bluuebunny/crossref_metadata_2025 huggingface dataset:
Involvement of p62 Nucleoporin in Angiotensin II-Induced Nuclear Translocation of STAT3 in Brain Neurons
Authors: Lu Di , Yang Hong , Raizada Mohan K.
Published: April 2018

Chronic stimulation of brain neurons by angiotensin II (Ang II) results in a increase in norepinephrine (NE) uptake. This involves stimulation of transcription of NE transporter and tyrosine hydroxylase genes and is associated with translocation of signaling molecules and transcription factors from the cytoplasmic compartment into the neuronal nucleus (Lu et al., 1996a). We report here that the phosphorylation of p62, a glycoprotein nucleoporin of the nuclear pore complex (NPC), by MAP kinase is involved in this process. Ang II caused a time-dependent translocation of signal transducers and activators of transcription (STAT3) from the cytoplasmic compartment into the nucleus. This translocation was attenuated by pretreatment with antisense oligonucleotide (AON) to MAP kinase. Ang II also stimulated phosphorylation of p62, and a maximal phosphorylation of 12-fold was observed with 100 nmAng II. This stimulation was blocked by losartan, an AT1receptor subtype-specific antagonist. The conclusion that MAP kinase is involved in Ang II-induced phosphorylation of p62 and nuclear translocation of STAT3 is supported by the following. (1) p62 phosphorylation was blocked by a peptide that competes with p62 as a MAP kinase substrate bothin vitroandin vivo; (2) AON to MAP kinase attenuated Ang II stimulation of p62 phosphorylation; and (3) in addition, it also blocked nuclear translocation of STAT3. Intracellular loading of the peptide containing MAP kinase substrate consensus of the p62 reduced Ang II stimulation of p62 phosphorylation and nuclear translocation of STAT3 in bothin vivoandin vitroexperiments. These observations suggest that Ang II-induced phosphorylation of p62 may accelerate the activity of the NPC, which would result in an increase in the nuclear transport of transcription factors and signaling molecules. This will stimulate transcriptional processes associated with Ang II regulation of NE neuromodulation.
Internalization of D1 Dopamine Receptor in Striatal NeuronsIn Vivoas Evidence of Activation by Dopamine Agonists
Authors: Dumartin Brigitte , Caillé Isabelle , Gonon Francois , Bloch Bertrand
Published: April 2018

To investigate how dopamine influences the subcellular localization of the dopamine receptors in the striatal dopaminoceptive neurons, we have used immunohistochemistry to detect D1 dopamine receptors (D1R) after modifications of the dopamine environment. In normal rats, D1R are located mostly extrasynaptically at the plasma membrane of the cell bodies, dendrites, and spines. The intrastriatal injection of the full D1R agonist SKF-82958 and the intraperitoneal injection of the same molecule or of amphetamine (which induces a massive release of dopamine in the striatum) induce modifications of the pattern of D1R immunoreactivity in the dorsal and ventral striatum. Whereas normal rats display homogenous staining of the neuropile with staining of the plasma membrane of the cell bodies, either treatment provokes the appearance of an intense immunoreactivity in the cytoplasm and the proximal dendrites. The labeling pattern is heterogeneous and more intense in the striosomes than in the matrix. Analysis of semithin sections and electron microscopy studies demonstrates a translocation of the labeling from the plasma membrane to endocytic vesicles and endosomes bearing D1R immunoreactivity in the cytoplasm of cell bodies and dendrites. Injection of D1R antagonist (SCH-23390) alone or injection of D1R antagonist, together with amphetamine or SKF-82958, do not provoke modification of the immunoreactivity, as compared with normal rat.

Our results demonstrate that,in vivo, the acute activation of dopamine receptors by direct agonists or endogenously released dopamine provokes dramatic modifications of their subcellular distribution in neurons, including internalization in the endosomal compartment in the cytoplasm. This suggests that modifications of the localization of neurotransmitter receptors, including extrasynaptic ones, may be a critical event that contributes to the postsynaptic responsein vivo.
Turnover of Amyloid β-Protein in Mouse Brain and Acute Reduction of Its Level by Phorbol Ester
Authors: Savage Mary J. , Trusko Stephen P. , Howland David S. , Pinsker Leonard R. , Mistretta Suzanne , Reaume Andrew G. , Greenberg Barry D. , Siman Robert , Scott Richard W.
Published: April 2018

Fibrillar amyloid deposits are defining pathological lesions in Alzheimer’s disease brain and are thought to mediate neuronal death. Amyloid is composed primarily of a 39–42 amino acid protein fragment of the amyloid precursor protein (APP), called amyloid β-protein (Aβ). Because deposition of fibrillar amyloidin vitrohas been shown to be highly dependent on Aβ concentration, reducing the proteolytic release of Aβ is an attractive, potentially therapeutic target. Here, the turnover rate of brain Aβ has been determined to define treatment intervals over which a change in steady-state concentration of Aβ could be measured. Mice producing elevated levels of human Aβ were used to determine approximate turnover rates for Aβ and two of its precursors, C99 and APP. Thet½for brain Aβ was between 1.0 and 2.5 hr, whereas for C99, immature, and fully glycosylated forms of APP695 the approximatet½values were 3, 3, and 7 hr, respectively. Given the rapid Aβ turnover rate, acute studies were designed using phorbol 12-myristate 13-acetate (PMA), which had been demonstrated previously to reduce Aβ secretion from cellsin vitrovia induction of protein kinase C (PKC) activity. Six hours after intracortical injection of PMA, Aβ levels were significantly reduced, as measured by both Aβ40- and Aβ42-selective ELISAs, returning to normal by 12 hr. An inactive structural analog of PMA, 4α-PMA, had no effect on brain Aβ levels. Among the secreted N-terminal APP fragments, APPβ levels were significantly reduced by PMA treatment, whereas APPα levels were unchanged, in contrast to most cell culture studies. These results indicate that Aβ is rapidly turned over under normal conditions and support the therapeutic potential of elevating PKC activity for reduction of brain Aβ.
Ectopic Overexpression of Engrailed-2 in Cerebellar Purkinje Cells Causes Restricted Cell Loss and Retarded External Germinal Layer Development at Lobule Junctions
Authors: Baader Stephan L. , Sanlioglu Salih , Berrebi Albert S. , Parker-Thornburg Jan , Oberdick John
Published: April 2018

Members of the En and Wnt gene families seem to play a key role in the early specification of the brain territory that gives rise to the cerebellum, the midhindbrain junction. To analyze the possible continuous role of the En and Wnt signaling pathway in later cerebellar patterning and function, we expressed En-2 ectopically in Purkinje cells during late embryonic and postnatal cerebellar development. As a result of this expression, the cerebellum is greatly reduced in size, and Purkinje cell numbers throughout the cerebellum are reduced by more than one-third relative to normal animals. Detailed analysis of both adult and developing cerebella reveals a pattern of selectivity to the loss of Purkinje cells and other cerebellar neurons. This is observed as a general loss of prominence of cerebellar fissures that is highlighted by a total loss of sublobular fissures. In contrast, mediolateral patterning is generally only subtly affected. That En-2 overexpression selectively affects Purkinje cells in the transition zone between lobules is evidenced by direct observation of selective Purkinje cell loss in certain fissures and by the observation that growth and migration of the external germinal layer (EGL) is selectively retarded in the deep fissures during early postnatal development. Thus, in addition to demonstrating the critical role of Purkinje cells in the generation and migration of granule cells, the heterogeneous distribution of cellular effects induced by ectopic En expression suggests a relatively late morphogenetic role for this and other segment polarity proteins, mainly oriented at lobule junctions.
Axonal Versus Dendritic Outgrowth Is Differentially Affected by Radial Glia in Discrete Layers of the Retina
Authors: Bauch Hubert , Stier Heike , Schlosshauer Burkhard
Published: April 2018

Formation of neural cell polarity defined by oriented extension of axons and dendrites is a crucial event during the development of the nervous system. Ganglion cells of the chicken retina extend axons exclusively into the inner retina, whereas their dendrites grow into the outer retina. To analyze guidance cues for specific neurite extension, novelin vitrosystems were established. Ganglion cells were purified by enzymatically facilitated detachment of the ganglion cell layer. A newly developed retrograde labeling technique and the expression analysis of the cell type-specific 2A1 antigen were used to monitor ganglion cell purification. In highly purified ganglion cells explanted onto retinal cryosections (cryoculture), axon formation was induced when the cells were positioned on the inner retina. In contrast, on outer layers of the developing retina dendritic outgrowth was prevalent. Because radial glia have been demonstrated to be instructive in neuritogenesis, distinct glial cell compartments located in inner and outer retina, respectively, were isolated for functional assays. Glial end feet were purified by a physical detachment technique. Glial somata were purified by complement mediated cytolysis of all nonglial cells. When ganglion cells were cultured on different glial compartments, axon formation occurred on end feet but not on glial somata. In striking contrast, on glial somata dendrites were formed. The data support the notion that ganglion cell polarity is affected by the retinal microenvironment, which in turn is possibly influenced by radial glia, being themselves polarized.
Cell- and Lamina-Specific Expression and Activity-Dependent Regulation of Type II Calcium/Calmodulin-Dependent Protein Kinase Isoforms in Monkey Visual Cortex
Authors: Tighilet Brahim , Hashikawa Tsutomu , Jones Edward G.
Published: April 2018

In situhybridization histochemistry and immunocytochemistry were used to study localization and activity-dependent regulation of α, β, γ, and δ isoforms of type II calcium/calmodulin-dependent protein kinase (CaMKII) and their mRNAs in areas 17 and 18 of normal and monocularly deprived adult macaques. CaMKII-α is expressed overall at levels three to four times higher than that of CaMKII-β and at least 15 times higher than that of CaMKII-γ and -δ. All isoforms are expressed primarily in pyramidal cells of both areas, especially those of layers II–III, IVA (in area 17), and VI, but are also expressed in nonpyramidal, non-GABAergic cells of layer IV of both areas and in interstitial neurons of the white matter. CaMKII-α and -β are colocalized, suggesting the formation of heteromers. There was no evidence of expression in neuroglial cells. Each isoform has a unique pattern of laminar and sublaminar distribution, but cortical layers or sublayers enriched for one isoform do not correlate with layers receiving inputs only from isoform-specific layers of the lateral geniculate nucleus. CaMKII-α and -β mRNA and protein levels in layer IVC of area 17 are subject to activity-dependent regulation, with brief periods of monocular deprivation caused by intraocular injections of tetrodotoxin leading to a 30% increase in CaMKII-α mRNA and a comparable decrease in CaMKII-β mRNA in deprived ocular dominance columns, especially of layer IVCβ. Expression in other layers and expression of CaMKII-γ and δ were unaffected. Changes occurring in layer IVC may influence the formation of heteromers and protect supragranular layers from CaMKII-dependent plasticity in the adult.
Mechanisms of Cortical Reorganization in Lower-Limb Amputees
Authors: Chen Robert , Corwell Brian , Yaseen Zaneb , Hallett Mark , Cohen Leonardo G.
Published: April 2018

The human motor system undergoes reorganization after amputation, but the site of motor reorganization and the mechanisms involved are unknown. We studied the site and mechanisms of motor reorganization in 16 subjects with traumatic lower-limb amputation. Stimulation at different levels in the CNS was used to determine the site of reorganization. The mechanisms involved were evaluated by measuring the thresholds for transcranial magnetic stimulation (TMS) and by testing intracortical inhibition and facilitation. With TMS, the threshold for muscle activation on the amputated side was lower than that of the intact side, but with transcranial electrical stimulation there was no difference in motor threshold between the two sides. TMS at the maximal output of the stimulator activated a higher percentage of the motor neuron pool (%MNP) on the amputated side than on the intact side. The %MNP activated by spinal electrical stimulation was similar on the two sides. Paired TMS study showed significantly less intracortical inhibition on the amputated side. Our findings suggest that motor reorganization after lower-limb amputation occurs predominately at the cortical level. The mechanisms involved are likely to include reduction of GABAergic inhibition.
Downregulation of Transient K+Channels in Dendrites of Hippocampal CA1 Pyramidal Neurons by Activation of PKA and PKC
Authors: Hoffman Dax A. , Johnston Daniel
Published: April 2018

We have reported recently a high density of transient A-type K+channels located in the distal dendrites of CA1 hippocampal pyramidal neurons and shown that these channels shape EPSPs, limit the back-propagation of action potentials, and prevent dendritic action potential initiation (Hoffman et al., 1997). Because of the importance of these channels in dendritic signal propagation, their modulation by protein kinases would be of significant interest. We investigated the effects of activators of cAMP-dependent protein kinase (PKA) and the Ca2+-dependent phospholipid-sensitive protein kinase (PKC) on K+channels in cell-attached patches from the distal dendrites of hippocampal CA1 pyramidal neurons. Inclusion of the membrane-permeant PKA activators 8-bromo-cAMP (8-br-cAMP) or forskolin in the dendritic patch pipette resulted in a depolarizing shift in the activation curve for the transient channels of ∼15 mV. Activation of PKC by either of two phorbol esters also resulted in a 15 mV depolarizing shift of the activation curve. Neither PKA nor PKC activation affected the sustained or slowly inactivating component of the total outward current. This downregulation of transient K+channels in the distal dendrites may be responsible for some of the frequently reported increases in cell excitability found after PKA and PKC activation. In support of this hypothesis, we found that activation of either PKA or PKC significantly increased the amplitude of back-propagating action potentials in distal dendrites.
Temporal and Spectral Sensitivity of Complex Auditory Neurons in the Nucleus HVc of Male Zebra Finches
Authors: Theunissen Frédéric E. , Doupe Allison J.
Published: April 2018

Complex vocalizations, such as human speech and birdsong, are characterized by their elaborate spectral and temporal structure. Because auditory neurons of the zebra finch forebrain nucleus HVc respond extremely selectively to a particular complex sound, the bird’s own song (BOS), we analyzed the spectral and temporal requirements of these neurons by measuring their responses to systematically degraded versions of the BOS. These synthetic songs were based exclusively on the set of amplitude envelopes obtained from a decomposition of the original sound into frequency bands and preserved the acoustical structure present in the original song with varying degrees of spectral versus temporal resolution, which depended on the width of the frequency bands. Although both excessive temporal or spectral degradation eliminated responses, HVc neurons responded well to degraded synthetic songs with time–frequency resolutions of ∼5 msec or 200 Hz. By comparing this neuronal time–frequency tuning with the time–frequency scales that best represented the acoustical structure in zebra finch song, we concluded that HVc neurons are more sensitive to temporal than to spectral cues. Furthermore, neuronal responses to synthetic songs were indistinguishable from those to the original BOS only when the amplitude envelopes of these songs were represented with 98% accuracy. That level of precision was equivalent to preserving the relative time-varying phase across frequency bands with resolutions finer than 2 msec. Spectral and temporal information are well known to be extracted by the peripheral auditory system, but this study demonstrates how precisely these cues must be preserved for the full response of high-level auditory neurons sensitive to learned vocalizations.
Retrograde Amnesia for Facts and Events: Findings from Four New Cases
Authors: Reed Jonathan M. , Squire Larry R.
Published: April 2018

Two patients with presumed hippocampal formation lesions and two patients with more extensive temporal lobe damage, all of whom became amnesic in a known year, were given tests of anterograde and retrograde memory function. The two patients with hippocampal formation lesions had moderately severe anterograde amnesia and limited retrograde amnesia for facts and events that affected, at most, the decade preceding the onset of amnesia. Content analysis could not distinguish the autobiographical recollections of the patients from the recollections of control subjects. The two patients with more extensive temporal lobe damage had severe anterograde amnesia and extensive retrograde memory loss for both facts and events. The results suggest that whether retrograde amnesia is temporally limited or very extensive depends on whether the damage is restricted to the hippocampal formation or also involves additional temporal cortex.
Modulation of Neuronal Activity by Glial Cells in the Retina
Authors: Newman Eric A. , Zahs Kathleen R.
Published: April 2018

Glial–neuronal communication was studied by monitoring the effect of intercellular glial Ca2+waves on the electrical activity of neighboring neurons in the eyecup preparation of the rat. Calcium waves in astrocytes and Müller cells were initiated with a mechanical stimulus applied to the retinal surface. Changes in the light-evoked spike activity of neurons within the ganglion cell layer occurred when, and only when, these Ca2+waves reached the neurons. Inhibition of activity was observed in 25 of 53 neurons (mean decrease in spike frequency, 28 ± 2%). Excitation occurred in another five neurons (mean increase, 27 ± 5%). Larger amplitude Ca2+waves were associated with greater modulation of neuronal activity. Thapsigargin, which reduced the amplitude of the glial Ca2+increases, also reduced the magnitude of neuronal modulation. Bicuculline and strychnine, inhibitory neurotransmitter antagonists, as well as 6-Nitro-7-sulphamoylbenzo[f]quinoxaline-2,3-dione (NBQX) andd(−)-2-amino-7-phosphonoheptanoic acid (D-AP7), glutamate antagonists, reduced the inhibition of neuronal activity associated with glial Ca2+waves, suggesting that inhibition is mediated by inhibitory interneurons stimulated by glutamate release from glial cells. The results suggest that glial cells are capable of modulating the electrical activity of neurons within the retina and thus, may directly participate in information processing in the CNS.
Prevention of PC12 Cell Death byN-Acetylcysteine Requires Activation of the Ras Pathway
Authors: Yan Chao Yun Irene , Greene Lloyd A.
Published: April 2018

We have shown thatN-acetylcysteine (NAC) promotes survival of sympathetic neurons and pheochromocytoma (PC12) cells in the absence of trophic factors. This action of NAC was not related to its antioxidant properties or ability to increase intracellular glutathione levels but was instead dependent on ongoing transcription and seemed attributable to the action of NAC as a reducing agent. Here, we investigate the mechanism by which NAC promotes neuronal survival. We show that NAC activates the Ras-extracellular signal-regulated kinase (ERK) pathway in PC12 cells. Ras activation by NAC seems necessary for survival in that it is unable to sustain serum-deprived PC12 MM17-26 cells constitutively expressing a dominant-negative form of Ras. Promotion of PC12 cell survival by NAC is totally blocked by PD98059, an inhibitor of the ERK-activating MAP kinase/ERK kinase, suggesting a required role for ERK activation in the NAC mechanism. In contrast, LY294002 and wortmannin, inhibitors of phosphatidylinositol 3-kinase (PI3K) that partially block NGF-promoted PC12 cell survival, have no effect on prevention of death by NAC. We hypothesized previously that the ability of NAC to promote survival correlates with its antiproliferative properties. However, although NAC does not protect PC12 MM17-26 cells from loss of trophic support, it does inhibit their capacity to synthesize DNA. Thus, the antiproliferative effect of NAC does not require Ras activation, and inhibition of DNA synthesis is insufficient to mediate NAC-promoted survival. These findings highlight the role of Ras-ERK activation in the mechanism by which NAC prevents neuronal death after loss of trophic support.
Non-Cell-Autonomous Photoreceptor Degeneration inrdsMutant Mice Mosaic for Expression of a Rescue Transgene
Authors: Kedzierski Wojciech , Bok Dean , Travis Gabriel H.
Published: April 2018

The inherited retinal dystrophies represent a large and heterogenous group of hereditary neurodegenerations, for many of which, the molecular defect has been defined. However, the mechanism of cell death has not been determined for any form of retinal degeneration. Theretinal degeneration slow(rds−/−) mutation of mice is associated with nondevelopment of photoreceptor outer segments and gradual death of photoreceptor cell bodies, attributed to the absence of the outer segment protein rds/peripherin. Here, we examined the effects of a transgene encoding normal rds/peripherin that had integrated into the X-chromosome in male and femalerds−/− mutant retinas. In 2-month-old transgenic males and homozygous-transgenic females onrds−/−, we observed virtually complete rescue of both the outer segment nondevelopment and photoreceptor degeneration. In contrast, hemizygous-transgenicrds−/− female littermates showed patchy distributions of the transgene mRNA, byin situhybridization analysis, and of photoreceptor cells that contain outer segments. This pattern is consistent with random inactivation of the X-chromosome and mosaic expression of the transgene. Surprisingly, we observed significant photoreceptor cell loss in both transgene-expressing and nonexpressing patches in hemizygous female retinas. These observations were supported by nuclease protection analysis, which showed notably lower than predicted levels of transgene mRNA in retinas from hemizygous females compared with male and homozygous female littermates. This phenotype suggests an important component of non-cell-autonomous photoreceptor death inrds−/− mutant mice. These results have significance to both the etiology and potential treatment of human inherited retinal degenerations.
The Development of Local, Layer-Specific Visual Cortical Axons in the Absence of Extrinsic Influences and Intrinsic Activity
Authors: Dantzker Jami L. , Callaway Edward M.
Published: April 2018

The laminar specificity of vertical connections in the primary visual cortex (area 17) develops precisely from the outset, leading to the hypothesis that layer-specific axonal targeting is attributable to molecular cues intrinsic to the cortex (Lund et al., 1977; Katz and Callaway, 1992). However, alternative factors that could influence axonal development have not been investigated. This study examines the roles of intrinsic cortical activity and extrinsic influences that could arise from earlier-formed connections with outside cortical and subcortical areas. Organotypic slice cultures were prepared from ferret area 17 before the formation of local axonal connections and were incubated for 5–7 d to allow initial, local axonal arbors to form in the absence of extrinsic influences. Additionally, some slices were cultured in the presence of the Na+channel blocker tetrodotoxin to block spontaneous action potentials within the slice. Individual neurons were labeled intracellularly with biocytin, and their patterns of local axonal arborizations were reconstructed. This study focuses on the development of layer 6 pyramidal neurons, the axons of whichin vivobypass an incorrect target, layer 5, before specifically arborizing in their local target, layer 4. We found that axonal arbors developingin vitropreferentially arborized in layer 4 versus layer 5. However, inhibition of spontaneous activity within the cortical slice decreased this specificity, resulting in similar numbers of axonal branches in layers 4 and 5. Thus, although cortical axons do not require influences from outside areas, intrinsic spontaneous activity is required for specific axonal arborization in correct laminar targets.
Ca2+Channel β3Subunit Enhances Voltage-Dependent Relief of G-Protein Inhibition Induced by Muscarinic Receptor Activation and Gβγ
Authors: Roche John P. , Treistman Steven N.
Published: April 2018

The Ca2+channel β subunit has been shown to reduce the magnitude of G-protein inhibition of Ca2+channels. However, neither the specificity of this action to different forms of G-protein inhibition nor the mechanism underlying this reduction in response is known. We have reported previously that coexpression of the Ca2+channel β3subunit causes M2muscarinic receptor-mediated inhibition of α1BCa2+currents to become more voltage-dependent. We report here that the β3subunit increases the rate of relief of inhibition produced by a depolarizing prepulse and also shifts the voltage dependency of this relief to more hyperpolarized voltages; these effects are likely to be responsible for the reduction of inhibitory response of α1Bchannels to G-protein-mediated inhibition seen after coexpression of the Ca2+channel β3subunit. Additionally, the β3subunit alters the rate and voltage dependency of relief of the inhibition produced by coexpressed Gβ1γ1, in a manner similar to the changes it produces in relief of M2receptor-induced inhibition. We conclude that the Ca2+channel β3subunit reduces the magnitude of G-protein inhibition of α1BCa2+channels by enhancing the rate of dissociation of the G-protein βγ subunit from the Ca2+channel α1Bsubunit.
Dopamine D1-Like Receptor Activation Excites Rat Striatal Large Aspiny NeuronsIn Vitro
Authors: Aosaki Toshihiko , Kiuchi Kazutoshi , Kawaguchi Yasuo
Published: April 2018

The aim of this study was to elucidate electrophysiologically the actions of dopamine and SKF38393, a D1-like dopamine receptor agonist, on the membrane excitability of striatal large aspiny neurons (cholinergic interneurons). Whole-cell and perforated patch-clamp recordings were made of striatal cholinergic neurons in rat brain slice preparations. Bath application of dopamine (1–100 μm) evoked a depolarization/inward current with an increase, a decrease, or no change in membrane conductance in a dose-dependent manner. This effect was antagonized by SCH23390, a D1-like dopamine receptor antagonist. The current–voltage relationships of the dopamine-induced current determined in 23 cells suggested two conductances. In 10 cells the current reversed at −94 mV, approximately equal to the K+equilibrium potential (EK); in three cells theI–Vcurves remained parallel, whereas in 10 cells the current reversed at −42 mV, which suggested an involvement of a cation permeable channel. Change in external K+concentration shifted the reversal potential as expected forEkin low Na+solution. The current observed in 2 mmBa2+-containing solution reversed at −28 mV. These actions of dopamine were mimicked by application of SKF38393 (1–50 μm) or forskolin (10 μm), an adenylyl cyclase activator, and were blocked by SCH23390 (10 μm) or SQ22536 (300 μm), an inhibitor of adenylyl cyclase. These data indicate, first, that dopamine depolarizes the striatal large aspiny neurons by a D1-mediated suppression of resting K+conductance and an opening of a nonselective cation channel and, second, that both mechanisms are mediated by an adenylyl cyclase-dependent pathway.
The Sodium ChannelScn8aIs the Major Contributor to the Postnatal Developmental Increase of Sodium Current Density in Spinal Motoneurons
Authors: Garcı́a Kelly D. , Sprunger Leslie K. , Meisler Miriam H. , Beam Kurt G.
Published: April 2018

Sodium currents were recorded from motoneurons that were isolated from mice at postnatal days 0–8 (P0–P8) and maintained in culture for 12–24 hr. Motoneurons from normal mice exhibited a more than threefold increase in peak sodium current density from P0 to P8. For mice lacking a functionalScn8asodium channel gene, motoneuronal sodium current density was comparable at P0 to that of normal mice but failed to increase from P0 to P8. The absence ofScn8asodium channels is associated with the phenotype “motor end plate disease,” which is characterized by a progressive neuromuscular failure and is fatal by 3–4 postnatal weeks. Thus, it appears that the development and function of mature motoneurons depends on the postnatal induction ofScn8aexpression.
Vasoactive Intestinal Peptide Enhances Its Own Expression in Sympathetic Neurons after Injury
Authors: Mohney Robert P. , Zigmond Richard E.
Published: April 2018

Neurons in the adult rat superior cervical sympathetic ganglion (SCG) dramatically increase their content of vasoactive intestinal peptide (VIP) and its mRNA after axotomyin vivoand after explantation. Because the VIP gene contains a functional cAMP response element, the effects of cAMP-elevating agents on VIP expression were examined. VIP, forskolin, or isoproterenol increased cAMP accumulation in explanted ganglia. Secretin, a peptide chemically related to VIP, or forskolin increased VIP levels above those seen in ganglia cultured in control medium, whereas treatment with VIP or secretin increased the level of peptide histidine isoleucine (PHI), a peptide coded for by the same mRNA that encodes VIP. VIP or forskolin also increased VIP–PHI mRNA. In contrast, isoproterenol did not alter levels of VIP, PHI, or VIP–PHI mRNA. Although VIP or forskolin increased cAMP levels in both dissociated neurons and in non-neuronal cells, isoproterenol significantly stimulated cAMP accumulation only in the latter. VIP6–28was an effective antagonist of the actions of exogenous VIP on cAMP and VIP–PHI mRNA in neuron-enriched cultures. When adult SCG explants were cultured in defined medium, endogenous VIP immunoreactivity was released. When VIP6–28was added to such cultures, it significantly inhibited the increase in VIP–PHI mRNA that normally occurs. These data indicate that VIP, or a closely related molecule, produced by adult neurons after injury can enhance the expression of VIP. Such a mechanism may prolong the period during which VIP is elevated after axonal damage. The possibility is also discussed that, because VIP is present in preganglionic neurons in normal animals, its release during periods of increased sympathetic nerve activity could alter VIP expression in the SCG.
Tlx-1andTlx-3Homeobox Gene Expression in Cranial Sensory Ganglia and Hindbrain of the Chick Embryo: Markers of Patterned Connectivity
Authors: Logan Cairine , Wingate Richard J. T. , McKay Ian J. , Lumsden Andrew
Published: April 2018

Recent evidence suggests that in vertebrates the formation of distinct neuronal cell types is controlled by specific families of homeodomain transcription factors. Furthermore, the expression domains of a number of these genes correlates with functionally integrated neuronal populations. We have isolated two members of the divergent T-cell leukemia translocation (HOX11/Tlx) homeobox gene family from chick,Tlx-1andTlx-3,and show that they are expressed in differentiating neurons of both the peripheral and central nervous systems. In the peripheral nervous system,Tlx-1andTlx-3are expressed in overlapping domains within the placodally derived components of a number of cranial sensory ganglia.Tlx-3, unlikeTlx-1, is also expressed in neural crest-derived dorsal root and sympathetic ganglia. In the CNS, both genes are expressed in longitudinal columns of neurons at specific dorsoventral levels of the hindbrain. Each column has distinct anterior and/or posterior limits that respect inter-rhombomeric boundaries.Tlx-3is also expressed in D2 and D3 neurons of the spinal cord.Tlx-1andTlx-3expression patterns within the peripheral and central nervous systems suggest that Tlx proteins may be involved not only in the differentiation and/or survival of specific neuronal populations but also in the establishment of neuronal circuitry. Furthermore, by analogy with the LIM genes, Tlx family members potentially define sensory columns early within the developing hindbrain in a combinatorial manner.
Differential Regulation of Synaptic Vesicle Protein Genes by Target and Synaptic Activity
Authors: Plunkett Jeffery A. , Baccus Stephen A. , Bixby John L.
Published: April 2018

Differentiation of presynaptic nerve terminals involves changes in gene expression; these may be regulated by synaptic transmission and/or by contact with the target muscle. To gain insight into the control of presynaptic differentiation, we examined the regulation by target and synaptic activity of synaptic vesicle protein (SVP) genes in the chick ciliary ganglion (CG). In the CG, two SVP genes, synaptotagmin I (syt I) and synaptophysin II (syp II), are coordinately upregulated at the time of target contact. To test the hypothesis that this upregulation is induced by target contact, we examined mRNA levels of syt I and syp II in CGs from embryos in which one eye had been removed before axon outgrowth. As expected, target removal prevented the normal upregulation of syt I mRNA in the deprived ganglion. In contrast, and unexpectedly, syp II mRNA upregulation was not affected. The target dependence of syt I upregulation was not attributable to nerve–muscle transmission, because blockade of this transmission had no effect on SVP mRNA levels. Surprisingly, blockade of synapses onto CG neurons from the brain also did not affect syt I mRNA levels but increased levels of syp II mRNA. We conclude that contact with target induces upregulation of syt I mRNA, which is the case for spinal motor neurons. However, the normal upregulation of syp II mRNA is not controlled by the same signal(s). Instead, our results suggest that these two SVP genes are differentially regulated, both by target contact and by blockade of synaptic transmission.
The “Neostriatum” Develops as Part of the Lateral Pallium in Birds
Authors: Striedter Georg F. , Marchant T. Alejandro , Beydler Sarah
Published: April 2018

Telencephalic organization in birds is so unusual that many homologies between avian and mammalian telencephalic areas remain controversial. Particularly contested is the avian “neostriatum,” which has historically been homologized to either mammalian striatum, lateral neocortex, or endopiriform claustrum. Because homologies between these adult structures have been so difficult to resolve, we have begun to examine how telencephalic development diverges between birds and other vertebrates. To this end, biotinylated dextran was injected into the lateral telencephalon of chick embryos at 3 d of incubation, and the distribution of labeled cells was examined up to 14 d later. The data show that a definite boundary to cellular migration develops just ventral to the neostriatum between 5 and 8 d of incubation. Labeled polyclones within the neostriatum stretch from the ventricular zone to the brain surface and exhibit an increasingly rostrocaudal orientation as development proceeds. Individual polyclones contribute cells to several of the distinct auditory, visual, somatosensory, and olfactory regions within the neostriatum. A comparative analysis suggests that the avian neostriatum develops from a precursor region that in other vertebrates gives rise to olfactory cortex and, when present, to other components of the piriform lobe, such as the endopiriform claustrum and basolateral amygdala. Conclusions about lateral pallial homologies between birds and mammals remain uncertain, however, primarily because so little is known about the development of the lateral pallium in mammals. This lacuna might be filled by applying to mammals the novel fate-mapping method described in the present paper.
Temperature-Sensitive Neuromuscular Transmission in Kv1.1 Null Mice: Role of Potassium Channels under the Myelin Sheath in Young Nerves
Authors: Zhou Lei , Zhang Chuan-Li , Messing Albee , Chiu Shing Yan
Published: April 2018

In mammalian myelinated nerves, the internodal axon that is normally concealed by the myelin sheath expresses a rich repertoire of K channel subtypes thought to be important in modulating action potential propagation. The function of myelin-covered K channels at transition zones, however, has remained unexplored. Here we show that deleting the voltage-sensitive potassium channel Kv1.1 from mice confers a marked temperature-sensitivity to neuromuscular transmission in postnatal day 14 (P14)–P21 mice. Using immunofluorescence and electrophysiology, we examined contributions of four regions of the peripheral nervous system to the mutant phenotype: the nerve trunk, the myelinated segment preceding the terminal, the presynaptic terminal membrane itself, and the muscle. We conclude that the temperature-sensitive neuromuscular transmission is accounted for solely by a deficiency in Kv1.1 normally concealed in the myelinated segments just preceding the terminal. This paper demonstrates that under certain situations of physiological stress, the functional role of myelin-covered K channels is dramatically enhanced as the transition zone at the neuromuscular junction is approached.
Cyclic AMP Elevation Is Sufficient to Promote the Survival of Spinal Motor NeuronsIn Vitro
Authors: Hanson Martin G. , Shen Shiliang , Wiemelt Anthony P. , McMorris F. Arthur , Barres Ben A.
Published: April 2018

The short-term survival of highly purified embryonic spinal motor neurons (SMNs) in culture can be promoted by many peptide trophic factors, including brain-derived neurotrophic factor (BDNF), ciliary neurotrophic factor (CNTF), fibroblast growth factor (FGF), glial-derived neurotrophic factor (GDNF), and hepatocyte growth factor (HGF). We have asked whether these peptides are sufficient to promote the long-term survival of purified E15 SMNs. Contrary to previous reports, we find that when SMNs are cultured in serum-free medium containing a single peptide trophic factor only approximately one-third of the cells survive for 3 d in culture. When multiple factors are combined, additive effects on survival are observed transiently, but by 7 d of culture the majority of SMNs has died. Surprisingly, when cAMP levels are elevated, the majority of SMNs extend processes and survive for 1 week in culture in the absence of peptide trophic factors, even in low-density cultures. A combination of five peptide trophic factors, together with cAMP elevation, promotes the long-term survival of most of the SMNs in serum-free culture for 3 weeks. These findings provide useful culture conditions for studying the properties of SMNs and have implications for the treatment of motor neuron diseases.
Parallel Projection of Amplitude and Phase Information from the Hindbrain to the Midbrain of the African Electric FishGymnarchus niloticus
Authors: Kawasaki Masashi , Guo Yuan-Xing
Published: April 2018

Two distinct sensory cues in electrosensory signals, amplitude modulation and differential phase modulation, are essential for an African wave-type electric fish,Gymnarchus, to perform the jamming avoidance responses. Individual neurons in the first brain station for central processing, the electrosensory lateral line lobe (ELL), were investigated by thein vivowhole-cell recording and labeling technique for their physiological responses, location, morphology, and projection areas.

Neurons in the dorsal zone of the ELL responded selectively to amplitude modulation. Neurons in the outer cell layer of the medial zone were categorized physiologically into two groups: amplitude-sensitive and differential phase-sensitive. All but one neuron in the inner cell layer of the medial zone responded exclusively to differential phase modulation. All neurons recorded and labeled in the ELL had pyramidal morphology with large and extensive apical dendrites and less extensive basal dendrites. They were found to project to two midbrain nuclei: the nucleus praeeminentialis and the torus semicircularis. Amplitude-sensitive neurons in the dorsal zone projected exclusively to the lateral posterior subdivision, the torus semicircularis. Neurons in the medial zone projected to the medial dorsal and lateral anterior subdivisions of the torus semicircularis.

Although some neurons in the ELL responded to both amplitude and differential phase modulation, they did not differentiate between temporal patterns of the two cues that encode necessary information for the jamming avoidance response. Overlapping projection of amplitude and differential phase-sensitive neurons to the torus semicircularis suggests integration of the two sensory cues in this nucleus.
Targeting of IgMκ Antibodies to Oligodendrocytes Promotes CNS Remyelination
Authors: Asakura Kunihiko , Miller David J. , Pease Larry R. , Rodriguez Moses
Published: April 2018

We previously identified the remyelinating activity of a natural IgMκ oligodendrocyte-reactive autoantibody (SCH94.03), using a virus-induced murine model of multiple sclerosis. We now describe a second mouse IgMκ monoclonal antibody (mAb) (SCH79.08) raised against normal mouse spinal cord homogenate, which reacts with myelin basic protein and also promotes remyelination. Because these two mAbs recognize different oligodendrocyte antigens, several previously identified oligodendrocyte-reactive IgMκ mAbs (O1, O4, A2B5, and HNK-1), each with distinct antigen specificities, were evaluated and found to promote remyelination. In contrast, IgMκ mAbs that did not bind to oligodendrocytes showed no remyelination. One of these, CH12 IgMκ mAb, which shares variable region cDNA sequences with SCH94.03 except for amino acid differences in the complementarity-determining region 3 in both heavy and light chains, did not bind to oligodendrocytes and did not promote remyelination. The fact that multiple oligodendrocyte-reactive antibodies with distinct antigen reactivities induce remyelination argues against direct activation by a unique cell surface receptor. These findings are most consistent with the hypothesis that the binding of mAbs to oligodendrocytes in the lesions induces myelin repair via indirect immune effector mechanisms initiated by the μ-chain. Importantly, these studies indicate that oligodendrocyte-reactive natural autoantibodies may provide a powerful and novel therapeutic means to induce remyelination in multiple sclerosis patients.
Melatonin Entrains the Restored Circadian Activity Rhythms of Syrian Hamsters Bearing Fetal Suprachiasmatic Nucleus Grafts
Authors: Grosse Julia , Davis Fred C.
Published: April 2018

A circadian pacemaker consists of at least three essential features: the ability to generate circadian oscillations, an output signal, and the ability to be entrained by external signals. In rodents, ablation of the suprachiasmatic nucleus (SCN) results in the loss of circadian rhythms in activity. Rhythmicity can be restored by transplanting fetal SCN into the brain of the lesioned animal, demonstrating the first two of the essential pacemaker features within the grafts. External signals, such as the light/dark cycle, have not, however, been shown to entrain the restored rhythms. Melatonin injections are an effective entraining stimulus in fetal and neonatal Syrian hamsters of the same developmental ages used to provide donor tissue for transplantation. Therefore, melatonin was used to test the hypothesis that SCN grafts contain an entrainable pacemaker. Daily injections of melatonin were given to SCN-lesioned hosts beginning on the day after transplantation of fetal SCN. Two groups that received melatonin at different times of day 12 hr apart each showed significantly clustered phases but with average phases that differed by 8.67 hr. Thus melatonin was able to entrain the restored circadian activity rhythms. In contrast to these initial injections, injections given 6 weeks after transplantation were unable to entrain or phase shift the rhythms. The results demonstrate that SCN grafts contain an entrainable circadian pacemaker. In addition, the results also indicate that the fetal SCN is directly sensitive to melatonin and, as with intact hamsters, sensitivity to melatonin is lost during SCN development.
Ascending Projections of Simple and Complex Cells in Layer 6 of the Cat Striate Cortex
Authors: Hirsch Judith A. , Gallagher Christine A. , Alonso José-Manuel , Martinez Luis M.
Published: April 2018

Receptive field properties vary systematically across the different layers of the cat striate cortex. Understanding how these functional differences emerge requires a precise description of the interlaminar connections and the quality of information that they transmit. This study examines the contribution of the two physiological types of neuron in layer 6, simple and complex, to the cortical microcircuit. The approach was to make whole-cell recordings with dye-filled electrodesin vivoto correlate visual response property with intracortical projection pattern. The two simple cells we stained projected to layer 4, as previously reported (Gilbert and Wiesel, 1979;Martin and Whitteridge, 1984). Six of the eight complex cells that we labeled projected to the superficial layers, a pathway not previously described in the cat. The remaining two cells targeted the infragranular layers. Layer 4 is dominated by simple cells, whereas layers 5 and 2+3 are mainly composed of complex cells (Hubel and Wiesel, 1962; Gilbert, 1977). Hence, our results indicate that the ascending projections of simple cells in layer 6 target other simple cells. In parallel, the ascending projections of a population of complex cells in layer 6 favor other complex cells. Anatomical experiments in several species (Lund and Boothe, 1975; Burkhalter, 1989; Usrey and Fitzpatrick, 1996; Wiser and Callaway, 1996) had also demonstrated that layer 6 gives rise to two separate intracortical pathways. Pooling the results of these anatomical studies with our own suggests a common feature of the laminar organization: cells that project to different intracortical targets have distinct functional characteristics.