bluuebunny/crossref_metadata_2025 huggingface dataset:
Myelin basic protein gene expression in neurons: developmental and regional changes in protein targeting within neuronal nuclei, cell bodies, and processes
Authors: Landry CF , Ellison JA , Pribyl TM , Campagnoni C , Kampf K , Campagnoni AT
Published: April 2018

The myelin basic protein (MBP) gene is part of the golli-mbp gene complex. In mouse, the golli-mbp gene produces two families of mRNAs from different transcription start sites that generate either MBPs or golli proteins (which contain MBP sequences in addition to unique peptide sequences). In situ hybridization and immunocytochemical analyses indicate that golli products are expressed in selected neuronal populations in postnatal mouse brain, in addition to oligodendrocytes, as shown earlier. The principal subcellular location of golli proteins in neurons was in axonal and dendritic processes. In a small subset of neurons, golli proteins were located in nuclei. With development and neuronal maturation, golli-mbp expression decreased and/or there was a striking shift in subcellular localization from nuclei and cell soma to the cell processes in specific neuronal populations. Golli protein was localize in neurites of migrating cerebellar granule cells, but it shifted to a nuclear localization when the cells took up residence in the internal granule cell layer. In some regions, (e.g., olfactory bulb and cerebellum) golli proteins were expressed over the entire postnatal period examined (birth to 75 d). The unique patterns of developmental expression within individual populations of neurons, and the unusual shift in subcellular localization of golli proteins with neuronal migration and maturation, suggest a complex regulation of this gene at both the transcriptional and posttranslational levels. The data also suggest that the cellular function(s) of the golli proteins is very different from the structurally related MBPs.
Cloning OF P2X5 and P2X6 receptors and the distribution and properties of an extended family of ATP-gated ion channels
Authors: Collo G , North RA , Kawashima E , Merlo-Pich E , Neidhart S , Surprenant A , Buell G
Published: April 2018

Two new P2X receptor cDNAs (P2X5 and P2X6) were isolated and expressed. All six proteins are 36–48 percent identical and seem to have two transmembrane segments with a large extracellular loop. Functionally, P2X5 and P2X6 receptors most resemble P2X2 and P2X4; they desensitize only slowly and do not respond to alpha beta methylene-ATP. P2X6 receptors, like P2X4, receptors, are not blocked by the antagonists suramin and pyridoxal-5-phosphate-6-azophenyl-2′,4′-disulfonic acid. P2X6 and P2X5 receptors express at lower levels than P2X1-P2X4 receptors do, perhaps indicating that they do not normally form homomultimeric channels. P2X6 and P2X4 are the receptors expressed most heavily in brain, where their RNAs have a widespread and extensively overlapping distribution. The spinal cord expresses all receptors except P2X3. P2X2, P2X4, and P2X6, are the most abundant in the dorsal horn. Sensory neurons of the trigeminal, dorsal root, and nodose ganglia express all six RNAs; P2X3 is found only there. The functional properties and tissue distribution of these six P2X receptors indicate new roles for ATP-gated ion channels.
Role of glutamic acid decarboxylase in the prepubertal inhibition of the luteinizing hormone releasing hormone release in female rhesus monkeys
Authors: Mitsushima D , Marzban F , Luchansky LL , Burich AJ , Keen KL , Durning M , Golos TG , Terasawa E
Published: April 2018

To investigate further the role of GABA in the onset of puberty, this study examines whether glutamic acid decarboxylase (GAD), the catalytic enzyme for GABA synthesis, is involved in the suppression of luteinizing hormone releasing hormone (LHRH) before puberty in rhesus monkeys. First, both GAD67 and GAD65 mRNAs were detectable by reverse transcription-PCR analysis in the preoptic area, medio-basal hypothalamus, posterior hypothalamic area, and hippocampus of the monkey brain. Second, effects of antisense oligodeoxynucleotides (D- oligos) for GAD67 and GAD65 mRNAs on LHRH release were examined in conscious female rhesus monkeys at the prepubertal stage using a push- pull perfusion method. The GAD67 or GAD65 antisense D-oligos or scrambled D-oligos were infused directly into the stalk-median eminence. Both the GAD67 and the GAD65 antisense D-oligos induced a large and prompt increase in LHRH release, whereas the scrambled D- oligos did not induce any significant effect. The results suggest that the removal of GABA inhibition by interfering with GAD synthesis is effective in increasing LHRH release in prepubertal monkeys. Third, the specificity of the antisense D-oligos on GAD levels was examined by incubating basal hypothalami with D-oligos in vitro and subsequent Western blot analysis. The antisense D-oligos consistently decreased the proteins GAD67 and GAD65 compared with respective control D-oligos. We conclude that the decrease of tonic GABAergic inhibition and maturational changes in GAD synthesis may be critical factors for the onset of puberty in nonhuman primates.
In vivo growth factor expansion of endogenous subependymal neural precursor cell populations in the adult mouse brain
Authors: Craig CG , Tropepe V , Morshead CM , Reynolds BA , Weiss S , van der Kooy D
Published: April 2018

The lateral ventricle subependyma in the adult mammalian forebrain contains both neural stem and progenitor cells. This study describes the in situ modulation of these subependymal neural precursor populations after intraventricular administration of exogenous growth factors. In vivo infusion of epidermal growth factor (EGF) into adult mouse forebrain for 6 consecutive days resulted in a dramatic increase in the proliferation and total number of subependymal cells and induced their migration away from the lateral ventricle walls into adjacent parenchyma. Immediately after EGF infusion, immunohistochemical characterization of the EGF-expanded cell population demonstrated that >95% of these cells were EGF receptor- and nestin-positive, whereas only 0.9% and 0.2% labeled for astrocytic and neuronal markers, respectively. Seven weeks after EGF withdrawal, 25% of the cells induced to proliferate after 6d of EGF were still detectable; 28% of these cells had differentiated into new astrocytes and 3% into new neurons in the cortex, striatum, and septum. Newly generated oligodendrocytes were also observed. These in vivo results (1) confirm the existence of EGF-responsive subependymal neural precursor cells in the adult mouse forebrain and (2) suggest that EGF acts directly as a proliferation, survival, and migration factor for subependymal precursor cells to expand these populations and promote the movement of these cells into normal brain parenchyma. Thus, in situ modulation of endogenous forebrain precursor cells represents a novel model for studying neural development in the adult mammalian brain and may provide insights that will achieve adult replacement of neurons and glia lost to disease or trauma.
Peripheral cell types contributing to the hyperalgesic action of nerve growth factor in inflammation
Authors: Woolf CJ , Ma QP , Allchorne A , Poole S
Published: April 2018

The contribution of nerve growth factor (NGF) to inflammatory hyperalgesia potentially could be mediated by any of the three peripheral cell types that express trkA, the high-affinity NGF receptor: inflammatory cells, sympathetic neurons, and primary sensory neurons. To investigate their relative involvement, the effects of sympathectomy and mast cell degranulation were examined on the local inflammation produced by an intraplantar injection of complete Freund's adjuvant in the adult rat. Sympathectomy, produced by neonatal guanethidine treatment, elevated basal NGF levels in the skin but did not attenuate a further increase in NGF during inflammation. Although the onset of inflammatory hyperalgesia was delayed in sympathectomized animals, peak sensitivity was not affected and was still NGF-dependent. In contrast, mast cell degranulation produced by several days of treatment with the cationic secretagogue compound 48/80, while also increasing basal NGF levels, prevented a further increase in NGF levels and attenuated hypersensitivity during inflammation. Neither manipulation modified the inflammatory upregulation of interleukin- 1beta. We conclude that sympathetic neurons contribute transiently to inflammatory hyperalgesia, but that mast cells and sensory neurons are important sites for the sustained action of NGF in producing increased sensitivity during inflammation.
Contributions of individual layer 6 pyramidal neurons to local circuitry in macaque primary visual cortex
Authors: Wiser AK , Callaway EM
Published: April 2018

We have studied the contributions of individual layer 6 pyramidal neurons in macaque primary visual cortex to local cortical circuitry by intracellular labeling and analysis of the morphologies of 58 neurons. These neurons are separated based on the laminar specificity of axonal and dendritic arbors into two classes, class I and class II, and into several types within these classes. Class I neurons project axons heavily and predominantly to layer 4C, whereas class II neurons have axonal projections primarily to layers other than 4C. Only 16 of the 58 neurons in our sample (28 percent) project to the white matter. Class I projection neurons are found at the top and bottom of layer 6, suggesting that they project to the lateral geniculate nucleus, whereas class II projection neurons are located in the middle of layer 6, suggesting that they project to the claustrum. The different types of class I neurons are distinguished from one another based on the sublaminar specificity of their axonal and dendritic arbors within layer 4, where they are biased toward compartments dominated by input from different functional streams. They are also distinct in their distributions within the depth of layer 6. The distinctive characteristics of the neuronal types we have identified suggest that each receives input from different sources and projects to a set of targets that is functionally appropriate. Thus, each type is likely to contribute uniquely to computations within V1 and extrinsically.
Microdialysis perfusion of 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH- DPAT) in the dorsal raphe nucleus decreases serotonin release and increases rapid eye movement sleep in the freely moving cat
Authors: Portas CM , Thakkar M , Rainnie D , McCarley RW
Published: April 2018

In vivo microdialysis was used to analyze the role of dorsal raphe nucleus (DRN) neurons in regulating the sleep-waking cycle. Measurements of extracellular serotonin (5-HT) were made in the DRN of freely moving adult cats before and during microdialysis perfusion of 8- hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), a selective 5-HT1A receptor agonist, in artificial CSF. Behavioral state alterations were measured by simultaneous polygraphic recordings. During waking and artificial CSF perfusion of probes histologically localized to the DRN, extracellular 5-HT was 4 fmol/7.5 micro L dialysate sample. With the addition of 8-OH-DPAT (10 microM in artificial CSF) to the perfusate, 5- HT levels in the same state decreased 50%, to 2 fmol/sample (p < 0.01), presumably through 5-HT1A autoreceptor-mediated inhibition of serotonergic neural activity. Concomitantly, this 8-OH-DPAT perfusion produced a short latency, threefold increase in rapid eye movement (REM) sleep, from 10 to 30% of the total recorded time (p < 0.05), whereas waking was not significantly affected. In contrast, and suggesting DRN specificity, 8-OH-DPAT delivery through a probe in the aqueduct did not increase REM sleep but rather tended to increase waking and decrease slow wave sleep. The data on REM sleep provide the first biochemically validated and direct evidence that suppression of DRN serotonergic activity increases REM sleep, and furnish a key complement to our laboratory's in vitro data indicating that mesopontine cholinergic neurons, a target of DRN projections, are inhibited by 5-HT. The 8-OH-DPAT-induced reduction of DRN 5-HT is consistent with the hypothesis that the concomitant REM sleep disinhibition is mediated by DRN serotonergic projections to mesopontine cholinergic neurons, which other data implicate in REM sleep production.
Cannabinoid Receptor Agonists Inhibit Glutamatergic Synaptic Transmission in Rat Hippocampal Cultures
Authors: Shen Maoxing , Piser Timothy M. , Seybold Virginia S. , Thayer Stanley A.
Published: April 2018

Activation of cannabinoid receptors inhibits voltage-gated Ca2+channels and activates K+channels, reminiscent of other G-protein-coupled signaling pathways that produce presynaptic inhibition. We tested cannabinoid receptor agonists for effects on excitatory neurotransmission between cultured rat hippocampal neurons. Reducing the extracellular Mg2+concentration to 0.1 mmelicited repetitive, transient increases in intracellular Ca2+concentration ([Ca2+]ispikes) that resulted from bursts of action potentials, as measured by combined whole-cell current clamp and indo-1-based microfluorimetry. Pharmacological characterization indicated that the [Ca2+]ispikes required glutamatergic synaptic transmission. Cannabinoid receptor ligands inhibited stereoselectively the frequency of [Ca2+]ispiking in the rank order of potency: CP 54,939 > CP 55,940 > Win 55,212-2 > anandamide, with EC50values of 0.36, 1.2, 2.7, and 71 nm, respectively. CP 55,940 was potent, but not efficacious, and reversed the inhibition produced by Win 55,212-2, indicating that it is a partial agonist. Inhibition of [Ca2+]ispiking by Win 55,212-2 was prevented by treatment of cultures with active, but not heat-treated, pertussis toxin. Win 55,212-2 (100 nm) inhibited stereoselectively CNQX-sensitive excitatory postsynaptic currents (EPSCs) elicited by presynaptic stimulation with an extracellular electrode, but did not affect the presynaptic action potential or currents elicited by direct application of kainate. Consistent with a presynaptic site of action, Win 55,212-2 increased both the number of response failures and the coefficient of variation of the evoked EPSCs. In contrast, cannabimimetics did not affect bicuculline-sensitive inhibitory postsynaptic currents. Thus, activation of cannabinoid receptors inhibits the presynaptic release of glutamate via an inhibitory G-protein.
[Ca2+]iElevations Detected by BK Channels during Ca2+Influx and Muscarine-Mediated Release of Ca2+from Intracellular Stores in Rat Chromaffin Cells
Authors: Prakriya Murali , Solaro Christopher R. , Lingle Christopher J.
Published: April 2018

Submembrane [Ca2+]ichanges were examined in rat chromaffin cells by monitoring the activity of an endogenous Ca2+-dependent protein: the large conductance Ca2+- and voltage-activated K+channel (also known as the BK channel). The Ca2+and voltage dependence of BK current inactivation and conductance were calibrated first by using defined [Ca2+]isalines. This information was used to examine submembrane [Ca2+]ielevations arising out of Ca2+influx and muscarine-mediated release of Ca2+from intracellular stores. During Ca2+influx, some BK channels are exposed to [Ca2+]iof at least 60 μm. However, the distribution of this [Ca2+]ielevation is highly nonuniform so that the average [Ca2+]idetected when all BK channels are activated is only ∼10 μm. Intracellular dialysis with 1 mmor higher EGTA spares only the BK channels activated by the highest [Ca2+]iduring influx, whereas dialysis with 1 mmor higher BAPTA blocks activation of all BK channels. Submembrane [Ca2+]ielevations fall rapidly after termination of short (5 msec) Ca2+influx steps but persist above 1 μmfor several hundred milliseconds after termination of long (200 msec) influx steps. In contrast to influx, the submembrane [Ca2+]ielevations produced by release of intracellular Ca2+by muscarinic actetylcholine receptor (mAChR) activation are much more uniform and reach peak levels of 3–5 μm. Our results suggest that during normal action potential activity only 10–20% of BK channels in each chromaffin cell see sufficient [Ca2+]ito be activated.
Neurotrophin-3 Antibodies Disrupt the Normal Development of the Chick Retina
Authors: Bovolenta Paola , Frade José-Marı́a , Martı́ Elisa , Rodrı́guez-Peña Marı́a-Angeles , Barde Yves-Alain , Rodrı́guez-Tébar Alfredo
Published: April 2018

When chick embryos are treated with a monoclonal antibody specifically blocking the activity of neurotrophin-3 (NT-3), the development of the retina is profoundly affected. Fewer axons are found in the optic nerve, and the retina shows abnormalities in all layers. Early during retinogenesis, the proportion of dividing cells is higher in NT-3-deprived embryos compared with age-matched controls and that of differentiated neurons is smaller. The NT-3 receptor trkC is expressed early by a majority of retinal cells, and NT-3 is present in the retina at the earliest stage studied. Initially, it is located mainly in the pigmented epithelium, with a shift toward the neural retina as development proceeds. Thus, NT-3 seems to be an essential intrinsic signal acting early in development to promote the differentiation and survival of many retinal neurons.
The Structure of Spatial Receptive Fields of Neurons in Primary Auditory Cortex of the Cat
Authors: Brugge John F. , Reale Richard A. , Hind Joseph E.
Published: April 2018

Transient broad-band stimuli that mimic in their spectrum and time waveform sounds arriving from a speaker in free space were delivered to the tympanic membranes of barbiturized cats via sealed and calibrated earphones. The full array of such signals constitutes a virtual acoustic space (VAS). The extracellular response to a single stimulus at each VAS direction, consisting of one or a few precisely time-locked spikes, was recorded from neurons in primary auditory cortex. Effective sound directions form a virtual space receptive field (VSRF). Near threshold, most VSRFs were confined to one quadrant of acoustic space and were located on or near the acoustic axis. Generally, VSRFs expanded monotonically with increases in stimulus intensity, with some occupying essentially all of the acoustic space. The VSRF was not homogeneous with respect to spike timing or firing strength. Typically, onset latency varied by as much as 4–5 msec across the VSRF. A substantial proportion of recorded cells exhibited a gradient of first-spike latency within the VSRF. Shortest latencies occupied a core of the VSRF, on or near the acoustic axis, with longer latency being represented progressively at directions more distant from the core. Remaining cells had VSRFs that exhibited no such gradient. The distribution of firing probability was mapped in those experiments in which multiple trials were carried out at each direction. For some cells there was a positive correlation between latency and firing probability.
Localization of the Somatostatin Receptor SST2Ain Rat Brain Using a Specific Anti-Peptide Antibody
Authors: Dournaud Pascal , Gu Yi Z. , Schonbrunn Agnes , Mazella Jean , Tannenbaum Gloria S. , Beaudet Alain
Published: April 2018

Biological actions of somatostatin are exerted via a family of receptors, for which five genes recently have been cloned. However, none of these receptor proteins has been visualized yet in the brain. In the present study, the regional and cellular distribution of the somatostatin sst2Areceptor was investigated via immunocytochemistry in the rat central nervous system by using an antibody generated against a unique sequence of the receptor protein. Specificity of the antiserum was demonstrated by immunoblot and immunocytochemistry on rat brain membranes and/or on cells transfected with cDNA encoding the different sst receptor subtypes. In rat brain sections, sst2Areceptor immunoreactivity was concentrated either in perikarya and dendrites or in axon terminals distributed throughout the neuropil. Somatodendritic labeling was most prominent in the olfactory tubercle, layers II–III of the cerebral cortex, nucleus accumbens, pyramidal cells of CA1–CA2 subfields of the hippocampus, central and cortical amygdaloid nuclei, and locus coeruleus. Labeled terminals were detected mainly in the endopiriform nucleus, deep layers of the cortex, claustrum, substantia innominata, subiculum, basolateral amygdala, medial habenula, and periaqueductal gray. Electron microscopy confirmed the association of sst2Areceptors with perikarya and dendrites in the former regions and with axon terminals in the latter. These results provide the first characterization of the cellular distribution of a somatostatin receptor in mammalian brain. The widespread distribution of the sst2Areceptor in cerebral cortex and limbic structures suggests that it is involved in the transduction of both pre- and postsynaptic effects of somatostatin on cognition, learning, and memory.
Profound Loss of Layer II Entorhinal Cortex Neurons Occurs in Very Mild Alzheimer’s Disease
Authors: Gómez-Isla Teresa , Price Joseph L. , McKeel Jr. Daniel W. , Morris John C. , Growdon John H. , Hyman Bradley T.
Published: April 2018

The entorhinal cortex (EC) plays a crucial role as a gateway connecting the neocortex and the hippocampal formation. Layer II of the EC gives rise to the perforant pathway, the major source of the excitatory input to the hippocampus, and layer IV receives a major hippocampal efferent projection. The EC is affected severely in Alzheimer disease (AD), likely contributing to memory impairment. We applied stereological principles of neuron counting to determine whether neuronal loss occurs in the EC in the very early stages of AD. We studied 20 individuals who at death had a Clinical Dementia Rating (CDR) score of 0 (cognitively normal), 0.5 (very mild), 1 (mild), or 3 (severe cognitive impairment). Lamina-specific neuronal counts were carried out on sections representing the entire EC. In the cognitively normal (CDR = 0) individuals, there were ∼650,000 neurons in layer II, 1 million neurons in layer IV, and 7 million neurons in the entire EC. The number of neurons remained constant between 60 and 90 years of age. The group with the mildest clinically detectable dementia (CDR = 0.5), all of whom had sufficient neurofibrillary tangles (NFTs) and senile plaques for the neuropathological diagnosis of AD, had 32% fewer EC neurons than controls. Decreases in individual lamina were even more dramatic, with the number of neurons in layer II decreasing by 60% and in layer IV by 40% compared with controls. In the severe dementia cases (CDR = 3), the number of neurons in layer II decreased by ∼90%, and the number of neurons in layer IV decreased by ∼70% compared with controls. Neuronal number in AD was inversely proportional to NFT formation and neuritic plaques, but was not related significantly to diffuse plaques or to total plaques. These results support the conclusion that a marked decrement of layer II neurons distinguishes even very mild AD from nondemented aging.
Immunogold Localization of the Dopamine Transporter: An Ultrastructural Study of the Rat Ventral Tegmental Area
Authors: Nirenberg Melissa J. , Chan June , Vaughan Roxanne A. , Uhl George R. , Kuhar Michael J. , Pickel Virginia M.
Published: April 2018

The dopamine transporter (DAT) plays an important role in the plasmalemmal reuptake of dopamine and, thus, in the termination of normal dopaminergic neurotransmission. DAT is also a major binding site for cocaine and other stimulants, the psychoactive effects of which are associated primarily with the inhibition of dopamine reuptake within mesocorticolimbic dopaminergic neurons. We used electron microscopy with an anti-peptide antiserum directed against the N-terminal domain of DAT to determine the subcellular localization of this transporter in the rat ventral tegmental area (VTA), the region that contains the cell bodies and dendrites of these dopaminergic neurons. We show that in the VTA, almost 95% of the DAT immunogold-labeled profiles are neuronal perikarya and dendrites, and the remainder are unmyelinated axons. Within perikarya and large proximal dendrites, almost all of the DAT immunogold particles are associated with intracellular membranes, including saccules of Golgi and cytoplasmic tubulovesicles. In contrast, within medium- to small-diameter dendrites and unmyelinated axons, most of the DAT gold particles are located on plasma membranes. In dually labeled tissue, peroxidase reaction product for the catecholamine-synthesizing enzyme tyrosine hydroxylase is present in DAT-immunoreactive profiles. These findings suggest that intermediate and distal dendrites are both the primary sites of dopamine reuptake and the principal targets of cocaine and related psychostimulants within dopaminergic neurons in the VTA.
Dysregulation of Diurnal Rhythms of Serotonin 5-HT2Cand Corticosteroid Receptor Gene Expression in the Hippocampus with Food Restriction and Glucocorticoids
Authors: Holmes Megan C. , French Karen L. , Seckl Jonathan R.
Published: April 2018

Both serotonergic dysfunction and glucocorticoid hypersecretion are implicated in affective and eating disorders. The adverse effects of serotonergic (5-HT)2Creceptor activation on mood and food intake, the antidepressant efficacy of 5-HT2receptor antagonists, and the hyperphagia observed in 5-HT2Creceptor knockout mice all suggest a key role for increased 5-HT2Creceptor-mediated neurotransmission. Glucocorticoids, however, downregulate 5-HT2Creceptor mRNA in the hippocampus, and it is unclear how increased 5-HT2Creceptor sensitivity is achieved in the presence of elevated glucocorticoid levels in depression. Here we show a monophasic diurnal rhythm of 5-HT2Creceptor mRNA expression in the rat hippocampus that parallels time-dependent variations in 5-HT2Creceptor agonist-induced behaviors in open field tests. Rats entrained to chronic food restriction show marked but intermittent corticosterone hypersecretion and maintain an unaltered 5-HT2Creceptor mRNA rhythm. The 5-HT2Creceptor mRNA rhythm, however, is suppressed by even modest constant elevations of corticosterone (adrenalectomy + pellet) or with elevated corticosterone during the daytime (8 A.M.), whereas a normal rhythm exists in animals that have the same dose of corticosterone in the evening (6 P.M.). Thus, animals showing even a transient daytime corticosterone nadir exhibit normal hippocampal 5-HT2Creceptor mRNA rhythms, even in the presence of overt corticosterone hypersecretion. Chronic food restriction also abolishes the normal diurnal variation in hippocampal glucocorticoid receptor (GR) and mineralocorticoid receptor mRNAs and produces, unusually, both elevated corticosterone and increased GR. The mismatch between elevated glucocorticoids and maintained 5-HT2Creceptor and increased GR gene expression in the hippocampus provides a new model to dissect mechanisms that may underlie affective and eating disorders.
The Monomeric G-Proteins Rac1 and/or Cdc42 Are Required for the Inhibition of Voltage-Dependent Calcium Current by Bradykinin
Authors: Wilk-Blaszczak Malgorzata A. , Singer William D. , Quill Timothy , Miller Billy , Frost Jeffrey A. , Sternweis Paul C. , Belardetti Francesco
Published: April 2018

Although regulation of voltage-dependent calcium current (ICa,V) by neurotransmitters is a ubiquitous mechanism among nerve cells, the signaling pathways involved are not well understood. We have determined previously that in a neuroblastoma-glioma hybrid cell line (NG108-15), the heterotrimeric G-protein G13mediates the inhibition ofICa,Vproduced by bradykinin (BK) via an unknown mechanism. Various reports indicate that G13can couple to RhoA, Rac1, and Cdc42, which are closely related members of the Rho family of monomeric G-proteins. We have investigated their role as signaling intermediates in the pathway used by BK to inhibitICa,V. Using immunoblot analysis and the PCR, we found evidence that RhoA, Rac1, and Cdc42 all are expressed in NG108-15 cells. Intracellularly perfused recombinant Rho-GDI (an inhibitor of guanine nucleotide exchange specific for the Rho family) attenuated the inhibition ofICa,Vby BK. These findings indicate that activation of RhoA, Rac1, or Cdc42 may be required for the response to BK. To determine whether any of these monomeric G-proteins mediate the response to BK, we have intracellularly applied blocking antibodies specific for each of the candidate proteins. Only the anti-Rac1 antibody blocked the response to BK. In parallel experiments, peptides corresponding to the C-terminal regions of Rac1 and Cdc42 blocked the same response. These data indicate a novel functional contribution of Rac1 and possibly also of Cdc42 to the inhibition ofICa,Vby neurotransmitters.
Bone Morphogenetic Proteins Induce Astroglial Differentiation of Oligodendroglial–Astroglial Progenitor Cells
Authors: Mabie P. C. , Mehler M. F. , Marmur R. , Papavasiliou A. , Song Q. , Kessler J. A.
Published: April 2018

We have used bipotent postnatal cortical oligodendroglial-astroglial progenitor cells (O-2As) to examine the role of inductive signals in astroglial lineage commitment. O-2A progenitor cells undergo progressive oligodendroglial differentiation when cultured in serum-free medium, but differentiate into astrocytes in medium supplemented with FBS. We now report that the bone morphogenetic proteins (BMPs), a major subclass of the transforming growth factor β (TGFβ) superfamily, promote the selective, dose-dependent differentiation of O-2As into astrocytes with concurrent suppression of oligodendroglial differentiation. This astroglial-inductive action is not sanctioned by other members of the TGFβ superfamily. Astroglial differentiation requires only very brief initial exposure to the BMPs and is accompanied by increased cellular survival and accelerated exit from cell cycle. Dual-label immunofluorescence microscopy documents that O-2A progenitor cells express a complement of BMP type I and type II receptor subunits required for signal transduction. Furthermore, expression of BMP2in vivoreaches maximal levels during the period of gliogenesis. These results suggest that the BMPs act as potent inductive factors in postnatal glial lineage commitment that initiate a stable program of astroglial differentiation.
Control of Action Potential-Induced Ca2+Signaling in the Soma of Hippocampal Neurons by Ca2+Release from Intracellular Stores
Authors: Jacobs Jason M. , Meyer Tobias
Published: April 2018

Stimulus-induced increases in neuronal Ca2+concentration are important signaling events for transcriptional regulation and neuronal plasticity. Electrical inputs are thought to mediate Ca2+responses in the soma by triggering action potentials, which in turn open voltage-gated Ca2+channels in the somatic plasma membrane. It is not yet known to what extent internal Ca2+amplification contributes to the somatic Ca2+responses. Here we used fluorescent Ca2+measurements in cultured hippocampal neurons and report that the amplitude of the somatic Ca2+increase triggered by field stimulation is independent of the extracellular Ca2+concentration as long as the concentration is greater than 50 μm. Furthermore, significantly more La3+has to be added extracellularly for blocking Ca2+responses, as predicted from the reported La3+dependence of voltage-gated Ca2+channels. These measurements suggest that field stimulation-induced somatic Ca2+responses in hippocampal neurons are largely attributable to Ca2+release from intracellular stores. Only a small number of Ca2+ions have to enter across the plasma membrane for this intracellular Ca2+amplification process to occur. Rapid fluorescence-imaging measurements showed that the internal Ca2+amplification occurs over 10–15 msec and linearly increases intracellular Ca2+concentrations for up to 40 action potentials. At a fixed number of field pulses, frequencies of 40 Hz were optimal for somatic Ca2+increases. Our studies suggest that the opening of intracellular Ca2+release channels plays a crucial part in shaping the action potential-induced neuronal Ca2+response.
Reduction of CuZn-Superoxide Dismutase Activity Exacerbates Neuronal Cell Injury and Edema Formation after Transient Focal Cerebral Ischemia
Authors: Kondo Takeo , Reaume Andrew G. , Huang Ting-Ting , Carlson Elaine , Murakami Kensuke , Chen Sylvia F. , Hoffman Eric K. , Scott Richard W. , Epstein Charles J. , Chan Pak H.
Published: April 2018

Apoptotic neuronal cell death has recently been associated with the development of infarction after cerebral ischemia. In a variety of studies, CuZn-superoxide dismutase (CuZn-SOD) has been shown to protect the brain from ischemic injury. A possible role for CuZn-SOD-related modulation of neuronal viability is suggested by the finding that CuZn-SOD inhibits apoptotic neuronal cell death in response to some forms of cellular damage. We evaluated this possibility in the model of transient focal cerebral ischemia in mice bearing a disruption of the CuZn-SOD gene (Sod1). Homozygous mutant (Sod1−/−) mice had no detectable CuZn-SOD activity, and heterozygous mutants (Sod1+/−) showed a 50% decrease compared with wild-type mice.Sod1−/− mice showed a high level of blood–brain barrier disruption soon after 1 hr of middle cerebral artery occlusion and 100% mortality at 24 hr after ischemia.Sod1+/− mice showed 30% mortality at 24 hr after ischemia, and neurological deficits were exacerbated compared with wild-type controls. TheSod1+/− animals also had increased infarct volume and brain swelling, accompanied by increased apoptotic neuronal cell death as indicated by thein situnick-end labeling technique to detect DNA fragmentation and morphological criteria. These results suggest that oxygen-free radicals, especially superoxide anions, are an important factor for the development of infarction by brain edema formation and apoptotic neuronal cell death after focal cerebral ischemia and reperfusion.
Upregulation of the Endosomal-Lysosomal Pathway in the Trembler-J Neuropathy
Authors: Notterpek Lucia , Shooter Eric M. , Snipes G. Jackson
Published: April 2018

A nonconservative leucine to proline mutation in peripheral myelin protein 22 (PMP22) causes the Trembler-J (TrJ) neuropathy in mice and humans. The expression levels and localization of the PMP22 protein in theTrJmouse have not been previously determined. The aim of our studies was to reevaluate the extent of myelin deficit in genotyped heterozygous and homozygous animals and to examine how theTrJmutation alters the normalin vivopost-translational processing of PMP22. Morphological studies show evidence for primary dysmyelination and myelin instability in affected animals. As expected, Western blot analysis indicates that in adult heterozygousTrJanimals, the level of PMP22 is markedly decreased, similar to myelin basic protein and protein zero, whereas myelin-associated glycoprotein is largely unaffected. The decrease in myelin protein expression is associated with an increase in lysosomal biogenesis, suggestive of augmented endocytosis or autophagy. Double-immunolabeling experiments show the accumulation of PMP22 in endosomal/lysosomal structures ofTrJSchwann cells, and chloroquine treatment of nerve segments indicates that the degradation of protein zero, PMP22, and myelin basic protein is augmented inTrJnerves. These studies suggest that theTrJmutation alters myelin stability and that the mutant protein is likely degraded via the lysosomal pathway.
Norepinephrine Facilitates the Development of the Murine Sweat Response But Is Not Essential
Authors: Tsahai Tafari A. , Thomas Steven A. , Palmiter Richard D.
Published: April 2018

During development, the sympathetic neurons innervating sweat glands undergo a neurotransmitter switch from noradrenergic to cholinergic between postnatal day (P) 4, when the sympathetic neurons first contact the sweat glands, and P21. Severalin vitroexperiments suggest that norepinephrine (NE), produced by sympathetic neurons, stimulates sweat glands to produce a factor that then induces the phenotypic switch. We tested this hypothesisin vivousing dopamine β-hydroxylase-deficient mice (DBH −/−), which are unable to synthesize NE and epinephrine, and tyrosine hydroxylase-deficient mice (TH −/−), which are unable to synthesize any catecholamines. The cholinergic agonist pilocarpine and electrostimulation of the sciatic nerve both elicited a sweat response in adult DBH −/− mice that was indistinguishable from the response of controls, and the cholinergic antagonist atropine effectively blocked these responses. We did note, however, a 1- to 2-week delay in the acquisition of the sweat response in DBH −/− mice. Although diminished in magnitude, a sweat response to pilocarpine was also noted in TH −/− mice at P21. Immunohistochemistry demonstrated that TH and vasoactive intestinal peptide were detectable at P14 and increased to adult levels by P21 in DBH +/− and DBH −/− mice. These observations indicate that NE is not essential for the acquisition of the cholinergic phenotype, but it may facilitate its postnatal development.
Selective Expression of Dopamine D3Receptor mRNA in Proliferative Zones during Embryonic Development of the Rat Brain
Authors: Diaz Jorge , Ridray Sophie , Mignon Virginie , Griffon Nathalie , Schwartz Jean-Charles , Sokoloff Pierre
Published: April 2018

We studied byin situhybridization histochemistry the expression of D3receptor (D3R) mRNA at various stages of rat brain development. The first expression of D3R mRNA was detected at embryonic day 14 (E14) in the striatal and rhinencephalic neuroepithelia and throughout the tectal neuroepithelium. From E16 to E19 D3R mRNA expression extended along a rostrocaudal axis to additional proliferative ventricular zones of the basal forebrain, including the neuroepithelia of the olfactory bulb, nucleus accumbens, septum, and amygdala, whereas D1and D2receptor (D1R and D2R) mRNAs were expressed predominantly by migrating neuroblasts and/or differentiating striatal neurons. Only a few neuroblasts, migrating in the lateral cortical stream or developing as cerebellar Purkinje cells, expressed D3R mRNA from E18. At birth D3R expression mRNA appeared in differentiating neuronal fields of the nucleus accumbens and medial mamillary body primordia and on P5 reached a distribution similar to that found in adult. In addition, a transient upregulation was detected on P5 in the medial mamillary bodies, parietofrontal cortex, and olfactory tubercle. In the adult brain D3R gene expression continued in the striatal proliferative subventricular zone. The late expression D3R mRNA in neurons, after achievement of dopamine innervation, supports the existence of a regulating factor released from dopamine neurons, as suggested by denervation studies in the adult. The sustained and abundant D3R gene expression, predominantly in germinative neuroepithelial zones actively involved in neurogenesis of most basal forebrain structures, supports the hypothesis of a neurogenetic but minor morphogenetic modulatory role for the D3R during CNS development.
The Fusiform Face Area: A Module in Human Extrastriate Cortex Specialized for Face Perception
Authors: Kanwisher Nancy , McDermott Josh , Chun Marvin M.
Published: April 2018

Using functional magnetic resonance imaging (fMRI), we found an area in the fusiform gyrus in 12 of the 15 subjects tested that was significantly more active when the subjects viewed faces than when they viewed assorted common objects. This face activation was used to define a specific region of interest individually for each subject, within which several new tests of face specificity were run. In each of five subjects tested, the predefined candidate “face area” also responded significantly more strongly to passive viewing of (1) intact than scrambled two-tone faces, (2) full front-view face photos than front-view photos of houses, and (in a different set of five subjects) (3) three-quarter-view face photos (with hair concealed) than photos of human hands; it also responded more strongly during (4) a consecutive matching task performed on three-quarter-view faces versus hands. Our technique of running multiple tests applied to the same region defined functionally within individual subjects provides a solution to two common problems in functional imaging: (1) the requirement to correct for multiple statistical comparisons and (2) the inevitable ambiguity in the interpretation of any study in which only two or three conditions are compared. Our data allow us to reject alternative accounts of the function of the fusiform face area (area “FF”) that appeal to visual attention, subordinate-level classification, or general processing of any animate or human forms, demonstrating that this region isselectivelyinvolved in the perception of faces.
How Is a Sensory Map Read Out? Effects of Microstimulation in Visual Area MT on Saccades and Smooth Pursuit Eye Movements
Authors: Groh Jennifer M. , Born Richard T. , Newsome William T.
Published: April 2018

To generate behavioral responses based on sensory input, motor areas of the brain must interpret, or “read out,” signals from sensory maps. Our experiments tested several algorithms for how the motor systems for smooth pursuit and saccadic eye movements might extract a usable signal of target velocity from the distributed representation of velocity in the middle temporal visual area (MT or V5). Using microstimulation, we attempted to manipulate the velocity information within MT while monkeys tracked a moving visual stimulus. We examined the effects of the microstimulation on smooth pursuit and on the compensation for target velocity shown by saccadic eye movements. Microstimulation could alter both the speed and direction of the motion estimates of both types of eye movements and could also cause monkeys to generate pursuit even when the visual target was actually stationary. The pattern of alterations suggests that microstimulation can introduce an additional velocity signal into MT and that the pursuit and saccadic systems usually compute a vector average of the visually evoked and microstimulation-induced velocity signals (pursuit, 55 of 122 experiments; saccades, 70 of 122). Microstimulation effects in a few experiments were consistent with vector summation of these two signals (pursuit, 6 of 122; saccades, 2 of 122). In the remainder of the experiments, microstimulation caused either an apparent impairment in motion processing (pursuit, 47 of 122; saccades, 41 of 122) or had no effect (pursuit, 14 of 122; saccades, 9 of 122). Within individual experiments, the effects on pursuit and saccades were usually similar, but the occasional striking exception suggests that the two eye movement systems may perform motion computations somewhat independently.
Vasopressin/Serotonin Interactions in the Anterior Hypothalamus Control Aggressive Behavior in Golden Hamsters
Authors: Ferris Craig F. , Melloni Jr Richard H. , Koppel Gary , Perry Kenneth W. , Fuller Ray W. , Delville Yvon
Published: April 2018

Studies in several species of rodents show that arginine vasopressin (AVP) acting through a V1Areceptor facilitates offensive aggression, i.e., the initiation of attacks and bites, whereas serotonin (5-HT) acting through a 5-HT1Breceptor inhibits aggressive responding. One area of the CNS that seems critical for the organization of aggressive behavior is the basolateral hypothalamus, particularly the anterior hypothalamic region. The present studies examine the neuroanatomical and neurochemical interaction between AVP and 5-HT at the level of the anterior hypothalamus (AH) in the control of offensive aggression in Syrian golden hamsters. First, specific V1Aand 5-HT1Bbinding sites in the AH are shown byin vitroreceptor autoradiography. The binding for each neurotransmitter colocalizes with a dense field of immunoreactive AVP and 5-HT fibers and putative terminals. Putative 5-HT synapses on AVP neurons in the area of the AH are identified by double-staining immunocytochemistry and laser scanning confocal microscopy. These morphological data predispose a functional interaction between AVP and 5-HT at the level of the AH. When tested for offensive aggression in a resident/intruder paradigm, resident hamsters treated with fluoxetine, a selective 5-HT reuptake inhibitor, have significantly longer latencies to bite and bite fewer times than vehicle-treated controls. Conversely, AVP microinjections into the AH significantly shorten the latency to bite and increase biting attacks. The action of microinjected AVP to increase offensive aggression is blocked by the pretreatment of hamsters with fluoxetine. These data suggest that 5-HT inhibits fighting, in part, by antagonizing the aggression-promoting action of the AVP system.
Firing Properties of Head Direction Cells in the Rat Anterior Thalamic Nucleus: Dependence on Vestibular Input
Authors: Stackman Robert W. , Taube Jeffrey S.
Published: April 2018

Vestibular information influences spatial orientation and navigation in laboratory animals and humans. Neurons within the rat anterior thalamus encode the directional heading of the animal in absolute space. These neurons, referred to as head direction (HD) cells, fire selectively when the rat points its head in a specific direction in the horizontal plane with respect to the external laboratory reference frame. HD cells are thought to represent an essential component of a neural network that processes allocentric spatial information. The functional properties of HD cells may be dependent on vestibular input. Here, anterior thalamic HD cells were recorded before and after sodium arsanilate-induced vestibular system lesion. Vestibular lesions abolished the directional firing properties of HD cells. The time course of disruption in the directional firing properties paralleled the loss of vestibular function. Arsanilate-treated rats exhibited only minor changes in locomotor behavior, which were unlikely to account for the loss of direction-specific firing. Vestibular lesions also disrupted the influence of angular head velocity on anterior thalamic single-unit firing rates. Finally, a subset of anterior thalamic neurons recorded from vestibular-lesioned rats exhibited a pattern of intermittent firing bursts that were distinctly unrelated to HD. This novel anterior thalamic firing pattern has not been encountered in any vestibular-intact rat. These data suggest that: (1) the neural code for directional bearing is critically dependent on vestibular information; and (2) this loss of HD cell information may represent a neurobiological mechanism to account for the orientation and navigational deficits observed after vestibular dysfunction.
The Low-Affinity Neurotrophin Receptor p75 Regulates the Function But Not the Selective Survival of Specific Subpopulations of Sensory Neurons
Authors: Stucky Cheryl L. , Koltzenburg Martin
Published: April 2018

Mice with a targeted deletion of the low-affinity neurotrophin receptor p75 (p75−/−) exhibit a 50% loss of large- and small-diameter sensory neurons in the dorsal root ganglion. Using neurophysiological recording techniques, we now show that p75 is not required for the survival of specific, functionally defined subpopulations of sensory neurons. Rather, p75−/− mice exhibit losses of neurons that subserve nociceptive as well as non-nociceptive functions. The receptive properties of large myelinated afferent fibers were normal in p75−/− mice. However, the receptive properties of subpopulations of afferent fibers with thin myelinated or unmyelinated axons were strikingly impaired in mice lacking p75. Furthermore, the presence of p75 is required for normal mechanotransduction in C fibers and D-hair receptors and normal heat sensitivity in A-fiber nociceptors.