next processing stage. There, stimulus-induced coincident activity can improve the extraction of behaviorally relevant features from the stimulus.
The Toll-Like Receptor TLR4 Is Necessary for Lipopolysaccharide-Induced Oligodendrocyte Injury in the CNS
Authors: Lehnardt Seija , Lachance Christian , Patrizi Silvia , Lefebvre Sharon , Follett Pamela L. , Jensen Frances E. , Rosenberg Paul A. , Volpe Joseph J. , Vartanian Timothy
Published: April 2018

The immediate or innate immune response is the first line of defense against diverse microbial pathogens and requires the expression of recently discovered toll-like receptors (TLRs). TLR4 serves as a specific receptor for lipopolysaccharide (LPS) and is localized on the surface of a subset of mammalian cells. Although innate immunity is a necessary host defense against microbial pathogens, the consequences of its activation in the CNS can be deleterious, as we show here in a developing neural model. We examined the major non-neuronal cell types in the CNS for expression of TLR4 and found that microglia expressed high levels, whereas astrocytes and oligodendrocytes expressed none. Consistent with TLR4 expression solely in microglia, we show that microglia are the only CNS glial cells that bind fluorescently tagged lipopolysaccharide. Lipopolysaccharide led to extensive oligodendrocyte death in culture only under conditions in which microglia were present. To determine whether TLR4 is necessary for lipopolysaccharide-induced oligodendrocyte death in mixed glial cultures, we studied cultures generated from mice bearing a loss-of-function mutation in thetlr4gene. Lipopolysaccharide failed to induce oligodendrocyte death in such cultures, in contrast to the death induced in cultures from wild-type mice. Finally, stereotactic intracerebral injection of lipopolysaccharide into the developing pericallosal white matter of immature rodents resulted in loss of oligodendrocytes and hypomyelination and periventricular cysts. Our data provide a general mechanistic link between (1) lipopolysaccharide and similar microbial molecular motifs and (2) injury to oligodendrocytes and myelin as occurs in periventricular leukomalacia and multiple sclerosis.
Myosin-1c Interacts with Hair-Cell Receptors through Its Calmodulin-Binding IQ Domains
Authors: Cyr Janet L. , Dumont Rachel A. , Gillespie Peter G.
Published: April 2018

Myosin-1c plays an essential role in adaptation of hair-cell mechanoelectrical transduction. To mediate adaptation, myosin-1c must interact directly or indirectly with other components of the transduction apparatus, including the mechanically gated transduction channel. As a first step toward identifying myosin-1c receptors, we used recombinant myosin-1c fragments to identify specific binding sites in hair cells and to biochemically characterize their interaction with myosin-1c. Myosin-1c fragments bound to tips of hair-cell stereocilia, the location of transduction and adaptation. Surprisingly, this interaction did not depend on the C-terminal tail of myosin-1c, proposed previously to be the receptor-binding site of the molecule. Instead, the interaction of myosin-1c with stereociliary receptors depended on its calmodulin-binding IQ domains. This interaction was blocked by calmodulin, which probably bound to a previously unoccupied IQ domain of myosin-1c. The calcium-sensitive binding of calmodulin to myosin-1c may therefore modulate the interaction of the adaptation motor with other components of the transduction apparatus.
Involvement of the α3 Subunit in Central Nicotinic Binding Populations
Authors: Whiteaker Paul , Peterson Cyrus G. , Xu Wei , McIntosh J. Michael , Paylor Richard , Beaudet Arthur L. , Collins Allan C. , Marks Michael J.
Published: April 2018

The α3 subunit gene was one of the first neuronal nicotinic acetylcholine receptor (nAChR) subunits to be cloned (Boulter et al., 1986), but direct evidence of α3 subunit contributions to mammalian central nAChR populations has not been presented. The studies reported here used mice engineered to contain a null mutation in the α3 nAChR subunit gene (Xu et al., 1999) to examine the involvement of the α3 subunit in central nAChR populations. Heterologously expressed α3β2 and α3β4 nAChRs are pharmacologically similar to native [125I]α-conotoxin MII (α-CtxMII)-binding and 3-(2(S)-azetidinylmethoxy)pyridine dihydrochloride (A85380)-resistant [125I]epibatidine-binding nAChR subtypes, respectively. The hypothesis that both native sites are α3-subtype nAChRs was tested using quantitative autoradiography in α3-null mutant mice. Somewhat surprisingly, deletion of the α3 nAChR subunit gene did not affect expression of the great majority of [125I]α-CtxMII-binding sites, indicating that they do not correspond to heterologously expressed α3β2 nAChRs. The only exception to this was observed in the habenulointerpeduncular tract, where α3-dependent [125I]α-CtxMII binding was observed. This finding may suggest the presence of an additional, minor nicotinic population in this pathway. In contrast, mostA85380-resistant [125I]epibatidine-binding nAChRs were dependent on α3 gene expression, suggesting that they do indeed correspond to an α3 nAChR subtype. However, widespread but lower levels of α3-independentA85380-resistant [125I]epibatidine binding were also seen. Again, this may indicate the existence of an additional, minor population of non-α3A85380-resistant sites.
Nicotinic Acetylcholine Receptors Interact with Dopamine in Induction of Striatal Long-Term Depression
Authors: Partridge John G. , Apparsundaram Subbu , Gerhardt Greg A. , Ronesi Jennifer , Lovinger David M.
Published: April 2018

The dorsal striatum participates in motor function and stimulus–response or “habit” learning. Acetylcholine (ACh) is a prominent neurotransmitter in the striatum and exerts part of its actions through nicotinic cholinergic receptors. Activation of these receptors has been associated with the enhancement of learning and certainly is instrumental in habitual use of nicotine. Nicotinic receptors have also been suggested to be a possible therapeutic target for disorders of the basal ganglia. In this report we show that the activation of nicotinic acetylcholine receptors in the dorsal striatum contributes to dopamine (DA)- and activity-dependent changes in synaptic efficacy. High-frequency activation of glutamatergic synapses onto striatal neurons results in a long-term depression (LTD) of synaptic efficacy that is dependent on the activation of dopamine receptors. This stimulation also produces robust increases in extracellular dopamine concentration as well as strong activation of cholinergic striatal interneurons. Antagonists of nicotinic acetylcholine receptors inhibit striatal LTD. However, on coapplication of dopamine reuptake inhibitors with nicotinic receptor antagonists, activity-induced striatal LTD is restored. Dopamine release is modulated by activation of nicotinic receptors in the dorsal striatum, and activation of nicotinic receptors during high-frequency synaptic activation appears to be capable of interacting with dopaminergic actions that lead to striatal LTD. Our results suggest that stimulation of mechanisms involved in striatal synaptic plasticity is an important role for striatal nicotinic acetylcholine receptors and that these mechanisms may contribute to the enhancement of learning and habit formation produced by nicotine intake.
Caspase Inhibitors Attenuate 1-Methyl-4-Phenylpyridinium Toxicity in Primary Cultures of Mesencephalic Dopaminergic Neurons
Authors: Bilsland James , Roy Sophie , Xanthoudakis Steve , Nicholson Donald W. , Han Yongxin , Grimm Erich , Hefti Franz , Harper Sarah J.
Published: April 2018

Parkinson's disease is characterized by a loss of dopaminergic nigrostriatal neurons. This neuronal loss is mimicked by the neurotoxin 1-methyl-4-phenylpyridinium (MPP+). MPP+toxicity is mediated through inhibition of mitochondrial complex I, decreasing ATP production, and upregulation of oxygen radicals. There is evidence that the cell death induced by MPP+is apoptotic and that inhibition of caspases may be neuroprotective. In primary cultures of rat mesencephalic dopaminergic neurons, MPP+treatment decreased the number of surviving dopaminergic neurons in the cultures and the ability of the neurons to take up [3H]dopamine ([3H]DA). Caspase inhibition using the broad-spectrum inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (zVAD-fmk) spared MPP+-treated dopaminergic neurons and increased somatic size. There was a partial restoration of neurite length in zVAD-fmk-treated cultures, but little restoration of [3H]DA uptake. Peptide inhibitors of caspases 2, 3, and 9, but not of caspase 1, caused significant neuroprotection. Two novel caspase inhibitors were tested for neuroprotection, a broad spectrum inhibitor and a selective caspase 3 inhibitor; both inhibitors increased survival to >90% of control. No neuroprotection was observed with an inactive control compound. MPP+treatment caused chromatin condensation in dopaminergic neurons and increased expression of activated caspase 3. Inhibition of caspases with either zVAD-fmk or a selective caspase 3 inhibitor decreased the number of apoptotic profiles, but not expression of the active caspase. We conclude that MPP+toxicity in primary dopaminergic neurons involves activation of a pathway terminating in caspase 3 activation, but that other mechanisms may underlie the neurite loss.
Pathological CNS Autoimmune Disease Triggered by Traumatic Spinal Cord Injury: Implications for Autoimmune Vaccine Therapy
Authors: Jones T. Bucky , Basso D. Michele , Sodhi Ajeet , Pan Jonathan Z. , Hart Ronald P. , MacCallum Robert C. , Lee Sunhee , Whitacre Caroline C. , Popovich Phillip G.
Published: April 2018

Lymphocytes respond to myelin proteins after spinal cord injury (SCI) and may contribute to post-traumatic secondary degeneration. However, there is increasing evidence that autoreactive T-lymphocytes may also convey neuroprotection and promote functional recovery after CNS injury. To clarify the role of myelin autoreactive lymphocytes after SCI, we performed contusion injuries in the thoracic spinal cord of transgenic (Tg) mice in which >95% of all CD4+ T-lymphocytes are reactive with myelin basic protein (MBP). We observed significantly impaired recovery of locomotor and reflex function in Tg mice compared with non-Tg (nTg) littermates. Measures of functional impairment in Tg mice correlated with significantly less white matter at the injury site, and morphometric comparisons of injured Tg and nTg spinal cords revealed increased rostrocaudal lesion expansion (i.e., secondary degeneration) in Tg mice. Rostrocaudal to the impact site in SCI–nTg mice, demyelination was restricted to the dorsal funiculus, i.e., axons undergoing Wallerian degeneration. The remaining white matter appeared normal. In contrast, lymphocytes were colocalized with regions of demyelination and axon loss throughout the white matter of SCI–Tg mice. Impaired neurological function and exacerbated neuropathology in SCI–Tg mice were associated with increased intraspinal production of proinflammatory cytokine mRNA; neurotrophin mRNA was not elevated. These data suggest that endogenous MBP-reactive lymphocytes, activated by traumatic SCI, can contribute to tissue injury and impair functional recovery. Any neuroprotection afforded by myelin-reactive T-cells is likely to be an indirect effect mediated by other non-CNS-reactive lymphocytes. Similar to the Tg mice in this study, a subset of humans that are genetically predisposed to autoimmune diseases of the CNS may be adversely affected by vaccine therapies designed to boost autoreactive lymphocyte responses after CNS trauma. Consequently, the safe implementation of such therapies requires that future studies define the mechanisms that control T-cell function within the injured CNS.
CNS Site of Action and Brainstem Circuitry Responsible for the Intravenous Effects of Nicotine on Gastric Tone
Authors: Ferreira Manuel , Sahibzada Niaz , Shi Min , Panico William , Niedringhaus Mark , Wasserman Adam , Kellar Kenneth J. , Verbalis Joseph , Gillis Richard A.
Published: April 2018

The purposes of our study were to determine (1) the effects of intravenous (i.v.) nicotine on gastric mechanical function of anesthetized rats, (2) the CNS site of action of nicotine to produce these effects, (3) the CNS nicotinic acetylcholine receptor (nAChR) subtype(s) responsible for mediating the i.v. effects of nicotine, and (4) the brainstem neurocircuitry engaged by i.v. nicotine for eliciting its gastric effects. This was accomplished by monitoring intragastric pressure (gastric tone) and contractility of the fundus and antrum while administering five doses of i.v. nicotine and microinjecting nicotine into specific brainstem nuclei. Additionally, c-Fos expression in the brainstem after i.v. nicotine and pharmacological agents were used as tools to identify the CNS site and circuitry and reveal the nAChR subtype(s) mediating the gastric effects of nicotine. Using these experimental approaches, we found the following. (1) When given intravenously in doses of 56.5, 113, 226, 452, and 904 nmol/kg, nicotine elicited only inhibitory effects on gastric mechanical function. The most sensitive area of the stomach to nicotine was the fundus, and this effect was mediated by the vagus nerve at doses of 56.5, 113, and 226 nmol/kg. (2) The CNS site of action and nAChR subtype responsible were glutamatergic vagal afferent nerve terminals in the medial subnucleus of the tractus solitarious (mNTS) and α4β2, respectively. (3) The brainstem neurocircuitry that was involved appeared to consist of a mNTS noradrenergic pathway projecting to the dorsal motor nucleus of the vagus (DMV). This pathway seems to be activated via nitriergic interneurons engaged by vagally released glutamate in the mNTS and results in α2 adrenergic receptor-mediated inhibition of DMV neurons projecting to the fundus and controlling gastric tone.
Cortical Activation during Spoken-Word Segmentation in Nonreading-Impaired and Dyslexic Adults
Authors: Helenius Päivi , Salmelin Riitta , Service Elisabet , Connolly John F. , Leinonen Seija , Lyytinen Heikki
Published: April 2018

We used magnetoencephalography to elucidate the cortical activation associated with the segmentation of spoken words in nonreading-impaired and dyslexic adults. The subjects listened to binaurally presented sentences where the sentence-ending words were either semantically appropriate or inappropriate to the preceding sentence context. Half of the inappropriate final words shared two or three initial phonemes with the highly expected semantically appropriate words. Two temporally and functionally distinct response patterns were detected in the superior temporal lobe. The first response peaked at ∼100 msec in the supratemporal plane and showed no sensitivity to the semantic appropriateness of the final word. This presemantic N100m response was abnormally strong in the left hemisphere of dyslexic individuals. After the N100m response, the semantically inappropriate sentence-ending words evoked stronger activation than the expected endings in the superior temporal cortex in the vicinity of the auditory cortex. This N400m response was delayed for words starting with the same two or three first few phonemes as the expected words but only until the first evidence of acoustic–phonetic dissimilarity emerged. This subtle delay supports the notion of initial lexical access being based on phonemes or acoustic features. In dyslexic participants, this qualitative aspect of word processing appeared to be normal. However, for all words alike, the ascending slope of the semantic activation in the left hemisphere was delayed by ∼50 msec as compared with control subjects. The delay in the auditory N400m response in dyslexic subjects is likely to result from presemantic–phonological deficits possibly reflected in the abnormal N100m response.
Neuron-to-Glia Signaling Mediated by Excitatory Amino Acid Receptors Regulates ErbB Receptor Function in Astroglial Cells of the Neuroendocrine Brain
Authors: Dziedzic Barbara , Prevot Vincent , Lomniczi Alejandro , Jung Heike , Cornea Anda , Ojeda Sergio R.
Published: April 2018

Hypothalamic astroglial erbB tyrosine kinase receptors are required for the timely initiation of mammalian puberty. Ligand-dependent activation of these receptors sets in motion a glia-to-neuron signaling pathway that prompts the secretion of luteinizing hormone-releasing hormone (LHRH), the neuropeptide controlling sexual development, from hypothalamic neuroendocrine neurons. The neuronal systems that may regulate this growth factor-mediated back signaling to neuroendocrine neurons have not been identified. Here we demonstrate that hypothalamic astrocytes contain metabotropic receptors of the metabotropic glutamate receptor 5 subtype and the AMPA receptor subunits glutamate receptor 2 (GluR2) and GluR3. As in excitatory synapses, these receptors are in physical association with their respective interacting/clustering proteins Homer and PICK1. In addition, they are associated with erbB-1 and erbB-4 receptors. Concomitant activation of astroglial metabotropic and AMPA receptors results in the recruitment of erbB tyrosine kinase receptors and their respective ligands to the glial cell membrane, transactivation of erbB receptors via a mechanism requiring metalloproteinase activity, and increased erbB receptor gene expression. By facilitating erbB-dependent signaling and promoting erbB receptor gene expression in astrocytes, a neuron-to-glia glutamatergic pathway may represent a basic cell–cell communication mechanism used by the neuroendocrine brain to coordinate the facilitatory transsynaptic and astroglial input to LHRH neurons during sexual development.
Evidence from Functional Neuroimaging of a Compensatory Prefrontal Network in Alzheimer's Disease
Authors: Grady Cheryl L. , McIntosh Anthony R. , Beig Sania , Keightley Michelle L. , Burian Hana , Black Sandra E.
Published: April 2018

Previous experiments have found that individuals with Alzheimer's disease (AD) show increased activity in prefrontal regions compared with healthy age-matched controls during cognitive tasks. This has been interpreted as compensatory reallocation of cognitive resources, but direct evidence for a facilitating effect on performance has been lacking. To address this we measured neural activity during semantic and episodic memory tasks in mildly demented AD patients and healthy elderly controls. Controls recruited a left hemisphere network of regions, including prefrontal and temporal cortices in both the semantic and episodic tasks. Patients engaged a unique network involving bilateral dorsolateral prefrontal and posterior cortices. Critically, activity in this network of regions was correlated with better performance on both the semantic and episodic tasks in the patients. This provides the most direct evidence to date that AD patients can use additional neural resources in prefrontal cortex, presumably those mediating executive functions, to compensate for losses attributable to the degenerative process of the disease.
Molecular Evidence for the Functional Role of Dopamine D3Receptor in the Morphine-Induced Rewarding Effect and Hyperlocomotion
Authors: Narita Minoru , Mizuo Keisuke , Mizoguchi Hirokazu , Sakata Mamoru , Narita Michiko , Tseng Leon F. , Suzuki Tsutomu
Published: April 2018

The aim of the present study was to investigate the role of dopamine D3receptors in the rewarding effect and hyperlocomotion induced by a prototypical μ-opioid receptor agonist morphine using dopamine D3receptor knock-out mice. The μ-opioid receptor in the brain determined by the [tylosil-3,5-3H(N)]-[d-Ala2,N-MePhe4,Gly-ol5]enkephalin binding assay was not significantly changed by a deletion of the dopamine D3receptor gene. Furthermore, we found that no significant differences in G-protein activation by morphine in the limbic forebrain and lower midbrain were noted between the two genotypes. These results suggest that the function of the μ-opioid receptor itself was not affected by a deletion of the dopamine D3receptor gene. To ascertain the morphine-induced rewarding effect in both genotypes, the conditioned place preference paradigm was performed. Deletion of the dopamine D3receptor gene resulted in a remarkable enhancement of the morphine-induced rewarding effect. Furthermore, knock-out mice with deletions of the dopamine D3receptor revealed a dramatic potentiation of morphine-induced hyperlocomotion. Under these conditions, a loss of the dopamine D3receptor gene had no effect on the basal levels of dopamine and the increased dopamine turnover by morphine in the limbic forebrain. These findings provide further evidence that dopamine D3receptor contributes to the postsynaptically negative modulation of the mesolimbic dopaminergic pathway that is associated with the rewarding effect and hyperlocomotion through the stimulation of μ-opioid receptors induced by morphine in the mouse.
Selective Impairment of Hippocampal Gamma Oscillations in Connexin-36 Knock-Out MouseIn Vivo
Authors: Buhl Derek L. , Harris Kenneth D. , Hormuzdi Sheriar G. , Monyer Hanna , Buzsáki György
Published: April 2018

The physiological roles of neuronal gap junctions in the intact brain are not known. The recent generation of the connexin-36 knock-out (Cx36 KO) mouse has offered a unique opportunity to examine this problem. Recentin vitrorecordings in Cx36 KO mice suggested that Cx36 gap junction contributes to various oscillatory patterns in the theta (∼5–10 Hz) and gamma (∼30–80 Hz) frequency ranges and affects certain aspects of high-frequency (>100 Hz) patterns. However, the relevance of these pharmacologically induced patterns to the intact brain is not known. We recorded field potentials and unit activity in the CA1 stratum pyramidale of the hippocampus in the behaving wild-type (WT) and Cx36 KO mice. Fast-field “ripple” oscillations (140–200 Hz) were present in both WT and KO mice and did not differ significantly in power, intraepisode frequency, or probability of occurrence. Thus, fast-field oscillations either may not require electrical synapses or may be mediated by a hitherto unknown class of gap junctions. Theta oscillations, recorded during either wheel running or rapid eye movement sleep, were not different either. However, the power in the gamma frequency band and the magnitude of theta-phase modulation of gamma power were significantly decreased in KO mice compared with WT controls during wheel running. This suggests that Cx36 interneuronal gap junctions selectively contribute to gamma oscillations.
Tumor Necrosis Factor-α Induces Mechanical Allodynia after Spinal Nerve Ligation by Activation of p38 MAPK in Primary Sensory Neurons
Authors: Schäfers Maria , Svensson Camilla I. , Sommer Claudia , Sorkin Linda S.
Published: April 2018

Tumor necrosis factor-α (TNF) is implicated in the initiation of neuropathic pain.In vitro, TNF activates p38 mitogen-activated kinase. Accordingly, we investigated whether TNF activates the p38 cascadein vivoto trigger pain behavior after spinal nerve ligation (SNL). Treatment starting 2 d before SNL with the TNF antagonist etanercept (1 mg, i.p., every third day) attenuated mechanical allodynia. Treatment starting 1 or 7 d after SNL was ineffective. Similarly, intrathecal infusion of a p38 inhibitor (SB203580, 4 mg/d) was effective only if it was started before but not 7 d after SNL. For both treatments, the cessation of therapy resulted in increased allodynia. In separate experiments using Western blots and immunohistochemistry, ipsilateral lumbar spinal cord and L5 and L6 DRG were analyzed for total and phosphorylated p38 after SNL alone or SNL combined with etanercept pretreatment. In DRG, activated p38 was transiently elevated 5 hr after SNL and returned to baseline by 1 d after SNL. Phosphorylated p38 was localized in small TNF-positive DRG neurons. In spinal cord, p38 was activated between 5 hr and 3 d after SNL and returned to baseline within 5 d. In DRG, but not spinal cord, etanercept pretreatment blocked p38 activation. These data indicate that after SNL treatment, phosphorylated p38 levels in spinal cord and DRG are transiently elevated. In DRG, p38 activation is blocked by systemic TNF inhibition. Parallel inhibition of p38 activation and allodynia may represent a clinically relevant therapeutic window. These data suggest a sequential role for TNF and p38 in the induction of neuropathic pain.
Somatic and Dendritic Small-Conductance Calcium-Activated Potassium Channels Regulate the Output of Cerebellar Purkinje Neurons
Authors: Womack Mary D. , Khodakhah Kamran
Published: April 2018

Cerebellar Purkinje neurons provide the sole output of the cerebellar cortex and play a crucial role in motor coordination and maintenance of balance. They are spontaneously active, and it is thought that they encode timing signals in the rate and pattern of their activity. An understanding of factors that control their excitability is important for delineating their computational role in the cerebellum. We evaluated the role of small-conductance calcium-activated potassium (SK) channels in the regulation of activity of mouse and rat Purkinje neurons. We find that somatic SK channels effectively limit the maximum firing rate of Purkinje neurons; when SK channels are blocked by the specific antagonists apamin or scyllatoxin, cells fire spontaneously at rates as high as 500 spikes per second. Dendritic SK channels, however, control primarily the extent to which dendrites contribute to the firing rate of Purkinje cells. Given their presence in the dendrites, it is likely that SK channels in the proximal dendrites govern the efficacy of dendrosomatic electrical coupling. When studied under physiological conditions, it is found that SK channels play the same role in controlling the excitability of adult Purkinje neurons as they do in young cells.
Dopamine D1-Class Receptors Selectively Modulate a Slowly Inactivating Potassium Current in Rat Medial Prefrontal Cortex Pyramidal Neurons
Authors: Dong Yan , White Francis J.
Published: April 2018

The dopamine (DA) innervation of medial prefrontal cortex (mPFC) regulates cognitive activity in a complex manner. Alterations of DA function, particularly via the DA D1 receptor class (D1R), are implicated in both schizophrenia and drug addiction, yet the precise roles of DA in modulating mPFC excitability remain unclear. We focused on DA modulation of voltage-gated K+current (VGKC) in acutely dissociated rat mPFC pyramidal neurons. We defined three components of the whole-cell VGKC according to biophysical and pharmacological properties. The A-type current (IA), with rapid activation and inactivation kinetics, was completely inactivated by prolonged holding of the membrane potential at −40 mV and was sensitive to the K+channel blocker 4-aminopyridine (4-AP) but not tetraethylammonium (TEA) or dendrotoxin (DTX). The slowly inactivating K+current (ID), with rapid activation but relatively slow inactivation, was the major contributor to VGKC and was completely inactivated at −40 mV and sensitive to TEA and DTX but less so to 4-AP. The very slowly inactivating K+current (IK) was elicited by command steps to more depolarized potentials from a prolonged holding potential of −40 mV and was sensitive to all three blockers. Stimulation of DA D2 receptors failed to alter any component of whole-cell VGKC. Stimulation of DA D1Rs selectively suppressedID, an effect mimicked by the adenylyl cyclase activator forskolin, the active cAMP analog Sp-cAMP, and the protein phosphatase inhibitor okadaic acid. Inhibition of protein kinase A (PKA) with either PKI or Rp-cAMP abolished D1R modulation. Thus, the DA D1R/cAMP/PKA signaling pathway mediates modulation ofIDby DA in rat mPFC pyramidal neurons.
Inhibition of Bax-Induced CytochromecRelease from Neural Cell and Brain Mitochondria by Dibucaine and Propranolol
Authors: Polster Brian M. , Basañez Gorka , Young Michael , Suzuki Motoshi , Fiskum Gary
Published: April 2018

BH3 (Bcl-2 homology 3)-only proteins of the Bcl-2 family activate Bax or Bak during apoptosis to promote the release of pro-death factors sequestered in the mitochondrial intermembrane space. Previous results demonstrated that a synthetic BH3 peptide mimics the ability of the BH3-only protein Bid to promote Bax insertion and cytochromec(cytc) release from neural cell mitochondria. However, the BH3 peptide was deficient in promoting cytcrelease from mitochondria without associated Bax, such as adult rat brain mitochondria. This study tested the hypothesis that the amphiphilic membrane-active cationic drugs dibucaine and propranolol block BH3 peptide-initiated cytcefflux by preventing the integration of Bax into the mitochondrial outer membrane. BH3 peptide-initiated release of cytcfrom GT1-7 neural cell mitochondria was inhibited by dibucaine and propranolol at concentrations of 100–300 μm. Recombinant Bax (100 nm) alone did not release cytcfrom adult rat brain mitochondria; however, when BH3 peptide or caspase-8 cleaved Bid (cBid) was added, robust cytcrelease was achieved that was inhibited completely by 200 μmdibucaine or propranolol. These drugs at similar concentrations also inhibited release of entrapped 10 kDa dextrans from protein-free liposomes treated with Bax and cBid. Contrary to the hypothesis that dibucaine and propranolol act by inhibiting the insertion of Bax into the mitochondrial outer membrane, membrane insertion of Bax was not inhibited in mitochondria or liposomes, indicating a mechanism of drug action downstream from this event. These results suggest that dibucaine and propranolol inhibit Bax-induced permeability changes through a direct interaction with the lipid membrane and present a novel target for the development of neuroprotective, antiapoptotic therapeutics.
Demonstration of Cholinergic Ganglion Cells in Rat Retina: Expression of an Alternative Splice Variant of Choline Acetyltransferase
Authors: Yasuhara Osamu , Tooyama Ikuo , Aimi Yoshinari , Bellier Jean-Pierre , Hisano Tadashi , Matsuo Akinori , Park Masami , Kimura Hiroshi
Published: April 2018

Acetylcholine acts as a neurotransmitter in the retina. Although previous physiological studies have indicated that some retinal ganglion cells may be cholinergic, several immunohistochemical studies using antibodies to choline acetyltransferase (ChAT) have stained only amacrine cells but not ganglion cells. Recently, we identified a splice variant of ChAT mRNA, lacking exons 6–9, in rat peripheral nervous system. The encoded protein was designated as ChAT of a peripheral type (pChAT), against which an antiserum was raised. In the present study, we examined expression of pChAT in rat retina, both at the protein level by immunohistochemistry using the antiserum and at the mRNA level by RT-PCR. Immunohistochemistry revealed that although no positive neurons were found in untreated intact retinas, many neurons became immunoreactive for pChAT after intravitreal injection of colchicine. Damage of the optic nerve was also effective in disclosing positive cells. Such positive neurons were shown to be ganglion cells by double labeling with a retrograde tracer that had been injected into the contralateral superior colliculus. Western blot analysis and RT-PCR revealed a corresponding band to the pChAT protein and to the amplified pChAT gene fragment, respectively, in retinal samples. In addition, ChAT activity was definitely detected in retinofugal fibers of the optic nerve. These results indicate the presence of cholinergic ganglion cells in rat retina.