bluuebunny/crossref_metadata_2025_split huggingface dataset:
GAT-3, a High-Affinity GABA Plasma Membrane Transporter, Is Localized to Astrocytic Processes, and It Is Not Confined to the Vicinity of GABAergic Synapses in the Cerebral Cortex
Authors: Minelli Andrea , DeBiasi Silvia , Brecha Nicholas C. , Vitellaro Zuccarello Laura , Conti Fiorenzo 
Published: April 2018

The termination of GABA synaptic action by high-affinity, Na+-dependent, neuronal, and glial plasma membrane transporters plays an important role in regulating neuronal activity in physiological and pathological conditions. We have investigated the cellular localization and distribution in the cerebral cortex of adult rats of one GABA transporter (GAT), GAT-3, by immunocytochemistry with affinity-purified polyclonal antibodies directed to its predicted C terminus that react monospecifically with a protein of ∼70 kDa.Light microscopic studies revealed specific GAT-3 immunoreactivity (ir) in small punctate structures, and it was never observed in fibers or cell bodies. No changes in immunostaining were observed in sections incubated with GAT-3 antibodies preadsorbed with the related rat GAT-1 or mouse GAT-2/BGT-1 C-terminal peptides, whereas in sections incubated with GAT-3 antibodies preadsorbed with rat GAT-3 C-terminal peptide, ir was not present. The highest number of GAT-3-positive puncta was in layer IV and in a narrow band corresponding to layer Vb, followed by layers II and III. Many GAT-3-positive puncta were in close association with pyramidal and nonpyramidal neuron cell bodies. Ultrastructural studies showed that GAT-3 ir was localized exclusively to astrocytic processes, which were found in the neuropil and adjacent to axon terminals having either symmetric or asymmetric specializations. In sections processed by both preembedding labeling for GAT-3 and postembedding immunogold labeling for GABA, only some of the GAT-3-positive astrocytic processes were found close to GABAergic profiles.These findings on the localization of GAT-3 in the cerebral cortex indicate that this transporter mediates GABA uptake into glial cells, and suggest that glial GABA uptake may function to limit the spread of GABA from the synapse, as well as to regulate overall GABA levels in the neuropil.
AMPA Receptor Flip/Flop Mutants Affecting Deactivation, Desensitization, and Modulation by Cyclothiazide, Aniracetam, and Thiocyanate
Authors: Partin Kathryn M. , Fleck Mark W. , Mayer Mark L. 
Published: April 2018

AMPA receptor GluRA subunits with mutations at position 750, a residue shown previously to control allosteric regulation by cyclothiazide, were analyzed for modulation of deactivation and desensitization by cyclothiazide, aniracetam, and thiocyanate. Point mutations from Ser to Asn, Ala, Asp, Gly, Gln, Met, Cys, Thr, Leu, Val, and Tyr were constructed in GluRAflip. The last four of these mutants were not functional; S750D was active only in the presence of cyclothiazide, and the remaining mutants exhibited altered rates of deactivation and desensitization for control responses to glutamate, and showed differential modulation by cyclothiazide and aniracetam. Results from kinetic analysis are consistent with aniracetam and cyclothiazide acting via distinct mechanisms. Our experiments demonstrate for the first time the functional importance of residue 750 in regulating intrinsic channel-gating kinetics and emphasize the biological significance of alternative splicing in the M3–M4 extracellular loop.
Age-Dependent Neuronal and Synaptic Degeneration in Mice Transgenic for the C Terminus of the Amyloid Precursor Protein
Authors: Oster-Granite Mary Lou , McPhie Donna L. , Greenan Jane , Neve Rachael L. 
Published: April 2018

The molecular basis for the degeneration of neurons and the deposition of amyloid in plaques and in the cerebrovasculature in Alzheimer’s disease (AD) is incompletely understood. We have proposed that one molecule common to these abnormal processes is a fragment of the Alzheimer amyloid precursor protein (APP) comprising the C-terminal 100 amino acids of this molecule (APP-C100). We tested this hypothesis by creating transgenic mice expressing APP-C100 in the brain. We report here that aging (18–28 month) APP-C100 transgenic mice exhibit profound degeneration of neurons and synapses in Ammon’s horn and the dentate gyrus of the hippocampal formation. Of the 106 transgenic mice between 8 and 28 months of age that were examined, all of those older than 18 months displayed severe hippocampal degeneration. The numerous degenerating axonal profiles contained increased numbers of neurofilaments, whorls of membrane, and accumulations of debris resembling secondary lysosomes near the cell body. The dendrites of degenerating granule and pyramidal cells contained disorganized, wavy microtubules. Cerebral blood vessels had thickened refractile basal laminae, and microglia laden with debris lay adjacent to larger venous vessels. Mice transgenic for Flag-APP-C100 (in which the hydrophilic Flag tag was fused to the N terminus of APP-C100) showed a similar degree of neurodegeneration in the hippocampal formation as early as 12 months of age. The 45 control mice displayed only occasional necrotic cells and no extensive cell degeneration in the same brain regions. These findings show that APP-C100 is capable of causing some of the neuropathological features of AD.
An Explanation for Reflex Blink Hyperexcitability in Parkinson’s Disease. II. Nucleus Raphe Magnus
Authors: Basso Michele A. , Evinger Craig 
Published: April 2018

Hyperexcitable reflex blinks are a cardinal sign of Parkinson’s disease. The first step in the circuit linking the basal ganglia and brainstem reflex blink circuits is the inhibitory nigrostriatal pathway (Basso et al., 1996). The current study reports the circuits linking the superior colliculus (SC) to trigeminal reflex blink circuits. Microstimulation of the deep layers of the SC suppresses subsequent reflex blinks at a latency of 5.4 msec. This microstimulation does not activate periaqueductal gray antinociceptive circuits. The brainstem structure linking SC to reflex blink circuits must suppress reflex blinks at a shorter latency than the SC and produce the same effect on reflex blink circuits as SC stimulation, and removal of the structure must block SC modulation of reflex blinks. Only the nucleus raphe magnus (NRM) meets these requirements. NRM microstimulation suppresses reflex blinks with a latency of 4.4 msec. Like SC stimulation, NRM microstimulation reduces the responsiveness of the spinal trigeminal nucleus. Finally, blocking the receptors for the NRM transmitter serotonin eliminates SC modulation of reflex blinks, and muscimol inactivation of the NRM transiently prevents SC modulation of reflex blinks. Thus, the circuit through which the basal ganglia modulates reflex blinking is (1) the substantia nigra pars reticulata inhibits SC neurons, (2) the SC excites tonically active NRM neurons, and (3) NRM neurons inhibit spinal trigeminal neurons involved in reflex blink circuits.
Neurotrophin-3 Is a Survival FactorIn Vivofor Early Mouse Trigeminal Neurons
Authors: Wilkinson George A. , Fariñas Isabel , Backus Carey , Yoshida Cathleen K. , Reichardt Louis F. 
Published: April 2018

Mice lacking neurotrophin-3 (NT-3) have been shown previously to be born with severe sensory deficits. This study characterizes the developmental course of this deficit in the trigeminal sensory ganglion, which in NT-3 homozygous mutants contains only 35% of the normal number of neurons at birth. At embryonic day 10.5 (E10.5), normal numbers of neurons, as assessed by expression of neurofilament protein and of total cells, are present in the ganglia of mutant homozygotes. During the next 3 d (E10.5–E13.5), virtually all of the deficit develops, after which mutant animals retain only ∼30% the normal number of neurons. Quantification of neuronal and neuronal precursor numbers in normal and mutant animals reveals that neurons are specifically depleted in the absence of NT-3. A deficiency in precursor proliferation is only seen after most of the neuronal deficit has developed. Numbers of apoptotic cells in the ganglia of mutant animals are elevated during this same interval, indicating that the neuronal deficit is caused, in large part, by increased cell death of embryonic neurons.To determine sources of NT-3 in the trigeminal system, we examined the expression pattern of β-galactosidase in mice, in which lacZ has replaced the NT-3 coding exon. E10.5–E11.5 embryos exhibit intense reporter expression throughout the mesenchyme and epithelia of the first branchial arch. β-galactosidase expression in E13.5 embryos is largely confined to the oral epithelium and the mesenchyme underlying the skin. Throughout the E10.5–E13.5 interval, the trigeminal ganglion and its targets in the CNS do not express reporter activity.We conclude that NT-3 acts principally as a peripherally derived survival factor for early trigeminal neurons.
5HT4Receptors Couple Positively to Tetrodotoxin-Insensitive Sodium Channels in a Subpopulation of Capsaicin-Sensitive Rat Sensory Neurons
Authors: Cardenas Carla G. , Del Mar Lucinda P. , Cooper Brian Y. , Scroggs Reese S. 
Published: April 2018

The distribution of tetrodotoxin (TTX)-sensitive and -insensitive Na+currents and their modulation by serotonin (5HT) and prostaglandin E2(PGE2) was studied in four different types of dorsal root ganglion (DRG) cell bodies (types 1, 2, 3, and 4), which were previously identified on the basis of differences in membrane properties (Cardenas et al., 1995). Types 1 and 2 DRG cells expressed TTX-insensitive Na+currents, whereas types 3 and 4 DRG cells exclusively expressed TTX-sensitive Na+currents.Application of 5HT (1–10 μm) increased TTX-insensitive Na+currents in type 2 DRG cells but did not affect Na+currents in type 1, 3, or 4 DRG cells. The 5HT receptor involved resembled the 5HT4subtype. It was activated by 5-methoxy-N,N-dimethyltryptamine (10 μm) but not by 5-carboxyamidotryptamine (1 μm), (+)-8-hydroxydipropylaminotetralin (10 μm), or 2-methyl-5HT (10 μm), and was blocked by ICS 205-930 with an EC50of ∼2 μmbut not by ketanserin (1 μm). PGE2(4 or 10 μm) also increased Na+currents in varying portions of cells in all four groups.The effect of 5HT and PGE2on Na+currents was delayed for 20–30 sec after exposure to 5HT, suggesting the involvement of a cytosolic diffusible component in the signaling pathway. The agonist-mediated increase in Na+current, however, was not mimicked by 8-chlorophenylthio-cAMP (200 μm), suggesting the possibility that cAMP was not involved.The data suggest that the 5HT- and PGE2-mediated increase in Na+current may be involved in hyperesthesia in different but overlapping subpopulations of nociceptors.
Instantaneous Perturbation of Dentate Interneuronal Networks by a Pressure Wave-Transient Delivered to the Neocortex
Authors: Toth Zsolt , Hollrigel Greg S. , Gorcs Tamas , Soltesz Ivan 
Published: April 2018

Whole-cell patch-clamp recordings and immunocytochemical experiments were performed to determine the short- and long-term effects of lateral fluid percussion head injury on the perisomatic inhibitory control of dentate granule cells in the adult rat, with special reference to the development of trauma-induced hyperexcitability. One week after the delivery of a single, moderate (2.0–2.2 atm) mechanical pressure wave to the neocortex, the feed-forward inhibitory control of dentate granule cell discharges was compromised, and the frequency of miniature IPSCs was decreased. Consistent with the electrophysiological data, the number of hilar parvalbumin (PV)- and cholecystokinin (CCK)-positive dentate interneurons supplying the inhibitory innervation of the perisomatic region of granule cells was decreased weeks and months after head injury. The initial injury to the hilar neurons took place instantaneously after the impact and did not require the recruitment of active physiological processes. Furthermore, the decrease in the number of PV- and CCK-positive hilar interneurons was similar to the decrease in the number of the AMPA-type glutamate receptor subunit 2/3-immunoreactive mossy cells, indicating that the pressure wave-transient causes injurious physical stretching and bending of most cells that are large and not tightly packed in a cell layer.These results reveal for the first time that moderate pressure wave-transients, triggered by traumatic head injury episodes, impact the dentate neuronal network in a unique temporal and spatial pattern, resulting in a net decrease in the perisomatic control of granule cell discharges.
Origin and Route of Tangentially Migrating Neurons in the Developing Neocortical Intermediate Zone
Authors: Tamamaki Nobuaki , Fujimori Kazuhiro E. , Takauji Rumiko 
Published: April 2018

Neuroblasts produced in the ventricular zone of the neocortex migrate radially and form the cortical plate, settling in an inside-out order. It is also well known that the tangential cell migration is not negligible in the embryonic neocortex. To have a better understanding of the tangential cell migration in the cortex, we disturbed the migration by making a cut in the neocortex, and we labeled the migrating cells with 1,1′-dioctodecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate (DiI)in vivoandin vitro. We also determined the birth dates of the cells.Disturbance of tangential cell migration caused an accumulation and disappearance of microtubule-associated protein 2 immunoreactive (MAP2-IR) cells on the ventral and dorsal side of the cut, respectively, which indicated that most of the MAP2-IR cells in the intermediate zone (IZ) were migrating toward the dorsal cortex. The DiI injection studyin vivoconfirmed the tendency of the direction of cell migration and suggested the origin of the cells to be in the lateral ganglionic eminence (LGE). DiI injection into the LGEin vitroconfirmed that the LGE cells cross the corticostriatal boundary and enter the IZ of the neocortex. The migrating cells acquired multipolar shape in the IZ of the dorsal cortex and seemed to reside there. A 5-bromo-deoxyuridine incorporation study revealed that the migrating MAP2-IR cells in the IZ were early-generated neurons. We concluded that the majority of tangentially migrating cells were generated in the LGE and identified as a distinct population that was assumed not to have joined the cortical plate.
Nerve Growth Factor Treatment Increases Brain-Derived Neurotrophic Factor Selectively in TrkA-Expressing Dorsal Root Ganglion Cells and in Their Central Terminations within the Spinal Cord
Authors: Michael G. J. , Averill S. , Nitkunan A. , Rattray M. , Bennett D. L. H. , Yan Q. , Priestley J. V. 
Published: April 2018

Using immunocytochemistry andin situhybridization, we have examined the expression of brain-derived neurotrophic factor (BDNF) and of neurotrophin receptors in dorsal root ganglion cells. In the adult rat, BDNF mRNA and protein were found mainly in the subpopulation of cells that express the nerve growth factor (NGF) receptor trkA and the neuropeptide calcitonin gene-related peptide (CGRP). NGF increased BDNF within the trkA/CGRP cells to the extent that almost 90% of trkA cells contained BDNF mRNA after intrathecal NGF treatment, and 80–90% of BDNF-expressing cells contained trkA. Non-trkA cells that expressed BDNF included some trkC cells and some small cells that labeled with the lectinGriffonia simplicifoliaIB4, a marker for cells that do not express trks. However, very few trkB cells expressed either BDNF mRNA or protein, and NGF did not increase BDNF expression in non-trkA cells. BDNF protein was anterogradely transported both peripherally and centrally. The central transport resulted in BDNF immunoreactivity in CGRP containing terminal arbors in the dorsal horn of the spinal cord, and this immunoreactivity was increased by NGF treatment. Electron microscopic analysis revealed that the BDNF immunoreactivity was present in finely myelinated and unmyelinated axons and in axon terminals, where it was most concentrated over dense-cored vesicles.Our data do not support an autocrine or paracrine role for BDNF within normal dorsal root ganglia, but indicate that BDNF may act as an anterograde trophic messenger. NGF levels in the periphery could influence dorsal horn neurons via release of BDNF from primary afferents.
Functional Properties of Perigeniculate Inhibition of Dorsal Lateral Geniculate Nucleus Thalamocortical NeuronsIn Vitro
Authors: Sanchez-Vives Maria V. , McCormick David A. 
Published: April 2018

The properties of the inhibitory influence of neurons in the perigeniculate (PGN) nucleus on thalamocortical cells were examined with intracellular recordings in the ferret geniculate slice maintainedin vitro. Activation of PGN neurons with the local application of glutamate caused IPSPs in thalamocortical neurons that were mediated by both GABAAand GABABreceptors, as well as the activation of spindle waves.With low intensity stimulation of the PGN, local application of bicuculline to the dorsal lateral geniculate nucleus (LGNd) strongly inhibited evoked and spindle-associated IPSPs, indicating that these are largely mediated by GABAAreceptors. The generation of GABABreceptor-mediated IPSPs in thalamocortical cells that were large enough to generate rebound low threshold Ca2+spikes required substantially increased activation of the PGN with glutamate.The activation of synchronous bicuculline-induced slowed oscillations in thalamocortical neurons required the block of GABAAreceptors in the LGNd as well as in the PGN. These results indicate that bursts of action potentials in PGN neurons can result in the activation of both GABAAand GABABreceptors in thalamocortical neurons, with the strong activation of GABABreceptors requiring an intense, simultaneous discharge of a number of PGN neurons. Functionally, these results suggest that PGN neurons inhibit thalamocortical cells preferentially through the activation of GABAAreceptors, although the strong activation of GABABreceptors may occur under pathological conditions and contribute to the generation of abnormal, synchronous slow oscillations.
Mutation Causing Autosomal Dominant Nocturnal Frontal Lobe Epilepsy Alters Ca2+Permeability, Conductance, and Gating of Human α4β2 Nicotinic Acetylcholine Receptors
Authors: Kuryatov Alexander , Gerzanich Volodymyr , Nelson Mark , Olale Felix , Lindstrom Jon 
Published: April 2018

A mutation (S247F) in the channel-lining domain (M2) of the α4 nicotinic acetylcholine receptor (AChR) subunit has previously been linked genetically to autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE).To better understand the functional significance of this mutation, we characterized the properties of mutant and wild-type human α4β2 AChRs expressed inXenopusoocytes. Both had similar expression levels and EC50values for ACh and nicotine. Substantial use-dependent functional upregulation was found for mutant α4β2 AChRs, but not for wild type. Mutant AChR responses showed faster desensitization, slower recovery from desensitization, less inward rectification, and virtually no Ca2+permeability as compared with wild-type α4β2 AChRs. Addition of the α5 subunit restored Ca2+permeability to the mutant α4β2α5 AChRs. At −80 mV, wild-type α4β2 AChR single channel currents exhibited two conductances, each with two mean open times (γ1= 17 pS, τ1= 3.7 msec, and τ2= 23.4 msec; γ2= 28 pS, τ1= 1.9 msec, and τ2= 8.1 msec). In contrast, mutant AChRs exhibited only one conductance of 11 pS, with τ1= 1.9 msec and τ2= 4.1 msec.The net effect of the mutation is to reduce AChR function. This could result in the hyperexcitability characteristic of epilepsy if the mutant AChRs were part of an inhibitory circuit, e.g., presynaptically regulating the release of GABA. In the minority of AChRs containing the α5 subunit, the overall functionality of these AChRs could be maintained despite the mutation in the α4 subunit.
Subcortical Input to the Smooth and Saccadic Eye Movement Subregions of the Frontal Eye Field inCebusMonkey
Authors: Tian Jun-ru , Lynch James C. 
Published: April 2018

We have recently identified two functional subregions in the frontal eye field (FEF) of theCebusmonkey, a smooth eye movement subregion (FEFsem) and a saccadic subregion (FEFsac). The thalamic input to these two subregions was studied and quantified to gain more information about the influence of the cerebellum and basal ganglia on the oculomotor control mechanisms of the cerebral cortex. A recent study using transneuronal transport of virus demonstrated that there are neurons in the basal ganglia and cerebellum that project to the FEFsac with only a single intervening synapse (Lynch et al., 1994). In the present study, we concentrated on the thalamic input to the FEFsem to define possible basal ganglia–thalamus–cortex and cerebellum–thalamus–cortex channels of information flow to the FEFsem. We localized the functional subregions using low threshold microstimulation, and retrogradely transported fluorescent tracers were then placed into the FEFsem and FEFsac.The neurons that project to the FEFsem are distributed in (1) the rostral portion of the ventral lateral nucleus, pars caudalis, (2) the caudal portion of the ventral lateral nucleus, pars caudalis, (3) the mediodorsal nucleus, (4) the ventral anterior nucleus, pars parvocellularis, and (5) the ventral anterior nucleus, pars magnocellularis. In contrast, the large majority of neurons that project to the FEFsac are located in the paralaminar region of the mediodorsal nucleus. The FEFsac and FEFsem thus each receive neural input frombothbasal ganglia-receiving and cerebellar-receiving cell groups in the thalamus, but each receives input from a unique combination of thalamic nuclei.
Myosin VIIA Is Required for Aminoglycoside Accumulation in Cochlear Hair Cells
Authors: Richardson G. P. , Forge A. , Kros C. J. , Fleming J. , Brown S. D. M. , Steel K. P. 
Published: April 2018

Myosin VIIA is expressed by sensory hair cells and has a primary structure predicting a role in membrane trafficking and turnover, processes that may underlie the susceptibility of hair cells to aminoglycoside antibiotics. [3H]Gentamicin accumulation and the effects of aminoglycosides were therefore examined in cochlear cultures of mice with different missense mutations in the myosin VIIA gene,Myo7a, to see whether myosin VIIA plays a role in aminoglycoside ototoxicity. Hair cells from homozygous mutantMyo7ash1mice, with a mutation in a nonconserved region of the myosin VIIA head, respond rapidly to aminoglycoside treatment and accumulate high levels of gentamicin. Hair cells from homozygous mutantMyo7a6Jmice, with a mutation at a highly conserved residue close to the ATP binding site of the myosin VIIA head, do not accumulate [3H]gentamicin and are protected from aminoglycoside ototoxicity. Hair cells from heterozygotes of both alleles accumulate [3H]gentamicin and respond to aminoglycosides.Although aminoglycoside uptake is thought to be via apical surface-associated endocytosis, coated pit numbers on the apical membrane of heterozygous and homozygousMyo7a6Jhair cells are similar. Pulse–chase experiments with cationic ferritin confirm that the apical endocytotic pathway is functional in homozygousMyo7a6Jhair cells. Transduction currents can be recorded from both heterozygous and homozygousMyo7a6Jhair cells, suggesting it is unlikely that the drug enters via diffusion through the mechanotransducer channel. The results show that myosin VIIA is required for aminoglycoside accumulation in hair cells. Myosin VIIA may transport a putative aminoglycoside receptor to the hair cell surface, indirectly translocate it to sites of membrane retrieval, or retain it in the endocytotic pathway.