Cholinergic, Glutamatergic, and GABAergic Neurons of the Pedunculopontine Tegmental Nucleus Have Distinct Effects on Sleep/Wake Behavior in Mice.

PubMed

Kroeger, Daniel; Ferrari, Loris L; Petit, Gaetan; Mahoney, Carrie E; Fuller, Patrick M; Arrigoni, Elda; Scammell, Thomas E

2017-02-01

The pedunculopontine tegmental (PPT) nucleus has long been implicated in the regulation of cortical activity and behavioral states, including rapid eye-movement (REM) sleep. For example, electrical stimulation of the PPT region during sleep leads to rapid awakening, whereas lesions of the PPT in cats reduce REM sleep. Though these effects have been linked with the activity of cholinergic PPT neurons, the PPT also includes intermingled glutamatergic and GABAergic cell populations, and the precise roles of cholinergic, glutamatergic, and GABAergic PPT cell groups in regulating cortical activity and behavioral state remain unknown. Using a chemogenetic approach in three Cre-driver mouse lines, we found that selective activation of glutamatergic PPT neurons induced prolonged cortical activation and behavioral wakefulness, whereas inhibition reduced wakefulness and increased non-REM (NREM) sleep. Activation of cholinergic PPT neurons suppressed lower-frequency electroencephalogram rhythms during NREM sleep. Last, activation of GABAergic PPT neurons slightly reduced REM sleep. These findings reveal that glutamatergic, cholinergic, and GABAergic PPT neurons differentially influence cortical activity and sleep/wake states. More than 40 million Americans suffer from chronic sleep disruption, and the development of effective treatments requires a more detailed understanding of the neuronal mechanisms controlling sleep and arousal. The pedunculopontine tegmental (PPT) nucleus has long been considered a key site for regulating wakefulness and REM sleep. This is mainly because of the cholinergic neurons contained in the PPT nucleus. However, the PPT nucleus also contains glutamatergic and GABAergic neurons that likely contribute to the regulation of cortical activity and sleep-wake states. The chemogenetic experiments in the present study reveal that cholinergic, glutamatergic, and GABAergic PPT neurons each have distinct effects on sleep/wake behavior, improving our understanding of how the PPT nucleus regulates cortical activity and behavioral states. Copyright © 2017 the authors 0270-6474/17/371352-15$15.00/0.

VAV-1 acts in a single interneuron to inhibit motor circuit activity in Caenorhabditis elegans.

PubMed

Fry, Amanda L; Laboy, Jocelyn T; Norman, Kenneth R

2014-11-21

The complex molecular and cellular mechanisms underlying neuronal control of animal movement are not well understood. Locomotion of Caenorhabditis elegans is mediated by a neuronal circuit that produces coordinated sinusoidal movement. Here we utilize this simple, yet elegant, behaviour to show that VAV-1, a conserved guanine nucleotide exchange factor for Rho-family GTPases, negatively regulates motor circuit activity and the rate of locomotion. While vav-1 is expressed in a small subset of neurons, we find that VAV-1 function is required in a single interneuron, ALA, to regulate motor neuron circuit activity. Furthermore, we show by genetic and optogenetic manipulation of ALA that VAV-1 is required for the excitation and activation of this neuron. We find that ALA signalling inhibits command interneuron activity by abrogating excitatory signalling in the command interneurons, which is responsible for promoting motor neuron circuit activity. Together, our data describe a novel neuromodulatory role for VAV-1-dependent signalling in the regulation of motor circuit activity and locomotion.

Regulation of persistent sodium currents by glycogen synthase kinase 3 encodes daily rhythms of neuronal excitability

NASA Astrophysics Data System (ADS)

Paul, Jodi R.; Dewoskin, Daniel; McMeekin, Laura J.; Cowell, Rita M.; Forger, Daniel B.; Gamble, Karen L.

2016-11-01

How neurons encode intracellular biochemical signalling cascades into electrical signals is not fully understood. Neurons in the central circadian clock in mammals provide a model system to investigate electrical encoding of biochemical timing signals. Here, using experimental and modelling approaches, we show how the activation of glycogen synthase kinase 3 (GSK3) contributes to neuronal excitability through regulation of the persistent sodium current (INaP). INaP exhibits a day/night difference in peak magnitude and is regulated by GSK3. Using mathematical modelling, we predict and confirm that GSK3 activation of INaP affects the action potential afterhyperpolarization, which increases the spontaneous firing rate without affecting the resting membrane potential. Together, these results demonstrate a crucial link between the molecular circadian clock and electrical activity, providing examples of kinase regulation of electrical activity and the propagation of intracellular signals in neuronal networks.

GABA-CREB signalling regulates maturation and survival of newly generated neurons in the adult hippocampus

PubMed Central

Jagasia, Ravi; Steib, Kathrin; Englberger, Elisabeth; Herold, Sabine; Faus-Kessler, Theresa; Saxe, Michael; Gage, Fred H.; Song, Hongjun; Lie, D. Chichung

2009-01-01

Survival and integration of new neurons in the hippocampal circuit are rate-limiting steps in adult hippocampal neurogenesis. Neuronal network activity is a major regulator of these processes, yet little is known about the respective downstream signalling pathways. Here, we investigate the role of CREB signalling in adult hippocampal neurogenesis. CREB is activated in new granule neurons during a distinct developmental period. Loss of CREB function in a cell-autonomous fashion impairs dendritic development, decreases the expression of the neurogenic transcription factor NeuroD and of the neuronal microtubule associated protein, DCX, and compromises the survival of newborn neurons. In addition, GABA-mediated excitation regulates CREB activation at early developmental stages. Importantly, developmental defects following loss of GABA-mediated excitation can be compensated by enhanced CREB signalling. These results indicate that CREB signalling is a central pathway in adult hippocampal neurogenesis, regulating the development and survival of new hippocampal neurons downstream of GABA-mediated excitation. PMID:19553437

Network feedback regulates motor output across a range of modulatory neuron activity.

PubMed

Spencer, Robert M; Blitz, Dawn M

2016-06-01

Modulatory projection neurons alter network neuron synaptic and intrinsic properties to elicit multiple different outputs. Sensory and other inputs elicit a range of modulatory neuron activity that is further shaped by network feedback, yet little is known regarding how the impact of network feedback on modulatory neurons regulates network output across a physiological range of modulatory neuron activity. Identified network neurons, a fully described connectome, and a well-characterized, identified modulatory projection neuron enabled us to address this issue in the crab (Cancer borealis) stomatogastric nervous system. The modulatory neuron modulatory commissural neuron 1 (MCN1) activates and modulates two networks that generate rhythms via different cellular mechanisms and at distinct frequencies. MCN1 is activated at rates of 5-35 Hz in vivo and in vitro. Additionally, network feedback elicits MCN1 activity time-locked to motor activity. We asked how network activation, rhythm speed, and neuron activity levels are regulated by the presence or absence of network feedback across a physiological range of MCN1 activity rates. There were both similarities and differences in responses of the two networks to MCN1 activity. Many parameters in both networks were sensitive to network feedback effects on MCN1 activity. However, for most parameters, MCN1 activity rate did not determine the extent to which network output was altered by the addition of network feedback. These data demonstrate that the influence of network feedback on modulatory neuron activity is an important determinant of network output and feedback can be effective in shaping network output regardless of the extent of network modulation. Copyright © 2016 the American Physiological Society.

Shp2 in Forebrain Neurons Regulates Synaptic Plasticity, Locomotion, and Memory Formation in Mice

PubMed Central

Kusakari, Shinya; Saitow, Fumihito; Ago, Yukio; Shibasaki, Koji; Sato-Hashimoto, Miho; Matsuzaki, Yasunori; Kotani, Takenori; Murata, Yoji; Hirai, Hirokazu; Matsuda, Toshio; Suzuki, Hidenori

2015-01-01

Shp2 (Src homology 2 domain-containing protein tyrosine phosphatase 2) regulates neural cell differentiation. It is also expressed in postmitotic neurons, however, and mutations of Shp2 are associated with clinical syndromes characterized by mental retardation. Here we show that conditional-knockout (cKO) mice lacking Shp2 specifically in postmitotic forebrain neurons manifest abnormal behavior, including hyperactivity. Novelty-induced expression of immediate-early genes and activation of extracellular-signal-regulated kinase (Erk) were attenuated in the cerebral cortex and hippocampus of Shp2 cKO mice, suggestive of reduced neuronal activity. In contrast, ablation of Shp2 enhanced high-K+-induced Erk activation in both cultured cortical neurons and synaptosomes, whereas it inhibited that induced by brain-derived growth factor in cultured neurons. Posttetanic potentiation and paired-pulse facilitation were attenuated and enhanced, respectively, in hippocampal slices from Shp2 cKO mice. The mutant mice also manifested transient impairment of memory formation in the Morris water maze. Our data suggest that Shp2 contributes to regulation of Erk activation and synaptic plasticity in postmitotic forebrain neurons and thereby controls locomotor activity and memory formation. PMID:25713104

Neurons for hunger and thirst transmit a negative-valence teaching signal.

PubMed

Betley, J Nicholas; Xu, Shengjin; Cao, Zhen Fang Huang; Gong, Rong; Magnus, Christopher J; Yu, Yang; Sternson, Scott M

2015-05-14

Homeostasis is a biological principle for regulation of essential physiological parameters within a set range. Behavioural responses due to deviation from homeostasis are critical for survival, but motivational processes engaged by physiological need states are incompletely understood. We examined motivational characteristics of two separate neuron populations that regulate energy and fluid homeostasis by using cell-type-specific activity manipulations in mice. We found that starvation-sensitive AGRP neurons exhibit properties consistent with a negative-valence teaching signal. Mice avoided activation of AGRP neurons, indicating that AGRP neuron activity has negative valence. AGRP neuron inhibition conditioned preference for flavours and places. Correspondingly, deep-brain calcium imaging revealed that AGRP neuron activity rapidly reduced in response to food-related cues. Complementary experiments activating thirst-promoting neurons also conditioned avoidance. Therefore, these need-sensing neurons condition preference for environmental cues associated with nutrient or water ingestion, which is learned through reduction of negative-valence signals during restoration of homeostasis.

Action of Neurotransmitter: A Key to Unlock the AgRP Neuron Feeding Circuit

PubMed Central

Liu, Tiemin; Wang, Qian; Berglund, Eric D.; Tong, Qingchun

2013-01-01

The current obesity epidemic and lack of efficient therapeutics demand a clear understanding of the mechanism underlying body weight regulation. Despite intensive research focus on obesity pathogenesis, an effective therapeutic strategy to treat and cure obesity is still lacking. Exciting studies in last decades have established the importance of hypothalamic agouti-related protein-expressing neurons (AgRP neurons) in the regulation of body weight homeostasis. AgRP neurons are both required and sufficient for feeding regulation. The activity of AgRP neurons is intricately regulated by nutritional hormones as well as synaptic inputs from upstream neurons. Changes in AgRP neuron activity lead to alterations in the release of mediators, including neuropeptides Neuropeptide Y (NPY) and AgRP, and fast-acting neurotransmitter GABA. Recent studies based on mouse genetics, novel optogenetics, and designer receptor exclusively activated by designer drugs have identified a critical role for GABA release from AgRP neurons in the parabrachial nucleus and paraventricular hypothalamus in feeding control. This review will summarize recent findings about AgRP neuron-mediated control of feeding circuits with a focus on the role of neurotransmitters. Given the limited knowledge on feeding regulation, understanding the action of neurotransmitters may be a key to unlock neurocircuitry that governs feeding. PMID:23346045

Neuron class-specific requirements for Fragile X Mental Retardation Protein in critical period development of calcium signaling in learning and memory circuitry.

PubMed

Doll, Caleb A; Broadie, Kendal

2016-05-01

Neural circuit optimization occurs through sensory activity-dependent mechanisms that refine synaptic connectivity and information processing during early-use developmental critical periods. Fragile X Mental Retardation Protein (FMRP), the gene product lost in Fragile X syndrome (FXS), acts as an activity sensor during critical period development, both as an RNA-binding translation regulator and channel-binding excitability regulator. Here, we employ a Drosophila FXS disease model to assay calcium signaling dynamics with a targeted transgenic GCaMP reporter during critical period development of the mushroom body (MB) learning/memory circuit. We find FMRP regulates depolarization-induced calcium signaling in a neuron-specific manner within this circuit, suppressing activity-dependent calcium transients in excitatory cholinergic MB input projection neurons and enhancing calcium signals in inhibitory GABAergic MB output neurons. Both changes are restricted to the developmental critical period and rectified at maturity. Importantly, conditional genetic (dfmr1) rescue of null mutants during the critical period corrects calcium signaling defects in both neuron classes, indicating a temporally restricted FMRP requirement. Likewise, conditional dfmr1 knockdown (RNAi) during the critical period replicates constitutive null mutant defects in both neuron classes, confirming cell-autonomous requirements for FMRP in developmental regulation of calcium signaling dynamics. Optogenetic stimulation during the critical period enhances depolarization-induced calcium signaling in both neuron classes, but this developmental change is eliminated in dfmr1 null mutants, indicating the activity-dependent regulation requires FMRP. These results show FMRP shapes neuron class-specific calcium signaling in excitatory vs. inhibitory neurons in developing learning/memory circuitry, and that FMRP mediates activity-dependent regulation of calcium signaling specifically during the early-use critical period. Copyright © 2016 Elsevier Inc. All rights reserved.

Fibroblast growth factor homologous factor 1 interacts with NEMO to regulate NF-κB signaling in neurons.

PubMed

König, Hans-Georg; Fenner, Beau J; Byrne, Jennifer C; Schwamborn, Robert F; Bernas, Tytus; Jefferies, Caroline A; Prehn, Jochen H M

2012-12-15

Neuronal survival and plasticity critically depend on constitutive activity of the transcription factor nuclear factor-κB (NF-κB). We here describe a role for a small intracellular fibroblast growth factor homologue, the fibroblast growth factor homologous factor 1 (FHF1/FGF12), in the regulation of NF-κB activity in mature neurons. FHFs have previously been described to control neuronal excitability, and mutations in FHF isoforms give rise to a form of progressive spinocerebellar ataxia. Using a protein-array approach, we identified FHF1b as a novel interactor of the canonical NF-κB modulator IKKγ/NEMO. Co-immunoprecipitation, pull-down and GAL4-reporter experiments, as well as proximity ligation assays, confirmed the interaction of FHF1 and NEMO and demonstrated that a major site of interaction occurred within the axon initial segment. Fhf1 gene silencing strongly activated neuronal NF-κB activity and increased neurite lengths, branching patterns and spine counts in mature cortical neurons. The effects of FHF1 on neuronal NF-κB activity and morphology required the presence of NEMO. Our results imply that FHF1 negatively regulates the constitutive NF-κB activity in neurons.

Neuronal activity determines distinct gliotransmitter release from a single astrocyte

PubMed Central

Covelo, Ana

2018-01-01

Accumulating evidence indicates that astrocytes are actively involved in brain function by regulating synaptic activity and plasticity. Different gliotransmitters, such as glutamate, ATP, GABA or D-serine, released form astrocytes have been shown to induce different forms of synaptic regulation. However, whether a single astrocyte may release different gliotransmitters is unknown. Here we show that mouse hippocampal astrocytes activated by endogenous (neuron-released endocannabinoids or GABA) or exogenous (single astrocyte Ca2+ uncaging) stimuli modulate putative single CA3-CA1 hippocampal synapses. The astrocyte-mediated synaptic modulation was biphasic and consisted of an initial glutamate-mediated potentiation followed by a purinergic-mediated depression of neurotransmitter release. The temporal dynamic properties of this biphasic synaptic regulation depended on the firing frequency and duration of the neuronal activity that stimulated astrocytes. Present results indicate that single astrocytes can decode neuronal activity and, in response, release distinct gliotransmitters to differentially regulate neurotransmission at putative single synapses. PMID:29380725

Genetic Feedback Regulation of Frontal Cortical Neuronal Ensembles Through Activity-Dependent Arc Expression and Dopaminergic Input.

PubMed

Mastwal, Surjeet; Cao, Vania; Wang, Kuan Hong

2016-01-01

Mental functions involve coordinated activities of specific neuronal ensembles that are embedded in complex brain circuits. Aberrant neuronal ensemble dynamics is thought to form the neurobiological basis of mental disorders. A major challenge in mental health research is to identify these cellular ensembles and determine what molecular mechanisms constrain their emergence and consolidation during development and learning. Here, we provide a perspective based on recent studies that use activity-dependent gene Arc/Arg3.1 as a cellular marker to identify neuronal ensembles and a molecular probe to modulate circuit functions. These studies have demonstrated that the transcription of Arc is activated in selective groups of frontal cortical neurons in response to specific behavioral tasks. Arc expression regulates the persistent firing of individual neurons and predicts the consolidation of neuronal ensembles during repeated learning. Therefore, the Arc pathway represents a prototypical example of activity-dependent genetic feedback regulation of neuronal ensembles. The activation of this pathway in the frontal cortex starts during early postnatal development and requires dopaminergic (DA) input. Conversely, genetic disruption of Arc leads to a hypoactive mesofrontal dopamine circuit and its related cognitive deficit. This mutual interaction suggests an auto-regulatory mechanism to amplify the impact of neuromodulators and activity-regulated genes during postnatal development. Such a mechanism may contribute to the association of mutations in dopamine and Arc pathways with neurodevelopmental psychiatric disorders. As the mesofrontal dopamine circuit shows extensive activity-dependent developmental plasticity, activity-guided modulation of DA projections or Arc ensembles during development may help to repair circuit deficits related to neuropsychiatric disorders.

Amyloid precursor protein controls cholesterol turnover needed for neuronal activity

PubMed Central

Pierrot, Nathalie; Tyteca, Donatienne; D'auria, Ludovic; Dewachter, Ilse; Gailly, Philippe; Hendrickx, Aurélie; Tasiaux, Bernadette; Haylani, Laetitia El; Muls, Nathalie; N'Kuli, Francisca; Laquerrière, Annie; Demoulin, Jean-Baptiste; Campion, Dominique; Brion, Jean-Pierre; Courtoy, Pierre J; Kienlen-Campard, Pascal; Octave, Jean-Noël

2013-01-01

Perturbation of lipid metabolism favours progression of Alzheimer disease, in which processing of Amyloid Precursor Protein (APP) has important implications. APP cleavage is tightly regulated by cholesterol and APP fragments regulate lipid homeostasis. Here, we investigated whether up or down regulation of full-length APP expression affected neuronal lipid metabolism. Expression of APP decreased HMG-CoA reductase (HMGCR)-mediated cholesterol biosynthesis and SREBP mRNA levels, while its down regulation had opposite effects. APP and SREBP1 co-immunoprecipitated and co-localized in the Golgi. This interaction prevented Site-2 protease-mediated processing of SREBP1, leading to inhibition of transcription of its target genes. A GXXXG motif in APP sequence was critical for regulation of HMGCR expression. In astrocytes, APP and SREBP1 did not interact nor did APP affect cholesterol biosynthesis. Neuronal expression of APP decreased both HMGCR and cholesterol 24-hydroxylase mRNA levels and consequently cholesterol turnover, leading to inhibition of neuronal activity, which was rescued by geranylgeraniol, generated in the mevalonate pathway, in both APP expressing and mevastatin treated neurons. We conclude that APP controls cholesterol turnover needed for neuronal activity. PMID:23554170

Aberrant neuronal activity-induced signaling and gene expression in a mouse model of RASopathy

PubMed Central

Nakhaei-Rad, Saeideh; Montenegro-Venegas, Carolina; Pina-Fernández, Eneko; Marini, Claudia; Santos, Monica; Ahmadian, Mohammad R.; Stork, Oliver; Zenker, Martin

2017-01-01

Noonan syndrome (NS) is characterized by reduced growth, craniofacial abnormalities, congenital heart defects, and variable cognitive deficits. NS belongs to the RASopathies, genetic conditions linked to mutations in components and regulators of the Ras signaling pathway. Approximately 50% of NS cases are caused by mutations in PTPN11. However, the molecular mechanisms underlying cognitive impairments in NS patients are still poorly understood. Here, we report the generation and characterization of a new conditional mouse strain that expresses the overactive Ptpn11D61Y allele only in the forebrain. Unlike mice with a global expression of this mutation, this strain is viable and without severe systemic phenotype, but shows lower exploratory activity and reduced memory specificity, which is in line with a causal role of disturbed neuronal Ptpn11 signaling in the development of NS-linked cognitive deficits. To explore the underlying mechanisms we investigated the neuronal activity-regulated Ras signaling in brains and neuronal cultures derived from this model. We observed an altered surface expression and trafficking of synaptic glutamate receptors, which are crucial for hippocampal neuronal plasticity. Furthermore, we show that the neuronal activity-induced ERK signaling, as well as the consecutive regulation of gene expression are strongly perturbed. Microarray-based hippocampal gene expression profiling revealed profound differences in the basal state and upon stimulation of neuronal activity. The neuronal activity-dependent gene regulation was strongly attenuated in Ptpn11D61Y neurons. In silico analysis of functional networks revealed changes in the cellular signaling beyond the dysregulation of Ras/MAPK signaling that is nearly exclusively discussed in the context of NS at present. Importantly, changes in PI3K/AKT/mTOR and JAK/STAT signaling were experimentally confirmed. In summary, this study uncovers aberrant neuronal activity-induced signaling and regulation of gene expression in Ptpn11D61Y mice and suggests that these deficits contribute to the pathophysiology of cognitive impairments in NS. PMID:28346493

ADP-ribosylation Factor 6 (ARF6) Bidirectionally Regulates Dendritic Spine Formation Depending on Neuronal Maturation and Activity*

PubMed Central

Kim, Yoonju; Lee, Sang-Eun; Park, Joohyun; Kim, Minhyung; Lee, Boyoon; Hwang, Daehee; Chang, Sunghoe

2015-01-01

Recent studies have reported conflicting results regarding the role of ARF6 in dendritic spine development, but no clear answer for the controversy has been suggested. We found that ADP-ribosylation factor 6 (ARF6) either positively or negatively regulates dendritic spine formation depending on neuronal maturation and activity. ARF6 activation increased the spine formation in developing neurons, whereas it decreased spine density in mature neurons. Genome-wide microarray analysis revealed that ARF6 activation in each stage leads to opposite patterns of expression of a subset of genes that are involved in neuronal morphology. ARF6-mediated Rac1 activation via the phospholipase D pathway is the coincident factor in both stages, but the antagonistic RhoA pathway becomes involved in the mature stage. Furthermore, blocking neuronal activity in developing neurons using tetrodotoxin or enhancing the activity in mature neurons using picrotoxin or chemical long term potentiation reversed the effect of ARF6 on each stage. Thus, activity-dependent dynamic changes in ARF6-mediated spine structures may play a role in structural plasticity of mature neurons. PMID:25605715

The novel gene tank, a tumor suppressor homolog, regulates ethanol sensitivity in Drosophila.

PubMed

Devineni, Anita V; Eddison, Mark; Heberlein, Ulrike

2013-05-08

In both mammalian and insect models of ethanol intoxication, high doses of ethanol induce motor impairment and eventually sedation. Sensitivity to the sedative effects of ethanol is inversely correlated with risk for alcoholism. However, the genes regulating ethanol sensitivity are largely unknown. Based on a previous genetic screen in Drosophila for ethanol sedation mutants, we identified a novel gene, tank (CG15626), the homolog of the mammalian tumor suppressor EI24/PIG8, which has a strong role in regulating ethanol sedation sensitivity. Genetic and behavioral analyses revealed that tank acts in the adult nervous system to promote ethanol sensitivity. We localized the function of tank in regulating ethanol sensitivity to neurons within the pars intercerebralis that have not been implicated previously in ethanol responses. We show that acutely manipulating the activity of all tank-expressing neurons, or of pars intercerebralis neurons in particular, alters ethanol sensitivity in a sexually dimorphic manner, since neuronal activation enhanced ethanol sedation in males, but not females. Finally, we provide anatomical evidence that tank-expressing neurons form likely synaptic connections with neurons expressing the neural sex determination factor fruitless (fru), which have been implicated recently in the regulation of ethanol sensitivity. We suggest that a functional interaction with fru neurons, many of which are sexually dimorphic, may account for the sex-specific effect induced by activating tank neurons. Overall, we have characterized a novel gene and corresponding set of neurons that regulate ethanol sensitivity in Drosophila.

The Novel Gene tank, a Tumor Suppressor Homolog, Regulates Ethanol Sensitivity in Drosophila

PubMed Central

Eddison, Mark; Heberlein, Ulrike

2013-01-01

In both mammalian and insect models of ethanol intoxication, high doses of ethanol induce motor impairment and eventually sedation. Sensitivity to the sedative effects of ethanol is inversely correlated with risk for alcoholism. However, the genes regulating ethanol sensitivity are largely unknown. Based on a previous genetic screen in Drosophila for ethanol sedation mutants, we identified a novel gene, tank (CG15626), the homolog of the mammalian tumor suppressor EI24/PIG8, which has a strong role in regulating ethanol sedation sensitivity. Genetic and behavioral analyses revealed that tank acts in the adult nervous system to promote ethanol sensitivity. We localized the function of tank in regulating ethanol sensitivity to neurons within the pars intercerebralis that have not been implicated previously in ethanol responses. We show that acutely manipulating the activity of all tank-expressing neurons, or of pars intercerebralis neurons in particular, alters ethanol sensitivity in a sexually dimorphic manner, since neuronal activation enhanced ethanol sedation in males, but not females. Finally, we provide anatomical evidence that tank-expressing neurons form likely synaptic connections with neurons expressing the neural sex determination factor fruitless (fru), which have been implicated recently in the regulation of ethanol sensitivity. We suggest that a functional interaction with fru neurons, many of which are sexually dimorphic, may account for the sex-specific effect induced by activating tank neurons. Overall, we have characterized a novel gene and corresponding set of neurons that regulate ethanol sensitivity in Drosophila. PMID:23658154

Mesopontine median raphe regulates hippocampal ripple oscillation and memory consolidation.

PubMed

Wang, Dong V; Yau, Hau-Jie; Broker, Carl J; Tsou, Jen-Hui; Bonci, Antonello; Ikemoto, Satoshi

2015-05-01

Sharp wave-associated field oscillations (∼200 Hz) of the hippocampus, referred to as ripples, are believed to be important for consolidation of explicit memory. Little is known about how ripples are regulated by other brain regions. We found that the median raphe region (MnR) is important for regulating hippocampal ripple activity and memory consolidation. We performed in vivo simultaneous recording in the MnR and hippocampus of mice and found that, when a group of MnR neurons was active, ripples were absent. Consistently, optogenetic stimulation of MnR neurons suppressed ripple activity and inhibition of these neurons increased ripple activity. Notably, using a fear conditioning procedure, we found that photostimulation of MnR neurons interfered with memory consolidation. Our results demonstrate a critical role of the MnR in regulating ripples and memory consolidation.

Mesopontine median raphe regulates hippocampal ripple oscillation and memory consolidation

PubMed Central

Wang, Dong V.; Yau, Hau-Jie; Broker, Carl J.; Tsou, Jen-Hui; Bonci, Antonello; Ikemoto, Satoshi

2015-01-01

Sharp-wave associated field-oscillations (~200 Hz) of the hippocampus, referred to as “ripples”, are believed to be important for consolidation of explicit memory. Little is known about how ripples are regulated by other brain regions. Here we show that the median raphe region (MnR) plays a key role in regulating hippocampal ripple activity and memory consolidation. We performed in vivo simultaneous recording in the MnR and hippocampus, and found that when a group of MnR neurons were active, ripples were absent. Consistently, optogenetic stimulation of MnR neurons suppressed ripple activity, while inhibition of these neurons increased ripple activity. Importantly, using a fear conditioning procedure, we provided evidence that photostimulation of MnR neurons interfered with memory consolidation. Our results demonstrate a critical role of the MnR in regulating ripples and memory consolidation. PMID:25867120

Neurons for hunger and thirst transmit a negative-valence teaching signal

PubMed Central

Gong, Rong; Magnus, Christopher J.; Yu, Yang; Sternson, Scott M.

2015-01-01

Homeostasis is a biological principle for regulation of essential physiological parameters within a set range. Behavioural responses due to deviation from homeostasis are critical for survival, but motivational processes engaged by physiological need states are incompletely understood. We examined motivational characteristics and dynamics of two separate neuron populations that regulate energy and fluid homeostasis by using cell type-specific activity manipulations in mice. We found that starvation-sensitive AGRP neurons exhibit properties consistent with a negative-valence teaching signal. Mice avoided activation of AGRP neurons, indicating that AGRP neuron activity has negative valence. AGRP neuron inhibition conditioned preference for flavours and places. Correspondingly, deep-brain calcium imaging revealed that AGRP neuron activity rapidly reduced in response to food-related cues. Complementary experiments activating thirst-promoting neurons also conditioned avoidance. Therefore, these need-sensing neurons condition preference for environmental cues associated with nutrient or water ingestion, which is learned through reduction of negative-valence signals during restoration of homeostasis. PMID:25915020

Proton detection and breathing regulation by the retrotrapezoid nucleus

PubMed Central

Bayliss, Douglas A.; Stornetta, Ruth L.; Ludwig, Marie‐Gabrielle; Kumar, Natasha N.; Shi, Yingtang; Burke, Peter G. R.; Kanbar, Roy; Basting, Tyler M.; Holloway, Benjamin B.; Wenker, Ian C.

2016-01-01

Abstract We discuss recent evidence which suggests that the principal central respiratory chemoreceptors are located within the retrotrapezoid nucleus (RTN) and that RTN neurons are directly sensitive to [H+]. RTN neurons are glutamatergic. In vitro, their activation by [H+] requires expression of a proton‐activated G protein‐coupled receptor (GPR4) and a proton‐modulated potassium channel (TASK‐2) whose transcripts are undetectable in astrocytes and the rest of the lower brainstem respiratory network. The pH response of RTN neurons is modulated by surrounding astrocytes but genetic deletion of RTN neurons or deletion of both GPR4 and TASK‐2 virtually eliminates the central respiratory chemoreflex. Thus, although this reflex is regulated by innumerable brain pathways, it seems to operate predominantly by modulating the discharge rate of RTN neurons, and the activation of RTN neurons by hypercapnia may ultimately derive from their intrinsic pH sensitivity. RTN neurons increase lung ventilation by stimulating multiple aspects of breathing simultaneously. They stimulate breathing about equally during quiet wake and non‐rapid eye movement (REM) sleep, and to a lesser degree during REM sleep. The activity of RTN neurons is regulated by inhibitory feedback and by excitatory inputs, notably from the carotid bodies. The latter input operates during normo‐ or hypercapnia but fails to activate RTN neurons under hypocapnic conditions. RTN inhibition probably limits the degree of hyperventilation produced by hypocapnic hypoxia. RTN neurons are also activated by inputs from serotonergic neurons and hypothalamic neurons. The absence of RTN neurons probably underlies the sleep apnoea and lack of chemoreflex that characterize congenital central hypoventilation syndrome. PMID:26748771

ROCK1 in AgRP neurons regulates energy expenditure and locomotor activity in male mice.

PubMed

Huang, Hu; Lee, Seung Hwan; Ye, Chianping; Lima, Ines S; Oh, Byung-Chul; Lowell, Bradford B; Zabolotny, Janice M; Kim, Young-Bum

2013-10-01

Normal leptin signaling is essential for the maintenance of body weight homeostasis. Proopiomelanocortin- and agouti-related peptide (AgRP)-producing neurons play critical roles in regulating energy metabolism. Our recent work demonstrates that deletion of Rho-kinase 1 (ROCK1) in the AgRP neurons of mice increased body weight and adiposity. Here, we report that selective loss of ROCK1 in AgRP neurons caused a significant decrease in energy expenditure and locomotor activity of mice. These effects were independent of any change in food intake. Furthermore, AgRP neuron-specific ROCK1-deficient mice displayed central leptin resistance, as evidenced by impaired Signal Transducer and Activator of Transcription 3 activation in response to leptin administration. Leptin's ability to hyperpolarize and decrease firing rate of AgRP neurons was also abolished in the absence of ROCK1. Moreover, diet-induced and genetic forms of obesity resulted in reduced ROCK1 activity in murine arcuate nucleus. Of note, high-fat diet also impaired leptin-stimulated ROCK1 activity in arcuate nucleus, suggesting that a defect in hypothalamic ROCK1 activity may contribute to the pathogenesis of central leptin resistance in obesity. Together, these data demonstrate that ROCK1 activation in hypothalamic AgRP neurons is required for the homeostatic regulation of energy expenditure and adiposity. These results further support previous work identifying ROCK1 as a key regulator of energy balance and suggest that targeting ROCK1 in the hypothalamus may lead to development of antiobesity therapeutics.

Concurrent and robust regulation of feeding behaviors and metabolism by orexin neurons.

PubMed

Inutsuka, Ayumu; Inui, Azusa; Tabuchi, Sawako; Tsunematsu, Tomomi; Lazarus, Michael; Yamanaka, Akihiro

2014-10-01

Orexin neurons in the hypothalamus regulate energy homeostasis by coordinating various physiological responses. Past studies have shown the role of the orexin peptide itself; however, orexin neurons contain not only orexin but also other neurotransmitters such as glutamate and dynorphin. In this study, we examined the physiological role of orexin neurons in feeding behavior and metabolism by pharmacogenetic activation and chronic ablation. We generated novel orexin-Cre mice and utilized Cre-dependent adeno-associated virus vectors to express Gq-coupled modified GPCR, hM3Dq or diphtheria toxin fragment A in orexin neurons. By intraperitoneal injection of clozapine-N oxide in orexin-Cre mice expressing hM3Dq in orexin neurons, we could selectively manipulate the activity of orexin neurons. Pharmacogenetic stimulation of orexin neurons simultaneously increased locomotive activity, food intake, water intake and the respiratory exchange ratio (RER). Elevation of blood glucose levels and RER persisted even after locomotion and feeding behaviors returned to basal levels. Accordantly, 83% ablation of orexin neurons resulted in decreased food and water intake, while 70% ablation had almost no effect on these parameters. Our results indicate that orexin neurons play an integral role in regulation of both feeding behavior and metabolism. This regulation is so robust that greater than 80% of orexin neurons were ablated before significant changes in feeding behavior emerged. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

Serotonin 2C receptor activates a distinct population of arcuate pro-opiomelanocortin neurons via TRPC channels

USDA-ARS?s Scientific Manuscript database

Serotonin 2C receptors (5-HT2CRs) expressed by pro-opiomelanocortin (POMC) neurons of hypothalamic arcuate nucleus regulate food intake, energy homeostasis ,and glucose metabolism. However, the cellular mechanisms underlying the effects of 5-HT to regulate POMC neuronal activity via 5-HT2CRs have no...

Neuronal expression of glucosylceramide synthase in central nervous system regulates body weight and energy homeostasis.

PubMed

Nordström, Viola; Willershäuser, Monja; Herzer, Silke; Rozman, Jan; von Bohlen Und Halbach, Oliver; Meldner, Sascha; Rothermel, Ulrike; Kaden, Sylvia; Roth, Fabian C; Waldeck, Clemens; Gretz, Norbert; de Angelis, Martin Hrabě; Draguhn, Andreas; Klingenspor, Martin; Gröne, Hermann-Josef; Jennemann, Richard

2013-01-01

Hypothalamic neurons are main regulators of energy homeostasis. Neuronal function essentially depends on plasma membrane-located gangliosides. The present work demonstrates that hypothalamic integration of metabolic signals requires neuronal expression of glucosylceramide synthase (GCS; UDP-glucose:ceramide glucosyltransferase). As a major mechanism of central nervous system (CNS) metabolic control, we demonstrate that GCS-derived gangliosides interacting with leptin receptors (ObR) in the neuronal membrane modulate leptin-stimulated formation of signaling metabolites in hypothalamic neurons. Furthermore, ganglioside-depleted hypothalamic neurons fail to adapt their activity (c-Fos) in response to alterations in peripheral energy signals. Consequently, mice with inducible forebrain neuron-specific deletion of the UDP-glucose:ceramide glucosyltransferase gene (Ugcg) display obesity, hypothermia, and lower sympathetic activity. Recombinant adeno-associated virus (rAAV)-mediated Ugcg delivery to the arcuate nucleus (Arc) significantly ameliorated obesity, specifying gangliosides as seminal components for hypothalamic regulation of body energy homeostasis.

Prolactin regulation of oxytocin neurone activity in pregnancy and lactation.

PubMed

Augustine, Rachael A; Ladyman, Sharon R; Bouwer, Gregory T; Alyousif, Yousif; Sapsford, Tony J; Scott, Victoria; Kokay, Ilona C; Grattan, David R; Brown, Colin H

2017-06-01

During lactation, prolactin promotes milk synthesis and oxytocin stimulates milk ejection. In virgin rats, prolactin inhibits the activity of oxytocin-secreting neurones. We found that prolactin inhibition of oxytocin neurone activity is lost in lactation, and that some oxytocin neurones were excited by prolactin in lactating rats. The change in prolactin regulation of oxytocin neurone activity was not associated with a change in activation of intracellular signalling pathways known to couple to prolactin receptors. The change in prolactin regulation of oxytocin neurone activity in lactation might allow coordinated activation of both populations of neurones when required for successful lactation. Secretion of prolactin for milk synthesis and oxytocin for milk secretion is required for successful lactation. In virgin rats, prolactin inhibits oxytocin neurones but this effect would be counterproductive during lactation when secretion of both hormones is required for synthesis and delivery of milk to the newborn. Hence, we determined the effects of intracerebroventricular (i.c.v.) prolactin on oxytocin neurones in urethane-anaesthetised virgin, pregnant and lactating rats. Prolactin (2 μg) consistently inhibited oxytocin neurones in virgin and pregnant rats (by 1.9 ± 0.4 and 1.8 ± 0.5 spikes s -1 , respectively), but not in lactating rats; indeed, prolactin excited six of 27 oxytocin neurones by >1 spike s -1 in lactating rats but excited none in virgin or pregnant rats (χ 2 2  = 7.2, P = 0.03). Vasopressin neurones were unaffected by prolactin (2 μg) in virgin rats but were inhibited by 1.1 ± 0.2 spikes s -1 in lactating rats. Immunohistochemistry showed that i.c.v. prolactin increased oxytocin expression in virgin and lactating rats and increased signal transducer and activator of transcription 5 phosphorylation to a similar extent in oxytocin neurones of virgin and lactating rats. Western blotting showed that i.c.v. prolactin did not affect phosphorylation of extracellular regulated kinase 1 or 2, or of Akt in the supraoptic or paraventricular nuclei of virgin or lactating rats. Hence, prolactin inhibition of oxytocin neurones is lost in lactation, which might allow concurrent elevation of prolactin secretion from the pituitary gland and activation of oxytocin neurones for synthesis and delivery of milk to the newborn. © 2017 The Authors. The Journal of Physiology © 2017 The Physiological Society.

Common inputs in subthreshold membrane potential: The role of quiescent states in neuronal activity

NASA Astrophysics Data System (ADS)

Montangie, Lisandro; Montani, Fernando

2018-06-01

Experiments in certain regions of the cerebral cortex suggest that the spiking activity of neuronal populations is regulated by common non-Gaussian inputs across neurons. We model these deviations from random-walk processes with q -Gaussian distributions into simple threshold neurons, and investigate the scaling properties in large neural populations. We show that deviations from the Gaussian statistics provide a natural framework to regulate population statistics such as sparsity, entropy, and specific heat. This type of description allows us to provide an adequate strategy to explain the information encoding in the case of low neuronal activity and its possible implications on information transmission.

A Small Potassium Current in AgRP/NPY Neurons Regulates Feeding Behavior and Energy Metabolism.

PubMed

He, Yanlin; Shu, Gang; Yang, Yongjie; Xu, Pingwen; Xia, Yan; Wang, Chunmei; Saito, Kenji; Hinton, Antentor; Yan, Xiaofeng; Liu, Chen; Wu, Qi; Tong, Qingchun; Xu, Yong

2016-11-08

Neurons that co-express agouti-related peptide (AgRP) and neuropeptide Y (NPY) are indispensable for normal feeding behavior. Firing activities of AgRP/NPY neurons are dynamically regulated by energy status and coordinate appropriate feeding behavior to meet nutritional demands. However, intrinsic mechanisms that regulate AgRP/NPY neural activities during the fed-to-fasted transition are not fully understood. We found that AgRP/NPY neurons in satiated mice express high levels of the small-conductance calcium-activated potassium channel 3 (SK3) and are inhibited by SK3-mediated potassium currents; on the other hand, food deprivation suppresses SK3 expression in AgRP/NPY neurons, and the decreased SK3-mediated currents contribute to fasting-induced activation of these neurons. Genetic mutation of SK3 specifically in AgRP/NPY neurons leads to increased sensitivity to diet-induced obesity, associated with chronic hyperphagia and decreased energy expenditure. Our results identify SK3 as a key intrinsic mediator that coordinates nutritional status with AgRP/NPY neural activities and animals' feeding behavior and energy metabolism. Copyright © 2016 The Author(s). Published by Elsevier Inc. All rights reserved.

The Role of Glia in Sleep Regulation and Function.

PubMed

Frank, Marcos G

2018-01-28

The cellular mechanisms governing the expression, regulation, and function of sleep are not entirely understood. The traditional view is that these mechanisms are neuronal. An alternative view is that glial brain cells may play important roles in these processes. Their ubiquity in the central nervous system makes them well positioned to modulate neuronal circuits that gate sleep and wake. Their ability to respond to chemical neuronal signals suggests that they form feedback loops with neurons that may globally regulate neuronal activity. Their potential role in detoxifying the brain, regulating neuronal metabolism, and promoting synaptic plasticity raises the intriguing possibility that glia mediate important functions ascribed to sleep.

miR-132 Regulates Dendritic Spine Structure by Direct Targeting of Matrix Metalloproteinase 9 mRNA.

PubMed

Jasińska, Magdalena; Miłek, Jacek; Cymerman, Iwona A; Łęski, Szymon; Kaczmarek, Leszek; Dziembowska, Magdalena

2016-09-01

Mir-132 is a neuronal activity-regulated microRNA that controls the morphology of dendritic spines and neuronal transmission. Similar activities have recently been attributed to matrix metalloproteinase-9 (MMP-9), an extrasynaptic protease. In the present study, we provide evidence that miR-132 directly regulates MMP-9 mRNA in neurons to modulate synaptic plasticity. With the use of luciferase reporter system, we show that miR-132 binds to the 3'UTR of MMP-9 mRNA to regulate its expression in neurons. The overexpression of miR-132 in neurons reduces the level of endogenous MMP-9 protein secretion. In synaptoneurosomes, metabotropic glutamate receptor (mGluR)-induced signaling stimulates the dissociation of miR-132 from polyribosomal fractions and shifts it towards the messenger ribonucleoprotein (mRNP)-containing fraction. Furthermore, we demonstrate that the overexpression of miR-132 in the cultured hippocampal neurons from Fmr1 KO mice that have increased synaptic MMP-9 level provokes enlargement of the dendritic spine heads, a process previously implicated in enhanced synaptic plasticity. We propose that activity-dependent miR-132 regulates structural plasticity of dendritic spines through matrix metalloproteinase 9.

Regulation of Na(+)/K(+)-ATPase by neuron-specific transcription factor Sp4: implication in the tight coupling of energy production, neuronal activity and energy consumption in neurons.

PubMed

Johar, Kaid; Priya, Anusha; Wong-Riley, Margaret T T

2014-02-01

A major source of energy demand in neurons is the Na(+)/K(+)-ATPase pump that restores the ionic gradient across the plasma membrane subsequent to depolarizing neuronal activity. The energy comes primarily from mitochondrial oxidative metabolism, of which cytochrome c oxidase (COX) is a key enzyme. Recently, we found that all 13 subunits of COX are regulated by specificity (Sp) factors, and that the neuron-specific Sp4, but not Sp1 or Sp3, regulates the expression of key glutamatergic receptor subunits as well. The present study sought to test our hypothesis that Sp4 also regulates Na(+)/K(+)-ATPase subunit genes in neurons. By means of multiple approaches, including in silico analysis, electrophoretic mobility shift and supershift assays, chromatin immunoprecipitation, promoter mutational analysis, over-expression, and RNA interference studies, we found that Sp4, with minor contributions from Sp1 and Sp3, functionally regulate the Atp1a1, Atp1a3, and Atp1b1 subunit genes of Na(+)/K(+)-ATPase in neurons. Transcripts of all three genes were up-regulated by depolarizing KCl stimulation and down-regulated by the impulse blocker tetrodotoxin (TTX), indicating that their expression was activity-dependent. Silencing of Sp4 blocked the up-regulation of these genes induced by KCl, whereas over-expression of Sp4 rescued them from TTX-induced suppression. The effect of silencing or over-expressing Sp4 on primary neurons was much greater than those of Sp1 or Sp3. The binding sites of Sp factors on these genes are conserved among mice, rats and humans. Thus, Sp4 plays an important role in the transcriptional coupling of energy generation and energy consumption in neurons. © 2013 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Lhx2 Expression in Postmitotic Cortical Neurons Initiates Assembly of the Thalamocortical Somatosensory Circuit.

PubMed

Wang, Chia-Fang; Hsing, Hsiang-Wei; Zhuang, Zi-Hui; Wen, Meng-Hsuan; Chang, Wei-Jen; Briz, Carlos G; Nieto, Marta; Shyu, Bai Chuang; Chou, Shen-Ju

2017-01-24

Cortical neurons must be specified and make the correct connections during development. Here, we examine a mechanism initiating neuronal circuit formation in the barrel cortex, a circuit comprising thalamocortical axons (TCAs) and layer 4 (L4) neurons. When Lhx2 is selectively deleted in postmitotic cortical neurons using conditional knockout (cKO) mice, L4 neurons in the barrel cortex are initially specified but fail to form cellular barrels or develop polarized dendrites. In Lhx2 cKO mice, TCAs from the thalamic ventral posterior nucleus reach the barrel cortex but fail to further arborize to form barrels. Several activity-regulated genes and genes involved in regulating barrel formation are downregulated in the Lhx2 cKO somatosensory cortex. Among them, Btbd3, an activity-regulated gene controlling dendritic development, is a direct downstream target of Lhx2. We find that Lhx2 confers neuronal competency for activity-dependent dendritic development in L4 neurons by inducing the expression of Btbd3. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

Nitric Oxide Is an Activity-Dependent Regulator of Target Neuron Intrinsic Excitability

PubMed Central

Steinert, Joern R.; Robinson, Susan W.; Tong, Huaxia; Haustein, Martin D.; Kopp-Scheinpflug, Cornelia; Forsythe, Ian D.

2011-01-01

Summary Activity-dependent changes in synaptic strength are well established as mediating long-term plasticity underlying learning and memory, but modulation of target neuron excitability could complement changes in synaptic strength and regulate network activity. It is thought that homeostatic mechanisms match intrinsic excitability to the incoming synaptic drive, but evidence for involvement of voltage-gated conductances is sparse. Here, we show that glutamatergic synaptic activity modulates target neuron excitability and switches the basis of action potential repolarization from Kv3 to Kv2 potassium channel dominance, thereby adjusting neuronal signaling between low and high activity states, respectively. This nitric oxide-mediated signaling dramatically increases Kv2 currents in both the auditory brain stem and hippocampus (>3-fold) transforming synaptic integration and information transmission but with only modest changes in action potential waveform. We conclude that nitric oxide is a homeostatic regulator, tuning neuronal excitability to the recent history of excitatory synaptic inputs over intervals of minutes to hours. PMID:21791288

A Co-operative Regulation of Neuronal Excitability by UNC-7 Innexin and NCA/NALCN Leak Channel

PubMed Central

2011-01-01

Gap junctions mediate the electrical coupling and intercellular communication between neighboring cells. Some gap junction proteins, namely connexins and pannexins in vertebrates, and innexins in invertebrates, may also function as hemichannels. A conserved NCA/Dmα1U/NALCN family cation leak channel regulates the excitability and activity of vertebrate and invertebrate neurons. In the present study, we describe a genetic and functional interaction between the innexin UNC-7 and the cation leak channel NCA in Caenorhabditis elegans neurons. While the loss of the neuronal NCA channel function leads to a reduced evoked postsynaptic current at neuromuscular junctions, a simultaneous loss of the UNC-7 function restores the evoked response. The expression of UNC-7 in neurons reverts the effect of the unc-7 mutation; moreover, the expression of UNC-7 mutant proteins that are predicted to be unable to form gap junctions also reverts this effect, suggesting that UNC-7 innexin regulates neuronal activity, in part, through gap junction-independent functions. We propose that, in addition to gap junction-mediated functions, UNC-7 innexin may also form hemichannels to regulate C. elegans' neuronal activity cooperatively with the NCA family leak channels. PMID:21489288

Divergent Regulation of Energy Expenditure and Hepatic Glucose Production by Insulin Receptor in Agouti-Related Protein and POMC Neurons

PubMed Central

Lin, Hua V.; Plum, Leona; Ono, Hiraku; Gutiérrez-Juárez, Roger; Shanabrough, Marya; Borok, Erzsebet; Horvath, Tamas L.; Rossetti, Luciano; Accili, Domenico

2010-01-01

OBJECTIVE The sites of insulin action in the central nervous system that regulate glucose metabolism and energy expenditure are incompletely characterized. We have shown that mice with hypothalamic deficiency (L1) of insulin receptors (InsRs) fail to regulate hepatic glucose production (HGP) in response to insulin. RESEARCH DESIGN AND METHODS To distinguish neurons that mediate insulin's effects on HGP from those that regulate energy homeostasis, we used targeted knock-ins to express InsRs in agouti-related protein (AgRP) or proopiomelanocortin (POMC) neurons of L1 mice. RESULTS Restoration of insulin action in AgRP neurons normalized insulin suppression of HGP. Surprisingly, POMC-specific InsR knock-in increased energy expenditure and locomotor activity, exacerbated insulin resistance and increased HGP, associated with decreased expression of the ATP-sensitive K+ channel (KATP channel) sulfonylurea receptor 1 subunit, and decreased inhibitory synaptic contacts on POMC neurons. CONCLUSIONS The contrasting phenotypes of InsR knock-ins in POMC and AgRP neurons suggest a branched-pathway model of hypothalamic insulin signaling in which InsR signaling in AgRP neurons decreases HGP, whereas InsR activation in POMC neurons promotes HGP and activates the melanocortinergic energy expenditure program. PMID:19933998

Neuronal Activity Promotes Glioma Growth through Neuroligin-3 Secretion.

PubMed

Venkatesh, Humsa S; Johung, Tessa B; Caretti, Viola; Noll, Alyssa; Tang, Yujie; Nagaraja, Surya; Gibson, Erin M; Mount, Christopher W; Polepalli, Jai; Mitra, Siddhartha S; Woo, Pamelyn J; Malenka, Robert C; Vogel, Hannes; Bredel, Markus; Mallick, Parag; Monje, Michelle

2015-05-07

Active neurons exert a mitogenic effect on normal neural precursor and oligodendroglial precursor cells, the putative cellular origins of high-grade glioma (HGG). By using optogenetic control of cortical neuronal activity in a patient-derived pediatric glioblastoma xenograft model, we demonstrate that active neurons similarly promote HGG proliferation and growth in vivo. Conditioned medium from optogenetically stimulated cortical slices promoted proliferation of pediatric and adult patient-derived HGG cultures, indicating secretion of activity-regulated mitogen(s). The synaptic protein neuroligin-3 (NLGN3) was identified as the leading candidate mitogen, and soluble NLGN3 was sufficient and necessary to promote robust HGG cell proliferation. NLGN3 induced PI3K-mTOR pathway activity and feedforward expression of NLGN3 in glioma cells. NLGN3 expression levels in human HGG negatively correlated with patient overall survival. These findings indicate the important role of active neurons in the brain tumor microenvironment and identify secreted NLGN3 as an unexpected mechanism promoting neuronal activity-regulated cancer growth. Copyright © 2015 Elsevier Inc. All rights reserved.

Overnight Fasting Regulates Inhibitory Tone to Cholinergic Neurons of the Dorsomedial Nucleus of the Hypothalamus

PubMed Central

Groessl, Florian; Jeong, Jae Hoon; Talmage, David A.; Role, Lorna W.; Jo, Young-Hwan

2013-01-01

The dorsomedial nucleus of the hypothalamus (DMH) contributes to the regulation of overall energy homeostasis by modulating energy intake as well as energy expenditure. Despite the importance of the DMH in the control of energy balance, DMH-specific genetic markers or neuronal subtypes are poorly defined. Here we demonstrate the presence of cholinergic neurons in the DMH using genetically modified mice that express enhanced green florescent protein (eGFP) selectively in choline acetyltransferase (Chat)-neurons. Overnight food deprivation increases the activity of DMH cholinergic neurons, as shown by induction of fos protein and a significant shift in the baseline resting membrane potential. DMH cholinergic neurons receive both glutamatergic and GABAergic synaptic input, but the activation of these neurons by an overnight fast is due entirely to decreased inhibitory tone. The decreased inhibition is associated with decreased frequency and amplitude of GABAergic synaptic currents in the cholinergic DMH neurons, while glutamatergic synaptic transmission is not altered. As neither the frequency nor amplitude of miniature GABAergic or glutamatergic postsynaptic currents is affected by overnight food deprivation, the fasting-induced decrease in inhibitory tone to cholinergic neurons is dependent on superthreshold activity of GABAergic inputs. This study reveals that cholinergic neurons in the DMH readily sense the availability of nutrients and respond to overnight fasting via decreased GABAergic inhibitory tone. As such, altered synaptic as well as neuronal activity of DMH cholinergic neurons may play a critical role in the regulation of overall energy homeostasis. PMID:23585854

Arcuate Na+,K+-ATPase senses systemic energy states and regulates feeding behavior through glucose-inhibited neurons.

PubMed

Kurita, Hideharu; Xu, Kai Y; Maejima, Yuko; Nakata, Masanori; Dezaki, Katsuya; Santoso, Putra; Yang, Yifei; Arai, Takeshi; Gantulga, Darambazar; Muroya, Shinji; Lefor, Alan K; Kakei, Masafumi; Watanabe, Eiju; Yada, Toshihiko

2015-08-15

Feeding is regulated by perception in the hypothalamus, particularly the first-order arcuate nucleus (ARC) neurons, of the body's energy state. However, the cellular device for converting energy states to the activity of critical neurons in ARC is less defined. We here show that Na(+),K(+)-ATPase (NKA) in ARC senses energy states to regulate feeding. Fasting-induced systemic ghrelin rise and glucose lowering reduced ATP-hydrolyzing activity of NKA and its substrate ATP level, respectively, preferentially in ARC. Lowering glucose concentration (LG), which mimics fasting, decreased intracellular NAD(P)H and increased Na(+) concentration in single ARC neurons that subsequently exhibited [Ca(2+)]i responses to LG, showing that they were glucose-inhibited (GI) neurons. Third ventricular injection of the NKA inhibitor ouabain induced c-Fos expression in agouti-related protein (AgRP) neurons in ARC and evoked neuropeptide Y (NPY)-dependent feeding. When injected focally into ARC, ouabain stimulated feeding and mRNA expressions for NPY and AgRP. Ouabain increased [Ca(2+)]i in single NPY/AgRP neurons with greater amplitude than in proopiomelanocortin neurons in ARC. Conversely, the specific NKA activator SSA412 suppressed fasting-induced feeding and LG-induced [Ca(2+)]i increases in ARC GI neurons. NPY/AgRP neurons highly expressed NKAα3, whose knockdown impaired feeding behavior. These results demonstrate that fasting, via ghrelin rise and LG, suppresses NKA enzyme/pump activity in ARC and thereby promotes the activation of GI neurons and NPY/AgRP-dependent feeding. This study identifies ARC NKA as a hypothalamic sensor and converter of metabolic states to key neuronal activity and feeding behaviour, providing a new target to treat hyperphagic obesity and diabetes. Copyright © 2015 the American Physiological Society.

The synchronous activity of lateral habenular neurons is essential for regulating hippocampal theta oscillation.

PubMed

Aizawa, Hidenori; Yanagihara, Shin; Kobayashi, Megumi; Niisato, Kazue; Takekawa, Takashi; Harukuni, Rie; McHugh, Thomas J; Fukai, Tomoki; Isomura, Yoshikazu; Okamoto, Hitoshi

2013-05-15

Lateral habenula (LHb) has attracted growing interest as a regulator of serotonergic and dopaminergic neurons in the CNS. However, it remains unclear how the LHb modulates brain states in animals. To identify the neural substrates that are under the influence of LHb regulation, we examined the effects of rat LHb lesions on the hippocampal oscillatory activity associated with the transition of brain states. Our results showed that the LHb lesion shortened the theta activity duration both in anesthetized and sleeping rats. Furthermore, this inhibitory effect of LHb lesion on theta maintenance depended upon an intact serotonergic median raphe, suggesting that LHb activity plays an essential role in maintaining hippocampal theta oscillation via the serotonergic raphe. Multiunit recording of sleeping rats further revealed that firing of LHb neurons showed significant phase-locking activity at each theta oscillation cycle in the hippocampus. LHb neurons showing activity that was coordinated with that of the hippocampal theta were localized in the medial LHb division, which receives afferents from the diagonal band of Broca (DBB), a pacemaker region for the hippocampal theta oscillation. Thus, our findings indicate that the DBB may pace not only the hippocampus, but also the LHb, during rapid eye movement sleep. Since serotonin is known to negatively regulate theta oscillation in the hippocampus, phase-locking activity of the LHb neurons may act, under the influence of the DBB, to maintain the hippocampal theta oscillation by modulating the activity of serotonergic neurons.

Role of GABA Release From Leptin Receptor-Expressing Neurons in Body Weight Regulation

PubMed Central

Xu, Yuanzhong; O'Brien, William G.; Lee, Cheng-Chi; Myers, Martin G.

2012-01-01

It is well established that leptin regulates energy balance largely through isoform B leptin receptor-expressing neurons (LepR neurons) in the brain and that leptin activates one subset of LepR neurons (leptin-excited neurons) while inhibiting the other (leptin-inhibited neurons). However, the neurotransmitters released from LepR neurons that mediate leptin action in the brain are not well understood. Previous results demonstrate that leptin mainly acts on γ-aminobutyric acid (GABA)ergic neurons to reduce body weight, and that leptin activates proopiomelanocortin neuron activity by reducing GABA release onto these neurons, suggesting a body weight-promoting role for GABA released from leptin-inhibited neurons. To directly examine the role of GABA release from LepR neurons in body weight regulation, mice with disruption of GABA release specifically from LepR neurons were generated by deletion of vesicular GABA transporter in LepR neurons. Interestingly, these mice developed mild obesity on chow diet and were sensitive to diet-induced obesity, which were associated with higher food intake and lower energy expenditure. Moreover, these mice showed blunted responses in both food intake and body weight to acute leptin administration. These results demonstrate that GABA plays an important role in mediating leptin action. In combination with the previous studies that leptin reduces GABA release onto proopiomelanocortin neurons through leptin-inhibited neurons and that disruption of GABA release from agouti gene-related protein neurons, one subset of LepR-inhibited neurons, leads to a lean phenotype, our results suggest that, under our experimental conditions, GABA release from leptin-excited neuron dominates over leptin-inhibited ones. PMID:22334723

Neuron-Glia Interactions and Nervous System Homeostasis

DTIC Science & Technology

1988-06-01

active neuron states, the mechanisms which glial cells and neurons use to modulate each others metabolic state and the chemical, electrical and... mechanisms by which axons/neurons and their glial cell investments communicate to actively regulate the ionic microenvironment of the nervous system and...of the glial cell in maintenance of the ionic homeostasis of the perineural environment during resting and active neuron states, the mechanisms which

HCN2 channels in the ventral tegmental area regulate behavioral responses to chronic stress

PubMed Central

Zhong, Peng; Vickstrom, Casey R; Liu, Xiaojie; Hu, Ying; Yu, Laikang; Yu, Han-Gang

2018-01-01

Dopamine neurons in the ventral tegmental area (VTA) are powerful regulators of depression-related behavior. Dopamine neuron activity is altered in chronic stress-based models of depression, but the underlying mechanisms remain incompletely understood. Here, we show that mice subject to chronic mild unpredictable stress (CMS) exhibit anxiety- and depressive-like behavior, which was associated with decreased VTA dopamine neuron firing in vivo and ex vivo. Dopamine neuron firing is governed by voltage-gated ion channels, in particular hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. Following CMS, HCN-mediated currents were decreased in nucleus accumbens-projecting VTA dopamine neurons. Furthermore, shRNA-mediated HCN2 knockdown in the VTA was sufficient to recapitulate CMS-induced depressive- and anxiety-like behavior in stress-naïve mice, whereas VTA HCN2 overexpression largely prevented CMS-induced behavioral deficits. Together, these results reveal a critical role for HCN2 in regulating VTA dopamine neuronal activity and depressive-related behaviors. PMID:29256865

Fine-tuned SRF activity controls asymmetrical neuronal outgrowth: implications for cortical migration, neural tissue lamination and circuit assembly

PubMed Central

Scandaglia, Marilyn; Benito, Eva; Morenilla-Palao, Cruz; Fiorenza, Anna; del Blanco, Beatriz; Coca, Yaiza; Herrera, Eloísa; Barco, Angel

2015-01-01

The stimulus-regulated transcription factor Serum Response Factor (SRF) plays an important role in diverse neurodevelopmental processes related to structural plasticity and motile functions, although its precise mechanism of action has not yet been established. To further define the role of SRF in neural development and distinguish between cell-autonomous and non cell-autonomous effects, we bidirectionally manipulated SRF activity through gene transduction assays that allow the visualization of individual neurons and their comparison with neighboring control cells. In vitro assays showed that SRF promotes survival and filopodia formation and is required for normal asymmetric neurite outgrowth, indicating that its activation favors dendrite enlargement versus branching. In turn, in vivo experiments demonstrated that SRF-dependent regulation of neuronal morphology has important consequences in the developing cortex and retina, affecting neuronal migration, dendritic and axonal arborization and cell positioning in these laminated tissues. Overall, our results show that the controlled and timely activation of SRF is essential for the coordinated growth of neuronal processes, suggesting that this event regulates the switch between neuronal growth and branching during developmental processes. PMID:26638868

Methamphetamine Regulation of Firing Activity of Dopamine Neurons

PubMed Central

Lin, Min; Sambo, Danielle

2016-01-01

Methamphetamine (METH) is a substrate for the dopamine transporter that increases extracellular dopamine levels by competing with dopamine uptake and increasing reverse transport of dopamine via the transporter. METH has also been shown to alter the excitability of dopamine neurons. The mechanism of METH regulation of the intrinsic firing behaviors of dopamine neurons is less understood. Here we identified an unexpected and unique property of METH on the regulation of firing activity of mouse dopamine neurons. METH produced a transient augmentation of spontaneous spike activity of midbrain dopamine neurons that was followed by a progressive reduction of spontaneous spike activity. Inspection of action potential morphology revealed that METH increased the half-width and produced larger coefficients of variation of the interspike interval, suggesting that METH exposure affected the activity of voltage-dependent potassium channels in these neurons. Since METH has been shown to affect Ca2+ homeostasis, the unexpected findings that METH broadened the action potential and decreased the amplitude of afterhyperpolarization led us to ask whether METH alters the activity of Ca2+-activated potassium (BK) channels. First, we identified BK channels in dopamine neurons by their voltage dependence and their response to a BK channel blocker or opener. While METH suppressed the amplitude of BK channel-mediated unitary currents, the BK channel opener NS1619 attenuated the effects of METH on action potential broadening, afterhyperpolarization repression, and spontaneous spike activity reduction. Live-cell total internal reflection fluorescence microscopy, electrophysiology, and biochemical analysis suggest METH exposure decreased the activity of BK channels by decreasing BK-α subunit levels at the plasma membrane. SIGNIFICANCE STATEMENT Methamphetamine (METH) competes with dopamine uptake, increases dopamine efflux via the dopamine transporter, and affects the excitability of dopamine neurons. Here, we identified an unexpected property of METH on dopamine neuron firing activity. METH transiently increased the spontaneous spike activity of dopamine neurons followed by a progressive reduction of the spontaneous spike activity. METH broadened the action potentials, increased coefficients of variation of the interspike interval, and decreased the amplitude of afterhyperpolarization, which are consistent with changes in the activity of Ca2+-activated potassium (BK) channels. We found that METH decreased the activity of BK channels by stimulating BK-α subunit trafficking. Thus, METH modulation of dopamine neurotransmission and resulting behavioral responses is, in part, due to METH regulation of BK channel activity. PMID:27707972

Taotie neurons regulate appetite in Drosophila

PubMed Central

Zhan, Yin Peng; Liu, Li; Zhu, Yan

2016-01-01

The brain has an essential role in maintaining a balance between energy intake and expenditure of the body. Deciphering the processes underlying the decision-making for timely feeding of appropriate amounts may improve our understanding of physiological and psychological disorders related to feeding control. Here, we identify a group of appetite-enhancing neurons in a behavioural screen for flies with increased appetite. Manipulating the activity of these neurons, which we name Taotie neurons, induces bidirectional changes in feeding motivation. Long-term stimulation of Taotie neurons results in flies with highly obese phenotypes. Furthermore, we show that the in vivo activity of Taotie neurons in the neuroendocrine region reflects the hunger/satiety states of un-manipulated animals, and that appetitive-enhancing Taotie neurons control the secretion of insulin, a known regulator of feeding behaviour. Thus, our study reveals a new set of neurons regulating feeding behaviour in the high brain regions that represents physiological hunger states and control feeding behaviour in Drosophila. PMID:27924813

Alpha2delta-1 in SF1+ Neurons of the Ventromedial Hypothalamus Is an Essential Regulator of Glucose and Lipid Homeostasis.

PubMed

Felsted, Jennifer A; Chien, Cheng-Hao; Wang, Dongqing; Panessiti, Micaella; Ameroso, Dominique; Greenberg, Andrew; Feng, Guoping; Kong, Dong; Rios, Maribel

2017-12-05

The central mechanisms controlling glucose and lipid homeostasis are inadequately understood. We show that α2δ-1 is an essential regulator of glucose and lipid balance, acting in steroidogenic factor-1 (SF1) neurons of the ventromedial hypothalamus (VMH). These effects are body weight independent and involve regulation of SF1 + neuronal activity and sympathetic output to metabolic tissues. Accordingly, mice with α2δ-1 deletion in SF1 neurons exhibit glucose intolerance, altered lipolysis, and decreased cholesterol content in adipose tissue despite normal energy balance regulation. Profound reductions in the firing rate of SF1 neurons, decreased sympathetic output, and elevated circulating levels of serotonin are associated with these alterations. Normal calcium currents but reduced excitatory postsynaptic currents in mutant SF1 neurons implicate α2δ-1 in the promotion of excitatory synaptogenesis separate from its canonical role as a calcium channel subunit. Collectively, these findings identify an essential mechanism that regulates VMH neuronal activity and glycemic and lipid control and may be a target for tackling metabolic disease. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

The O-GlcNAc Modification of CDK5 Involved in Neuronal Apoptosis Following In Vitro Intracerebral Hemorrhage.

PubMed

Ning, Xiaojin; Tao, Tao; Shen, Jianhong; Ji, Yuteng; Xie, Lili; Wang, Hongmei; Liu, Ning; Xu, Xide; Sun, Chi; Zhang, Dongmei; Shen, Aiguo; Ke, Kaifu

2017-04-01

Contrary to cell cycle-associated cyclin-dependent kinases, CDK5 is best known for its regulation of signaling processes in regulating mammalian CNS development. Studies of CDK5 have focused on its phosphorylation, although the diversity of CDK5 functions in the brain suggests additional forms of regulation. Here we expanded on the functional roles of CDK5 glycosylation in neurons. We showed that CDK5 was dynamically modified with O-GlcNAc in response to neuronal activity and that glycosylation represses CDK5-dependent apoptosis by impairing its association with p53 pathway. Blocking glycosylation of CDK5 alters cellular function and increases neuronal apoptosis in the cell model of the ICH. Our findings demonstrated a new role for O-glycosylation in neuronal apoptosis and provided a mechanistic understanding of how glycosylation contributes to critical neuronal functions. Moreover, we identified a previously unknown mechanism for the regulation of activity-dependent gene expression, neural development, and apoptosis.

Regulation of Drosophila hematopoietic sites by Activin-β from active sensory neurons

PubMed Central

Makhijani, Kalpana; Alexander, Brandy; Rao, Deepti; Petraki, Sophia; Herboso, Leire; Kukar, Katelyn; Batool, Itrat; Wachner, Stephanie; Gold, Katrina S.; Wong, Corinna; O’Connor, Michael B.; Brückner, Katja

2017-01-01

An outstanding question in animal development, tissue homeostasis and disease is how cell populations adapt to sensory inputs. During Drosophila larval development, hematopoietic sites are in direct contact with sensory neuron clusters of the peripheral nervous system (PNS), and blood cells (hemocytes) require the PNS for their survival and recruitment to these microenvironments, known as Hematopoietic Pockets. Here we report that Activin-β, a TGF-β family ligand, is expressed by sensory neurons of the PNS and regulates the proliferation and adhesion of hemocytes. These hemocyte responses depend on PNS activity, as shown by agonist treatment and transient silencing of sensory neurons. Activin-β has a key role in this regulation, which is apparent from reporter expression and mutant analyses. This mechanism of local sensory neurons controlling blood cell adaptation invites evolutionary parallels with vertebrate hematopoietic progenitors and the independent myeloid system of tissue macrophages, whose regulation by local microenvironments remain undefined. PMID:28748922

Sonic hedgehog signaling regulates actin cytoskeleton via Tiam1-Rac1 cascade during spine formation.

PubMed

Sasaki, Nobunari; Kurisu, Junko; Kengaku, Mineko

2010-12-01

The sonic hedgehog (Shh) pathway has essential roles in several processes during development of the vertebrate central nervous system (CNS). Here, we report that Shh regulates dendritic spine formation in hippocampal pyramidal neurons via a novel pathway that directly regulates the actin cytoskeleton. Shh signaling molecules Patched (Ptc) and Smoothened (Smo) are expressed in several types of postmitotic neurons, including cerebellar Purkinje cells and hippocampal pyramidal neurons. Knockdown of Smo induces dendritic spine formation in cultured hippocampal neurons independently of Gli-mediated transcriptional activity. Smo interacts with Tiam1, a guanine nucleotide exchange factor for Rac1, via its cytoplasmic C-terminal region. Inhibition of Tiam1 or Rac1 activity suppresses spine induction by Smo knockdown. Shh induces remodeling of the actin cytoskeleton independently of transcriptional activation in mouse embryonic fibroblasts. These findings demonstrate a novel Shh pathway that regulates the actin cytoskeleton via Tiam1-Rac1 activation. Copyright © 2010 Elsevier Inc. All rights reserved.

The dusp1 Immediate Early Gene is Regulated by Natural Stimuli Predominantly in Sensory Input Neurons

PubMed Central

Horita, Haruhito; Wada, Kazuhiro; Rivas, Miriam V.; Hara, Erina; Jarvis, Erich D.

2010-01-01

Many immediate early genes (IEGs) have activity-dependent induction in a subset of brain subdivisions or neuron types. However, none have been reported yet with regulation specific to thalamic-recipient sensory neurons of the telencephalon or in the thalamic sensory input neurons themselves. Here, we report the first such gene, dual specificity phosphatase 1 (dusp1). Dusp1 is an inactivator of mitogen-activated protein kinase (MAPK), and MAPK activates expression of egr1, one of the most commonly studied IEGs, as determined in cultured cells. We found that in the brain of naturally behaving songbirds and other avian species, hearing song, seeing visual stimuli, or performing motor behavior caused high dusp1 upregulation, respectively, in auditory, visual, and somatosensory input cell populations of the thalamus and thalamic-recipient sensory neurons of the telencephalic pallium, whereas high egr1 upregulation occurred only in subsequently connected secondary and tertiary sensory neuronal populations of these same pathways. Motor behavior did not induce high levels of dusp1 expression in the motor-associated areas adjacent to song nuclei, where egr1 is upregulated in response to movement. Our analysis of dusp1 expression in mouse brain suggests similar regulation in the sensory input neurons of the thalamus and thalamic-recipient layer IV and VI neurons of the cortex. These findings suggest that dusp1 has specialized regulation to sensory input neurons of the thalamus and telencephalon; they further suggest that this regulation may serve to attenuate stimulus-induced expression of egr1 and other IEGs, leading to unique molecular properties of forebrain sensory input neurons. PMID:20506480

Regulation of neuronal axon specification by glia-neuron gap junctions in C. elegans.

PubMed

Meng, Lingfeng; Zhang, Albert; Jin, Yishi; Yan, Dong

2016-10-21

Axon specification is a critical step in neuronal development, and the function of glial cells in this process is not fully understood. Here, we show that C. elegans GLR glial cells regulate axon specification of their nearby GABAergic RME neurons through GLR-RME gap junctions. Disruption of GLR-RME gap junctions causes misaccumulation of axonal markers in non-axonal neurites of RME neurons and converts microtubules in those neurites to form an axon-like assembly. We further uncover that GLR-RME gap junctions regulate RME axon specification through activation of the CDK-5 pathway in a calcium-dependent manner, involving a calpain clp-4 . Therefore, our study reveals the function of glia-neuron gap junctions in neuronal axon specification and shows that calcium originated from glial cells can regulate neuronal intracellular pathways through gap junctions.

Deletion of Lkb1 in pro-opiomelanocortin neurons impairs peripheral glucose homeostasis in mice.

PubMed

Claret, Marc; Smith, Mark A; Knauf, Claude; Al-Qassab, Hind; Woods, Angela; Heslegrave, Amanda; Piipari, Kaisa; Emmanuel, Julian J; Colom, André; Valet, Philippe; Cani, Patrice D; Begum, Ghazala; White, Anne; Mucket, Phillip; Peters, Marco; Mizuno, Keiko; Batterham, Rachel L; Giese, K Peter; Ashworth, Alan; Burcelin, Remy; Ashford, Michael L; Carling, David; Withers, Dominic J

2011-03-01

AMP-activated protein kinase (AMPK) signaling acts as a sensor of nutrients and hormones in the hypothalamus, thereby regulating whole-body energy homeostasis. Deletion of Ampkα2 in pro-opiomelanocortin (POMC) neurons causes obesity and defective neuronal glucose sensing. LKB1, the Peutz-Jeghers syndrome gene product, and Ca(2+)-calmodulin-dependent protein kinase kinase β (CaMKKβ) are key upstream activators of AMPK. This study aimed to determine their role in POMC neurons upon energy and glucose homeostasis regulation. Mice lacking either Camkkβ or Lkb1 in POMC neurons were generated, and physiological, electrophysiological, and molecular biology studies were performed. Deletion of Camkkβ in POMC neurons does not alter energy homeostasis or glucose metabolism. In contrast, female mice lacking Lkb1 in POMC neurons (PomcLkb1KO) display glucose intolerance, insulin resistance, impaired suppression of hepatic glucose production, and altered expression of hepatic metabolic genes. The underlying cellular defect in PomcLkb1KO mice involves a reduction in melanocortin tone caused by decreased α-melanocyte-stimulating hormone secretion. However, Lkb1-deficient POMC neurons showed normal glucose sensing, and body weight was unchanged in PomcLkb1KO mice. Our findings demonstrate that LKB1 in hypothalamic POMC neurons plays a key role in the central regulation of peripheral glucose metabolism but not body-weight control. This phenotype contrasts with that seen in mice lacking AMPK in POMC neurons with defects in body-weight regulation but not glucose homeostasis, which suggests that LKB1 plays additional functions distinct from activating AMPK in POMC neurons.

Upper intestinal lipids regulate energy and glucose homeostasis.

PubMed

Cheung, Grace W C; Kokorovic, Andrea; Lam, Tony K T

2009-09-01

Upon the entry of nutrients into the small intestine, nutrient sensing mechanisms are activated to allow the body to adapt appropriately to the incoming nutrients. To date, mounting evidence points to the existence of an upper intestinal lipid-induced gut-brain neuronal axis to regulate energy homeostasis. Moreover, a recent discovery has also revealed an upper intestinal lipid-induced gut-brain-liver neuronal axis involved in the regulation of glucose homeostasis. In this mini-review, we will focus on the mechanisms underlying the activation of these respective neuronal axes by upper intestinal lipids.

Lycopene inhibits regulator of calcineurin 1-mediated apoptosis by reducing oxidative stress and down-regulating Nucling in neuronal cells.

PubMed

Lim, Seiyoung; Hwang, Sinwoo; Yu, Ji Hoon; Lim, Joo Weon; Kim, Hyeyoung

2017-05-01

Regulator of calcineurin 1 (RCAN1) is located on the Down syndrome critical region (DSCR) locus in human chromosome 21. Oxidative stress and overexpression of RCAN1 are implicated in neuronal impairment in Down's syndrome (DS) and Alzheimer's disease (AD). Serum level of lycopene, an antioxidant pigment, is low in DS and AD patients, which may be related to neuronal damage. The present study is to investigate whether lycopene inhibits apoptosis by reducing ROS levels, NF-κB activation, expression of the apoptosis regulator Nucling, cell viability, and indices of apoptosis (cytochrome c release, caspase-3 activation) in RCAN1-overexpressing neuronal cells. Cells transfected with either pcDNA or RCAN1 were treated with or without lycopene. Lycopene decreased intracellular and mitochondrial ROS levels, NF-κB activity, and Nucling expression while it reversed decrease in mitochondrial membrane potential, mitochondrial respiration, and glycolytic function in RCAN1-overexpressing cells. Lycopene inhibited cell death, DNA fragmentation, caspase-3 activation, and cytochrome c release in RCAN1-overexpressing cells. Lycopene inhibits RCAN1-mediated apoptosis by reducing ROS levels and by inhibiting NF-κB activation, Nucling induction, and the increase in apoptotic indices in neuronal cells. Consumption of lycopene-rich foods may prevent oxidative stress-associated neuronal damage in some pathologic conditions such as DS or AD. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Neurotrophins regulate ApoER2 proteolysis through activation of the Trk signaling pathway.

PubMed

Larios, Jorge A; Jausoro, Ignacio; Benitez, Maria-Luisa; Bronfman, Francisca C; Marzolo, Maria-Paz

2014-09-19

ApoER2 and the neurotrophin receptors Trk and p75(NTR) are expressed in the CNS and regulate key functional aspects of neurons, including development, survival, and neuronal function. It is known that both ApoER2 and p75(NTR) are processed by metalloproteinases, followed by regulated intramembrane proteolysis. TrkA activation by nerve growth factor (NGF) increases the proteolytic processing of p75(NTR) mediated by ADAM17. Reelin induces the sheeding of ApoER2 ectodomain depending on metalloproteinase activity. However, it is not known if there is a common regulation mechanism for processing these receptors. We found that TrkA activation by NGF in PC12 cells induced ApoER2 processing, which was dependent on TrkA activation and metalloproteinases. NGF-induced ApoER2 proteolysis was independent of mitogen activated protein kinase activity and of phosphatidylinositol-3 kinase activity. In contrast, the basal proteolysis of ApoER2 increased when both kinases were pharmacologically inhibited. The ApoER2 ligand reelin regulated the proteolytic processing of its own receptor but not of p75(NTR). Finally, in primary cortical neurons, which express both ApoER2 and TrkB, we found that the proteolysis of ApoER2 was also regulated by brain-derived growth factor (BDNF). Our results highlight a novel relationship between neurotrophins and the reelin-ApoER2 system, suggesting that these two pathways might be linked to regulate brain development, neuronal survival, and some pathological conditions.

GDE2 regulates subtype-specific motor neuron generation through inhibition of Notch signaling.

PubMed

Sabharwal, Priyanka; Lee, Changhee; Park, Sungjin; Rao, Meenakshi; Sockanathan, Shanthini

2011-09-22

The specification of spinal interneuron and motor neuron identities initiates within progenitor cells, while motor neuron subtype diversification is regulated by hierarchical transcriptional programs implemented postmitotically. Here we find that mice lacking GDE2, a six-transmembrane protein that triggers motor neuron generation, exhibit selective losses of distinct motor neuron subtypes, specifically in defined subsets of limb-innervating motor pools that correlate with the loss of force-generating alpha motor neurons. Mechanistically, GDE2 is expressed by postmitotic motor neurons but utilizes extracellular glycerophosphodiester phosphodiesterase activity to induce motor neuron generation by inhibiting Notch signaling in neighboring motor neuron progenitors. Thus, neuronal GDE2 controls motor neuron subtype diversity through a non-cell-autonomous feedback mechanism that directly regulates progenitor cell differentiation, implying that subtype specification initiates within motor neuron progenitor populations prior to their differentiation into postmitotic motor neurons. Copyright © 2011 Elsevier Inc. All rights reserved.

GDE2 regulates subtype specific motor neuron generation through inhibition of Notch signaling

PubMed Central

Sabharwal, Priyanka; Lee, Changhee; Park, Sungjin; Rao, Meenakshi; Sockanathan, Shanthini

2011-01-01

The specification of spinal interneuron and motor neuron identities initiates within progenitor cells, while motor neuron subtype diversification is regulated by hierarchical transcriptional programs implemented postmitotically. Here, we find that mice lacking GDE2, a six-transmembrane protein that triggers motor neuron generation, exhibit selective losses of distinct motor neuron subtypes, specifically in defined subsets of limb-innervating motor pools that correlate with the loss of force-generating alpha motor neurons. Mechanistically, GDE2 is expressed by postmitotic motor neurons but utilizes extracellular glycerophosphodiester phosphodiesterase activity to induce motor neuron generation by inhibiting Notch signaling in neighboring motor neuron progenitors. Thus, neuronal GDE2 controls motor neuron subtype diversity through a non cell-autonomous feedback mechanism that directly regulates progenitor cell differentiation, implying that subtype specification initiates within motor neuron progenitor populations prior to their differentiation into postmitotic motor neurons. PMID:21943603

Evolution of Osteocrin as an activity-regulated factor in the primate brain

PubMed Central

Ataman, Bulent; Boulting, Gabriella L.; Harmin, David A.; Yang, Marty G.; Baker-Salisbury, Mollie; Yap, Ee-Lynn; Malik, Athar N.; Mei, Kevin; Rubin, Alex A.; Spiegel, Ivo; Durresi, Ershela; Sharma, Nikhil; Hu, Linda S.; Pletikos, Mihovil; Griffith, Eric C.; Partlow, Jennifer N.; Stevens, Christine R.; Adli, Mazhar; Chahrour, Maria; Sestan, Nenad; Walsh, Christopher A.; Berezovskii, Vladimir K.; Livingstone, Margaret S.; Greenberg, Michael E.

2017-01-01

Sensory stimuli drive the maturation and function of the mammalian nervous system in part through the activation of gene expression networks that regulate synapse development and plasticity. These networks have primarily been studied in mice, and it is not known whether there are species- or clade-specific activity-regulated genes that control features of brain development and function. Here we use transcriptional profiling of human fetal brain cultures to identify an activity-dependent secreted factor, Osteocrin (OSTN), that is induced by membrane depolarization of human but not mouse neurons. We find that OSTN has been repurposed in primates through the evolutionary acquisition of DNA regulatory elements that bind the activity-regulated transcription factor MEF2. In addition, we demonstrate that OSTN is expressed in primate neocortex and restricts activity-dependent dendritic growth in human neurons. These findings suggest that, in response to sensory input, OSTN regulates features of neuronal structure and function that are unique to primates. PMID:27830782

Reduced synaptic density and deficient locomotor response in neuronal activity-regulated pentraxin 2a mutant zebrafish.

PubMed

Elbaz, Idan; Lerer-Goldshtein, Tali; Okamoto, Hitoshi; Appelbaum, Lior

2015-04-01

Neuronal-activity-regulated pentraxin (NARP/NPTX2/NP2) is a secreted synaptic protein that regulates the trafficking of glutamate receptors and mediates learning, memory, and drug addiction. The role of NPTX2 in regulating structural synaptic plasticity and behavior in a developing vertebrate is indefinite. We characterized the expression of nptx2a in larvae and adult zebrafish and established a transcription activator-like effector nuclease (TALEN)-mediated nptx2a mutant (nptx2a(-/-)) to study the role of Nptx2a in regulating structural synaptic plasticity and behavior. Similar to mammals, the zebrafish nptx2a was expressed in excitatory neurons in the brain and spinal cord. Its expression was induced in response to a mechanosensory stimulus but did not change during day and night. Behavioral assays showed that loss of Nptx2a results in reduced locomotor response to light-to-dark transition states and to a sound stimulus. Live imaging of synapses using the transgenic nptx2a:GAL4VP16 zebrafish and a fluorescent presynaptic synaptophysin (SYP) marker revealed reduced synaptic density in the axons of the spinal motor neurons and the anterodorsal lateral-line ganglion (gAD), which regulate locomotor activity and locomotor response to mechanosensory stimuli, respectively. These results suggest that Nptx2a affects locomotor response to external stimuli by mediating structural synaptic plasticity in excitatory neuronal circuits. © FASEB.

Connexin-Mediated Functional and Metabolic Coupling Between Astrocytes and Neurons.

PubMed

Mayorquin, Lady C; Rodriguez, Andrea V; Sutachan, Jhon-Jairo; Albarracín, Sonia L

2018-01-01

The central nervous system (CNS) requires sophisticated regulation of neuronal activity. This modulation is partly accomplished by non-neuronal cells, characterized by the presence of transmembrane gap junctions (GJs) and hemichannels (HCs). This allows small molecule diffusion to guarantee neuronal synaptic activity and plasticity. Astrocytes are metabolically and functionally coupled to neurons by the uptake, binding and recycling of neurotransmitters. In addition, astrocytes release metabolites, such as glutamate, glutamine, D-serine, adenosine triphosphate (ATP) and lactate, regulating synaptic activity and plasticity by pre- and postsynaptic mechanisms. Uncoupling neuroglial communication leads to alterations in synaptic transmission that can be detrimental to neuronal circuit function and behavior. Therefore, understanding the pathways and mechanisms involved in this intercellular communication is fundamental for the search of new targets that can be used for several neurological disease treatments. This review will focus on molecular mechanisms mediating physiological and pathological coupling between astrocytes and neurons through GJs and HCs.

Crosstalk between p38, Hsp25 and Akt in spinal motor neurons after sciatic nerve injury

NASA Technical Reports Server (NTRS)

Murashov, A. K.; Ul Haq, I.; Hill, C.; Park, E.; Smith, M.; Wang, X.; Wang, X.; Goldberg, D. J.; Wolgemuth, D. J.

2001-01-01

The p38 stress-activated protein kinase pathway is involved in regulation of phosphorylation of Hsp25, which in turn regulates actin filament dynamic in non-neuronal cells. We report that p38, Hsp25 and Akt signaling pathways were specifically activated in spinal motor neurons after sciatic nerve axotomy. The activation of the p38 kinase was required for induction of Hsp25 expression. Furthermore, Hsp25 formed a complex with Akt, a member of PI-3 kinase pathway that prevents neuronal cell death. Together, our observations implicate Hsp25 as a central player in a complex system of signaling that may both promote regeneration of nerve fibers and prevent neuronal cell death in the injured spinal cord.

Activity-induced histone modifications govern Neurexin-1 mRNA splicing and memory preservation.

PubMed

Ding, Xinlu; Liu, Sanxiong; Tian, Miaomiao; Zhang, Wenhao; Zhu, Tao; Li, Dongdong; Wu, Jiawei; Deng, HaiTeng; Jia, Yichang; Xie, Wei; Xie, Hong; Guan, Ji-Song

2017-05-01

Epigenetic mechanisms regulate the formation, consolidation and reconsolidation of memories. However, the signaling path from neuronal activation to epigenetic modifications within the memory-related brain circuit remains unknown. We report that learning induces long-lasting histone modifications in hippocampal memory-activated neurons to regulate memory stability. Neuronal activity triggers a late-onset shift in Nrxn1 splice isoform choice at splicing site 4 by accumulating a repressive histone marker, H3K9me3, to modulate the splicing process. Activity-dependent phosphorylation of p66α via AMP-activated protein kinase recruits HDAC2 and Suv39h1 to establish repressive histone markers and changes the connectivity of the activated neurons. Removal of Suv39h1 abolished the activity-dependent shift in Nrxn1 splice isoform choice and reduced the stability of established memories. We uncover a cell-autonomous process for memory preservation in which memory-related neurons initiate a late-onset reduction of their rewiring capacities through activity-induced histone modifications.

A small potassium current in AgRP/NPY neurons regulates feeding behavior and enery metabolism

USDA-ARS?s Scientific Manuscript database

Neurons that co-express agouti-related peptide (AgRP) and neuropeptide Y (NPY) are indispensable for normal feeding behavior. Firing activities of AgRP/NPY neurons are dynamically regulated by energy status and coordinate appropriate feeding behavior to meet nutritional demands. However, intrinsic m...

YAP regulates neuronal differentiation through Sonic hedgehog signaling pathway

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Yi-Ting; Ding, Jing-Ya; Li, Ming-Yang

2012-09-10

Tight regulation of cell numbers by controlling cell proliferation and apoptosis is important during development. Recently, the Hippo pathway has been shown to regulate tissue growth and organ size in Drosophila. In mammalian cells, it also affects cell proliferation and differentiation in various tissues, including the nervous system. Interplay of several signaling cascades, such as Notch, Wnt, and Sonic Hedgehog (Shh) pathways, control cell proliferation during neuronal differentiation. However, it remains unclear whether the Hippo pathway coordinates with other signaling cascades in regulating neuronal differentiation. Here, we used P19 cells, a mouse embryonic carcinoma cell line, as a model tomore » study roles of YAP, a core component of the Hippo pathway, in neuronal differentiation. P19 cells can be induced to differentiate into neurons by expressing a neural bHLH transcription factor gene Ascl1. Our results showed that YAP promoted cell proliferation and inhibited neuronal differentiation. Expression of Yap activated Shh but not Wnt or Notch signaling activity during neuronal differentiation. Furthermore, expression of Yap increased the expression of Patched homolog 1 (Ptch1), a downstream target of the Shh signaling. Knockdown of Gli2, a transcription factor of the Shh pathway, promoted neuronal differentiation even when Yap was over-expressed. We further demonstrated that over-expression of Yap inhibited neuronal differentiation in primary mouse cortical progenitors and Gli2 knockdown rescued the differentiation defect in Yap over-expressing cells. In conclusion, our study reveals that Shh signaling acts downstream of YAP in regulating neuronal differentiation. -- Highlights: Black-Right-Pointing-Pointer YAP promotes cell proliferation and inhibits neuronal differentiation in P19 cells. Black-Right-Pointing-Pointer YAP promotes Sonic hedgehog signaling activity during neuronal differentiation. Black-Right-Pointing-Pointer Knockdown of Gli2 rescues the Yap-overexpression phenotype in P19 cells. Black-Right-Pointing-Pointer Knockdown of Gli2 rescues the Yap-overexpression phenotype in cortical progenitors.« less

Cdk5 Regulates Activity-Dependent Gene Expression and Dendrite Development.

PubMed

Liang, Zhuoyi; Ye, Tao; Zhou, Xiaopu; Lai, Kwok-On; Fu, Amy K Y; Ip, Nancy Y

2015-11-11

The proper growth and arborization of dendrites in response to sensory experience are essential for neural connectivity and information processing in the brain. Although neuronal activity is important for sculpting dendrite morphology, the underlying molecular mechanisms are not well understood. Here, we report that cyclin-dependent kinase 5 (Cdk5)-mediated transcriptional regulation is a key mechanism that controls activity-dependent dendrite development in cultured rat neurons. During membrane depolarization, Cdk5 accumulates in the nucleus to regulate the expression of a subset of genes, including that of the neurotrophin brain-derived neurotrophic factor, for subsequent dendritic growth. Furthermore, Cdk5 function is mediated through the phosphorylation of methyl-CpG-binding protein 2, a key transcriptional repressor that is mutated in the mental disorder Rett syndrome. These findings collectively suggest that the nuclear import of Cdk5 is crucial for activity-dependent dendrite development by regulating neuronal gene transcription during neural development. Neural activity directs dendrite development through the regulation of gene transcription. However, how molecular signals link extracellular stimuli to the transcriptional program in the nucleus remains unclear. Here, we demonstrate that neuronal activity stimulates the translocation of the kinase Cdk5 from the cytoplasmic compartment into the nucleus; furthermore, the nuclear localization of Cdk5 is required for dendrite development in cultured neurons. Genome-wide transcriptome analysis shows that Cdk5 deficiency specifically disrupts activity-dependent gene transcription of bdnf. The action of Cdk5 is mediated through the modulation of the transcriptional repressor methyl-CpG-binding protein 2. Therefore, this study elucidates the role of nuclear Cdk5 in the regulation of activity-dependent gene transcription and dendritic growth. Copyright © 2015 the authors 0270-6474/15/3515127-08$15.00/0.

Differential regulation of the Rac1 GTPase-activating protein (GAP) BCR during oxygen/glucose deprivation in hippocampal and cortical neurons.

PubMed

Smith, Katharine R; Rajgor, Dipen; Hanley, Jonathan G

2017-12-08

Brain ischemia causes oxygen and glucose deprivation (OGD) in neurons, triggering a cascade of events leading to synaptic accumulation of glutamate. Excessive activation of glutamate receptors causes excitotoxicity and delayed cell death in vulnerable neurons. Following global cerebral ischemia, hippocampal CA1 pyramidal neurons are more vulnerable to injury than their cortical counterparts, but the mechanisms that underlie this difference are unclear. Signaling via Rho-family small GTPases, their upstream guanine nucleotide exchange factors, and GTPase-activating proteins (GAPs) is differentially dysregulated in response to OGD/ischemia in hippocampal and cortical neurons. Increased Rac1 activity caused by OGD/ischemia contributes to neuronal death in hippocampal neurons via diverse effects on NADPH oxidase activity and dendritic spine morphology. The Rac1 guanine nucleotide exchange factor Tiam1 mediates an OGD-induced increase in Rac1 activity in hippocampal neurons; however, the identity of an antagonistic GAP remains elusive. Here we show that the Rac1 GAP breakpoint cluster region (BCR) associates with NMDA receptors (NMDARs) along with Tiam1 and that this protein complex is more abundant in hippocampal compared with cortical neurons. Although total BCR is similar in the two neuronal types, BCR is more active in hippocampal compared with cortical neurons. OGD causes an NMDAR- and Ca 2+ -permeable AMPAR-dependent deactivation of BCR in hippocampal but not cortical neurons. BCR knockdown occludes OGD-induced Rac1 activation in hippocampal neurons. Furthermore, disrupting the Tiam1-NMDAR interaction with a fragment of Tiam1 blocks OGD-induced Tiam1 activation but has no effect on the deactivation of BCR. This work identifies BCR as a critical player in Rac1 regulation during OGD in hippocampal neurons. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Basal Forebrain Gating by Somatostatin Neurons Drives Prefrontal Cortical Activity.

PubMed

Espinosa, Nelson; Alonso, Alejandra; Morales, Cristian; Espinosa, Pedro; Chávez, Andrés E; Fuentealba, Pablo

2017-11-17

The basal forebrain provides modulatory input to the cortex regulating brain states and cognitive processing. Somatostatin-expressing neurons constitute a heterogeneous GABAergic population known to functionally inhibit basal forebrain cortically projecting cells thus favoring sleep and cortical synchronization. However, it remains unclear if somatostatin cells can regulate population activity patterns in the basal forebrain and modulate cortical dynamics. Here, we demonstrate that somatostatin neurons regulate the corticopetal synaptic output of the basal forebrain impinging on cortical activity and behavior. Optogenetic inactivation of somatostatin neurons in vivo rapidly modified neural activity in the basal forebrain, with the consequent enhancement and desynchronization of activity in the prefrontal cortex, reflected in both neuronal spiking and network oscillations. Cortical activation was partially dependent on cholinergic transmission, suppressing slow waves and potentiating gamma oscillations. In addition, recruitment dynamics was cell type-specific, with interneurons showing similar temporal profiles, but stronger responses than pyramidal cells. Finally, optogenetic stimulation of quiescent animals during resting periods prompted locomotor activity, suggesting generalized cortical activation and increased arousal. Altogether, we provide physiological and behavioral evidence indicating that somatostatin neurons are pivotal in gating the synaptic output of the basal forebrain, thus indirectly controlling cortical operations via both cholinergic and non-cholinergic mechanisms. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Nerve growth factor (NGF) regulates activity of nuclear factor of activated T-cells (NFAT) in neurons via the phosphatidylinositol 3-kinase (PI3K)-Akt-glycogen synthase kinase 3β (GSK3β) pathway.

PubMed

Kim, Man-Su; Shutov, Leonid P; Gnanasekaran, Aswini; Lin, Zhihong; Rysted, Jacob E; Ulrich, Jason D; Usachev, Yuriy M

2014-11-07

The Ca(2+)/calcineurin-dependent transcription factor nuclear factor of activated T-cells (NFAT) plays an important role in regulating many neuronal functions, including excitability, axonal growth, synaptogenesis, and neuronal survival. NFAT can be activated by action potential firing or depolarization that leads to Ca(2+)/calcineurin-dependent dephosphorylation of NFAT and its translocation to the nucleus. Recent data suggest that NFAT and NFAT-dependent functions in neurons can also be potently regulated by NGF and other neurotrophins. However, the mechanisms of NFAT regulation by neurotrophins are not well understood. Here, we show that in dorsal root ganglion sensory neurons, NGF markedly facilitates NFAT-mediated gene expression induced by mild depolarization. The effects of NGF were not associated with changes in [Ca(2+)]i and were independent of phospholipase C activity. Instead, the facilitatory effect of NGF depended on activation of the PI3K/Akt pathway downstream of the TrkA receptor and on inhibition of glycogen synthase kinase 3β (GSK3β), a protein kinase known to phosphorylate NFAT and promote its nuclear export. Knockdown or knockout of NFATc3 eliminated this facilitatory effect. Simultaneous monitoring of EGFP-NFATc3 nuclear translocation and [Ca(2+)]i changes in dorsal root ganglion neurons indicated that NGF slowed the rate of NFATc3 nuclear export but did not affect its nuclear import rate. Collectively, our data suggest that NGF facilitates depolarization-induced NFAT activation by stimulating PI3K/Akt signaling, inactivating GSK3β, and thereby slowing NFATc3 export from the nucleus. We propose that NFAT serves as an integrator of neurotrophin action and depolarization-driven calcium signaling to regulate neuronal gene expression. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

Nerve Growth Factor (NGF) Regulates Activity of Nuclear Factor of Activated T-cells (NFAT) in Neurons via the Phosphatidylinositol 3-Kinase (PI3K)-Akt-Glycogen Synthase Kinase 3β (GSK3β) Pathway*

PubMed Central

Kim, Man-Su; Shutov, Leonid P.; Gnanasekaran, Aswini; Lin, Zhihong; Rysted, Jacob E.; Ulrich, Jason D.; Usachev, Yuriy M.

2014-01-01

The Ca2+/calcineurin-dependent transcription factor nuclear factor of activated T-cells (NFAT) plays an important role in regulating many neuronal functions, including excitability, axonal growth, synaptogenesis, and neuronal survival. NFAT can be activated by action potential firing or depolarization that leads to Ca2+/calcineurin-dependent dephosphorylation of NFAT and its translocation to the nucleus. Recent data suggest that NFAT and NFAT-dependent functions in neurons can also be potently regulated by NGF and other neurotrophins. However, the mechanisms of NFAT regulation by neurotrophins are not well understood. Here, we show that in dorsal root ganglion sensory neurons, NGF markedly facilitates NFAT-mediated gene expression induced by mild depolarization. The effects of NGF were not associated with changes in [Ca2+]i and were independent of phospholipase C activity. Instead, the facilitatory effect of NGF depended on activation of the PI3K/Akt pathway downstream of the TrkA receptor and on inhibition of glycogen synthase kinase 3β (GSK3β), a protein kinase known to phosphorylate NFAT and promote its nuclear export. Knockdown or knockout of NFATc3 eliminated this facilitatory effect. Simultaneous monitoring of EGFP-NFATc3 nuclear translocation and [Ca2+]i changes in dorsal root ganglion neurons indicated that NGF slowed the rate of NFATc3 nuclear export but did not affect its nuclear import rate. Collectively, our data suggest that NGF facilitates depolarization-induced NFAT activation by stimulating PI3K/Akt signaling, inactivating GSK3β, and thereby slowing NFATc3 export from the nucleus. We propose that NFAT serves as an integrator of neurotrophin action and depolarization-driven calcium signaling to regulate neuronal gene expression. PMID:25231981

Regulation of the Proteasome by Neuronal Activity and Calcium/Calmodulin-dependent Protein Kinase II*

PubMed Central

Djakovic, Stevan N.; Schwarz, Lindsay A.; Barylko, Barbara; DeMartino, George N.; Patrick, Gentry N.

2009-01-01

Protein degradation via the ubiquitin proteasome system has been shown to regulate changes in synaptic strength that underlie multiple forms of synaptic plasticity. It is plausible, therefore, that the ubiquitin proteasome system is itself regulated by synaptic activity. By utilizing live-cell imaging strategies we report the rapid and dynamic regulation of the proteasome in hippocampal neurons by synaptic activity. We find that the blockade of action potentials (APs) with tetrodotoxin inhibited the activity of the proteasome, whereas the up-regulation of APs with bicuculline dramatically increased the activity of the proteasome. In addition, the regulation of the proteasome is dependent upon external calcium entry in part through N-methyl-d-aspartate receptors and L-type voltage-gated calcium channels and requires the activity of calcium/calmodulin-dependent protein kinase II (CaMKII). Using in vitro and in vivo assays we find that CaMKII stimulates proteasome activity and directly phosphorylates Rpt6, a subunit of the 19 S (PA700) subcomplex of the 26 S proteasome. Our data provide a novel mechanism whereby CaMKII may regulate the proteasome in neurons to facilitate remodeling of synaptic connections through protein degradation. PMID:19638347

Regulation of the proteasome by neuronal activity and calcium/calmodulin-dependent protein kinase II.

PubMed

Djakovic, Stevan N; Schwarz, Lindsay A; Barylko, Barbara; DeMartino, George N; Patrick, Gentry N

2009-09-25

Protein degradation via the ubiquitin proteasome system has been shown to regulate changes in synaptic strength that underlie multiple forms of synaptic plasticity. It is plausible, therefore, that the ubiquitin proteasome system is itself regulated by synaptic activity. By utilizing live-cell imaging strategies we report the rapid and dynamic regulation of the proteasome in hippocampal neurons by synaptic activity. We find that the blockade of action potentials (APs) with tetrodotoxin inhibited the activity of the proteasome, whereas the up-regulation of APs with bicuculline dramatically increased the activity of the proteasome. In addition, the regulation of the proteasome is dependent upon external calcium entry in part through N-methyl-D-aspartate receptors and L-type voltage-gated calcium channels and requires the activity of calcium/calmodulin-dependent protein kinase II (CaMKII). Using in vitro and in vivo assays we find that CaMKII stimulates proteasome activity and directly phosphorylates Rpt6, a subunit of the 19 S (PA700) subcomplex of the 26 S proteasome. Our data provide a novel mechanism whereby CaMKII may regulate the proteasome in neurons to facilitate remodeling of synaptic connections through protein degradation.

A hypothalamic circuit for the circadian control of aggression.

PubMed

Todd, William D; Fenselau, Henning; Wang, Joshua L; Zhang, Rong; Machado, Natalia L; Venner, Anne; Broadhurst, Rebecca Y; Kaur, Satvinder; Lynagh, Timothy; Olson, David P; Lowell, Bradford B; Fuller, Patrick M; Saper, Clifford B

2018-05-01

'Sundowning' in dementia and Alzheimer's disease is characterized by early-evening agitation and aggression. While such periodicity suggests a circadian origin, whether the circadian clock directly regulates aggressive behavior is unknown. We demonstrate that a daily rhythm in aggression propensity in male mice is gated by GABAergic subparaventricular zone (SPZ GABA ) neurons, the major postsynaptic targets of the central circadian clock, the suprachiasmatic nucleus. Optogenetic mapping revealed that SPZ GABA neurons receive input from vasoactive intestinal polypeptide suprachiasmatic nucleus neurons and innervate neurons in the ventrolateral part of the ventromedial hypothalamus (VMH), which is known to regulate aggression. Additionally, VMH-projecting dorsal SPZ neurons are more active during early day than early night, and acute chemogenetic inhibition of SPZ GABA transmission phase-dependently increases aggression. Finally, SPZ GABA -recipient central VMH neurons directly innervate ventrolateral VMH neurons, and activation of this intra-VMH circuit drove attack behavior. Altogether, we reveal a functional polysynaptic circuit by which the suprachiasmatic nucleus clock regulates aggression.

I(A) channels encoded by Kv1.4 and Kv4.2 regulate neuronal firing in the suprachiasmatic nucleus and circadian rhythms in locomotor activity.

PubMed

Granados-Fuentes, Daniel; Norris, Aaron J; Carrasquillo, Yarimar; Nerbonne, Jeanne M; Herzog, Erik D

2012-07-18

Neurons in the suprachiasmatic nucleus (SCN) display coordinated circadian changes in electrical activity that are critical for daily rhythms in physiology, metabolism, and behavior. SCN neurons depolarize spontaneously and fire repetitively during the day and hyperpolarize, drastically reducing firing rates, at night. To explore the hypothesis that rapidly activating and inactivating A-type (I(A)) voltage-gated K(+) (Kv) channels, which are also active at subthreshold membrane potentials, are critical regulators of the excitability of SCN neurons, we examined locomotor activity and SCN firing in mice lacking Kv1.4 (Kv1.4(-/-)), Kv4.2 (Kv4.2(-/-)), or Kv4.3 (Kv4.3(-/-)), the pore-forming (α) subunits of I(A) channels. Mice lacking either Kv1.4 or Kv4.2 α subunits have markedly shorter (0.5 h) periods of locomotor activity than wild-type (WT) mice. In vitro extracellular multi-electrode recordings revealed that Kv1.4(-/-) and Kv4.2(-/-) SCN neurons display circadian rhythms in repetitive firing, but with shorter periods (0.5 h) than WT cells. In contrast, the periods of wheel-running activity in Kv4.3(-/-) mice and firing in Kv4.3(-/-) SCN neurons were indistinguishable from WT animals and neurons. Quantitative real-time PCR revealed that the transcripts encoding all three Kv channel α subunits, Kv1.4, Kv4.2, and Kv4.3, are expressed constitutively throughout the day and night in the SCN. Together, these results demonstrate that Kv1.4- and Kv4.2-encoded I(A) channels regulate the intrinsic excitability of SCN neurons during the day and night and determine the period and amplitude of circadian rhythms in SCN neuron firing and locomotor behavior.

Active dendrites regulate the impact of gliotransmission on rat hippocampal pyramidal neurons

PubMed Central

Ashhad, Sufyan

2016-01-01

An important consequence of gliotransmission, a signaling mechanism that involves glial release of active transmitter molecules, is its manifestation as N-methyl-d-aspartate receptor (NMDAR)-dependent slow inward currents in neurons. However, the intraneuronal spatial dynamics of these events or the role of active dendrites in regulating their amplitude and spatial spread have remained unexplored. Here, we used somatic and/or dendritic recordings from rat hippocampal pyramidal neurons and demonstrate that a majority of NMDAR-dependent spontaneous slow excitatory potentials (SEP) originate at dendritic locations and are significantly attenuated through their propagation across the neuronal arbor. We substantiated the astrocytic origin of SEPs through paired neuron–astrocyte recordings, where we found that specific infusion of inositol trisphosphate (InsP3) into either distal or proximal astrocytes enhanced the amplitude and frequency of neuronal SEPs. Importantly, SEPs recorded after InsP3 infusion into distal astrocytes exhibited significantly slower kinetics compared with those recorded after proximal infusion. Furthermore, using neuron-specific infusion of pharmacological agents and morphologically realistic conductance-based computational models, we demonstrate that dendritically expressed hyperpolarization-activated cyclic-nucleotide–gated (HCN) and transient potassium channels play critical roles in regulating the strength, kinetics, and compartmentalization of neuronal SEPs. Finally, through the application of subtype-specific receptor blockers during paired neuron–astrocyte recordings, we provide evidence that GluN2B- and GluN2D-containing NMDARs predominantly mediate perisomatic and dendritic SEPs, respectively. Our results unveil an important role for active dendrites in regulating the impact of gliotransmission on neurons and suggest astrocytes as a source of dendritic plateau potentials that have been implicated in localized plasticity and place cell formation. PMID:27217559

The interplay of microRNA and neuronal activity in health and disease

PubMed Central

Eacker, Stephen M.; Dawson, Ted M.; Dawson, Valina L.

2013-01-01

MicroRNAs (miRNAs) are small 19–23 nucleotide regulatory RNAs that function by modulating mRNA translation and/or turnover in a sequence-specific fashion. In the nervous system, miRNAs regulate the production of numerous proteins involved in synaptic transmission. In turn, neuronal activity can regulate the production and turnover of miRNA through a variety of mechanisms. In this way, miRNAs and neuronal activity are in a reciprocal homeostatic relationship that balances neuronal function. The miRNA function is critical in pathological states related to overexcitation such as epilepsy and stroke, suggesting miRNA’s potential as a therapeutic target. We review the current literature relating the interplay of miRNA and neuronal activity and provide future directions for defining miRNA’s role in disease. PMID:23986658

Human embryonic stem cell-derived neurons adopt and regulate the activity of an established neural network

PubMed Central

Weick, Jason P.; Liu, Yan; Zhang, Su-Chun

2011-01-01

Whether hESC-derived neurons can fully integrate with and functionally regulate an existing neural network remains unknown. Here, we demonstrate that hESC-derived neurons receive unitary postsynaptic currents both in vitro and in vivo and adopt the rhythmic firing behavior of mouse cortical networks via synaptic integration. Optical stimulation of hESC-derived neurons expressing Channelrhodopsin-2 elicited both inhibitory and excitatory postsynaptic currents and triggered network bursting in mouse neurons. Furthermore, light stimulation of hESC-derived neurons transplanted to the hippocampus of adult mice triggered postsynaptic currents in host pyramidal neurons in acute slice preparations. Thus, hESC-derived neurons can participate in and modulate neural network activity through functional synaptic integration, suggesting they are capable of contributing to neural network information processing both in vitro and in vivo. PMID:22106298

Speed and segmentation control mechanisms characterized in rhythmically-active circuits created from spinal neurons produced from genetically-tagged embryonic stem cells

PubMed Central

Sternfeld, Matthew J; Hinckley, Christopher A; Moore, Niall J; Pankratz, Matthew T; Hilde, Kathryn L; Driscoll, Shawn P; Hayashi, Marito; Amin, Neal D; Bonanomi, Dario; Gifford, Wesley D; Sharma, Kamal; Goulding, Martyn; Pfaff, Samuel L

2017-01-01

Flexible neural networks, such as the interconnected spinal neurons that control distinct motor actions, can switch their activity to produce different behaviors. Both excitatory (E) and inhibitory (I) spinal neurons are necessary for motor behavior, but the influence of recruiting different ratios of E-to-I cells remains unclear. We constructed synthetic microphysical neural networks, called circuitoids, using precise combinations of spinal neuron subtypes derived from mouse stem cells. Circuitoids of purified excitatory interneurons were sufficient to generate oscillatory bursts with properties similar to in vivo central pattern generators. Inhibitory V1 neurons provided dual layers of regulation within excitatory rhythmogenic networks - they increased the rhythmic burst frequency of excitatory V3 neurons, and segmented excitatory motor neuron activity into sub-networks. Accordingly, the speed and pattern of spinal circuits that underlie complex motor behaviors may be regulated by quantitatively gating the intra-network cellular activity ratio of E-to-I neurons. DOI: http://dx.doi.org/10.7554/eLife.21540.001 PMID:28195039

JNK1 regulates histone acetylation in trigeminal neurons following chemical stimulation

PubMed Central

Wu, Jing; Zhang, Xuan; Nauta, Haring J; Lin, Qing; Li, Junfa; Fang, Li

2008-01-01

Trigeminal nerve fibers in nasal and oral cavities are sensitive to various environmental hazardous stimuli, which trigger many neurotoxic problems such as chronic migraine headache and trigeminal irritated disorders. However, the role of JNK kinase cascade and its epigenetic modulation of histone remodeling in trigeminal ganglion (TG) neurons activated by environmental neurotoxins remains unknown. Here we investigated the role of JNK/c-Jun cascade in the regulation of acetylation of H3 histone in TG neurons following in vitro stimulation by a neuro-inflammatory agent, mustard oil (MO). We found that MO stimulation elicited JNK/c-Jun pathway significantly by enhancing phospho-JNK1, phospho-c-Jun expression, and c-Jun activity, which were correlated with an elevated acetylated H3 histone in TG neurons. However, increases in phospho-c-Jun and c-Jun activity were significantly blocked by a JNK inhibitor, SP600125. We also found that altered H3 histone remodeling, assessed by H3 acetylation in triggered TG neurons, was reduced by SP600125. The study suggests that the activated JNK signaling in regulation of histone remodeling may contribute to neuro-epigentic changes in peripheral sensory neurons following environmental neurotoxic exposure. PMID:18822271

Activation of Tyrosine Hydroxylase mRNA Translation by cAMP in Midbrain Dopaminergic Neurons

PubMed Central

Chen, Xiqun; Xu, Lu; Radcliffe, Pheona; Sun, Baoyong; Tank, A. William

2009-01-01

During prolonged stress or chronic treatment with neurotoxins, robust compensatory mechanisms occur which maintain sufficient levels of catecholamine neurotransmitters in terminal regions. One of these mechanisms is the up-regulation of tyrosine hydroxylase (TH), the enzyme that controls catecholamine biosynthesis. In neurons of the periphery and locus coeruleus, this up-regulation is associated with an initial induction of TH mRNA. In contrast, this induction either does not occur or is nominal in mesencephalic dopamine neurons. The reasons for this lack of compensatory TH mRNA induction remain obscure, because so little is known about the regulation of TH expression in these neurons. In this report we test whether activation of the cAMP signaling pathway regulates TH gene expression in two rodent models of midbrain dopamine neurons, ventral midbrain organotypic slice cultures and MN9D cells. Our results demonstrate that elevation of cAMP leads to induction of TH protein and TH activity in both model systems; however, TH mRNA levels are not up-regulated by cAMP. The induction of TH protein is the result of a novel post-transcriptional mechanism that activates TH mRNA translation. This translational activation is mediated by sequences within the 3′UTR of TH mRNA. Our results support a model in which cAMP induces or activates trans-factors that interact with the TH mRNA 3′UTR to increase TH protein synthesis. An understanding of this novel regulatory mechanism may help to explain the control of TH gene expression and consequently dopamine biosynthesis in midbrain neurons under different physiological and pathological conditions. PMID:18349104

Genetic ablation of hypocretin neurons alters behavioral state transitions in zebrafish.

PubMed

Elbaz, Idan; Yelin-Bekerman, Laura; Nicenboim, Julian; Vatine, Gad; Appelbaum, Lior

2012-09-12

Sleep is an essential biological need of all animals studied to date. The sleep disorder narcolepsy is characterized by excessive daytime sleepiness, fragmentation of nighttime sleep, and cataplexy. Narcolepsy is caused by selective degeneration of hypothalamic hypocretin/orexin (HCRT) neurons. In mammals, HCRT neurons primarily regulate the sleep/wake cycle, feeding, reward-seeking, and addiction. The role of HCRT neurons in zebrafish is implicated in both sleep and wake regulation. We established a transgenic zebrafish model enabling inducible ablation of HCRT neurons and used these animals to understand the function of HCRT neurons and narcolepsy. Loss of HCRT neurons increased the expression of the HCRT receptor (hcrtr). Behavioral assays revealed that HCRT neuron-ablated larvae had normal locomotor activity, but demonstrated an increase in sleep time during the day and an increased number of sleep/wake transitions during both day and night. Mild sleep disturbance reduced sleep and increased c-fos expression in HCRT neuron-ablated larvae. Furthermore, ablation of HCRT neurons altered the behavioral response to external stimuli. Exposure to light during the night decreased locomotor activity of wild-type siblings, but induced an opposite response in HCRT neuron-ablated larvae. Sound stimulus during the day reduced the locomotor activity of wild-type sibling larvae, while HCRT neuron-ablated larvae demonstrated a hyposensitive response. This study establishes zebrafish as a model for narcolepsy, and indicating a role of HCRT neurons in regulation of sleep/wake transitions during both day and night. Our results further suggest a key role of HCRT neurons in mediating behavioral state transitions in response to external stimuli.

Deletion of Lkb1 in Pro-Opiomelanocortin Neurons Impairs Peripheral Glucose Homeostasis in Mice

PubMed Central

Claret, Marc; Smith, Mark A.; Knauf, Claude; Al-Qassab, Hind; Woods, Angela; Heslegrave, Amanda; Piipari, Kaisa; Emmanuel, Julian J.; Colom, André; Valet, Philippe; Cani, Patrice D.; Begum, Ghazala; White, Anne; Mucket, Phillip; Peters, Marco; Mizuno, Keiko; Batterham, Rachel L.; Giese, K. Peter; Ashworth, Alan; Burcelin, Remy; Ashford, Michael L.; Carling, David; Withers, Dominic J.

2011-01-01

OBJECTIVE AMP-activated protein kinase (AMPK) signaling acts as a sensor of nutrients and hormones in the hypothalamus, thereby regulating whole-body energy homeostasis. Deletion of Ampkα2 in pro-opiomelanocortin (POMC) neurons causes obesity and defective neuronal glucose sensing. LKB1, the Peutz-Jeghers syndrome gene product, and Ca2+-calmodulin–dependent protein kinase kinase β (CaMKKβ) are key upstream activators of AMPK. This study aimed to determine their role in POMC neurons upon energy and glucose homeostasis regulation. RESEARCH DESIGN AND METHODS Mice lacking either Camkkβ or Lkb1 in POMC neurons were generated, and physiological, electrophysiological, and molecular biology studies were performed. RESULTS Deletion of Camkkβ in POMC neurons does not alter energy homeostasis or glucose metabolism. In contrast, female mice lacking Lkb1 in POMC neurons (PomcLkb1KO) display glucose intolerance, insulin resistance, impaired suppression of hepatic glucose production, and altered expression of hepatic metabolic genes. The underlying cellular defect in PomcLkb1KO mice involves a reduction in melanocortin tone caused by decreased α-melanocyte–stimulating hormone secretion. However, Lkb1-deficient POMC neurons showed normal glucose sensing, and body weight was unchanged in PomcLkb1KO mice. CONCLUSIONS Our findings demonstrate that LKB1 in hypothalamic POMC neurons plays a key role in the central regulation of peripheral glucose metabolism but not body-weight control. This phenotype contrasts with that seen in mice lacking AMPK in POMC neurons with defects in body-weight regulation but not glucose homeostasis, which suggests that LKB1 plays additional functions distinct from activating AMPK in POMC neurons. PMID:21266325

Effects of PTEN inhibition on the regulation of Tau phosphorylation in rat cortical neuronal injury after oxygen and glucose deprivation.

PubMed

Zhao, Jing; Chen, Yurong; Xu, Yuxia; Pi, Guanghuan

2016-01-01

This report investigated the involvement of the PTEN pathway in the regulation of Tau phosphorylation using an oxygen and glucose deprivation (OGD) model with rat cortical neurons. Primary cortical neurons were used to establish the oxygen and glucose deprivation (OGD) model in vitro. These were randomly divided into control, OGD, bpV+OGD, As+OGD, Se+OGD and Mock treatment groups. The neuron viability was assessed by MTT, the cell apoptosis was detected using TUNEL staining. The expression of Phospho-PTEN/PTEN, Phospho-Tau/Tau, Phospho-Akt/Akt and Phospho-GSK-3β/GSK-3β were detected by Western blotting. OGD induced Tau phosphorylation through PTEN and glycogen synthase kinase-3β (GSK-3β) activation, together with a decrease in AKT activity. Pre-treatment with bpv, a potent PTEN inhibitor, and PTEN antisense nucleotides decreased PTEN and GSK-3β activity and caused alterations in Tau phosphorylation. Neuronal apoptosis was also reduced. The PTEN/Akt/GSK-3β/Tau pathway is involved in the regulation of neuronal injury, providing a novel route for protecting neurons following neonatal HI.

Negative regulation of neuronal cell differentiation by INHAT subunit SET/TAF-Iβ.

PubMed

Kim, Dong-Wook; Kim, Kee-Beom; Kim, Ji-Young; Lee, Kyu-Sun; Seo, Sang-Beom

2010-09-24

Epigenetic modification plays an important role in transcriptional regulation. As a subunit of the INHAT (inhibitor of histone acetyltransferases) complex, SET/TAF-Iβ evidences transcriptional repression activity. In this study, we demonstrate that SET/TAF-Iβ is abundantly expressed in neuronal tissues of Drosophila embryos. It is expressed at high levels prior to and in early stages of neuronal development, and gradually reduced as differentiation proceeds. SET/TAF-Iβ binds to the promoters of a subset of neuronal development markers and negatively regulates the transcription of these genes. The results of this study show that the knockdown of SET/TAF-Iβ by si-RNA induces neuronal cell differentiation, thus implicating SET/TAF-Iβ as a negative regulator of neuronal development. Copyright © 2010 Elsevier Inc. All rights reserved.

Miro1 Regulates Activity-Driven Positioning of Mitochondria within Astrocytic Processes Apposed to Synapses to Regulate Intracellular Calcium Signaling

PubMed Central

Stephen, Terri-Leigh; Higgs, Nathalie F.; Sheehan, David F.; Al Awabdh, Sana; López-Doménech, Guillermo; Arancibia-Carcamo, I. Lorena

2015-01-01

It is fast emerging that maintaining mitochondrial function is important for regulating astrocyte function, although the specific mechanisms that govern astrocyte mitochondrial trafficking and positioning remain poorly understood. The mitochondrial Rho-GTPase 1 protein (Miro1) regulates mitochondrial trafficking and detachment from the microtubule transport network to control activity-dependent mitochondrial positioning in neurons. However, whether Miro proteins are important for regulating signaling-dependent mitochondrial dynamics in astrocytic processes remains unclear. Using live-cell confocal microscopy of rat organotypic hippocampal slices, we find that enhancing neuronal activity induces transient mitochondrial remodeling in astrocytes, with a concomitant, transient reduction in mitochondrial trafficking, mediated by elevations in intracellular Ca2+. Stimulating neuronal activity also induced mitochondrial confinement within astrocytic processes in close proximity to synapses. Furthermore, we show that the Ca2+-sensing EF-hand domains of Miro1 are important for regulating mitochondrial trafficking in astrocytes and required for activity-driven mitochondrial confinement near synapses. Additionally, activity-dependent mitochondrial positioning by Miro1 reciprocally regulates the levels of intracellular Ca2+ in astrocytic processes. Thus, the regulation of intracellular Ca2+ signaling, dependent on Miro1-mediated mitochondrial positioning, could have important consequences for astrocyte Ca2+ wave propagation, gliotransmission, and ultimately neuronal function. SIGNIFICANCE STATEMENT Mitochondria are key cellular organelles that play important roles in providing cellular energy and buffering intracellular calcium ions. The mechanisms that control mitochondrial distribution within the processes of glial cells called astrocytes and the impact this may have on calcium signaling remains unclear. We show that activation of glutamate receptors or increased neuronal activity leads to the altered transport of mitochondria and their positioning at synapses dependent on a key mitochondrial trafficking protein called Miro1. We also show that, the control of mitochondrial movement and stopping by Miro plays an important role in regulating astrocyte calcium responses. Thus the regulation of intracellular calcium signaling, by Miro-mediated mitochondrial positioning, could have important consequences for astrocyte signaling and neuron–glial interactions. PMID:26631479

Regulator of G protein signaling 5 (RGS5) inhibits sonic hedgehog function in mouse cortical neurons.

PubMed

Liu, Chuanliang; Hu, Qiongqiong; Jing, Jia; Zhang, Yun; Jin, Jing; Zhang, Liulei; Mu, Lili; Liu, Yumei; Sun, Bo; Zhang, Tongshuai; Kong, Qingfei; Wang, Guangyou; Wang, Dandan; Zhang, Yao; Liu, Xijun; Zhao, Wei; Wang, Jinghua; Feng, Tao; Li, Hulun

2017-09-01

Regulator of G protein signaling 5 (RGS5) acts as a GTPase-activating protein (GAP) for the Gαi subunit and negatively regulates G protein-coupled receptor signaling. However, its presence and function in postmitotic differentiated primary neurons remains largely uncharacterized. During neural development, sonic hedgehog (Shh) signaling is involved in cell signaling pathways via Gαi activity. In particular, Shh signaling is essential for embryonic neural tube patterning, which has been implicated in neuronal polarization involving neurite outgrowth. Here, we examined whether RGS5 regulates Shh signaling in neurons. RGS5 transcripts were found to be expressed in cortical neurons and their expression gradually declined in a time-dependent manner in culture system. When an adenovirus expressing RGS5 was introduced into an in vitro cell culture model of cortical neurons, RGS5 overexpression significantly reduced neurite outgrowth and FM4-64 uptake, while cAMP-PKA signaling was also affected. These findings suggest that RGS5 inhibits Shh function during neurite outgrowth and the presynaptic terminals of primary cortical neurons mature via modulation of cAMP. Copyright © 2017 Elsevier Inc. All rights reserved.

Nuclear BK Channels Regulate Gene Expression via the Control of Nuclear Calcium Signaling

PubMed Central

Li, Boxing; Jie, Wei; Huang, Lianyan; Wei, Peng; Li, Shuji; Luo, Zhengyi; Friedman, Allyson K.; Meredith, Andrea L.; Han, Ming-Hu; Zhu, Xin-Hong; Gao, Tian-Ming

2014-01-01

Ion channels are essential for the regulation of neuronal functions. The significance of plasma membrane, mitochondrial, endoplasmic reticulum, and lysosomal ion channels in the regulation of Ca2+ is well established. In contrast, surprisingly less is known about the function of ion channels on the nuclear envelope (NE). Here we demonstrate the presence of functional large-conductance, calcium-activated potassium channels (BK channels) on the NE of rodent hippocampal neurons. Functionally blockade of nuclear BK channels (nBK channels) induces NE-derived Ca2+ release, nucleoplasmic Ca2+ elevation, and cAMP response element binding protein (CREB)-dependent transcription. More importantly, blockade of nBK channels regulates nuclear Ca2+-sensitive gene expression and promotes dendritic arborization in a nuclear Ca2+-dependent manner. These results suggest that nBK channel functions as a molecular linker between neuronal activity and nuclear Ca2+ to convey the signals from synapse to nucleus and is a new modulator for synaptic activity-dependent neuronal functions at the NE level. PMID:24952642

A Distributed Chemosensory Circuit for Oxygen Preference in C. elegans

PubMed Central

Chang, Andy J; Chronis, Nikolas; Karow, David S; Marletta, Michael A; Bargmann, Cornelia I

2006-01-01

The nematode Caenorhabditis elegans has complex, naturally variable behavioral responses to environmental oxygen, food, and other animals. C. elegans detects oxygen through soluble guanylate cyclase homologs (sGCs) and responds to it differently depending on the activity of the neuropeptide receptor NPR-1: npr-1(lf) and naturally isolated npr-1(215F) animals avoid high oxygen and aggregate in the presence of food; npr-1(215V) animals do not. We show here that hyperoxia avoidance integrates food with npr-1 activity through neuromodulation of a distributed oxygen-sensing network. Hyperoxia avoidance is stimulated by sGC-expressing oxygen-sensing neurons, nociceptive neurons, and ADF sensory neurons. In npr-1(215V) animals, the switch from weak aerotaxis on food to strong aerotaxis in its absence requires close regulation of the neurotransmitter serotonin in the ADF neurons; high levels of ADF serotonin promote hyperoxia avoidance. In npr-1(lf) animals, food regulation is masked by increased activity of the oxygen-sensing neurons. Hyperoxia avoidance is also regulated by the neuronal TGF-β homolog DAF-7, a secreted mediator of crowding and stress responses. DAF-7 inhibits serotonin synthesis in ADF, suggesting that ADF serotonin is a convergence point for regulation of hyperoxia avoidance. Coalitions of neurons that promote and repress hyperoxia avoidance generate a subtle and flexible response to environmental oxygen. PMID:16903785

A frightening thought: Neuronal activity enhances tumor growth.

PubMed

Thompson, Emily G; Sontheimer, Harald

2015-08-01

Stem cells present in the adult brain are regulated by neuronal activity; malignant gliomas, which most likely originate from this population of cells, could also be regulated in this manner. A recent study by Venkatesh et al. published in Cell has identified Neuroligin-3 (NLGN3) as a mitogen promoting high-grade glioma growth.

Transcriptional activation of human mu-opioid receptor gene by insulin-like growth factor-I in neuronal cells is modulated by the transcription factor REST.

PubMed

Bedini, Andrea; Baiula, Monica; Spampinato, Santi

2008-06-01

The human mu-opioid receptor gene (OPRM1) promoter contains a DNA sequence binding the repressor element 1 silencing transcription factor (REST) that is implicated in transcriptional repression. We investigated whether insulin-like growth factor I (IGF-I), which affects various aspects of neuronal induction and maturation, regulates OPRM1 transcription in neuronal cells in the context of the potential influence of REST. A series of OPRM1-luciferase promoter/reporter constructs were transfected into two neuronal cell models, neuroblastoma-derived SH-SY5Y cells and PC12 cells. In the former, endogenous levels of human mu-opioid receptor (hMOPr) mRNA were evaluated by real-time PCR. IGF-I up-regulated OPRM1 transcription in: PC12 cells lacking REST, in SH-SY5Y cells transfected with constructs deficient in the REST DNA binding element, or when REST was down-regulated in retinoic acid-differentiated cells. IGF-I activates the signal transducer and activator of transcription-3 signaling pathway and this transcription factor, binding to the signal transducer and activator of transcription-1/3 DNA element located in the promoter, increases OPRM1 transcription. We propose that a reduction in REST is a critical switch enabling IGF-I to up-regulate hMOPr. These findings help clarify how hMOPr expression is regulated in neuronal cells.

Coordinated activation of AMP-activated protein kinase, extracellular signal-regulated kinase, and autophagy regulates phorbol myristate acetate-induced differentiation of SH-SY5Y neuroblastoma cells.

PubMed

Zogovic, Nevena; Tovilovic-Kovacevic, Gordana; Misirkic-Marjanovic, Maja; Vucicevic, Ljubica; Janjetovic, Kristina; Harhaji-Trajkovic, Ljubica; Trajkovic, Vladimir

2015-04-01

We explored the interplay between the intracellular energy sensor AMP-activated protein kinase (AMPK), extracellular signal-regulated kinase (ERK), and autophagy in phorbol myristate acetate (PMA)-induced neuronal differentiation of SH-SY5Y human neuroblastoma cells. PMA-triggered expression of neuronal markers (dopamine transporter, microtubule-associated protein 2, β-tubulin) was associated with an autophagic response, measured by the conversion of microtubule-associated protein light chain 3 (LC3)-I to autophagosome-bound LC3-II, increase in autophagic flux, and expression of autophagy-related (Atg) proteins Atg7 and beclin-1. This coincided with the transient activation of AMPK and sustained activation of ERK. Pharmacological inhibition or RNA interference-mediated silencing of AMPK suppressed PMA-induced expression of neuronal markers, as well as ERK activation and autophagy. A selective pharmacological blockade of ERK prevented PMA-induced neuronal differentiation and autophagy induction without affecting AMPK phosphorylation. Conversely, the inhibition of autophagy downstream of AMPK/ERK, either by pharmacological agents or LC3 knockdown, promoted the expression of neuronal markers, thus indicating a role of autophagy in the suppression of PMA-induced differentiation of SH-SY5Y cells. Therefore, PMA-induced neuronal differentiation of SH-SY5Y cells depends on a complex interplay between AMPK, ERK, and autophagy, in which the stimulatory effects of AMPK/ERK signaling are counteracted by the coinciding autophagic response. Phorbol myristate acetate (PMA) induces the expression of dopamine transporter, microtubule-associated protein 2, and β-tubulin, and subsequent neuronal differentiation of SH-SY5Y neuroblastoma cells through AMP-activated protein kinase (AMPK)-dependent activation of extracellular signal-regulated kinase (ERK). The activation of AMPK/ERK axis also induces the expression of beclin-1 and Atg7, and increases LC3 conversion, thereby triggering the autophagic response that counteracts differentiation process. © 2014 International Society for Neurochemistry.

GSK3 temporally regulates neurogenin 2 proneural activity in the neocortex.

PubMed

Li, Saiqun; Mattar, Pierre; Zinyk, Dawn; Singh, Kulwant; Chaturvedi, Chandra-Prakash; Kovach, Christopher; Dixit, Rajiv; Kurrasch, Deborah M; Ma, Yong-Chao; Chan, Jennifer A; Wallace, Valerie; Dilworth, F Jeffrey; Brand, Marjorie; Schuurmans, Carol

2012-06-06

The neocortex is comprised of six neuronal layers that are generated in a defined temporal sequence. While extrinsic and intrinsic cues are known to regulate the sequential production of neocortical neurons, how these factors interact and function in a coordinated manner is poorly understood. The proneural gene Neurog2 is expressed in progenitors throughout corticogenesis, but is only required to specify early-born, deep-layer neuronal identities. Here, we examined how neuronal differentiation in general and Neurog2 function in particular are temporally controlled during murine neocortical development. We found that Neurog2 proneural activity declines in late corticogenesis, correlating with its phosphorylation by GSK3 kinase. Accordingly, GSK3 activity, which is negatively regulated by canonical Wnt signaling, increases over developmental time, while Wnt signaling correspondingly decreases. When ectopically activated, GSK3 inhibits Neurog2-mediated transcription in cultured cells and Neurog2 proneural activities in vivo. Conversely, a reduction in GSK3 activity promotes the precocious differentiation of later stage cortical progenitors without influencing laminar fate specification. Mechanistically, we show that GSK3 suppresses Neurog2 activity by influencing its choice of dimerization partner, promoting heterodimeric interactions with E47 (Tcfe2a), as opposed to Neurog2-Neurog2 homodimer formation, which occurs when GSK3 activity levels are low. At the functional level, Neurog2-E47 heterodimers have a reduced ability to transactivate neuronal differentiation genes compared with Neurog2-Neurog2 homodimers, both in vitro and in vivo. We thus conclude that the temporal regulation of Neurog2-E47 heterodimerization by GSK3 is a central component of the neuronal differentiation "clock" that coordinates the timing and tempo of neocortical neurogenesis in mouse.

Phospholipase C δ4 regulates cold sensitivity in mice.

PubMed

Yudin, Yevgen; Lutz, Brianna; Tao, Yuan-Xiang; Rohacs, Tibor

2016-07-01

The cold- and menthol-activated transient receptor potential melastatin 8 (TRPM8) channels are thought to be regulated by phospholipase C (PLC), but neither the specific PLC isoform nor the in vivo relevance of this regulation has been established. Here we identify PLCδ4 as the key PLC isoform involved in regulation of TRPM8 channels in vivo. We show that in small PLCδ4(-/-) TRPM8-positive dorsal root ganglion neurons cold, menthol and WS-12, a selective TRPM8 agonist, evoked significantly larger currents than in wild-type neurons, and action potential frequencies induced by menthol or by current injections were also higher in PLCδ4(-/-) neurons. PLCδ4(-/-) mice showed increased behavioural responses to evaporative cooling, and this effect was inhibited by a TRPM8 antagonist; behavioural responses to heat and mechanical stimuli were not altered. We provide evidence for the involvement of a specific PLC isoform in the regulation of cold sensitivity in mice by regulating TRPM8 activity. The transient receptor potential melastatin 8 (TRPM8) ion channel is a major sensor of environmental low temperatures. Ca(2+) -induced activation of phospholipase C (PLC) has been implied in the regulation of TRPM8 channels during menthol- and cold-induced desensitization in vitro. Here we identify PLCδ4 as the key PLC isoform involved in regulation of TRPM8 in sensory dorsal root ganglion (DRG) neurons. We identified two TRPM8-positive neuronal subpopulations, based on their cell body size. Most TRPM8-positive small neurons also responded to capsaicin, and had significantly larger menthol-induced inward current densities than medium-large cells, most of which did not respond to capsaicin. Small, but not medium-large, PLCδ4(-/-) neurons showed significantly larger currents induced by cold, menthol or WS-12, a specific TRPM8 agonist, compared to wild-type (WT) neurons, but TRPM8 protein levels were not different between the two groups. In current-clamp experiments small neurons had more depolarized resting membrane potentials, and required smaller current injections to generate action potentials (APs) than medium-large cells. In small PLCδ4(-/-) neurons, menthol application induced larger depolarizations and generation of APs with frequencies significantly higher compared to WT neurons. In behavioural experiments PLCδ4(-/-) mice showed greater sensitivity to evaporative cooling by acetone than control animals. Pretreatment with the TRPM8 antagonist PBMC reduced cold-induced responses, and the effect was more pronounced in the PLCδ4(-/-) group. Heat and mechanical sensitivity of the PLCδ4(-/-) mice was not different from WT animals. Our data support the involvement of PLCδ4 in the regulation of TRPM8 channel activity in vivo. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

Lactate rescues neuronal sodium homeostasis during impaired energy metabolism.

PubMed

Karus, Claudia; Ziemens, Daniel; Rose, Christine R

2015-01-01

Recently, we established that recurrent activity evokes network sodium oscillations in neurons and astrocytes in hippocampal tissue slices. Interestingly, metabolic integrity of astrocytes was essential for the neurons' capacity to maintain low sodium and to recover from sodium loads, indicating an intimate metabolic coupling between the 2 cell types. Here, we studied if lactate can support neuronal sodium homeostasis during impaired energy metabolism by analyzing whether glucose removal, pharmacological inhibition of glycolysis and/or addition of lactate affect cellular sodium regulation. Furthermore, we studied the effect of lactate on sodium regulation during recurrent network activity and upon inhibition of the glial Krebs cycle by sodium-fluoroacetate. Our results indicate that lactate is preferentially used by neurons. They demonstrate that lactate supports neuronal sodium homeostasis and rescues the effects of glial poisoning by sodium-fluoroacetate. Altogether, they are in line with the proposed transfer of lactate from astrocytes to neurons, the so-called astrocyte-neuron-lactate shuttle.

Lactate rescues neuronal sodium homeostasis during impaired energy metabolism

PubMed Central

Karus, Claudia; Ziemens, Daniel; Rose, Christine R

2015-01-01

Recently, we established that recurrent activity evokes network sodium oscillations in neurons and astrocytes in hippocampal tissue slices. Interestingly, metabolic integrity of astrocytes was essential for the neurons' capacity to maintain low sodium and to recover from sodium loads, indicating an intimate metabolic coupling between the 2 cell types. Here, we studied if lactate can support neuronal sodium homeostasis during impaired energy metabolism by analyzing whether glucose removal, pharmacological inhibition of glycolysis and/or addition of lactate affect cellular sodium regulation. Furthermore, we studied the effect of lactate on sodium regulation during recurrent network activity and upon inhibition of the glial Krebs cycle by sodium-fluoroacetate. Our results indicate that lactate is preferentially used by neurons. They demonstrate that lactate supports neuronal sodium homeostasis and rescues the effects of glial poisoning by sodium-fluoroacetate. Altogether, they are in line with the proposed transfer of lactate from astrocytes to neurons, the so-called astrocyte-neuron-lactate shuttle. PMID:26039160

Long-Term Recordings of Arcuate Nucleus Kisspeptin Neurons Reveal Patterned Activity That Is Modulated by Gonadal Steroids in Male Mice.

PubMed

Vanacker, Charlotte; Moya, Manuel Ricu; DeFazio, R Anthony; Johnson, Michael L; Moenter, Suzanne M

2017-10-01

Pulsatile release of gonadotropin-releasing hormone (GnRH) is key to fertility. Pulse frequency is modulated by gonadal steroids and likely arises subsequent to coordination of GnRH neuron firing activity. The source of rhythm generation and the site of steroid feedback remain critical unanswered questions. Arcuate neurons that synthesize kisspeptin, neurokinin B, and dynorphin (KNDy) may be involved in both of these processes. We tested the hypotheses that action potential firing in KNDy neurons is episodic and that gonadal steroids regulate this pattern. Targeted extracellular recordings were made of green fluorescent protein-identified KNDy neurons in brain slices from adult male mice that were intact, castrated, or castrated and treated with estradiol or dihydrotestosterone (DHT). KNDy neurons exhibited marked peaks and nadirs in action potential firing activity during recordings lasting 1 to 3.5 hours. Peaks, identified by Cluster analysis, occurred more frequently in castrated than intact mice, and either estradiol or DHT in vivo or blocking neurokinin type 3 receptor in vitro restored peak frequency to intact levels. The frequency of peaks in firing rate and estradiol regulation of this frequency is similar to that observed for GnRH neurons, whereas DHT suppressed firing in KNDy but not GnRH neurons. We further examined the patterning of action potentials to identify bursts that may be associated with increased neuromodulator release. Burst frequency and duration are increased in castrated compared with intact and steroid-treated mice. The observation that KNDy neurons fire in an episodic manner that is regulated by steroid feedback is consistent with a role for these neurons in GnRH pulse generation and regulation. Copyright © 2017 Endocrine Society.

The neuropeptide PDF acts directly on evening pacemaker neurons to regulate multiple features of circadian behavior.

PubMed

Lear, Bridget C; Zhang, Luoying; Allada, Ravi

2009-07-01

Discrete clusters of circadian clock neurons temporally organize daily behaviors such as sleep and wake. In Drosophila, a network of just 150 neurons drives two peaks of timed activity in the morning and evening. A subset of these neurons expresses the neuropeptide pigment dispersing factor (PDF), which is important for promoting morning behavior as well as maintaining robust free-running rhythmicity in constant conditions. Yet, how PDF acts on downstream circuits to mediate rhythmic behavior is unknown. Using circuit-directed rescue of PDF receptor mutants, we show that PDF targeting of just approximately 30 non-PDF evening circadian neurons is sufficient to drive morning behavior. This function is not accompanied by large changes in core molecular oscillators in light-dark, indicating that PDF RECEPTOR likely regulates the output of these cells under these conditions. We find that PDF also acts on this focused set of non-PDF neurons to regulate both evening activity phase and period length, consistent with modest resetting effects on core oscillators. PDF likely acts on more distributed pacemaker neuron targets, including the PDF neurons themselves, to regulate rhythmic strength. Here we reveal defining features of the circuit-diagram for PDF peptide function in circadian behavior, revealing the direct neuronal targets of PDF as well as its behavioral functions at those sites. These studies define a key direct output circuit sufficient for multiple PDF dependent behaviors.

Intrinsically active and pacemaker neurons in pluripotent stem cell-derived neuronal populations.

PubMed

Illes, Sebastian; Jakab, Martin; Beyer, Felix; Gelfert, Renate; Couillard-Despres, Sébastien; Schnitzler, Alfons; Ritter, Markus; Aigner, Ludwig

2014-03-11

Neurons generated from pluripotent stem cells (PSCs) self-organize into functional neuronal assemblies in vitro, generating synchronous network activities. Intriguingly, PSC-derived neuronal assemblies develop spontaneous activities that are independent of external stimulation, suggesting the presence of thus far undetected intrinsically active neurons (IANs). Here, by using mouse embryonic stem cells, we provide evidence for the existence of IANs in PSC-neuronal networks based on extracellular multielectrode array and intracellular patch-clamp recordings. IANs remain active after pharmacological inhibition of fast synaptic communication and possess intrinsic mechanisms required for autonomous neuronal activity. PSC-derived IANs are functionally integrated in PSC-neuronal populations, contribute to synchronous network bursting, and exhibit pacemaker properties. The intrinsic activity and pacemaker properties of the neuronal subpopulation identified herein may be particularly relevant for interventions involving transplantation of neural tissues. IANs may be a key element in the regulation of the functional activity of grafted as well as preexisting host neuronal networks.

Intrinsically Active and Pacemaker Neurons in Pluripotent Stem Cell-Derived Neuronal Populations

PubMed Central

Illes, Sebastian; Jakab, Martin; Beyer, Felix; Gelfert, Renate; Couillard-Despres, Sébastien; Schnitzler, Alfons; Ritter, Markus; Aigner, Ludwig

2014-01-01

Summary Neurons generated from pluripotent stem cells (PSCs) self-organize into functional neuronal assemblies in vitro, generating synchronous network activities. Intriguingly, PSC-derived neuronal assemblies develop spontaneous activities that are independent of external stimulation, suggesting the presence of thus far undetected intrinsically active neurons (IANs). Here, by using mouse embryonic stem cells, we provide evidence for the existence of IANs in PSC-neuronal networks based on extracellular multielectrode array and intracellular patch-clamp recordings. IANs remain active after pharmacological inhibition of fast synaptic communication and possess intrinsic mechanisms required for autonomous neuronal activity. PSC-derived IANs are functionally integrated in PSC-neuronal populations, contribute to synchronous network bursting, and exhibit pacemaker properties. The intrinsic activity and pacemaker properties of the neuronal subpopulation identified herein may be particularly relevant for interventions involving transplantation of neural tissues. IANs may be a key element in the regulation of the functional activity of grafted as well as preexisting host neuronal networks. PMID:24672755

Tlr7 deletion alters expression profiles of genes related to neural function and regulates mouse behaviors and contextual memory.

PubMed

Hung, Yun-Fen; Chen, Chiung-Ya; Li, Wan-Chen; Wang, Ting-Fang; Hsueh, Yi-Ping

2018-06-07

The neuronal innate immune system recognizes endogenous danger signals and regulates neuronal development and function. Toll-like receptor 7 (TLR7), one of the TLRs that trigger innate immune responses in neurons, controls neuronal morphology. To further assess the function of TLR7 in the brain, we applied next generation sequencing to investigate the effect of Tlr7 deletion on gene expression in hippocampal and cortical mixed cultures and on mouse behaviors. Since previous in vivo study suggested that TLR7 is more critical for neuronal morphology at earlier developmental stages, we analyzed two time-points (4 and 18 DIV) to represent young and mature neurons, respectively. At 4 DIV, Tlr7 KO neurons exhibited reduced expression of genes involved in neuronal development, synaptic organization and activity and behaviors. Some of these Tlr7-regulated genes are also associated with multiple neurological and neuropsychiatric diseases. TLR7-regulated transcriptomic profiles differed at 18 DIV. Apart from neuronal genes, genes related to glial cell development and differentiation became sensitive to Tlr7 deletion at 18 DIV. Moreover, Tlr7 KO mice exhibited altered behaviors in terms of anxiety, aggression, olfaction and contextual fear memory. Electrophysiological analysis further showed an impairment of long-term potentiation in Tlr7 KO hippocampus. Taken together, these results indicate that TLR7 regulates neural development and brain function, even in the absence of infectious or pathogenic molecules. Our findings strengthen evidence for the role of the neuronal innate immune system in fine-tuning neuronal morphology and activity and implicate it in neuropsychiatric disorders. Copyright © 2018 Elsevier Inc. All rights reserved.

Activation of VTA GABA neurons disrupts reward consumption

PubMed Central

van Zessen, Ruud; Phillips, Jana L.; Budygin, Evgeny A.; Stuber, Garret D.

2012-01-01

The activity of Ventral Tegmental Area (VTA) dopamine (DA) neurons promotes behavioral responses to rewards and environmental stimuli that predict them. VTA GABA inputs synapse directly onto DA neurons and may regulate DA neuronal activity to alter reward-related behaviors, however, the functional consequences of selective activation of VTA GABA neurons remains unknown. Here, we show that in vivo optogenetic activation of VTA GABA neurons disrupts reward consummatory behavior, but not conditioned anticipatory behavior in response to reward-predictive cues. In addition, direct activation of VTA GABA projections to the nucleus accumbens (NAc) resulted in detectable GABA release, but did not alter reward consumption. Furthermore, optogenetic stimulation of VTA GABA neurons directly suppressed the activity and excitability of neighboring DA neurons, as well as the release of DA in the NAc, suggesting that the dynamic interplay between VTA DA and GABA neurons can control the initiation and termination of reward-related behaviors. PMID:22445345

The importance of regulation of blood glucose levels through activation of peripheral 5'-AMP-activated protein kinase on ischemic neuronal damage.

PubMed

Harada, Shinichi; Fujita-Hamabe, Wakako; Tokuyama, Shogo

2010-09-10

5'-AMP-activated protein kinase (AMPK) is a serine/threonine kinase that plays a key role in energy homeostasis. Recently, it was reported that centrally activated AMPK is involved in the development of ischemic neuronal damage, while the effect of peripherally activated AMPK on ischemic neuronal damage is not known. In addition, we have previously reported that the development of post-ischemic glucose intolerance could be one of the triggers for the aggravation of neuronal damage. In this study, we focused on effect of activation of peripheral or central AMPK on the development of ischemic neuronal damage. Male ddY mice were subjected to 2 h of middle cerebral artery occlusion (MCAO). Neuronal damage was estimated by histological and behavioral analysis after MCAO. In the liver and skeletal muscle, AMPK activity was not affected by MCAO. But, application of intraperitoneal metformin (250 mg/kg), an AMPK activator, significantly suppressed the development of post-ischemic glucose intolerance and ischemic neuronal damage without alteration of central AMPK activity. On the other hand, application of intracerebroventricular metformin (25, 100 microg/mouse) significantly exacerbated the development of neuronal damage observed on day 1 after MCAO, in a dose-dependent manner. These effects were significantly blocked by compound C, a specific AMPK inhibitor. These results suggest that central AMPK was activated by ischemic stress per se, however, peripheral AMPK was not altered. Furthermore, the regulation of post-ischemic glucose intolerance by activation of peripheral AMPK is of assistance for the suppression of cerebral ischemic neuronal damage. 2010 Elsevier B.V. All rights reserved.

The Ste20 Family Kinases MAP4K4, MINK1, and TNIK Converge to Regulate Stress-Induced JNK Signaling in Neurons.

PubMed

Larhammar, Martin; Huntwork-Rodriguez, Sarah; Rudhard, York; Sengupta-Ghosh, Arundhati; Lewcock, Joseph W

2017-11-15

The c-Jun- N -terminal kinase (JNK) signaling pathway regulates nervous system development, axon regeneration, and neuronal degeneration after acute injury or in chronic neurodegenerative disease. Dual leucine zipper kinase (DLK) is required for stress-induced JNK signaling in neurons, yet the factors that initiate DLK/JNK pathway activity remain poorly defined. In the present study, we identify the Ste20 kinases MAP4K4, misshapen-like kinase 1 (MINK1 or MAP4K6) and TNIK Traf2- and Nck-interacting kinase (TNIK or MAP4K7), as upstream regulators of DLK/JNK signaling in neurons. Using a trophic factor withdrawal-based model of neurodegeneration in both male and female embryonic mouse dorsal root ganglion neurons, we show that MAP4K4, MINK1, and TNIK act redundantly to regulate DLK activation and downstream JNK-dependent phosphorylation of c-Jun in response to stress. Targeting MAP4K4, MINK1, and TNIK, but not any of these kinases individually, is sufficient to protect neurons potently from degeneration. Pharmacological inhibition of MAP4Ks blocks stabilization and phosphorylation of DLK within axons and subsequent retrograde translocation of the JNK signaling complex to the nucleus. These results position MAP4Ks as important regulators of the DLK/JNK signaling pathway. SIGNIFICANCE STATEMENT Neuronal degeneration occurs in disparate circumstances: during development to refine neuronal connections, after injury to clear damaged neurons, or pathologically during disease. The dual leucine zipper kinase (DLK)/c-Jun- N -terminal kinase (JNK) pathway represents a conserved regulator of neuronal injury signaling that drives both neurodegeneration and axon regeneration, yet little is known about the factors that initiate DLK activity. Here, we uncover a novel role for a subfamily of MAP4 kinases consisting of MAP4K4, Traf2- and Nck-interacting kinase (TNIK or MAP4K7), and misshapen-like kinase 1 (MINK1 or MAP4K6) in regulating DLK/JNK signaling in neurons. Inhibition of these MAP4Ks blocks stress-induced retrograde JNK signaling and protects from neurodegeneration, suggesting that these kinases may represent attractive therapeutic targets. Copyright © 2017 the authors 0270-6474/17/3711074-11$15.00/0.

Food-derived sensory cues modulate longevity via distinct neuroendocrine insulin-like peptides

PubMed Central

Artan, Murat; Jeong, Dae-Eun; Lee, Dongyeop; Kim, Young-Il; Son, Heehwa G.; Husain, Zahabiya; Kim, Jinmahn; Altintas, Ozlem; Kim, Kyuhyung; Alcedo, Joy; Lee, Seung-Jae V.

2016-01-01

Environmental fluctuations influence organismal aging by affecting various regulatory systems. One such system involves sensory neurons, which affect life span in many species. However, how sensory neurons coordinate organismal aging in response to changes in environmental signals remains elusive. Here, we found that a subset of sensory neurons shortens Caenorhabditis elegans’ life span by differentially regulating the expression of a specific insulin-like peptide (ILP), INS-6. Notably, treatment with food-derived cues or optogenetic activation of sensory neurons significantly increases ins-6 expression and decreases life span. INS-6 in turn relays the longevity signals to nonneuronal tissues by decreasing the activity of the transcription factor DAF-16/FOXO. Together, our study delineates a mechanism through which environmental sensory cues regulate aging rates by modulating the activities of specific sensory neurons and ILPs. PMID:27125673

Amitriptyline Activates TrkA to Aid Neuronal Growth and Attenuate Anesthesia-Induced Neurodegeneration in Rat Dorsal Root Ganglion Neurons.

PubMed

Zheng, Xiaochun; Chen, Feng; Zheng, Ting; Huang, Fengyi; Chen, Jianghu; Tu, Wenshao

2016-05-01

Tricyclic antidepressant amitriptyline (AM) has been shown to exert neurotrophic activity on neurons. We thus explored whether AM may aid the neuronal development and protect anesthesia-induced neuro-injury in young spinal cord dorsal root ganglion (DRG) neurons.The DRG explants were prepared from 1-day-old rats. The effect of AM on aiding DRG neural development was examined by immunohistochemistry at dose-dependent manner. AM-induced changes in gene and protein expressions, and also phosphorylation states of tyrosine kinases receptor A (TrkA) and B (TrkB) in DRG, were examined by quantitative real-time polymerase chain reaction and western blot. The effect of AM on attenuating lidocaine-induced DRG neurodegeneration was examined by immunohistochemistry, and small interfering RNA (siRNA)-mediated TrkA/B down-regulation.Amitriptyline stimulated DRG neuronal development in dose-dependent manner, but exerted toxic effect at concentrations higher than 10 M. AM activated TrkA in DRG through phosphorylation, whereas it had little effect on TrkB-signaling pathway. AM reduced lidocaine-induced DRG neurodegeneration by regenerating neurites and growth cones. Moreover, the neuroprotection of AM on lidocaine-injured neurodegeneration was blocked by siRNA-mediated TrkA down-regulation, but not by TrkB down-regulation.Amitriptyline facilitated neuronal development and had protective effect on lidocaine-induced neurodegeneration, very likely through the activation of TrkA-signaling pathway in DRG.

Neuronal SIRT1 (Silent Information Regulator 2 Homologue 1) Regulates Glycolysis and Mediates Resveratrol-Induced Ischemic Tolerance.

PubMed

Koronowski, Kevin B; Khoury, Nathalie; Saul, Isabel; Loris, Zachary B; Cohan, Charles H; Stradecki-Cohan, Holly M; Dave, Kunjan R; Young, Juan I; Perez-Pinzon, Miguel A

2017-11-01

Resveratrol, at least in part via SIRT1 (silent information regulator 2 homologue 1) activation, protects against cerebral ischemia when administered 2 days before injury. However, it remains unclear if SIRT1 activation must occur, and in which brain cell types, for the induction of neuroprotection. We hypothesized that neuronal SIRT1 is essential for resveratrol-induced ischemic tolerance and sought to characterize the metabolic pathways regulated by neuronal Sirt1 at the cellular level in the brain. We assessed infarct size and functional outcome after transient 60 minute middle cerebral artery occlusion in control and inducible, neuronal-specific SIRT1 knockout mice. Nontargeted primary metabolomics analysis identified putative SIRT1-regulated pathways in brain. Glycolytic function was evaluated in acute brain slices from adult mice and primary neuronal-enriched cultures under ischemic penumbra-like conditions. Resveratrol-induced neuroprotection from stroke was lost in neuronal Sirt1 knockout mice. Metabolomics analysis revealed alterations in glucose metabolism on deletion of neuronal Sirt1 , accompanied by transcriptional changes in glucose metabolism machinery. Furthermore, glycolytic ATP production was impaired in acute brain slices from neuronal Sirt1 knockout mice. Conversely, resveratrol increased glycolytic rate in a SIRT1-dependent manner and under ischemic penumbra-like conditions in vitro. Our data demonstrate that resveratrol requires neuronal SIRT1 to elicit ischemic tolerance and identify a novel role for SIRT1 in the regulation of glycolytic function in brain. Identification of robust neuroprotective mechanisms that underlie ischemia tolerance and the metabolic adaptations mediated by SIRT1 in brain are crucial for the translation of therapies in cerebral ischemia and other neurological disorders. © 2017 American Heart Association, Inc.

Effects of body temperature on neural activity in the hippocampus: regulation of resting membrane potentials by transient receptor potential vanilloid 4.

PubMed

Shibasaki, Koji; Suzuki, Makoto; Mizuno, Atsuko; Tominaga, Makoto

2007-02-14

Physiological body temperature is an important determinant for neural functions, and it is well established that changes in temperature have dynamic influences on hippocampal neural activities. However, the detailed molecular mechanisms have never been clarified. Here, we show that hippocampal neurons express functional transient receptor potential vanilloid 4 (TRPV4), one of the thermosensitive TRP (transient receptor potential) channels, and that TRPV4 is constitutively active at physiological temperature. Activation of TRPV4 at 37 degrees C depolarized the resting membrane potential in hippocampal neurons by allowing cation influx, which was observed in wild-type (WT) neurons, but not in TRPV4-deficient (TRPV4KO) cells, although dendritic morphology, synaptic marker clustering, and synaptic currents were indistinguishable between the two genotypes. Furthermore, current injection studies revealed that TRPV4KO neurons required larger depolarization to evoke firing, equivalent to WT neurons, indicating that TRPV4 is a key regulator for hippocampal neural excitabilities. We conclude that TRPV4 is activated by physiological temperature in hippocampal neurons and thereby controls their excitability.

[P21-activated kinases and their role in the nervous system].

PubMed

Qin, Yuan; Ding, Yue-Min; Xia, Qiang

2012-12-25

P21-activated kinases (PAK) participate in a variety of important cellular activities, such as cytoskeleton remodeling, cell migration, cell cycle regulation, and apoptosis or survival. PAK also has an important impact on brain development, neuronal differentiation, and regulation of synaptic plasticity in the nervous system. PAK abnormalities result in diseases including cancer, Parkinson's disease (PD), Alzheimer's disease (AD) and neural retardation. Therefore, it is of vital physiological significance to investigate the neuronal function of PAK. In this paper we review the advancement of research on the neuronal biological function and the underlying mechanisms of PAK.

Paeoniflorin, a Monoterpene Glycoside, Protects the Brain from Cerebral Ischemic Injury via Inhibition of Apoptosis.

PubMed

Zhang, Yuqin; Li, Huang; Huang, Mingqing; Huang, Mei; Chu, Kedan; Xu, Wei; Zhang, Shengnan; Que, Jinhua; Chen, Lidian

2015-01-01

Paeoniflorin (PF) is a principal bioactive component, which exhibits many pharmacological effects, including protection against ischemic injury. This paper aimed to investigate the protective effect of PF both in vivo and in vitro. Middle cerebral artery occlusion (MCAO) was performed on male Sprague-Dawley (SD) rat for 2 h, and different doses of PF or vehicle were administered 2 h after reperfusion. Rats were sacrificed after 7 days treatment of PF/vehicle. PF treatment for 7 days ameliorated MCAO-induced neurological deficit and decreased the infarct area. Further study demonstrated that PF inhibited the over-activation of astrocytes and apoptosis of neurons, and PF promoted up-regulation of neuronal specific marker neuron-specific nuclear (NeuN) and microtubule-associated protein 2 (MAP-2) in brain. Moreover, NMDA-induced neuron apoptosis was employed. The in vitro study revealed that PF treatment protected against NMDA-induced cell apoptosis and neuronal loss via up-regulation of neuronal specific marker NeuN, MAP-2 and Bcl-2 and the down-regulation Bax. Taken together, the present study demonstrates that PF produces its protective effect by inhibiting the over-activation of astrocytes, apoptosis of neurons and up-regulation of neuronal specific marker NeuN, MAP-2, and B-cell lymphoma-2 (Bcl-2), and down-regulation Bax. Our study reveals that PF may be a potential neuroprotective agent for stroke and can provide basic data for clinical use.

Effect of dietary salt intake on epithelial Na+ channels (ENaC) in vasopressin magnocellular neurosecretory neurons in the rat supraoptic nucleus.

PubMed

Sharma, Kaustubh; Haque, Masudul; Guidry, Richard; Ueta, Yoichi; Teruyama, Ryoichi

2017-09-01

A growing body of evidence suggests that epithelial Na + channels (ENaCs) in the brain play a significant role in the regulation of blood pressure; however, the brain structures that mediate the effect are not well understood. Because vasopressin (VP) neurons play a pivotal role in coordinating neuroendocrine and autonomic responses to maintain cardiovascular homeostasis, a basic understanding of the regulation and activity of ENaC in VP neurons is of great interest. We show that high dietary salt intake caused an increase in the expression and activity of ENaC which resulted in the steady state depolarization of VP neurons. The results help us understand one of the mechanisms underlying how dietary salt intake affects the activity of VP neurons via ENaC activity. All three epithelial Na + channel (ENaC) subunits (α, β and γ) are located in vasopressin (VP) magnocellular neurons in the hypothalamic supraoptic (SON) and paraventricular nuclei. Our previous study demonstrated that ENaC mediates a Na + leak current that affects the steady state membrane potential in VP neurons. In the present study, we evaluated the effect of dietary salt intake on ENaC regulation and activity in VP neurons. High dietary salt intake for 7 days caused an increase in expression of β- and γENaC subunits in the SON and the translocation of αENaC immunoreactivity towards the plasma membrane. Patch clamp experiments on hypothalamic slices showed that the mean amplitude of the putative ENaC currents was significantly greater in VP neurons from animals that were fed a high salt diet compared with controls. The enhanced ENaC current contributed to the more depolarized basal membrane potential observed in VP neurons in the high salt diet group. These findings indicate that high dietary NaCl intake enhances the expression and activity of ENaCs, which augments synaptic drive by depolarizing the basal membrane potential close to the action potential threshold during hormonal demand. However, ENaCs appear to have only a minor role in the regulation of the firing activity of VP neurons in the absence of synaptic inputs as neither the mean intraburst frequency, burst duration, nor interspike interval variability of phasic bursting activity was affected. Moreover, ENaC activity did not affect the initiation, sustention, or termination of the phasic bursting generated in an intrinsic manner without synaptic inputs. © 2017 The Authors. The Journal of Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society.

Hydroxysafflor Yellow A Attenuates Neuron Damage by Suppressing the Lipopolysaccharide-Induced TLR4 Pathway in Activated Microglial Cells.

PubMed

Lv, Yanni; Qian, Yisong; Ou-Yang, Aijun; Fu, Longsheng

2016-11-01

Microglia activation initiates a neurological deficit cascade that contributes to substantial neuronal damage and impairment following ischemia stroke. Toll-like receptor 4 (TLR4) has been demonstrated to play a critical role in this cascade. In the current study, we tested the hypothesis that hydroxysafflor yellow A (HSYA), an active ingredient extracted from Flos Carthami tinctorii, alleviated inflammatory damage, and mediated neurotrophic effects in neurons by inducing the TLR4 pathway in microglia. A non-contact Transwell co-culture system comprised microglia and neurons was treated with HSYA followed by a 1 mg/mL lipopolysaccharide (LPS) stimulation. The microglia were activated prior to neuronal apoptosis, which were induced by increasing TLR4 expression in the activated microglia. However, HSYA suppressed TLR4 expression in the activated microglia, resulting in less neuronal damage at the early stage of LPS stimulation. Western blot analysis and immunofluorescence indicated that dose-dependently HSYA down-regulated TLR4-induced downstream effectors myeloid differentiation factor 88 (MyD88), nuclear factor kappa b (NF-κB), and the mitogen-activated protein kinases (MAPK)-regulated proteins c-Jun NH2-terminal protein kinase (JNK), protein kinase (ERK) 1/2 (ERK1/2), p38 MAPK (p38), as well as the LPS-induced inflammatory cytokine release. However, HSYA up-regulated brain-derived neurotrophic factor (BDNF) expression. Our data suggest that HSYA could exert neurotrophic and anti-inflammatory functions in response to LPS stimulation by inhibiting TLR4 pathway-mediated signaling.

Interplay between glucose and leptin signaling determines the strength of GABAergic synapses at POMC neurons

PubMed Central

Lee, Dong Kun; Jeong, Jae Hoon; Chun, Sung-Kun; Chua, Streamson; Jo, Young-Hwan

2015-01-01

Regulation of GABAergic inhibitory inputs and alterations in POMC neuron activity by nutrients and adiposity signals regulate energy and glucose homeostasis. Thus, understanding how POMC neurons integrate these two signal molecules at the synaptic level is important. Here we show that leptin’s action on GABA release to POMC neurons is influenced by glucose levels. Leptin stimulates the JAK2-PI3K pathway in both presynaptic GABAergic terminals and postsynaptic POMC neurons. Inhibition of AMPK activity in presynaptic terminals decreases GABA release at 10 mM glucose. However, postsynaptic TRPC channel opening by the PI3K-PLC signaling pathway in POMC neurons enhances spontaneous GABA release via activation of presynaptic MC3/4 and mGlu receptors at 2.5 mM glucose. High-fat feeding blunts AMPK-dependent presynaptic inhibition, whereas PLC-mediated GABAergic feedback inhibition remains responsive to leptin. Our data indicate that the interplay between glucose and leptin signaling in glutamatergic POMC neurons is critical for determining the strength of inhibitory tone towards POMC neurons. PMID:25808323

Interplay between glucose and leptin signalling determines the strength of GABAergic synapses at POMC neurons.

PubMed

Lee, Dong Kun; Jeong, Jae Hoon; Chun, Sung-Kun; Chua, Streamson; Jo, Young-Hwan

2015-03-26

Regulation of GABAergic inhibitory inputs and alterations in POMC neuron activity by nutrients and adiposity signals regulate energy and glucose homeostasis. Thus, understanding how POMC neurons integrate these two signal molecules at the synaptic level is important. Here we show that leptin's action on GABA release to POMC neurons is influenced by glucose levels. Leptin stimulates the JAK2-PI3K pathway in both presynaptic GABAergic terminals and postsynaptic POMC neurons. Inhibition of AMPK activity in presynaptic terminals decreases GABA release at 10 mM glucose. However, postsynaptic TRPC channel opening by the PI3K-PLC signalling pathway in POMC neurons enhances spontaneous GABA release via activation of presynaptic MC3/4 and mGlu receptors at 2.5 mM glucose. High-fat feeding blunts AMPK-dependent presynaptic inhibition, whereas PLC-mediated GABAergic feedback inhibition remains responsive to leptin. Our data indicate that the interplay between glucose and leptin signalling in glutamatergic POMC neurons is critical for determining the strength of inhibitory tone towards POMC neurons.

Lhx6-positive GABA-releasing neurons of the zona incerta promote sleep

PubMed Central

Liu, Kai; Kim, Juhyun; Kim, Dong Won; Zhang, Yi Stephanie; Bao, Hechen; Denaxa, Myrto; Lim, Szu-Aun; Kim, Eileen; Liu, Chang; Wickersham, Ian R.; Pachnis, Vassilis; Hattar, Samer; Song, Juan; Brown, Solange P.; Blackshaw, Seth

2017-01-01

Multiple populations of wake-promoting neurons have been characterized in mammals, but few sleep-promoting neurons have been identified1. Wake-promoting cell types include hypocretin and GABA (γ-aminobutyric-acid)-releasing neurons of the lateral hypothalamus, which promote the transition to wakefulness from non-rapid eye movement (NREM) and rapid eye movement (REM) sleep2,3. Here we show that a subset of GABAergic neurons in the mouse ventral zona incerta, which express the LIM homeodomain factor Lhx6 and are activated by sleep pressure, both directly inhibit wake-active hypocretin and GABAergic cells in the lateral hypothalamus and receive inputs from multiple sleep–wake-regulating neurons. Conditional deletion of Lhx6 from the developing diencephalon leads to decreases in both NREM and REM sleep. Furthermore, selective activation and inhibition of Lhx6-positive neurons in the ventral zona incerta bidirectionally regulate sleep time in adult mice, in part through hypocretin-dependent mechanisms. These studies identify a GABAergic subpopulation of neurons in the ventral zona incerta that promote sleep. PMID:28847002

Royal Jelly Reduces Cholesterol Levels, Ameliorates Aβ Pathology and Enhances Neuronal Metabolic Activities in a Rabbit Model of Alzheimer's Disease.

PubMed

Pan, Yongming; Xu, Jianqin; Chen, Cheng; Chen, Fangming; Jin, Ping; Zhu, Keyan; Hu, Chenyue W; You, Mengmeng; Chen, Minli; Hu, Fuliang

2018-01-01

Alzheimer's disease (AD) is the most common form of dementia characterized by aggregation of amyloid β (Aβ) and neuronal loss. One of the risk factors for AD is high cholesterol levels, which are known to promote Aβ deposition. Previous studies have shown that royal jelly (RJ), a product of worker bees, has potential neuroprotective effects and can attenuate Aβ toxicity. However, little is known about how RJ regulates Aβ formation and its effects on cholesterol levels and neuronal metabolic activities. Here, we investigated whether RJ can reduce cholesterol levels, regulate Aβ levels and enhance neuronal metabolic activities in an AD rabbit model induced by 2% cholesterol diet plus copper drinking water. Our results suggest that RJ significantly reduced the levels of plasma total cholesterol (TC) and low density lipoprotein-cholesterol (LDL-C), and decreased the level of Aβ in rabbit brains. RJ was also shown to markedly ameliorate amyloid deposition in AD rabbits from Aβ immunohistochemistry and thioflavin-T staining. Furthermore, our study suggests that RJ can reduce the expression levels of β-site APP cleaving enzyme-1 (BACE1) and receptor for advanced glycation end products (RAGE), and increase the expression levels of low density lipoprotein receptor-related protein 1 (LRP-1) and insulin degrading enzyme (IDE). In addition, we found that RJ remarkably increased the number of neurons, enhanced antioxidant capacities, inhibited activated-capase-3 protein expression, and enhanced neuronal metabolic activities by increasing N-acetyl aspartate (NAA) and glutamate and by reducing choline and myo-inositol in AD rabbits. Taken together, our data demonstrated that RJ could reduce cholesterol levels, regulate Aβ levels and enhance neuronal metabolic activities in AD rabbits, providing preclinical evidence that RJ treatment has the potential to protect neurons and prevent AD.

TRPC6-mediated ERK1/2 Activation Regulates Neuronal Excitability via Subcellular Kv4.3 Localization in the Rat Hippocampus

PubMed Central

Kim, Ji-Eun; Park, Jin-Young; Kang, Tae-Cheon

2017-01-01

Recently, we have reported that transient receptor potential channel-6 (TRPC6) plays an important role in the regulation of neuronal excitability and synchronization of spiking activity in the dentate granule cells (DGC). However, the underlying mechanisms of TRPC6 in these phenomena have been still unclear. In the present study, we investigated the role of TRPC6 in subcellular localization of Kv4.3 and its relevance to neuronal excitability in the rat hippocampus. TRPC6 knockdown increased excitability and inhibitory transmission in the DGC and the CA1 neurons in response to a paired-pulse stimulus. However, TRPC6 knockdown impaired γ-aminobutyric acid (GABA)ergic inhibition in the hippocampus during and after high-frequency stimulation (HFS). TRPC6 knockdown reduced the Kv4.3 clusters in membrane fractions and its dendritic localization on DGC and GABAergic interneurons. TRPC6 knockdown also decreased extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation and the efficacy of 4-aminopyridine (4-AP) in neuronal excitability. An ERK1/2 inhibitor generated multiple population spikes in response to a paired-pulse stimulus, concomitant with reduced membrane Kv4.3 translocation. A TRPC6 activator (hyperforin) reversed the effects of TRPC knockdown, except paired-pulse inhibition. These findings provide valuable clues indicating that TRPC6-mediated ERK1/2 activation may regulate subcellular Kv4.3 localization in DGC and interneurons, which is cause-effect relationship between neuronal excitability and seizure susceptibility. PMID:29326557

Retrieval-Induced Upregulation of Tet3 in Pyramidal Neurons of the Dorsal Hippocampus Mediates Cocaine-Associated Memory Reconsolidation

PubMed Central

Liu, Cao; Sun, Xue; Wang, Zhilin; Le, Qiumin; Liu, Peipei; Jiang, Changyou; Wang, Feifei; Ma, Lan

2018-01-01

Abstract Background Memory retrieval refers to reexposure to information previously encoded and stored in the brain. Following retrieval, a once-consolidated memory destabilizes and undergoes reconsolidation, during which gene expression changes to restabilize memory. Investigating epigenetic regulation during reconsolidation could provide insights into normal memory formation and pathological memory associated with psychiatric disorders. Methods We used cocaine-induced conditioned place preference to assess the cocaine-associated memory of mice and used chemogenetic methods to manipulate the activity of the pyramidal neurons in the dorsal hippocampus. We isolated the ribosome-associated transcripts from the excitatory neurons in the dorsal hippocampus by RiboTag purification to identify the potential epigenetic regulators, and we specifically knocked down gene expression in pyramidal neurons with a Cre-dependent lentivirus. Results Chemogenetically silencing the activity of the pyramidal neurons in the dorsal hippocampus immediately after memory retrieval markedly impaired memory reconsolidation, and the ribosome-associated mRNA level of the ten-eleven translocation (Tet) family methylcytosine dioxygenase Tet3, but not Tet1 or Tet2, was dramatically upregulated 10 minutes after memory retrieval. The protein level of Tet3 in the dorsal hippocampus but not in the anterior cingulate cortex was dramatically increased 1 hour after memory retrieval. Specifically, knockdown of Tet3 in pyramidal neurons in the dorsal hippocampus decreased the activation of pyramidal neurons and impaired the reconsolidation of cocaine-associated memory. Conclusions Our findings highlight the new function of the DNA demethylation regulator Tet3 in pyramidal neurons of the dorsal hippocampus in regulating the reconsolidation of cocaine-associated memory. PMID:29106571

Estradiol-Dependent Stimulation and Suppression of Gonadotropin-Releasing Hormone Neuron Firing Activity by Corticotropin-Releasing Hormone in Female Mice.

PubMed

Phumsatitpong, Chayarndorn; Moenter, Suzanne M

2018-01-01

Gonadotropin-releasing hormone (GnRH) neurons are the final central regulators of reproduction, integrating various inputs that modulate fertility. Stress typically inhibits reproduction but can be stimulatory; stress effects can also be modulated by steroid milieu. Corticotropin-releasing hormone (CRH) released during the stress response may suppress reproduction independent of downstream glucocorticoids. We hypothesized CRH suppresses fertility by decreasing GnRH neuron firing activity. To test this, mice were ovariectomized (OVX) and either implanted with an estradiol capsule (OVX+E) or not treated further to examine the influence of estradiol on GnRH neuron response to CRH. Targeted extracellular recordings were used to record firing activity from green fluorescent protein-identified GnRH neurons in brain slices before and during CRH treatment; recordings were done in the afternoon when estradiol has a positive feedback effect to increase GnRH neuron firing. In OVX mice, CRH did not affect the firing rate of GnRH neurons. In contrast, CRH exhibited dose-dependent stimulatory (30 nM) or inhibitory (100 nM) effects on GnRH neuron firing activity in OVX+E mice; both effects were reversible. The dose-dependent effects of CRH appear to result from activation of different receptor populations; a CRH receptor type-1 agonist increased firing activity in GnRH neurons, whereas a CRH receptor type-2 agonist decreased firing activity. CRH and specific agonists also differentially regulated short-term burst frequency and burst properties, including burst duration, spikes/burst, and/or intraburst interval. These results indicate that CRH alters GnRH neuron activity and that estradiol is required for CRH to exert both stimulatory and inhibitory effects on GnRH neurons. Copyright © 2018 Endocrine Society.

An excitatory paraventricular nucleus to AgRP neuron circuit that drives hunger.

PubMed

Krashes, Michael J; Shah, Bhavik P; Madara, Joseph C; Olson, David P; Strochlic, David E; Garfield, Alastair S; Vong, Linh; Pei, Hongjuan; Watabe-Uchida, Mitsuko; Uchida, Naoshige; Liberles, Stephen D; Lowell, Bradford B

2014-03-13

Hunger is a hard-wired motivational state essential for survival. Agouti-related peptide (AgRP)-expressing neurons in the arcuate nucleus (ARC) at the base of the hypothalamus are crucial to the control of hunger. They are activated by caloric deficiency and, when naturally or artificially stimulated, they potently induce intense hunger and subsequent food intake. Consistent with their obligatory role in regulating appetite, genetic ablation or chemogenetic inhibition of AgRP neurons decreases feeding. Excitatory input to AgRP neurons is important in caloric-deficiency-induced activation, and is notable for its remarkable degree of caloric-state-dependent synaptic plasticity. Despite the important role of excitatory input, its source(s) has been unknown. Here, through the use of Cre-recombinase-enabled, cell-specific neuron mapping techniques in mice, we have discovered strong excitatory drive that, unexpectedly, emanates from the hypothalamic paraventricular nucleus, specifically from subsets of neurons expressing thyrotropin-releasing hormone (TRH) and pituitary adenylate cyclase-activating polypeptide (PACAP, also known as ADCYAP1). Chemogenetic stimulation of these afferent neurons in sated mice markedly activates AgRP neurons and induces intense feeding. Conversely, acute inhibition in mice with caloric-deficiency-induced hunger decreases feeding. Discovery of these afferent neurons capable of triggering hunger advances understanding of how this intense motivational state is regulated.

Activation of extrasynaptic, but not synaptic, NMDA receptors modifies amyloid precursor protein expression pattern and increases amyloid-ß production.

PubMed

Bordji, Karim; Becerril-Ortega, Javier; Nicole, Olivier; Buisson, Alain

2010-11-24

Calcium is a key mediator controlling essential neuronal functions depending on electrical activity. Altered neuronal calcium homeostasis affects metabolism of amyloid precursor protein (APP), leading to increased production of β-amyloid (Aβ), and contributing to the initiation of Alzheimer's disease (AD). A linkage between excessive glutamate receptor activation and neuronal Aβ release was established, and recent reports suggest that synaptic and extrasynaptic NMDA receptor (NMDAR) activation may have distinct consequences in plasticity, gene regulation, and neuronal death. Here, we report for the first time that prolonged activation of extrasynaptic NMDAR, but not synaptic NMDAR, dramatically increased the neuronal production of Aβ. This effect was preceded by a shift from APP695 to Kunitz protease inhibitory domain (KPI) containing APPs (KPI-APPs), isoforms exhibiting an important amyloidogenic potential. Conversely, after synaptic NMDAR activation, we failed to detect any KPI-APP expression and neuronal Aβ production was not modified. Calcium imaging data showed that intracellular calcium concentration after extrasynaptic NMDAR stimulation was lower than after synaptic activation. This suggests distinct signaling pathways for each pool of receptors. We found that modification of neuronal APP expression pattern triggered by extrasynaptic NMDAR activation was regulated at an alternative splicing level involving calcium-/calmodulin-dependent protein kinase IV, but overall APP expression remained identical. Finally, memantine dose-dependently inhibited extrasynaptic NMDAR-induced KPI-APPs expression as well as neuronal Aβ release. Altogether, these data suggest that a chronic activation of extrasynaptic NMDAR promotes amyloidogenic KPI-APP expression leading to neuronal Aβ release, representing a causal risk factor for developing AD.

C. elegans STRADalpha and SAD cooperatively regulate neuronal polarity and synaptic organization.

PubMed

Kim, Joanne S M; Hung, Wesley; Narbonne, Patrick; Roy, Richard; Zhen, Mei

2010-01-01

Neurons are polarized cells with morphologically and functionally distinct axons and dendrites. The SAD kinases are crucial for establishing the axon-dendrite identity across species. Previous studies suggest that a tumour suppressor kinase, LKB1, in the presence of a pseudokinase, STRADalpha, initiates axonal differentiation and growth through activating the SAD kinases in vertebrate neurons. STRADalpha was implicated in the localization, stabilization and activation of LKB1 in various cell culture studies. Its in vivo functions, however, have not been examined. In our present study, we analyzed the neuronal phenotypes of the first loss-of-function mutants for STRADalpha and examined their genetic interactions with LKB1 and SAD in C. elegans. Unexpectedly, only the C. elegans STRADalpha, STRD-1, functions exclusively through the SAD kinase, SAD-1, to regulate neuronal polarity and synaptic organization. Moreover, STRD-1 tightly associates with SAD-1 to coordinate its synaptic localizations. By contrast, the C. elegans LKB1, PAR-4, also functions in an additional genetic pathway independently of SAD-1 and STRD-1 to regulate neuronal polarity. We propose that STRD-1 establishes neuronal polarity and organizes synaptic proteins in a complex with the SAD-1 kinase. Our findings suggest that instead of a single, linear genetic pathway, STRADalpha and LKB1 regulate neuronal development through multiple effectors that are shared in some cellular contexts but distinct in others.

Transcription factor REST negatively influences the protein kinase C-dependent up-regulation of human mu-opioid receptor gene transcription.

PubMed

Bedini, Andrea; Baiula, Monica; Carbonari, Gioia; Spampinato, Santi

2010-01-01

Mu-opioid receptor expression increases during neurogenesis, regulates the survival of maturing neurons and is implicated in ischemia-induced neuronal death. The repressor element 1 silencing transcription factor (REST), a regulator of a subset of genes in differentiating and post-mitotic neurons, is involved in its transcriptional repression. Extracellular signaling molecules and mechanisms that control the human mu-opioid receptor (hMOR) gene transcription are not clearly understood. We examined the role of protein kinase C (PKC) on hMOR transcription in a model of neuronal cells and in the context of the potential influence of REST. In native SH-SY5Y neuroblastoma cells, PKC activation with phorbol 12-myristate 13-acetate (PMA, 16 nM, 24h) down-regulated hMOR transcription and concomitantly elevated the REST binding activity to repressor element 1 of the hMOR promoter. In contrast, PMA activated hMOR gene transcription when REST expression was knocked down by an antisense strategy or by retinoic acid-induced cell differentiation. PMA acts through a PKC-dependent pathway requiring downstream MAP kinases and the transcription factor AP-1. In a series of hMOR-luciferase promoter/reporter constructs transfected into SH-SY5Y cells and PC12 cells, PMA up-regulated hMOR transcription in PC12 cells lacking REST, and in SH-SY5Y cells either transfected with constructs deficient in the REST DNA binding element or when REST was down-regulated in retinoic acid-differentiated cells. These findings help explain how hMOR transcription is regulated and may clarify its contribution to epigenetic modifications and reprogramming of differentiated neuronal cells exposed to PKC-activating agents. Copyright 2009 Elsevier Ltd. All rights reserved.

Spatiotemporal intracellular dynamics of neurotrophin and its receptors. Implications for neurotrophin signaling and neuronal function.

PubMed

Bronfman, F C; Lazo, O M; Flores, C; Escudero, C A

2014-01-01

Neurons possess a polarized morphology specialized to contribute to neuronal networks, and this morphology imposes an important challenge for neuronal signaling and communication. The physiology of the network is regulated by neurotrophic factors that are secreted in an activity-dependent manner modulating neuronal connectivity. Neurotrophins are a well-known family of neurotrophic factors that, together with their cognate receptors, the Trks and the p75 neurotrophin receptor, regulate neuronal plasticity and survival and determine the neuronal phenotype in healthy and regenerating neurons. Is it now becoming clear that neurotrophin signaling and vesicular transport are coordinated to modify neuronal function because disturbances of vesicular transport mechanisms lead to disturbed neurotrophin signaling and to diseases of the nervous system. This chapter summarizes our current understanding of how the regulated secretion of neurotrophin, the distribution of neurotrophin receptors in different locations of neurons, and the intracellular transport of neurotrophin-induced signaling in distal processes are achieved to allow coordinated neurotrophin signaling in the cell body and axons.

NMDA receptor dependent PGC-1alpha up-regulation protects the cortical neuron against oxygen-glucose deprivation/reperfusion injury.

PubMed

Luo, Yun; Zhu, Wenjing; Jia, Jia; Zhang, Chenyu; Xu, Yun

2009-09-01

The peroxisome proliferator activated receptor coactivator 1 alpha (PGC-1alpha) is a nuclear transcriptional coactivator that is widely expressed in the brain areas. Over-expression of PGC-1alpha can protect neuronal cells from oxidant-induced injury. The purpose of the current study is to investigate the role of PGC-1alpha in the oxygen (anoxia) deprivation (OGD) neurons. The PGC-1alpha mRNA and protein level between control and OGD neurons were examined by real-time PCR and Western blot. More PGC-1alpha expression was found in the OGD neurons compared with the normal group. Over-expression of PGC-1alpha suppressed cell apoptosis while inhibition of the PGC-1alpha expression induced cell apoptosis in OGD neurons. Furthermore, increase of PGC-1alpha resulted in activation of N-methyl-D-aspartate (NMDA) receptor, p38, and ERK mitogen-activated protein kinase (MAPK) pathway. The blocking of the NMDA receptor by its antagonists MK-801 reduced PGC-1alpha mRNA expression in OGD neurons, while NMDA itself can directly induce the expression of PGC-1alpha in neuronal cells. At the same time, PD98059 (ERK MAPK inhibitor) and SB203580 (P38 MAPK inhibitor) also prevented the up-regulation of PGC-1alpha in OGD neurons and MK801 can inhibit the expression of P38 and ERK MAPK. These data suggested that the expression of PGC-1alpha was up-regulated in OGD mice cortical neurons, which protected the neurons against OGD injury. Moreover, this effect was correlated to the NMDA receptor and the ERK and P38 MAPK pathway. The protective effect of PGC-1alpha on OGD cortical neurons may be useful for stroke therapy.

The Role of D2-Autoreceptors in Regulating Dopamine Neuron Activity and Transmission

PubMed Central

Ford, Christopher P

2014-01-01

Dopamine D2-autoreceptors play a key role in regulating the activity of dopamine neurons and control the synthesis, release and uptake of dopamine. These Gi/o-coupled inhibitory receptors play a major part in shaping dopamine transmission. Found at both somatodendritic and axonal sites, autoreceptors regulate the firing patterns of dopamine neurons and control the timing and amount of dopamine released from their terminals in target regions. Alterations in the expression and activity of autoreceptors are thought to contribute to Parkinson’s disease as well as schizophrenia, drug addiction and attention deficit hyperactivity disorder (ADHD), which emphasizes the importance of D2-autoreceptors in regulating the dopamine system. This review will summarize the cellular actions of dopamine autoreceptors and discuss recent advances that have furthered our understanding of the mechanisms by which D2-receptors control dopamine transmission. PMID:24463000

Food-derived sensory cues modulate longevity via distinct neuroendocrine insulin-like peptides.

PubMed

Artan, Murat; Jeong, Dae-Eun; Lee, Dongyeop; Kim, Young-Il; Son, Heehwa G; Husain, Zahabiya; Kim, Jinmahn; Altintas, Ozlem; Kim, Kyuhyung; Alcedo, Joy; Lee, Seung-Jae V

2016-05-01

Environmental fluctuations influence organismal aging by affecting various regulatory systems. One such system involves sensory neurons, which affect life span in many species. However, how sensory neurons coordinate organismal aging in response to changes in environmental signals remains elusive. Here, we found that a subset of sensory neurons shortens Caenorhabditis elegans' life span by differentially regulating the expression of a specific insulin-like peptide (ILP), INS-6. Notably, treatment with food-derived cues or optogenetic activation of sensory neurons significantly increases ins-6 expression and decreases life span. INS-6 in turn relays the longevity signals to nonneuronal tissues by decreasing the activity of the transcription factor DAF-16/FOXO. Together, our study delineates a mechanism through which environmental sensory cues regulate aging rates by modulating the activities of specific sensory neurons and ILPs. © 2016 Artan et al.; Published by Cold Spring Harbor Laboratory Press.

Excitatory motor neurons are local oscillators for backward locomotion.

PubMed

Gao, Shangbang; Guan, Sihui Asuka; Fouad, Anthony D; Meng, Jun; Kawano, Taizo; Huang, Yung-Chi; Li, Yi; Alcaire, Salvador; Hung, Wesley; Lu, Yangning; Qi, Yingchuan Billy; Jin, Yishi; Alkema, Mark; Fang-Yen, Christopher; Zhen, Mei

2018-01-23

Cell- or network-driven oscillators underlie motor rhythmicity. The identity of C. elegans oscillators remains unknown. Through cell ablation, electrophysiology, and calcium imaging, we show: (1) forward and backward locomotion is driven by different oscillators; (2) the cholinergic and excitatory A-class motor neurons exhibit intrinsic and oscillatory activity that is sufficient to drive backward locomotion in the absence of premotor interneurons; (3) the UNC-2 P/Q/N high-voltage-activated calcium current underlies A motor neuron's oscillation; (4) descending premotor interneurons AVA, via an evolutionarily conserved, mixed gap junction and chemical synapse configuration, exert state-dependent inhibition and potentiation of A motor neuron's intrinsic activity to regulate backward locomotion. Thus, motor neurons themselves derive rhythms, which are dually regulated by the descending interneurons to control the reversal motor state. These and previous findings exemplify compression: essential circuit properties are conserved but executed by fewer numbers and layers of neurons in a small locomotor network. © 2017, Gao et al.

TDP-43 regulates the microprocessor complex activity during in vitro neuronal differentiation.

PubMed

Di Carlo, Valerio; Grossi, Elena; Laneve, Pietro; Morlando, Mariangela; Dini Modigliani, Stefano; Ballarino, Monica; Bozzoni, Irene; Caffarelli, Elisa

2013-12-01

TDP-43 (TAR DNA-binding protein 43) is an RNA-binding protein implicated in RNA metabolism at several levels. Even if ubiquitously expressed, it is considered as a neuronal activity-responsive factor and a major signature for neurological pathologies, making the comprehension of its activity in the nervous system a very challenging issue. TDP-43 has also been described as an accessory component of the Drosha-DGCR8 (DiGeorge syndrome critical region gene 8) microprocessor complex, which is crucially involved in basal and tissue-specific RNA processing events. In the present study, we exploited in vitro neuronal differentiation systems to investigate the TDP-43 demand for the microprocessor function, focusing on both its canonical microRNA biosynthetic activity and its alternative role as a post-transcriptional regulator of gene expression. Our findings reveal a novel role for TDP-43 as an essential factor that controls the stability of Drosha protein during neuronal differentiation, thus globally affecting the production of microRNAs. We also demonstrate that TDP-43 is required for the Drosha-mediated regulation of Neurogenin 2, a master gene orchestrating neurogenesis, whereas post-transcriptional control of Dgcr8, another Drosha target, resulted to be TDP-43-independent. These results implicate a previously uncovered contribution of TDP-43 in regulating the abundance and the substrate specificity of the microprocessor complex and provide new insights into TDP-43 as a key player in neuronal differentiation.

A small group of neurosecretory cells expressing the transcriptional regulator apontic and the neuropeptide corazonin mediate ethanol sedation in Drosophila.

PubMed

McClure, Kimberly D; Heberlein, Ulrike

2013-02-27

In the fruit fly Drosophila melanogaster, as in mammals, acute exposure to a high dose of ethanol leads to stereotypical behavioral changes beginning with increased activity, followed by incoordination, loss of postural control, and eventually, sedation. The mechanism(s) by which ethanol impacts the CNS leading to ethanol-induced sedation and the genes required for normal sedation sensitivity remain largely unknown. Here we identify the gene apontic (apt), an Myb/SANT-containing transcription factor that is required in the nervous system for normal sensitivity to ethanol sedation. Using genetic and behavioral analyses, we show that apt mediates sensitivity to ethanol sedation by acting in a small set of neurons that express Corazonin (Crz), a neuropeptide likely involved in the physiological response to stress. The activity of Crz neurons regulates the behavioral response to ethanol, as silencing and activating these neurons affects sedation sensitivity in opposite ways. Furthermore, this effect is mediated by Crz, as flies with reduced crz expression show reduced sensitivity to ethanol sedation. Finally, we find that both apt and crz are rapidly upregulated by acute ethanol exposure. Thus, we have identified two genes and a small set of peptidergic neurons that regulate sensitivity to ethanol-induced sedation. We propose that Apt regulates the activity of Crz neurons and/or release of the neuropeptide during ethanol exposure.

A Small Group of Neurosecretory Cells Expressing the Transcriptional Regulator apontic and the Neuropeptide corazonin Mediate Ethanol Sedation in Drosophila

PubMed Central

2013-01-01

In the fruit fly Drosophila melanogaster, as in mammals, acute exposure to a high dose of ethanol leads to stereotypical behavioral changes beginning with increased activity, followed by incoordination, loss of postural control, and eventually, sedation. The mechanism(s) by which ethanol impacts the CNS leading to ethanol-induced sedation and the genes required for normal sedation sensitivity remain largely unknown. Here we identify the gene apontic (apt), an Myb/SANT-containing transcription factor that is required in the nervous system for normal sensitivity to ethanol sedation. Using genetic and behavioral analyses, we show that apt mediates sensitivity to ethanol sedation by acting in a small set of neurons that express Corazonin (Crz), a neuropeptide likely involved in the physiological response to stress. The activity of Crz neurons regulates the behavioral response to ethanol, as silencing and activating these neurons affects sedation sensitivity in opposite ways. Furthermore, this effect is mediated by Crz, as flies with reduced crz expression show reduced sensitivity to ethanol sedation. Finally, we find that both apt and crz are rapidly upregulated by acute ethanol exposure. Thus, we have identified two genes and a small set of peptidergic neurons that regulate sensitivity to ethanol-induced sedation. We propose that Apt regulates the activity of Crz neurons and/or release of the neuropeptide during ethanol exposure. PMID:23447613

ERK1/2 mediates glucose-regulated POMC gene expression in hypothalamic neurons.

PubMed

Zhang, Juan; Zhou, Yunting; Chen, Cheng; Yu, Feiyuan; Wang, Yun; Gu, Jiang; Ma, Lian; Ho, Guyu

2015-04-01

Hypothalamic glucose-sensing neurons regulate the expression of genes encoding feeding-related neuropetides POMC, AgRP, and NPY - the key components governing metabolic homeostasis. AMP-activated protein kinase (AMPK) is postulated to be the molecular mediator relaying glucose signals to regulate the expression of these neuropeptides. Whether other signaling mediator(s) plays a role is not clear. In this study, we investigated the role of ERK1/2 using primary hypothalamic neurons as the model system. The primary neurons were differentiated from hypothalamic progenitor cells. The differentiated neurons possessed the characteristic neuronal cell morphology and expressed neuronal post-mitotic markers as well as leptin-regulated orexigenic POMC and anorexigenic AgRP/NPY genes. Treatment of cells with glucose dose-dependently increased POMC and decreased AgRP/NPY expression with a concurrent suppression of AMPK phosphorylation. In addition, glucose treatment dose-dependently increased the ERK1/2 phosphorylation. Blockade of ERK1/2 activity with its specific inhibitor PD98059 partially (approximately 50%) abolished glucose-induced POMC expression, but had little effect on AgRP/NPY expression. Conversely, blockade of AMPK activity with its specific inhibitor produced a partial (approximately 50%) reversion of low-glucose-suppressed POMC expression, but almost completely blunted the low-glucose-induced AgRP/NPY expression. The results indicate that ERK1/2 mediated POMC but not AgRP/NPY expression. Confirming the in vitro findings, i.c.v. administration of PD98059 in rats similarly attenuated glucose-induced POMC expression in the hypothalamus, but again had little effect on AgRP/NPY expression. The results are indicative of a novel role of ERK1/2 in glucose-regulated POMC expression and offer new mechanistic insights into hypothalamic glucose sensing. © 2015 Society for Endocrinology.

Activity of Raphé Serotonergic Neurons Controls Emotional Behaviors.

PubMed

Teissier, Anne; Chemiakine, Alexei; Inbar, Benjamin; Bagchi, Sneha; Ray, Russell S; Palmiter, Richard D; Dymecki, Susan M; Moore, Holly; Ansorge, Mark S

2015-12-01

Despite the well-established role of serotonin signaling in mood regulation, causal relationships between serotonergic neuronal activity and behavior remain poorly understood. Using a pharmacogenetic approach, we find that selectively increasing serotonergic neuronal activity in wild-type mice is anxiogenic and reduces floating in the forced-swim test, whereas inhibition has no effect on the same measures. In a developmental mouse model of altered emotional behavior, increased anxiety and depression-like behaviors correlate with reduced dorsal raphé and increased median raphé serotonergic activity. These mice display blunted responses to serotonergic stimulation and behavioral rescues through serotonergic inhibition. Furthermore, we identify opposing consequences of dorsal versus median raphé serotonergic neuron inhibition on floating behavior, together suggesting that median raphé hyperactivity increases anxiety, whereas a low dorsal/median raphé serotonergic activity ratio increases depression-like behavior. Thus, we find a critical role of serotonergic neuronal activity in emotional regulation and uncover opposing roles of median and dorsal raphé function. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Insulin-like growth factor-1 inhibits adult supraoptic neurons via complementary modulation of mechanoreceptors and glycine receptors.

PubMed

Ster, Jeanne; Colomer, Claude; Monzo, Cécile; Duvoid-Guillou, Anne; Moos, Françoise; Alonso, Gérard; Hussy, Nicolas

2005-03-02

In the CNS, insulin-like growth factor-1 (IGF-1) is mainly known for its trophic effect both during development and in adulthood. Here, we show than in adult rat supraoptic nucleus (SON), IGF-1 receptor immunoreactivity is present in neurons, whereas IGF-1 immunoreactivity is found principally in astrocytes and more moderately in neurons. In vivo application of IGF-1 within the SON acutely inhibits the activity of both vasopressin and oxytocin neurons, the two populations of SON neuroendocrine cells. Recordings of acutely isolated SON neurons showed that this inhibition occurs through two rapid and reversible mechanisms, both involving the neuronal IGF-1 receptor but different intracellular messengers. IGF-1 inhibits Gd3+-sensitive and osmosensitive mechanoreceptor cation current via phosphatidylinositol-3 (PI3) kinase activation. IGF-1 also potentiates taurine-activated glycine receptor (GlyR) Cl- currents by increasing the agonist sensitivity through a extremely rapid (within a second) PI3 kinase-independent mechanism. Both mechanoreceptor channels and GlyR, which form the excitatory and inhibitory components of SON neuron osmosensitivity, are active at rest, and their respective inhibition and potentiation will both be inhibitory, leading to strong decrease in neuronal activity. It will be of interest to determine whether IGF-1 is released by neurons, thus participating in an inhibitory autocontrol, or astrocytes, then joining the growing family of glia-to-neuron transmitters that modulate neuronal and synaptic activity. Through the opposite and complementary acute regulation of mechanoreceptors and GlyR, IGF-1 appears as a new important neuromodulator in the adult CNS, participating in the complex integration of neural messages that regulates the level of neuronal excitability.

p35 Regulates the CRM1-Dependent Nucleocytoplasmic Shuttling of Nuclear Hormone Receptor Coregulator-Interacting Factor 1 (NIF-1)

PubMed Central

Zhao, Xiao-Su; Fu, Wing-Yu; Chien, Winnie W. Y.; Li, Zhen; Fu, Amy K. Y.; Ip, Nancy Y.

2014-01-01

Cyclin-dependent kinase 5 (Cdk5) is a proline-directed serine/threonine kinase, which plays critical roles in a wide spectrum of neuronal functions including neuronal survival, neurite outgrowth, and synapse development and plasticity. Cdk5 activity is controlled by its specific activators: p35 or p39. While knockout studies reveal that Cdk5/p35 is critical for neuronal migration during early brain development, functions of Cdk5/p35 have been unraveled through the identification of the interacting proteins of p35, most of which are Cdk5/p35 substrates. However, it remains unclear whether p35 can regulate neuronal functions independent of Cdk5 activity. Here, we report that a nuclear protein, nuclear hormone receptor coregulator (NRC)-interacting factor 1 (NIF-1), is a new interacting partner of p35. Interestingly, p35 regulates the functions of NIF-1 independent of Cdk5 activity. NIF-1 was initially discovered as a transcriptional regulator that enhances the transcriptional activity of nuclear hormone receptors. Our results show that p35 interacts with NIF-1 and regulates its nucleocytoplasmic trafficking via the nuclear export pathway. Furthermore, we identified a nuclear export signal on p35; mutation of this site or blockade of the CRM1/exportin-dependent nuclear export pathway resulted in the nuclear accumulation of p35. Intriguingly, blocking the nuclear export of p35 attenuated the nuclear accumulation of NIF-1. These findings reveal a new p35-dependent mechanism in transcriptional regulation that involves the nucleocytoplasmic shuttling of transcription regulators. PMID:25329792

p35 regulates the CRM1-dependent nucleocytoplasmic shuttling of nuclear hormone receptor coregulator-interacting factor 1 (NIF-1).

PubMed

Zhao, Xiao-Su; Fu, Wing-Yu; Chien, Winnie W Y; Li, Zhen; Fu, Amy K Y; Ip, Nancy Y

2014-01-01

Cyclin-dependent kinase 5 (Cdk5) is a proline-directed serine/threonine kinase, which plays critical roles in a wide spectrum of neuronal functions including neuronal survival, neurite outgrowth, and synapse development and plasticity. Cdk5 activity is controlled by its specific activators: p35 or p39. While knockout studies reveal that Cdk5/p35 is critical for neuronal migration during early brain development, functions of Cdk5/p35 have been unraveled through the identification of the interacting proteins of p35, most of which are Cdk5/p35 substrates. However, it remains unclear whether p35 can regulate neuronal functions independent of Cdk5 activity. Here, we report that a nuclear protein, nuclear hormone receptor coregulator (NRC)-interacting factor 1 (NIF-1), is a new interacting partner of p35. Interestingly, p35 regulates the functions of NIF-1 independent of Cdk5 activity. NIF-1 was initially discovered as a transcriptional regulator that enhances the transcriptional activity of nuclear hormone receptors. Our results show that p35 interacts with NIF-1 and regulates its nucleocytoplasmic trafficking via the nuclear export pathway. Furthermore, we identified a nuclear export signal on p35; mutation of this site or blockade of the CRM1/exportin-dependent nuclear export pathway resulted in the nuclear accumulation of p35. Intriguingly, blocking the nuclear export of p35 attenuated the nuclear accumulation of NIF-1. These findings reveal a new p35-dependent mechanism in transcriptional regulation that involves the nucleocytoplasmic shuttling of transcription regulators.

Inducible and Conditional Deletion of Extracellular Signal-regulated Kinase 5 Disrupts Adult Hippocampal Neurogenesis*

PubMed Central

Pan, Yung-Wei; Zou, Junhui; Wang, Wenbin; Sakagami, Hiroyuki; Garelick, Michael G.; Abel, Glen; Kuo, Chay T.; Storm, Daniel R.; Xia, Zhengui

2012-01-01

Recent studies have led to the exciting idea that adult-born neurons in the dentate gyrus of the hippocampus may play a role in hippocampus-dependent memory formation. However, signaling mechanisms that regulate adult hippocampal neurogenesis are not well defined. Here we report that extracellular signal-regulated kinase 5 (ERK5), a member of the mitogen-activated protein kinase family, is selectively expressed in the neurogenic regions of the adult mouse brain. We present evidence that shRNA suppression of ERK5 in adult hippocampal neural stem/progenitor cells (aNPCs) reduces the number of neurons while increasing the number of cells expressing markers for stem/progenitor cells or proliferation. Furthermore, shERK5 attenuates both transcription and neuronal differentiation mediated by Neurogenin 2, a transcription factor expressed in adult hippocampal neural progenitor cells. By contrast, ectopic activation of endogenous ERK5 signaling via expression of constitutive active MEK5, an upstream activating kinase for ERK5, promotes neurogenesis in cultured aNPCs and in the dentate gyrus of the mouse brain. Moreover, neurotrophins including NT3 activate ERK5 and stimulate neuronal differentiation in aNPCs in an ERK5-dependent manner. Finally, inducible and conditional deletion of ERK5 specifically in the neurogenic regions of the adult mouse brain delays the normal progression of neuronal differentiation and attenuates adult neurogenesis in vivo. These data suggest ERK5 signaling as a critical regulator of adult hippocampal neurogenesis. PMID:22645146

A Sodium Leak Current Regulates Pacemaker Activity of Adult Central Pattern Generator Neurons in Lymnaea Stagnalis

PubMed Central

Lu, Tom Z.; Feng, Zhong-Ping

2011-01-01

The resting membrane potential of the pacemaker neurons is one of the essential mechanisms underlying rhythm generation. In this study, we described the biophysical properties of an uncharacterized channel (U-type channel) and investigated the role of the channel in the rhythmic activity of a respiratory pacemaker neuron and the respiratory behaviour in adult freshwater snail Lymnaea stagnalis. Our results show that the channel conducts an inward leak current carried by Na+ (ILeak-Na). The ILeak-Na contributed to the resting membrane potential and was required for maintaining rhythmic action potential bursting activity of the identified pacemaker RPeD1 neurons. Partial knockdown of the U-type channel suppressed the aerial respiratory behaviour of the adult snail in vivo. These findings identified the Na+ leak conductance via the U-type channel, likely a NALCN-like channel, as one of the fundamental mechanisms regulating rhythm activity of pacemaker neurons and respiratory behaviour in adult animals. PMID:21526173

Activation of anorexigenic pro-opiomelanocortin neurones during refeeding is independent of vagal and brainstem inputs.

PubMed

Fekete, C; Zséli, G; Singru, P S; Kádár, A; Wittmann, G; Füzesi, T; El-Bermani, W; Lechan, R M

2012-11-01

After fasting, satiety is observed within 2 h after reintroducing food, accompanied by activation of anorexigenic, pro-opiomelanocortin (POMC)-synthesising neurones in the arcuate nucleus (ARC), indicative of the critical role that α-melanocyte-stimulating hormone has in the regulation of meal size during refeeding. To determine whether refeeding-induced activation of POMC neurones in the arcuate is dependent upon the vagus nerve and/or ascending brainstem pathways, bilateral subdiaphragmatic vagotomy or transection of the afferent brainstem input to one side of the ARC was performed. One day after vagotomy or 2 weeks after brain surgery, animals were fasted and then refed for 2 h. Sections containing the ARC from vagotomised animals or animals with effective transection were immunostained for c-Fos and POMC to detect refeeding-induced activation of POMC neurones. Quantitative analyses of double-labelled preparations demonstrated that sham-operated and vagotomised animals markedly increased the number of c-Fos-immunoreactive (-IR) POMC neurones with refeeding. Furthermore, transection of the ascending brainstem pathway had no effect on diminishing c-Fos-immunoreactivity in POMC neurones on either side of the ARC, although it did diminish activation in a separate, subpopulation of neurones in the dorsomedial posterior ARC (dmpARC) on the transected side. We conclude that inputs mediated via the vagus nerve and/or arising from the brainstem do not have a primary role in refeeding-induced activation of POMC neurones in the ARC, and propose that these neurones may be activated solely by direct effects of circulating hormones/metabolites during refeeding. Activation of the dmpARC by refeeding indicates a previously unrecognised role for these neurones in appetite regulation in the rat. © 2012 The Authors. Journal of Neuroendocrinology © 2012 British Society for Neuroendocrinology.

Essential role of the cAMP-cAMP response-element binding protein pathway in opiate-induced homeostatic adaptations of locus coeruleus neurons.

PubMed

Cao, Jun-Li; Vialou, Vincent F; Lobo, Mary Kay; Robison, Alfred J; Neve, Rachael L; Cooper, Donald C; Nestler, Eric J; Han, Ming-Hu

2010-09-28

Excessive inhibition of brain neurons in primary or slice cultures can induce homeostatic intrinsic plasticity, but the functional role and underlying molecular mechanisms of such plasticity are poorly understood. Here, we developed an ex vivo locus coeruleus (LC) slice culture system and successfully recapitulated the opiate-induced homeostatic adaptation in electrical activity of LC neurons seen in vivo. We investigated the mechanisms underlying this adaptation in LC slice cultures by use of viral-mediated gene transfer and genetic mutant mice. We found that short-term morphine treatment of slice cultures almost completely abolished the firing of LC neurons, whereas chronic morphine treatment increased LC neuronal excitability as revealed during withdrawal. This increased excitability was mediated by direct activation of opioid receptors and up-regulation of the cAMP pathway and accompanied by increased cAMP response-element binding protein (CREB) activity. Overexpression of a dominant negative CREB mutant blocked the increase in LC excitability induced by morphine- or cAMP-pathway activation. Knockdown of CREB in slice cultures from floxed CREB mice similarly decreased LC excitability. Furthermore, the ability of morphine or CREB overexpression to up-regulate LC firing was blocked by knockout of the CREB target adenylyl cyclase 8. Together, these findings provide direct evidence that prolonged exposure to morphine induces homeostatic plasticity intrinsic to LC neurons, involving up-regulation of the cAMP-CREB signaling pathway, which then enhances LC neuronal excitability.

Amitriptyline Activates TrkA to Aid Neuronal Growth and Attenuate Anesthesia-Induced Neurodegeneration in Rat Dorsal Root Ganglion Neurons

PubMed Central

Zheng, Xiaochun; Chen, Feng; Zheng, Ting; Huang, Fengyi; Chen, Jianghu; Tu, Wenshao

2016-01-01

Abstract Tricyclic antidepressant amitriptyline (AM) has been shown to exert neurotrophic activity on neurons. We thus explored whether AM may aid the neuronal development and protect anesthesia-induced neuro-injury in young spinal cord dorsal root ganglion (DRG) neurons. The DRG explants were prepared from 1-day-old rats. The effect of AM on aiding DRG neural development was examined by immunohistochemistry at dose-dependent manner. AM-induced changes in gene and protein expressions, and also phosphorylation states of tyrosine kinases receptor A (TrkA) and B (TrkB) in DRG, were examined by quantitative real-time polymerase chain reaction and western blot. The effect of AM on attenuating lidocaine-induced DRG neurodegeneration was examined by immunohistochemistry, and small interfering RNA (siRNA)-mediated TrkA/B down-regulation. Amitriptyline stimulated DRG neuronal development in dose-dependent manner, but exerted toxic effect at concentrations higher than 10 M. AM activated TrkA in DRG through phosphorylation, whereas it had little effect on TrkB-signaling pathway. AM reduced lidocaine-induced DRG neurodegeneration by regenerating neurites and growth cones. Moreover, the neuroprotection of AM on lidocaine-injured neurodegeneration was blocked by siRNA-mediated TrkA down-regulation, but not by TrkB down-regulation. Amitriptyline facilitated neuronal development and had protective effect on lidocaine-induced neurodegeneration, very likely through the activation of TrkA-signaling pathway in DRG. PMID:27149473

Neuronal regulation of homeostasis by nutrient sensing.

PubMed

Lam, Tony K T

2010-04-01

In type 2 diabetes and obesity, the homeostatic control of glucose and energy balance is impaired, leading to hyperglycemia and hyperphagia. Recent studies indicate that nutrient-sensing mechanisms in the body activate negative-feedback systems to regulate energy and glucose homeostasis through a neuronal network. Direct metabolic signaling within the intestine activates gut-brain and gut-brain-liver axes to regulate energy and glucose homeostasis, respectively. In parallel, direct metabolism of nutrients within the hypothalamus regulates food intake and blood glucose levels. These findings highlight the importance of the central nervous system in mediating the ability of nutrient sensing to maintain homeostasis. Futhermore, they provide a physiological and neuronal framework by which enhancing or restoring nutrient sensing in the intestine and the brain could normalize energy and glucose homeostasis in diabetes and obesity.

The effects of glycogen synthase kinase-3beta in serotonin neurons.

PubMed

Zhou, Wenjun; Chen, Ligong; Paul, Jodi; Yang, Sufen; Li, Fuzeng; Sampson, Karen; Woodgett, Jim R; Beaulieu, Jean Martin; Gamble, Karen L; Li, Xiaohua

2012-01-01

Glycogen synthase kinase-3 (GSK3) is a constitutively active protein kinase in brain. Increasing evidence has shown that GSK3 acts as a modulator in the serotonin neurotransmission system, including direct interaction with serotonin 1B (5-HT1B) receptors in a highly selective manner and prominent modulating effect on 5-HT1B receptor activity. In this study, we utilized the serotonin neuron-selective GSK3β knockout (snGSK3β-KO) mice to test if GSK3β in serotonin neurons selectively modulates 5-HT1B autoreceptor activity and function. The snGSK3β-KO mice were generated by crossbreeding GSK3β-floxed mice and ePet1-Cre mice. These mice had normal growth and physiological characteristics, similar numbers of tryptophan hydroxylase-2 (TpH2)-expressing serotonin neurons, and the same brain serotonin content as in littermate wild type mice. However, the expression of GSK3β in snGSK3β-KO mice was diminished in TpH2-expressing serotonin neurons. Compared to littermate wild type mice, snGSK3β-KO mice had a reduced response to the 5-HT1B receptor agonist anpirtoline in the regulation of serotonergic neuron firing, cAMP production, and serotonin release, whereas these animals displayed a normal response to the 5-HT1A receptor agonist 8-OH-DPAT. The effect of anpirtoline on the horizontal, center, and vertical activities in the open field test was differentially affected by GSK3β depletion in serotonin neurons, wherein vertical activity, but not horizontal activity, was significantly altered in snGSK3β-KO mice. In addition, there was an enhanced anti-immobility response to anpirtoline in the tail suspension test in snGSK3β-KO mice. Therefore, results of this study demonstrated a serotonin neuron-targeting function of GSK3β by regulating 5-HT1B autoreceptors, which impacts serotonergic neuron firing, serotonin release, and serotonin-regulated behaviors.

Gene expression profile of activated microglia under conditions associated with dopamine neuronal damage.

PubMed

Thomas, David M; Francescutti-Verbeem, Dina M; Kuhn, Donald M

2006-03-01

Microglia are the resident antigen-presenting cells within the central nervous system (CNS), and they serve immune-like functions in protecting the brain against injury and invading pathogens. By contrast, activated microglia can secrete numerous reactants that damage neurons. The pathogenesis of various neurodegenerative diseases has been associated with microglial activation, but the signaling pathways that program a neuronally protective or destructive phenotype in microglia are not known. To increase the understanding of microglial activation, microarray analysis was used to profile the transcriptome of BV-2 microglial cells after activation. Microglia were activated by lipopolysaccharide, the HIV neurotoxic protein TAT, and dopamine quinone, each of which has been linked to dopamine neuronal damage. We identified 210 of 9882 genes whose expression was differentially regulated by all activators (116 increased and 94 decreased in expression). Gene ontology analysis assigned up-regulated genes to a number of specific biological processes and molecular functions, including immune response, inflammation, and cytokine/chemokine activity. Genes down-regulated in expression contribute to conditions that are permissive of microglial migration, lowered adhesion to matrix, lessened phagocytosis, and reduction in receptors that oppose chemotaxis and inflammation. These results elaborate a broad profile of microglial genes whose expression is altered by conditions associated with both neurodegenerative diseases and microglial activation.

Activation of SF1 Neurons in the Ventromedial Hypothalamus by DREADD Technology Increases Insulin Sensitivity in Peripheral Tissues.

PubMed

Coutinho, Eulalia A; Okamoto, Shiki; Ishikawa, Ayako Wendy; Yokota, Shigefumi; Wada, Nobuhiro; Hirabayashi, Takahiro; Saito, Kumiko; Sato, Tatsuya; Takagi, Kazuyo; Wang, Chen-Chi; Kobayashi, Kenta; Ogawa, Yoshihiro; Shioda, Seiji; Yoshimura, Yumiko; Minokoshi, Yasuhiko

2017-09-01

The ventromedial hypothalamus (VMH) regulates glucose and energy metabolism in mammals. Optogenetic stimulation of VMH neurons that express steroidogenic factor 1 (SF1) induces hyperglycemia. However, leptin acting via the VMH stimulates whole-body glucose utilization and insulin sensitivity in some peripheral tissues, and this effect of leptin appears to be mediated by SF1 neurons. We examined the effects of activation of SF1 neurons with DREADD (designer receptors exclusively activated by designer drugs) technology. Activation of SF1 neurons by an intraperitoneal injection of clozapine- N -oxide (CNO), a specific hM3Dq ligand, reduced food intake and increased energy expenditure in mice expressing hM3Dq in SF1 neurons. It also increased whole-body glucose utilization and glucose uptake in red-type skeletal muscle, heart, and interscapular brown adipose tissue, as well as glucose production and glycogen phosphorylase a activity in the liver, thereby maintaining blood glucose levels. During hyperinsulinemic-euglycemic clamp, such activation of SF1 neurons increased insulin-induced glucose uptake in the same peripheral tissues and tended to enhance insulin-induced suppression of glucose production by suppressing gluconeogenic gene expression and glycogen phosphorylase a activity in the liver. DREADD technology is thus an important tool for studies of the role of the brain in the regulation of insulin sensitivity in peripheral tissues. © 2017 by the American Diabetes Association.

Berberine regulates neurite outgrowth through AMPK-dependent pathways by lowering energy status

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Jiaqi; Cao, Yuanzhao; Cheng, Kuoyuan

2015-06-10

As a widely used anti-bacterial agent and a metabolic inhibitor as well as AMP-activated protein kinase (AMPK) activator, berberine (BBR) has been shown to cross the blood–brain barrier. Its efficacy has been investigated in various disease models of the central nervous system. Neurite outgrowth is critical for nervous system development and is a highly energy-dependent process regulated by AMPK-related pathways. In the present study, we aimed to investigate the effects of BBR on AMPK activation and neurite outgrowth in neurons. The neurite outgrowth of primary rat cortical neurons at different stages of polarization was monitored after exposure of BBR. Intracellularmore » energy level, AMPK activation and polarity-related pathways were also inspected. The results showed that BBR suppressed neurite outgrowth and affected cytoskeleton stability in the early stages of neuronal polarization, which was mediated by lowered energy status and AMPK activation. Liver kinase B1 and PI3K–Akt–GSK3β signaling pathways were also involved. In addition, mitochondrial dysfunction and endoplasmic reticulum stress contributed to the lowered energy status induced by BBR. This study highlighted the knowledge of the complex activities of BBR in neurons and corroborated the significance of energy status during the neuronal polarization. - Highlights: • BBR inhibited neurite outgrowth in early stages of neuronal development. • Lowered neuronal energy status was induced by BBR treatment. • Neuronal energy stress induced by BBR activated AMPK-related pathways. • BBR induced mitochondrial dysfunction and endoplasmic reticulum stress.« less

Role of citron kinase in dendritic morphogenesis of cortical neurons.

PubMed

Di Cunto, Ferdinando; Ferrara, Luciana; Curtetti, Roberta; Imarisio, Sara; Guazzone, Simona; Broccoli, Vania; Bulfone, Alessandro; Altruda, Fiorella; Vercelli, Alessandro; Silengo, Lorenzo

2003-05-30

Small GTPases of the rho family regulate the extensive rearrangements of the cytoskeleton that characterize neuronal differentiation. Citron kinase is a target molecule for activated rhoA, previously implicated in control of cytokinesis. We have found that, in addition, it could play an important role in modulating the extension of neuronal processes. Using constitutively active and dominant negative mutants, we showed that citron kinase is involved in the morphologic differentiation of N1E-115 neuroblastoma cells induced by serum starvation. More importantly, quantitative analysis of citron kinase knockout cerebral cortex displayed that this molecule may differentially regulate the morphology of the dendritic compartment in corticocollicular versus callosally-projecting pyramidal neurons.

Connexin-Dependent Neuroglial Networking as a New Therapeutic Target.

PubMed

Charvériat, Mathieu; Naus, Christian C; Leybaert, Luc; Sáez, Juan C; Giaume, Christian

2017-01-01

Astrocytes and neurons dynamically interact during physiological processes, and it is now widely accepted that they are both organized in plastic and tightly regulated networks. Astrocytes are connected through connexin-based gap junction channels, with brain region specificities, and those networks modulate neuronal activities, such as those involved in sleep-wake cycle, cognitive, or sensory functions. Additionally, astrocyte domains have been involved in neurogenesis and neuronal differentiation during development; they participate in the "tripartite synapse" with both pre-synaptic and post-synaptic neurons by tuning down or up neuronal activities through the control of neuronal synaptic strength. Connexin-based hemichannels are also involved in those regulations of neuronal activities, however, this feature will not be considered in the present review. Furthermore, neuronal processes, transmitting electrical signals to chemical synapses, stringently control astroglial connexin expression, and channel functions. Long-range energy trafficking toward neurons through connexin-coupled astrocytes and plasticity of those networks are hence largely dependent on neuronal activity. Such reciprocal interactions between neurons and astrocyte networks involve neurotransmitters, cytokines, endogenous lipids, and peptides released by neurons but also other brain cell types, including microglial and endothelial cells. Over the past 10 years, knowledge about neuroglial interactions has widened and now includes effects of CNS-targeting drugs such as antidepressants, antipsychotics, psychostimulants, or sedatives drugs as potential modulators of connexin function and thus astrocyte networking activity. In physiological situations, neuroglial networking is consequently resulting from a two-way interaction between astrocyte gap junction-mediated networks and those made by neurons. As both cell types are modulated by CNS drugs we postulate that neuroglial networking may emerge as new therapeutic targets in neurological and psychiatric disorders.

Changes in Appetitive Associative Strength Modulates Nucleus Accumbens, But Not Orbitofrontal Cortex Neuronal Ensemble Excitability.

PubMed

Ziminski, Joseph J; Hessler, Sabine; Margetts-Smith, Gabriella; Sieburg, Meike C; Crombag, Hans S; Koya, Eisuke

2017-03-22

Cues that predict the availability of food rewards influence motivational states and elicit food-seeking behaviors. If a cue no longer predicts food availability, then animals may adapt accordingly by inhibiting food-seeking responses. Sparsely activated sets of neurons, coined "neuronal ensembles," have been shown to encode the strength of reward-cue associations. Although alterations in intrinsic excitability have been shown to underlie many learning and memory processes, little is known about these properties specifically on cue-activated neuronal ensembles. We examined the activation patterns of cue-activated orbitofrontal cortex (OFC) and nucleus accumbens (NAc) shell ensembles using wild-type and Fos-GFP mice, which express green fluorescent protein (GFP) in activated neurons, after appetitive conditioning with sucrose and extinction learning. We also investigated the neuronal excitability of recently activated, GFP+ neurons in these brain areas using whole-cell electrophysiology in brain slices. Exposure to a sucrose cue elicited activation of neurons in both the NAc shell and OFC. In the NAc shell, but not the OFC, these activated GFP+ neurons were more excitable than surrounding GFP- neurons. After extinction, the number of neurons activated in both areas was reduced and activated ensembles in neither area exhibited altered excitability. These data suggest that learning-induced alterations in the intrinsic excitability of neuronal ensembles is regulated dynamically across different brain areas. Furthermore, we show that changes in associative strength modulate the excitability profile of activated ensembles in the NAc shell. SIGNIFICANCE STATEMENT Sparsely distributed sets of neurons called "neuronal ensembles" encode learned associations about food and cues predictive of its availability. Widespread changes in neuronal excitability have been observed in limbic brain areas after associative learning, but little is known about the excitability changes that occur specifically on neuronal ensembles that encode appetitive associations. Here, we reveal that sucrose cue exposure recruited a more excitable ensemble in the nucleus accumbens, but not orbitofrontal cortex, compared with their surrounding neurons. This excitability difference was not observed when the cue's salience was diminished after extinction learning. These novel data provide evidence that the intrinsic excitability of appetitive memory-encoding ensembles is regulated differentially across brain areas and adapts dynamically to changes in associative strength. Copyright © 2017 the authors 0270-6474/17/373160-11$15.00/0.

TRPM8 is a neuronal osmosensor that regulates eye blinking in mice

PubMed Central

Quallo, Talisia; Vastani, Nisha; Horridge, Elisabeth; Gentry, Clive; Parra, Andres; Moss, Sian; Viana, Felix; Belmonte, Carlos; Andersson, David A.; Bevan, Stuart

2015-01-01

Specific peripheral sensory neurons respond to increases in extracellular osmolality but the mechanism responsible for excitation is unknown. Here we show that small increases in osmolality excite isolated mouse dorsal root ganglion (DRG) and trigeminal ganglion (TG) neurons expressing the cold-sensitive TRPM8 channel (transient receptor potential channel, subfamily M, member 8). Hyperosmotic responses were abolished by TRPM8 antagonists, and were absent in DRG and TG neurons isolated from Trpm8−/− mice. Heterologously expressed TRPM8 was activated by increased osmolality around physiological levels and inhibited by reduced osmolality. Electrophysiological studies in a mouse corneal preparation demonstrated that osmolality regulated the electrical activity of TRPM8-expressing corneal afferent neurons. Finally, the frequency of eye blinks was reduced in Trpm8−/− compared with wild-type mice and topical administration of a TRPM8 antagonist reduced blinking in wild-type mice. Our findings identify TRPM8 as a peripheral osmosensor responsible for the regulation of normal eye-blinking in mice. PMID:25998021

Effects of continuous hypoxia on energy metabolism in cultured cerebro-cortical neurons.

PubMed

Malthankar-Phatak, Gauri H; Patel, Anant B; Xia, Ying; Hong, Soonsun; Chowdhury, Golam M I; Behar, Kevin L; Orina, Isaac A; Lai, James C K

2008-09-10

Mechanisms underlying hypoxia-induced neuronal adaptation have not been fully elucidated. In the present study we investigated glucose metabolism and the activities of glycolytic and TCA cycle enzymes in cerebro-cortical neurons exposed to hypoxia (3 days in 1% of O2) or normoxia (room air). Hypoxia led to increased activities of LDH (194%), PK (90%), and HK (24%) and decreased activities of CS (15%) and GDH (34%). Neurons were incubated with [1-(13)C]glucose for 45 and 120 min under normoxic or hypoxic (120 min only) conditions and 13C enrichment determined in the medium and cell extract using 1H-{13C}-NMR. In hypoxia-treated neurons [3-(13)C]lactate release into the medium was 428% greater than in normoxia-treated controls (45-min normoxic incubation) and total flux through lactate was increased by 425%. In contrast glucose oxidation was reduced significantly in hypoxia-treated neurons, even when expressed relative to total cellular protein, which correlated with the reduced activities of the measured mitochondrial enzymes. The results suggest that surviving neurons adapt to prolonged hypoxia by up-regulation of glycolysis and down-regulation of oxidative energy metabolism, similar to certain other cell types. The factors leading to adaptation and survival for some neurons but not others remain to be determined.

Oxytocin stimulates hippocampal neurogenesis via oxytocin receptor expressed in CA3 pyramidal neurons.

PubMed

Lin, Yu-Ting; Chen, Chien-Chung; Huang, Chiung-Chun; Nishimori, Katsuhiko; Hsu, Kuei-Sen

2017-09-14

In addition to the regulation of social and emotional behaviors, the hypothalamic neuropeptide oxytocin has been shown to stimulate neurogenesis in adult dentate gyrus; however, the mechanisms underlying the action of oxytocin are still unclear. Taking advantage of the conditional knockout mouse model, we show here that endogenous oxytocin signaling functions in a non-cell autonomous manner to regulate survival and maturation of newly generated dentate granule cells in adult mouse hippocampus via oxytocin receptors expressed in CA3 pyramidal neurons. Through bidirectional chemogenetic manipulations, we also uncover a significant role for CA3 pyramidal neuron activity in regulating adult neurogenesis in the dentate gyrus. Retrograde neuronal tracing combined with immunocytochemistry revealed that the oxytocin neurons in the paraventricular nucleus project directly to the CA3 region of the hippocampus. Our findings reveal a critical role for oxytocin signaling in adult neurogenesis.Oxytocin (OXT) has been implicated in adult neurogenesis. Here the authors show that CA3 pyramidal cells in the adult mouse hippocampus express OXT receptors and receive inputs from hypothalamic OXT neurons; activation of OXT signaling in CA3 pyramidal cells promotes the survival and maturation of newborn neurons in the dentate gyrus in a non-cell autonomous manner.

Bidirectional electromagnetic control of the hypothalamus regulates feeding and metabolism

PubMed Central

Stanley, Sarah A.; Kelly, Leah; Latcha, Kaamashri N.; Schmidt, Sarah F.; Yu, Xiaofei; Nectow, Alexander R.; Sauer, Jeremy; Dyke, Jonathan P.; Dordick, Jonathan S.; Friedman, Jeffrey M.

2016-01-01

Targeted, temporally regulated neural modulation is invaluable in determining the physiological roles of specific neural populations or circuits. Here we describe a system for non-invasive, temporal activation or inhibition of neuronal activity in vivo and its use to study central nervous system control of glucose homeostasis and feeding in mice. We are able to induce neuronal activation remotely using radio waves or magnetic fields via Cre-dependent expression of a GFP-tagged ferritin fusion protein tethered to the cation-conducting transient receptor potential vanilloid 1 (TRPV1) by a camelid anti-GFP antibody (anti-GFP–TRPV1)1. Neuronal inhibition via the same stimuli is achieved by mutating the TRPV1 pore, rendering the channel chloride-permeable. These constructs were targeted to glucose-sensing neurons in the ventromedial hypothalamus in glucokinase–Cre mice, which express Cre in glucose-sensing neurons2. Acute activation of glucose-sensing neurons in this region increases plasma glucose and glucagon, lowers insulin levels and stimulates feeding, while inhibition reduces blood glucose, raises insulin levels and suppresses feeding. These results suggest that pancreatic hormones function as an effector mechanism of central nervous system circuits controlling blood glucose and behaviour. The method we employ obviates the need for permanent implants and could potentially be applied to study other neural processes or used to regulate other, even dispersed, cell types. PMID:27007848

Nuclear Calcium Signaling Controls Expression of a Large Gene Pool: Identification of a Gene Program for Acquired Neuroprotection Induced by Synaptic Activity

PubMed Central

Zhang, Sheng-Jia; Zou, Ming; Lu, Li; Lau, David; Ditzel, Désirée A. W.; Delucinge-Vivier, Celine; Aso, Yoshinori; Descombes, Patrick; Bading, Hilmar

2009-01-01

Synaptic activity can boost neuroprotection through a mechanism that requires synapse-to-nucleus communication and calcium signals in the cell nucleus. Here we show that in hippocampal neurons nuclear calcium is one of the most potent signals in neuronal gene expression. The induction or repression of 185 neuronal activity-regulated genes is dependent upon nuclear calcium signaling. The nuclear calcium-regulated gene pool contains a genomic program that mediates synaptic activity-induced, acquired neuroprotection. The core set of neuroprotective genes consists of 9 principal components, termed Activity-regulated Inhibitor of Death (AID) genes, and includes Atf3, Btg2, GADD45β, GADD45γ, Inhibin β-A, Interferon activated gene 202B, Npas4, Nr4a1, and Serpinb2, which strongly promote survival of cultured hippocampal neurons. Several AID genes provide neuroprotection through a common process that renders mitochondria more resistant to cellular stress and toxic insults. Stereotaxic delivery of AID gene-expressing recombinant adeno-associated viruses to the hippocampus confers protection in vivo against seizure-induced brain damage. Thus, treatments that enhance nuclear calcium signaling or supplement AID genes represent novel therapies to combat neurodegenerative conditions and neuronal cell loss caused by synaptic dysfunction, which may be accompanied by a deregulation of calcium signal initiation and/or propagation to the cell nucleus. PMID:19680447

Retrieval-Induced Upregulation of Tet3 in Pyramidal Neurons of the Dorsal Hippocampus Mediates Cocaine-Associated Memory Reconsolidation.

PubMed

Liu, Cao; Sun, Xue; Wang, Zhilin; Le, Qiumin; Liu, Peipei; Jiang, Changyou; Wang, Feifei; Ma, Lan

2018-03-01

Memory retrieval refers to reexposure to information previously encoded and stored in the brain. Following retrieval, a once-consolidated memory destabilizes and undergoes reconsolidation, during which gene expression changes to restabilize memory. Investigating epigenetic regulation during reconsolidation could provide insights into normal memory formation and pathological memory associated with psychiatric disorders. We used cocaine-induced conditioned place preference to assess the cocaine-associated memory of mice and used chemogenetic methods to manipulate the activity of the pyramidal neurons in the dorsal hippocampus. We isolated the ribosome-associated transcripts from the excitatory neurons in the dorsal hippocampus by RiboTag purification to identify the potential epigenetic regulators, and we specifically knocked down gene expression in pyramidal neurons with a Cre-dependent lentivirus. Chemogenetically silencing the activity of the pyramidal neurons in the dorsal hippocampus immediately after memory retrieval markedly impaired memory reconsolidation, and the ribosome-associated mRNA level of the ten-eleven translocation (Tet) family methylcytosine dioxygenase Tet3, but not Tet1 or Tet2, was dramatically upregulated 10 minutes after memory retrieval. The protein level of Tet3 in the dorsal hippocampus but not in the anterior cingulate cortex was dramatically increased 1 hour after memory retrieval. Specifically, knockdown of Tet3 in pyramidal neurons in the dorsal hippocampus decreased the activation of pyramidal neurons and impaired the reconsolidation of cocaine-associated memory. Our findings highlight the new function of the DNA demethylation regulator Tet3 in pyramidal neurons of the dorsal hippocampus in regulating the reconsolidation of cocaine-associated memory. © The Author 2017. Published by Oxford University Press on behalf of CINP.

Gemfibrozil and fenofibrate, Food and Drug Administration-approved lipid-lowering drugs, up-regulate tripeptidyl-peptidase 1 in brain cells via peroxisome proliferator-activated receptor α: implications for late infantile Batten disease therapy.

PubMed

Ghosh, Arunava; Corbett, Grant T; Gonzalez, Frank J; Pahan, Kalipada

2012-11-09

The classical late infantile neuronal ceroid lipofuscinosis (LINCLs) is an autosomal recessive disease, where the defective gene is Cln2, encoding tripeptidyl-peptidase I (TPP1). At the molecular level, LINCL is caused by accumulation of autofluorescent storage materials in neurons and other cell types. Currently, there is no established treatment for this fatal disease. This study reveals a novel use of gemfibrozil and fenofibrate, Food and Drug Administration-approved lipid-lowering drugs, in up-regulating TPP1 in brain cells. Both gemfibrozil and fenofibrate up-regulated mRNA, protein, and enzymatic activity of TPP1 in primary mouse neurons and astrocytes as well as human astrocytes and neuronal cells. Because gemfibrozil and fenofibrate are known to activate peroxisome proliferator-activated receptor-α (PPARα), the role of PPARα in gemfibrozil- and fenofibrate-mediated up-regulation of TPP1 was investigated revealing that both drugs up-regulated TPP1 mRNA, protein, and enzymatic activity both in vitro and in vivo in wild type (WT) and PPARβ(-/-), but not PPARα(-/-), mice. In an attempt to delineate the mechanism of TPP1 up-regulation, it was found that the effects of the fibrate drugs were abrogated in the absence of retinoid X receptor-α (RXRα), a molecule known to form a heterodimer with PPARα. Accordingly, all-trans-retinoic acid, alone or together with gemfibrozil, up-regulated TPP1. Co-immunoprecipitation and ChIP studies revealed the formation of a PPARα/RXRα heterodimer and binding of the heterodimer to an RXR-binding site on the Cln2 promoter. Together, this study demonstrates a unique mechanism for the up-regulation of TPP1 by fibrate drugs via PPARα/RXRα pathway.

Gemfibrozil and Fenofibrate, Food and Drug Administration-approved Lipid-lowering Drugs, Up-regulate Tripeptidyl-peptidase 1 in Brain Cells via Peroxisome Proliferator-activated Receptor α

PubMed Central

Ghosh, Arunava; Corbett, Grant T.; Gonzalez, Frank J.; Pahan, Kalipada

2012-01-01

The classical late infantile neuronal ceroid lipofuscinosis (LINCLs) is an autosomal recessive disease, where the defective gene is Cln2, encoding tripeptidyl-peptidase I (TPP1). At the molecular level, LINCL is caused by accumulation of autofluorescent storage materials in neurons and other cell types. Currently, there is no established treatment for this fatal disease. This study reveals a novel use of gemfibrozil and fenofibrate, Food and Drug Administration-approved lipid-lowering drugs, in up-regulating TPP1 in brain cells. Both gemfibrozil and fenofibrate up-regulated mRNA, protein, and enzymatic activity of TPP1 in primary mouse neurons and astrocytes as well as human astrocytes and neuronal cells. Because gemfibrozil and fenofibrate are known to activate peroxisome proliferator-activated receptor-α (PPARα), the role of PPARα in gemfibrozil- and fenofibrate-mediated up-regulation of TPP1 was investigated revealing that both drugs up-regulated TPP1 mRNA, protein, and enzymatic activity both in vitro and in vivo in wild type (WT) and PPARβ−/−, but not PPARα−/−, mice. In an attempt to delineate the mechanism of TPP1 up-regulation, it was found that the effects of the fibrate drugs were abrogated in the absence of retinoid X receptor-α (RXRα), a molecule known to form a heterodimer with PPARα. Accordingly, all-trans-retinoic acid, alone or together with gemfibrozil, up-regulated TPP1. Co-immunoprecipitation and ChIP studies revealed the formation of a PPARα/RXRα heterodimer and binding of the heterodimer to an RXR-binding site on the Cln2 promoter. Together, this study demonstrates a unique mechanism for the up-regulation of TPP1 by fibrate drugs via PPARα/RXRα pathway. PMID:22989886

Role of PPARγ in the Differentiation and Function of Neurons

PubMed Central

Quintanilla, Rodrigo A.; Utreras, Elias; Cabezas-Opazo, Fabián A.

2014-01-01

Neuronal processes (neurites and axons) have an important role in brain cells communication and, generally, they are damaged in neurodegenerative diseases. Recent evidence has showed that the activation of PPARγ pathway promoted neuronal differentiation and axon polarity. In addition, activation of PPARγ using thiazolidinediones (TZDs) prevented neurodegeneration by reducing neuronal death, improving mitochondrial function, and decreasing neuroinflammation in neuropathic pain. In this review, we will discuss important evidence that supports a possible role of PPARγ in neuronal development, improvement of neuronal health, and pain signaling. Therefore, activation of PPARγ is a potential target with therapeutic applications against neurodegenerative disorders, brain injury, and pain regulation. PMID:25246934

Gs-coupled GPCR signalling in AgRP neurons triggers sustained increase in food intake.

PubMed

Nakajima, Ken-ichiro; Cui, Zhenzhong; Li, Chia; Meister, Jaroslawna; Cui, Yinghong; Fu, Ou; Smith, Adam S; Jain, Shalini; Lowell, Bradford B; Krashes, Michael J; Wess, Jürgen

2016-01-08

Agouti-related peptide (AgRP) neurons of the hypothalamus play a key role in regulating food intake and body weight, by releasing three different orexigenic molecules: AgRP; GABA; and neuropeptide Y. AgRP neurons express various G protein-coupled receptors (GPCRs) with different coupling properties, including Gs-linked GPCRs. At present, the potential role of Gs-coupled GPCRs in regulating the activity of AgRP neurons remains unknown. Here we show that the activation of Gs-coupled receptors expressed by AgRP neurons leads to a robust and sustained increase in food intake. We also provide detailed mechanistic data linking the stimulation of this class of receptors to the observed feeding phenotype. Moreover, we show that this pathway is clearly distinct from other GPCR signalling cascades that are operative in AgRP neurons. Our data suggest that drugs able to inhibit this signalling pathway may become useful for the treatment of obesity.

The RNA helicase DDX17 controls the transcriptional activity of REST and the expression of proneural microRNAs in neuronal differentiation.

PubMed

Lambert, Marie-Pierre; Terrone, Sophie; Giraud, Guillaume; Benoit-Pilven, Clara; Cluet, David; Combaret, Valérie; Mortreux, Franck; Auboeuf, Didier; Bourgeois, Cyril F

2018-06-21

The Repressor Element 1-silencing transcription factor (REST) represses a number of neuronal genes in non-neuronal cells or in undifferentiated neural progenitors. Here, we report that the DEAD box RNA helicase DDX17 controls important REST-related processes that are critical during the early phases of neuronal differentiation. First, DDX17 associates with REST, promotes its binding to the promoter of a subset of REST-targeted genes and co-regulates REST transcriptional repression activity. During neuronal differentiation, we observed a downregulation of DDX17 along with that of the REST complex that contributes to the activation of neuronal genes. Second, DDX17 and its paralog DDX5 regulate the expression of several proneural microRNAs that are known to target the REST complex during neurogenesis, including miR-26a/b that are also direct regulators of DDX17 expression. In this context, we propose a new mechanism by which RNA helicases can control the biogenesis of intronic miRNAs. We show that the processing of the miR-26a2 precursor is dependent on RNA helicases, owing to an intronic regulatory region that negatively impacts on both miRNA processing and splicing of its host intron. Our work places DDX17 in the heart of a pathway involving REST and miRNAs that allows neuronal gene repression.

[Regulation of the neuronal functional state by ultra low doses of different biologically active substances. Nonspecific effect ].

PubMed

Terekhova, S F; Grechenko, T N

2003-01-01

The role of biologically active substances in ultra-low doses (10(-15)-10(-27) mol/l) is discussed from the different points of view. The most detailed analysis of neurobiological effects produced by these doses can be studied on the preparate of completely isolated molluscan neurones. In this case the possibility arises to control the first modifications of action at the electrophysiological characteristics of neuronal activity. These changes of electrical activity can be regarded as a reaction to biologically active substance. The following characteristics were controlled: the level of membrane resting potential (MP), the electroexcitable membrane and pacemaker mechanism, chemical sensitivity of somatic membrane loci to neurotransmitter acetylcholine (Ach). Several substances were used in these experiments: two kinds of synthetic antioxidant, GABA, ethanol, serotonine, DSIP (delta-sleep inducing peptide), antibiotic ruboxil, nootrop GVS-111. The isolated neurones were placed into the special chamber. All these substances (0.35 ml) were added single dosing into this chamber with living physiological solution in concentration 10(-15)-10(-27) mol/l. The results demonstrated that all substances had initiated the development of prolonged neurophysiological responses. The intensities of neuronal reactions didn't depend in contact period on the concentration and on the type of substance. It is suggested that these data reveal the existence of unknown modes of regulation of neuronal functional states and presence of hidden channel for information transfer and receiving. This different way of regulation is extremely important influence living organisms.

Regulate axon branching by the cyclic GMP pathway via inhibition of glycogen synthase kinase 3 in dorsal root ganglion sensory neurons.

PubMed

Zhao, Zhen; Wang, Zheng; Gu, Ying; Feil, Robert; Hofmann, Franz; Ma, Le

2009-02-04

Cyclic GMP has been proposed to regulate axonal development, but the molecular and cellular mechanisms underlying the formation of axon branches are not well understood. Here, we report the use of rodent embryonic sensory neurons from the dorsal root ganglion (DRG) to demonstrate the role of cGMP signaling in axon branching and to identify the downstream molecular pathway mediating this novel regulation. Pharmacologically, a specific cGMP analog promotes DRG axon branching in culture, and this activity can be achieved by activating the endogenous soluble guanylyl cyclase that produces cGMP. At the molecular level, the cGMP-dependent protein kinase 1 (PrkG1) mediates this activity, as DRG neurons isolated from the kinase-deficient mouse fail to respond to cGMP activation to make branches, whereas overexpression of a PrkG1 mutant with a higher-than-normal basal kinase activity is sufficient to induce branching. In addition, cGMP activation in DRG neurons leads to phosphorylation of glycogen synthase kinase 3 (GSK3), a protein that normally suppresses branching. This interaction is direct, because PrkG1 binds GSK3 in heterologous cells and the purified kinase can phosphorylate GSK3 in vitro. More importantly, overexpression of a dominant active form of GSK3 suppresses cGMP-dependent branching in DRG neurons. Thus, our study establishes an intrinsic signaling cascade that links cGMP activation to GSK3 inhibition in controlling axon branching during sensory axon development.

Adrenoceptor-Mediated Post- and Pre-Synaptic Regulations of the Reticulospinal Neurons in Rat Caudal Pontine Reticular Nucleus.

PubMed

Yang, Nian; Qiao, Qi-Cheng; Liu, Yu-Hui; Zhang, Ji-Qiang; Hu, Zhi-An; Zhang, Jun

2016-12-01

The central noradrenergic system participates in diverse nervous functions. Nevertheless, our knowledge of the action of adrenoceptors in motor regulation is still lacking. Intriguingly, reticulospinal neurons in the caudal pontine reticular nucleus (PnC) receive fairly dense noradrenergic innervation and play an important role in motor control. Here, after demonstrating the expression of α1- and α2-adrenoceptors in the PnC, we found that noradrenaline elicited a post-synaptic effect (inward or outward whole-cell current at -70 mV holding) on PnC reticulospinal neurons. The α1- and α2-adrenoceptors were co-expressed in individual PnC reticulospinal neurons to mediate an inward and an outward current component at -70 mV holding, respectively, which, when superposed, produced the overall post-synaptic effects of noradrenaline (NA). More importantly, the activation of post-synaptic α1- or α2-adrenoceptors indeed exerted opposing modulations (excitation vs. inhibition) on the firing activities of individual PnC reticulospinal neurons. Furthermore, the activation and inhibition of the Na + -permeable non-selective cationic conductance (NSCC) were demonstrated to be coupled to α1- and α2-adrenoceptors, respectively. Additionally, the activation of α2-adrenoceptors activated K + conductance. Pre-synaptically, the α2-adrenoceptors were expressed to attenuate the miniature excitatory postsynaptic current (mEPSC) in PnC reticulospinal neurons, but not to affect the miniature inhibitory postsynaptic current (mIPSC). Consistently, the evoked EPSC in PnC reticulospinal neurons was suppressed after the activation of pre-synaptic α2-adrenoceptors. Thus, the excitatory input and post-synaptic dynamics of PnC reticulospinal neurons are indeed intricately modulated by the activation of α1- and α2-adrenoceptors, through which motor control may be regulated in an adaptive manner by the central noradrenergic system.

Regulation of gonadotropin-releasing hormone neurons by glucose

PubMed Central

Roland, Alison V.; Moenter, Suzanne M.

2011-01-01

Reproduction is influenced by energy balance, but the physiological pathways mediating their relationship have not been fully elucidated. As the central regulators of fertility, gonadotropin-releasing hormone (GnRH) neurons integrate numerous physiological signals, including metabolic cues. Circulating glucose levels regulate GnRH release and may in part mediate the effects of negative energy balance on fertility. Existing evidence suggests that neural pathways originating in the hindbrain, as well as in the hypothalamic feeding nuclei, transmit information concerning glucose availability to GnRH neurons. Here we review recent evidence suggesting that GnRH neurons may directly sense changes in glucose availability by a mechanism involving adenosine monophosphate-activated protein kinase (AMPK). These findings expand our understanding of how metabolic signaling in the brain regulates reproduction. PMID:21855365

GABAA receptor-expressing neurons promote consumption in Drosophila melanogaster.

PubMed

Cheung, Samantha K; Scott, Kristin

2017-01-01

Feeding decisions are highly plastic and bidirectionally regulated by neurons that either promote or inhibit feeding. In Drosophila melanogaster, recent studies have identified four GABAergic interneurons that act as critical brakes to prevent incessant feeding. These GABAergic neurons may inhibit target neurons that drive consumption. Here, we tested this hypothesis by examining GABA receptors and neurons that promote consumption. We find that Resistance to dieldrin (RDL), a GABAA type receptor, is required for proper control of ingestion. Knockdown of Rdl in a subset of neurons causes overconsumption of tastants. Acute activation of these neurons is sufficient to drive consumption of appetitive substances and non-appetitive substances and acute silencing of these neurons decreases consumption. Taken together, these studies identify GABAA receptor-expressing neurons that promote Drosophila ingestive behavior and provide insight into feeding regulation.

Control of food intake and energy expenditure by Nos1 neurons of the paraventricular hypothalamus.

PubMed

Sutton, Amy K; Pei, Hongjuan; Burnett, Korri H; Myers, Martin G; Rhodes, Christopher J; Olson, David P

2014-11-12

The paraventricular nucleus of the hypothalamus (PVH) contains a heterogeneous cluster of Sim1-expressing cell types that comprise a major autonomic output nucleus and play critical roles in the control of food intake and energy homeostasis. The roles of specific PVH neuronal subtypes in energy balance have yet to be defined, however. The PVH contains nitric oxide synthase-1 (Nos1)-expressing (Nos1(PVH)) neurons of unknown function; these represent a subset of the larger population of Sim1-expressing PVH (Sim1(PVH)) neurons. To determine the role of Nos1(PVH) neurons in energy balance, we used Cre-dependent viral vectors to both map their efferent projections and test their functional output in mice. Here we show that Nos1(PVH) neurons project to hindbrain and spinal cord regions important for food intake and energy expenditure control. Moreover, pharmacogenetic activation of Nos1(PVH) neurons suppresses feeding to a similar extent as Sim1(PVH) neurons, and increases energy expenditure and activity. Furthermore, we found that oxytocin-expressing PVH neurons (OXT(PVH)) are a subset of Nos1(PVH) neurons. OXT(PVH) cells project to preganglionic, sympathetic neurons in the thoracic spinal cord and increase energy expenditure upon activation, though not to the same extent as Nos1(PVH) neurons; their activation fails to alter feeding, however. Thus, Nos1(PVH) neurons promote negative energy balance through changes in feeding and energy expenditure, whereas OXT(PVH) neurons regulate energy expenditure alone, suggesting a crucial role for non-OXT Nos1(PVH) neurons in feeding regulation. Copyright © 2014 the authors 0270-6474/14/3415306-13$15.00/0.

Epigenetic Basis of Neuronal and Synaptic Plasticity.

PubMed

Karpova, Nina N; Sales, Amanda J; Joca, Samia R

2017-01-01

Neuronal network and plasticity change as a function of experience. Altered neural connectivity leads to distinct transcriptional programs of neuronal plasticity-related genes. The environmental challenges throughout life may promote long-lasting reprogramming of gene expression and the development of brain disorders. The modifications in neuronal epigenome mediate gene-environmental interactions and are required for activity-dependent regulation of neuronal differentiation, maturation and plasticity. Here, we highlight the latest advances in understanding the role of the main players of epigenetic machinery (DNA methylation and demethylation, histone modifications, chromatin-remodeling enzymes, transposons, and non-coding RNAs) in activity-dependent and long- term neural and synaptic plasticity. The review focuses on both the transcriptional and post-transcriptional regulation of gene expression levels, including the processes of promoter activation, alternative splicing, regulation of stability of gene transcripts by natural antisense RNAs, and alternative polyadenylation. Further, we discuss the epigenetic aspects of impaired neuronal plasticity and the pathogenesis of neurodevelopmental (Rett syndrome, Fragile X Syndrome, genomic imprinting disorders, schizophrenia, and others), stressrelated (mood disorders) and neurodegenerative Alzheimer's, Parkinson's and Huntington's disorders. The review also highlights the pharmacological compounds that modulate epigenetic programming of gene expression, the potential treatment strategies of discussed brain disorders, and the questions that should be addressed during the development of effective and safe approaches for the treatment of brain disorders.

ERK signaling pathway regulates sleep duration through activity-induced gene expression during wakefulness.

PubMed

Mikhail, Cyril; Vaucher, Angélique; Jimenez, Sonia; Tafti, Mehdi

2017-01-24

Wakefulness is accompanied by experience-dependent synaptic plasticity and an increase in activity-regulated gene transcription. Wake-induced genes are certainly markers of neuronal activity and may also directly regulate the duration of and need for sleep. We stimulated murine cortical cultures with the neuromodulatory signals that are known to control wakefulness in the brain and found that norepinephrine alone or a mixture of these neuromodulators induced activity-regulated gene transcription. Pharmacological inhibition of the various signaling pathways involved in the regulation of gene expression indicated that the extracellular signal-regulated kinase (ERK) pathway is the principal one mediating the effects of waking neuromodulators on gene expression. In mice, ERK phosphorylation in the cortex increased and decreased with wakefulness and sleep. Whole-body or cortical neuron-specific deletion of Erk1 or Erk2 significantly increased the duration of wakefulness in mice, and pharmacological inhibition of ERK phosphorylation decreased sleep duration and increased the duration of wakefulness bouts. Thus, this signaling pathway, which is highly conserved from Drosophila to mammals, is a key pathway that links waking experience-induced neuronal gene expression to sleep duration and quality. Copyright © 2017, American Association for the Advancement of Science.

Context Fear Learning Specifically Activates Distinct Populations of Neurons in Amygdala and Hypothalamus

ERIC Educational Resources Information Center

Trogrlic, Lidia; Wilson, Yvette M.; Newman, Andrew G.; Murphy, Mark

2011-01-01

The identity and distribution of neurons that are involved in any learning or memory event is not known. In previous studies, we identified a discrete population of neurons in the lateral amygdala that show learning-specific activation of a c-"fos"-regulated transgene following context fear conditioning. Here, we have extended these studies to…

Sleep-Active Neurons: Conserved Motors of Sleep

PubMed Central

Bringmann, Henrik

2018-01-01

Sleep is crucial for survival and well-being. This behavioral and physiological state has been studied in all major genetically accessible model animals, including rodents, fish, flies, and worms. Genetic and optogenetic studies have identified several neurons that control sleep, making it now possible to compare circuit mechanisms across species. The “motor” of sleep across animal species is formed by neurons that depolarize at the onset of sleep to actively induce this state by directly inhibiting wakefulness. These sleep-inducing neurons are themselves controlled by inhibitory or activating upstream pathways, which act as the “drivers” of the sleep motor: arousal inhibits “sleep-active” neurons whereas various sleep-promoting “tiredness” pathways converge onto sleep-active neurons to depolarize them. This review provides the first overview of sleep-active neurons across the major model animals. The occurrence of sleep-active neurons and their regulation by upstream pathways in both vertebrate and invertebrate species suggests that these neurons are general and ancient components that evolved early in the history of nervous systems. PMID:29618588

Transient Receptor Potential Vanilloid Type 1–Dependent Regulation of Liver-Related Neurons in the Paraventricular Nucleus of the Hypothalamus Diminished in the Type 1 Diabetic Mouse

PubMed Central

Gao, Hong; Miyata, Kayoko; Bhaskaran, Muthu D.; Derbenev, Andrei V.; Zsombok, Andrea

2012-01-01

The paraventricular nucleus (PVN) of the hypothalamus controls the autonomic neural output to the liver, thereby participating in the regulation of hepatic glucose production (HGP); nevertheless, mechanisms controlling the activity of liver-related PVN neurons are not known. Transient receptor potential vanilloid type 1 (TRPV1) is involved in glucose homeostasis and colocalizes with liver-related PVN neurons; however, the functional role of TRPV1 regarding liver-related PVN neurons has to be elucidated. A retrograde viral tracer was used to identify liver-related neurons within the brain-liver circuit in control, type 1 diabetic, and insulin-treated mice. Our data indicate that TRPV1 regulates liver-related PVN neurons. This TRPV1-dependent excitation diminished in type 1 diabetic mice. In vivo and in vitro insulin restored TRPV1 activity in a phosphatidylinositol 3-kinase/protein kinase C–dependent manner and stimulated TRPV1 receptor trafficking to the plasma membrane. There was no difference in total TRPV1 protein expression; however, increased phosphorylation of TRPV1 receptors was observed in type 1 diabetic mice. Our data demonstrate that TRPV1 plays a pivotal role in the regulation of liver-related PVN neurons. Moreover, TRPV1-dependent excitation of liver-related PVN neurons diminishes in type 1 diabetes, thus indicating that the brain-liver autonomic circuitry is altered in type 1 diabetes and may contribute to the autonomic dysfunction of HGP. PMID:22492526

Kisspeptin: past, present, and prologue.

PubMed

Steiner, Robert A

2013-01-01

Research in the nineteenth and early twentieth century established that the brain awakens reproduction, governs reproductive activity in the adult of virtually all vertebrates. By 1950, nearly 100 years later, scientists realized that the hypothalamus and its neurosecretory products play a key role in regulating gonadal function in both males and females. Another 20 years would be required to reveal the chemical identity of GnRH and establish that neurons producing GnRH represent the final common pathway through which the brain regulates gonadotropin secretion. It had also become clear that GnRH neurons behave more like motor neurons-better perhaps at going than stopping-and are themselves regulated by a complex network of afferent inputs, which guide the tempo of sexual maturation, regulate estrous and menstrual cycles, control seasonal breeding, and stop reproduction under adversity. In 2003, the revelation that kisspeptin and its receptor are critical for reproduction opened a floodgate of research documenting the role of kisspeptin neurons as central processors of reproduction. Today, there is wide consensus that kisspeptin signaling in the brain is essential, providing the impetus to GnRH neurons to awaken at puberty and reigning the activity of these neurons when discretion is advised. We celebrate this watershed moment-with full knowledge that time and discovery will provide context and perspective to even these heady days.

TAM receptors affect adult brain neurogenesis by negative regulation of microglial cell activation.

PubMed

Ji, Rui; Tian, Shifu; Lu, Helen J; Lu, Qingjun; Zheng, Yan; Wang, Xiaomin; Ding, Jixiang; Li, Qiutang; Lu, Qingxian

2013-12-15

TAM tyrosine kinases play multiple functional roles, including regulation of the target genes important in homeostatic regulation of cytokine receptors or TLR-mediated signal transduction pathways. In this study, we show that TAM receptors affect adult hippocampal neurogenesis and loss of TAM receptors impairs hippocampal neurogenesis, largely attributed to exaggerated inflammatory responses by microglia characterized by increased MAPK and NF-κB activation and elevated production of proinflammatory cytokines that are detrimental to neuron stem cell proliferation and neuronal differentiation. Injection of LPS causes even more severe inhibition of BrdU incorporation in the Tyro3(-/-)Axl(-/-)Mertk(-/-) triple-knockout (TKO) brains, consistent with the LPS-elicited enhanced expression of proinflammatory mediators, for example, IL-1β, IL-6, TNF-α, and inducible NO synthase, and this effect is antagonized by coinjection of the anti-inflammatory drug indomethacin in wild-type but not TKO brains. Conditioned medium from TKO microglia cultures inhibits neuron stem cell proliferation and neuronal differentiation. IL-6 knockout in Axl(-/-)Mertk(-/-) double-knockout mice overcomes the inflammatory inhibition of neurogenesis, suggesting that IL-6 is a major downstream neurotoxic mediator under homeostatic regulation by TAM receptors in microglia. Additionally, autonomous trophic function of the TAM receptors on the proliferating neuronal progenitors may also promote progenitor differentiation into immature neurons.

Focal adhesion kinase regulates neuronal growth, synaptic plasticity and hippocampus-dependent spatial learning and memory.

PubMed

Monje, Francisco J; Kim, Eun-Jung; Pollak, Daniela D; Cabatic, Maureen; Li, Lin; Baston, Arthur; Lubec, Gert

2012-01-01

The focal adhesion kinase (FAK) is a non-receptor tyrosine kinase abundantly expressed in the mammalian brain and highly enriched in neuronal growth cones. Inhibitory and facilitatory activities of FAK on neuronal growth have been reported and its role in neuritic outgrowth remains controversial. Unlike other tyrosine kinases, such as the neurotrophin receptors regulating neuronal growth and plasticity, the relevance of FAK for learning and memory in vivo has not been clearly defined yet. A comprehensive study aimed at determining the role of FAK in neuronal growth, neurotransmitter release and synaptic plasticity in hippocampal neurons and in hippocampus-dependent learning and memory was therefore undertaken using the mouse model. Gain- and loss-of-function experiments indicated that FAK is a critical regulator of hippocampal cell morphology. FAK mediated neurotrophin-induced neuritic outgrowth and FAK inhibition affected both miniature excitatory postsynaptic potentials and activity-dependent hippocampal long-term potentiation prompting us to explore the possible role of FAK in spatial learning and memory in vivo. Our data indicate that FAK has a growth-promoting effect, is importantly involved in the regulation of the synaptic function and mediates in vivo hippocampus-dependent spatial learning and memory. Copyright © 2011 S. Karger AG, Basel.

Muscarinic receptors acting at pre- and post-synaptic sites differentially regulate dopamine/DARPP-32 signaling in striatonigral and striatopallidal neurons.

PubMed

Kuroiwa, Mahomi; Hamada, Miho; Hieda, Eriko; Shuto, Takahide; Sotogaku, Naoki; Flajolet, Marc; Snyder, Gretchen L; Hendrick, Joseph P; Fienberg, Allen; Nishi, Akinori

2012-12-01

Muscarinic receptors, activated by acetylcholine, play critical roles in the functional regulation of medium spiny neurons in the striatum. However, the muscarinic receptor signaling pathways are not fully elucidated due to their complexity. In this study, we investigated the function of muscarinic receptors in the striatum by monitoring DARPP-32 (dopamine- and cAMP-regulated phosphoprotein of M(r) 32 kDa) phosphorylation at Thr34 (the PKA-site) using mouse striatal slices. Treatment of slices with a non-selective muscarinic receptor agonist, oxotremorine (10 μM), rapidly and transiently increased DARPP-32 phosphorylation. The increase in DARPP-32 phosphorylation was completely abolished either by a dopamine D(1) receptor antagonist (SCH23390), tetrodotoxin, genetic deletion of M5 receptors, muscarinic toxins for M1 and M4 receptors, or 6-hydroxydopamine lesioning of dopaminergic neurons, whereas it was enhanced by nicotine. Analysis in D(1)-DARPP-32-Flag/D(2)-DARPP-32-Myc transgenic mice revealed that oxotremorine increases DARPP-32 phosphorylation selectively in D(1)-type/striatonigral, but not in D(2)-type/striatopallidal, neurons. When D(1) and D(2) receptors were blocked by selective antagonists to exclude the effects of released dopamine, oxotremorine increased DARPP-32 Thr34 phosphorylation only in D(2)-type/striatopallidal neurons. This increase required activation of M1 receptors and was dependent upon adenosine A(2A) receptor activity. The results demonstrate that muscarinic receptors, especially M5 receptors, act at presynaptic dopaminergic terminals, regulate the release of dopamine in cooperation with nicotinic receptors, and activate D(1) receptor/DARPP-32 signaling in the striatonigral neurons. Muscarinic M1 receptors expressed in striatopallidal neurons interact with adenosine A(2A) receptors and activate DARPP-32 signaling. Copyright © 2012 Elsevier Ltd. All rights reserved.

The endogenous alkaloid harmane: acidifying and activity-reducing effects on hippocampal neurons in vitro.

PubMed

Bonnet, Udo; Scherbaum, Norbert; Wiemann, Martin

2008-02-15

The endogenous alkaloid harmane is enriched in plasma of patients with neurodegenerative or addictive disorders. As harmane affects neuronal activity and viability and because both parameters are strongly influenced by intracellular pH (pH(i)), we tested whether effects of harmane are correlated with altered pH(i) regulation. Pyramidal neurons in the CA3 field of hippocampal slices were investigated under bicarbonate-buffered conditions. Harmane (50 and 100 microM) reversibly decreased spontaneous firing of action potentials and caffeine-induced bursting of CA3 neurons. In parallel experiments, 50 and 100 microM harmane evoked a neuronal acidification of 0.12+/-0.08 and 0.18+/-0.07 pH units, respectively. Recovery from intracellular acidification subsequent to an ammonium prepulse was also impaired, suggesting an inhibition of transmembrane acid extrusion by harmane. Harmane may modulate neuronal functions via altered pH(i)-regulation. Implications of these findings for neuronal survival are discussed.

Neurotrophins, growth-factor-regulated genes and the control of energy balance.

PubMed

Salton, Stephen R J

2003-03-01

Neurotrophic growth factors are proteins that control neuronal differentiation and survival, and consequently play important roles in the developing and adult stages of the nervous system. Study of the genes that are regulated by these growth factors has provided insight into the proteins that are critical to the maturation of the nervous system, suggesting that select neurotrophins may play a role in the control of body homeostasis by the brain and peripheral nervous system. Our understanding of the mechanisms of action of neurotrophic growth factors has increased through experimental manipulation of cultured neurons and neuronal cell lines. In particular, the PC12 pheochromocytoma cell line, which displays many properties of adrenal chromaffin cells and undergoes differentiation into sympathetic neuron-like cells when treated with nerve growth factor, has been extensively investigated to identify components of neurotrophin signaling pathways as well as the genes that they regulate. VGF was one of the first neurotrophin-regulated clones identified in NGF-treated PC12 cells. Subsequent studies indicate that the vgf gene is regulated in vivo in the nervous system by neurotrophins, by electrical activity, in response to injury or seizure, and by feeding and the circadian clock. The vgf gene encodes a polypeptide rich in paired basic amino acids; this polypeptide is differentially processed in neuronal and neuroendocrine cells and is released via the regulated secretory pathway. Generation and analysis of knockout mice that fail to synthesize VGF indicate that this protein plays a critical, non-redundant role in the regulation of energy homeostasis, providing a possible link between neurotrophin function in the nervous system and the peripheral control of feeding and metabolic activity. Future experiments should clarify the sites and mechanisms of action of this neurotrophin-regulated neuronal and neuroendocrine protein.

Neuronal DNA Methyltransferases: Epigenetic Mediators between Synaptic Activity and Gene Expression?

PubMed Central

Bayraktar, Gonca; Kreutz, Michael R.

2017-01-01

DNMT3A and 3B are the main de novo DNA methyltransferases (DNMTs) in the brain that introduce new methylation marks to non-methylated DNA in postmitotic neurons. DNA methylation is a key epigenetic mark that is known to regulate important cellular processes in neuronal development and brain plasticity. Accumulating evidence disclosed rapid and dynamic changes in DNA methylation of plasticity-relevant genes that are important for learning and memory formation. To understand how DNMTs contribute to brain function and how they are regulated by neuronal activity is a prerequisite for a deeper appreciation of activity-dependent gene expression in health and disease. This review discusses the functional role of de novo methyltransferases and in particular DNMT3A1 in the adult brain with special emphasis on synaptic plasticity, memory formation, and brain disorders. PMID:28513272

Regulated expression of the Ras effector Rin1 in forebrain neurons

PubMed Central

Dzudzor, Bartholomew; Huynh, Lucia; Thai, Minh; Bliss, Joanne M.; Nagaoka, Yoshiko; Wang, Ying; Ch'ng, Toh Hean; Jiang, Meisheng; Martin, Kelsey C.; Colicelli, John

2009-01-01

The Ras effector Rin1 is induced concomitant with synaptogenesis in forebrain neurons, where it inhibits fear conditioning and amygdala LTP. In epithelial cells, lower levels of Rin1 orchestrate receptor endocytosis. A 945bp Rin1 promoter fragment was active in hippocampal neurons and directed accurate tissue-specific and temporal expression in transgenic mice. Regulated expression in neurons and epithelial cells was mediated in part by Snail transcriptional repressors: mutation of a conserved Snail site increased expression and endogenous Snai1 was detected at the Rin1 promoter. We also describe an element closely related to, but distinct from, the consensus site for REST, a master repressor of neuronal genes. Conversion to a consensus REST sequence reduced expression in both cell types. These results provide insight into regulated expression of a neuronal Ras effector, define a promoter useful in telencephalic neuron studies, and describe a novel REST site variant directing expression to mature neurons. PMID:19837165

Neuronal activity in ontogeny and oncology

PubMed Central

Venkatesh, Humsa; Monje, Michelle

2017-01-01

The nervous system plays a central role in regulating the stem cell niche in many organs and thereby critically modulates development, homeostasis and plasticity. A similarly powerful role for neural regulation of the cancer microenvironment is emerging. Neurons promote the growth of cancers of the brain, skin, prostate, pancreas and stomach. Parallel mechanisms shared in development and cancer suggest that neural modulation of the tumor microenvironment may prove a universal theme, although the mechanistic details of such modulation remain to be discovered for many malignancies. Here, we review what is known about the influences of active neurons on stem cell and cancer microenvironments across a broad range of tissues and discuss emerging principles of neural regulation of development and cancer. PMID:28718448

Transcriptional coupling of synaptic transmission and energy metabolism: role of nuclear respiratory factor 1 in co-regulating neuronal nitric oxide synthase and cytochrome c oxidase genes in neurons.

PubMed

Dhar, Shilpa S; Liang, Huan Ling; Wong-Riley, Margaret T T

2009-10-01

Neuronal activity is highly dependent on energy metabolism; yet, the two processes have traditionally been regarded as independently regulated at the transcriptional level. Recently, we found that the same transcription factor, nuclear respiratory factor 1 (NRF-1) co-regulates an important energy-generating enzyme, cytochrome c oxidase, as well as critical subunits of glutamatergic receptors. The present study tests our hypothesis that the co-regulation extends to the next level of glutamatergic synapses, namely, neuronal nitric oxide synthase, which generates nitric oxide as a downstream signaling molecule. Using in silico analysis, electrophoretic mobility shift assay, chromatin immunoprecipitation, promoter mutations, and NRF-1 silencing, we documented that NRF-1 functionally bound to Nos1, but not Nos2 (inducible) and Nos3 (endothelial) gene promoters. Both COX and Nos1 transcripts were up-regulated by depolarizing KCl treatment and down-regulated by TTX-mediated impulse blockade in neurons. However, NRF-1 silencing blocked the up-regulation of both Nos1 and COX induced by KCl depolarization, and over-expression of NRF-1 rescued both Nos1 and COX transcripts down-regulated by TTX. These findings are consistent with our hypothesis that synaptic neuronal transmission and energy metabolism are tightly coupled at the molecular level.

Insulin/IGF1 Signaling Inhibits Age-Dependent Axon Regeneration

PubMed Central

Byrne, Alexandra B.; Walradt, Trent; Gardner, Kathryn E.; Hubbert, Austin; Reinke, Valerie; Hammarlund, Marc

2014-01-01

Summary The ability of injured axons to regenerate declines with age yet the mechanisms that regulate axon regeneration in response to age are not known. Here we show that axon regeneration in aging C. elegans motor neurons is inhibited by the conserved insulin/IGF1 receptor DAF-2. DAF-2’s function in regeneration is mediated by intrinsic neuronal activity of the forkhead transcription factor DAF-16/FOXO. DAF-16 regulates regeneration independently of lifespan, indicating that neuronal aging is an intrinsic, neuron specific, and genetically regulated process. In addition, we found that daf-18/PTEN inhibits regeneration independently of age and FOXO signaling, via the TOR pathway. Finally, DLK-1, a conserved regulator of regeneration, is downregulated by insulin/IGF1 signaling, bound by DAF-16 in neurons, and is required for both DAF-16- and DAF-18-mediated regeneration. Together, our data establish that insulin signaling specifically inhibits regeneration in aging adult neurons, and that this mechanism is independent of PTEN and TOR. PMID:24440228

Mitochondria-targeted molecules MitoQ and SS31 reduce mutant huntingtin-induced mitochondrial toxicity and synaptic damage in Huntington's disease

PubMed Central

Yin, Xiangling; Manczak, Maria; Reddy, P. Hemachandra

2016-01-01

The objective of this study was to determine the protective effects of the mitochondria-targeted molecules MitoQ and SS31 in striatal neurons that stably express mutant huntingtin (Htt) (STHDhQ111/Q111) in Huntington's disease (HD). We studied mitochondrial and synaptic activities by measuring mRNA and the protein levels of mitochondrial and synaptic genes, mitochondrial function, and ultra-structural changes in MitoQ- and SS31-treated mutant Htt neurons relative to untreated mutant Htt neurons. We used gene expression analysis, biochemical methods, transmission electron microscopy (TEM) and confocal microscopy methods. In the MitoQ- and SS31-treated mutant Htt neurons, fission genes Drp1 and Fis1 were down-regulated, and fusion genes Mfn1, Mfn2 and Opa1 were up-regulated relative to untreated neurons, suggesting that mitochondria-targeted molecules reduce fission activity. Interestingly, the mitochondrial biogenesis genes PGC1α, PGC1β, Nrf1, Nrf2 and TFAM were up-regulated in MitoQ- and SS31-treated mutant Htt neurons. The synaptic genes synaptophysin and PSD95 were up-regulated, and mitochondrial function was normal in the MitoQ- and SS31-treated mutant Htt neurons. Immunoblotting findings of mitochondrial and synaptic proteins agreed with the mRNA findings. TEM studies revealed decreased numbers of structurally intact mitochondria in MitoQ- and SS31-treated mutant Htt neurons. These findings suggest that mitochondria-targeted molecules MitoQ and SS31 are protective against mutant Htt-induced mitochondrial and synaptic damage in HD neurons, and these mitochondria-targeted molecules are potential therapeutic molecules for the treatment of HD neurons. PMID:26908605

Mitochondria-targeted molecules MitoQ and SS31 reduce mutant huntingtin-induced mitochondrial toxicity and synaptic damage in Huntington's disease.

PubMed

Yin, Xiangling; Manczak, Maria; Reddy, P Hemachandra

2016-05-01

The objective of this study was to determine the protective effects of the mitochondria-targeted molecules MitoQ and SS31 in striatal neurons that stably express mutant huntingtin (Htt) (STHDhQ111/Q111) in Huntington's disease (HD). We studied mitochondrial and synaptic activities by measuring mRNA and the protein levels of mitochondrial and synaptic genes, mitochondrial function, and ultra-structural changes in MitoQ- and SS31-treated mutant Htt neurons relative to untreated mutant Htt neurons. We used gene expression analysis, biochemical methods, transmission electron microscopy (TEM) and confocal microscopy methods. In the MitoQ- and SS31-treated mutant Htt neurons, fission genes Drp1 and Fis1 were down-regulated, and fusion genes Mfn1, Mfn2 and Opa1 were up-regulated relative to untreated neurons, suggesting that mitochondria-targeted molecules reduce fission activity. Interestingly, the mitochondrial biogenesis genes PGC1α, PGC1β, Nrf1, Nrf2 and TFAM were up-regulated in MitoQ- and SS31-treated mutant Htt neurons. The synaptic genes synaptophysin and PSD95 were up-regulated, and mitochondrial function was normal in the MitoQ- and SS31-treated mutant Htt neurons. Immunoblotting findings of mitochondrial and synaptic proteins agreed with the mRNA findings. TEM studies revealed decreased numbers of structurally intact mitochondria in MitoQ- and SS31-treated mutant Htt neurons. These findings suggest that mitochondria-targeted molecules MitoQ and SS31 are protective against mutant Htt-induced mitochondrial and synaptic damage in HD neurons, and these mitochondria-targeted molecules are potential therapeutic molecules for the treatment of HD neurons. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Regulating the dorsal neural tube expression of Ptf1a through a distal 3' enhancer.

PubMed

Mona, Bishakha; Avila, John M; Meredith, David M; Kollipara, Rahul K; Johnson, Jane E

2016-10-01

Generating the correct balance of inhibitory and excitatory neurons in a neural network is essential for normal functioning of a nervous system. The neural network in the dorsal spinal cord functions in somatosensation where it modulates and relays sensory information from the periphery. PTF1A is a key transcriptional regulator present in a specific subset of neural progenitor cells in the dorsal spinal cord, cerebellum and retina that functions to specify an inhibitory neuronal fate while suppressing excitatory neuronal fates. Thus, the regulation of Ptf1a expression is critical for determining mechanisms controlling neuronal diversity in these regions of the nervous system. Here we identify a sequence conserved, tissue-specific enhancer located 10.8kb 3' of the Ptf1a coding region that is sufficient to direct expression to dorsal neural tube progenitors that give rise to neurons in the dorsal spinal cord in chick and mouse. DNA binding motifs for Paired homeodomain (Pd-HD) and zinc finger (ZF) transcription factors are required for enhancer activity. Mutations in these sequences implicate the Pd-HD motif for activator function and the ZF motif for repressor function. Although no repressor transcription factor was identified, both PAX6 and SOX3 can increase enhancer activity in reporter assays. Thus, Ptf1a is regulated by active and repressive inputs integrated through multiple sequence elements within a highly conserved sequence downstream of the Ptf1a gene. Copyright © 2016 Elsevier Inc. All rights reserved.

Developmental Responses of the Lateral Hypothalamus to Leptin in Neonatal Rats, and its Implications for the Development of Functional Connections with the Ventral Tegmental Area.

PubMed

Gjerde, E; Long, H; Richard, D; Walker, C-D

2016-03-01

Food intake is regulated by a close communication between the hypothalamus and the mesocorticolimbic pathways, which are still developing during the perinatal period in the rat, and are known targets for peripheral metabolic hormones such as leptin. A key region for this communication is the lateral hypothalamus (LH), although the onset of leptin responsiveness in the LH is unknown. We examined the activation of cellular signalling molecules in identified LH neurones on postnatal day (PND)10 and 16 and determined whether leptin directly targets orexin A (ORX-A) or neurotensin (NT) LH neurones through the detection of leptin receptors (ObRb) mRNA on these neurones. Next, using retrograde labelling in PND6 pups, we tested whether phenotypically identified neurones of the LH that respond to leptin project to ventral tegmental area (VTA) neurones. Leptin significantly induced phosphorylated extracellular signal-regulated kinase (pERK)1/2 and phosphorylated signal transducer activator of transcription (pSTAT)3 in the LH on PND16, whereas, on PND10, modest pERK1/2- and sparse pSTAT3-positive cells were identified. On PND16, most pERK1/2-activated neurones contain ORX-A and leptin-induced pSTAT3 was observed in other unidentified neurones. Afferents to the VTA were observed on PND6, including a large input from the LH, which contained both ORX-A-positive and non-ORX-A neurones, with some of these ORX-A neurones being activated by leptin treatment. Leptin receptor (ObRb) mRNA in the LH did not colocalise with ORX-A neurones on PND10, and only a few NT-positive neurones displayed ObRb mRNA expression. Thus, functional responsiveness to leptin in LH neurones is only partially achieved prior to the onset of independent feeding on PND16, and ORX-A neurones are indirectly activated by leptin. The presence of anatomical connections between the LH and the VTA in the first week of life, prior to the development of leptin responsiveness in both structures, suggests that tissue responsiveness to leptin, rather than the maturation of neuronal connections, critically regulates the onset of independent feeding. © 2015 British Society for Neuroendocrinology.

Na-coupled bicarbonate transporters of the Slc4 family in the nervous system: function, localization, and relevance to neurologic function

PubMed Central

Majumdar, Debeshi; Bevensee, Mark O.

2010-01-01

Many cellular processes including neuronal activity are sensitive to changes in intracellular and/or extracellular pH— both of which are regulated by acid-base transporter activity. HCO3−-dependent transporters are particularly potent regulators of intracellular pH in neurons and astrocytes, and also contribute to the composition of the cerebrospinal fluid (CSF). The molecular physiology of HCO3− transporters has advanced considerably over the past ~14 years as investigators have cloned and characterized the function and localization of many Na-Coupled Bicarbonate Transporters of the Slc4 family (NCBTs). In this review, we provide an updated overview of the function and localization of NCBTs in the nervous system. Multiple NCBTs are expressed in neurons and astrocytes in various brain regions, as well as in epithelial cells of the choroid plexus. Characteristics of human patients with SLC4 gene mutations/deletions and results from recent studies on mice with Slc4 gene disruptions highlight the functional importance of NCBTs in neuronal activity, somatosensory function, and CSF production. Furthermore, energy-deficient states (e.g., hypoxia and ischemia) lead to altered expression and activity of NCBTs. Thus, recent studies expand our understanding of the role of NCBTs in regulating the pH and ionic composition of the nervous system that can modulate neuronal activity. PMID:20884330

Computational modeling of epidural cortical stimulation

NASA Astrophysics Data System (ADS)

Wongsarnpigoon, Amorn; Grill, Warren M.

2008-12-01

Epidural cortical stimulation (ECS) is a developing therapy to treat neurological disorders. However, it is not clear how the cortical anatomy or the polarity and position of the electrode affects current flow and neural activation in the cortex. We developed a 3D computational model simulating ECS over the precentral gyrus. With the electrode placed directly above the gyrus, about half of the stimulus current flowed through the crown of the gyrus while current density was low along the banks deep in the sulci. Beneath the electrode, neurons oriented perpendicular to the cortical surface were depolarized by anodic stimulation, and neurons oriented parallel to the boundary were depolarized by cathodic stimulation. Activation was localized to the crown of the gyrus, and neurons on the banks deep in the sulci were not polarized. During regulated voltage stimulation, the magnitude of the activating function was inversely proportional to the thickness of the CSF and dura. During regulated current stimulation, the activating function was not sensitive to the thickness of the dura but was slightly more sensitive than during regulated voltage stimulation to the thickness of the CSF. Varying the width of the gyrus and the position of the electrode altered the distribution of the activating function due to changes in the orientation of the neurons beneath the electrode. Bipolar stimulation, although often used in clinical practice, reduced spatial selectivity as well as selectivity for neuron orientation.

IMPACT Is a Developmentally Regulated Protein in Neurons That Opposes the Eukaryotic Initiation Factor 2α Kinase GCN2 in the modulation of Neurite Outgrowth*

PubMed Central

Roffé, Martín; Hajj, Glaucia N. M.; Azevedo, Hátylas F.; Alves, Viviane S.; Castilho, Beatriz A.

2013-01-01

The product of the mouse Imprinted and Ancient gene, IMPACT, is preferentially expressed in neurons. We have previously shown that IMPACT overexpression inhibits the activation of the protein kinase GCN2, which signals amino acid starvation. GCN2 phosphorylates the α-subunit of eukaryotic translation initiation factor 2 (eIF2α), resulting in inhibition of general protein synthesis but increased translation of specific messages, such as ATF4. GCN2 is also involved in the regulation of neuronal functions, controlling synaptic plasticity, memory, and feeding behavior. We show here that IMPACT abundance increases during differentiation of neurons and neuron-like N2a cells, whereas GCN2 displays lowered activation levels. Upon differentiation, IMPACT associates with translating ribosomes, enhances translation initiation, and down-regulates the expression of ATF4. We further show that endogenous IMPACT promotes neurite outgrowth whereas GCN2 is a strong inhibitor of spontaneous neuritogenesis. Together, these results uncover the participation of the GCN2-IMPACT module of translational regulation in a highly controlled step in the development of the nervous system. PMID:23447528

IMPACT is a developmentally regulated protein in neurons that opposes the eukaryotic initiation factor 2α kinase GCN2 in the modulation of neurite outgrowth.

PubMed

Roffé, Martín; Hajj, Glaucia N M; Azevedo, Hátylas F; Alves, Viviane S; Castilho, Beatriz A

2013-04-12

The product of the mouse Imprinted and Ancient gene, IMPACT, is preferentially expressed in neurons. We have previously shown that IMPACT overexpression inhibits the activation of the protein kinase GCN2, which signals amino acid starvation. GCN2 phosphorylates the α-subunit of eukaryotic translation initiation factor 2 (eIF2α), resulting in inhibition of general protein synthesis but increased translation of specific messages, such as ATF4. GCN2 is also involved in the regulation of neuronal functions, controlling synaptic plasticity, memory, and feeding behavior. We show here that IMPACT abundance increases during differentiation of neurons and neuron-like N2a cells, whereas GCN2 displays lowered activation levels. Upon differentiation, IMPACT associates with translating ribosomes, enhances translation initiation, and down-regulates the expression of ATF4. We further show that endogenous IMPACT promotes neurite outgrowth whereas GCN2 is a strong inhibitor of spontaneous neuritogenesis. Together, these results uncover the participation of the GCN2-IMPACT module of translational regulation in a highly controlled step in the development of the nervous system.

Synaptic organization of the Drosophila antennal lobe and its regulation by the Teneurins

PubMed Central

Mosca, Timothy J; Luo, Liqun

2014-01-01

Understanding information flow through neuronal circuits requires knowledge of their synaptic organization. In this study, we utilized fluorescent pre- and postsynaptic markers to map synaptic organization in the Drosophila antennal lobe, the first olfactory processing center. Olfactory receptor neurons (ORNs) produce a constant synaptic density across different glomeruli. Each ORN within a class contributes nearly identical active zone number. Active zones from ORNs, projection neurons (PNs), and local interneurons have distinct subglomerular and subcellular distributions. The correct number of ORN active zones and PN acetylcholine receptor clusters requires the Teneurins, conserved transmembrane proteins involved in neuromuscular synapse organization and synaptic partner matching. Ten-a acts in ORNs to organize presynaptic active zones via the spectrin cytoskeleton. Ten-m acts in PNs autonomously to regulate acetylcholine receptor cluster number and transsynaptically to regulate ORN active zone number. These studies advanced our ability to assess synaptic architecture in complex CNS circuits and their underlying molecular mechanisms. DOI: http://dx.doi.org/10.7554/eLife.03726.001 PMID:25310239

Estrogen receptor-a in medial amygdala neurons regulates body weight

USDA-ARS?s Scientific Manuscript database

Estrogen receptor–a (ERa) activity in the brain prevents obesity in both males and females. However, the ERa-expressing neural populations that regulate body weight remain to be fully elucidated. Here we showed that single-minded–1 (SIM1) neurons in the medial amygdala (MeA) express abundant levels ...

Localized Disruption of Narp in Medial Prefrontal Cortex Blocks Reinforcer Devaluation Performance

ERIC Educational Resources Information Center

Johnson, Alexander W.; Han, Sungho; Blouin, Ashley M.; Saini, Jasjit; Worley, Paul F.; During, Matthew J.; Holland, Peter C.; Baraban, Jay M.; Reti, Irving M.

2010-01-01

Neuronal activity regulated pentraxin (Narp) is a secreted protein that regulates [alpha]-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate receptors (AMPAR) aggregation and synaptogenesis. Mapping of Narp-positive neurons in brain has revealed it is prominently expressed in several limbic system projection pathways. Consistent with this…

Royal Jelly Reduces Cholesterol Levels, Ameliorates Aβ Pathology and Enhances Neuronal Metabolic Activities in a Rabbit Model of Alzheimer’s Disease

PubMed Central

Pan, Yongming; Xu, Jianqin; Chen, Cheng; Chen, Fangming; Jin, Ping; Zhu, Keyan; Hu, Chenyue W.; You, Mengmeng; Chen, Minli; Hu, Fuliang

2018-01-01

Alzheimer’s disease (AD) is the most common form of dementia characterized by aggregation of amyloid β (Aβ) and neuronal loss. One of the risk factors for AD is high cholesterol levels, which are known to promote Aβ deposition. Previous studies have shown that royal jelly (RJ), a product of worker bees, has potential neuroprotective effects and can attenuate Aβ toxicity. However, little is known about how RJ regulates Aβ formation and its effects on cholesterol levels and neuronal metabolic activities. Here, we investigated whether RJ can reduce cholesterol levels, regulate Aβ levels and enhance neuronal metabolic activities in an AD rabbit model induced by 2% cholesterol diet plus copper drinking water. Our results suggest that RJ significantly reduced the levels of plasma total cholesterol (TC) and low density lipoprotein-cholesterol (LDL-C), and decreased the level of Aβ in rabbit brains. RJ was also shown to markedly ameliorate amyloid deposition in AD rabbits from Aβ immunohistochemistry and thioflavin-T staining. Furthermore, our study suggests that RJ can reduce the expression levels of β-site APP cleaving enzyme-1 (BACE1) and receptor for advanced glycation end products (RAGE), and increase the expression levels of low density lipoprotein receptor-related protein 1 (LRP-1) and insulin degrading enzyme (IDE). In addition, we found that RJ remarkably increased the number of neurons, enhanced antioxidant capacities, inhibited activated-capase-3 protein expression, and enhanced neuronal metabolic activities by increasing N-acetyl aspartate (NAA) and glutamate and by reducing choline and myo-inositol in AD rabbits. Taken together, our data demonstrated that RJ could reduce cholesterol levels, regulate Aβ levels and enhance neuronal metabolic activities in AD rabbits, providing preclinical evidence that RJ treatment has the potential to protect neurons and prevent AD. PMID:29556189

Reciprocal signals between microglia and neurons regulate α-synuclein secretion by exophagy through a neuronal cJUN-N-terminal kinase-signaling axis.

PubMed

Christensen, Dan Ploug; Ejlerskov, Patrick; Rasmussen, Izabela; Vilhardt, Frederik

2016-03-08

Secretion of proteopathic α-synuclein (α-SNC) species from neurons is a suspected driving force in the propagation of Parkinson's disease (PD). We have previously implicated exophagy, the exocytosis of autophagosomes, as a dominant mechanism of α-SNC secretion in differentiated PC12 or SH-SY5Y nerve cells. Here we have examined the regulation of exophagy associated with different forms of nerve cell stress relevant to PD. We identify cJUN-N-terminal kinase (JNK) activity as pivotal in the secretory fate of autophagosomes containing α-SNC. Pharmacological inhibition or genetic (shRNA) knockdown of JNK2 or JNK3 decreases α-SNC secretion in differentiated PC12 and SH-SY5Y cells, respectively. Conversely, expression of constitutively active mitogen-activated protein kinase kinase 7 (MKK7)-JNK2 and -JNK3 constructs augment secretion. The transcriptional activity of cJUN was not required for the observed effects. We establish a causal relationship between increased α-SNC release by exophagy and JNK activation subsequent to lysosomal fusion deficiency (overexpression of Lewy body-localized protein p25α or bafilomycin A1). JNK activation following neuronal ER or oxidative stress was not correlated with exophagy, but of note, we demonstrate that reciprocal signaling between microglia and neurons modulates α-SNC secretion. NADPH oxidase activity of microglia cell lines was upregulated by direct co-culture with α-SNC-expressing PC12 neurons or by passive transfer of nerve cell-conditioned medium. Conversely, inflammatory factors secreted from activated microglia increased JNK activation and α-SNC secretion several-fold in PC12 cells. While we do not identify these factors, we extend our observations by showing that exposure of neurons in monoculture to TNFα, a classical pro-inflammatory mediator of activated microglia, is sufficient to increase α-SNC secretion in a mechanism dependent on JNK2 or JNK3. In continuation hereof, we show that also IFNβ and TGFβ increase the release of α-SNC from PC12 neurons. We implicate stress kinases of the JNK family in the regulation of exophagy and release of α-SNC following endogenous or exogenous stimulation. In a wider scope, our results imply that microglia not only inflict bystander damage to neurons in late phases of inflammatory brain disease but may also be active mediators of disease propagation.

Pharmacological characterization of ionic currents that regulate high-frequency spontaneous activity of electromotor neurons in the weakly electric fish, Apteronotus leptorhynchus.

PubMed

Smith, G Troy

2006-01-01

The neural circuit that controls the electric organ discharge (EOD) of the brown ghost knifefish (Apteronotus leptorhynchus) contains two spontaneous oscillators. Both pacemaker neurons in the medulla and electromotor neurons (EMNs) in the spinal cord fire spontaneously at frequencies of 500-1,000 Hz to control the EOD. These neurons continue to fire in vitro at frequencies that are highly correlated with in vivo EOD frequency. Previous studies used channel blocking drugs to pharmacologically characterize ionic currents that control high-frequency firing in pacemaker neurons. The goal of the present study was to use similar techniques to investigate ionic currents in EMNs, the other type of spontaneously active neuron in the electromotor circuit. As in pacemaker neurons, high-frequency firing of EMNs was regulated primarily by tetrodotoxin-sensitive sodium currents and by potassium currents that were sensitive to 4-aminopyridine and kappaA-conotoxin SIVA, but resistant to tetraethylammonium. EMNs, however, differed from pacemaker neurons in their sensitivity to some channel blocking drugs. Alpha-dendrotoxin, which blocks a subset of Kv1 potassium channels, increased firing rates in EMNs, but not pacemaker neurons; and the sodium channel blocker muO-conotoxin MrVIA, which reduced firing rates of pacemaker neurons, had no effect on EMNs. These results suggest that similar, but not identical, ionic currents regulate high-frequency firing in EMNs and pacemaker neurons. The differences in the ionic currents expressed in pacemaker neurons and EMNs might be related to differences in the morphology, connectivity, or function of these two cell types.

Clique of Functional Hubs Orchestrates Population Bursts in Developmentally Regulated Neural Networks

PubMed Central

Luccioli, Stefano; Ben-Jacob, Eshel; Barzilai, Ari; Bonifazi, Paolo; Torcini, Alessandro

2014-01-01

It has recently been discovered that single neuron stimulation can impact network dynamics in immature and adult neuronal circuits. Here we report a novel mechanism which can explain in neuronal circuits, at an early stage of development, the peculiar role played by a few specific neurons in promoting/arresting the population activity. For this purpose, we consider a standard neuronal network model, with short-term synaptic plasticity, whose population activity is characterized by bursting behavior. The addition of developmentally inspired constraints and correlations in the distribution of the neuronal connectivities and excitabilities leads to the emergence of functional hub neurons, whose stimulation/deletion is critical for the network activity. Functional hubs form a clique, where a precise sequential activation of the neurons is essential to ignite collective events without any need for a specific topological architecture. Unsupervised time-lagged firings of supra-threshold cells, in connection with coordinated entrainments of near-threshold neurons, are the key ingredients to orchestrate population activity. PMID:25255443

Protease-Activated Receptor 2 Activation Inhibits N-Type Ca2+ Currents in Rat Peripheral Sympathetic Neurons

PubMed Central

Kim, Young-Hwan; Ahn, Duck-Sun; Kim, Myeong Ok; Joeng, Ji-Hyun; Chung, Seungsoo

2014-01-01

The protease-activated receptor (PAR)-2 is highly expressed in endothelial cells and vascular smooth muscle cells. It plays a crucial role in regulating blood pressure via the modulation of peripheral vascular tone. Although several mechanisms have been suggested to explain PAR-2-induced hypotension, the precise mechanism remains to be elucidated. To investigate this possibility, we investigated the effects of PAR-2 activation on N-type Ca2+ currents (ICa-N) in isolated neurons of the celiac ganglion (CG), which is involved in the sympathetic regulation of mesenteric artery vascular tone. PAR-2 agonists irreversibly diminished voltage-gated Ca2+ currents (ICa), measured using the patch-clamp method, in rat CG neurons, whereas thrombin had little effect on ICa. This PAR-2-induced inhibition was almost completely prevented by ω-CgTx, a potent N-type Ca2+ channel blocker, suggesting the involvement of N-type Ca2+ channels in PAR-2-induced inhibition. In addition, PAR-2 agonists inhibited ICa–N in a voltage-independent manner in rat CG neurons. Moreover, PAR-2 agonists reduced action potential (AP) firing frequency as measured using the current-clamp method in rat CG neurons. This inhibition of AP firing induced by PAR-2 agonists was almost completely prevented by ω-CgTx, indicating that PAR-2 activation may regulate the membrane excitability of peripheral sympathetic neurons through modulation of N-type Ca2+ channels. In conclusion, the present findings demonstrate that the activation of PAR-2 suppresses peripheral sympathetic outflow by modulating N-type Ca2+ channel activity, which appears to be involved in PAR-2-induced hypotension, in peripheral sympathetic nerve terminals. PMID:25410909

Central serotonergic neurons activate and recruit thermogenic brown and beige fat and regulate glucose and lipid homeostasis.

PubMed

McGlashon, Jacob M; Gorecki, Michelle C; Kozlowski, Amanda E; Thirnbeck, Caitlin K; Markan, Kathleen R; Leslie, Kirstie L; Kotas, Maya E; Potthoff, Matthew J; Richerson, George B; Gillum, Matthew P

2015-05-05

Thermogenic brown and beige adipocytes convert chemical energy to heat by metabolizing glucose and lipids. Serotonin (5-HT) neurons in the CNS are essential for thermoregulation and accordingly may control metabolic activity of thermogenic fat. To test this, we generated mice in which the human diphtheria toxin receptor (DTR) was selectively expressed in central 5-HT neurons. Treatment with diphtheria toxin (DT) eliminated 5-HT neurons and caused loss of thermoregulation, brown adipose tissue (BAT) steatosis, and a >50% decrease in uncoupling protein 1 (Ucp1) expression in BAT and inguinal white adipose tissue (WAT). In parallel, blood glucose increased 3.5-fold, free fatty acids 13.4-fold, and triglycerides 6.5-fold. Similar BAT and beige fat defects occurred in Lmx1b(f/f)ePet1(Cre) mice in which 5-HT neurons fail to develop in utero. We conclude 5-HT neurons play a major role in regulating glucose and lipid homeostasis, in part through recruitment and metabolic activation of brown and beige adipocytes. Copyright © 2015 Elsevier Inc. All rights reserved.

Developmental Activation of the Proteolipid Protein Promoter Transgene in Neuronal and Oligodendroglial Cells of Neostriatum in Mice

PubMed Central

Fulton, Daniel; Paez, Pablo; Spreur, Vilma; Handley, Vance; Colwell, Christopher S.; Campagnoni, Anthony; Fisher, Robin

2011-01-01

Prior studies suggest that non-canonical proteolipid protein (PLP) gene expression occurs during development in non-myelinating neurons as well as myelinating oligodendroglia in mammalian brain. To assess this possibility in neostriatum, a region of uncertain PLP gene expression in neurons, morphological and electrophysiological tools were used to determine phenotypes of cells with activation of a PLP promoter transgene during the early postnatal period in mice. PLP gene expression is evident in both neuronal and oligodendroglial phenotypes in developing neostriatum, a conclusion based on three novel observations: (1) An enhanced green fluorescent protein (EGFP) reporter of PLP promoter activation was localized in two distinct populations of cells, which exhibit collective, developmental differences of morphological and electrophysiological characteristics in accord with neuronal and oligodendroglial phenotypes of neostriatal cells found during the early postnatal period in both transgenic and wild-type mice. (2) The EGFP reporter of PLP promoter activation was appropriately positioned to serve as a regulator of PLP gene expression. It colocalized with native PLP proteins in both neuronal and oligodendroglial phenotypes; however, only soma-restricted PLP protein isoforms were found in the neuronal phenotype, while classic and soma-restricted PLP protein isoforms were found in the oligodendroglial phenotype. (3) As shown by EGFP reporter, PLP promoter activation was placed to regulate PLP gene expression in only one neuronal phenotype among the several that constitute neostriatum. It was localized in medium spiny neurons, but not large aspiny neurons. These outcomes have significant implications for the non-canonical functional roles of PLP gene expression in addition to myelinogenesis in mammalian brain, and are consistent with potentially independent pathologic loci in neurons during the course of human mutational disorders of PLP gene expression. PMID:21912090

Administration of IL-1beta to the 4th ventricle causes anorexia that is blocked by agouti-related peptide and that coincides with activation of tyrosine-hydroxylase neurons in the nucleus of the solitary tract.

PubMed

DeBoer, Mark D; Scarlett, Jarrad M; Levasseur, Peter R; Grant, Wilmon F; Marks, Daniel L

2009-02-01

Inflammation-associated cachexia is associated with multiple chronic diseases and involves activation of appetite regulating centers in the arcuate nucleus of the hypothalamus (ARH). The nucleus of the solitary tract (NTS) in the brainstem has also been implicated as an important nucleus involved in appetite regulation. We set out to determine whether the NTS may be involved in inflammation-associated anorexia by injecting IL-1 beta into the 4th ventricle and assessing food intake and NTS neuronal activation. Injection of IL-1 beta produced a decrease in food intake at 3 and 12h after injection which was ameliorated at the 12h time point by a sub-threshold dose of agouti-related peptide (AgRP). Investigation into neuron types in the NTS revealed that IL-1 beta injection was associated with an increase in c-Fos activity in NTS neurons expressing tyrosine hydroxylase (TH). Additionally, injection of IL-1 beta into the 4th ventricle did not produce c-Fos activation of neurons expressing pro-opiomelanocortin (POMC) in the ARH, cells known to be involved in producing anorexia in response to systemic inflammation. Double-label in situ hybridization revealed that TH neurons did not express IL-1 receptor I (IL1-RI) transcript, demonstrating that c-Fos activation of TH neurons in this setting was not via direct stimulation of IL-1 beta on TH neurons themselves. We conclude that IL-1 beta injection into the 4th ventricle produces anorexia and is accompanied by an increase in activation in TH neurons in the NTS. This provides evidence that the brainstem may be an important mediator of anorexia in the setting of inflammation.

A leptin-regulated circuit controls glucose mobilization during noxious stimuli.

PubMed

Flak, Jonathan N; Arble, Deanna; Pan, Warren; Patterson, Christa; Lanigan, Thomas; Goforth, Paulette B; Sacksner, Jamie; Joosten, Maja; Morgan, Donald A; Allison, Margaret B; Hayes, John; Feldman, Eva; Seeley, Randy J; Olson, David P; Rahmouni, Kamal; Myers, Martin G

2017-08-01

Adipocytes secrete the hormone leptin to signal the sufficiency of energy stores. Reductions in circulating leptin concentrations reflect a negative energy balance, which augments sympathetic nervous system (SNS) activation in response to metabolically demanding emergencies. This process ensures adequate glucose mobilization despite low energy stores. We report that leptin receptor-expressing neurons (LepRb neurons) in the periaqueductal gray (PAG), the largest population of LepRb neurons in the brain stem, mediate this process. Application of noxious stimuli, which often signal the need to mobilize glucose to support an appropriate response, activated PAG LepRb neurons, which project to and activate parabrachial nucleus (PBN) neurons that control SNS activation and glucose mobilization. Furthermore, activating PAG LepRb neurons increased SNS activity and blood glucose concentrations, while ablating LepRb in PAG neurons augmented glucose mobilization in response to noxious stimuli. Thus, decreased leptin action on PAG LepRb neurons augments the autonomic response to noxious stimuli, ensuring sufficient glucose mobilization during periods of acute demand in the face of diminished energy stores.

Regulation Of Hypothalamic Signaling By Tuberoinfundibular Peptide Of 39 Residues Is Critical For The Response To Cold: A Novel Peptidergic Mechanism Of Thermoregulation

PubMed Central

Dimitrov, Eugene L.; Kim, Yoon Yi; Usdin, Ted B.

2012-01-01

Euthermia is critical for mammalian homeostasis. Circuits within the preoptic hypothalamus regulate temperature, with fine control exerted via descending GABAergic inhibition of presympathetic motor neurons that control brown adipose tissue (BAT) thermogenesis and cutaneous vascular tone. The thermoregulatory role of hypothalamic excitatory neurons is less clear. Here we report peptidergic regulation of preoptic glutamatergic neurons that contributes to temperature regulation. Tuberoinfundibular peptide of 39 residues (TIP39) is a ligand for the parathyroid hormone 2 receptor (PTH2R). Both peptide and receptor are abundant in the preoptic hypothalamus. Based on PTH2R and vesicular glutamate transporter 2 (VGlut2) immunolabeling in animals with retrograde tracer injection, PTH2R containing glutamatergic fibers are presynaptic to neurons projecting from the median preoptic nucleus (MnPO) to the dorsomedial hypothalamus. Transneuronal retrograde pathway tracing with pseudorabies virus revealed connectivity between MnPO VGlut2 and PTH2R neurons and BAT. MnPO injection of TIP39 increased body temperature by 2° C for several hours. Mice lacking TIP39 signaling, either because of PTH2R null mutation or brain delivery of a PTH2R antagonist had impaired heat production upon cold exposure, but no change in basal temperature and no impairment in response to a hot environment. Thus, TIP39 appears to act on PTH2Rs present on MnPO glutamatergic terminals to regulate their activation of projection neurons and subsequent sympathetic BAT activation. This excitatory mechanism of heat production appears to be activated on demand, during cold exposure, and parallels the tonic inhibitory GABAergic control of body temperature. PMID:22159128

Noradrenaline induces CX3CL1 production and release by neurons.

PubMed

Madrigal, José L M; Caso, Javier R; García-Bueno, Borja; Gutiérrez, Irene L; Leza, Juan C

2017-03-01

CX3CL1 is a chemokine for which neurons constitute its primary source within the brain. Besides acting as a chemokine, CX3CL1 regulates multiple processes and is known to inhibit microglial activation. Because of this, CX3CL1 is considered as a messenger used by neurons to communicate with microglia. Similarly, the neurotransmitter noradrenaline reduces microglial activation and production of neurotoxic agents. Based on this, the regulation of neuronal CX3CXL1 by noradrenaline was analyzed. In primary cortical neurons, noradrenaline induced the accumulation of CX3CL1 protein and mRNA. Noradrenaline also increased CX3CL1 in its soluble form despite the inhibition of the activity and synthesis of ADAM10 and ADAM17, the main proteases known to cleave CX3CL1 from the neuronal membrane. Noradrenaline-treated neurons displayed a higher degree of dendritic arborization and a characteristic accumulation of CX3CL1 in the dendritic bifurcation zones. The soluble CX3CL1 produced by neurons after noradrenaline treatment, reduced the accumulation of nitrites in microglia. These findings indicate that NA anti-inflammatory actions are mediated by neuronal CX3CL1. In addition, CX3CL1 seems to be involved in the development of neuronal processes stimulated by noradrenaline. Copyright © 2016 Elsevier Ltd. All rights reserved.

Modulation of gastrointestinal vagal neurocircuits by hyperglycemia

PubMed Central

Browning, Kirsteen N.

2013-01-01

Glucose sensing within autonomic neurocircuits is critical for the effective integration and regulation of a variety of physiological homeostatic functions including the co-ordination of vagally-mediated reflexes regulating gastrointestinal (GI) functions. Glucose regulates GI functions via actions at multiple sites of action, from modulating the activity of enteric neurons, endocrine cells, and glucose transporters within the intestine, to regulating the activity and responsiveness of the peripheral terminals, cell bodies and central terminals of vagal sensory neurons, to modifying both the activity and synaptic responsiveness of central brainstem neurons. Unsurprisingly, significant impairment in GI functions occurs in pathophysiological states where glucose levels are dysregulated, such as diabetes. A substantial obstacle to the development of new therapies to modify the disease, rather than treat the symptoms, are the gaps in our understanding of the mechanisms by which glucose modulates GI functions, particularly vagally-mediated responses and a more complete understanding of disease-related plasticity within these neurocircuits may open new avenues and targets for research. PMID:24324393

Making sense of the sensory regulation of hunger neurons.

PubMed

Chen, Yiming; Knight, Zachary A

2016-04-01

AgRP and POMC neurons are two key cell types that regulate feeding in response to hormones and nutrients. Recently, it was discovered that these neurons are also rapidly modulated by the mere sight and smell of food. This rapid sensory regulation "resets" the activity of AgRP and POMC neurons before a single bite of food has been consumed. This surprising and counterintuitive discovery challenges longstanding assumptions about the function and regulation of these cells. Here we review these recent findings and discuss their implications for our understanding of feeding behavior. We propose several alternative hypotheses for how these new observations might be integrated into a revised model of the feeding circuit, and also highlight some of the key questions that remain to be answered. © 2016 WILEY Periodicals, Inc.

Making sense of the sensory regulation of hunger neurons

PubMed Central

Chen, Yiming; Knight, Zachary A.

2016-01-01

AgRP and POMC neurons are two key cell types that regulate feeding in response to hormones and nutrients. Recently, it was discovered that these neurons are also rapidly modulated by the mere sight and smell of food. This rapid sensory regulation “resets” the activity of AgRP and POMC neurons before a single bite of food has been consumed. This surprising and counterintuitive discovery challenges longstanding assumptions about the function and regulation of these cells. Here we review these recent findings and discuss their implications for our understanding of feeding behavior. We propose several alternative hypotheses for how these new observations might be integrated into a revised model of the feeding circuit, and also highlight some of the key questions that remain to be answered. PMID:26898524

ACTIVITY-DEPENDENT, STRESS-RESPONSIVE BDNF SIGNALING AND THE QUEST FOR OPTIMAL BRAIN HEALTH AND RESILIENCE THROUGHOUT THE LIFESPAN

PubMed Central

Rothman, S. M.; Mattson, M. P.

2013-01-01

During development of the nervous system, the formation of connections (synapses) between neurons is dependent upon electrical activity in those neurons, and neurotrophic factors produced by target cells play a pivotal role in such activity-dependent sculpting of the neural networks. A similar interplay between neurotransmitter and neurotrophic factor signaling pathways mediates adaptive responses of neural networks to environmental demands in adult mammals, with the excitatory neurotransmitter glutamate and brain-derived neurotrophic factor (BDNF) being particularly prominent regulators of synaptic plasticity throughout the central nervous system. Optimal brain health throughout the lifespan is promoted by intermittent challenges such as exercise, cognitive stimulation and dietary energy restriction, that subject neurons to activity-related metabolic stress. At the molecular level, such challenges to neurons result in the production of proteins involved in neurogenesis, learning and memory and neuronal survival; examples include proteins that regulate mitochondrial biogenesis, protein quality control, and resistance of cells to oxidative, metabolic and proteotoxic stress. BDNF signaling mediates up-regulation of several such proteins including the protein chaperone GRP-78, antioxidant enzymes, the cell survival protein Bcl-2, and the DNA repair enzyme APE1. Insufficient exposure to such challenges, genetic factors may conspire to impair BDNF production and/or signaling resulting in the vulnerability of the brain to injury and neurodegenerative disorders including Alzheimer’s, Parkinson’s and Huntington’s diseases. Further, BDNF signaling is negatively regulated by glucocorticoids. Glucocorticoids impair synaptic plasticity in the brain by negatively regulating spine density, neurogenesis and long-term potentiation, effects that are potentially linked to glucocorticoid regulation of BDNF. Findings suggest that BDNF signaling in specific brain regions mediates some of the beneficial effects of exercise and energy restriction on peripheral energy metabolism and the cardiovascular system. Collectively, the findings described in this article suggest the possibility of developing prescriptions for optimal brain health based on activity-dependent BDNF signaling. PMID:23079624

Caudal fourth ventricular administration of the AMPK activator 5-aminoimidazole-4-carboxamide-riboside regulates glucose and counterregulatory hormone profiles, dorsal vagal complex metabolosensory neuron function, and hypothalamic Fos expression.

PubMed

Ibrahim, Baher A; Tamrakar, Pratistha; Gujar, Amit D; Cherian, Ajeesh Koshy; Briski, Karen P

2013-09-01

This study investigated the hypothesis that estrogen controls hindbrain AMP-activated protein kinase (AMPK) activity and regulation of blood glucose, counterregulatory hormone secretion, and hypothalamic nerve cell transcriptional status. Dorsal vagal complex A2 noradrenergic neurons were laser microdissected from estradiol benzoate (E)- or oil (O)-implanted ovariectomized female rats after caudal fourth ventricular (CV4) delivery of the AMPK activator 5-aminoimidazole-4-carboxamide-riboside (AICAR), for Western blot analysis. E advanced AICAR-induced increases in A2 phospho-AMPK (pAMPK) expression and in blood glucose levels and was required for augmentation of Fos, estrogen receptor-α (ERα), monocarboxylate transporter-2, and glucose transporter-3 protein in A2 neurons and enhancement of corticosterone secretion by this treatment paradigm. CV4 AICAR also resulted in site-specific modifications in Fos immunolabeling of hypothalamic metabolic structures, including the paraventricular, ventromedial, and arcuate nuclei. The current studies demonstrate that estrogen regulates AMPK activation in caudal hindbrain A2 noradrenergic neurons during pharmacological replication of energy shortage in this area of the brain, and that this sensor is involved in neural regulation of glucostasis, in part, through control of corticosterone secretion. The data provide unique evidence that A2 neurons express both ERα and -β proteins and that AMPK upregulates cellular sensitivity to ERα-mediated signaling during simulated energy insufficiency. The results also imply that estrogen promotes glucose and lactate uptake by these cells under those conditions. Evidence for correlation between hindbrain AMPK and hypothalamic nerve cell genomic activation provides novel proof for functional connectivity between this hindbrain sensor and higher order metabolic brain loci while demonstrating a modulatory role for estrogen in this interaction. Copyright © 2013 Wiley Periodicals, Inc.

Dopamine Induces Oscillatory Activities in Human Midbrain Neurons with Parkin Mutations.

PubMed

Zhong, Ping; Hu, Zhixing; Jiang, Houbo; Yan, Zhen; Feng, Jian

2017-05-02

Locomotor symptoms in Parkinson's disease (PD) are accompanied by widespread oscillatory neuronal activities in basal ganglia. Here, we show that activation of dopamine D1-class receptors elicits a large rhythmic bursting of spontaneous excitatory postsynaptic currents (sEPSCs) in midbrain neurons differentiated from induced pluripotent stem cells (iPSCs) of PD patients with parkin mutations, but not normal subjects. Overexpression of wild-type parkin, but not its PD-causing mutant, abolishes the oscillatory activities in patient neurons. Dopamine induces a delayed enhancement in the amplitude of spontaneous, but not miniature, EPSCs, thus increasing quantal content. The results suggest that presynaptic regulation of glutamatergic transmission by dopamine D1-class receptors is significantly potentiated by parkin mutations. The aberrant dopaminergic regulation of presynaptic glutamatergic transmission in patient-specific iPSC-derived midbrain neurons provides a mechanistic clue to PD pathophysiology, and it demonstrates the usefulness of this model system in understanding how mutations of parkin cause movement symptoms in Parkinson's disease. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

Serotonin Control of Thermotaxis Memory Behavior in Nematode Caenorhabditis elegans

PubMed Central

Guo, Yuling; Wang, Daoyong; Li, Chaojun; Wang, Dayong

2013-01-01

Caenorhabditis elegans is as an ideal model system for the study of mechanisms underlying learning and memory. In the present study, we employed C. elegans assay system of thermotaxis memory to investigate the possible role of serotonin neurotransmitter in memory control. Our data showed that both mutations of tph-1, bas-1, and cat-4 genes, required for serotonin synthesis, and mutations of mod-5 gene, encoding a serotonin reuptake transporter, resulted in deficits in thermotaxis memory behavior. Exogenous treatment with serotonin effectively recovered the deficits in thermotaxis memory of tph-1 and bas-1 mutants to the level of wild-type N2. Neuron-specific activity assay of TPH-1 suggests that serotonin might regulate the thermotaxis memory behavior by release from the ADF sensory neurons. Ablation of ADF sensory neurons by expressing a cell-death activator gene egl-1 decreased the thermotaxis memory, whereas activation of ADF neurons by expression of a constitutively active protein kinase C homologue (pkc-1(gf)) increased the thermotaxis memory and rescued the deficits in thermotaxis memory in tph-1 mutants. Moreover, serotonin released from the ADF sensory neurons might act through the G-protein-coupled serotonin receptors of SER-4 and SER-7 to regulate the thermotaxis memory behavior. Genetic analysis implies that serotonin might further target the insulin signaling pathway to regulate the thermotaxis memory behavior. Thus, our results suggest the possible crucial role of serotonin and ADF sensory neurons in thermotaxis memory control in C. elegans. PMID:24223727

Pituitary adenylate cyclase-activating polypeptide: a novel peptide with protean implications.

PubMed

Pisegna, Joseph R; Oh, David S

2007-02-01

The purpose of this review is to highlight the importance of pituitary adenylate cyclase-activating polypeptide in physiological processes and to describe how this peptide is becoming increasingly recognized as having a major role in the body. Since its discovery in 1989, investigators have sought to determine the site of biological activity and the function of pituitary adenylate cyclase-activating polypeptide in maintaining homeostasis. Since its discovery, pituitary adenylate cyclase-activating polypeptide appears to play an important role in the regulation of processes within the central nervous system and gastrointestinal tract, as well in reproductive biology. Pituitary adenylate cyclase-activating polypeptide has been shown to regulate tumor cell growth and to regulate immune function through its effects on T lympocytes. These discoveries suggest the importance of pituitary adenylate cyclase-activating polypeptide in neuronal development, neuronal function, gastrointestinal tract function and reproduction. Future studies will examine more closely the role of pituitary adenylate cyclase-activating polypeptide in regulation of malignantly transformed cells, as well as in regulation of immune function.

Kv2.2: a novel molecular target to study the role of basal forebrain GABAergic neurons in the sleep-wake cycle.

PubMed

Hermanstyne, Tracey O; Subedi, Kalpana; Le, Wei Wei; Hoffman, Gloria E; Meredith, Andrea L; Mong, Jessica A; Misonou, Hiroaki

2013-12-01

The basal forebrain (BF) has been implicated as an important brain region that regulates the sleep-wake cycle of animals. Gamma-aminobutyric acidergic (GABAergic) neurons are the most predominant neuronal population within this region. However, due to the lack of specific molecular tools, the roles of the BF GABAergic neurons have not been fully elucidated. Previously, we have found high expression levels of the Kv2.2 voltage-gated potassium channel on approximately 60% of GABAergic neurons in the magnocellular preoptic area and horizontal limb of the diagonal band of Broca of the BF and therefore proposed it as a potential molecular target to study this neuronal population. In this study, we sought to determine the functional roles of the Kv2.2-expressing neurons in the regulation of the sleep-wake cycle. Sleep analysis between two genotypes and within each genotype before and after sleep deprivation. Animal sleep research laboratory. Adult mice. Wild-type and Kv2.2 knockout mice with C57/BL6 background. EEG/EMG recordings from the basal state and after sleep-deprivation which was induced by mild agitation for 6 h. Immunostaining of a marker of neuronal activity indicates that these Kv2.2-expressing neurons appear to be preferentially active during the wake state. Therefore, we tested whether Kv2.2-expressing neurons in the BF are involved in arousal using Kv2.2-deficient mice. BF GABAergic neurons exhibited augmented expression of c-Fos. These knockout mice exhibited longer consolidated wake bouts than wild-type littermates, and that phenotype was further exacerbated by sleep deprivation. Moreover, in-depth analyses of their cortical electroencephalogram revealed a significant decrease in the delta-frequency activity during the nonrapid eye movement sleep state. These results revealed the significance of Kv2.2-expressing neurons in the regulation of the sleep-wake cycle.

Phosphorylation status of pyruvate dehydrogenase distinguishes metabolic phenotypes of cultured rat brain astrocytes and neurons.

PubMed

Halim, Nader D; Mcfate, Thomas; Mohyeldin, Ahmed; Okagaki, Peter; Korotchkina, Lioubov G; Patel, Mulchand S; Jeoung, Nam Ho; Harris, Robert A; Schell, Michael J; Verma, Ajay

2010-08-01

Glucose metabolism in nervous tissue has been proposed to occur in a compartmentalized manner with astrocytes contributing largely to glycolysis and neurons being the primary site of glucose oxidation. However, mammalian astrocytes and neurons both contain mitochondria, and it remains unclear why in culture neurons oxidize glucose, lactate, and pyruvate to a much larger extent than astrocytes. The objective of this study was to determine whether pyruvate metabolism is differentially regulated in cultured neurons versus astrocytes. Expression of all components of the pyruvate dehydrogenase complex (PDC), the rate-limiting step for pyruvate entry into the Krebs cycle, was determined in cultured astrocytes and neurons. In addition, regulation of PDC enzymatic activity in the two cell types via protein phosphorylation was examined. We show that all components of the PDC are expressed in both cell types in culture, but that PDC activity is kept strongly inhibited in astrocytes through phosphorylation of the pyruvate dehydrogenase alpha subunit (PDH alpha). In contrast, neuronal PDC operates close to maximal levels with much lower levels of phosphorylated PDH alpha. Dephosphorylation of astrocytic PDH alpha restores PDC activity and lowers lactate production. Our findings suggest that the glucose metabolism of astrocytes and neurons may be far more flexible than previously believed. (c) 2010 Wiley-Liss, Inc.

[A neuronal analysis of the hunting behavior of sea butterfly Clione limacina].

PubMed

Norekian, T P; Satterly, R

1991-01-01

Neurones of the cerebral ganglia controlling the movements of the hunting apparatus of predatory pelagic mollusc Clione limacina are described in detail. A large group is identified of high-threshold electrically interconnected neurones A, the impulse activity of which leads to the opening of the skin folds and throwing forward Clione catching tentacles. Neurones of B group, having constant background activity and receiving powerful inhibitory inputs from A cells, on the contrary, elicit contraction and drawing in of the hunting tentacles inside the head. The third group--C neurons, the impulse activity of which leads to tightening of the skin folds covering the hunting apparatus. The action has been studied on identified neurones of such transmitters as serotonine, dopamine and gamma-aminobutyric acid. Serotonine depolarises both A and B neurones, but activation of the hunting apparatus is an integrating effect: activated neurones A owing to powerful TPSP inhibit neurones B, interrupting direct exciting action of serotonine. Dopamine in different concentrations has an opposite effect: at low concentrations only B cells are activated and tentacles are drawn inside the head; at high ones the neurones A start working which inhibit B cells and activate the hunting apparatus. GABA renders to neurones, regulating the movements of the hunting apparatus a total, well coordinated action directed to activation of the hunting behaviour: it depolarises-activates A neurones and hyperpolarises-inhibits neurones of B and C groups.

TMEM150C/Tentonin3 Is a Regulator of Mechano-gated Ion Channels.

PubMed

Anderson, Evan O; Schneider, Eve R; Matson, Jon D; Gracheva, Elena O; Bagriantsev, Sviatoslav N

2018-04-17

Neuronal mechano-sensitivity relies on mechano-gated ion channels, but pathways regulating their activity remain poorly understood. TMEM150C was proposed to mediate mechano-activated current in proprioceptive neurons. Here, we studied functional interaction of TMEM150C with mechano-gated ion channels from different classes (Piezo2, Piezo1, and the potassium channel TREK-1) using two independent methods of mechanical stimulation. We found that TMEM150C significantly prolongs the duration of the mechano-current produced by all three channels, decreases apparent activation threshold in Piezo2, and induces persistent current in Piezo1. We also show that TMEM150C is co-expressed with Piezo2 in trigeminal neurons, expanding its role beyond proprioceptors. Finally, we cloned TMEM150C from the trigeminal neurons of the tactile-foraging domestic duck and showed that it functions similarly to the mouse ortholog, demonstrating evolutionary conservation among vertebrates. Our studies reveal TMEM150C as a general regulator of mechano-gated ion channels from different classes. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

Regulation of Energy Stores and Feeding by Neuronal and Peripheral CREB Activity in Drosophila

PubMed Central

Iijima, Koichi; Zhao, LiJuan; Shenton, Christopher; Iijima-Ando, Kanae

2009-01-01

The cAMP-responsive transcription factor CREB functions in adipose tissue and liver to regulate glycogen and lipid metabolism in mammals. While Drosophila has a homolog of mammalian CREB, dCREB2, its role in energy metabolism is not fully understood. Using tissue-specific expression of a dominant-negative form of CREB (DN-CREB), we have examined the effect of blocking CREB activity in neurons and in the fat body, the primary energy storage depot with functions of adipose tissue and the liver in flies, on energy balance, stress resistance and feeding behavior. We found that disruption of CREB function in neurons reduced glycogen and lipid stores and increased sensitivity to starvation. Expression of DN-CREB in the fat body also reduced glycogen levels, while it did not affect starvation sensitivity, presumably due to increased lipid levels in these flies. Interestingly, blocking CREB activity in the fat body increased food intake. These flies did not show a significant change in overall body size, suggesting that disruption of CREB activity in the fat body caused an obese-like phenotype. Using a transgenic CRE-luciferase reporter, we further demonstrated that disruption of the adipokinetic hormone receptor, which is functionally related to mammalian glucagon and β-adrenergic signaling, in the fat body reduced CRE-mediated transcription in flies. This study demonstrates that CREB activity in either neuronal or peripheral tissues regulates energy balance in Drosophila, and that the key signaling pathway regulating CREB activity in peripheral tissue is evolutionarily conserved. PMID:20041126

Sulforaphane attenuates microglia-mediated neuronal necroptosis through down-regulation of MAPK/NF-κB signaling pathways in LPS-activated BV-2 microglia.

PubMed

Qin, Sisi; Yang, Canhong; Huang, Weihua; Du, Shuhua; Mai, Hantao; Xiao, Jijie; Lü, Tianming

2018-01-31

Sulforaphane (SFN), a natural dietary isothiocyanate in cruciferous vegetables such as broccoli and cabbage, has very strong anti-inflammatory activity. Activation of microglia leads to overexpression of a series of pro-inflammatory mediators, which play a vital role in neuronal damage. SFN may have neuroprotective effects in different neurodegenerative diseases related to inflammation. However, the mechanisms underlying SFN's protection of neurons against microglia-mediated neuronal damage are not fully understood. Here, we investigated how SFN attenuated microglia-mediated neuronal damage. Our results showed that SFN could not directly protect the viability of neurons following pro-inflammatory mediators, but increased the viability of BV-2 microglia and down-regulated the mRNA and protein levels of pro-inflammatory mediators including TNF-α, IL-1β, IL-6 and iNOS in a concentration-dependent manner in BV-2 cells. SFN also significantly blocked the phosphorylation of MAPKs (p38, JNK, and ERK1/2) and NF-κB p65, both by itself and with MAPK inhibitors (SB203580, SP 600125, and U0126) or an NF-κB inhibitor (PDTC). The expression of pro-inflammatory proteins was also blocked by SFN with or without inhibitors. Further, SFN indirectly increased the viability and maintained the morphology of neurons, and the protein expression of RIPK3 and MLKL was significantly suppressed by SFN in neuronal necroptosis through p38, JNK, and NF-κB p65 but not ERK1/2 signaling pathways. Together, our results demonstrate that SFN attenuates LPS-induced pro-inflammatory responses through down-regulation of MAPK/NF-κB signaling pathway in BV-2 microglia and thus indirectly suppresses microglia-mediated neuronal damage. Copyright © 2018 Elsevier Ltd. All rights reserved.

Dendrosomatic Sonic Hedgehog Signaling in Hippocampal Neurons Regulates Axon Elongation

PubMed Central

Petralia, Ronald S.; Ott, Carolyn; Wang, Ya-Xian; Lippincott-Schwartz, Jennifer; Mattson, Mark P.

2015-01-01

The presence of Sonic Hedgehog (Shh) and its signaling components in the neurons of the hippocampus raises a question about what role the Shh signaling pathway may play in these neurons. We show here that activation of the Shh signaling pathway stimulates axon elongation in rat hippocampal neurons. This Shh-induced effect depends on the pathway transducer Smoothened (Smo) and the transcription factor Gli1. The axon itself does not respond directly to Shh; instead, the Shh signal transduction originates from the somatodendritic region of the neurons and occurs in neurons with and without detectable primary cilia. Upon Shh stimulation, Smo localization to dendrites increases significantly. Shh pathway activation results in increased levels of profilin1 (Pfn1), an actin-binding protein. Mutations in Pfn1's actin-binding sites or reduction of Pfn1 eliminate the Shh-induced axon elongation. These findings indicate that Shh can regulate axon growth, which may be critical for development of hippocampal neurons. SIGNIFICANCE STATEMENT Although numerous signaling mechanisms have been identified that act directly on axons to regulate their outgrowth, it is not known whether signals transduced in dendrites may also affect axon outgrowth. We describe here a transcellular signaling pathway in embryonic hippocampal neurons in which activation of Sonic Hedgehog (Shh) receptors in dendrites stimulates axon growth. The pathway involves the dendritic-membrane-associated Shh signal transducer Smoothened (Smo) and the transcription factor Gli, which induces the expression of the gene encoding the actin-binding protein profilin 1. Our findings suggest scenarios in which stimulation of Shh in dendrites results in accelerated outgrowth of the axon, which therefore reaches its presumptive postsynaptic target cell more quickly. By this mechanism, Shh may play critical roles in the development of hippocampal neuronal circuits. PMID:26658865

Functional identification of activity-regulated, high-affinity glutamine transport in hippocampal neurons inhibited by riluzole.

PubMed

Erickson, Jeffrey D

2017-07-01

Glutamine (Gln) is considered the preferred precursor for the neurotransmitter pool of glutamate (Glu), the major excitatory transmitter in the mammalian CNS. Here, an activity-regulated, high-affinity Gln transport system is described in developing and mature neuron-enriched hippocampal cultures that is potently inhibited by riluzole (IC 50 1.3 ± 0.5 μM), an anti-glutamatergic drug, and is blocked by low concentrations of 2-(methylamino)isobutyrate (MeAIB), a system A transport inhibitor. K + -stimulated MeAIB transport displays an affinity (K m ) for MeAIB of 37 ± 1.2 μM, saturates at ~ 200 μM, is dependent on extracellular Ca 2+ , and is blocked by inhibition of voltage-gated Ca 2+ channels. Spontaneous MeAIB transport is also dependent on extracellullar Ca 2+ and voltage-gated calcium channels, but is also blocked by the Na + channel blocker tetrodotoxin, by Glu receptor antagonists, and by GABA indicating its dependence on intact neural circuits driven by endogenous glutamatergic activity. The transport of MeAIB itself does not rely on Ca 2+ , but on Na + ions, and is pH sensitive. Activity-regulated, riluzole-sensitive spontaneous and K + -stimulated transport is minimal at 7-8 days in vitro, coordinately induced during the next 2 weeks and is maximally expressed by days in vitro > 20; the known period for maturation of the Glu/Gln cycle and regulated pre-synaptic Glu release. Competition analyses with various amino acids indicate that Gln is the most likely physiological substrate. Activity-regulated Gln/MeAIB transport is not observed in astrocytes. The functional identification of activity-regulated, high-affinity, riluzole-sensitive Gln/MeAIB transport in hippocampal neurons may have important ramifications in the neurobiology of activity-stimulated pre-synaptic Glu release, the Glu/Gln cycle between astrocytes and neurons, and neuronal Glu-induced excitotoxicity. Cover Image for this issue: doi: 10.1111/jnc.13805. © 2017 International Society for Neurochemistry.

Photoreceptive oscillators within neurons of the premammillary nucleus (PMM) and seasonal reproduction in temperate zone birds.

PubMed

Kosonsiriluk, Sunantha; Mauro, Laura J; Chaiworakul, Voravasa; Chaiseha, Yupaporn; El Halawani, Mohamed E

2013-09-01

The pathway for light transmission regulating the reproductive neuroendocrine system in temperate zone birds remains elusive. Based on the evidence provided from our studies with female turkeys, it is suggested that the circadian clock regulating reproductive seasonality is located in putatively photosensitive dopamine-melatonin (DA-MEL) neurons residing in the premammillary nucleus (PMM) of the caudal hypothalamus. Melanopsin is expressed by these neurons; a known photopigment which mediates light information pertaining to the entrainment of the clock. Exposure to a gonad stimulatory photoperiod enhances the activity of the DAergic system within DA-MEL neurons. DAergic activity encoding the light information is transmitted to the pars tuberalis, where thyroid-stimulating hormone, beta (TSHβ) cells reside, and induces the release of TSH. TSH stimulates tanycytes lining the base of the third ventricle and activates type 2 deiodinase in the ependymal which enhances triiodothyronine (T3) synthesis. T3 facilitates the release of gonadotropin-releasing hormone-I which stimulates luteinizing hormone/follicle stimulating hormone release and gonad recrudescence. These data taken together with the findings that clock genes are rhythmically expressed in the PMM where DA-MEL neurons are localized imply that endogenous oscillators containing photoreceptors within DA-MEL neurons are important in regulating the DA and MEL rhythms that drive the circadian cycle controlling seasonal reproduction. Published by Elsevier Inc.

Endogenous opioids regulate moment-to-moment neuronal communication and excitability.

PubMed

Winters, Bryony L; Gregoriou, Gabrielle C; Kissiwaa, Sarah A; Wells, Oliver A; Medagoda, Danashi I; Hermes, Sam M; Burford, Neil T; Alt, Andrew; Aicher, Sue A; Bagley, Elena E

2017-03-22

Fear and emotional learning are modulated by endogenous opioids but the cellular basis for this is unknown. The intercalated cells (ITCs) gate amygdala output and thus regulate the fear response. Here we find endogenous opioids are released by synaptic stimulation to act via two distinct mechanisms within the main ITC cluster. Endogenously released opioids inhibit glutamate release through the δ-opioid receptor (DOR), an effect potentiated by a DOR-positive allosteric modulator. Postsynaptically, the opioids activate a potassium conductance through the μ-opioid receptor (MOR), suggesting for the first time that endogenously released opioids directly regulate neuronal excitability. Ultrastructural localization of endogenous ligands support these functional findings. This study demonstrates a new role for endogenously released opioids as neuromodulators engaged by synaptic activity to regulate moment-to-moment neuronal communication and excitability. These distinct actions through MOR and DOR may underlie the opposing effect of these receptor systems on anxiety and fear.

Down-regulation of voltage-dependent sodium channels initiated by sodium influx in developing neurons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dargent, B.; Couraud, F.

1990-08-01

To address the issue of whether regulatory feedback exists between the electrical activity of a neuron and ion-channel density, the authors investigated the effect of Na{sup +}-channel activators (scorpion {alpha} toxin, batrachotoxin, and veratridine) on the density of Na{sup +} channels in fetal rat brain neurons in vitro. A partial but rapid (t{sub 1/2}, 15 min) disappearance of surface Na{sup +} channels was observed as measured by a decrease in the specific binding of ({sup 3}H)saxitoxin and {sup 125}I-labeled scorpion {beta} toxin and a decrease in specific {sup 22}Na{sup +} uptake. Moreover, the increase in the number of Na{sup +}more » channels that normally occurs during neuronal maturation in vitro was inhibited by chronic channel activator treatment. The induced disappearance of Na{sup +} channels was abolished by tetrodotoxin, was found to be dependent on the external Na{sup +} concentration, and was prevented when either choline (a nonpermeant ion) or Li{sup +} (a permeant ion) was substituted for Na{sup +}. Amphotericin B, a Na{sup +} ionophore, and monensin were able to mimick the effect of Na{sup +}-channel activators, while a KCl depolarization failed to do this. This feedback regulation seems to be a neuronal property since Na{sup +}-channel density in cultured astrocytes was not affected by channel activator treatment or by amphotericin B. The present evidence suggests that an increase in intracellular Na{sup +} concentration, whether elicited by Na{sup +}-channel activators or mediated by a Na{sup +} ionophore, can induce a decrease in surface Na{sup +} channels and therefore is involved in down-regulation of Na{sup +}-channel density in fetal rat brain neurons in vitro.« less

Glucose level determines excitatory or inhibitory effects of adiponectin on arcuate POMC neuron activity and feeding.

PubMed

Suyama, Shigetomo; Maekawa, Fumihiko; Maejima, Yuko; Kubota, Naoto; Kadowaki, Takashi; Yada, Toshihiko

2016-08-09

Adiponectin regulates glucose and lipid metabolism, acting against metabolic syndrome and atherosclerosis. Accumulating evidence suggest that adiponectin acts on the brain including hypothalamic arcuate nucleus (ARC), where proopiomelanocortin (POMC) neurons play key roles in feeding regulation. Several studies have examined intracerebroventricular (ICV) injection of adiponectin and reported opposite effects, increase or decrease of food intake. These reports used different nutritional states. The present study aimed to clarify whether adiponectin exerts distinct effects on food intake and ARC POMC neurons depending on the glucose concentration. Adiponectin was ICV injected with or without glucose for feeding experiments and administered to ARC slices with high or low glucose for patch clamp experiments. We found that adiponectin at high glucose inhibited POMC neurons and increased food intake while at low glucose it exerted opposite effects. The results demonstrate that glucose level determines excitatory or inhibitory effects of adiponectin on arcuate POMC neuron activity and feeding.

AgRP Neurons Can Increase Food Intake during Conditions of Appetite Suppression and Inhibit Anorexigenic Parabrachial Neurons.

PubMed

Essner, Rachel A; Smith, Alison G; Jamnik, Adam A; Ryba, Anna R; Trutner, Zoe D; Carter, Matthew E

2017-09-06

To maintain energy homeostasis, orexigenic (appetite-inducing) and anorexigenic (appetite suppressing) brain systems functionally interact to regulate food intake. Within the hypothalamus, neurons that express agouti-related protein (AgRP) sense orexigenic factors and orchestrate an increase in food-seeking behavior. In contrast, calcitonin gene-related peptide (CGRP)-expressing neurons in the parabrachial nucleus (PBN) suppress feeding. PBN CGRP neurons become active in response to anorexigenic hormones released following a meal, including amylin, secreted by the pancreas, and cholecystokinin (CCK), secreted by the small intestine. Additionally, exogenous compounds, such as lithium chloride (LiCl), a salt that creates gastric discomfort, and lipopolysaccharide (LPS), a bacterial cell wall component that induces inflammation, exert appetite-suppressing effects and activate PBN CGRP neurons. The effects of increasing the homeostatic drive to eat on feeding behavior during appetite suppressing conditions are unknown. Here, we show in mice that food deprivation or optogenetic activation of AgRP neurons induces feeding to overcome the appetite suppressing effects of amylin, CCK, and LiCl, but not LPS. AgRP neuron photostimulation can also increase feeding during chemogenetic-mediated stimulation of PBN CGRP neurons. AgRP neuron stimulation reduces Fos expression in PBN CGRP neurons across all conditions. Finally, stimulation of projections from AgRP neurons to the PBN increases feeding following administration of amylin, CCK, and LiCl, but not LPS. These results demonstrate that AgRP neurons are sufficient to increase feeding during noninflammatory-based appetite suppression and to decrease activity in anorexigenic PBN CGRP neurons, thereby increasing food intake during homeostatic need. SIGNIFICANCE STATEMENT The motivation to eat depends on the relative balance of activity in distinct brain regions that induce or suppress appetite. An abnormal amount of activity in neurons that induce appetite can cause obesity, whereas an abnormal amount of activity in neurons that suppress appetite can cause malnutrition and a severe reduction in body weight. The purpose of this study was to determine whether a population of neurons known to induce appetite ("AgRP neurons") could induce food intake to overcome appetite-suppression following administration of various appetite-suppressing compounds. We found that stimulating AgRP neurons could overcome various forms of appetite suppression and decrease neural activity in a separate population of appetite-suppressing neurons, providing new insights into how the brain regulates food intake. Copyright © 2017 the authors 0270-6474/17/378678-10$15.00/0.

Sirtuin7 is involved in protecting neurons against oxygen-glucose deprivation and reoxygenation-induced injury through regulation of the p53 signaling pathway.

PubMed

Lv, Jianrui; Tian, Junbin; Zheng, Guoxi; Zhao, Jing

2017-10-01

Sirtuin7 (SIRT7) is known to regulate apoptosis and stress responses. So far, very little is known about the role of SIRT7 in cerebral ischemia/reperfusion injury. In this study, we aimed to investigate the potential role of SIRT7 in regulating oxygen-glucose deprivation and reoxygenation (OGD/R)-induced injury in neurons. We found a significant increase of SIRT7 expression in neurons in response to OGD/R treatment. Knockdown of SIRT7 aggravated OGD/R-induced injury. Knockdown of SIRT7 augmented the levels of total and acetylated p53 protein. Moreover, knockdown of SIRT7 markedly increased the transcriptional activity of p53 toward apoptosis and activated the p53-mediated proapoptotic signaling pathway. By contrast, overexpression of SIRT7 showed the opposite effects. Taken together, the results of our study suggest that SIRT7 is involved in protecting neurons against OGD/R-induced injury, possibly through regulation of the p53-mediated proapoptotic signaling pathway, indicating a potential therapeutic target for cerebral ischemia/reperfusion injury. © 2017 Wiley Periodicals, Inc.

Sonic hedgehog pathway activation increases mitochondrial abundance and activity in hippocampal neurons

PubMed Central

Yao, Pamela J.; Manor, Uri; Petralia, Ronald S.; Brose, Rebecca D.; Wu, Ryan T. Y.; Ott, Carolyn; Wang, Ya-Xian; Charnoff, Ari; Lippincott-Schwartz, Jennifer; Mattson, Mark P.

2017-01-01

Mitochondria are essential organelles whose biogenesis, structure, and function are regulated by many signaling pathways. We present evidence that, in hippocampal neurons, activation of the Sonic hedgehog (Shh) signaling pathway affects multiple aspects of mitochondria. Mitochondrial mass was increased significantly in neurons treated with Shh. Using biochemical and fluorescence imaging analyses, we show that Shh signaling activity reduces mitochondrial fission and promotes mitochondrial elongation, at least in part, via suppression of the mitochondrial fission protein dynamin-like GTPase Drp1. Mitochondria from Shh-treated neurons were more electron-dense, as revealed by electron microscopy, and had higher membrane potential and respiratory activity. We further show that Shh protects neurons against a variety of stresses, including the mitochondrial poison rotenone, amyloid β-peptide, hydrogen peroxide, and high levels of glutamate. Collectively our data suggest a link between Shh pathway activity and the physiological properties of mitochondria in hippocampal neurons. PMID:27932496

Developmental and hormonal regulation of thermosensitive neuron potential activity in rat brain.

PubMed

Belugin, S; Akino, K; Takamura, N; Mine, M; Romanovsky, D; Fedoseev, V; Kubarko, A; Kosaka, M; Yamashita, S

1999-08-01

To understand the involvement of thyroid hormone on the postnatal development of hypothalamic thermosensitive neurons, we focused on the analysis of thermosensitive neuronal activity in the preoptic and anterior hypothalamic (PO/AH) regions of developing rats with and without hypothyroidism. In euthyroid rats, the distribution of thermosensitive neurons in PO/AH showed that in 3-week-old rats (46 neurons tested), 19.5% were warm-sensitive and 80.5% were nonsensitive. In 5- to 12-week-old euthyroid rats (122 neurons), 33.6% were warm-sensitive and 66.4% were nonsensitive. In 5- to 12-week-old hypothyroid rats (108 neurons), however, 18.5% were warm-sensitive and 81.5% were nonsensitive. Temperature thresholds of warm-sensitive neurons were lower in 12-week-old euthyroid rats (36.4+/-0.2 degrees C, n = 15, p<0.01,) than in 3-week-old and in 5-week-old euthyroid rats (38.5+/-0.5 degrees C, n = 9 and 38.0+/-0.3 degrees C, n = 15, respectively). The temperature thresholds of warm-sensitive neurons in 12-week-old hypothyroid rats (39.5+/-0.3 degrees C, n = 8) were similar to that of warm-sensitive neurons of 3-week-old raats (euthyroid and hypothyroid). In contrast, there was no difference in the thresholds of warm-sensitive neurons between hypothyroid and euthyroid rats at the age of 3-5 weeks. In conclusion, monitoring the thermosensitive neuronal tissue activity demonstrated the evidence that thyroid hormone regulates the maturation of warm-sensitive hypothalamic neurons in developing rat brain by electrophysiological analysis.

IGF-I: A Key Growth Factor that Regulates Neurogenesis and Synaptogenesis from Embryonic to Adult Stages of the Brain

PubMed Central

Nieto-Estévez, Vanesa; Defterali, Çağla; Vicario-Abejón, Carlos

2016-01-01

The generation of neurons in the adult mammalian brain requires the activation of quiescent neural stem cells (NSCs). This activation and the sequential steps of neuron formation from NSCs are regulated by a number of stimuli, which include growth factors. Insulin-like growth factor-I (IGF-I) exert pleiotropic effects, regulating multiple cellular processes depending on their concentration, cell type, and the developmental stage of the animal. Although IGF-I expression is relatively high in the embryonic brain its levels drop sharply in the adult brain except in neurogenic regions, i.e., the hippocampus (HP) and the subventricular zone-olfactory bulb (SVZ-OB). By contrast, the expression of IGF-IR remains relatively high in the brain irrespective of the age of the animal. Evidence indicates that IGF-I influences NSC proliferation and differentiation into neurons and glia as well as neuronal maturation including synapse formation. Furthermore, recent studies have shown that IGF-I not only promote adult neurogenesis by regulating NSC number and differentiation but also by influencing neuronal positioning and migration as described during SVZ-OB neurogenesis. In this article we will revise and discuss the actions reported for IGF-I signaling in a variety of in vitro and in vivo models, focusing on the maintenance and proliferation of NSCs/progenitors, neurogenesis, and neuron integration in synaptic circuits. PMID:26941597

Disruption of centrifugal inhibition to olfactory bulb granule cells impairs olfactory discrimination.

PubMed

Nunez-Parra, Alexia; Maurer, Robert K; Krahe, Krista; Smith, Richard S; Araneda, Ricardo C

2013-09-03

Granule cells (GCs) are the most abundant inhibitory neuronal type in the olfactory bulb and play a critical role in olfactory processing. GCs regulate the activity of principal neurons, the mitral cells, through dendrodendritic synapses, shaping the olfactory bulb output to other brain regions. GC excitability is regulated precisely by intrinsic and extrinsic inputs, and this regulation is fundamental for odor discrimination. Here, we used channelrhodopsin to stimulate GABAergic axons from the basal forebrain selectively and show that this stimulation generates reliable inhibitory responses in GCs. Furthermore, selective in vivo inhibition of GABAergic neurons in the basal forebrain by targeted expression of designer receptors exclusively activated by designer drugs produced a reversible impairment in the discrimination of structurally similar odors, indicating an important role of these inhibitory afferents in olfactory processing.

Bidirectional Anticipation of Future Osmotic Challenges by Vasopressin Neurons.

PubMed

Mandelblat-Cerf, Yael; Kim, Angela; Burgess, Christian R; Subramanian, Siva; Tannous, Bakhos A; Lowell, Bradford B; Andermann, Mark L

2017-01-04

Ingestion of water and food are major hypo- and hyperosmotic challenges. To protect the body from osmotic stress, posterior pituitary-projecting, vasopressin-secreting neurons (VP pp neurons) counter osmotic perturbations by altering their release of vasopressin, which controls renal water excretion. Vasopressin levels begin to fall within minutes of water consumption, even prior to changes in blood osmolality. To ascertain the precise temporal dynamics by which water or food ingestion affect VP pp neuron activity, we directly recorded the spiking and calcium activity of genetically defined VP pp neurons. In states of elevated osmolality, water availability rapidly decreased VP pp neuron activity within seconds, beginning prior to water ingestion, upon presentation of water-predicting cues. In contrast, food availability following food restriction rapidly increased VP pp neuron activity within seconds, but only following feeding onset. These rapid and distinct changes in activity during drinking and feeding suggest diverse neural mechanisms underlying anticipatory regulation of VP pp neurons. Published by Elsevier Inc.

Arc in synaptic plasticity: from gene to behavior

PubMed Central

Korb, Erica; Finkbeiner, Steven

2011-01-01

The activity-regulated cytoskeletal (Arc) gene encodes a protein that is critical for memory consolidation. Arc is one of the most tightly regulated molecules known: neuronal activity controls Arc mRNA induction, trafficking, and accumulation, and Arc protein production, localization and stability. Arc regulates synaptic strength through multiple mechanisms and is involved in essentially every known form of synaptic plasticity. It also mediates memory formation and is implicated in multiple neurological diseases. In this review, we will discuss how Arc is regulated and used as a tool to study neuronal activity. We will also attempt to clarify how its molecular functions correspond to its requirement for various forms of plasticity, discuss Arc’s role in behavior and disease, and highlight critical unresolved questions. PMID:21963089

Liver ERα regulates AgRP neuronal activity in the arcuate nucleus of female mice.

PubMed

Benedusi, Valeria; Della Torre, Sara; Mitro, Nico; Caruso, Donatella; Oberto, Alessandra; Tronel, Claire; Meda, Clara; Maggi, Adriana

2017-04-26

Recent work revealed the major role played by liver Estrogen Receptor α (ERα) in the regulation of metabolic and reproductive functions. By using mutant mice with liver-specific ablation of Erα, we here demonstrate that the hepatic ERα is essential for the modulation of the activity of Agouti Related Protein (AgRP) neurons in relation to the reproductive cycle and diet. Our results suggest that the alterations of hepatic lipid metabolism due to the lack of liver ERα activity are responsible for a neuroinflammatory status that induces refractoriness of AgRP neurons to reproductive and dietary stimuli. The study therefore points to the liver ERα as a necessary sensor for the coordination of systemic energy metabolism and reproductive functions.

Gs-coupled GPCR signalling in AgRP neurons triggers sustained increase in food intake

PubMed Central

Nakajima, Ken-ichiro; Cui, Zhenzhong; Li, Chia; Meister, Jaroslawna; Cui, Yinghong; Fu, Ou; Smith, Adam S.; Jain, Shalini; Lowell, Bradford B.; Krashes, Michael J.; Wess, Jürgen

2016-01-01

Agouti-related peptide (AgRP) neurons of the hypothalamus play a key role in regulating food intake and body weight, by releasing three different orexigenic molecules: AgRP; GABA; and neuropeptide Y. AgRP neurons express various G protein-coupled receptors (GPCRs) with different coupling properties, including Gs-linked GPCRs. At present, the potential role of Gs-coupled GPCRs in regulating the activity of AgRP neurons remains unknown. Here we show that the activation of Gs-coupled receptors expressed by AgRP neurons leads to a robust and sustained increase in food intake. We also provide detailed mechanistic data linking the stimulation of this class of receptors to the observed feeding phenotype. Moreover, we show that this pathway is clearly distinct from other GPCR signalling cascades that are operative in AgRP neurons. Our data suggest that drugs able to inhibit this signalling pathway may become useful for the treatment of obesity. PMID:26743492

Altered LARK Expression Perturbs Development and Physiology of the Drosophila PDF Clock Neurons

PubMed Central

Huang, Yanmei; Howlett, Eric; Stern, Michael; Jackson, F. Rob

2009-01-01

The LARK RNA-binding protein (RBP) has well documented roles in the circadian systems of Drosophila and mammals. Recent studies have demonstrated that the Drosophila LARK RBP is associated with many mRNA targets, in vivo, including those that regulate either neurophysiology or development of the nervous system. In the present study, we have employed conditional expression techniques to distinguish developmental and physiological functions of LARK for a defined class of neurons: the Pigment Dispersing Factor (PDF)-containing LNv clock neurons. We found that increased LARK expression during development dramatically alters the small LNv class of neurons with no obvious effects on the large LNv cells. Conversely, conditional expression of LARK at the adult stage results in altered clock protein rhythms and circadian locomotor activity, even though neural morphology is normal in such animals. Electrophysiological analyses at the larval neuromuscular junction indicate a role for LARK in regulating neuronal excitability. Altogether, our results demonstrate that LARK activity is critical for neuronal development and physiology. PMID:19303442

Investigating neuronal function with optically controllable proteins

PubMed Central

Zhou, Xin X.; Pan, Michael; Lin, Michael Z.

2015-01-01

In the nervous system, protein activities are highly regulated in space and time. This regulation allows for fine modulation of neuronal structure and function during development and adaptive responses. For example, neurite extension and synaptogenesis both involve localized and transient activation of cytoskeletal and signaling proteins, allowing changes in microarchitecture to occur rapidly and in a localized manner. To investigate the role of specific protein regulation events in these processes, methods to optically control the activity of specific proteins have been developed. In this review, we focus on how photosensory domains enable optical control over protein activity and have been used in neuroscience applications. These tools have demonstrated versatility in controlling various proteins and thereby cellular functions, and possess enormous potential for future applications in nervous systems. Just as optogenetic control of neuronal firing using opsins has changed how we investigate the function of cellular circuits in vivo, optical control may yet yield another revolution in how we study the circuitry of intracellular signaling in the brain. PMID:26257603

Differential regulation of microtubule severing by APC underlies distinct patterns of projection neuron and interneuron migration

PubMed Central

Eom, Tae-Yeon; Stanco, Amelia; Guo, Jiami; Wilkins, Gary; Deslauriers, Danielle; Yan, Jessica; Monckton, Chase; Blair, Josh; Oon, Eesim; Perez, Abby; Salas, Eduardo; Oh, Adrianna; Ghukasyan, Vladimir; Snider, William D.; Rubenstein, John L. R.; Anton, E. S.

2014-01-01

Coordinated migration of distinct classes of neurons to appropriate positions leads to the formation of functional neuronal circuitry in the cerebral cortex. Two major classes of cortical neurons, interneurons and projection neurons, utilize distinctly different modes (radial vs. tangential) and routes of migration to arrive at their final positions in the cerebral cortex. Here, we show that adenomatous polyposis coli (APC) modulates microtubule (MT) severing in interneurons to facilitate tangential mode of interneuron migration, but not the glial-guided, radial migration of projection neurons. APC regulates the stability and activity of the MT severing protein p60-katanin in interneurons to promote the rapid remodeling of neuronal processes necessary for interneuron migration. These findings reveal how severing and restructuring of MTs facilitate distinct modes of neuronal migration necessary for laminar organization of neurons in the developing cerebral cortex. PMID:25535916

MAP kinase-independent signaling in angiotensin II regulation of neuromodulation in SHR neurons.

PubMed

Yang, H; Raizada, M K

1998-09-01

Angiotensin II (Ang II), via its interaction with the angiotensin type 1 (AT1) receptor subtype, causes enhanced stimulation of norepinephrine (NE) neuromodulation. This involves increased transcription of NE transporter, tyrosine hydroxylase, and dopamine ss-hydroxylase genes in Wistar-Kyoto rat (WKY) brain neurons. AT1 receptor-mediated regulation of certain signaling events (such as activation of the Ras-Raf-1-mitogen activated protein (MAP) kinase signaling pathway, nuclear translocation of transcription factors such as Fos and Jun, and the interactions of these factors with AP-1 binding sites) is involved in this NE neuromodulation (Lu et al. J Cell Biol. 1996;135:1609-1617). The aim of this study was to compare the signal transduction mechanism of Ang II regulation of NE neuromodulation in WKY and spontaneously hypertensive rat (SHR) brain neurons, in view of the fact that AT1 receptor expression and Ang II stimulation of NE neuromodulation are higher in SHR neurons compared with WKY neurons. Despite this hyperactivity, Ang II stimulation of Ras, Raf-1, and MAP kinase activities was comparable between the neurons from WKY and SHR. Similarly, central injections of Ang II caused a comparable stimulation of MAP kinase in the hypothalamic and brain stem areas of adult WKY and SHR. Inhibition of MAP kinase by either an MAP kinase kinase inhibitor (PD98059) or an MAP kinase antisense oligonucleotide completely attenuated the stimulatory effects of Ang II on [3H]-NE uptake, NE transporter mRNA, and tyrosine hydroxylase mRNA levels in WKY neurons. These treatments resulted in only 43% to 50% inhibition of [3H]-NE uptake and NE transporter and tyrosine hydroxylase mRNAs in SHR neurons. Thus, Ang II stimulation of NE neuromodulation was completely blocked by MAP kinase inhibition in WKY neurons and only partially blocked in the SHR neurons. These observations suggest the presence of an additional signal transduction pathway involved in NE neuromodulation in SHR neurons that is independent of the MAP kinase pathway.

elPBN neurons regulate rVLM activity through elPBN-rVLM projections during activation of cardiac sympathetic afferent nerves

PubMed Central

Longhurst, John C.; Tjen-A-Looi, Stephanie C.; Fu, Liang-Wu

2016-01-01

The external lateral parabrachial nucleus (elPBN) within the pons and rostral ventrolateral medulla (rVLM) contributes to central processing of excitatory cardiovascular reflexes during stimulation of cardiac sympathetic afferent nerves (CSAN). However, the importance of elPBN cardiovascular neurons in regulation of rVLM activity during CSAN activation remains unclear. We hypothesized that CSAN stimulation excites the elPBN cardiovascular neurons and, in turn, increases rVLM activity through elPBN-rVLM projections. Compared with controls, in rats subjected to microinjection of retrograde tracer into the rVLM, the numbers of elPBN neurons double-labeled with c-Fos (an immediate early gene) and the tracer were increased after CSAN stimulation (P < 0.05). The majority of these elPBN neurons contain vesicular glutamate transporter 3. In cats, epicardial bradykinin and electrical stimulation of CSAN increased the activity of elPBN cardiovascular neurons, which was attenuated (n = 6, P < 0.05) after blockade of glutamate receptors with iontophoresis of kynurenic acid (Kyn, 25 mM). In separate cats, microinjection of Kyn (1.25 nmol/50 nl) into the elPBN reduced rVLM activity evoked by both bradykinin and electrical stimulation (n = 5, P < 0.05). Excitation of the elPBN with microinjection of dl-homocysteic acid (2 nmol/50 nl) significantly increased basal and CSAN-evoked rVLM activity. However, the enhanced rVLM activity induced by dl-homocysteic acid injected into the elPBN was reversed following iontophoresis of Kyn into the rVLM (n = 7, P < 0.05). These data suggest that cardiac sympathetic afferent stimulation activates cardiovascular neurons in the elPBN and rVLM sequentially through a monosynaptic (glutamatergic) excitatory elPBN-rVLM pathway. PMID:27225950

RNA sequencing from neural ensembles activated during fear conditioning in the mouse temporal association cortex

PubMed Central

Cho, Jin-Hyung; Huang, Ben S.; Gray, Jesse M.

2016-01-01

The stable formation of remote fear memories is thought to require neuronal gene induction in cortical ensembles that are activated during learning. However, the set of genes expressed specifically in these activated ensembles is not known; knowledge of such transcriptional profiles may offer insights into the molecular program underlying stable memory formation. Here we use RNA-Seq to identify genes whose expression is enriched in activated cortical ensembles labeled during associative fear learning. We first establish that mouse temporal association cortex (TeA) is required for remote recall of auditory fear memories. We then perform RNA-Seq in TeA neurons that are labeled by the activity reporter Arc-dVenus during learning. We identify 944 genes with enriched expression in Arc-dVenus+ neurons. These genes include markers of L2/3, L5b, and L6 excitatory neurons but not glial or inhibitory markers, confirming Arc-dVenus to be an excitatory neuron-specific but non-layer-specific activity reporter. Cross comparisons to other transcriptional profiles show that 125 of the enriched genes are also activity-regulated in vitro or induced by visual stimulus in the visual cortex, suggesting that they may be induced generally in the cortex in an experience-dependent fashion. Prominent among the enriched genes are those encoding potassium channels that down-regulate neuronal activity, suggesting the possibility that part of the molecular program induced by fear conditioning may initiate homeostatic plasticity. PMID:27557751

PGC-1α/ERRα-Sirt3 Pathway Regulates DAergic Neuronal Death by Directly Deacetylating SOD2 and ATP Synthase β

PubMed Central

Zhang, Xuefei; Ren, Xiaoqing; Zhang, Qi; Li, Zheyi; Ma, Shuaipeng; Bao, Jintao; Li, Zeyang; Bai, Xue; Zheng, Liangjun; Zhang, Zhong; Shang, Shujiang; Zhang, Chen; Wang, Chuangui; Cao, Liu

2016-01-01

Abstract Aims: Parkinson's disease (PD) heavily affects humans and little is known about its cause and pathogenesis. Sirtuin 3 (Sirt3) plays a key role in regulating mitochondrial dysfunction, which is the main cause of DAergic neuronal loss in PD. We investigated the mechanisms of neuroprotective role of Sirt3 in DAergic neuronal survival. Results: Sirt3 was reduced in 1-methyl-4-phenyl-1,2,3,6 tetrahydropyridine (MPTP)-treated neurons with its overexpression being neuroprotective. We identified that Sirt3 interacted with manganese superoxide dismutase (SOD2) and adenosine triphosphate (ATP) synthase β and modulated their activities by deacetylating SOD2 (K130) and ATP synthase β (K485) to prevent reactive oxygen species accumulation and ATP depletion, and to alleviate DAergic neuronal death upon MPTP treatment. Peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) interacted with estrogen-related receptor alpha (ERRα) that bound to the Sirt3 promoter as its transcription factor to regulate Sirt3 expression and DAergic neuronal death. In the mouse midbrain, MPTP administration led to the loss of PGC-1α and Sirt3, high acetylation level of SOD2 and ATP synthase β, and the specific loss of DAergic neurons, while Sirt3 overexpression could protect against DAergic neuronal loss. Sirt3 knockout mice exhibited more sensitive and more DAergic neuronal loss to MPTP treatment. Innovation: The study provides new insights into a critical PGC-1α/ERRα-Sirt3 pathway, linking regulation of mitochondrial protein acetylation and DAergic neuronal death in PD pathogenesis, which provide a potential therapeutic strategy and target in PD treatment. Conclusion: These results provide a vital PGC-1α/ERRα-Sirt3 pathway that protects against DAergic neuronal death by directly deacetylating SOD2 (K130) and ATP synthase β (K485) in PD. Antioxid. Redox Signal. 24, 312–328. PMID:26421366

Activation of Ih and TTX-sensitive sodium current at subthreshold voltages during CA1 pyramidal neuron firing

PubMed Central

Yamada-Hanff, Jason

2015-01-01

We used dynamic clamp and action potential clamp techniques to explore how currents carried by tetrodotoxin-sensitive sodium channels and HCN channels (Ih) regulate the behavior of CA1 pyramidal neurons at resting and subthreshold voltages. Recording from rat CA1 pyramidal neurons in hippocampal slices, we found that the apparent input resistance and membrane time constant were strongly affected by both conductances, with Ih acting to decrease apparent input resistance and time constant and sodium current acting to increase both. We found that both Ih and sodium current were active during subthreshold summation of artificial excitatory postsynaptic potentials (EPSPs) generated by dynamic clamp, with Ih dominating at less depolarized voltages and sodium current at more depolarized voltages. Subthreshold sodium current—which amplifies EPSPs—was most effectively recruited by rapid voltage changes, while Ih—which blunts EPSPs—was maximal for slow voltage changes. The combined effect is to selectively amplify rapid EPSPs. We did similar experiments in mouse CA1 pyramidal neurons, doing voltage-clamp experiments using experimental records of action potential firing of CA1 neurons previously recorded in awake, behaving animals as command voltages to quantify flow of Ih and sodium current at subthreshold voltages. Subthreshold sodium current was larger and subthreshold Ih was smaller in mouse neurons than in rat neurons. Overall, the results show opposing effects of subthreshold sodium current and Ih in regulating subthreshold behavior of CA1 neurons, with subthreshold sodium current prominent in both rat and mouse CA1 pyramidal neurons and additional regulation by Ih in rat neurons. PMID:26289465

Cellular manganese content is developmentally regulated in human dopaminergic neurons

NASA Astrophysics Data System (ADS)

Kumar, Kevin K.; Lowe, Edward W., Jr.; Aboud, Asad A.; Neely, M. Diana; Redha, Rey; Bauer, Joshua A.; Odak, Mihir; Weaver, C. David; Meiler, Jens; Aschner, Michael; Bowman, Aaron B.

2014-10-01

Manganese (Mn) is both an essential biological cofactor and neurotoxicant. Disruption of Mn biology in the basal ganglia has been implicated in the pathogenesis of neurodegenerative disorders, such as parkinsonism and Huntington's disease. Handling of other essential metals (e.g. iron and zinc) occurs via complex intracellular signaling networks that link metal detection and transport systems. However, beyond several non-selective transporters, little is known about the intracellular processes regulating neuronal Mn homeostasis. We hypothesized that small molecules that modulate intracellular Mn could provide insight into cell-level Mn regulatory mechanisms. We performed a high throughput screen of 40,167 small molecules for modifiers of cellular Mn content in a mouse striatal neuron cell line. Following stringent validation assays and chemical informatics, we obtained a chemical `toolbox' of 41 small molecules with diverse structure-activity relationships that can alter intracellular Mn levels under biologically relevant Mn exposures. We utilized this toolbox to test for differential regulation of Mn handling in human floor-plate lineage dopaminergic neurons, a lineage especially vulnerable to environmental Mn exposure. We report differential Mn accumulation between developmental stages and stage-specific differences in the Mn-altering activity of individual small molecules. This work demonstrates cell-level regulation of Mn content across neuronal differentiation.

Neurotrophin responsiveness of sympathetic neurons is regulated by rapid mobilization of the p75 receptor to the cell surface through TrkA activation of Arf6.

PubMed

Edward Hickman, F; Stanley, Emily M; Carter, Bruce D

2018-05-22

The p75 neurotrophin receptor (p75NTR) plays an integral role in patterning the sympathetic nervous system during development. Initially, p75NTR is expressed at low levels as sympathetic axons project toward their targets, which enables neurotrophin-3 (NT3) to activate TrkA receptors and promote growth. Upon reaching nerve growth factor (NGF) producing tissues, p75NTR is up regulated resulting in formation of TrkA-p75 complexes, which are high affinity binding sites selective for NGF, thereby blunting NT3 signaling. The level of p75NTR expressed on the neuron surface is instrumental in regulating trophic factor response; however, the mechanisms by which p75NTR expression is regulated are poorly understood. Here, we demonstrate a rapid, translation independent increase in surface expression of p75NTR in response to NGF in rat sympathetic neurons. p75NTR was mobilized to the neuron surface from GGA3-postitive vesicles through activation of the GTPase Arf6, which was stimulated by NGF, but not NT3 binding to TrkA. Arf6 activation required PI3 kinase activity and was prevented by an inhibitor of the cytohesin family of Arf6 GEFs. Overexpression of a constitutively active Arf6 mutant (Q67L) was sufficient to significantly increase surface expression of p75NTR even in the absence of NGF. Functionally, expression of active Arf6 markedly attenuated the ability of NT3 to promote neuronal survival and neurite outgrowth while the NGF response was unaltered. These data suggest that NGF activation of Arf6 through TrkA is critical for the increase in p75NTR surface expression that enables the switch in neurotrophin responsiveness during development in the sympathetic nervous system. SIGNIFICANCE STATEMENT p75NTR is instrumental in the regulation of neuronal survival and apoptosis during development and is also implicated as a contributor to aberrant neurodegeneration in numerous conditions. Therefore, a better understanding of the mechanisms that mediate p75NTR surface availability, may provide insight into how and why neurodegenerative processes manifest and reveal new therapeutic targets. Results from this study indicate a novel mechanism by which p75NTR can be rapidly shuttled to the cell surface from existing intracellular pools and explores a unique pathway by which NGF regulates the sympathetic innervation of target tissues, which has profound consequences for the function of these organs. Copyright © 2018 the authors.

Melanin-concentrating hormone neurons discharge in a reciprocal manner to orexin neurons across the sleep–wake cycle

PubMed Central

Hassani, Oum Kaltoum; Lee, Maan Gee; Jones, Barbara E.

2009-01-01

Neurons containing melanin-concentrating hormone (MCH) are codistributed with neurons containing orexin (Orx or hypocretin) in the lateral hypothalamus, a peptide and region known to be critical for maintaining wakefulness. Evidence from knockout and c-Fos studies suggests, however, that the MCH neurons might play a different role than Orx neurons in regulating activity and sleep–wake states. To examine this possibility, neurons were recorded across natural sleep–wake states in head-fixed rats and labeled by using the juxtacellular technique for subsequent immunohistochemical identification. Neurons identified as MCH+ did not fire during wake (W); they fired selectively during sleep, occasionally during slow wave sleep (SWS) and maximally during paradoxical sleep (PS). As W-Off/Sleep-On, the MCH neurons discharged in a reciprocal manner to the W-On/Sleep-Off Orx neurons and could accordingly play a complementary role to Orx neurons in sleep–wake state regulation and contribute to the pathophysiology of certain sleep disorders, such as narcolepsy with cataplexy. PMID:19188611

HuR (Elavl1) and HuB (Elavl2) Stabilize Matrix Metalloproteinase-9 mRNA During Seizure-Induced Mmp-9 Expression in Neurons

PubMed Central

Zybura-Broda, Katarzyna; Wolder-Gontarek, Malgorzata; Ambrozek-Latecka, Magdalena; Choros, Artur; Bogusz, Agnieszka; Wilemska-Dziaduszycka, Joanna; Rylski, Marcin

2018-01-01

Matrix metalloproteinase-9 (Mmp-9) is involved in different general and cell-type–specific processes, both in neuronal and non-neuronal cells. Moreover, it is implicated in an induction or progression of various human disorders, including diseases of the central nervous system. Mechanisms regulating activity-driven Mmp-9 expression in neurons are still not fully understood. Here, we show that stabilization of Mmp-9 mRNA is one of the factors responsible for the neuronal activity-evoked upregulation of Mmp-9 mRNA expression in hippocampal neurons. Furthermore, we demonstrate that the molecular mechanism related to this stabilization is dependent on the neuronal seizure-triggered transiently increased binding of the mRNA stability-inducing protein, HuR, to ARE1 and ARE4 motifs of the 3′UTR for Mmp-9 mRNA as well as the stably augmented association of another mRNA-stabilizing protein, HuB, to the ARE1 element of the 3′UTR. Intriguingly, we demonstrate further that both HuR and HuB are crucial for an incidence of Mmp-9 mRNA stabilization after neuronal activation. This study identifies Mmp-9 mRNA as the first HuB target regulated by mRNA stabilization in neurons. Moreover, these results are the first to describe an existence of HuR-dependent mRNA stabilization in neurons of the brain. PMID:29686606

An ATF4-ATG5 signaling in hypothalamic POMC neurons regulates obesity.

PubMed

Xiao, Yuzhong; Deng, Yalan; Yuan, Feixiang; Xia, Tingting; Liu, Hao; Li, Zhigang; Chen, Shanghai; Liu, Zhixue; Ying, Hao; Liu, Yi; Zhai, Qiwei; Guo, Feifan

2017-06-03

ATF4 (activating transcription factor 4) is an important transcription factor that has many biological functions, while its role in hypothalamic POMC (pro-opiomelanocortin-α) neurons in the regulation of energy homeostasis has not been explored. We recently discovered that mice with an Atf4 deletion specific to POMC neurons (PAKO mice) are lean and have higher energy expenditure. Furthermore, these mice are resistant to high-fat diet (HFD)-induced obesity and obesity-related metabolic disorders. Mechanistically, we found the expression of ATG5 (autophagy-related 5) is upregulated in POMC neurons of PAKO mice, and ATF4 regulates ATG5 expression by binding directly to its promoter. Mice with Atf4 and Atg5 double knockout in POMC neurons have reduced energy expenditure and gain more fat mass compared with PAKO mice under a HFD. Finally, the effect of Atf4 knockout in POMC neurons is possibly mediated by enhanced ATG5-dependent macroautophagy/autophagy and α-melanocyte-stimulating hormone (α-MSH) production in the hypothalamus. Together, this work not only identifies a beneficial role for ATF4 in hypothalamic POMC neurons in the regulation of obesity, but also provides a new potential therapeutic target for obesity and obesity-related metabolic diseases.

PTEN inhibition prevents rat cortical neuron injury after hypoxia-ischemia.

PubMed

Zhao, J; Qu, Y; Wu, J; Cao, M; Ferriero, D M; Zhang, L; Mu, D

2013-05-15

Alterations in axon-dendrite polarity impair functional recovery in the developing CNS after hypoxia-ischemia (HI) injury. PTEN (phosphatase and tensin homolog deleted on chromosome 10) signaling pathway mediates the formation of neuronal polarity. However, its role in cerebral HI injury is not fully understood. In this study, we investigated the role of PTEN pathway in regulation of axon-dendrite polarity using an oxygen-glucose deprivation (OGD) model with rat cortical neurons. We found that the activity of PTEN and glycogen synthase kinase 3β (GSK-3β) was increased after OGD, along with the decrease of the activity in protein kinase B (Akt) and collapsin response mediator protein-2 (CRMP-2). Pretreatment with bpv, a potent inhibitor of PTEN, caused a decrease of the activity in PTEN and GSK-3β, and a significant increase of the activity in Akt and CRMP-2. Simultaneously, the morphological polarity of neurons was maintained and neuronal apoptosis was reduced. Moreover, inhibition of PTEN rescued vesicle recycling in axons. These findings suggested that the PTEN/Akt/GSK-3β/CRMP-2 pathway is involved in the regulation of axon-dendrite polarity, providing a novel route for protecting neurons following neonatal HI. Copyright © 2013 IBRO. Published by Elsevier Ltd. All rights reserved.

I(2)(PP2A) regulates p53 and Akt correlatively and leads the neurons to abort apoptosis.

PubMed

Liu, Gong-Ping; Wei, Wei; Zhou, Xin; Zhang, Yao; Shi, Hai-Hong; Yin, Jun; Yao, Xiu-Qing; Peng, Cai-Xia; Hu, Juan; Wang, Qun; Li, Hong-Lian; Wang, Jian-Zhi

2012-02-01

A chronic neuron loss is the cardinal pathology in Alzheimer disease (AD), but it is still not understood why most neurons in AD brain do not accomplish apoptosis even though they are actually exposed to an environment with enriched proapoptotic factors. Protein phosphatase-2A inhibitor-2 (I(2)(PP2A)), an endogenous PP2A inhibitor, is significantly increased in AD brain, but the role of I(2)(PP2A) in AD-like neuron loss is elusive. Here, we show that I(2)(PP2A) regulates p53 and Akt correlatively. The mechanisms involve activated transcription and p38 MAPK activities. More importantly, we demonstrate that the simultaneous activation of Akt induced by I(2)(PP2A) counteracts the hyperactivated p53-induced cell apoptosis. Furthermore, I(2)(PP2A), p53 and Akt are all elevated in the brain of mouse model and AD patients. Our results suggest that the increased I(2)(PP2A) may trigger apoptosis by p53 upregulation, but due to simultaneous activation of Akt, the neurons are aborted from the apoptotic pathway. This finding contributes to the understanding of why most neurons in AD brain do not undergo apoptosis. Copyright © 2010. Published by Elsevier Inc.

The tumour suppressor protein, p53, is involved in the activation of the apoptotic cascade by Delta9-tetrahydrocannabinol in cultured cortical neurons.

PubMed

Downer, Eric J; Gowran, Aoife; Murphy, Aine C; Campbell, Veronica A

2007-06-14

Cannabis is the most commonly used illegal drug of abuse in Western society. Delta(9)-tetrahydrocannabinol, the psychoactive ingredient of marijuana, regulates a variety of neuronal processes including neurotransmitter release and synaptic transmission. An increasing body of evidence suggests that cannabinoids play a key role in the regulation of neuronal viability. In cortical neurons tetrahydrocannabinol has a neurodegenerative effect, the mechanisms of which are poorly understood, but involve the cannabinoid receptor subtype, CB(1). In this study we report that tetrahydrocannabinol (5 muM) evokes a rapid phosphorylation, and thus activation, of the tumour suppressor protein, p53, in a manner involving the cannabinoid CB(1) receptor, and the stress-activated protein kinase, c-jun N-terminal kinase, in cultured cortical neurons. Tetrahydrocannabinol increased expression of the p53-transcriptional target, Bax and promoted Bcl phosphorylation. These events were abolished by the p53 inhibitor, pifithrin-alpha (100 nM). The tetrahydrocannabinol-induced activation of the pro-apoptotic cysteine protease, caspase-3, and DNA fragmentation was also blocked by pifithrin-alpha. A siRNA knockdown of p53 further verified the role of p53 in tetrahydrocannabinol-induced apoptosis. This study demonstrates a novel cannabinoid signalling pathway involving p53 that culminates in neuronal apoptosis.

Naphthazarin protects against glutamate-induced neuronal death via activation of the Nrf2/ARE pathway

DOE Office of Scientific and Technical Information (OSTI.GOV)

Son, Tae Gen; Kawamoto, Elisa M.; Yu, Qian-Sheng

2013-04-19

Highlights: •Naphthazarin activates the Nrf2/ARE pathway. •Naphthazarin induces Nrf2-driven genes in neurons and astrocytes. •Naphthazarin protects neurons against excitotoxicity. -- Abstract: Nuclear factor E2-related factor 2 (Nrf2)/antioxidant response element (ARE) pathway is an important cellular stress response pathway involved in neuroprotection. We previously screened several natural phytochemicals and identified plumbagin as a novel activator of the Nrf2/ARE pathway that can protect neurons against ischemic injury. Here we extended our studies to natural and synthetic derivatives of plumbagin. We found that 5,8-dimethoxy-1,4-naphthoquinone (naphthazarin) is a potent activator of the Nrf2/ARE pathway, up-regulates the expression of Nrf2-driven genes in primary neuronal andmore » glial cultures, and protects neurons against glutamate-induced excitotoxicity.« less

Histone methyltransferase Ash1L mediates activity-dependent repression of neurexin-1α

PubMed Central

Zhu, Τao; Liang, Chen; Li, Dongdong; Tian, Miaomiao; Liu, Sanxiong; Gao, Guanjun; Guan, Ji-Song

2016-01-01

Activity-dependent transcription is critical for the regulation of long-term synaptic plasticity and plastic rewiring in the brain. Here, we report that the transcription of neurexin1α (nrxn1α), a presynaptic adhesion molecule for synaptic formation, is regulated by transient neuronal activation. We showed that 10 minutes of firing at 50 Hz in neurons repressed the expression of nrxn1α for 24 hours in a primary cortical neuron culture through a transcriptional repression mechanism. By performing a screening assay using a synthetic zinc finger protein (ZFP) to pull down the proteins enriched near the nrxn1α promoter region in vivo, we identified that Ash1L, a histone methyltransferase, is enriched in the nrxn1α promoter. Neuronal activity triggered binding of Ash1L to the promoter and enriched the histone marker H3K36me2 at the nrxn1α promoter region. Knockout of Ash1L in mice completely abolished the activity-dependent repression of nrxn1α. Taken together, our results reveal that a novel process of activity-dependent transcriptional repression exists in neurons and that Ash1L mediates the long-term repression of nrxn1α, thus implicating an important role for epigenetic modification in brain functioning. PMID:27229316

Increased Cell-Intrinsic Excitability Induces Synaptic Changes in New Neurons in the Adult Dentate Gyrus That Require Npas4

PubMed Central

Sim, Shuyin; Antolin, Salome; Lin, Chia-Wei; Lin, Ying-Xi

2013-01-01

Electrical activity regulates the manner in which neurons mature and form connections to each other. However, it remains unclear whether increased single-cell activity is sufficient to alter the development of synaptic connectivity of that neuron or whether a global increase in circuit activity is necessary. To address this question, we genetically increased neuronal excitability of in vivo individual adult-born neurons in the mouse dentate gyrus via expression of a voltage-gated bacterial sodium channel. We observed that increasing the excitability of new neurons in an otherwise unperturbed circuit leads to changes in both their input and axonal synapses. Furthermore, the activity-dependent transcription factor Npas4 is necessary for the changes in the input synapses of these neurons, but it is not involved in changes to their axonal synapses. Our results reveal that an increase in cell-intrinsic activity during maturation is sufficient to alter the synaptic connectivity of a neuron with the hippocampal circuit and that Npas4 is required for activity-dependent changes in input synapses. PMID:23637184

Pushing the threshold: How NMDAR antagonists induce homeostasis through protein synthesis to remedy depression.

PubMed

Raab-Graham, Kimberly F; Workman, Emily R; Namjoshi, Sanjeev; Niere, Farr

2016-09-15

Healthy neurons have an optimal operating range, coded globally by the frequency of action potentials or locally by calcium. The maintenance of this range is governed by homeostatic plasticity. Here, we discuss how new approaches to treat depression alter synaptic activity. These approaches induce the neuron to recruit homeostatic mechanisms to relieve depression. Homeostasis generally implies that the direction of activity necessary to restore the neuron's critical operating range is opposite in direction to its current activity pattern. Unconventional antidepressant therapies-deep brain stimulation and NMDAR antagonists-alter the neuron's "depressed" state by pushing the neuron's current activity in the same direction but to the extreme edge. These therapies rally the intrinsic drive of neurons in the opposite direction, thereby allowing the cell to return to baseline activity, form new synapses, and restore proper communication. In this review, we discuss seminal studies on protein synthesis dependent homeostatic plasticity and their contribution to our understanding of molecular mechanisms underlying the effectiveness of NMDAR antagonists as rapid antidepressants. Rapid antidepressant efficacy is likely to require a cascade of mRNA translational regulation. Emerging evidence suggests that changes in synaptic strength or intrinsic excitability converge on the same protein synthesis pathways, relieving depressive symptoms. Thus, we address the question: Are there multiple homeostatic mechanisms that induce the neuron and neuronal circuits to self-correct to regulate mood in vivo? Targeting alternative ways to induce homeostatic protein synthesis may provide, faster, safer, and longer lasting antidepressants. This article is part of a Special Issue entitled SI:RNA Metabolism in Disease. Published by Elsevier B.V.

The properties, distribution and function of Na+–Ca2+ exchanger isoforms in rat cutaneous sensory neurons

PubMed Central

Scheff, N N; Yilmaz, E; Gold, M S

2014-01-01

The Na+–Ca2+ exchanger (NCX) appears to play an important role in the regulation of the high K+-evoked Ca2+ transient in putative nociceptive dorsal root ganglion (DRG) neurons. The purpose of the present study was to (1) characterize the properties of NCX activity in subpopulations of DRG neurons, (2) identify the isoform(s) underlying NCX activity, and (3) begin to assess the function of the isoform(s) in vivo. In retrogradely labelled neurons from the glabrous skin of adult male Sprague–Dawley rats, NCX activity, as assessed with fura-2-based microfluorimetry, was only detected in putative nociceptive IB4+ neurons. There were two modes of NCX activity: one was evoked in response to relatively large and long lasting (∼325 nm for >12 s) increases in the concentration of intracellular Ca2+ ([Ca2+]i), and a second was active at resting [Ca2+]i > ∼150 nm. There also were two modes of evoked activity: one that decayed relatively rapidly (<5 min) and a second that persisted (>10 min). Whereas mRNA encoding all three NCX isoforms (NCX1–3) was detected in putative nociceptive cutaneous neurons with single cell PCR, pharmacological analysis and small interfering RNA (siRNA) knockdown of each isoform in vivo suggested that NCX2 and 3 were responsible for NCX activity. Western blot analyses suggested that NCX isoforms were differentially distributed within sensory neurons. Functional assays of excitability, action potential propagation, and nociceptive behaviour suggest NCX activity has little influence on excitability per se, but instead influences axonal conduction velocity, resting membrane potential, and nociceptive threshold. Together these results indicate that the function of NCX in the regulation of [Ca2+]i in putative nociceptive neurons may be unique relative to other cells in which these exchanger isoforms have been characterized and it has the potential to influence sensory neuron properties at multiple levels. PMID:25239455

Control of the neurovascular coupling by nitric oxide-dependent regulation of astrocytic Ca2+ signaling

PubMed Central

Muñoz, Manuel F.; Puebla, Mariela; Figueroa, Xavier F.

2015-01-01

Neuronal activity must be tightly coordinated with blood flow to keep proper brain function, which is achieved by a mechanism known as neurovascular coupling. Then, an increase in synaptic activity leads to a dilation of local parenchymal arterioles that matches the enhanced metabolic demand. Neurovascular coupling is orchestrated by astrocytes. These glial cells are located between neurons and the microvasculature, with the astrocytic endfeet ensheathing the vessels, which allows fine intercellular communication. The neurotransmitters released during neuronal activity reach astrocytic receptors and trigger a Ca2+ signaling that propagates to the endfeet, activating the release of vasoactive factors and arteriolar dilation. The astrocyte Ca2+ signaling is coordinated by gap junction channels and hemichannels formed by connexins (Cx43 and Cx30) and channels formed by pannexins (Panx-1). The neuronal activity-initiated Ca2+ waves are propagated among neighboring astrocytes directly via gap junctions or through ATP release via connexin hemichannels or pannexin channels. In addition, Ca2+ entry via connexin hemichannels or pannexin channels may participate in the regulation of the astrocyte signaling-mediated neurovascular coupling. Interestingly, nitric oxide (NO) can activate connexin hemichannel by S-nitrosylation and the Ca2+-dependent NO-synthesizing enzymes endothelial NO synthase (eNOS) and neuronal NOS (nNOS) are expressed in astrocytes. Therefore, the astrocytic Ca2+ signaling triggered in neurovascular coupling may activate NO production, which, in turn, may lead to Ca2+ influx through hemichannel activation. Furthermore, NO release from the hemichannels located at astrocytic endfeet may contribute to the vasodilation of parenchymal arterioles. In this review, we discuss the mechanisms involved in the regulation of the astrocytic Ca2+ signaling that mediates neurovascular coupling, with a special emphasis in the possible participation of NO in this process. PMID:25805969

Locomotor- and Reward-Enhancing Effects of Cocaine Are Differentially Regulated by Chemogenetic Stimulation of Gi-Signaling in Dopaminergic Neurons.

PubMed

Runegaard, Annika H; Sørensen, Andreas T; Fitzpatrick, Ciarán M; Jørgensen, Søren H; Petersen, Anders V; Hansen, Nikolaj W; Weikop, Pia; Andreasen, Jesper T; Mikkelsen, Jens D; Perrier, Jean-Francois; Woldbye, David; Rickhag, Mattias; Wortwein, Gitta; Gether, Ulrik

2018-01-01

Dopamine plays a key role in the cellular and behavioral responses to drugs of abuse, but the implication of metabotropic regulatory input to dopaminergic neurons on acute drug effects and subsequent drug-related behavior remains unclear. Here, we used chemogenetics [Designer Receptors Exclusively Activated by Designer Drugs (DREADDs)] to modulate dopamine signaling and activity before cocaine administration in mice. We show that chemogenetic inhibition of dopaminergic ventral tegmental area (VTA) neurons differentially affects locomotor and reward-related behavioral responses to cocaine. Stimulation of Gi-coupled DREADD (hM4Di) expressed in dopaminergic VTA neurons persistently reduced the locomotor response to repeated cocaine injections. An attenuated locomotor response was seen even when a dual-viral vector approach was used to restrict hM4Di expression to dopaminergic VTA neurons projecting to the nucleus accumbens. Surprisingly, despite the attenuated locomotor response, hM4Di-mediated inhibition of dopaminergic VTA neurons did not prevent cocaine sensitization, and the inhibitory effect of hM4Di-mediated inhibition was eliminated after withdrawal. In the conditioned place-preference paradigm, hM4Di-mediated inhibition did not affect cocaine-induced place preference; however, the extinction period was extended. Also, hM4Di-mediated inhibition had no effect on preference for a sugar-based reward over water but impaired motivation to work for the same reward in a touchscreen-based motivational assay. In addition, to support that VTA dopaminergic neurons operate as regulators of reward motivation toward both sugar and cocaine, our data suggest that repeated cocaine exposure leads to adaptations in the VTA that surmount the ability of Gi-signaling to suppress and regulate VTA dopaminergic neuronal activity.

Drp1 levels constitutively regulate mitochondrial dynamics and cell survival in cortical neurons.

PubMed

Uo, Takuma; Dworzak, Jenny; Kinoshita, Chizuru; Inman, Denise M; Kinoshita, Yoshito; Horner, Philip J; Morrison, Richard S

2009-08-01

Mitochondria exist as dynamic networks that are constantly remodeled through the opposing actions of fusion and fission proteins. Changes in the expression of these proteins alter mitochondrial shape and size, and may promote or inhibit the propagation of apoptotic signals. Using mitochondrially targeted EGFP or DsRed2 to identify mitochondria, we observed a short, distinctly tubular mitochondrial morphology in postnatal cortical neurons in culture and in retinal ganglion cells in vivo, whereas longer, highly interconnected mitochondrial networks were detected in cortical astrocytes in vitro and non-neuronal cells in the retina in vivo. Differential expression patterns of fusion and fission proteins, in part, appear to determine these morphological differences as neurons expressed markedly high levels of Drp1 and OPA1 proteins compared to non-neuronal cells. This finding was corroborated using optic tissue samples. Moreover, cortical neurons expressed several splice variants of Drp1 including a neuron-specific isoform which incorporates exon 3. Knockdown or dominant-negative interference of endogenous Drp1 significantly increased mitochondrial length in both neurons and non-neuronal cells, but caused cell death only in cortical neurons. Conversely, depletion of the fusion protein, Mfn2, but not Mfn1, caused extensive mitochondrial fission and cell death. Thus, Drp1 and Mfn2 in normal cortical neurons not only regulate mitochondrial morphology, but are also required for cell survival. The present findings point to unique patterns of Drp1 expression and selective vulnerability to reduced levels of Drp1 expression/activity in neurons, and demonstrate that the regulation of mitochondrial dynamics must be tightly regulated in neurons.

Drp1 levels constitutively regulate mitochondrial dynamics and cell survival in cortical neurons

PubMed Central

Uo, Takuma; Dworzak, Jenny; Kinoshita, Chizuru; Inman, Denise M.; Kinoshita, Yoshito; Horner, Philip J.; Morrison, Richard S.

2009-01-01

Mitochondria exist as dynamic networks that are constantly remodeled through the opposing actions of fusion and fission proteins. Changes in the expression of these proteins alter mitochondrial shape and size, and may promote or inhibit the propagation of apoptotic signals. Using mitochondrially targeted EGFP or DsRed2 to identify mitochondria, we observed a short, distinctly tubular mitochondrial morphology in postnatal cortical neurons in culture and in retinal ganglion cells in vivo, whereas longer, highly interconnected mitochondrial networks were detected in cortical astrocytes in vitro and non-neuronal cells in the retina in vivo. Differential expression patterns of fusion and fission proteins, in part, appear to determine these morphological differences as neurons expressed markedly high levels of Drp1 and OPA1 proteins compared to non-neuronal cells. This finding was corroborated using optic tissue samples. Moreover, cortical neurons expressed several splice variants of Drp1 including a neuron-specific isoform which incorporates exon 3. Knockdown or dominant negative interference of endogenous Drp1 significantly increased mitochondrial length in both neurons and non-neuronal cells, but caused cell death only in cortical neurons. Conversely, depletion of the fusion protein, Mfn2, but not Mfn1, caused extensive mitochondrial fission and cell death. Thus, Drp1 and Mfn2 in normal cortical neurons not only regulate mitochondrial morphology, but are also required for cell survival. The present findings point to unique patterns of Drp1 expression and selective vulnerability to reduced levels of Drp1 expression/activity in neurons, and demonstrate that the regulation of mitochondrial dynamics must be tightly regulated in neurons. PMID:19445933

Matrix Metalloproteinase-9 regulates neuronal circuit development and excitability

PubMed Central

Murase, Sachiko; Lantz, Crystal; Kim, Eunyoung; Gupta, Nitin; Higgins, Richard; Stopfer, Mark; Hoffman, Dax A.; Quinlan, Elizabeth M.

2015-01-01

In early postnatal development, naturally occurring cell death, dendritic outgrowth and synaptogenesis sculpt neuronal ensembles into functional neuronal circuits. Here we demonstrate that deletion of the extracellular proteinase MMP-9 affects each of these processes, resulting in maladapted neuronal circuitry. MMP-9 deletion increases the number of CA1 pyramidal neurons, but decreases dendritic length and complexity while dendritic spine density is unchanged. Parallel changes in neuronal morphology are observed in primary visual cortex, and persist into adulthood. Individual CA1 neurons in MMP-9−/− mice have enhanced input resistance and a significant increase in the frequency, but not amplitude, of miniature excitatory postsynaptic currents (mEPSCs). Additionally, deletion of MMP-9 significant increases spontaneous neuronal activity in awake MMP-9−/− mice and enhances response to acute challenge by the excitotoxin kainate. Thus MMP-9-dependent proteolysis regulates several aspects of circuit maturation to constrain excitability throughout life. PMID:26093382

p62 modulates Akt activity via association with PKC{zeta} in neuronal survival and differentiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joung, Insil; Kim, Hak Jae; Kwon, Yunhee Kim

2005-08-26

p62 is a ubiquitously expressed phosphoprotein that interacts with a number of signaling molecules and a major component of neurofibrillary tangles in the brain of Alzheimer's disease patients. It has been implicated in important cellular functions such as cell proliferation and anti-apoptotic pathways. In this study, we have addressed the potential role of p62 during neuronal differentiation and survival using HiB5, a rat neuronal progenitor cell. We generated a recombinant adenovirus encoding T7-epitope tagged p62 to reliably transfer p62 cDNA into the neuronal cells. The results show that an overexpression of p62 led not only to neuronal differentiation, but alsomore » to decreased cell death induced by serum withdrawal in HiB5 cells. In this process p62-dependent Akt phosphorylation occurred via the release of Akt from PKC{zeta} by association of p62 and PKC{zeta}, which is known as a negative regulator of Akt activation. These findings indicate that p62 facilitates cell survival through novel signaling cascades that result in Akt activation. Furthermore, we found that p62 expression was induced during neuronal differentiation. Taken together, the data suggest p62 is a regulator of neuronal cell survival and differentiation.« less

Genetic activation, inactivation and deletion reveal a limited and nuanced role for somatostatin-containing basal forebrain neurons in behavioral state control.

PubMed

Anaclet, Christelle; De Luca, Roberto; Venner, Anne; Malyshevskaya, Olga; Lazarus, Michael; Arrigoni, Elda; Fuller, Patrick M

2018-05-07

Recent studies have identified an especially important role for basal forebrain GABAergic (BF VGAT ) neurons in the regulation of behavioral waking and fast cortical rhythms associated with cognition. However, BF VGAT neurons comprise several neurochemically and anatomically distinct sub-populations, including parvalbumin- and somatostatin-containing BF VGAT neurons (BF Parv and BF SOM ), and it was recently reported that optogenetic activation of BF SOM neurons increases the probability of a wakefulness to non-rapid-eye movement (NREM) sleep transition when stimulated during the animal's rest period. This finding was unexpected given that most BF SOM neurons are not NREM sleep active and that central administration of the synthetic SOM analog, octreotide, suppresses NREM sleep or increases REM sleep. Here we employed a combination of genetically-driven chemogenetic and optogenetic activation, chemogenetic inhibition and ablation approaches to further explore the in vivo role of BF SOM neurons in arousal control. Our findings indicate that acute activation or inhibition of BF SOM neurons is neither wakefulness- nor NREM sleep-promoting, is without significant effect on the EEG, and that chronic loss of these neurons is without effect on total 24h sleep amounts, although a small but significant increase in waking was observed in the lesioned mice during the early active period. Our in vitro cell recordings further reveal electrophysiological heterogeneity in BF SOM neurons, specifically suggesting at least two distinct sub-populations. Taken together our data support the more nuanced view that BF SOM are electrically heterogeneous and are not NREM sleep- or wake-promoting per se , but may exert, in particular during the early active period, a modest inhibitory influence on arousal circuitry. SIGNIFICANCE STATEMENT The cellular basal forebrain (BF) is a highly complex area of the brain that is implicated in a wide-range of higher-level neurobiological processes, including regulating and maintaining normal levels of electrocortical and behavioral arousal. The respective in vivo roles of BF cell populations and their neurotransmitter systems in the regulation of electrocortical and behavioral arousal remains incompletely understood. Here we seek to define the neurobiological contribution of GABAergic somatostanin-containing BF neurons to arousal control. Understanding the respective contribution of BF cell populations to arousal control may provide critical insight into the pathogenesis of a host of neuropsychiatric and neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, schizophrenia and the cognitive impairments of normal aging. Copyright © 2018 the authors.

Dual leucine zipper kinase-dependent PERK activation contributes to neuronal degeneration following insult

PubMed Central

Larhammar, Martin; Huntwork-Rodriguez, Sarah; Jiang, Zhiyu; Solanoy, Hilda; Sengupta Ghosh, Arundhati; Wang, Bei; Kaminker, Joshua S; Huang, Kevin; Eastham-Anderson, Jeffrey; Siu, Michael; Modrusan, Zora; Farley, Madeline M; Tessier-Lavigne, Marc; Lewcock, Joseph W; Watkins, Trent A

2017-01-01

The PKR-like endoplasmic reticulum kinase (PERK) arm of the Integrated Stress Response (ISR) is implicated in neurodegenerative disease, although the regulators and consequences of PERK activation following neuronal injury are poorly understood. Here we show that PERK signaling is a component of the mouse MAP kinase neuronal stress response controlled by the Dual Leucine Zipper Kinase (DLK) and contributes to DLK-mediated neurodegeneration. We find that DLK-activating insults ranging from nerve injury to neurotrophin deprivation result in both c-Jun N-terminal Kinase (JNK) signaling and the PERK- and ISR-dependent upregulation of the Activating Transcription Factor 4 (ATF4). Disruption of PERK signaling delays neurodegeneration without reducing JNK signaling. Furthermore, DLK is both sufficient for PERK activation and necessary for engaging the ISR subsequent to JNK-mediated retrograde injury signaling. These findings identify DLK as a central regulator of not only JNK but also PERK stress signaling in neurons, with both pathways contributing to neurodegeneration. DOI: http://dx.doi.org/10.7554/eLife.20725.001 PMID:28440222

A hypothalamic circuit that controls body temperature.

PubMed

Zhao, Zheng-Dong; Yang, Wen Z; Gao, Cuicui; Fu, Xin; Zhang, Wen; Zhou, Qian; Chen, Wanpeng; Ni, Xinyan; Lin, Jun-Kai; Yang, Juan; Xu, Xiao-Hong; Shen, Wei L

2017-02-21

The homeostatic control of body temperature is essential for survival in mammals and is known to be regulated in part by temperature-sensitive neurons in the hypothalamus. However, the specific neural pathways and corresponding neural populations have not been fully elucidated. To identify these pathways, we used cFos staining to identify neurons that are activated by a thermal challenge and found induced expression in subsets of neurons within the ventral part of the lateral preoptic nucleus (vLPO) and the dorsal part of the dorsomedial hypothalamus (DMD). Activation of GABAergic neurons in the vLPO using optogenetics reduced body temperature, along with a decrease in physical activity. Optogenetic inhibition of these neurons resulted in fever-level hyperthermia. These GABAergic neurons project from the vLPO to the DMD and optogenetic stimulation of the nerve terminals in the DMD also reduced body temperature and activity. Electrophysiological recording revealed that the vLPO GABAergic neurons suppressed neural activity in DMD neurons, and fiber photometry of calcium transients revealed that DMD neurons were activated by cold. Accordingly, activation of DMD neurons using designer receptors exclusively activated by designer drugs (DREADDs) or optogenetics increased body temperature with a strong increase in energy expenditure and activity. Finally, optogenetic inhibition of DMD neurons triggered hypothermia, similar to stimulation of the GABAergic neurons in the vLPO. Thus, vLPO GABAergic neurons suppressed the thermogenic effect of DMD neurons. In aggregate, our data identify vLPO→DMD neural pathways that reduce core temperature in response to a thermal challenge, and we show that outputs from the DMD can induce activity-induced thermogenesis.

Protein arginine methylation facilitates KCNQ channel-PIP2 interaction leading to seizure suppression

PubMed Central

Kim, Hyun-Ji; Jeong, Myong-Ho; Kim, Kyung-Ran; Jung, Chang-Yun; Lee, Seul-Yi; Kim, Hanna; Koh, Jewoo; Vuong, Tuan Anh; Jung, Seungmoon; Yang, Hyunwoo; Park, Su-Kyung; Choi, Dahee; Kim, Sung Hun; Kang, KyeongJin; Sohn, Jong-Woo; Park, Joo Min; Jeon, Daejong; Koo, Seung-Hoi; Ho, Won-Kyung; Kang, Jong-Sun; Kim, Seong-Tae; Cho, Hana

2016-01-01

KCNQ channels are critical determinants of neuronal excitability, thus emerging as a novel target of anti-epileptic drugs. To date, the mechanisms of KCNQ channel modulation have been mostly characterized to be inhibitory via Gq-coupled receptors, Ca2+/CaM, and protein kinase C. Here we demonstrate that methylation of KCNQ by protein arginine methyltransferase 1 (Prmt1) positively regulates KCNQ channel activity, thereby preventing neuronal hyperexcitability. Prmt1+/- mice exhibit epileptic seizures. Methylation of KCNQ2 channels at 4 arginine residues by Prmt1 enhances PIP2 binding, and Prmt1 depletion lowers PIP2 affinity of KCNQ2 channels and thereby the channel activities. Consistently, exogenous PIP2 addition to Prmt1+/- neurons restores KCNQ currents and neuronal excitability to the WT level. Collectively, we propose that Prmt1-dependent facilitation of KCNQ-PIP2 interaction underlies the positive regulation of KCNQ activity by arginine methylation, which may serve as a key target for prevention of neuronal hyperexcitability and seizures. DOI: http://dx.doi.org/10.7554/eLife.17159.001 PMID:27466704

Nesfatin-1-regulated oxytocinergic signaling in the paraventricular nucleus causes anorexia through a leptin-independent melanocortin pathway.

PubMed

Maejima, Yuko; Sedbazar, Udval; Suyama, Shigetomo; Kohno, Daisuke; Onaka, Tatsushi; Takano, Eisuke; Yoshida, Natsu; Koike, Masato; Uchiyama, Yasuo; Fujiwara, Ken; Yashiro, Takashi; Horvath, Tamas L; Dietrich, Marcelo O; Tanaka, Shigeyasu; Dezaki, Katsuya; Oh-I, Shinsuke; Hashimoto, Koushi; Shimizu, Hiroyuki; Nakata, Masanori; Mori, Masatomo; Yada, Toshihiko

2009-11-01

The hypothalamic paraventricular nucleus (PVN) functions as a center to integrate various neuronal activities for regulating feeding behavior. Nesfatin-1, a recently discovered anorectic molecule, is localized in the PVN. However, the anorectic neural pathway of nesfatin-1 remains unknown. Here we show that central injection of nesfatin-1 activates the PVN and brain stem nucleus tractus solitarius (NTS). In the PVN, nesfatin-1 targets both magnocellular and parvocellular oxytocin neurons and nesfatin-1 neurons themselves and stimulates oxytocin release. Immunoelectron micrographs reveal nesfatin-1 specifically in the secretory vesicles of PVN neurons, and immunoneutralization against endogenous nesfatin-1 suppresses oxytocin release in the PVN, suggesting paracrine/autocrine actions of nesfatin-1. Nesfatin-1-induced anorexia is abolished by an oxytocin receptor antagonist. Moreover, oxytocin terminals are closely associated with and oxytocin activates pro-opiomelanocortin neurons in the NTS. Oxytocin induces melanocortin-dependent anorexia in leptin-resistant Zucker-fatty rats. The present results reveal the nesfatin-1-operative oxytocinergic signaling in the PVN that triggers leptin-independent melanocortin-mediated anorexia.

In the loop: how chromatin topology links genome structure to function in mechanisms underlying learning and memory.

PubMed

Watson, L Ashley; Tsai, Li-Huei

2017-04-01

Different aspects of learning, memory, and cognition are regulated by epigenetic mechanisms such as covalent DNA modifications and histone post-translational modifications. More recently, the modulation of chromatin architecture and nuclear organization is emerging as a key factor in dynamic transcriptional regulation of the post-mitotic neuron. For instance, neuronal activity induces relocalization of gene loci to 'transcription factories', and specific enhancer-promoter looping contacts allow for precise transcriptional regulation. Moreover, neuronal activity-dependent DNA double-strand break formation in the promoter of immediate early genes appears to overcome topological constraints on transcription. Together, these findings point to a critical role for genome topology in integrating dynamic environmental signals to define precise spatiotemporal gene expression programs supporting cognitive processes. Copyright © 2016 Elsevier Ltd. All rights reserved.

Brain innate immunity regulates hypothalamic arcuate neuronal activity and feeding behavior.

PubMed

Reis, Wagner L; Yi, Chun-Xia; Gao, Yuanqing; Tschöp, Mathias H; Stern, Javier E

2015-04-01

Hypothalamic inflammation, involving microglia activation in the arcuate nucleus (ARC), is proposed as a novel underlying mechanism in obesity, insulin and leptin resistance. However, whether activated microglia affects ARC neuronal activity, and consequently basal and hormonal-induced food intake, is unknown. We show that lipopolysaccharide, an agonist of the toll-like receptor-4 (TLR4), which we found to be expressed in ARC microglia, inhibited the firing activity of the majority of orexigenic agouti gene-related protein/neuropeptide Y neurons, whereas it increased the activity of the majority of anorexigenic proopiomelanocortin neurons. Lipopolysaccharide effects in agouti gene-related protein/neuropeptide Y (but not in proopiomelanocortin) neurons were occluded by inhibiting microglia function or by blocking TLR4 receptors. Finally, we report that inhibition of hypothalamic microglia altered basal food intake, also preventing central orexigenic responses to ghrelin. Our studies support a major role for a TLR4-mediated microglia signaling pathway in the control of ARC neuronal activity and feeding behavior.

Channeling the Central Dogma.

PubMed

Calabrese, Ronald L

2014-05-21

How do neurons and networks achieve their characteristic electrical activity, regulate this activity homeostatically, and yet show population variability in expression? In this issue of Neuron, O'Leary et al. (2014) address some of these thorny questions in this theoretical analysis that starts with the Central Dogma. Copyright © 2014 Elsevier Inc. All rights reserved.

Bifurcation analysis of the regulation of nociceptive neuronal activity

NASA Astrophysics Data System (ADS)

Dik, O. E.

2017-11-01

A model of the membrane of a nociceptive neuron from a rat dorsal ganglion has been used to address the problem of analyzing the regulation of nociceptive signals by 5-hydroxy-γ-pyrone-2-carboxylic acid, which is the active pharmaceutic ingredient of the analgesic Anoceptin. The study has applied bifurcation analysis to report the relationship between the values of model parameters and the type of problem solution before and after the parameters change in response to analgesic modulation.

DCPIB, a potent volume-regulated anion channel antagonist, attenuates microglia-mediated inflammatory response and neuronal injury following focal cerebral ischemia.

PubMed

Han, Qingdong; Liu, Shengwen; Li, Zhengwei; Hu, Feng; Zhang, Qiang; Zhou, Min; Chen, Jingcao; Lei, Ting; Zhang, Huaqiu

2014-01-13

Accumulating evidence indicates that extensive microglia activation-mediated local inflammation contributes to neuronal injury in cerebral ischemia. We have previously shown that 4-(2-butyl-6, 7-dichloro-2-cyclopentyl-indan-1-on-5-yl) oxobutyric acid (DCPIB), a potent volume-regulated anion channel (VRAC) inhibitor, suppresses pathological glutamate release and excitatory neurotoxicity in reversible middle cerebral artery occlusion (rMCAO) model in vivo. In the present study, we sought to determine whether DCPIB also attenuates microglia activation that could contribute to neuronal injury in the cerebral ischemia/reperfusion pathology. We show that oxygen-glucose deprivation (OGD) induced microglia proliferation, migration, and secretion of cytokines and all these pathological changes were effectively inhibited by DCPIB in vitro. In the microglia/neuron co-cultures, OGD induced neuronal damage was reduced markedly in the presence of DCPIB. In rat rMCAO animal model, DCPIB significantly attenuated microglia activation and neuronal death. Activation of mitogen-activated protein kinase (MAPK) signaling pathway is known to be a critical signaling pathway for microglia activation. We further explored a potential involvement of DCPIB in this pathway by western blot analysis. Under the conditions that MAPK pathway was activated either by lipopolysaccharides (LPS) or OGD, the levels of phosphorylated ERK1/2, JNK and p38 were reduced significantly in the presence of DCPIB. Altogether, our study demonstrated that DCPIB inhibits microglia activation potently under ischemic conditions both in vitro and in vivo. The DCPIB effect is likely attributable to both direct inhibition VRAC and indirect inhibition of MAPK pathway in microglia that are beneficial for the survival of neurons in cerebral ischemic conditions. © 2013 Elsevier B.V. All rights reserved.

The dependence of neuronal encoding efficiency on Hebbian plasticity and homeostatic regulation of neurotransmitter release

PubMed Central

Faghihi, Faramarz; Moustafa, Ahmed A.

2015-01-01

Synapses act as information filters by different molecular mechanisms including retrograde messenger that affect neuronal spiking activity. One of the well-known effects of retrograde messenger in presynaptic neurons is a change of the probability of neurotransmitter release. Hebbian learning describe a strengthening of a synapse between a presynaptic input onto a postsynaptic neuron when both pre- and postsynaptic neurons are coactive. In this work, a theory of homeostatic regulation of neurotransmitter release by retrograde messenger and Hebbian plasticity in neuronal encoding is presented. Encoding efficiency was measured for different synaptic conditions. In order to gain high encoding efficiency, the spiking pattern of a neuron should be dependent on the intensity of the input and show low levels of noise. In this work, we represent spiking trains as zeros and ones (corresponding to non-spike or spike in a time bin, respectively) as words with length equal to three. Then the frequency of each word (here eight words) is measured using spiking trains. These frequencies are used to measure neuronal efficiency in different conditions and for different parameter values. Results show that neurons that have synapses acting as band-pass filters show the highest efficiency to encode their input when both Hebbian mechanism and homeostatic regulation of neurotransmitter release exist in synapses. Specifically, the integration of homeostatic regulation of feedback inhibition with Hebbian mechanism and homeostatic regulation of neurotransmitter release in the synapses leads to even higher efficiency when high stimulus intensity is presented to the neurons. However, neurons with synapses acting as high-pass filters show no remarkable increase in encoding efficiency for all simulated synaptic plasticity mechanisms. This study demonstrates the importance of cooperation of Hebbian mechanism with regulation of neurotransmitter release induced by rapid diffused retrograde messenger in neurons with synapses as low and band-pass filters to obtain high encoding efficiency in different environmental and physiological conditions. PMID:25972786

A Subset of Cholinergic Mushroom Body Neurons Requires Go Signaling to Regulate Sleep in Drosophila

PubMed Central

Yi, Wei; Zhang, Yunpeng; Tian, Yinjun; Guo, Jing; Li, Yan; Guo, Aike

2013-01-01

Study Objectives: Identifying the neurochemistry and neural circuitry of sleep regulation is critical for understanding sleep and various sleep disorders. Fruit flies display sleep-like behavior, sharing essential features with sleep of vertebrate. In the fruit fly's central brain, the mushroom body (MB) has been highlighted as a sleep center; however, its neurochemical nature remains unclear, and whether it promotes sleep or wake is still a topic of controversy. Design: We used a video recording system to accurately monitor the locomotor activity and sleep status. Gene expression was temporally and regionally manipulated by heat induction and the Gal4/UAS system. Measurements and Results: We found that expressing pertussis toxin (PTX) in the MB by c309-Gal4 to block Go activity led to unique sleep defects as dramatic sleep increase in daytime and fragmented sleep in nighttime. We narrowed down the c309-Gal4 expressing brain regions to the MB α/β core neurons that are responsible for the Go-mediated sleep effects. Using genetic tools of neurotransmitter-specific Gal80 and RNA interference approach to suppress acetylcholine signal, we demonstrated that these MB α/β core neurons were cholinergic and sleep-promoting neurons, supporting that Go mediates an inhibitory signal. Interestingly, we found that adjacent MB α/β neurons were also cholinergic but wake-promoting neurons, in which Go signal was also required. Conclusion: Our findings in fruit flies characterized a group of sleep-promoting neurons surrounded by a group of wake-promoting neurons. The two groups of neurons are both cholinergic and use Go inhibitory signal to regulate sleep. Citation: Yi W; Zhang Y; Tian Y; Guo J; Li Y; Guo A. A subset of cholinergic mushroom body neurons requires go signaling to regulate sleep in Drosophila. SLEEP 2013;36(12):1809-1821. PMID:24293755

FOXOs modulate proteasome activity in human-induced pluripotent stem cells of Huntington's disease and their derived neural cells.

PubMed

Liu, Yanying; Qiao, Fangfang; Leiferman, Patricia C; Ross, Alan; Schlenker, Evelyn H; Wang, Hongmin

2017-11-15

Although it has been speculated that proteasome dysfunction may contribute to the pathogenesis of Huntington's disease (HD), a devastating neurodegenerative disorder, how proteasome activity is regulated in HD affected stem cells and somatic cells remains largely unclear. To better understand the pathogenesis of HD, we analyzed proteasome activity and the expression of FOXO transcription factors in three wild-type (WT) and three HD induced-pluripotent stem cell (iPSC) lines. HD iPSCs exhibited elevated proteasome activity and higher levels of FOXO1 and FOXO4 proteins. Knockdown of FOXO4 but not FOXO1 expression decreased proteasome activity. Following neural differentiation, the HD-iPSC-derived neural progenitor cells (NPCs) demonstrated lower levels of proteasome activity and FOXO expressions than their WT counterparts. More importantly, overexpression of FOXO4 but not FOXO1 in HD NPCs dramatically enhanced proteasome activity. When HD NPCs were further differentiated into DARPP32-positive neurons, these HD neurons were more susceptible to death than WT neurons and formed Htt aggregates under the condition of oxidative stress. Similar to HD NPCs, HD-iPSC-derived neurons showed reduced proteasome activity and diminished FOXO4 expression compared to WT-iPSC-derived neurons. Furthermore, HD iPSCs had lower AKT activities than WT iPSCs, whereas the neurons derived from HD iPSC had higher AKT activities than their WT counterparts. Inhibiting AKT activity increased both FOXO4 level and proteasome activity, indicating a potential role of AKT in regulating FOXO levels. These data suggest that FOXOs modulate proteasome activity, and thus represents a potentially valuable therapeutic target for HD. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Regulating anxiety with extrasynaptic inhibition

PubMed Central

Botta, Paolo; Demmou, Lynda; Kasugai, Yu; Markovic, Milica; Xu, Chun; Fadok, Jonathan P.; Lu, Tingjia; Poe, Michael M.; Xu, Li; Cook, James M.; Rudolph, Uwe; Sah, Pankaj; Ferraguti, Francesco; Lüthi, Andreas

2015-01-01

Aversive experiences can lead to complex behavioral adaptations including increased levels of anxiety and fear generalization. The neuronal mechanisms underlying such maladaptive behavioral changes, however, are poorly understood. Here, using a combination of behavioral, physiological and optogenetic approaches in mouse, we identify a specific subpopulation of central amygdala neurons expressing protein kinase C δ (PKCδ) as key elements of the neuronal circuitry controlling anxiety. Moreover, we show that aversive experiences induce anxiety and fear generalization by regulating the activity of PKCδ+ neurons via extrasynaptic inhibition mediated by α5 subunit-containing GABAA receptors. Our findings reveal that the neuronal circuits that mediate fear and anxiety overlap at the level of defined subpopulations of central amygdala neurons and demonstrate that persistent changes in the excitability of a single cell type can orchestrate complex behavioral changes. PMID:26322928

PIKfyve mediates the motility of late endosomes and lysosomes in neuronal dendrites.

PubMed

Tsuruta, Fuminori; Dolmetsch, Ricardo E

2015-09-25

The endosome/lysosome system in the nervous system is critically important for a variety of neuronal functions such as neurite outgrowth, retrograde transport, and synaptic plasticity. In neurons, the endosome/lysosome system is crucial for the activity-dependent internalization of membrane proteins and contributes to the regulation of lipid level on the plasma membrane. Although homeostasis of membrane dynamics plays important roles in the properties of central nervous systems, it has not been elucidated how endosome/lysosome system is regulated. Here, we report that phosphatidylinositol 3-phosphate 5-kinase (PIKfyve) mediates the motility of late endosomes and lysosomes in neuronal dendrites. Endosomes and lysosomes are highly motile in resting neurons, however knockdown of PIKfyve led to a significant reduction in late endosomes and lysosomes motility. We also found that vesicle acidification is crucial for their motility and PIKfyve is associated with this process indirectly. These data suggest that PIKfyve mediates vesicle motility through the regulation of vesicle integrity in neurons. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

The role of PDF neurons in setting the preferred temperature before dawn in Drosophila.

PubMed

Tang, Xin; Roessingh, Sanne; Hayley, Sean E; Chu, Michelle L; Tanaka, Nobuaki K; Wolfgang, Werner; Song, Seongho; Stanewsky, Ralf; Hamada, Fumika N

2017-05-02

Animals have sophisticated homeostatic controls. While mammalian body temperature fluctuates throughout the day, small ectotherms, such as Drosophila achieve a body temperature rhythm (BTR) through their preference of environmental temperature. Here, we demonstrate that pigment dispersing factor (PDF) neurons play an important role in setting preferred temperature before dawn. We show that small lateral ventral neurons (sLNvs), a subset of PDF neurons, activate the dorsal neurons 2 (DN2s), the main circadian clock cells that regulate temperature preference rhythm (TPR). The number of temporal contacts between sLNvs and DN2s peak before dawn. Our data suggest that the thermosensory anterior cells (ACs) likely contact sLNvs via serotonin signaling. Together, the ACs-sLNs-DN2s neural circuit regulates the proper setting of temperature preference before dawn. Given that sLNvs are important for sleep and that BTR and sleep have a close temporal relationship, our data highlight a possible neuronal interaction between body temperature and sleep regulation.

Thrombospondin-4 divergently regulates voltage-gated Ca2+ channel subtypes in sensory neurons after nerve injury.

PubMed

Pan, Bin; Guo, Yuan; Wu, Hsiang-En; Park, John; Trinh, Van Nancy; Luo, Z David; Hogan, Quinn H

2016-09-01

Loss of high-voltage-activated (HVA) calcium current (ICa) and gain of low-voltage-activated (LVA) ICa after painful peripheral nerve injury cause elevated excitability in sensory neurons. Nerve injury is also accompanied by increased expression of the extracellular matrix glycoprotein thrombospondin-4 (TSP4), and interruption of TSP4 function can reverse or prevent behavioral hypersensitivity after injury. We therefore investigated TSP4 regulation of ICa in dorsal root ganglion (DRG) neurons. During depolarization adequate to activate HVA ICa, TSP4 decreases both N- and L-type ICa and the associated intracellular calcium transient. In contrast, TSP4 increases ICa and the intracellular calcium signal after low-voltage depolarization, which we confirmed is due to ICa through T-type channels. These effects are blocked by gabapentin, which ameliorates neuropathic pain by targeting the α2δ1 calcium subunit. Injury-induced changes of HVA and LVA ICa are attenuated in TSP4 knockout mice. In the neuropathic pain model of spinal nerve ligation, TSP4 application did not further regulate ICa of injured DRG neurons. Taken together, these findings suggest that elevated TSP4 after peripheral nerve injury may contribute to hypersensitivity of peripheral sensory systems by decreasing HVA and increasing LVA in DRG neurons by targeting the α2δ1 calcium subunit. Controlling TSP4 overexpression in peripheral sensory neurons may be a target for analgesic drug development for neuropathic pain.

Melatonin-mediated β-catenin activation protects neuron cells against prion protein-induced neurotoxicity.

PubMed

Jeong, Jae-Kyo; Lee, Ju-Hee; Moon, Ji-Hong; Lee, You-Jin; Park, Sang-Youel

2014-11-01

Activation of β-catenin in neurons regulates mitochondrial function and protects against protein misfolding disorders, including Alzheimer's disease and Huntington's disease. Melatonin, a natural secretory product of the pineal gland, exerts neuroprotective effects through the activation of β-catenin. In this study, melatonin increased β-catenin protein expression and activation in human neuroblastoma cell lines SH-SY5Y cells. Melatonin also inhibited PrP (106-126)-induced neurotoxicity and the inhibition attenuated by treatment of β-catenin inhibitor ICG-001. Activation of β-catenin blocked PrP (106-126)-mediated downregulation of anti-apoptotic protein survivin and Bcl-2. Reduction of mitochondrial membrane potential, translocation of Bax, and cytochrome c release which induced by PrP (106-126) treatment were inhibited by β-catenin activation, which contributed to prevented PrP (106-126)-induced neuronal cell death. In conclusion, β-catenin activation by melatonin prevented PrP (106-126)-induced neuronal cell death through regulating anti-apoptotic proteins and mitochondrial pathways. These results also suggest the therapeutic value of Wnt/β-catenin signaling in prion-related disorders as influenced by melatonin. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Serotonin neurons in the dorsal raphe mediate the anticataplectic action of orexin neurons by reducing amygdala activity.

PubMed

Hasegawa, Emi; Maejima, Takashi; Yoshida, Takayuki; Masseck, Olivia A; Herlitze, Stefan; Yoshioka, Mitsuhiro; Sakurai, Takeshi; Mieda, Michihiro

2017-04-25

Narcolepsy is a sleep disorder caused by the loss of orexin (hypocretin)-producing neurons and marked by excessive daytime sleepiness and a sudden weakening of muscle tone, or cataplexy, often triggered by strong emotions. In a mouse model for narcolepsy, we previously demonstrated that serotonin neurons of the dorsal raphe nucleus (DRN) mediate the suppression of cataplexy-like episodes (CLEs) by orexin neurons. Using an optogenetic tool, in this paper we show that the acute activation of DRN serotonin neuron terminals in the amygdala, but not in nuclei involved in regulating rapid eye-movement sleep and atonia, suppressed CLEs. Not only did stimulating serotonin nerve terminals reduce amygdala activity, but the chemogenetic inhibition of the amygdala using designer receptors exclusively activated by designer drugs also drastically decreased CLEs, whereas chemogenetic activation increased them. Moreover, the optogenetic inhibition of serotonin nerve terminals in the amygdala blocked the anticataplectic effects of orexin signaling in DRN serotonin neurons. Taken together, the results suggest that DRN serotonin neurons, as a downstream target of orexin neurons, inhibit cataplexy by reducing the activity of amygdala as a center for emotional processing.

Serotonin neurons in the dorsal raphe mediate the anticataplectic action of orexin neurons by reducing amygdala activity

PubMed Central

Hasegawa, Emi; Maejima, Takashi; Yoshida, Takayuki; Herlitze, Stefan; Yoshioka, Mitsuhiro; Sakurai, Takeshi; Mieda, Michihiro

2017-01-01

Narcolepsy is a sleep disorder caused by the loss of orexin (hypocretin)-producing neurons and marked by excessive daytime sleepiness and a sudden weakening of muscle tone, or cataplexy, often triggered by strong emotions. In a mouse model for narcolepsy, we previously demonstrated that serotonin neurons of the dorsal raphe nucleus (DRN) mediate the suppression of cataplexy-like episodes (CLEs) by orexin neurons. Using an optogenetic tool, in this paper we show that the acute activation of DRN serotonin neuron terminals in the amygdala, but not in nuclei involved in regulating rapid eye-movement sleep and atonia, suppressed CLEs. Not only did stimulating serotonin nerve terminals reduce amygdala activity, but the chemogenetic inhibition of the amygdala using designer receptors exclusively activated by designer drugs also drastically decreased CLEs, whereas chemogenetic activation increased them. Moreover, the optogenetic inhibition of serotonin nerve terminals in the amygdala blocked the anticataplectic effects of orexin signaling in DRN serotonin neurons. Taken together, the results suggest that DRN serotonin neurons, as a downstream target of orexin neurons, inhibit cataplexy by reducing the activity of amygdala as a center for emotional processing. PMID:28396432

Aldosterone-Sensing Neurons in the NTS Exhibit State-Dependent Pacemaker Activity and Drive Sodium Appetite via Synergy with Angiotensin II Signaling.

PubMed

Resch, Jon M; Fenselau, Henning; Madara, Joseph C; Wu, Chen; Campbell, John N; Lyubetskaya, Anna; Dawes, Brian A; Tsai, Linus T; Li, Monica M; Livneh, Yoav; Ke, Qingen; Kang, Peter M; Fejes-Tóth, Géza; Náray-Fejes-Tóth, Anikó; Geerling, Joel C; Lowell, Bradford B

2017-09-27

Sodium deficiency increases angiotensin II (ATII) and aldosterone, which synergistically stimulate sodium retention and consumption. Recently, ATII-responsive neurons in the subfornical organ (SFO) and aldosterone-sensitive neurons in the nucleus of the solitary tract (NTS HSD2 neurons) were shown to drive sodium appetite. Here we investigate the basis for NTS HSD2 neuron activation, identify the circuit by which NTS HSD2 neurons drive appetite, and uncover an interaction between the NTS HSD2 circuit and ATII signaling. NTS HSD2 neurons respond to sodium deficiency with spontaneous pacemaker-like activity-the consequence of "cardiac" HCN and Na v 1.5 channels. Remarkably, NTS HSD2 neurons are necessary for sodium appetite, and with concurrent ATII signaling their activity is sufficient to produce rapid consumption. Importantly, NTS HSD2 neurons stimulate appetite via projections to the vlBNST, which is also the effector site for ATII-responsive SFO neurons. The interaction between angiotensin signaling and NTS HSD2 neurons provides a neuronal context for the long-standing "synergy hypothesis" of sodium appetite regulation. Copyright © 2017 Elsevier Inc. All rights reserved.

Neurosteroid biosynthesis: enzymatic pathways and neuroendocrine regulation by neurotransmitters and neuropeptides.

PubMed

Do Rego, Jean Luc; Seong, Jae Young; Burel, Delphine; Leprince, Jerôme; Luu-The, Van; Tsutsui, Kazuyoshi; Tonon, Marie-Christine; Pelletier, Georges; Vaudry, Hubert

2009-08-01

Neuroactive steroids synthesized in neuronal tissue, referred to as neurosteroids, are implicated in proliferation, differentiation, activity and survival of nerve cells. Neurosteroids are also involved in the control of a number of behavioral, neuroendocrine and metabolic processes such as regulation of food intake, locomotor activity, sexual activity, aggressiveness, anxiety, depression, body temperature and blood pressure. In this article, we summarize the current knowledge regarding the existence, neuroanatomical distribution and biological activity of the enzymes responsible for the biosynthesis of neurosteroids in the brain of vertebrates, and we review the neuronal mechanisms that control the activity of these enzymes. The observation that the activity of key steroidogenic enzymes is finely tuned by various neurotransmitters and neuropeptides strongly suggests that some of the central effects of these neuromodulators may be mediated via the regulation of neurosteroid production.

Synaptophysin regulates the kinetics of synaptic vesicle endocytosis in central neurons

PubMed Central

Kwon, Sung E.; Chapman, Edwin R.

2011-01-01

Summary Despite being the most abundant synaptic vesicle membrane protein, the function of synaptophysin remains enigmatic. For example, synaptic transmission was reported to be completely normal in synaptophysin knockout mice; however, direct experiments to monitor the synaptic vesicle cycle have not been carried out. Here, using optical imaging and electrophysiological experiments, we demonstrate that synaptophysin is required for kinetically efficient endocytosis of synaptic vesicles in cultured hippocampal neurons. Truncation analysis revealed that distinct structural elements of synaptophysin differentially regulate vesicle retrieval during and after stimulation. Thus, synaptophysin regulates at least two phases of endocytosis to ensure vesicle availability during and after sustained neuronal activity. PMID:21658579

Electrophysical properties, synaptic transmission and neuromodulation in serotonergic caudal raphe neurons.

PubMed

Li, Y W; Bayliss, D A

1998-06-01

1. We studied electrophysiological properties, synaptic transmission and modulation by 5-hydroxytryptamine (5-HT) of caudal raphe neurons using whole-cell recording in a neonatal rat brain slice preparation; recorded neurons were identified as serotonergic by post-hoc immunohistochemical detection of tryptophan hydroxylase, the 5-HT-synthesizing enzyme. 2. Serotonergic neurons fired spontaneously (approximately 1 Hz), with maximal steady state firing rates of < 4 Hz. 5-Hydroxytryptamine caused hyperpolarization and cessation of spike activity in these neurons by activating inwardly rectifying K+ conductance via somatodendritic 5-HT1A receptors. 3. Unitary glutamatergic excitatory post-synaptic potentials (EPSP) and currents (EPSC) were evoked in serotonergic neurons by local electrical stimulation. Evoked EPSC were potently inhibited by 5-HT, an effect mediated by presynaptic 5-HT1B receptors. 4. In conclusion, serotonergic caudal raphe neurons are spontaneously active in vitro; they receive prominent glutamatergic synaptic inputs. 5-Hydroxytryptamine regulates serotonergic neuronal activity of the caudal raphe by decreasing spontaneous activity via somatodendritic 5-HT1A receptors and by inhibiting excitatory synaptic transmission onto these neurons via presynaptic 5-HT1B receptors. These local modulatory mechanisms provide multiple levels of feedback autoregulation of serotonergic raphe neurons by 5-HT.

Kisspeptin Signaling in the Brain

PubMed Central

Oakley, Amy E.; Clifton, Donald K.; Steiner, Robert A.

2009-01-01

Kisspeptin (a product of the Kiss1 gene) and its receptor (GPR54 or Kiss1r) have emerged as key players in the regulation of reproduction. Mutations in humans or genetically targeted deletions in mice of either Kiss1 or Kiss1r cause profound hypogonadotropic hypogonadism. Neurons that express Kiss1/kisspeptin are found in discrete nuclei in the hypothalamus, as well as other brain regions in many vertebrates, and their distribution, regulation, and function varies widely across species. Kisspeptin neurons directly innervate and stimulate GnRH neurons, which are the final common pathway through which the brain regulates reproduction. Kisspeptin neurons are sexually differentiated with respect to cell number and transcriptional activity in certain brain nuclei, and some kisspeptin neurons express other cotransmitters, including dynorphin and neurokinin B (whose physiological significance is unknown). Kisspeptin neurons express the estrogen receptor and the androgen receptor, and these cells are direct targets for the action of gonadal steroids in both male and female animals. Kisspeptin signaling in the brain has been implicated in mediating the negative feedback action of sex steroids on gonadotropin secretion, generating the preovulatory GnRH/LH surge, triggering and guiding the tempo of sexual maturation at puberty, controlling seasonal reproduction, and restraining reproductive activity during lactation. Kisspeptin signaling may also serve diverse functions outside of the classical realm of reproductive neuroendocrinology, including the regulation of metastasis in certain cancers, vascular dynamics, placental physiology, and perhaps even higher-order brain function. PMID:19770291

Dynamic change of SGK expression and its role in neuron apoptosis after traumatic brain injury.

PubMed

Wu, Xinmin; Mao, Hui; Liu, Jiao; Xu, Jian; Cao, Jianhua; Gu, Xingxing; Cui, Gang

2013-01-01

Activation of specific signaling pathways in response to mechanical trauma causes delayed neuronal apoptosis; GSK-3β/β-catenin signaling plays a critical role in the apoptosis of neurons in CNS diseases, SGK was discovered as a regulator of GSK-3β/β-catenin pathway, The goal of this study was to determine if the mechanism of cell death or survival mediated by the SGK/GSK-3β/β-catenin pathway is involved in a rat model of TBI. Here, an acute traumatic brain injury model was applied to investigate the expression change and possible roles of SGK, Expression of SGK, and total-GSK-3β, phospho-GSK3β on ser-9, beta-catenin, and caspase-3 were examined by immunohistochemistry and Western blot analysis. Double immunofluorescent staining was used to observe the SGK localizations. Si-RNA was performed to identify whether SGK regulates neuron apoptosis via GSK-3β/β-catenin pathway, ultimately inhibit caspase-3 activation. Temporally, SGK expression showed an increase pattern after TBI and reached a peak at day 3. Spatially, SGK was widely expressed in the neuron, rarely in astrocytes and oligodendrocytes; in addition, the expression patterns of active caspase-3 and phospho-GSK3β were parallel with that of SGK, at the same time, the expression of β-catenin shows similarity with SGK. In vitro, to further investigate the function of SGK, a neuronal cell line PC12 was employed to establish an apoptosis model. We analyzed the association of SGK with apoptosis on PC12 cells by western blot, immunofluorescent labeling and siRNA. the results implied that SGK plays an important role in neuron apoptosis via the regulation of GSK3β/β-catenin signaling pathway; ultimately inhibit caspase-3 activation. Taken together, we inferred traumatic brain injury induced an upregulation of SGK in the central nervous system, which show a protective role in neuron apoptosis.

Deletion of the Kv2.1 delayed rectifier potassium channel leads to neuronal and behavioral hyperexcitability

PubMed Central

Speca, David J.; Ogata, Genki; Mandikian, Danielle; Bishop, Hannah I.; Wiler, Steve W.; Eum, Kenneth; Wenzel, H. Jürgen; Doisy, Emily T.; Matt, Lucas; Campi, Katharine L.; Golub, Mari S.; Nerbonne, Jeanne M.; Hell, Johannes W.; Trainor, Brian C.; Sack, Jon T.; Schwartzkroin, Philip A.; Trimmer, James S.

2014-01-01

The Kv2.1 delayed rectifier potassium channel exhibits high-level expression in both principal and inhibitory neurons throughout the central nervous system, including prominent expression in hippocampal neurons. Studies of in vitro preparations suggest that Kv2.1 is a key yet conditional regulator of intrinsic neuronal excitability, mediated by changes in Kv2.1 expression, localization and function via activity-dependent regulation of Kv2.1 phosphorylation. Here we identify neurological and behavioral deficits in mutant (Kv2.1−/−) mice lacking this channel. Kv2.1−/− mice have grossly normal characteristics. No impairment in vision or motor coordination was apparent, although Kv2.1−/− mice exhibit reduced body weight. The anatomic structure and expression of related Kv channels in the brains of Kv2.1−/− mice appears unchanged. Delayed rectifier potassium current is diminished in hippocampal neurons cultured from Kv2.1−/− animals. Field recordings from hippocampal slices of Kv2.1−/− mice reveal hyperexcitability in response to the convulsant bicuculline, and epileptiform activity in response to stimulation. In Kv2.1−/− mice, long-term potentiation at the Schaffer collateral – CA1 synapse is decreased. Kv2.1−/− mice are strikingly hyperactive, and exhibit defects in spatial learning, failing to improve performance in a Morris Water Maze task. Kv2.1−/− mice are hypersensitive to the effects of the convulsants flurothyl and pilocarpine, consistent with a role for Kv2.1 as a conditional suppressor of neuronal activity. Although not prone to spontaneous seizures, Kv2.1−/− mice exhibit accelerated seizure progression. Together, these findings suggest homeostatic suppression of elevated neuronal activity by Kv2.1 plays a central role in regulating neuronal network function. PMID:24494598

The anatomical, cellular and synaptic basis of motor atonia during rapid eye movement sleep

PubMed Central

Chen, Michael C.

2016-01-01

Abstract Rapid eye movement (REM) sleep is a recurring part of the sleep–wake cycle characterized by fast, desynchronized rhythms in the electroencephalogram (EEG), hippocampal theta activity, rapid eye movements, autonomic activation and loss of postural muscle tone (atonia). The brain circuitry governing REM sleep is located in the pontine and medullary brainstem and includes ascending and descending projections that regulate the EEG and motor components of REM sleep. The descending signal for postural muscle atonia during REM sleep is thought to originate from glutamatergic neurons of the sublaterodorsal nucleus (SLD), which in turn activate glycinergic pre‐motor neurons in the spinal cord and/or ventromedial medulla to inhibit motor neurons. Despite work over the past two decades on many neurotransmitter systems that regulate the SLD, gaps remain in our knowledge of the synaptic basis by which SLD REM neurons are regulated and in turn produce REM sleep atonia. Elucidating the anatomical, cellular and synaptic basis of REM sleep atonia control is a critical step for treating many sleep‐related disorders including obstructive sleep apnoea (apnea), REM sleep behaviour disorder (RBD) and narcolepsy with cataplexy. PMID:27060683

Cerebral activation of mitogen-activated protein kinases after circulatory arrest and low flow cardiopulmonary bypass.

PubMed

Aharon, Alon S; Mulloy, Matthew R; Drinkwater, Davis C; Lao, Oliver B; Johnson, Mahlon D; Thunder, Megan; Yu, Chang; Chang, Paul

2004-11-01

Mitogen-activated protein kinases (MAPK) are important intermediates in the signal transduction pathways involved in neuronal dysfunction following cerebral ischemia-reperfusion injury. One subfamily, extracellular regulated kinase 1/2, has been heavily implicated in the pathogenesis of post-ischemic neuronal damage. However, the contribution of extracellular regulated kinase 1/2 to neuronal damage following deep hypothermic circulatory arrest and low flow cardiopulmonary bypass is unknown. We attempted to correlate the extent of neuronal damage present following deep hypothermic circulatory arrest and low flow cardiopulmonary bypass with phosphorylated extracellular regulated kinase 1/2 expression in the cerebral vascular endothelium. Piglets underwent normal flow cardiopulmonary bypass (n=4) deep hypothermic circulatory arrest (n=6) and low flow cardiopulmonary bypass (n=5). Brains were harvested following 24 h of post-cardiopulmonary bypass recovery. Cerebral cortical watershed zones, hippocampus, basal ganglia, thalamus, cerebellum, mesencephalon, pons and medulla were evaluated using hematoxylin and eosin staining. A section of ischemic cortex was evaluated by immunohistochemistry with rabbit polyclonal antibodies against phosphorylated extracellular regulated kinase 1/2. Compared to cardiopulmonary bypass controls, the deep hypothermic circulatory arrest and low flow cardiopulmonary bypass piglets exhibited diffuse ischemic changes with overlapping severity and distribution. Significant neuronal damage occurred in the frontal watershed zones and basal ganglia of the deep hypothermic circulatory arrest group (P<0.05). No detectable phosphorylated extracellular regulated kinase 1/2 immunoreactivity was found in the cardiopulmonary bypass controls; however, ERK 1/2 immunoreactivity was present in the cerebral vascular endothelium of the deep hypothermic circulatory arrest and low flow cardiopulmonary bypass groups. Our results indicate that phosphorylated extracellular regulated kinase 1/2 may play a prominent role in early cerebral ischemia-reperfusion injury and endothelial dysfunction. The pharmacologic inhibition of extracellular regulated kinase 1/2 represents a new and exciting opportunity for the modulation of cerebral tolerance to low flow cardiopulmonary bypass and deep hypothermic circulatory arrest.

Administration of IL-1β to the 4th ventricle causes anorexia that is blocked by agouti-related peptide and that coincides with activation of tyrosine-hydroxylase neurons in the nucleus of the solitary tract

PubMed Central

DeBoer, Mark D.; Scarlett, Jarrad M.; Levasseur, Peter R.; Grant, Wilmon F.; Marks, Daniel L.

2010-01-01

Inflammation-associated cachexia is associated with multiple chronic diseases and involves activation of appetite regulating centers in the arcuate nucleus of the hypothalamus (ARH). The nucleus of the solitary tract (NTS) in the brainstem has also been implicated as an important nucleus involved in appetite regulation. We set out to determine whether the NTS may be involved in inflammation-associated anorexia by injecting IL-1β into the 4th ventricle and assessing food intake and NTS neuronal activation. Injection of IL-1β produced a decrease in food intake at 3 and 12 h after injection which was ameliorated at the 12 h time point by a sub-threshold dose of agouti-related peptide (AgRP). Investigation into neuron types in the NTS revealed that IL-1β injection was associated with an increase in c-Fos activity in NTS neurons expressing tyrosine hydroxylase (TH). Additionally, injection of IL-1β into the 4th ventricle did not produce c-Fos activation of neurons expressing pro-opiomelanocortin (POMC) in the ARH, cells known to be involved in producing anorexia in response to systemic inflammation. Double-label in situ hybridization revealed that TH neurons did not express IL-1 receptor I (IL1-RI) transcript, demonstrating that c-Fos activation of TH neurons in this setting was not via direct stimulation of IL-1β on TH neurons themselves. We conclude that IL-1β injection into the 4th ventricle produces anorexia and is accompanied by an increase in activation in TH neurons in the NTS. This provides evidence that the brainstem may be an important mediator of anorexia in the setting of inflammation. PMID:19028534

Food for thought: Impact of metabolism on neuronal excitability.

PubMed

Katsu-Jiménez, Yurika; Alves, Renato M P; Giménez-Cassina, Alfredo

2017-11-01

Neuronal excitability is a highly demanding process that requires high amounts of energy and needs to be exquisitely regulated. For this reason, brain cells display active energy metabolism to support their activity. Independently of their roles as energy substrates, compelling evidence shows that the nature of the fuels that neurons use contribute to fine-tune neuronal excitability. Crosstalk of neurons with glial populations also plays a prominent role in shaping metabolic flow in the brain. In this review, we provide an overview on how different carbon substrates and metabolic pathways impact neurotransmission, and the potential implications for neurological disorders in which neuronal excitability is deregulated, such as epilepsy. Copyright © 2017 Elsevier Inc. All rights reserved.

Baclofen mediates neuroprotection on hippocampal CA1 pyramidal cells through the regulation of autophagy under chronic cerebral hypoperfusion

PubMed Central

Liu, Li; Li, Chang-jun; Lu, Yun; Zong, Xian-gang; Luo, Chao; Sun, Jun; Guo, Lian-jun

2015-01-01

GABA receptors play an important role in ischemic brain injury. Studies have indicated that autophagy is closely related to neurodegenerative diseases. However, during chronic cerebral hypoperfusion, the changes of autophagy in the hippocampal CA1 area, the correlation between GABA receptors and autophagy, and their influences on hippocampal neuronal apoptosis have not been well established. Here, we found that chronic cerebral hypoperfusion resulted in rat hippocampal atrophy, neuronal apoptosis, enhancement and redistribution of autophagy, down-regulation of Bcl-2/Bax ratio, elevation of cleaved caspase-3 levels, reduction of surface expression of GABAA receptor α1 subunit and an increase in surface and mitochondrial expression of connexin 43 (CX43) and CX36. Chronic administration of GABAB receptors agonist baclofen significantly alleviated neuronal damage. Meanwhile, baclofen could up-regulate the ratio of Bcl-2/Bax and increase the activation of Akt, GSK-3β and ERK which suppressed cytodestructive autophagy. The study also provided evidence that baclofen could attenuate the decrease in surface expression of GABAA receptor α1 subunit, and down-regulate surface and mitochondrial expression of CX43 and CX36, which might enhance protective autophagy. The current findings suggested that, under chronic cerebral hypoperfusion, the effects of GABAB receptors activation on autophagy regulation could reverse neuronal damage. PMID:26412641

Dorsal–Ventral Gradient for Neuronal Plasticity in the Embryonic Spinal Cord

PubMed Central

Pineda, Ricardo H.; Ribera, Angeles B.

2008-01-01

Within the developing Xenopus spinal cord, voltage-gated potassium (Kv) channel genes display different expression patterns, many of which occur in opposing dorsal–ventral gradients. Regional differences in Kv gene expression would predict different patterns of potassium current (IKv) regulation. However, during the first 24 h of postmitotic differentiation, all primary spinal neurons undergo a temporally coordinated upregulation of IKv density that shortens the duration of the action potential. Here, we tested whether spinal neurons demonstrate regional differences in IKv regulation subsequent to action potential maturation. We show that two types of neurons, I and II, can be identified in culture on the basis of biophysical and pharmacological properties of IKv and different firing patterns. Chronic increases in extracellular potassium, a signature of high neuronal activity, do not alter excitability properties of either neuron type. However, elevating extracellular potassium acutely after the period of action potential maturation leads to different changes in membrane properties of the two types of neurons. IKv of type I neurons gains sensitivity to the blocker XE991, whereas type II neurons increase IKv density and fire fewer action potentials. Moreover, by recording from neurons in vivo, we found that primary spinal neurons can be identified as either type I or type II. Type I neurons predominate in dorsal regions, whereas type II neurons localize to ventral regions. The findings reveal a dorsal–ventral gradient for IKv regulation and a novel form of neuronal plasticity in spinal cord neurons. PMID:18385340

The MEK-ERK pathway negatively regulates bim expression through the 3' UTR in sympathetic neurons

PubMed Central

2011-01-01

Background Apoptosis plays a critical role during neuronal development and disease. Developing sympathetic neurons depend on nerve growth factor (NGF) for survival during the late embryonic and early postnatal period and die by apoptosis in its absence. The proapoptotic BH3-only protein Bim increases in level after NGF withdrawal and is required for NGF withdrawal-induced death. The regulation of Bim expression in neurons is complex and this study describes a new mechanism by which an NGF-activated signalling pathway regulates bim gene expression in sympathetic neurons. Results We report that U0126, an inhibitor of the prosurvival MEK-ERK pathway, increases bim mRNA levels in sympathetic neurons in the presence of NGF. We find that this effect is independent of PI3-K-Akt and JNK-c-Jun signalling and is not mediated by the promoter, first exon or first intron of the bim gene. By performing 3' RACE and microinjection experiments with a new bim-LUC+3'UTR reporter construct, we show that U0126 increases bim expression via the bim 3' UTR. We demonstrate that this effect does not involve a change in bim mRNA stability and by using PD184352, a specific MEK1/2-ERK1/2 inhibitor, we show that this mechanism involves the MEK1/2-ERK1/2 pathway. Finally, we demonstrate that inhibition of MEK/ERK signalling independently reduces cell survival in NGF-treated sympathetic neurons. Conclusions These results suggest that in sympathetic neurons, MEK-ERK signalling negatively regulates bim expression via the 3' UTR and that this regulation is likely to be at the level of transcription. This data provides further insight into the different mechanisms by which survival signalling pathways regulate bim expression in neurons. PMID:21762482

LRP8-Reelin-regulated Neuronal (LRN) Enhancer Signature Underlying Learning and Memory Formation

PubMed Central

Telese, Francesca; Ma, Qi; Perez, Patricia Montilla; Notani, Dimple; Oh, Soohwan; Li, Wenbo; Comoletti, Davide; Ohgi, Kenneth A.; Taylor, Havilah; Rosenfeld, Michael G.

2015-01-01

Summary One of the exceptional properties of the brain is its ability to acquire new knowledge through learning and to store that information through memory. The epigenetic mechanisms linking changes in neuronal transcriptional programs to behavioral plasticity remain largely unknown. Here, we identify the epigenetic signature of the neuronal enhancers required for transcriptional regulation of synaptic plasticity genes during memory formation, linking this to Reelin signaling. The binding of Reelin to its receptor, LRP8, triggers activation of this cohort of LRP8-Reelin-regulated-Neuronal (LRN) enhancers that serve as the ultimate convergence point of a novel synapse-to-nucleus pathway. Reelin simultaneously regulates NMDA-receptor transmission, which reciprocally permits the required, γ-secretase-dependent cleavage of LRP8, revealing an unprecedented role for its intracellular domain in the regulation of synaptically generated signals. These results uncover an in vivo enhancer code serving as a critical molecular component of cognition and relevant to psychiatric disorders linked to defects in Reelin signaling. PMID:25892301

Chemogenetic Activation of Midbrain Dopamine Neurons Affects Attention, but not Impulsivity, in the Five-Choice Serial Reaction Time Task in Rats.

PubMed

Boekhoudt, Linde; Voets, Elisa S; Flores-Dourojeanni, Jacques P; Luijendijk, Mieneke Cm; Vanderschuren, Louk Jmj; Adan, Roger Ah

2017-05-01

Attentional impairments and exaggerated impulsivity are key features of psychiatric disorders, such as attention-deficit/hyperactivity disorder, schizophrenia, and addiction. These deficits in attentional performance and impulsive behaviors have been associated with aberrant dopamine (DA) signaling, but it remains unknown whether these deficits result from enhanced DA neuronal activity in the midbrain. Here, we took a novel approach by testing the impact of chemogenetically activating DA neurons in the ventral tegmental area (VTA) or substantia nigra pars compacta (SNc) on attention and impulsivity in the five-choice serial reaction time task (5-CSRTT) in rats. We found that activation of DA neurons in both the VTA and SNc impaired attention by increasing trial omissions. In addition, SNc DA neuron activation decreased attentional accuracy. Surprisingly, enhanced DA neuron activity did not affect impulsive action in this task. These results show that enhanced midbrain DA neuronal activity induces deficits in attentional performance, but not impulsivity. Furthermore, DA neurons in the VTA and SNc have different roles in regulating attention. These findings contribute to our understanding of the neural substrates underlying attention deficits and impulsivity, and provide valuable insights to improve treatment of these symptoms.

A novel function of the cell polarity-regulating kinase PAR-1/MARK in dendritic spines

PubMed Central

Hayashi, Kenji; Suzuki, Atsushi; Ohno, Shigeo

2011-01-01

Dendritic spines are postsynaptic structures that receive excitatory synaptic signals from presynaptic terminals in neurons. Because the morphology of spines has been considered to be a crucial factor for the efficiency of synaptic transmission, understanding the mechanisms regulating their morphology is important for neuroscience. Actin filaments and their regulatory proteins are known to actively maintain spine morphology; recent studies have also shown an essential role of microtubules (MTs). Live imaging of the plus-ends of MTs in mature neurons revealed that MTs stochastically enter spines and mediate accumulation of p140Cap, which regulates reorganization of actin filaments. However, the molecular mechanism by which MT dynamics is controlled has remained largely unknown. A cell polarity-regulating serine/threonine kinase, partitioning-defective 1 (PAR-1), phosphorylates classical MAPs and inhibits their binding to MTs. Because the interaction of MAPs with MTs can decrease MT dynamic instability, PAR-1 is supposed to activate MT dynamics through its MAP/MT affinity-regulating kinase (MARK) activity, although there is not yet any direct evidence for this. Here, we review recent findings on the localization of PAR-1b in the dendrites of mouse hippocampal neurons, and its novel function in the maintenance of mature spine morphology by regulating MT dynamics. PMID:22545177

A novel function of the cell polarity-regulating kinase PAR-1/MARK in dendritic spines.

PubMed

Hayashi, Kenji; Suzuki, Atsushi; Ohno, Shigeo

2011-11-01

Dendritic spines are postsynaptic structures that receive excitatory synaptic signals from presynaptic terminals in neurons. Because the morphology of spines has been considered to be a crucial factor for the efficiency of synaptic transmission, understanding the mechanisms regulating their morphology is important for neuroscience. Actin filaments and their regulatory proteins are known to actively maintain spine morphology; recent studies have also shown an essential role of microtubules (MTs). Live imaging of the plus-ends of MTs in mature neurons revealed that MTs stochastically enter spines and mediate accumulation of p140Cap, which regulates reorganization of actin filaments. However, the molecular mechanism by which MT dynamics is controlled has remained largely unknown. A cell polarity-regulating serine/threonine kinase, partitioning-defective 1 (PAR-1), phosphorylates classical MAPs and inhibits their binding to MTs. Because the interaction of MAPs with MTs can decrease MT dynamic instability, PAR-1 is supposed to activate MT dynamics through its MAP/MT affinity-regulating kinase (MARK) activity, although there is not yet any direct evidence for this. Here, we review recent findings on the localization of PAR-1b in the dendrites of mouse hippocampal neurons, and its novel function in the maintenance of mature spine morphology by regulating MT dynamics.

Neuronal migration is regulated by endogenous RNAi and chromatin-binding factor ZFP-1/AF10 in Caenorhabditis elegans.

PubMed

Kennedy, Lisa M; Grishok, Alla

2014-05-01

Endogenous short RNAs and the conserved plant homeodomain (PHD) zinc-finger protein ZFP-1/AF10 regulate overlapping sets of genes in Caenorhabditis elegans, which suggests that they control common biological pathways. We have shown recently that the RNAi factor RDE-4 and ZFP-1 negatively modulate transcription of the insulin/PI3 signaling-dependent kinase PDK-1 to promote C. elegans fitness. Moreover, we have demonstrated that the insulin/IGF-1-PI3K-signaling pathway regulates the activity of the DAF-16/FOXO transcription factor in the hypodermis to nonautonomously promote the anterior migrations of the hermaphrodite-specific neurons (HSNs) during embryogenesis of C. elegans. In this study, we implicate the PHD-containing isoform of ZFP-1 and endogenous RNAi in the regulation of HSN migration. ZFP-1 affects HSN migration in part through its negative effect on pdk-1 transcription and modulation of downstream DAF-16 activity. We also identify a novel role for ZFP-1 and RNAi pathway components, including RDE-4, in the regulation of HSN migration in parallel with DAF-16. Therefore, the coordinated activities of DAF-16, ZFP-1, and endogenous RNAi contribute to gene regulation during development to ensure proper neuronal positioning.

Neuronal Migration Is Regulated by Endogenous RNAi and Chromatin-Binding Factor ZFP-1/AF10 in Caenorhabditis elegans

PubMed Central

Kennedy, Lisa M.; Grishok, Alla

2014-01-01

Endogenous short RNAs and the conserved plant homeodomain (PHD) zinc-finger protein ZFP-1/AF10 regulate overlapping sets of genes in Caenorhabditis elegans, which suggests that they control common biological pathways. We have shown recently that the RNAi factor RDE-4 and ZFP-1 negatively modulate transcription of the insulin/PI3 signaling-dependent kinase PDK-1 to promote C. elegans fitness. Moreover, we have demonstrated that the insulin/IGF-1-PI3K-signaling pathway regulates the activity of the DAF-16/FOXO transcription factor in the hypodermis to nonautonomously promote the anterior migrations of the hermaphrodite-specific neurons (HSNs) during embryogenesis of C. elegans. In this study, we implicate the PHD-containing isoform of ZFP-1 and endogenous RNAi in the regulation of HSN migration. ZFP-1 affects HSN migration in part through its negative effect on pdk-1 transcription and modulation of downstream DAF-16 activity. We also identify a novel role for ZFP-1 and RNAi pathway components, including RDE-4, in the regulation of HSN migration in parallel with DAF-16. Therefore, the coordinated activities of DAF-16, ZFP-1, and endogenous RNAi contribute to gene regulation during development to ensure proper neuronal positioning. PMID:24558261

The long and the short of SAD-1 kinase.

PubMed

Kim, Joanne S M; Hung, Wesley; Zhen, Mei

2010-05-01

The Ser/Thr SAD kinases are evolutionarily conserved, critical regulators of neural development. Exciting findings in recent years have significantly advanced our understanding of the mechanism through which SAD kinases regulate neural development. Mammalian SAD-A and SAD-B, activated by a master kinase LKB1, regulate microtubule dynamics and polarize neurons. In C. elegans, the sad-1 gene encodes two isoforms, namely the long and the short, which exhibit overlapping and yet distinct functions in neuronal polarity and synaptic organization. Surprisingly, our most recent findings in C. elegans revealed a SAD-1-independent LKB1 activity in neuronal polarity. We also found that the long SAD-1 isoform directly interacts with a STRADalpha pseudokinase, STRD-1, to regulate neuronal polarity and synaptic organization. We elaborate here a working model of SAD-1 in which the two isoforms dimer/oligomerize to form a functional complex, and STRD-1 clusters and localizes the SAD-1 complex to synapses. While the mechanistic difference between the vertebrate and invertebrate SAD kinases may be puzzling, a recent discovery of the functionally distinct SAD-B isoforms predicts that the difference likely arises from our incomplete understanding of the SAD kinase mechanism and may eventually be reconciled as the revelation continues.

Gli function is essential for motor neuron induction in zebrafish.

PubMed

Vanderlaan, Gary; Tyurina, Oksana V; Karlstrom, Rolf O; Chandrasekhar, Anand

2005-06-15

The Gli family of zinc-finger transcription factors mediates Hedgehog (Hh) signaling in all vertebrates. However, their roles in ventral neural tube patterning, in particular motor neuron induction, appear to have diverged across species. For instance, cranial motor neurons are essentially lost in zebrafish detour (gli1(-)) mutants, whereas motor neuron development is unaffected in mouse single gli and some double gli knockouts. Interestingly, the expression of some Hh-regulated genes (ptc1, net1a, gli1) is mostly unaffected in the detour mutant hindbrain, suggesting that other Gli transcriptional activators may be involved. To better define the roles of the zebrafish gli genes in motor neuron induction and in Hh-regulated gene expression, we examined these processes in you-too (yot) mutants, which encode dominant repressor forms of Gli2 (Gli2(DR)), and following morpholino-mediated knockdown of gli1, gli2, and gli3 function. Motor neuron induction at all axial levels was reduced in yot (gli2(DR)) mutant embryos. In addition, Hh target gene expression at all axial levels except in rhombomere 4 was also reduced, suggesting an interference with the function of other Glis. Indeed, morpholino-mediated knockdown of Gli2(DR) protein in yot mutants led to a suppression of the defective motor neuron phenotype. However, gli2 knockdown in wild-type embryos generated no discernable motor neuron phenotype, while gli3 knockdown reduced motor neuron induction in the hindbrain and spinal cord. Significantly, gli2 or gli3 knockdown in detour (gli1(-)) mutants revealed roles for Gli2 and Gli3 activator functions in ptc1 expression and spinal motor neuron induction. Similarly, gli1 or gli3 knockdown in yot (gli2(DR)) mutants resulted in severe or complete loss of motor neurons, and of ptc1 and net1a expression, in the hindbrain and spinal cord. In addition, gli1 expression was greatly reduced in yot mutants following gli3, but not gli1, knockdown, suggesting that Gli3 activator function is specifically required for gli1 expression. These observations demonstrate that Gli activator function (encoded by gli1, gli2, and gli3) is essential for motor neuron induction and Hh-regulated gene expression in zebrafish.

Eukaryotic elongation factor 2 kinase regulates the synthesis of microtubule-related proteins in neurons.

PubMed

Kenney, Justin W; Genheden, Maja; Moon, Kyung-Mee; Wang, Xuemin; Foster, Leonard J; Proud, Christopher G

2016-01-01

Modulation of the elongation phase of protein synthesis is important for numerous physiological processes in both neurons and other cell types. Elongation is primarily regulated via eukaryotic elongation factor 2 kinase (eEF2K). However, the consequence of altering eEF2K activity on the synthesis of specific proteins is largely unknown. Using both pharmacological and genetic manipulations of eEF2K combined with two protein-labeling techniques, stable isotope labeling of amino acids in cell culture and bio-orthogonal non-canonical amino acid tagging, we identified a subset of proteins whose synthesis is sensitive to inhibition of eEF2K in murine primary cortical neurons. Gene ontology (GO) analyses indicated that processes related to microtubules are particularly sensitive to eEF2K inhibition. Our findings suggest that eEF2K likely contributes to neuronal function by regulating the synthesis of microtubule-related proteins. Modulation of the elongation phase of protein synthesis is important for numerous physiological processes in neurons. Here, using labeling of new proteins coupled with proteomic techniques in primary cortical neurons, we find that the synthesis of microtubule-related proteins is up-regulated by inhibition of elongation. This suggests that translation elongation is a key regulator of cytoskeletal dynamics in neurons. © 2015 The Authors. Journal of Neurochemistry published by John Wiley & Sons Ltd on behalf of International Society for Neurochemistry.

Reestablishment of Energy Balance in a Male Mouse Model With POMC Neuron Deletion of BMPR1A.

PubMed

Townsend, Kristy L; Madden, Christopher J; Blaszkiewicz, Magdalena; McDougall, Lindsay; Tupone, Domenico; Lynes, Matthew D; Mishina, Yuji; Yu, Paul; Morrison, Shaun F; Tseng, Yu-Hua

2017-12-01

The regulation of energy balance involves complex processes in the brain, including coordination by hypothalamic neurons that contain pro-opiomelanocortin (POMC). We previously demonstrated that central bone morphogenetic protein (BMP) 7 reduced appetite. Now we show that a type 1 BMP receptor, BMPR1A, is colocalized with POMC neurons and that POMC-BMPR1A-knockout (KO) mice are hyperphagic, revealing physiological involvement of BMP signaling in anorectic POMC neurons in the regulation of appetite. Surprisingly, the hyperphagic POMC-BMPR1A-KO mice exhibited a lack of obesity, even on a 45% high-fat diet. This is because the brown adipose tissue (BAT) of KO animals exhibited increased sympathetic activation and greater thermogenic capacity owing to a reestablishment of energy balance, most likely stemming from a compensatory increase of BMPR1A in the whole hypothalamus of KO mice. Indeed, control animals given central BMP7 displayed increased energy expenditure and a specific increase in sympathetic nerve activity (SNA) in BAT. In these animals, pharmacological blockade of BMPR1A-SMAD signaling blunted the ability of BMP7 to increase energy expenditure or BAT SNA. Together, we demonstrated an important role for hypothalamic BMP signaling in the regulation of energy balance, including BMPR1A-mediated appetite regulation in POMC neurons as well as hypothalamic BMP-SMAD regulation of the sympathetic drive to BAT for thermogenesis. Copyright © 2017 Endocrine Society.

Tetramethylpyrazine promotes SH-SY5Y cell differentiation into neurons through epigenetic regulation of Topoisomerase IIβ.

PubMed

Yan, Y; Zhao, J; Cao, C; Jia, Z; Zhou, N; Han, S; Wang, Y; Xu, Y; Zhao, J; Yan, Y; Cui, H

2014-10-10

Tetramethylpyrazine (TMP) is an active compound extracted from the traditional Chinese medicinal herb Chuanxiong. Recently, it has been reported that TMP enhances neurogenesis, and promotes neural stem cell differentiation toward neurons. However, its molecular basis remains unknown. Topoisomerase IIβ (TopoIIβ) is a nuclear enzyme with an essential role in neuronal development. This study aimed to investigate whether TopoIIβ is involved in TMP-induced neuronal differentiation. We examined the effect of TMP on neuronal differentiation of SH-SY5Y cells. It was found that TMP inhibited cell proliferation and induced G0/G1 cell cycle arrest. TMP promoted SH-SY5Y cells to differentiate toward post-mitotic neurons characterized by long, out-branched neurites and up-regulated neuronal markers, microtubule-associated protein 2 (MAP2) and tau. Meanwhile, we demonstrated that TopoIIβ was highly expressed following TMP treatment. To unravel how TMP affects TopoIIβ expression, two chromatin active markers, acetylated histone H3 (Ac-H3) and acetylated histone H4 (Ac-H4) were examined in this study. Our data showed that the levels of Ac-H3 and Ac-H4 were positively correlated with TopoIIβ expression in the processes of neuronal differentiation. We further performed chromatin immunoprecipitation (ChIP) analysis and identified that TMP enhanced the recruitment of Ac-H3 and Ac-H4 to the TopoIIβ gene promoter region. Therefore, we concluded that TMP may stimulate neuronal differentiation of SH-SY5Y cells through epigenetic regulation of TopoIIβ. These results suggest a novel molecular mechanism underlying TMP-promoted neuronal differentiation. Copyright © 2014 IBRO. Published by Elsevier Ltd. All rights reserved.

The Down syndrome-related protein kinase DYRK1A phosphorylates p27Kip1 and Cyclin D1 and induces cell cycle exit and neuronal differentiation

PubMed Central

Soppa, Ulf; Schumacher, Julian; Florencio Ortiz, Victoria; Pasqualon, Tobias; Tejedor, Francisco J; Becker, Walter

2014-01-01

A fundamental question in neurobiology is how the balance between proliferation and differentiation of neuronal precursors is maintained to ensure that the proper number of brain neurons is generated. Substantial evidence implicates DYRK1A (dual specificity tyrosine-phosphorylation-regulated kinase 1A) as a candidate gene responsible for altered neuronal development and brain abnormalities in Down syndrome. Recent findings support the hypothesis that DYRK1A is involved in cell cycle control. Nonetheless, how DYRK1A contributes to neuronal cell cycle regulation and thereby affects neurogenesis remains poorly understood. In the present study we have investigated the mechanisms by which DYRK1A affects cell cycle regulation and neuronal differentiation in a human cell model, mouse neurons, and mouse brain. Dependent on its kinase activity and correlated with the dosage of overexpression, DYRK1A blocked proliferation of SH-SY5Y neuroblastoma cells within 24 h and arrested the cells in G1 phase. Sustained overexpression of DYRK1A induced G0 cell cycle exit and neuronal differentiation. Furthermore, we provide evidence that DYRK1A modulated protein stability of cell cycle-regulatory proteins. DYRK1A reduced cellular Cyclin D1 levels by phosphorylation on Thr286, which is known to induce proteasomal degradation. In addition, DYRK1A phosphorylated p27Kip1 on Ser10, resulting in protein stabilization. Inhibition of DYRK1A kinase activity reduced p27Kip1 Ser10 phosphorylation in cultured hippocampal neurons and in embryonic mouse brain. In aggregate, these results suggest a novel mechanism by which overexpression of DYRK1A may promote premature neuronal differentiation and contribute to altered brain development in Down syndrome. PMID:24806449

Androgen Action via the Androgen Receptor in Neurons Within the Brain Positively Regulates Muscle Mass in Male Mice.

PubMed

Davey, Rachel A; Clarke, Michele V; Russell, Patricia K; Rana, Kesha; Seto, Jane; Roeszler, Kelly N; How, Jackie M Y; Chia, Ling Yeong; North, Kathryn; Zajac, Jeffrey D

2017-10-01

Although it is well established that exogenous androgens have anabolic effects on skeletal muscle mass in humans and mice, data from muscle-specific androgen receptor (AR) knockout (ARKO) mice indicate that myocytic expression of the AR is dispensable for hind-limb muscle mass accrual in males. To identify possible indirect actions of androgens via the AR in neurons to regulate muscle, we generated neuron-ARKO mice in which the dominant DNA binding-dependent actions of the AR are deleted in neurons of the cortex, forebrain, hypothalamus, and olfactory bulb. Serum testosterone and luteinizing hormone levels were elevated twofold in neuron-ARKO males compared with wild-type littermates due to disruption of negative feedback to the hypothalamic-pituitary-gonadal axis. Despite this increase in serum testosterone levels, which was expected to increase muscle mass, the mass of the mixed-fiber gastrocnemius (Gast) and the fast-twitch fiber extensor digitorum longus hind-limb muscles was decreased by 10% in neuron-ARKOs at 12 weeks of age, whereas muscle strength and fatigue of the Gast were unaffected. The mass of the soleus muscle, however, which consists of a high proportion of slow-twitch fibers, was unaffected in neuron-ARKOs, demonstrating a stimulatory action of androgens via the AR in neurons to increase the mass of fast-twitch hind-limb muscles. Furthermore, neuron-ARKOs displayed reductions in voluntary and involuntary physical activity by up to 60%. These data provide evidence for a role of androgens via the AR in neurons to positively regulate fast-twitch hind-limb muscle mass and physical activity in male mice. Copyright © 2017 Endocrine Society.

Leptin-receptor-expressing neurons in the dorsomedial hypothalamus and median preoptic area regulate sympathetic brown adipose tissue circuits.

PubMed

Zhang, Yan; Kerman, Ilan A; Laque, Amanda; Nguyen, Phillip; Faouzi, Miro; Louis, Gwendolyn W; Jones, Justin C; Rhodes, Chris; Münzberg, Heike

2011-02-02

Brown adipose tissue (BAT) thermogenesis is critical to maintain homoeothermia and is centrally controlled via sympathetic outputs. Body temperature and BAT activity also impact energy expenditure, and obesity is commonly associated with decreased BAT capacity and sympathetic tone. Severely obese mice that lack leptin or its receptor (LepRb) show decreased BAT capacity, sympathetic tone, and body temperature and thus are unable to adapt to acute cold exposure (Trayhurn et al., 1976). LepRb-expressing neurons are found in several hypothalamic sites, including the dorsomedial hypothalamus (DMH) and median preoptic area (mPOA), both critical sites to regulate sympathetic, thermoregulatory BAT circuits. Specifically, a subpopulation in the DMH/dorsal hypothalamic area (DHA) is stimulated by fever-inducing endotoxins or cold exposure (Dimicco and Zaretsky, 2007; Morrison et al., 2008). Using the retrograde, transsynaptic tracer pseudorabies virus (PRV) injected into the BAT of mice, we identified PRV-labeled LepRb neurons in the DMH/DHA and mPOA (and other sites), thus indicating their involvement in the regulation of sympathetic BAT circuits. Indeed, acute cold exposure induced c-Fos (as a surrogate for neuronal activity) in DMH/DHA LepRb neurons, and a large number of mPOA LepRb neurons project to the DMH/DHA. Furthermore, DMH/DHA LepRb neurons (and a subpopulation of LepRb mPOA neurons) project and synaptically couple to rostral raphe pallidus neurons, consistent with the current understanding of BAT thermoregulatory circuits from the DMH/DHA and mPOA (Dimicco and Zaretsky, 2007; Morrison et al., 2008). Thus, these data present strong evidence that LepRb neurons in the DMH/DHA and mPOA mediate thermoregulatory leptin action.

The GABAA Receptor RDL Acts in Peptidergic PDF Neurons to Promote Sleep in Drosophila

PubMed Central

Chung, Brian Y.; Kilman, Valerie L.; Keath, J. Russel; Pitman, Jena L.; Allada, Ravi

2011-01-01

SUMMARY Sleep is regulated by a circadian clock that largely times sleep and wake to occur at specific times of day and a sleep homeostat that drives sleep as a function of duration of prior wakefulness[1]. To better understand the role of the circadian clock in sleep regulation, we have been using the fruit fly Drosophila melanogaster[2]. Fruit flies display all of the core behavioral features of sleep including relative immobility, elevated arousal thresholds and homeostatic regulation[2, 3]. We assessed sleep-wake modulation by a core set of 20 circadian pacemaker neurons that express the neuropeptide PDF. We find that PDF neuron ablation, loss of pdf or its receptor pdfr results in increased sleep during the late night in light:dark (LD) conditions and more prominent increases on the first subjective day of constant darkness (DD). Flies deploy similar genetic and neurotransmitter pathways to regulate sleep as their mammalian counterparts, including GABA[4]. We find that RNAi-mediated knockdown of the GABAA receptor gene, Resistant to dieldrin (Rdl), in PDF neurons, reduced sleep consistent with a role for GABA in inhibiting PDF neuron function. Patch clamp electrophysiology reveals GABA-activated picrotoxin-sensitive chloride currents on PDF+ neurons. In addition, RDL is detectable most strongly on the large subset of PDF+ pacemaker neurons. These results suggest that GABAergic inhibition of arousal promoting PDF neurons is an important mode of sleep-wake regulation in vivo. PMID:19230663

Ketamine-induced apoptosis in the mouse cerebral cortex follows similar characteristic of physiological apoptosis and can be regulated by neuronal activity.

PubMed

Wang, Qi; Shen, Feng-Yan; Zou, Rong; Zheng, Jing-Jing; Yu, Xiang; Wang, Ying-Wei

2017-06-17

The effects of general anesthetics on inducing neuronal apoptosis during early brain development are well-documented. However, since physiological apoptosis also occurs during this developmental window, it is important to determine whether anesthesia-induced apoptosis targets the same cell population as physiological apoptosis or different cell types altogether. To provide an adequate plane of surgery, ketamine was co-administered with dexmedetomidine. The apoptotic neurons in the mouse primary somatosensory cortex (S1) were quantitated by immunohistochemistry. To explore the effect of neural activity on ketamine-induced apoptosis, the approaches of Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) and an environmental enrichment (EE) were performed. Ketamine-induced apoptosis in S1 is most prominent at postnatal days 5 and 7 (P5 - P7), and becomes insignificant by P12. Physiological and ketamine-induced apoptosis follow similar developmental patterns, mostly comprised of layer V pyramidal neurons at P5 and shifting to mostly layer II to IV GABAergic neurons by P9. Changes in neuronal activity induced by the DREADD system bidirectionally regulated the pattern of ketamine-induced apoptosis, with reduced activity inducing increased apoptosis and shifting the lamination pattern to a more immature form. Importantly, rearing mice in an EE significantly reduced the magnitude of ketamine-induced apoptosis and shifted its developmental pattern to a more mature form. Together, these results demonstrate that lamination pattern and cell-type dependent vulnerability to ketamine-induced apoptosis follow the physiological apoptosis pattern and are age- and activity-dependent. Naturally elevating neuronal activity is a possible method for reducing the adverse effects of general anesthesia.

Genetically increased cell-intrinsic excitability enhances neuronal integration into adult brain circuits

PubMed Central

Lin, Chia-Wei; Sim, Shuyin; Ainsworth, Alice; Okada, Masayoshi; Kelsch, Wolfgang; Lois, Carlos

2009-01-01

New neurons are added to the adult brain throughout life, but only half ultimately integrate into existing circuits. Sensory experience is an important regulator of the selection of new neurons but it remains unknown whether experience provides specific patterns of synaptic input, or simply a minimum level of overall membrane depolarization critical for integration. To investigate this issue, we genetically modified intrinsic electrical properties of adult-generated neurons in the mammalian olfactory bulb. First, we observed that suppressing levels of cell-intrinsic neuronal activity via expression of ESKir2.1 potassium channels decreases, whereas enhancing activity via expression of NaChBac sodium channels increases survival of new neurons. Neither of these modulations affects synaptic formation. Furthermore, even when neurons are induced to fire dramatically altered patterns of action potentials, increased levels of cell-intrinsic activity completely blocks cell death triggered by NMDA receptor deletion. These findings demonstrate that overall levels of cell-intrinsic activity govern survival of new neurons and precise firing patterns are not essential for neuronal integration into existing brain circuits. PMID:20152111

Neurophysiological, metabolic and cellular compartments that drive neurovascular coupling and neuroimaging signals

PubMed Central

Moreno, Andrea; Jego, Pierrick; de la Cruz, Feliberto; Canals, Santiago

2013-01-01

Complete understanding of the mechanisms that coordinate work and energy supply of the brain, the so called neurovascular coupling, is fundamental to interpreting brain energetics and their influence on neuronal coding strategies, but also to interpreting signals obtained from brain imaging techniques such as functional magnetic resonance imaging. Interactions between neuronal activity and cerebral blood flow regulation are largely compartmentalized. First, there exists a functional compartmentalization in which glutamatergic peri-synaptic activity and its electrophysiological events occur in close proximity to vascular responses. Second, the metabolic processes that fuel peri-synaptic activity are partially segregated between glycolytic and oxidative compartments. Finally, there is cellular segregation between astrocytic and neuronal compartments, which has potentially important implications on neurovascular coupling. Experimental data is progressively showing a tight interaction between the products of energy consumption and neurotransmission-driven signaling molecules that regulate blood flow. Here, we review some of these issues in light of recent findings with special attention to the neuron-glia interplay on the generation of neuroimaging signals. PMID:23543907

Excitatory motor neurons are local oscillators for backward locomotion

PubMed Central

Guan, Sihui Asuka; Fouad, Anthony D; Meng, Jun; Kawano, Taizo; Huang, Yung-Chi; Li, Yi; Alcaire, Salvador; Hung, Wesley; Lu, Yangning; Qi, Yingchuan Billy; Jin, Yishi; Alkema, Mark; Fang-Yen, Christopher

2018-01-01

Cell- or network-driven oscillators underlie motor rhythmicity. The identity of C. elegans oscillators remains unknown. Through cell ablation, electrophysiology, and calcium imaging, we show: (1) forward and backward locomotion is driven by different oscillators; (2) the cholinergic and excitatory A-class motor neurons exhibit intrinsic and oscillatory activity that is sufficient to drive backward locomotion in the absence of premotor interneurons; (3) the UNC-2 P/Q/N high-voltage-activated calcium current underlies A motor neuron’s oscillation; (4) descending premotor interneurons AVA, via an evolutionarily conserved, mixed gap junction and chemical synapse configuration, exert state-dependent inhibition and potentiation of A motor neuron’s intrinsic activity to regulate backward locomotion. Thus, motor neurons themselves derive rhythms, which are dually regulated by the descending interneurons to control the reversal motor state. These and previous findings exemplify compression: essential circuit properties are conserved but executed by fewer numbers and layers of neurons in a small locomotor network. PMID:29360035

Go Signaling in Mushroom Bodies Regulates Sleep in Drosophila

PubMed Central

Guo, Fang; Yi, Wei; Zhou, Mingmin; Guo, Aike

2011-01-01

Study Objectives: Sleep is a fundamental physiological process and its biological mechanisms are poorly understood. In Drosophila melanogaster, heterotrimeric Go protein is abundantly expressed in the brain. However, its post-developmental function has not been extensively explored. Design: Locomotor activity was measured using the Drosophila Activity Monitoring System under a 12:12 LD cycle. Sleep was defined as periods of 5 min with no recorded activity. Results: Pan-neuronal elevation of Go signaling induced quiescence accompanied by an increased arousal threshold in flies. By screening region-specific GAL4 lines, we mapped the sleep-regulatory function of Go signaling to mushroom bodies (MBs), a central brain region which modulates memory, decision making, and sleep in Drosophila. Up-regulation of Go activity in these neurons consolidated sleep while inhibition of endogenous Go via expression of Go RNAi or pertussis toxin reduced and fragmented sleep, indicating that the Drosophila sleep requirement is affected by levels of Go activity in the MBs. Genetic interaction results showed that Go signaling serves as a neuronal transmission inhibitor in a cAMP-independent pathway. Conclusion: Go signaling is a novel signaling pathway in MBs that regulates sleep in Drosophila. Citation: Guo F; Yi W; Zhou M; Guo A. Go signaling in mushroom bodies regulates sleep in drosophila. SLEEP 2011;34(3):273-281. PMID:21358844

Identification of an immune-responsive mesolimbocortical serotonergic system: Potential role in regulation of emotional behavior

PubMed Central

Lowry, C.A.; Hollis, J.H.; de Vries, A.; Pan, B.; Brunet, L.R.; Hunt, J.R.F.; Paton, J.F.R.; van Kampen, E.; Knight, D.M.; Evans, A.K.; Rook, G.A.W.; Lightman, S.L.

2007-01-01

Peripheral immune activation can have profound physiological and behavioral effects including induction of fever and sickness behavior. One mechanism through which immune activation or immunomodulation may affect physiology and behavior is via actions on brainstem neuromodulatory systems, such as serotonergic systems. We have found that peripheral immune activation with antigens derived from the nonpathogenic, saprophytic bacterium, Mycobacterium vaccae, activated a specific subset of serotonergic neurons in the interfascicular part of the dorsal raphe nucleus (DRI) of mice, as measured by quantification of c-Fos expression following intratracheal (12 h) or s.c. (6 h) administration of heat-killed, ultrasonically disrupted M. vaccae, or heat-killed, intact M. vaccae, respectively. These effects were apparent after immune activation by M. vaccae or its components but not by ovalbumin, which induces a qualitatively different immune response. The effects of immune activation were associated with increases in serotonin metabolism within the ventromedial prefrontal cortex, consistent with an effect of immune activation on mesolimbocortical serotonergic systems. The effects of M. vaccae administration on serotonergic systems were temporally associated with reductions in immobility in the forced swim test, consistent with the hypothesis that the stimulation of mesolimbocortical serotonergic systems by peripheral immune activation alters stress-related emotional behavior. These findings suggest that the immune-responsive subpopulation of serotonergic neurons in the DRI is likely to play an important role in the neural mechanisms underlying regulation of the physiological and pathophysiological responses to both acute and chronic immune activation, including regulation of mood during health and disease states. Together with previous studies, these findings also raise the possibility that immune stimulation activates a functionally and anatomically distinct subset of serotonergic neurons, different from the subset of serotonergic neurons activated by anxiogenic stimuli or uncontrollable stressors. Consequently, selective activation of specific subsets of serotonergic neurons may have distinct behavioral outcomes. PMID:17367941

Daucosterol protects neurons against oxygen-glucose deprivation/reperfusion-mediated injury by activating IGF1 signaling pathway.

PubMed

Jiang, Li-hua; Yuan, Xiao-lin; Yang, Nian-yun; Ren, Li; Zhao, Feng-ming; Luo, Ban-xin; Bian, Yao-yao; Xu, Jian-ya; Lu, Da-xiang; Zheng, Yuan-yuan; Zhang, Chuan-juan; Diao, Yuan-ming; Xia, Bao-mei; Chen, Gang

2015-08-01

We previously reported that daucosterol (a sterolin) up-regulates the expression of insulin-like growth factor I (IGF1)(1) protein in neural stem cells. In this study, we investigated the effects of daucosterol on the survival of cultured cortical neurons after neurons were subjected to oxygen and glucose deprivation and simulated reperfusion (OGD/R)(2), and determined the corresponding molecular mechanism. The results showed that post-treatment of daucosterol significantly reduced neuronal loss, as well as apoptotic rate and caspase-3 activity, displaying the neuroprotective activity. We also found that daucosterol increased the expression level of IGF1 protein, diminished the down-regulation of p-AKT(3) and p-GSK-3β(4), thus activating the AKT(5) signal pathway. Additionally, it diminished the down-regulation of the anti-apoptotic proteins Mcl-1(6) and Bcl-2(7), and decreased the expression level of the pro-apoptotic protein Bax(8), thus raising the ratio of Bcl-2/Bax. The neuroprotective effect of daucosterol was inhibited in the presence of picropodophyllin (PPP)(9), the inhibitor of insulin-like growth factor I receptors (IGF1R)(10). Our study provided information about daucosterol as an efficient and inexpensive neuroprotectants, to which the IGF1-like activity of daucosterol contributes. Daucosterol could be potentially developed as a medicine for ischemic stroke treatment. Copyright © 2015 Elsevier Ltd. All rights reserved.

Alcohol induces synaptotagmin 1 expression in neurons via activation of heat shock factor 1.

PubMed

Varodayan, F P; Pignataro, L; Harrison, N L

2011-10-13

Many synapses within the central nervous system are sensitive to ethanol. Although alcohol is known to affect the probability of neurotransmitter release in specific brain regions, the effects of alcohol on the underlying synaptic vesicle fusion machinery have been little studied. To identify a potential pathway by which ethanol can regulate neurotransmitter release, we investigated the effects of acute alcohol exposure (1-24 h) on the expression of the gene encoding synaptotagmin 1 (Syt1), a synaptic protein that binds calcium to directly trigger vesicle fusion. Syt1 was identified in a microarray screen as a gene that may be sensitive to alcohol and heat shock. We found that Syt1 mRNA and protein expression are rapidly and robustly up-regulated by ethanol in mouse cortical neurons, and that the distribution of Syt1 protein along neuronal processes is also altered. Syt1 mRNA up-regulation is dependent on the activation of the transcription factor heat shock factor 1 (HSF1). The transfection of a constitutively active Hsf1 construct into neurons stimulates Syt1 transcription, while transfection of Hsf1 small interfering RNA (siRNA) or a constitutively inactive Hsf1 construct into neurons attenuates the induction of Syt1 by ethanol. This suggests that the activation of HSF1 can induce Syt1 expression and that this may be a mechanism by which alcohol regulates neurotransmitter release during brief exposures. Further analysis revealed that a subset of the genes encoding the core synaptic vesicle fusion (soluble NSF (N-ethylmaleimide-sensitive factor) attachment protein receptor; SNARE) proteins share this property of induction by ethanol, suggesting that alcohol may trigger a specific coordinated adaptation in synaptic function. This molecular mechanism could explain some of the changes in synaptic function that occur following alcohol administration and may be an important step in the process of neuronal adaptation to alcohol. Copyright © 2011 IBRO. Published by Elsevier Ltd. All rights reserved.

Organizational and activational effects of sex steroids on kisspeptin neuron development

PubMed Central

Poling, Matthew C.; Kauffman, Alexander S.

2012-01-01

Kisspeptin, encoded by the Kiss1 gene, is a neuropeptide required for puberty and adult reproductive function. Understanding the regulation and development of the kisspeptin system provides valuable knowledge about the physiology of puberty and adult fertility, and may provide insights into human pubertal or reproductive disorders. Recent studies, particularly in rodent models, have assessed how kisspeptin neurons develop and how hormonal and non-hormonal factors regulate this developmental process. Exposure to sex steroids (testosterone and estradiol) during critical periods of development can induce organizational (permanent) effects on kisspeptin neuron development, with respect to both sexually dimorphic and non-sexually dimorphic aspects of kisspeptin biology. In addition, sex steroids can also impart activational (temporary) effects on kisspeptin neurons and Kiss1 gene expression at various times during neonatal and peripubertal development, as they do in adulthood. Here, we discuss the current knowledge—and in some cases, lack thereof—of the influence of hormones and other factors on kisspeptin neuronal development. PMID:22728025

Glucose level determines excitatory or inhibitory effects of adiponectin on arcuate POMC neuron activity and feeding

PubMed Central

Suyama, Shigetomo; Maekawa, Fumihiko; Maejima, Yuko; Kubota, Naoto; Kadowaki, Takashi; Yada, Toshihiko

2016-01-01

Adiponectin regulates glucose and lipid metabolism, acting against metabolic syndrome and atherosclerosis. Accumulating evidence suggest that adiponectin acts on the brain including hypothalamic arcuate nucleus (ARC), where proopiomelanocortin (POMC) neurons play key roles in feeding regulation. Several studies have examined intracerebroventricular (ICV) injection of adiponectin and reported opposite effects, increase or decrease of food intake. These reports used different nutritional states. The present study aimed to clarify whether adiponectin exerts distinct effects on food intake and ARC POMC neurons depending on the glucose concentration. Adiponectin was ICV injected with or without glucose for feeding experiments and administered to ARC slices with high or low glucose for patch clamp experiments. We found that adiponectin at high glucose inhibited POMC neurons and increased food intake while at low glucose it exerted opposite effects. The results demonstrate that glucose level determines excitatory or inhibitory effects of adiponectin on arcuate POMC neuron activity and feeding. PMID:27503800

P21-activated kinase 2 (PAK2) regulates glucose uptake and insulin sensitivity in neuronal cells.

PubMed

Varshney, Pallavi; Dey, Chinmoy Sankar

2016-07-05

P21-activated kinases (PAKs) are recently reported as important players of insulin signaling and glucose homeostasis in tissues like muscle, pancreas and liver. However, their role in neuronal insulin signaling is still unknown. Present study reports the involvement of PAK2 in neuronal insulin signaling, glucose uptake and insulin resistance. Irrespective of insulin sensitivity, insulin stimulation decreased PAK2 activity. PAK2 downregulation displayed marked enhancement of GLUT4 translocation with increase in glucose uptake whereas PAK2 over-expression showed its reduction. Treatment with Akti-1/2 and wortmannin suggested that Akt and PI3K are mediators of insulin effect on PAK2 and glucose uptake. Rac1 inhibition demonstrated decreased PAK2 activity while inhibition of PP2A resulted in increased PAK2 activity, with corresponding changes in glucose uptake. Taken together, present study demonstrates an inhibitory role of insulin signaling (via PI3K-Akt) and PP2A on PAK2 activity and establishes PAK2 as a Rac1-dependent negative regulator of neuronal glucose uptake and insulin sensitivity. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

The Hem protein mediates neuronal migration by inhibiting WAVE degradation and functions opposite of Abelson tyrosine kinase

PubMed Central

Zhu, Zengrong; Bhat, Krishna Moorthi

2011-01-01

In the nervous system, neurons form in different regions, then they migrate and occupy specific positions. We have previously shown that RP2/sib, a well-studied neuronal pair in the Drosophila ventral nerve cord (VNC), has a complex migration route. Here, we show that the Hem protein, via the WAVE complex, regulates migration of GMC-1 and its progeny RP2 neuron. In Hem or WAVE mutants, RP2 neuron either abnormally migrates, crossing the midline from one hemisegment to the contralateral hemisegment, or does not migrate at al and fail to send out its axon projection. We report that Hem regulates neuronal migration through stabilizing WAVE. Since Hem and WAVE normally form a complex, our data argues that in the absence of Hem, WAVE, which is presumably no longer in a complex, becomes susceptible to degradation. We also find that Abelson Tyrosine kinase affects RP2 migration in a similar manner as Hem and WAVE, and appears to operate via WAVE. However, while Abl negatively regulates the levels of WAVE, it regulates migration via regulating the activity of WAVE. Our results also show that during the degradation of WAVE, Hem function is opposite to that of and downstream of Abl. PMID:21726548

“Listening” and “talking” to neurons: Implications of immune activation for pain control and increasing the efficacy of opioids

PubMed Central

Watkins, Linda R.; Hutchinson, Mark R.; Milligan, Erin D.; Maier, Steven F.

2008-01-01

It is recently become clear that activated immune cells and immune-like glial cells can dramatically alter neuronal function. By increasing neuronal excitability, these non-neuronal cells are now implicated in the creation and maintenance of pathological pain, such as occurs in response to peripheral nerve injury. Such effects are exerted at multiple sites along the pain pathway, including at peripheral nerves, dorsal root ganglia, and spinal cord. In addition, activated glial cells are now recognized as disrupting the pain suppressive effects of opioid drugs and contributing to opioid tolerance and opioid dependence/withdrawal. While this review focuses on regulation of pain and opioid actions, such immune-neuronal interactions are broad in their implications. Such changes in neuronal function would be expected to occur wherever immune-derived substances come in close contact with neurons. PMID:17706291

C1 neurons: the body's EMTs

PubMed Central

Stornetta, Ruth L.; Bochorishvili, Genrieta; DePuy, Seth D.; Burke, Peter G. R.; Abbott, Stephen B. G.

2013-01-01

The C1 neurons reside in the rostral and intermediate portions of the ventrolateral medulla (RVLM, IVLM). They use glutamate as a fast transmitter and synthesize catecholamines plus various neuropeptides. These neurons regulate the hypothalamic pituitary axis via direct projections to the paraventricular nucleus and regulate the autonomic nervous system via projections to sympathetic and parasympathetic preganglionic neurons. The presympathetic C1 cells, located in the RVLM, are probably organized in a roughly viscerotopic manner and most of them regulate the circulation. C1 cells are variously activated by hypoglycemia, infection or inflammation, hypoxia, nociception, and hypotension and contribute to most glucoprivic responses. C1 cells also stimulate breathing and activate brain stem noradrenergic neurons including the locus coeruleus. Based on the various effects attributed to the C1 cells, their axonal projections and what is currently known of their synaptic inputs, subsets of C1 cells appear to be differentially recruited by pain, hypoxia, infection/inflammation, hemorrhage, and hypoglycemia to produce a repertoire of stereotyped autonomic, metabolic, and neuroendocrine responses that help the organism survive physical injury and its associated cohort of acute infection, hypoxia, hypotension, and blood loss. C1 cells may also contribute to glucose and cardiovascular homeostasis in the absence of such physical stresses, and C1 cell hyperactivity may contribute to the increase in sympathetic nerve activity associated with diseases such as hypertension. PMID:23697799

C1 neurons: the body's EMTs.

PubMed

Guyenet, Patrice G; Stornetta, Ruth L; Bochorishvili, Genrieta; Depuy, Seth D; Burke, Peter G R; Abbott, Stephen B G

2013-08-01

The C1 neurons reside in the rostral and intermediate portions of the ventrolateral medulla (RVLM, IVLM). They use glutamate as a fast transmitter and synthesize catecholamines plus various neuropeptides. These neurons regulate the hypothalamic pituitary axis via direct projections to the paraventricular nucleus and regulate the autonomic nervous system via projections to sympathetic and parasympathetic preganglionic neurons. The presympathetic C1 cells, located in the RVLM, are probably organized in a roughly viscerotopic manner and most of them regulate the circulation. C1 cells are variously activated by hypoglycemia, infection or inflammation, hypoxia, nociception, and hypotension and contribute to most glucoprivic responses. C1 cells also stimulate breathing and activate brain stem noradrenergic neurons including the locus coeruleus. Based on the various effects attributed to the C1 cells, their axonal projections and what is currently known of their synaptic inputs, subsets of C1 cells appear to be differentially recruited by pain, hypoxia, infection/inflammation, hemorrhage, and hypoglycemia to produce a repertoire of stereotyped autonomic, metabolic, and neuroendocrine responses that help the organism survive physical injury and its associated cohort of acute infection, hypoxia, hypotension, and blood loss. C1 cells may also contribute to glucose and cardiovascular homeostasis in the absence of such physical stresses, and C1 cell hyperactivity may contribute to the increase in sympathetic nerve activity associated with diseases such as hypertension.

Glutamatergic Preoptic Area Neurons That Express Leptin Receptors Drive Temperature-Dependent Body Weight Homeostasis.

PubMed

Yu, Sangho; Qualls-Creekmore, Emily; Rezai-Zadeh, Kavon; Jiang, Yanyan; Berthoud, Hans-Rudolf; Morrison, Christopher D; Derbenev, Andrei V; Zsombok, Andrea; Münzberg, Heike

2016-05-04

The preoptic area (POA) regulates body temperature, but is not considered a site for body weight control. A subpopulation of POA neurons express leptin receptors (LepRb(POA) neurons) and modulate reproductive function. However, LepRb(POA) neurons project to sympathetic premotor neurons that control brown adipose tissue (BAT) thermogenesis, suggesting an additional role in energy homeostasis and body weight regulation. We determined the role of LepRb(POA) neurons in energy homeostasis using cre-dependent viral vectors to selectively activate these neurons and analyzed functional outcomes in mice. We show that LepRb(POA) neurons mediate homeostatic adaptations to ambient temperature changes, and their pharmacogenetic activation drives robust suppression of energy expenditure and food intake, which lowers body temperature and body weight. Surprisingly, our data show that hypothermia-inducing LepRb(POA) neurons are glutamatergic, while GABAergic POA neurons, originally thought to mediate warm-induced inhibition of sympathetic premotor neurons, have no effect on energy expenditure. Our data suggest a new view into the neurochemical and functional properties of BAT-related POA circuits and highlight their additional role in modulating food intake and body weight. Brown adipose tissue (BAT)-induced thermogenesis is a promising therapeutic target to treat obesity and metabolic diseases. The preoptic area (POA) controls body temperature by modulating BAT activity, but its role in body weight homeostasis has not been addressed. LepRb(POA) neurons are BAT-related neurons and we show that they are sufficient to inhibit energy expenditure. We further show that LepRb(POA) neurons modulate food intake and body weight, which is mediated by temperature-dependent homeostatic responses. We further found that LepRb(POA) neurons are stimulatory glutamatergic neurons, contrary to prevalent models, providing a new view on thermoregulatory neural circuits. In summary, our study significantly expands our current understanding of central circuits and mechanisms that modulate energy homeostasis. Copyright © 2016 the authors 0270-6474/16/365034-13$15.00/0.

Glutamatergic Preoptic Area Neurons That Express Leptin Receptors Drive Temperature-Dependent Body Weight Homeostasis

PubMed Central

Qualls-Creekmore, Emily; Rezai-Zadeh, Kavon; Jiang, Yanyan; Berthoud, Hans-Rudolf; Morrison, Christopher D.; Derbenev, Andrei V.; Zsombok, Andrea

2016-01-01

The preoptic area (POA) regulates body temperature, but is not considered a site for body weight control. A subpopulation of POA neurons express leptin receptors (LepRbPOA neurons) and modulate reproductive function. However, LepRbPOA neurons project to sympathetic premotor neurons that control brown adipose tissue (BAT) thermogenesis, suggesting an additional role in energy homeostasis and body weight regulation. We determined the role of LepRbPOA neurons in energy homeostasis using cre-dependent viral vectors to selectively activate these neurons and analyzed functional outcomes in mice. We show that LepRbPOA neurons mediate homeostatic adaptations to ambient temperature changes, and their pharmacogenetic activation drives robust suppression of energy expenditure and food intake, which lowers body temperature and body weight. Surprisingly, our data show that hypothermia-inducing LepRbPOA neurons are glutamatergic, while GABAergic POA neurons, originally thought to mediate warm-induced inhibition of sympathetic premotor neurons, have no effect on energy expenditure. Our data suggest a new view into the neurochemical and functional properties of BAT-related POA circuits and highlight their additional role in modulating food intake and body weight. SIGNIFICANCE STATEMENT Brown adipose tissue (BAT)-induced thermogenesis is a promising therapeutic target to treat obesity and metabolic diseases. The preoptic area (POA) controls body temperature by modulating BAT activity, but its role in body weight homeostasis has not been addressed. LepRbPOA neurons are BAT-related neurons and we show that they are sufficient to inhibit energy expenditure. We further show that LepRbPOA neurons modulate food intake and body weight, which is mediated by temperature-dependent homeostatic responses. We further found that LepRbPOA neurons are stimulatory glutamatergic neurons, contrary to prevalent models, providing a new view on thermoregulatory neural circuits. In summary, our study significantly expands our current understanding of central circuits and mechanisms that modulate energy homeostasis. PMID:27147656

Regulation of hippocampus-dependent memory by the zinc finger protein Zbtb20 in mature CA1 neurons.

PubMed

Ren, Anjing; Zhang, Huan; Xie, Zhifang; Ma, Xianhua; Ji, Wenli; He, David Z Z; Yuan, Wenjun; Ding, Yu-Qiang; Zhang, Xiao-Hui; Zhang, Weiping J

2012-10-01

The mammalian hippocampus harbours neural circuitry that is crucial for associative learning and memory. The mechanisms that underlie the development and regulation of this complex circuitry are not fully understood. Our previous study established an essential role for the zinc finger protein Zbtb20 in the specification of CA1 field identity in the developing hippocampus. Here, we show that conditionally deleting Zbtb20 specifically in mature CA1 pyramidal neurons impaired hippocampus-dependent memory formation, without affecting hippocampal architecture or the survival, identity and basal excitatory synaptic activity of CA1 pyramidal neurons. We demonstrate that mature CA1-specific Zbtb20 knockout mice exhibited reductions in long-term potentiation (LTP) and NMDA receptor (NMDAR)-mediated excitatory post-synaptic currents. Furthermore, we show that activity-induced phosphorylation of ERK and CREB is impaired in the hippocampal CA1 of Zbtb20 mutant mice. Collectively, these results indicate that Zbtb20 in mature CA1 plays an important role in LTP and memory by regulating NMDAR activity, and activation of ERK and CREB.

Spatio-temporal regulations and functions of neuronal alternative RNA splicing in developing and adult brains.

PubMed

Iijima, Takatoshi; Hidaka, Chiharu; Iijima, Yoko

2016-08-01

Alternative pre-mRNA splicing is a fundamental mechanism that generates molecular diversity from a single gene. In the central nervous system (CNS), key neural developmental steps are thought to be controlled by alternative splicing decisions, including the molecular diversity underlying synaptic wiring, plasticity, and remodeling. Significant progress has been made in understanding the molecular mechanisms and functions of alternative pre-mRNA splicing in neurons through studies in invertebrate systems; however, recent studies have begun to uncover the potential role of neuronal alternative splicing in the mammalian CNS. This article provides an overview of recent findings regarding the regulation and function of neuronal alternative splicing. In particular, we focus on the spatio-temporal regulation of neurexin, a synaptic adhesion molecule, by neuronal cell type-specific factors and neuronal activity, which are thought to be especially important for characterizing neural development and function within the mammalian CNS. Notably, there is increasing evidence that implicates the dysregulation of neuronal splicing events in several neurological disorders. Therefore, understanding the detailed mechanisms of neuronal alternative splicing in the mammalian CNS may provide plausible treatment strategies for these diseases. Copyright © 2016 Elsevier Ireland Ltd and Japan Neuroscience Society. All rights reserved.

Contributions of Bcl-xL to acute and long term changes in bioenergetics during neuronal plasticity.

PubMed

Jonas, Elizabeth A

2014-08-01

Mitochondria manufacture and release metabolites and manage calcium during neuronal activity and synaptic transmission, but whether long term alterations in mitochondrial function contribute to the neuronal plasticity underlying changes in organism behavior patterns is still poorly understood. Although normal neuronal plasticity may determine learning, in contrast a persistent decline in synaptic strength or neuronal excitability may portend neurite retraction and eventual somatic death. Anti-death proteins such as Bcl-xL not only provide neuroprotection at the neuronal soma during cell death stimuli, but also appear to enhance neurotransmitter release and synaptic growth and development. It is proposed that Bcl-xL performs these functions through its ability to regulate mitochondrial release of bioenergetic metabolites and calcium, and through its ability to rapidly alter mitochondrial positioning and morphology. Bcl-xL also interacts with proteins that directly alter synaptic vesicle recycling. Bcl-xL translocates acutely to sub-cellular membranes during neuronal activity to achieve changes in synaptic efficacy. After stressful stimuli, pro-apoptotic cleaved delta N Bcl-xL (ΔN Bcl-xL) induces mitochondrial ion channel activity leading to synaptic depression and this is regulated by caspase activation. During physiological states of decreased synaptic stimulation, loss of mitochondrial Bcl-xL and low level caspase activation occur prior to the onset of long term decline in synaptic efficacy. The degree to which Bcl-xL changes mitochondrial membrane permeability may control the direction of change in synaptic strength. The small molecule Bcl-xL inhibitor ABT-737 has been useful in defining the role of Bcl-xL in synaptic processes. Bcl-xL is crucial to the normal health of neurons and synapses and its malfunction may contribute to neurodegenerative disease. Copyright © 2013. Published by Elsevier B.V.

Modulation of A-type K+ channels by the short-chain cobrotoxin through the protein kinase C-delta isoform decreases membrane excitability in dorsal root ganglion neurons.

PubMed

Guo, Qiang; Jiang, You-Jing; Jin, Hong; Jiang, Xing-Hong; Gu, Bo; Zhang, Yi-Ming; Wang, Jian-Gong; Qin, Zheng-Hong; Tao, Jin

2013-05-01

A-type K(+) channels are crucial in controlling neuronal excitability, and their regulation in sensory neurons may alter pain sensation. In this study, we identified the functional role of cobrotoxin, the short-chain α-neurotoxin isolated from Naja atra venom, which acts in the regulation of the transient A-type K(+) currents (IA) and membrane excitability in dorsal root ganglion (DRG) neurons via the activation of the muscarinic M3 receptor (M3R). Our results showed that cobrotoxin increased IA in a concentration-dependent manner, whereas the sustained delayed rectifier K(+) currents (IDR) were not affected. Cobrotoxin did not affect the activation of IA markedly, however, it shifted the inactivation curve significantly in the depolarizing direction. The cobrotoxin-induced IA response was blocked by the M3R-selective antagonists DAU-5884 and 4-DAMP. An siRNA targeting the M3R in small DRG neurons abolished the cobrotoxin-induced IA increase. In addition, dialysis of the cells with the novel protein kinase C-delta isoform (PKC-δ) inhibitor δv1-1 or an siRNA targeting PKC-δ abolished the cobrotoxin-induced IA response, whereas inhibition of PKA or classic PKC activity elicited no such effects. Moreover, we observed a significant decrease in the firing rate of the neuronal action potential induced by M3R activation. Pretreatment of the cells with 4-aminopyridine, a selective blocker of IA, abolished this effect. Taken together, these results suggest that the short-chain cobrotoxin selectively enhances IA via a novel PKC-δ-dependent pathway. This effect occurred via the activation of M3R and might contribute to its neuronal hypoexcitability in small DRG neurons. Copyright © 2013 Elsevier Inc. All rights reserved.

Interaction of Constitutive Nitric Oxide Synthases with Cyclooxygenases in Regulation of Bicarbonate Secretion in the Gastric Mucosa.

PubMed

Zolotarev, V A; Andreeva, Yu V; Vershinina, E; Khropycheva, R P

2017-05-01

Neuronal NO synthase blocker 7-nitroindazole suppressed bicarbonate secretion in rat gastric mucosa induced by mild local irritation with 1 M NaCl (pH 2.0). Non-selective blocker of neuronal and endothelial synthases, Nω-nitro-L-arginine (L-NNA), did not affect HCO 3 - production, but inhibited secretion after pretreatment with omeprazole. Non-selective cyclooxygenase blocker indomethacin inhibited HCO 3 - production under conditions of normal synthase activity and in the presence of L-NNA, but was ineffective when co-administered with 7-nitroindazole. It was concluded that neuronal and endothelial synthases are involved in different mechanisms of regulation of HCO 3 - secretion in the gastric mucosa induced by mild irritation. Activation of neuronal synthase stimulated HCO 3 - production, which is mediated mainly through activation of cyclooxygenase. Theoretically, activation of endothelial synthase should suppress HCO 3 - production. The effect of endothelial synthase depends on acid secretion in the stomach and bicarbonate concentration in the submucosa, as it was demonstrated in experiments with intravenous NaHCO 3 infusion.

Disrupted Prediction Error Links Excessive Amygdala Activation to Excessive Fear.

PubMed

Sengupta, Auntora; Winters, Bryony; Bagley, Elena E; McNally, Gavan P

2016-01-13

Basolateral amygdala (BLA) is critical for fear learning, and its heightened activation is widely thought to underpin a variety of anxiety disorders. Here we used chemogenetic techniques in rats to study the consequences of heightened BLA activation for fear learning and memory, and to specifically identify a mechanism linking increased activity of BLA glutamatergic neurons to aberrant fear. We expressed the excitatory hM3Dq DREADD in rat BLA glutamatergic neurons and showed that CNO acted selectively to increase their activity, depolarizing these neurons and increasing their firing rates. This chemogenetic excitation of BLA glutamatergic neurons had no effect on the acquisition of simple fear learning, regardless of whether this learning led to a weak or strong fear memory. However, in an associative blocking task, chemogenetic excitation of BLA glutamatergic neurons yielded significant learning to a blocked conditioned stimulus, which otherwise should not have been learned about. Moreover, in an overexpectation task, chemogenetic manipulation of BLA glutamatergic neurons prevented use of negative prediction error to reduce fear learning, leading to significant impairments in fear inhibition. These effects were not attributable to the chemogenetic manipulation enhancing arousal, increasing asymptotic levels of fear learning or fear memory consolidation. Instead, chemogenetic excitation of BLA glutamatergic neurons disrupted use of prediction error to regulate fear learning. Several neuropsychiatric disorders are characterized by heightened activation of the amygdala. This heightened activation has been hypothesized to underlie increased emotional reactivity, fear over generalization, and deficits in fear inhibition. Yet the mechanisms linking heightened amygdala activation to heightened emotional learning are elusive. Here we combined chemogenetic excitation of rat basolateral amygdala glutamatergic neurons with a variety of behavioral approaches to show that, although simple fear learning is unaffected, the use of prediction error to regulate this learning is profoundly disrupted, leading to formation of inappropriate fear associations and impaired fear inhibition. Copyright © 2016 the authors 0270-6474/16/360385-11$15.00/0.

Glucose Induces Slow-Wave Sleep by Exciting the Sleep-Promoting Neurons in the Ventrolateral Preoptic Nucleus: A New Link between Sleep and Metabolism.

PubMed

Varin, Christophe; Rancillac, Armelle; Geoffroy, Hélène; Arthaud, Sébastien; Fort, Patrice; Gallopin, Thierry

2015-07-08

Sleep-active neurons located in the ventrolateral preoptic nucleus (VLPO) play a crucial role in the induction and maintenance of slow-wave sleep (SWS). However, the cellular and molecular mechanisms responsible for their activation at sleep onset remain poorly understood. Here, we test the hypothesis that a rise in extracellular glucose concentration in the VLPO can promote sleep by increasing the activity of sleep-promoting VLPO neurons. We find that infusion of a glucose concentration into the VLPO of mice promotes SWS and increases the density of c-Fos-labeled neurons selectively in the VLPO. Moreover, we show in patch-clamp recordings from brain slices that VLPO neurons exhibiting properties of sleep-promoting neurons are selectively excited by glucose within physiological range. This glucose-induced excitation implies the catabolism of glucose, leading to a closure of ATP-sensitive potassium (KATP) channels. The extracellular glucose concentration monitors the gating of KATP channels of sleep-promoting neurons, highlighting that these neurons can adapt their excitability according to the extracellular energy status. Together, these results provide evidence that glucose may participate in the mechanisms of SWS promotion and/or consolidation. Although the brain circuitry underlying vigilance states is well described, the molecular mechanisms responsible for sleep onset remain largely unknown. Combining in vitro and in vivo experiments, we demonstrate that glucose likely contributes to sleep onset facilitation by increasing the excitability of sleep-promoting neurons in the ventrolateral preoptic nucleus (VLPO). We find here that these neurons integrate energetic signals such as ambient glucose directly to regulate vigilance states accordingly. Glucose-induced excitation of sleep-promoting VLPO neurons should therefore be involved in the drowsiness that one feels after a high-sugar meal. This novel mechanism regulating the activity of VLPO neurons reinforces the fundamental and intimate link between sleep and metabolism. Copyright © 2015 the authors 0270-6474/15/359900-12$15.00/0.

The metabolic regulator PGC-1α directly controls the expression of the hypothalamic neuropeptide oxytocin.

PubMed

Blechman, Janna; Amir-Zilberstein, Liat; Gutnick, Amos; Ben-Dor, Shifra; Levkowitz, Gil

2011-10-19

The transcriptional coactivator PGC-1α is a key regulator of cellular energy expenditure in peripheral tissues. Recent studies report that PGC-1α-null mice develop late-onset obesity and that the neuronal inactivation of PGC-1α causes increased food intake. However, the exact role of PGC-1α in the CNS remains unclear. Here we show that PGC-1α directly regulates the expression of the hypothalamic neuropeptide oxytocin, a known central regulator of appetite. We developed a unique genetic approach in the zebrafish, allowing us to monitor and manipulate PGC-1α activity in oxytocinergic neurons. We found that PGC-1α is coexpressed with oxytocin in the zebrafish hypothalamus. Targeted knockdown of the zebrafish PGC-1α gene activity caused a marked decrease in oxytocin mRNA levels and inhibited the expression of a transgenic GFP reporter driven by the oxytocin promoter. The effect of PGC-1α loss of function on oxytocin gene activity was rescued by tissue-specific re-expression of either PGC-1α or oxytocin precursor in zebrafish oxytocinergic neurons. PGC-1α activated the oxytocin promoter in a heterologous cell culture system, and overexpression of PGC-1α induced ectopic expression of oxytocin in muscles and neurons. Finally, PGC-1α forms an in vivo complex with the oxytocin promoter in fed but not fasted animals. These findings demonstrate that PGC-1α is both necessary and sufficient for the production of oxytocin, implicating hypothalamic PGC-1α in the direct activation of a hypothalamic hormone known to control energy intake.

Canonical TGF-β Signaling Negatively Regulates Neuronal Morphogenesis through TGIF/Smad Complex-Mediated CRMP2 Suppression.

PubMed

Nakashima, Hideyuki; Tsujimura, Keita; Irie, Koichiro; Ishizu, Masataka; Pan, Miao; Kameda, Tomonori; Nakashima, Kinichi

2018-05-16

Functional neuronal connectivity requires proper neuronal morphogenesis and its dysregulation causes neurodevelopmental diseases. Transforming growth factor-β (TGF-β) family cytokines play pivotal roles in development, but little is known about their contribution to morphological development of neurons. Here we show that the Smad-dependent canonical signaling of TGF-β family cytokines negatively regulates neuronal morphogenesis during brain development. Mechanistically, activated Smads form a complex with transcriptional repressor TG-interacting factor (TGIF), and downregulate the expression of a neuronal polarity regulator, collapsin response mediator protein 2. We also demonstrate that TGF-β family signaling inhibits neurite elongation of human induced pluripotent stem cell-derived neurons. Furthermore, the expression of TGF-β receptor 1, Smad4, or TGIF, which have mutations found in patients with neurodevelopmental disorders, disrupted neuronal morphogenesis in both mouse (male and female) and human (female) neurons. Together, these findings suggest that the regulation of neuronal morphogenesis by an evolutionarily conserved function of TGF-β signaling is involved in the pathogenesis of neurodevelopmental diseases. SIGNIFICANCE STATEMENT Canonical transforming growth factor-β (TGF-β) signaling plays a crucial role in multiple organ development, including brain, and mutations in components of the signaling pathway associated with several human developmental disorders. In this study, we found that Smads/TG-interacting factor-dependent canonical TGF-β signaling regulates neuronal morphogenesis through the suppression of collapsin response mediator protein-2 (CRMP2) expression during brain development, and that function of this signaling is evolutionarily conserved in the mammalian brain. Mutations in canonical TGF-β signaling factors identified in patients with neurodevelopmental disorders disrupt the morphological development of neurons. Thus, our results suggest that proper control of TGF-β/Smads/CRMP2 signaling pathways is critical for the precise execution of neuronal morphogenesis, whose impairment eventually results in neurodevelopmental disorders. Copyright © 2018 the authors 0270-6474/18/384791-20$15.00/0.

Dopamine is produced in the rat spinal cord and regulates micturition reflex after spinal cord injury

PubMed Central

Hou, Shaoping; Carson, David M.; Wu, Di; Klaw, Michelle C.; Houlé, John D.; Tom, Veronica J.

2016-01-01

Dopamine (DA) neurons in the mammalian central nervous system are thought to be restricted to the brain. DA-mediated regulation of urinary activity is considered to occur through an interaction between midbrain DA neurons and the pontine micturition center. Here we show that DA is produced in the rat spinal cord and modulates the bladder reflex. We observed numerous tyrosine hydroxylase (TH)+ neurons in the autonomic nuclei and superficial dorsal horn in L6–S3 spinal segments. These neurons are dopamine-β-hydroxylase (DBH)− and some contain detectable dopamine decarboxylase (DDC), suggesting their capacity to produce DA. Interestingly, following a complete thoracic spinal cord injury (SCI) to interrupt supraspinal projections, more TH+ neurons emerged in the lumbosacral spinal cord, coincident with a sustained, low level of DA expression there and a partially recovered micturition reflex. Non-selective blockade of spinal DA receptors reduced bladder activity whereas activation of spinal D2-like receptors increased bladder activity and facilitated voiding. Additionally, depletion of lumbosacral TH+ neurons with 6-hydroxydopamine (6-OHDA) decreased bladder non-voiding contractions and voiding efficiency. Furthermore, injecting the transsynaptic neuronal tracer pseudorabies virus (PRV) into the bladder detrusor labeled TH+ cells in the lumbosacral cord, confirming their involvement in spinal micturition reflex circuits. These results illustrate that DA is synthesized in the rat spinal cord; plasticity of lumbosacral TH+ neurons following SCI may contribute to DA expression and modulate the spinal bladder reflex. Thus, spinally-derived DA and receptors could be a novel therapeutic target to improve micturition recovery after SCI. PMID:26655672

Dopamine is produced in the rat spinal cord and regulates micturition reflex after spinal cord injury.

PubMed

Hou, Shaoping; Carson, David M; Wu, Di; Klaw, Michelle C; Houlé, John D; Tom, Veronica J

2016-11-01

Dopamine (DA) neurons in the mammalian central nervous system are thought to be restricted to the brain. DA-mediated regulation of urinary activity is considered to occur through an interaction between midbrain DA neurons and the pontine micturition center. Here we show that DA is produced in the rat spinal cord and modulates the bladder reflex. We observed numerous tyrosine hydroxylase (TH) + neurons in the autonomic nuclei and superficial dorsal horn in L6-S3 spinal segments. These neurons are dopamine-β-hydroxylase (DBH) - and some contain detectable dopamine decarboxylase (DDC), suggesting their capacity to produce DA. Interestingly, following a complete thoracic spinal cord injury (SCI) to interrupt supraspinal projections, more TH + neurons emerged in the lumbosacral spinal cord, coincident with a sustained, low level of DA expression there and a partially recovered micturition reflex. Non-selective blockade of spinal DA receptors reduced bladder activity whereas activation of spinal D 2 -like receptors increased bladder activity and facilitated voiding. Additionally, depletion of lumbosacral TH + neurons with 6-hydroxydopamine (6-OHDA) decreased bladder non-voiding contractions and voiding efficiency. Furthermore, injecting the transsynaptic neuronal tracer pseudorabies virus (PRV) into the bladder detrusor labeled TH + cells in the lumbosacral cord, confirming their involvement in spinal micturition reflex circuits. These results illustrate that DA is synthesized in the rat spinal cord; plasticity of lumbosacral TH + neurons following SCI may contribute to DA expression and modulate the spinal bladder reflex. Thus, spinally-derived DA and receptors could be a novel therapeutic target to improve micturition recovery after SCI. Published by Elsevier Inc.

The GABA(A) receptor RDL acts in peptidergic PDF neurons to promote sleep in Drosophila.

PubMed

Chung, Brian Y; Kilman, Valerie L; Keath, J Russel; Pitman, Jena L; Allada, Ravi

2009-03-10

Sleep is regulated by a circadian clock that times sleep and wake to specific times of day and a homeostat that drives sleep as a function of prior wakefulness. To analyze the role of the circadian clock, we have used the fruit fly Drosophila. Flies display the core behavioral features of sleep, including relative immobility, elevated arousal thresholds, and homeostatic regulation. We assessed sleep-wake modulation by a core set of circadian pacemaker neurons that express the neuropeptide PDF. We find that disruption of PDF function increases sleep during the late night in light:dark and the first subjective day of constant darkness. Flies deploy genetic and neurotransmitter pathways to regulate sleep that are similar to those of their mammalian counterparts, including GABA. We find that RNA interference-mediated knockdown of the GABA(A) receptor gene, Resistant to dieldrin (Rdl), in PDF neurons reduces sleep, consistent with a role for GABA in inhibiting PDF neuron function. Patch-clamp electrophysiology reveals GABA-activated picrotoxin-sensitive chloride currents on PDF+ neurons. In addition, RDL is detectable most strongly on the large subset of PDF+ pacemaker neurons. These results suggest that GABAergic inhibition of arousal-promoting PDF neurons is an important mode of sleep-wake regulation in vivo.

Early induction of c-Myc is associated with neuronal cell death.

PubMed

Lee, Hyun-Pil; Kudo, Wataru; Zhu, Xiongwei; Smith, Mark A; Lee, Hyoung-gon

2011-11-14

Neuronal cell cycle activation has been implicated in neurodegenerative diseases such as Alzheimer's disease, while the initiating mechanism of cell cycle activation remains to be determined. Interestingly, our previous studies have shown that cell cycle activation by c-Myc (Myc) leads to neuronal cell death which suggests Myc might be a key regulator of cell cycle re-entry mediated neuronal cell death. However, the pattern of Myc expression in the process of neuronal cell death has not been addressed. To this end, we examined Myc induction by the neurotoxic agents camptothecin and amyloid-β peptide in a differentiated SH-SY5Y neuronal cell culture model. Myc expression was found to be significantly increased following either treatment and importantly, the induction of Myc preceded neuronal cell death suggesting it is an early event of neuronal cell death. Since ectopic expression of Myc in neurons causes the cell cycle activation and neurodegeneration in vivo, the current data suggest that induction of Myc by neurotoxic agents or other disease factors might be a key mediator in cell cycle activation and consequent cell death that is a feature of neurodegenerative diseases. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

The intracellular portion of GITR enhances NGF-promoted neurite growth through an inverse modulation of Erk and NF-κB signalling

PubMed Central

McKelvey, Laura; Gutierrez, Humberto; Nocentini, Giuseppe; Crampton, Sean J.; Davies, Alun M.; Riccardi, Carlo R.; O’keeffe, Gerard W.

2012-01-01

Summary NF-κB transcription factors play a key role in regulating the growth of neural processes in the developing PNS. Although several secreted proteins have been shown to activate NF-κB to inhibit the growth of developing sympathetic neurons, it is unknown how the endogenous level of NF-κB activity present in these neurons is restricted to allow neurite growth to occur during their normal development. Here we show that activation of the glucocorticoid-induced tumour necrosis factor receptor (GITR) inhibits NF-κB activation while promoting the activation of Erk in developing sympathetic neurons. Conversely, inhibition of GITR results in an increase in NF-κB dependent gene transcription and a decrease in Erk activation leading to a reduction in neurite growth. These findings show that GITR signalling can regulate the extent of sympathetic neurite growth through an inverse modulation of Erk and NF-κB signalling, which provides an optimal environment for NGF-promoted growth. PMID:23213379

Thalamic regulation of sucrose-seeking during unexpected reward omission

PubMed Central

Do-Monte, Fabricio H.; Minier-Toribio, Angélica; Quiñones-Laracuente, Kelvin; Medina-Colón, Estefanía M.; Quirk, Gregory J.

2017-01-01

SUMMARY The paraventricular nucleus of the thalamus (PVT) is thought to regulate behavioral responses under emotionally arousing conditions. Reward-associated cues activate PVT neurons, however, the specific PVT efferents regulating reward-seeking remain elusive. Using a cued sucrose-seeking task, we manipulated PVT activity under two emotionally distinct conditions: 1) when reward was available during the cue as expected, or 2) when reward was unexpectedly omitted during the cue. Pharmacological inactivation of the anterior PVT (aPVT), but not the posterior PVT, increased sucrose-seeking only when reward was omitted. Consistent with this, photoactivation of aPVT neurons abolished sucrose-seeking, and the firing of aPVT neurons differentiated reward availability. Photoinhibition of aPVT projections to the nucleus accumbens or to the amygdala increased or decreased, respectively, sucrose-seeking only when reward was omitted. Our findings suggest that PVT bidirectionally modulates sucrose-seeking under the negative (frustrative) conditions of reward omission. PMID:28426970

Cholesterol up-regulates neuronal G protein-gated inwardly rectifying potassium (GIRK) channel activity in the hippocampus

PubMed Central

Bukiya, Anna N.; Noskov, Sergei; Rosenhouse-Dantsker, Avia

2017-01-01

Hypercholesterolemia is a well known risk factor for the development of neurodegenerative disease. However, the underlying mechanisms are mostly unknown. In recent years, it has become increasingly evident that cholesterol-driven effects on physiology and pathophysiology derive from its ability to alter the function of a variety of membrane proteins including ion channels. Yet, the effect of cholesterol on G protein-gated inwardly rectifying potassium (GIRK) channels expressed in the brain is unknown. GIRK channels mediate the actions of inhibitory brain neurotransmitters. As a result, loss of GIRK function can enhance neuron excitability, whereas gain of GIRK function can reduce neuronal activity. Here we show that in rats on a high-cholesterol diet, cholesterol levels in hippocampal neurons are increased. We also demonstrate that cholesterol plays a critical role in modulating neuronal GIRK currents. Specifically, cholesterol enrichment of rat hippocampal neurons resulted in enhanced channel activity. In accordance, elevated currents upon cholesterol enrichment were also observed in Xenopus oocytes expressing GIRK2 channels, the primary GIRK subunit expressed in the brain. Furthermore, using planar lipid bilayers, we show that although cholesterol did not affect the unitary conductance of GIRK2, it significantly enhanced the frequency of channel openings. Last, combining computational and functional approaches, we identified two putative cholesterol-binding sites in the transmembrane domain of GIRK2. These findings establish that cholesterol plays a critical role in modulating GIRK activity in the brain. Because up-regulation of GIRK function can reduce neuronal activity, our findings may lead to novel approaches for prevention and therapy of cholesterol-driven neurodegenerative disease. PMID:28213520

Pannexins Are Potential New Players in the Regulation of Cerebral Homeostasis during Sleep-Wake Cycle

PubMed Central

Shestopalov, Valery I.; Panchin, Yuri; Tarasova, Olga S.; Gaynullina, Dina; Kovalzon, Vladimir M.

2017-01-01

During brain homeostasis, both neurons and astroglia release ATP that is rapidly converted to adenosine in the extracellular space. Pannexin-1 (Panx1) hemichannels represent a major conduit of non-vesicular ATP release from brain cells. Previous studies have shown that Panx1−/− mice possess severe disruption of the sleep-wake cycle. Here, we review experimental data supporting the involvement of pannexins (Panx) in the coordination of fundamental sleep-associated brain processes, such as neuronal activity and regulation of cerebrovascular tone. Panx1 hemichannels are likely implicated in the regulation of the sleep-wake cycle via an indirect effect of released ATP on adenosine receptors and through interaction with other somnogens, such as IL-1β, TNFα and prostaglandin D2. In addition to the recently established role of Panx1 in the regulation of endothelium-dependent arterial dilation, similar signaling pathways are the major cellular component of neurovascular coupling. The new discovered role of Panx in sleep regulation may have broad implications in coordinating neuronal activity and homeostatic housekeeping processes during the sleep-wake cycle. PMID:28769767

Pannexins Are Potential New Players in the Regulation of Cerebral Homeostasis during Sleep-Wake Cycle.

PubMed

Shestopalov, Valery I; Panchin, Yuri; Tarasova, Olga S; Gaynullina, Dina; Kovalzon, Vladimir M

2017-01-01

During brain homeostasis, both neurons and astroglia release ATP that is rapidly converted to adenosine in the extracellular space. Pannexin-1 (Panx1) hemichannels represent a major conduit of non-vesicular ATP release from brain cells. Previous studies have shown that Panx1 -/- mice possess severe disruption of the sleep-wake cycle. Here, we review experimental data supporting the involvement of pannexins (Panx) in the coordination of fundamental sleep-associated brain processes, such as neuronal activity and regulation of cerebrovascular tone. Panx1 hemichannels are likely implicated in the regulation of the sleep-wake cycle via an indirect effect of released ATP on adenosine receptors and through interaction with other somnogens, such as IL-1β, TNFα and prostaglandin D2. In addition to the recently established role of Panx1 in the regulation of endothelium-dependent arterial dilation, similar signaling pathways are the major cellular component of neurovascular coupling. The new discovered role of Panx in sleep regulation may have broad implications in coordinating neuronal activity and homeostatic housekeeping processes during the sleep-wake cycle.

PINK1-Mediated Phosphorylation of Parkin Boosts Parkin Activity in Drosophila

PubMed Central

Shiba-Fukushima, Kahori; Inoshita, Tsuyoshi; Hattori, Nobutaka; Imai, Yuzuru

2014-01-01

Two genes linked to early onset Parkinson's disease, PINK1 and Parkin, encode a protein kinase and a ubiquitin-ligase, respectively. Both enzymes have been suggested to support mitochondrial quality control. We have reported that Parkin is phosphorylated at Ser65 within the ubiquitin-like domain by PINK1 in mammalian cultured cells. However, it remains unclear whether Parkin phosphorylation is involved in mitochondrial maintenance and activity of dopaminergic neurons in vivo. Here, we examined the effects of Parkin phosphorylation in Drosophila, in which the phosphorylation residue is conserved at Ser94. Morphological changes of mitochondria caused by the ectopic expression of wild-type Parkin in muscle tissue and brain dopaminergic neurons disappeared in the absence of PINK1. In contrast, phosphomimetic Parkin accelerated mitochondrial fragmentation or aggregation and the degradation of mitochondrial proteins regardless of PINK1 activity, suggesting that the phosphorylation of Parkin boosts its ubiquitin-ligase activity. A non-phosphorylated form of Parkin fully rescued the muscular mitochondrial degeneration due to the loss of PINK1 activity, whereas the introduction of the non-phosphorylated Parkin mutant in Parkin-null flies led to the emergence of abnormally fused mitochondria in the muscle tissue. Manipulating the Parkin phosphorylation status affected spontaneous dopamine release in the nerve terminals of dopaminergic neurons, the survivability of dopaminergic neurons and flight activity. Our data reveal that Parkin phosphorylation regulates not only mitochondrial function but also the neuronal activity of dopaminergic neurons in vivo, suggesting that the appropriate regulation of Parkin phosphorylation is important for muscular and dopaminergic functions. PMID:24901221

Near infrared radiation protects against oxygen-glucose deprivation-induced neurotoxicity by down-regulating neuronal nitric oxide synthase (nNOS) activity in vitro.

PubMed

Yu, Zhanyang; Li, Zhaoyu; Liu, Ning; Jizhang, Yunneng; McCarthy, Thomas J; Tedford, Clark E; Lo, Eng H; Wang, Xiaoying

2015-06-01

Near infrared radiation (NIR) has been shown to be neuroprotective against neurological diseases including stroke and brain trauma, but the underlying mechanisms remain poorly understood. In the current study we aimed to investigate the hypothesis that NIR may protect neurons by attenuating oxygen-glucose deprivation (OGD)-induced nitric oxide (NO) production and modulating cell survival/death signaling. Primary mouse cortical neurons were subjected to 4 h OGD and NIR was applied at 2 h reoxygenation. OGD significantly increased NO level in primary neurons compared to normal control, which was significantly ameliorated by NIR at 5 and 30 min post-NIR. Neither OGD nor NIR significantly changed neuronal nitric oxide synthase (nNOS) mRNA or total protein levels compared to control groups. However, OGD significantly increased nNOS activity compared to normal control, and this effect was significantly diminished by NIR. Moreover, NIR significantly ameliorated the neuronal death induced by S-Nitroso-N-acetyl-DL-penicillamine (SNAP), a NO donor. Finally, NIR significantly rescued OGD-induced suppression of p-Akt and Bcl-2 expression, and attenuated OGD-induced upregulation of Bax, BAD and caspase-3 activation. These results suggest NIR may protect against OGD at least partially through reducing NO production by down-regulating nNOS activity, and modulating cell survival/death signaling.

Down-regulation of MIF by NFκB under hypoxia accelerated neuronal loss during stroke

PubMed Central

Zhang, Si; Zis, Odysseus; Ly, Philip T. T.; Wu, Yili; Zhang, Shuting; Zhang, Mingming; Cai, Fang; Bucala, Richard; Shyu, Woei-Cherng; Song, Weihong

2014-01-01

Neuronal apoptosis is one of the major causes of poststroke neurological deficits. Inflammation during the acute phase of stroke results in nuclear translocation of NFκB in affected cells in the infarct area. Macrophage migration inhibitory factor (MIF) promotes cardiomyocyte survival in mice following heart ischemia. However, the role of MIF during stroke remains limited. In this study, we showed that MIF expression is down-regulated by 0.75 ± 0.10-fold of the control in the infarct area in the mouse brains. Two functional cis-acing NFκB response elements were identified in the human MIF promoter. Dual activation of hypoxia and NFκB signaling resulted in significant reduction of MIF promoter activity to 0.86 ± 0.01-fold of the control. Furthermore, MIF reduced caspase-3 activation and protected neurons from oxidative stress- and in vitro ischemia/reperfusion-induced apoptosis. H2O2 significantly induced cell death with 12.81 ± 0.58-fold increase of TUNEL-positive cells, and overexpression of MIF blocked the H2O2-induced cell death. Disruption of the MIF gene in MIF-knockout mice resulted in caspase-3 activation, neuronal loss, and increased infarct development during stroke in vivo. The infarct volume was increased from 6.51 ± 0.74% in the wild-type mice to 9.07 ± 0.66% in the MIF-knockout mice. Our study demonstrates that MIF exerts a neuronal protective effect and that down-regulation of MIF by NFκB-mediated signaling under hypoxia accelerates neuronal loss during stroke. Our results suggest that MIF is an important molecule for preserving a longer time window for stroke treatment, and strategies to maintain MIF expression at physiological level could have beneficial effects for stroke patients.—Zhang, S., Zis, O., Ly, P. T. T., Wu, Y., Zhang, S., Zhang, M., Cai, F., Bucala, R., Shyu, W.-C., Song, W. Down-regulation of MIF by NFκB under hypoxia accelerated neuronal loss during stroke. PMID:24970391

Glutamate-dependent ectodomain shedding of neuregulin-1 type II precursors in rat forebrain neurons.

PubMed

Iwakura, Yuriko; Wang, Ran; Inamura, Naoko; Araki, Kazuaki; Higashiyama, Shigeki; Takei, Nobuyuki; Nawa, Hiroyuki

2017-01-01

The neurotrophic factor neuregulin 1 (NRG1) regulates neuronal development, glial differentiation, and excitatory synapse maturation. NRG1 is synthesized as a membrane-anchored precursor and is then liberated by proteolytic processing or exocytosis. Mature NRG1 then binds to its receptors expressed by neighboring neurons or glial cells. However, the molecular mechanisms that govern this process in the nervous system are not defined in detail. Here we prepared neuron-enriched and glia-enriched cultures from embryonic rat neocortex to investigate the role of neurotransmitters that regulate the liberation/release of NRG1 from the membrane of neurons or glial cells. Using a two-site enzyme immunoassay to detect soluble NRG1, we show that, of various neurotransmitters, glutamate was the most potent inducer of NRG1 release in neuron-enriched cultures. NRG1 release in glia-enriched cultures was relatively limited. Furthermore, among glutamate receptor agonists, N-Methyl-D-Aspartate (NMDA) and kainate (KA), but not AMPA or tACPD, mimicked the effects of glutamate. Similar findings were acquired from analysis of the hippocampus of rats with KA-induced seizures. To evaluate the contribution of members of a disintegrin and metalloproteinase (ADAM) families to NRG1 release, we transfected primary cultures of neurons with cDNA vectors encoding NRG1 types I, II, or III precursors, each tagged with the alkaline phosphatase reporter. Analysis of alkaline phosphatase activity revealed that the NRG1 type II precursor was subjected to tumor necrosis factor-α-converting enzyme (TACE) / a Disintegrin And Metalloproteinase 17 (ADAM17) -dependent ectodomain shedding in a protein kinase C-dependent manner. These results suggest that glutamatergic neurotransmission positively regulates the ectodomain shedding of NRG1 type II precursors and liberates the active NRG1 domain in an activity-dependent manner.

The pro-differentiating role of miR-124: indicating the road to become a neuron.

PubMed

Maiorano, Nicola Antonio; Mallamaci, Antonello

2010-01-01

miRNAs are essential post-transcriptional modulators affecting cell identity and fate, with a central role in cellular and developmental processes. The brain-enriched neuronal specific miRNAs-124 has been identified as a promoter of neuronogenesis in various conditions, in vitro and in vivo, with a potential role in regulating also activities of post-mitotic neurons, such as synaptic plasticity and memory formation. In this point of view, we recapitulate the main experimental findings substantiating the positive correlation between miR-124 expression and neuronogenesis progression. Then, we describe the impact of miR-124 on the molecular network driving the profound changes which take place in differentiating neuronal cells. Finally, we consider the possibility of a post-transcriptional modulation of miR-124 biogenesis, which may finely regulate--in turn--the activities of miR-124 in neural precursor cells.

Transsynaptic trophic effects of steroid hormones in an avian model of adult brain plasticity

PubMed Central

Brenowitz, Eliot A.

2014-01-01

The avian song control system provides an excellent model for studying transsynaptic trophic effects of steroid sex hormones. Seasonal changes in systemic testosterone (T) and its metabolites regulate plasticity of this system. Steroids interact with the neurotrophin brain-derived neurotrophic factor (BDNF) to influence cellular processes of plasticity in nucleus HVC of adult birds, including the addition of newborn neurons. This interaction may also occur transsynpatically; T increases the synthesis of BDNF in HVC, and BDNF protein is then released by HVC neurons on to postsynaptic cells in nucleus RA where it has trophic effects on activity and morphology. Androgen action on RA neurons increases their activity and this has a retrograde trophic effect on the addition of new neurons to HVC. The functional linkage of sex steroids to BDNF may be of adaptive value in regulating the trophic effects of the neurotrophin and coordinating circuit function in reproductively relevant contexts. PMID:25285401

Ghrelin Induces Leptin Resistance by Activation of Suppressor of Cytokine Signaling 3 Expression in Male Rats: Implications in Satiety Regulation

PubMed Central

Heldsinger, Andrea; Grabauskas, Gintautas; Wu, Xiaoyin; Zhou, ShiYi; Lu, Yuanxu; Song, Il

2014-01-01

The anorexigenic adipocyte-derived hormone leptin and the orexigenic hormone ghrelin act in opposition to regulate feeding behavior via the vagal afferent pathways. The mechanisms by which ghrelin exerts its inhibitory effects on leptin are unknown. We hypothesized that ghrelin activates the exchange protein activated by cAMP (Epac), inducing increased SOCS3 expression, which negatively affects leptin signal transduction and neuronal firing in nodose ganglia (NG) neurons. We showed that 91 ± 3% of leptin receptor (LRb) –bearing neurons contained ghrelin receptors (GHS-R1a) and that ghrelin significantly inhibited leptin-stimulated STAT3 phosphorylation in rat NG neurons. Studies of the signaling cascades used by ghrelin showed that ghrelin caused a significant increase in Epac and suppressor of cytokine signaling 3 (SOCS3) expression in cultured rat NG neurons. Transient transfection of cultured NG neurons to silence SOCS3 and Epac genes reversed the inhibitory effects of ghrelin on leptin-stimulated STAT3 phosphorylation. Patch-clamp studies and recordings of single neuronal discharges of vagal primary afferent neurons showed that ghrelin markedly inhibited leptin-stimulated neuronal firing, an action abolished by silencing SOCS3 expression in NG. Plasma ghrelin levels increased significantly during fasting. This was accompanied by enhanced SOCS3 expression in the NG and prevented by treatment with a ghrelin antagonist. Feeding studies showed that silencing SOCS3 expression in the NG reduced food intake evoked by endogenous leptin. We conclude that ghrelin exerts its inhibitory effects on leptin-stimulated neuronal firing by increasing SOCS3 expression. The SOCS3 signaling pathway plays a pivotal role in ghrelin's inhibitory effect on STAT3 phosphorylation, neuronal firing, and feeding behavior. PMID:25060362

Localization and distribution of neurons that co-express xeroderma pigmentosum-A and epidermal growth factor receptor within Rosenthal's canal.

PubMed

Guthrie, O'neil W

2015-10-01

Xeroderma pigmentosum-A (XPA) is a C4-type zinc-finger scaffolding protein that regulates the removal of bulky-helix distorting DNA damage products from the genome. Phosphorylation of serine residues within the XPA protein is associated with improved protection of genomic DNA and cell death resistance. Therefore, kinase signaling is one important mechanism for regulating the protective function of XPA. Previous experiments have shown that spiral ganglion neurons (SGNs) may mobilize XPA as a general stress response to chemical and physical ototoxicants. Therapeutic optimization of XPA via kinase signaling could serve as a means to improve DNA repair capacity within neurons following injury. The kinase signaling activity of the epidermal growth factor receptor (EGFR) has been shown in tumor cell lines to increase the repair of DNA damage products that are primarily repaired by XPA. Such observations suggest that EGFR may regulate the protective function of XPA. However, it is not known whether SGNs in particular or neurons in general could co-express XPA and EGFR. In the current study gene and protein expression of XPA and EGFR were determined from cochlear homogenates. Immunofluorescence assays were then employed to localize neurons expressing both EGFR and XPA within the ganglion. This work was then confirmed with double-immunohistochemistry. Rosenthal's canal served as the reference space in these experiments and design-based stereology was employed in first-order stereology quantification of immunoreactive neurons. The results confirmed that a population of SGNs that constitutively express XPA may also express the EGFR. These results provide the basis for future experiments designed to therapeutically manipulate the EGFR in order to regulate XPA activity and restore gene function in neurons following DNA damage. Copyright © 2015 Elsevier GmbH. All rights reserved.

Pharmacogenetic stimulation of neuronal activity increases myelination in an axon-specific manner.

PubMed

Mitew, Stanislaw; Gobius, Ilan; Fenlon, Laura R; McDougall, Stuart J; Hawkes, David; Xing, Yao Lulu; Bujalka, Helena; Gundlach, Andrew L; Richards, Linda J; Kilpatrick, Trevor J; Merson, Tobias D; Emery, Ben

2018-01-22

Mounting evidence suggests that neuronal activity influences myelination, potentially allowing for experience-driven modulation of neural circuitry. The degree to which neuronal activity is capable of regulating myelination at the individual axon level is unclear. Here we demonstrate that stimulation of somatosensory axons in the mouse brain increases proliferation and differentiation of oligodendrocyte progenitor cells (OPCs) within the underlying white matter. Stimulated axons display an increased probability of being myelinated compared to neighboring non-stimulated axons, in addition to being ensheathed with thicker myelin. Conversely, attenuating neuronal firing reduces axonal myelination in a selective activity-dependent manner. Our findings reveal that the process of selecting axons for myelination is strongly influenced by the relative activity of individual axons within a population. These observed cellular changes are consistent with the emerging concept that adaptive myelination is a key mechanism for the fine-tuning of neuronal circuitry in the mammalian CNS.

Asynchronous Cholinergic Drive Correlates with Excitation-Inhibition Imbalance via a Neuronal Ca2+ Sensor Protein.

PubMed

Zhou, Keming; Cherra, Salvatore J; Goncharov, Alexandr; Jin, Yishi

2017-05-09

Excitation-inhibition imbalance in neural networks is widely linked to neurological and neuropsychiatric disorders. However, how genetic factors alter neuronal activity, leading to excitation-inhibition imbalance, remains unclear. Here, using the C. elegans locomotor circuit, we examine how altering neuronal activity for varying time periods affects synaptic release pattern and animal behavior. We show that while short-duration activation of excitatory cholinergic neurons elicits a reversible enhancement of presynaptic strength, persistent activation results to asynchronous and reduced cholinergic drive, inducing imbalance between endogenous excitation and inhibition. We find that the neuronal calcium sensor protein NCS-2 is required for asynchronous cholinergic release in an activity-dependent manner and dampens excitability of inhibitory neurons non-cell autonomously. The function of NCS-2 requires its Ca 2+ binding and membrane association domains. These results reveal a synaptic mechanism implicating asynchronous release in regulation of excitation-inhibition balance. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

Overexpression of cypin alters dendrite morphology, single neuron activity, and network properties via distinct mechanisms

NASA Astrophysics Data System (ADS)

Rodríguez, Ana R.; O'Neill, Kate M.; Swiatkowski, Przemyslaw; Patel, Mihir V.; Firestein, Bonnie L.

2018-02-01

Objective. This study investigates the effect that overexpression of cytosolic PSD-95 interactor (cypin), a regulator of synaptic PSD-95 protein localization and a core regulator of dendrite branching, exerts on the electrical activity of rat hippocampal neurons and networks. Approach. We cultured rat hippocampal neurons and used lipid-mediated transfection and lentiviral gene transfer to achieve high levels of cypin or cypin mutant (cypinΔPDZ PSD-95 non-binding) expression cellularly and network-wide, respectively. Main results. Our analysis revealed that although overexpression of cypin and cypinΔPDZ increase dendrite numbers and decrease spine density, cypin and cypinΔPDZ distinctly regulate neuronal activity. At the single cell level, cypin promotes decreases in bursting activity while cypinΔPDZ reduces sEPSC frequency and further decreases bursting compared to cypin. At the network level, by using the Fano factor as a measure of spike count variability, cypin overexpression results in an increase in variability of spike count, and this effect is abolished when cypin cannot bind PSD-95. This variability is also dependent on baseline activity levels and on mean spike rate over time. Finally, our spike sorting data show that overexpression of cypin results in a more complex distribution of spike waveforms and that binding to PSD-95 is essential for this complexity. Significance. Our data suggest that dendrite morphology does not play a major role in cypin action on electrical activity.

Control of male sexual behavior and sexual orientation in Drosophila by the fruitless gene.

PubMed

Ryner, L C; Goodwin, S F; Castrillon, D H; Anand, A; Villella, A; Baker, B S; Hall, J C; Taylor, B J; Wasserman, S A

1996-12-13

Sexual orientation and courtship behavior in Drosophila are regulated by fruitless (fru), the first gene in a branch of the sex-determination hierarchy functioning specifically in the central nervous system (CNS). The phenotypes of new fru mutants encompass nearly all aspects of male sexual behavior. Alternative splicing of fru transcripts produces sex-specific proteins belonging to the BTB-ZF family of transcriptional regulators. The sex-specific fru products are produced in only about 500 of the 10(5) neurons that comprise the CNS. The properties of neurons expressing these fru products suggest that fru specifies the fates or activities of neurons that carry out higher order control functions to elicit and coordinate the activities comprising male courtship behavior.

Comparative analysis of cis-regulation following stroke and seizures in subspaces of conserved eigensystems

PubMed Central

2010-01-01

Background It is often desirable to separate effects of different regulators on gene expression, or to identify effects of the same regulator across several systems. Here, we focus on the rat brain following stroke or seizures, and demonstrate how the two tasks can be approached simultaneously. Results We applied SVD to time-series gene expression datasets from the rat experimental models of stroke and seizures. We demonstrate conservation of two eigensystems, reflecting inflammation and/or apoptosis (eigensystem 2) and neuronal synaptic activity (eigensystem 3), between the stroke and seizures. We analyzed cis-regulation of gene expression in the subspaces of the conserved eigensystems. Bayesian networks analysis was performed separately for either experimental model, with cross-system validation of the highest-ranking features. In this way, we correctly re-discovered the role of AP1 in the regulation of apoptosis, and the involvement of Creb and Egr in the regulation of synaptic activity-related genes. We identified a novel antagonistic effect of the motif recognized by the nuclear matrix attachment region-binding protein Satb1 on AP1-driven transcriptional activation, suggesting a link between chromatin loop structure and gene activation by AP1. The effects of motifs binding Satb1 and Creb on gene expression in brain conform to the assumption of the linear response model of gene regulation. Our data also suggest that numerous enhancers of neuronal-specific genes are important for their responsiveness to the synaptic activity. Conclusion Eigensystems conserved between stroke and seizures separate effects of inflammation/apoptosis and neuronal synaptic activity, exerted by different transcription factors, on gene expression in rat brain. PMID:20565733

Akt/PKB Controls the Activity-Dependent Bulk Endocytosis of Synaptic Vesicles

PubMed Central

Smillie, Karen J; Cousin, Michael A

2012-01-01

Activity-dependent bulk endocytosis (ADBE) is the dominant SV endocytosis mode during intense neuronal activity. The dephosphorylation of Ser774 on dynamin I is essential for triggering of ADBE, as is its subsequent rephosphorylation by glycogen synthase kinase 3 (GSK3). We show that in primary cultures of cerebellar granule neurons the protein kinase Akt phosphorylates GSK3 during intense neuronal activity, ensuring that GSK3 is inactive during intense stimulation to aid dynamin I dephosphorylation. Furthermore, when a constitutively active form of Akt was overexpressed in primary neuronal cultures, ADBE was inhibited with no effect on clathrin-mediated endocytosis. Thus Akt has two major regulatory roles (i) to ensure efficient dynamin I dephosphorylation via acute activity-dependent inhibition of GSK3 and (ii) to negatively regulate ADBE when activated in the longer term. This is the first demonstration of a role for Akt in SV recycling and suggests a key role for this protein kinase in modulating synaptic strength during elevated neuronal activity. PMID:22487004

Dynamics and function of distal regulatory elements during neurogenesis and neuroplasticity

PubMed Central

Thakurela, Sudhir; Sahu, Sanjeeb Kumar; Garding, Angela; Tiwari, Vijay K.

2015-01-01

Gene regulation in mammals involves a complex interplay between promoters and distal regulatory elements that function in concert to drive precise spatiotemporal gene expression programs. However, the dynamics of the distal gene regulatory landscape and its function in the transcriptional reprogramming that underlies neurogenesis and neuronal activity remain largely unknown. Here, we performed a combinatorial analysis of genome-wide data sets for chromatin accessibility (FAIRE-seq) and the enhancer mark H3K27ac, revealing the highly dynamic nature of distal gene regulation during neurogenesis, which gets progressively restricted to distinct genomic regions as neurons acquire a post-mitotic, terminally differentiated state. We further find that the distal accessible and active regions serve as target sites for distinct transcription factors that function in a stage-specific manner to contribute to the transcriptional program underlying neuronal commitment and maturation. Mature neurons respond to a sustained activity of NMDA receptors by epigenetic reprogramming at a large number of distal regulatory regions as well as dramatic reorganization of super-enhancers. Such massive remodeling of the distal regulatory landscape in turn results in a transcriptome that confers a transient loss of neuronal identity and gain of cellular plasticity. Furthermore, NMDA receptor activity also induces many novel prosurvival genes that function in neuroprotective pathways. Taken together, these findings reveal the dynamics of the distal regulatory landscape during neurogenesis and uncover novel regulatory elements that function in concert with epigenetic mechanisms and transcription factors to generate the transcriptome underlying neuronal development and activity. PMID:26170447

The role of GluN2A and GluN2B NMDA receptor subunits in AgRP and POMC neurons on body weight and glucose homeostasis.

PubMed

Üner, Aykut; Gonçalves, Gabriel H M; Li, Wenjing; Porceban, Matheus; Caron, Nicole; Schönke, Milena; Delpire, Eric; Sakimura, Kenji; Bjørbæk, Christian

2015-10-01

Hypothalamic agouti-related peptide (AgRP) and pro-opiomelanocortin (POMC) expressing neurons play critical roles in control of energy balance. Glutamatergic input via n-methyl-d-aspartate receptors (NMDARs) is pivotal for regulation of neuronal activity and is required in AgRP neurons for normal body weight homeostasis. NMDARs typically consist of the obligatory GluN1 subunit and different GluN2 subunits, the latter exerting crucial differential effects on channel activity and neuronal function. Currently, the role of specific GluN2 subunits in AgRP and POMC neurons on whole body energy and glucose balance is unknown. We used the cre-lox system to genetically delete GluN2A or GluN2B only from AgRP or POMC neurons in mice. Mice were then subjected to metabolic analyses and assessment of AgRP and POMC neuronal function through morphological studies. We show that loss of GluN2B from AgRP neurons reduces body weight, fat mass, and food intake, whereas GluN2B in POMC neurons is not required for normal energy balance control. GluN2A subunits in either AgRP or POMC neurons are not required for regulation of body weight. Deletion of GluN2B reduces the number of AgRP neurons and decreases their dendritic length. In addition, loss of GluN2B in AgRP neurons of the morbidly obese and severely diabetic leptin-deficient Lep (ob/ob) mice does not affect body weight and food intake but, remarkably, leads to full correction of hyperglycemia. Lep (ob/ob) mice lacking GluN2B in AgRP neurons are also more sensitive to leptin's anti-obesity actions. GluN2B-containing NMDA receptors in AgRP neurons play a critical role in central control of body weight homeostasis and blood glucose balance via mechanisms that likely involve regulation of AgRP neuronal survival and structure, and modulation of hypothalamic leptin action.

Negative Regulation of Leptin-induced Reactive Oxygen Species (ROS) Formation by Cannabinoid CB1 Receptor Activation in Hypothalamic Neurons.

PubMed

Palomba, Letizia; Silvestri, Cristoforo; Imperatore, Roberta; Morello, Giovanna; Piscitelli, Fabiana; Martella, Andrea; Cristino, Luigia; Di Marzo, Vincenzo

2015-05-29

The adipocyte-derived, anorectic hormone leptin was recently shown to owe part of its regulatory effects on appetite-regulating hypothalamic neuropeptides to the elevation of reactive oxygen species (ROS) levels in arcuate nucleus (ARC) neurons. Leptin is also known to exert a negative regulation on hypothalamic endocannabinoid levels and hence on cannabinoid CB1 receptor activity. Here we investigated the possibility of a negative regulation by CB1 receptors of leptin-mediated ROS formation in the ARC. Through pharmacological and molecular biology experiments we report data showing that leptin-induced ROS accumulation is 1) blunted by arachidonyl-2'-chloroethylamide (ACEA) in a CB1-dependent manner in both the mouse hypothalamic cell line mHypoE-N41 and ARC neuron primary cultures, 2) likewise blocked by a peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist, troglitazone, in a manner inhibited by T0070907, a PPAR-γ antagonist that also inhibited the ACEA effect on leptin, 3) blunted under conditions of increased endocannabinoid tone due to either pharmacological or genetic inhibition of endocannabinoid degradation in mHypoE-N41 and primary ARC neuronal cultures from MAGL(-/-) mice, respectively, and 4) associated with reduction of both PPAR-γ and catalase activity, which are reversed by both ACEA and troglitazone. We conclude that CB1 activation reverses leptin-induced ROS formation and hence possibly some of the ROS-mediated effects of the hormone by preventing PPAR-γ inhibition by leptin, with subsequent increase of catalase activity. This mechanism might underlie in part CB1 orexigenic actions under physiopathological conditions accompanied by elevated hypothalamic endocannabinoid levels. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Kinases of eIF2a Switch Translation of mRNA Subset during Neuronal Plasticity

PubMed Central

Chesnokova, Ekaterina; Bal, Natalia

2017-01-01

Compared to other types of cells, neurons express the largest number of diverse mRNAs, including neuron-specific ones. This mRNA diversity is required for neuronal function, memory storage, maintenance and retrieval. Regulation of translation in neurons is very complicated and involves various proteins. Some proteins, implementing translational control in other cell types, are used by neurons for synaptic plasticity. In this review, we discuss the neuron-specific activity of four kinases: protein kinase R (PKR), PKR-like endoplasmic reticulum kinase (PERK), general control nonderepressible 2 kinase (GCN2), and heme-reguated eIF2α kinase (HRI), the substrate for which is α-subunit of eukaryotic initiation factor 2 (eIF2α). Phosphorylation of eIF2α is necessary for the cell during stress conditions, such as lack of amino acids, energy stress or viral infection. We propose that, during memory formation, neurons use some mechanisms similar to those involved in the cellular stress. The four eIF2α kinases regulate translation of certain mRNAs containing upstream open reading frames (uORFs). These mRNAs encode proteins involved in the processes of long-term potentiation (LTP) or long-term depression (LTD). The review examines some neuronal proteins for which translation regulation by eIF2 was suggested and checked experimentally. Of such proteins, we pay close attention to protein kinase Mζ, which is involved in memory storage and regulated at the translational level. PMID:29065505

Sodium Pumps Mediate Activity-Dependent Changes in Mammalian Motor Networks

PubMed Central

Picton, Laurence D.; Nascimento, Filipe; Broadhead, Matthew J.; Sillar, Keith T.

2017-01-01

Ubiquitously expressed sodium pumps are best known for maintaining the ionic gradients and resting membrane potential required for generating action potentials. However, activity- and state-dependent changes in pump activity can also influence neuronal firing and regulate rhythmic network output. Here we demonstrate that changes in sodium pump activity regulate locomotor networks in the spinal cord of neonatal mice. The sodium pump inhibitor, ouabain, increased the frequency and decreased the amplitude of drug-induced locomotor bursting, effects that were dependent on the presence of the neuromodulator dopamine. Conversely, activating the pump with the sodium ionophore monensin decreased burst frequency. When more “natural” locomotor output was evoked using dorsal-root stimulation, ouabain increased burst frequency and extended locomotor episode duration, whereas monensin slowed and shortened episodes. Decreasing the time between dorsal-root stimulation, and therefore interepisode interval, also shortened and slowed activity, suggesting that pump activity encodes information about past network output and contributes to feedforward control of subsequent locomotor bouts. Using whole-cell patch-clamp recordings from spinal motoneurons and interneurons, we describe a long-duration (∼60 s), activity-dependent, TTX- and ouabain-sensitive, hyperpolarization (∼5 mV), which is mediated by spike-dependent increases in pump activity. The duration of this dynamic pump potential is enhanced by dopamine. Our results therefore reveal sodium pumps as dynamic regulators of mammalian spinal motor networks that can also be affected by neuromodulatory systems. Given the involvement of sodium pumps in movement disorders, such as amyotrophic lateral sclerosis and rapid-onset dystonia parkinsonism, knowledge of their contribution to motor network regulation also has considerable clinical importance. SIGNIFICANCE STATEMENT The sodium pump is ubiquitously expressed and responsible for at least half of total brain energy consumption. The pumps maintain ionic gradients and the resting membrane potential of neurons, but increasing evidence suggests that activity- and state-dependent changes in pump activity also influence neuronal firing. Here we demonstrate that changes in sodium pump activity regulate locomotor output in the spinal cord of neonatal mice. We describe a sodium pump-mediated afterhyperpolarization in spinal neurons, mediated by spike-dependent increases in pump activity, which is affected by dopamine. Understanding how sodium pumps contribute to network regulation and are targeted by neuromodulators, including dopamine, has clinical relevance due to the role of the sodium pump in diseases, including amyotrophic lateral sclerosis, parkinsonism, epilepsy, and hemiplegic migraine. PMID:28123025

Activation state of the hyperpolarization-activated current modulates temperature-sensitivity of firing in locus coeruleus neurons from bullfrogs.

PubMed

Santin, Joseph M; Hartzler, Lynn K

2015-06-15

Locus coeruleus neurons of anuran amphibians contribute to breathing control and have spontaneous firing frequencies that, paradoxically, increase with cooling. We previously showed that cooling inhibits a depolarizing membrane current, the hyperpolarization-activated current (I h) in locus coeruleus neurons from bullfrogs, Lithobates catesbeianus (Santin JM, Watters KC, Putnam RW, Hartzler LK. Am J Physiol Regul Integr Comp Physiol 305: R1451-R1464, 2013). This suggests an unlikely role for I h in generating cold activation, but led us to hypothesize that inhibition of I h by cooling functions as a physiological brake to limit the cold-activated response. Using whole cell electrophysiology in brain slices, we employed 2 mM Cs(+) (an I h antagonist) to isolate the role of I h in spontaneous firing and cold activation in neurons recorded with either control or I h agonist (cyclic AMP)-containing artificial intracellular fluid. I h did not contribute to the membrane potential (V m) and spontaneous firing at 20°C. Although voltage-clamp analysis confirmed that cooling inhibits I h, its lack of involvement in setting baseline firing and V m precluded its ability to regulate cold activation as hypothesized. In contrast, neurons dialyzed with cAMP exhibited greater baseline firing frequencies at 20°C due to I h activation. Our hypothesis was supported when the starting level of I h was enhanced by elevating cAMP because cold activation was converted to more ordinary cold inhibition. These findings indicate that situations leading to enhancement of I h facilitate firing at 20°C, yet the hyperpolarization associated with inhibiting a depolarizing cation current by cooling blunts the net V m response to cooling to oppose normal cold-depolarizing factors. This suggests that the influence of I h activation state on neuronal firing varies in the poikilothermic neuronal environment. Copyright © 2015 the American Physiological Society.

Gut microbial products regulate murine gastrointestinal motility via Toll-like Receptor 4 signaling

PubMed Central

Anitha, Mallappa; Vijay-Kumar, Matam; Sitaraman, Shanthi V.; Gewirtz, Andrew T.; Srinivasan, Shanthi

2012-01-01

Background & Aims Altered gastrointestinal motility is associated with significant morbidity and health care costs. Toll-like receptors regulate intestinal homeostasis. We examined the roles of Toll-like receptor (TLR)4 signaling in survival of enteric neurons and gastrointestinal motility. Methods We assessed changes in intestinal motility by assessing stool frequency, bead expulsion, and isometric muscle recordings of colonic longitudinal muscle strips from mice that do not express TLR4 (Tlr4Lps-d or TLR4−/−) or Myd88 (Myd88−/−), in wild-type germ-free mice or wild-type mice depleted of the microbiota, and in mice with neural crest-specific deletion of Myd88 (Wnt1Cre+/−/Myd88fl/fl). We studied the effects of the TLR4 agonist lipopolysaccharide (LPS) on survival of cultured, immortalized fetal enteric neurons (IM-FEN) and enteric neuronal cells isolated from wild-type and Tlr4Lps-d mice at embryonic day 13.5. Results There was a significant delay in gastrointestinal motility and reduced numbers of nitrergic neurons in TLR4Lps-d, TLR4−/−, and Myd88−/− mice, compared with wild-type mice. A similar phenotype was observed in germ-free mice, mice depleted of intestinal microbiota, and Wnt1Cre+/−/Myd88fl/fl mice. Incubation of enteric neuronal cells with LPS led to activation of the transcription factor NF-κB and increased cell survival. Conclusions Interactions between enteric neurons and microbes increases neuron survival and gastrointestinal motility in mice. LPS activation of TLR4 and NF-κB appears to promote survival of enteric neurons. Factors that regulate TLR4 signaling by neurons might be developed to alter gastrointestinal motility. PMID:22732731

Differential regulation of ASICs and TRPV1 by zinc in rat bronchopulmonary sensory neurons.

PubMed

Vysotskaya, Zhanna V; Moss, Charles R; Gu, Qihai

2014-12-01

Zinc has been known to act as a signaling molecule that regulates a variety of neuronal functions. In this study, we aimed to study the effect of zinc on two populations of acid-sensitive ion channels, acid-sensing ion channels (ASICs), and transient receptor potential vanilloid receptor-1 (TRPV1), in vagal bronchopulmonary sensory neurons. Rat vagal sensory neurons innervating lungs and airways were retrogradely labeled with a fluorescent tracer. Whole-cell perforated patch-clamp recordings were carried out in primarily cultured bronchopulmonary sensory neurons. The acid-evoked ASIC and TRPV1 currents were measured and compared between before and after the zinc pretreatment. ASIC currents were induced by a pH drop from 7.4 to 6.8 or 6.5 in the presence of capsazepine (10 µM), a specific TRPV1 antagonist. Pretreatment with zinc (50 or 300 µM, 2 min) displayed different effects on the two distinct phenotypes of ASIC currents: a marked potentiation on ASIC channels with fast kinetics of activation and inactivation or no significant effect on ASIC currents with slow activation and inactivation. On the other hand, pretreatment with zinc significantly inhibited the acid (pH 5.5 or 5.3)-induced TRPV1 currents. The inhibition was abolished by intracellular chelation of zinc by TPEN (25 µM), indicating that intracellular accumulation of zinc was likely required for its inhibitory effect on TRPV1 channels. Our study showed that zinc differentially regulates the activities of ASICs and TRPV1 channels in rat vagal bronchopulmonary sensory neurons.

Metabolic reprogramming during neuronal differentiation from aerobic glycolysis to neuronal oxidative phosphorylation.

PubMed

Zheng, Xinde; Boyer, Leah; Jin, Mingji; Mertens, Jerome; Kim, Yongsung; Ma, Li; Ma, Li; Hamm, Michael; Gage, Fred H; Hunter, Tony

2016-06-10

How metabolism is reprogrammed during neuronal differentiation is unknown. We found that the loss of hexokinase (HK2) and lactate dehydrogenase (LDHA) expression, together with a switch in pyruvate kinase gene splicing from PKM2 to PKM1, marks the transition from aerobic glycolysis in neural progenitor cells (NPC) to neuronal oxidative phosphorylation. The protein levels of c-MYC and N-MYC, transcriptional activators of the HK2 and LDHA genes, decrease dramatically. Constitutive expression of HK2 and LDHA during differentiation leads to neuronal cell death, indicating that the shut-off aerobic glycolysis is essential for neuronal survival. The metabolic regulators PGC-1α and ERRγ increase significantly upon neuronal differentiation to sustain the transcription of metabolic and mitochondrial genes, whose levels are unchanged compared to NPCs, revealing distinct transcriptional regulation of metabolic genes in the proliferation and post-mitotic differentiation states. Mitochondrial mass increases proportionally with neuronal mass growth, indicating an unknown mechanism linking mitochondrial biogenesis to cell size.

An ALS-Associated Mutant SOD1 Rapidly Suppresses KCNT1 (Slack) Na+-Activated K+ Channels in Aplysia Neurons.

PubMed

Zhang, Yalan; Ni, Weiming; Horwich, Arthur L; Kaczmarek, Leonard K

2017-02-22

Mutations that alter levels of Slack (KCNT1) Na + -activated K + current produce devastating effects on neuronal development and neuronal function. We now find that Slack currents are rapidly suppressed by oligomers of mutant human Cu/Zn superoxide dismutase 1 (SOD1), which are associated with motor neuron toxicity in an inherited form of amyotrophic lateral sclerosis (ALS). We recorded from bag cell neurons of Aplysia californica , a model system to study neuronal excitability. We found that injection of fluorescent wild-type SOD1 (wt SOD1YFP) or monomeric mutant G85R SOD1YFP had no effect on net ionic currents measured under voltage clamp. In contrast, outward potassium currents were significantly reduced by microinjection of mutant G85R SOD1YFP that had been preincubated at 37°C or of cross-linked dimers of G85R SOD1YFP. Reduction of potassium current was also seen with multimeric G85R SOD1YFP of ∼300 kDa or >300 kDa that had been cross-linked. In current clamp recordings, microinjection of cross-linked 300 kDa increased excitability by depolarizing the resting membrane potential, and decreasing the latency of action potentials triggered by depolarization. The effect of cross-linked 300 kDa on potassium current was reduced by removing Na + from the bath solution, or by knocking down levels of Slack using siRNA. It was also prevented by pharmacological inhibition of ASK1 (apoptosis signal-regulating kinase 1) or of c-Jun N-terminal kinase, but not by an inhibitor of p38 mitogen-activated protein kinase. These results suggest that soluble mutant SOD1 oligomers rapidly trigger a kinase pathway that regulates the activity of Na + -activated K + channels in neurons. SIGNIFICANCE STATEMENT Slack Na + -activated K + channels (KCNT1, K Na 1.1) regulate neuronal excitability but are also linked to cytoplasmic signaling pathways that control neuronal protein translation. Mutations that alter the amplitude of these currents have devastating effects on neuronal development and function. We find that injection of oligomers of mutant superoxide dismutase 1 (SOD1) into the cytoplasm of invertebrate neurons rapidly suppresses these Na + -activated K + currents and that this effect is mediated by a MAP kinase cascade, including ASK1 and c-Jun N-terminal kinase. Because amyotrophic lateral sclerosis is a fatal adult-onset neurodegenerative disease produced by mutations in SOD1 that cause the enzyme to form toxic oligomers, our findings suggest that suppression of Slack channels may be an early step in the progression of the disease. Copyright © 2017 the authors 0270-6474/17/372258-08$15.00/0.

Acute Knockdown of Kv4.1 Regulates Repetitive Firing Rates and Clock Gene Expression in the Suprachiasmatic Nucleus and Daily Rhythms in Locomotor Behavior

PubMed Central

Hermanstyne, Tracey O.; Mellor, Rebecca L.

2017-01-01

Abstract Rapidly activating and inactivating A-type K+ currents (IA) encoded by Kv4.2 and Kv4.3 pore-forming (α) subunits of the Kv4 subfamily are key regulators of neuronal excitability. Previous studies have suggested a role for Kv4.1 α-subunits in regulating the firing properties of mouse suprachiasmatic nucleus (SCN) neurons. To test this, we utilized an RNA-interference strategy to knockdown Kv4.1, acutely and selectively, in the SCN. Current-clamp recordings revealed that the in vivo knockdown of Kv4.1 significantly (p < 0.0001) increased mean ± SEM repetitive firing rates in SCN neurons during the day (6.4 ± 0.5 Hz) and at night (4.3 ± 0.6 Hz), compared with nontargeted shRNA-expressing SCN neurons (day: 3.1 ± 0.5 Hz; night: 1.6 ± 0.3 Hz). IA was also significantly (p < 0.05) reduced in Kv4.1-targeted shRNA-expressing SCN neurons (day: 80.3 ± 11.8 pA/pF; night: 55.3 ± 7.7 pA/pF), compared with nontargeted shRNA-expressing (day: 121.7 ± 10.2 pA/pF; night: 120.6 ± 16.5 pA/pF) SCN neurons. The magnitude of the effect of Kv4.1-targeted shRNA expression on firing rates and IA was larger at night. In addition, Kv4.1-targeted shRNA expression significantly (p < 0.001) increased mean ± SEM nighttime input resistance (Rin; 2256 ± 166 MΩ), compared to nontargeted shRNA-expressing SCN neurons (1143 ± 93 MΩ). Additional experiments revealed that acute knockdown of Kv4.1 significantly (p < 0.01) shortened, by ∼0.5 h, the circadian period of spontaneous electrical activity, clock gene expression and locomotor activity demonstrating a physiological role for Kv4.1-encoded IA channels in regulating circadian rhythms in neuronal excitability and behavior. PMID:28560311

Acute Knockdown of Kv4.1 Regulates Repetitive Firing Rates and Clock Gene Expression in the Suprachiasmatic Nucleus and Daily Rhythms in Locomotor Behavior.

PubMed

Hermanstyne, Tracey O; Granados-Fuentes, Daniel; Mellor, Rebecca L; Herzog, Erik D; Nerbonne, Jeanne M

2017-01-01

Rapidly activating and inactivating A-type K + currents (I A ) encoded by Kv4.2 and Kv4.3 pore-forming (α) subunits of the Kv4 subfamily are key regulators of neuronal excitability. Previous studies have suggested a role for Kv4.1 α-subunits in regulating the firing properties of mouse suprachiasmatic nucleus (SCN) neurons. To test this, we utilized an RNA-interference strategy to knockdown Kv4.1, acutely and selectively, in the SCN. Current-clamp recordings revealed that the in vivo knockdown of Kv4.1 significantly ( p < 0.0001) increased mean ± SEM repetitive firing rates in SCN neurons during the day (6.4 ± 0.5 Hz) and at night (4.3 ± 0.6 Hz), compared with nontargeted shRNA-expressing SCN neurons (day: 3.1 ± 0.5 Hz; night: 1.6 ± 0.3 Hz). I A was also significantly ( p < 0.05) reduced in Kv4.1-targeted shRNA-expressing SCN neurons (day: 80.3 ± 11.8 pA/pF; night: 55.3 ± 7.7 pA/pF), compared with nontargeted shRNA-expressing (day: 121.7 ± 10.2 pA/pF; night: 120.6 ± 16.5 pA/pF) SCN neurons. The magnitude of the effect of Kv4.1-targeted shRNA expression on firing rates and I A was larger at night. In addition, Kv4.1-targeted shRNA expression significantly ( p < 0.001) increased mean ± SEM nighttime input resistance (R in ; 2256 ± 166 MΩ), compared to nontargeted shRNA-expressing SCN neurons (1143 ± 93 MΩ). Additional experiments revealed that acute knockdown of Kv4.1 significantly ( p < 0.01) shortened, by ∼0.5 h, the circadian period of spontaneous electrical activity, clock gene expression and locomotor activity demonstrating a physiological role for Kv4.1-encoded I A channels in regulating circadian rhythms in neuronal excitability and behavior.

Differential Expression and Regulation of Brain-Derived Neurotrophic Factor (BDNF) mRNA Isoforms in Brain Cells from Mecp2(308/y) Mouse Model.

PubMed

Rousseaud, Audrey; Delépine, Chloé; Nectoux, Juliette; Billuart, Pierre; Bienvenu, Thierry

2015-08-01

Rett syndrome (RTT) is a severe neurodevelopmental disease caused by mutations in methyl-CpG-binding protein 2 (MECP2), which encodes a transcriptional modulator of many genes including BDNF. BDNF comprises nine distinct promoter regions, each triggering the expression of a specific transcript. The role of this diversity of transcripts remains unknown. MeCP2 being highly expressed in neurons, RTT was initially considered as a neuronal disease. However, recent studies have shown that MeCP2 was also expressed in astrocytes. Though several studies explored Bdnf IV expression in Mecp2-deficient mice, the differential expression of Bdnf isoforms in Mecp2-deficient neurons and astrocytes was never studied. By using TaqMan technology and a mouse model expressing a truncated Mecp2 (Mecp2(308/y)), we firstly showed in neurons that Bdnf transcripts containing exon I, IIb, IIc, IV, and VI are prominently expressed, whereas in astrocytes, Bdnf transcript containing exon VI is preferentially expressed, suggesting a specific regulation of Bdnf expression at the cellular level. Secondly, we confirmed the repressive role of Mecp2 only on the expression of Bdnf VI in neurons. Our data suggested that the truncated Mecp2 protein maintains its function on Bdnf expression regulation in neurons and in astrocytes. Interestingly, we observed that Bdnf transcripts (I and IXA), regulated by neural activity induced by bicuculline in Mecp2(308/y) neurons, were not affected by histone deacetylase inhibition. In contrast, Bdnf transcripts (IIb, IIc, and VI), regulated by histone deacetylation, were not affected by bicuculline treatment in wild-type and Mecp2(308/y) neurons. All these results reflect the complexity of regulation of Bdnf gene.

Wogonin prevents rat dorsal root ganglion neurons death via inhibiting tunicamycin-induced ER stress in vitro.

PubMed

Xu, Shujuan; Zhao, Xin; Zhao, Quanlai; Zheng, Quan; Fang, Zhen; Yang, Xiaoming; Wang, Hong; Liu, Ping; Xu, Hongguang

2015-04-01

Wogonin is a natural flavonoid isolated from the root of Scutellaria baicalensis Georgi, which has been widely used in various research areas for its anti-oxidant, anti-inflammatory, and anti-cancer activities. It also presents a neuroprotective effect in the brain while encounters stress conditions, but the mechanisms controlling the neuroprotective effect of wogonin are not clear. In this study, we investigated the biomechanism underlying the neuroprotective effect of wogonin on rat dorsal root ganglion (DRG) neurons. Wogonin pre-treatment at 75 μM significantly increased the cell viability of DRG neurons and decreased the number of the propidium iodide-positive DRG neurons before the endoplasmic reticulum (ER) stress is being induced by tunicamycin (TUN) (0.75 μg/mL). In addition, Wogonin also inhibited the release of LDH and up-regulated the level of GSH. Furthermore, wogonin decreased the activation of ER stress-related molecules, including glucose-regulated protein 78 (GRP78), GRP94, C/EBP-homologous protein, active caspase12 and active caspase3, phosphorylation of pancreatic ER stress kinase, and eukaryotic initiation factor 2 alpha (eIF2α). In summary, our results indicated that wogonin could protect DRG neurons against TUN-induced ER stress.

Kv4.2 Mediates Histamine Modulation of Preoptic Neuron Activity and Body Temperature

PubMed Central

Sethi, Jasmine; Sanchez-Alavez, Manuel; Tabarean, Iustin V.

2011-01-01

Histamine regulates arousal, circadian rhythms, and thermoregulation. Activation of H3 histamine receptors expressed by preoptic GABAergic neurons results in a decrease of their firing rate and hyperthermia. Here we report that an increase in the A-type K+ current in preoptic GABAergic neurons in response to activation of H3 histamine receptors results in decreased firing rate and hyperthermia in mice. The Kv4.2 subunit is required for these actions in spite of the fact that Kv4.2−/− preoptic GABAergic neurons display A-type currents and firing characteristics similar to those of wild-type neurons. This electrical remodeling is achieved by robust upregulation of the expression of the Kv4.1 subunit and of a delayed rectifier current. Dynamic clamp experiments indicate that enhancement of the A-type current by a similar amount to that induced by histamine is sufficient to mimic its robust effect on firing rates. These data indicate a central role played by the Kv4.2 subunit in histamine regulation of body temperature and its interaction with pERK1/2 downstream of the H3 receptor. We also reveal that this pathway provides a mechanism for selective modulation of body temperature at the beginning of the active phase of the circadian cycle. PMID:22220205

Calcium-permeable α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid Receptors Trigger Neuronal Nitric-oxide Synthase Activation to Promote Nerve Cell Death in an Src Kinase-dependent Fashion*

PubMed Central

Socodato, Renato; Santiago, Felipe N.; Portugal, Camila C.; Domingues, Ana F.; Santiago, Ana R.; Relvas, João B.; Ambrósio, António F.; Paes-de-Carvalho, Roberto

2012-01-01

In the retina information decoding is dependent on excitatory neurotransmission and is critically modulated by AMPA glutamate receptors. The Src-tyrosine kinase has been implicated in modulating neurotransmission in CNS. Thus, our main goal was to correlate AMPA-mediated excitatory neurotransmission with the modulation of Src activity in retinal neurons. Cultured retinal cells were used to access the effects of AMPA stimulation on nitric oxide (NO) production and Src phosphorylation. 4-Amino-5-methylamino-2′,7′-difluorofluorescein diacetate fluorescence mainly determined NO production, and immunocytochemistry and Western blotting evaluated Src activation. AMPA receptors activation rapidly up-regulated Src phosphorylation at tyrosine 416 (stimulatory site) and down-regulated phosphotyrosine 527 (inhibitory site) in retinal cells, an effect mainly mediated by calcium-permeable AMPA receptors. Interestingly, experiments confirmed that neuronal NOS was activated in response to calcium-permeable AMPA receptor stimulation. Moreover, data suggest NO pathway as a key regulatory signaling in AMPA-induced Src activation in neurons but not in glial cells. The NO donor SNAP (S-nitroso-N-acetyl-dl-penicillamine) and a soluble guanylyl cyclase agonist (YC-1) mimicked AMPA effect in Src Tyr-416 phosphorylation, reinforcing that Src activation is indeed modulated by the NO pathway. Gain and loss-of-function data demonstrated that ERK is a downstream target of AMPA-induced Src activation and NO signaling. Furthermore, AMPA stimulated NO production in organotypic retinal cultures and increased Src activity in the in vivo retina. Additionally, AMPA-induced apoptotic retinal cell death was regulated by both NOS and Src activity. Because Src activity is pivotal in several CNS regions, the data presented herein highlight that Src modulation is a critical step in excitatory retinal cell death. PMID:22992730

Calcium-permeable α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors trigger neuronal nitric-oxide synthase activation to promote nerve cell death in an Src kinase-dependent fashion.

PubMed

Socodato, Renato; Santiago, Felipe N; Portugal, Camila C; Domingues, Ana F; Santiago, Ana R; Relvas, João B; Ambrósio, António F; Paes-de-Carvalho, Roberto

2012-11-09

In the retina information decoding is dependent on excitatory neurotransmission and is critically modulated by AMPA glutamate receptors. The Src-tyrosine kinase has been implicated in modulating neurotransmission in CNS. Thus, our main goal was to correlate AMPA-mediated excitatory neurotransmission with the modulation of Src activity in retinal neurons. Cultured retinal cells were used to access the effects of AMPA stimulation on nitric oxide (NO) production and Src phosphorylation. 4-Amino-5-methylamino-2',7'-difluorofluorescein diacetate fluorescence mainly determined NO production, and immunocytochemistry and Western blotting evaluated Src activation. AMPA receptors activation rapidly up-regulated Src phosphorylation at tyrosine 416 (stimulatory site) and down-regulated phosphotyrosine 527 (inhibitory site) in retinal cells, an effect mainly mediated by calcium-permeable AMPA receptors. Interestingly, experiments confirmed that neuronal NOS was activated in response to calcium-permeable AMPA receptor stimulation. Moreover, data suggest NO pathway as a key regulatory signaling in AMPA-induced Src activation in neurons but not in glial cells. The NO donor SNAP (S-nitroso-N-acetyl-DL-penicillamine) and a soluble guanylyl cyclase agonist (YC-1) mimicked AMPA effect in Src Tyr-416 phosphorylation, reinforcing that Src activation is indeed modulated by the NO pathway. Gain and loss-of-function data demonstrated that ERK is a downstream target of AMPA-induced Src activation and NO signaling. Furthermore, AMPA stimulated NO production in organotypic retinal cultures and increased Src activity in the in vivo retina. Additionally, AMPA-induced apoptotic retinal cell death was regulated by both NOS and Src activity. Because Src activity is pivotal in several CNS regions, the data presented herein highlight that Src modulation is a critical step in excitatory retinal cell death.

Acute engagement of Gq-mediated signaling in the bed nucleus of the stria terminalis induces anxiety-like behavior.

PubMed

Mazzone, C M; Pati, D; Michaelides, M; DiBerto, J; Fox, J H; Tipton, G; Anderson, C; Duffy, K; McKlveen, J M; Hardaway, J A; Magness, S T; Falls, W A; Hammack, S E; McElligott, Z A; Hurd, Y L; Kash, T L

2018-01-01

The bed nucleus of the stria terminalis (BNST) is a brain region important for regulating anxiety-related behavior in both humans and rodents. Here we used a chemogenetic strategy to investigate how engagement of G protein-coupled receptor (GPCR) signaling cascades in genetically defined GABAergic BNST neurons modulates anxiety-related behavior and downstream circuit function. We saw that stimulation of vesicular γ-aminobutyric acid (GABA) transporter (VGAT)-expressing BNST neurons using hM3Dq, but neither hM4Di nor rM3Ds designer receptors exclusively activated by a designer drug (DREADD), promotes anxiety-like behavior. Further, we identified that activation of hM3Dq receptors in BNST VGAT neurons can induce a long-term depression-like state of glutamatergic synaptic transmission, indicating DREADD-induced changes in synaptic plasticity. Further, we used DREADD-assisted metabolic mapping to profile brain-wide network activity following activation of G q -mediated signaling in BNST VGAT neurons and saw increased activity within ventral midbrain structures, including the ventral tegmental area and hindbrain structures such as the locus coeruleus and parabrachial nucleus. These results highlight that G q -mediated signaling in BNST VGAT neurons can drive downstream network activity that correlates with anxiety-like behavior and points to the importance of identifying endogenous GPCRs within genetically defined cell populations. We next used a microfluidics approach to profile the receptorome of single BNST VGAT neurons. This approach yielded multiple G q -coupled receptors that are associated with anxiety-like behavior and several potential novel candidates for regulation of anxiety-like behavior. From this, we identified that stimulation of the G q -coupled receptor 5-HT 2C R in the BNST is sufficient to elevate anxiety-like behavior in an acoustic startle task. Together, these results provide a novel profile of receptors within genetically defined BNST VGAT neurons that may serve as therapeutic targets for regulating anxiety states and provide a blueprint for examining how G-protein-mediated signaling in a genetically defined cell type can be used to assess behavior and brain-wide circuit function.

Activation of hypothalamic RIP-Cre neurons promotes beiging of WAT via sympathetic nervous system.

PubMed

Wang, Baile; Li, Ang; Li, Xiaomu; Ho, Philip Wl; Wu, Donghai; Wang, Xiaoqi; Liu, Zhuohao; Wu, Kelvin Kl; Yau, Sonata Sy; Xu, Aimin; Cheng, Kenneth Ky

2018-04-01

Activation of brown adipose tissue (BAT) and beige fat by cold increases energy expenditure. Although their activation is known to be differentially regulated in part by hypothalamus, the underlying neural pathways and populations remain poorly characterized. Here, we show that activation of rat-insulin-promoter-Cre (RIP-Cre) neurons in ventromedial hypothalamus (VMH) preferentially promotes recruitment of beige fat via a selective control of sympathetic nervous system (SNS) outflow to subcutaneous white adipose tissue (sWAT), but has no effect on BAT Genetic ablation of APPL2 in RIP-Cre neurons diminishes beiging in sWAT without affecting BAT, leading to cold intolerance and obesity in mice. Such defects are reversed by activation of RIP-Cre neurons, inactivation of VMH AMPK, or treatment with a β3-adrenergic receptor agonist. Hypothalamic APPL2 enhances neuronal activation in VMH RIP-Cre neurons and raphe pallidus, thereby eliciting SNS outflow to sWAT and subsequent beiging. These data suggest that beige fat can be selectively activated by VMH RIP-Cre neurons, in which the APPL2-AMPK signaling axis is crucial for this defending mechanism to cold and obesity. © 2018 The Authors.

mTORC1-dependent increase in oxidative metabolism in POMC neurons regulates food intake and action of leptin.

PubMed

Haissaguerre, Magalie; Ferrière, Amandine; Simon, Vincent; Saucisse, Nicolas; Dupuy, Nathalie; André, Caroline; Clark, Samantha; Guzman-Quevedo, Omar; Tabarin, Antoine; Cota, Daniela

2018-06-01

Nutrient availability modulates reactive oxygen species (ROS) production in the hypothalamus. In turn, ROS regulate hypothalamic neuronal activity and feeding behavior. The mechanistic target of rapamycin complex 1 (mTORC1) pathway is an important cellular integrator of the action of nutrients and hormones. Here we tested the hypothesis that modulation of mTORC1 activity, particularly in Proopiomelanocortin (POMC)-expressing neurons, mediates the cellular and behavioral effects of ROS. C57BL/6J mice or controls and their knockout (KO) littermates deficient either for the mTORC1 downstream target 70-kDa ribosomal protein S6 kinase 1 (S6K1) or for the mTORC1 component Rptor specifically in POMC neurons (POMC-rptor-KO) were treated with an intracerebroventricular (icv) injection of the ROS hydrogen peroxide (H 2 O 2 ) or the ROS scavenger honokiol, alone or, respectively, in combination with the mTORC1 inhibitor rapamycin or the mTORC1 activator leptin. Oxidant-related signal in POMC neurons was assessed using dihydroethidium (DHE) fluorescence. Icv administration of H 2 O 2 decreased food intake, while co-administration of rapamycin, whole-body deletion of S6K1, or deletion of rptor in POMC neurons impeded the anorectic action of H 2 O 2 . H 2 O 2 also increased oxidant levels in POMC neurons, an effect that hinged on functional mTORC1 in these neurons. Finally, scavenging ROS prevented the hypophagic action of leptin, which in turn required mTORC1 to increase oxidant levels in POMC neurons and to inhibit food intake. Our results demonstrate that ROS and leptin require mTORC1 pathway activity in POMC neurons to increase oxidant levels in POMC neurons and consequently decrease food intake. Copyright © 2018 The Authors. Published by Elsevier GmbH.. All rights reserved.

Neuronal Circuitry Mechanisms Regulating Adult Mammalian Neurogenesis

PubMed Central

Song, Juan; Olsen, Reid H.J.; Sun, Jiaqi; Ming, Guo-li; Song, Hongjun

2017-01-01

The adult mammalian brain is a dynamic structure, capable of remodeling in response to various physiological and pathological stimuli. One dramatic example of brain plasticity is the birth and subsequent integration of newborn neurons into the existing circuitry. This process, termed adult neurogenesis, recapitulates neural developmental events in two specialized adult brain regions: the lateral ventricles of the forebrain. Recent studies have begun to delineate how the existing neuronal circuits influence the dynamic process of adult neurogenesis, from activation of quiescent neural stem cells (NSCs) to the integration and survival of newborn neurons. Here, we review recent progress toward understanding the circuit-based regulation of adult neurogenesis in the hippocampus and olfactory bulb. PMID:27143698

Cocaine- and amphetamine-regulated transcript peptide increases mitochondrial respiratory chain complex II activity and protects against oxygen-glucose deprivation in neurons.

PubMed

Sha, Dujuan; Wang, Luna; Zhang, Jun; Qian, Lai; Li, Qiming; Li, Jin; Qian, Jian; Gu, Shuangshuang; Han, Ling; Xu, Peng; Xu, Yun

2014-09-25

The mechanisms of ischemic stroke, a main cause of disability and death, are complicated. Ischemic stroke results from the interaction of various factors including oxidative stress, a key pathological mechanism that plays an important role during the acute stage of ischemic brain injury. This study demonstrated that cocaine- and amphetamine-regulated transcript (CART) peptide, specifically CART55-102, increased the survival rate, but decreased the mortality of neurons exposed to oxygen-glucose deprivation (OGD), in a dose-dependent manner. The above-mentioned effects of CART55-102 were most significant at 0.4nM. These results indicated that CART55-102 suppressed neurotoxicity and enhanced neuronal survival after oxygen-glucose deprivation. CART55-102 (0.4nM) significantly diminished reactive oxygen species levels and markedly increased the activity of mitochondrial respiratory chain complex II in oxygen-glucose deprived neurons. In summary, CART55-102 suppressed oxidative stress in oxygen-glucose deprived neurons, possibly through elevating the activity of mitochondrial respiratory chain complex II. This result provides evidence for the development of CART55-102 as an antioxidant drug. Copyright © 2014 Elsevier B.V. All rights reserved.

Class II G Protein-Coupled Receptors and Their Ligands in Neuronal Function and Protection

PubMed Central

Martin, Bronwen; de Maturana, Rakel Lopez; Brenneman, Randall; Walent, Tom; Mattson, Mark P.; Maudsley, Stuart

2008-01-01

G protein-coupled receptors (GPCRs) play pivotal roles in regulating the function and plasticity of neuronal circuits in the nervous system. Among the myriad of GPCRs expressed in neural cells, class II GPCRs which couples predominantly to the Gs–adenylate cyclase–cAMP signaling pathway, have recently received considerable attention for their involvement in regulating neuronal survival. Neuropeptides that activate class II GPCRs include secretin, glucagon-like peptides (GLP-1 and GLP-2), growth hormone-releasing hormone (GHRH), pituitary adenylate cyclase activating peptide (PACAP), corticotropin-releasing hormone (CRH), vasoactive intestinal peptide (VIP), parathyroid hormone (PTH), and calcitonin-related peptides. Studies of patients and animal and cell culture models, have revealed possible roles for class II GPCRs signaling in the pathogenesis of several prominent neurodegenerative conditions including stroke, Alzheimer's, Parkinson's, and Huntington's diseases. Many of the peptides that activate class II GPCRs promote neuron survival by increasing the resistance of the cells to oxidative, metabolic, and excitotoxic injury. A better understanding of the cellular and molecular mechanisms by which class II GPCRs signaling modulates neuronal survival and plasticity will likely lead to novel therapeutic interventions for neurodegenerative disorders. PMID:16052036

Ablation of Sim1 Neurons Causes Obesity through Hyperphagia and Reduced Energy Expenditure

PubMed Central

Xi, Dong; Gandhi, Nilay; Lai, Meizan; Kublaoui, Bassil M.

2012-01-01

Single-minded 1 (Sim1) is a transcription factor necessary for development of the paraventricular nucleus of the hypothalamus (PVH). This nucleus is a critical regulator of appetite, energy expenditure and body weight. Previously we showed that Sim1+/− mice and conditional postnatal Sim1−/− mice exhibit hyperphagia, obesity, increased linear growth and susceptibility to diet-induced obesity, but no decrease in energy expenditure. Bilateral ablation of the PVH causes obesity due to hyperphagia and reduced energy expenditure. It remains unknown whether Sim1 neurons regulate energy expenditure. In this study, Sim1cre mice were bred to homozygous inducible diphtheria toxin receptor (iDTR) mice to generate mice expressing the simian DTR in Sim1 cells. In these mice, Sim1 neuron ablation was performed by intracerebroventricular (ICV) injection of diphtheria toxin. Compared to controls, mice with Sim1 neuron ablation became obese (with increased fat mass) on a chow diet due to increased food intake and reduced energy expenditure. In post-injection mice, we observed a strong inverse correlation between the degree of obesity and hypothalamic Sim1 expression. The reduction in baseline energy expenditure observed in these mice was accompanied by a reduction in activity. This reduction in activity did not fully account for the reduced energy expenditure as these mice exhibited decreased resting energy expenditure, decreased body temperature, decreased brown adipose tissue temperature, and decreased UCP1 expression suggesting an impairment of thermogenesis. In injected mice, hypothalamic gene expression of Sim1, oxytocin (OXT) and thyrotropin releasing hormone (TRH) was reduced by about 50%. These results demonstrate that Sim1 neurons in adult mice regulate both food intake and energy expenditure. Based on the body of work in the field, feeding regulation by Sim1 neurons likely occurs in both the PVH and medial amygdala, in contrast to energy expenditure regulation by Sim1 neurons, which likely is localized to the PVH. PMID:22558467

Ablation of Sim1 neurons causes obesity through hyperphagia and reduced energy expenditure.

PubMed

Xi, Dong; Gandhi, Nilay; Lai, Meizan; Kublaoui, Bassil M

2012-01-01

Single-minded 1 (Sim1) is a transcription factor necessary for development of the paraventricular nucleus of the hypothalamus (PVH). This nucleus is a critical regulator of appetite, energy expenditure and body weight. Previously we showed that Sim1(+/-) mice and conditional postnatal Sim1(-/-) mice exhibit hyperphagia, obesity, increased linear growth and susceptibility to diet-induced obesity, but no decrease in energy expenditure. Bilateral ablation of the PVH causes obesity due to hyperphagia and reduced energy expenditure. It remains unknown whether Sim1 neurons regulate energy expenditure. In this study, Sim1cre mice were bred to homozygous inducible diphtheria toxin receptor (iDTR) mice to generate mice expressing the simian DTR in Sim1 cells. In these mice, Sim1 neuron ablation was performed by intracerebroventricular (ICV) injection of diphtheria toxin. Compared to controls, mice with Sim1 neuron ablation became obese (with increased fat mass) on a chow diet due to increased food intake and reduced energy expenditure. In post-injection mice, we observed a strong inverse correlation between the degree of obesity and hypothalamic Sim1 expression. The reduction in baseline energy expenditure observed in these mice was accompanied by a reduction in activity. This reduction in activity did not fully account for the reduced energy expenditure as these mice exhibited decreased resting energy expenditure, decreased body temperature, decreased brown adipose tissue temperature, and decreased UCP1 expression suggesting an impairment of thermogenesis. In injected mice, hypothalamic gene expression of Sim1, oxytocin (OXT) and thyrotropin releasing hormone (TRH) was reduced by about 50%. These results demonstrate that Sim1 neurons in adult mice regulate both food intake and energy expenditure. Based on the body of work in the field, feeding regulation by Sim1 neurons likely occurs in both the PVH and medial amygdala, in contrast to energy expenditure regulation by Sim1 neurons, which likely is localized to the PVH.

p39, the Primary Activator for Cyclin-dependent Kinase 5 (Cdk5) in Oligodendroglia, Is Essential for Oligodendroglia Differentiation and Myelin Repair*

PubMed Central

Bankston, Andrew N.; Li, Wenqi; Zhang, Hui; Ku, Li; Liu, Guanglu; Papa, Filomena; Zhao, Lixia; Bibb, James A.; Cambi, Franca; Tiwari-Woodruff, Seema K.; Feng, Yue

2013-01-01

Cyclin-dependent kinase 5 (Cdk5) plays key roles in normal brain development and function. Dysregulation of Cdk5 may cause neurodegeneration and cognitive impairment. Besides the well demonstrated role of Cdk5 in neurons, emerging evidence suggests the functional requirement of Cdk5 in oligodendroglia (OL) and CNS myelin development. However, whether neurons and OLs employ similar or distinct mechanisms to regulate Cdk5 activity remains elusive. We report here that in contrast to neurons that harbor high levels of two Cdk5 activators, p35 and p39, OLs express abundant p39 but negligible p35. In addition, p39 is selectively up-regulated in OLs during differentiation along with elevated Cdk5 activity, whereas p35 expression remains unaltered. Specific knockdown of p39 by siRNA significantly attenuates Cdk5 activity and OL differentiation without affecting p35. Finally, expression of p39, but not p35, is increased during myelin repair, and remyelination is impaired in p39−/− mice. Together, these results reveal that neurons and OLs harbor distinct preference of Cdk5 activators and demonstrate important functions of p39-dependent Cdk5 activation in OL differentiation during de novo myelin development and myelin repair. PMID:23645679

Cellular Links between Neuronal Activity and Energy Homeostasis.

PubMed

Shetty, Pavan K; Galeffi, Francesca; Turner, Dennis A

2012-01-01

Neuronal activity, astrocytic responses to this activity, and energy homeostasis are linked together during baseline, conscious conditions, and short-term rapid activation (as occurs with sensory or motor function). Nervous system energy homeostasis also varies during long-term physiological conditions (i.e., development and aging) and with adaptation to pathological conditions, such as ischemia or low glucose. Neuronal activation requires increased metabolism (i.e., ATP generation) which leads initially to substrate depletion, induction of a variety of signals for enhanced astrocytic function, and increased local blood flow and substrate delivery. Energy generation (particularly in mitochondria) and use during ATP hydrolysis also lead to considerable heat generation. The local increases in blood flow noted following neuronal activation can both enhance local substrate delivery but also provides a heat sink to help cool the brain and removal of waste by-products. In this review we highlight the interactions between short-term neuronal activity and energy metabolism with an emphasis on signals and factors regulating astrocyte function and substrate supply.

Calcium Signaling Is Involved in Cadmium-Induced Neuronal Apoptosis via Induction of Reactive Oxygen Species and Activation of MAPK/mTOR Network

PubMed Central

Luo, Yan; Chen, Zi; Liu, Lei; Zhou, Hongyu; Chen, Wenxing; Shen, Tao; Han, Xiuzhen; Chen, Long; Huang, Shile

2011-01-01

Cadmium (Cd), a toxic environmental contaminant, induces oxidative stress, leading to neurodegenerative disorders. Recently we have demonstrated that Cd induces neuronal apoptosis in part by activation of the mitogen-activated protein kineses (MAPK) and mammalian target of rapamycin (mTOR) pathways. However, the underlying mechanism remains elusive. Here we show that Cd elevated intracellular calcium ion ([Ca2+]i) level in PC12, SH-SY5Y cells and primary murine neurons. BAPTA/AM, an intracellular Ca2+ chelator, abolished Cd-induced [Ca2+]i elevation, and blocked Cd activation of MAKPs including extracellular signal-regulated kinase 1/2 (Erk1/2), c-Jun N-terminal kinase (JNK) and p38, and mTOR-mediated signaling pathways, as well as cell death. Pretreatment with the extracellular Ca2+ chelator EGTA also prevented Cd-induced [Ca2+]i elevation, MAPK/mTOR activation, as well as cell death, suggesting that Cd-induced extracellular Ca2+ influx plays a critical role in contributing to neuronal apoptosis. In addition, calmodulin (CaM) antagonist trifluoperazine (TFP) or silencing CaM attenuated the effects of Cd on MAPK/mTOR activation and cell death. Furthermore, Cd-induced [Ca2+]i elevation or CaM activation resulted in induction of reactive oxygen species (ROS). Pretreatment with BAPTA/AM, EGTA or TFP attenuated Cd-induced ROS and cleavage of caspase-3 in the neuronal cells. Our findings indicate that Cd elevates [Ca2+]i, which induces ROS and activates MAPK and mTOR pathways, leading to neuronal apoptosis. The results suggest that regulation of Cd-disrupted [Ca2+]i homeostasis may be a new strategy for prevention of Cd-induced neurodegenerative diseases. PMID:21544200

Stimulation of GABA-Induced Ca2+ Influx Enhances Maturation of Human Induced Pluripotent Stem Cell-Derived Neurons

PubMed Central

Rushton, David J.; Mattis, Virginia B.; Svendsen, Clive N.; Allen, Nicholas D.; Kemp, Paul J.

2013-01-01

Optimal use of patient-derived, induced pluripotent stem cells for modeling neuronal diseases is crucially dependent upon the proper physiological maturation of derived neurons. As a strategy to develop defined differentiation protocols that optimize electrophysiological function, we investigated the role of Ca2+ channel regulation by astrocyte conditioned medium in neuronal maturation, using whole-cell patch clamp and Ca2+ imaging. Standard control medium supported basic differentiation of induced pluripotent stem cell-derived neurons, as assayed by the ability to fire simple, single, induced action potentials. In contrast, treatment with astrocyte conditioned medium elicited complex and spontaneous neuronal activity, often with rhythmic and biphasic characteristics. Such augmented spontaneous activity correlated with astrocyte conditioned medium-evoked hyperpolarization and was dependent upon regulated function of L-, N- and R-type Ca2+ channels. The requirement for astrocyte conditioned medium could be substituted by simply supplementing control differentiation medium with high Ca2+ or γ-amino butyric acid (GABA). Importantly, even in the absence of GABA signalling, opening Ca2+ channels directly using Bay K8644 was able to hyperpolarise neurons and enhance excitability, producing fully functional neurons. These data provide mechanistic insight into how secreted astrocyte factors control differentiation and, importantly, suggest that pharmacological modulation of Ca2+ channel function leads to the development of a defined protocol for improved maturation of induced pluripotent stem cell-derived neurons. PMID:24278369

IL-10 Promotes Neurite Outgrowth and Synapse Formation in Cultured Cortical Neurons after the Oxygen-Glucose Deprivation via JAK1/STAT3 Pathway.

PubMed

Chen, Hongbin; Lin, Wei; Zhang, Yixian; Lin, Longzai; Chen, Jianhao; Zeng, Yongping; Zheng, Mouwei; Zhuang, Zezhong; Du, Houwei; Chen, Ronghua; Liu, Nan

2016-07-26

As a classic immunoregulatory and anti-inflammatory cytokine, interleukin-10 (IL-10) provides neuroprotection in cerebral ischemia in vivo or oxygen-glucose deprivation (OGD)-induced injury in vitro. However, it remains blurred whether IL-10 promotes neurite outgrowth and synapse formation in cultured primary cortical neurons after OGD injury. In order to evaluate its effect on neuronal apoptosis, neurite outgrowth and synapse formation, we administered IL-10 or IL-10 neutralizing antibody (IL-10NA) to cultured rat primary cortical neurons after OGD injury. We found that IL-10 treatment activated the Janus kinase 1 (JAK1)/signal transducers and activators of transcription 3 (STAT3) signaling pathway. Moreover, IL-10 attenuated OGD-induced neuronal apoptosis by down-regulating the Bax expression and up-regulating the Bcl-2 expression, facilitated neurite outgrowth by increasing the expression of Netrin-1, and promoted synapse formation in cultured primary cortical neurons after OGD injury. These effects were partly abolished by JAK1 inhibitor GLPG0634. Contrarily, IL-10NA produced opposite effects on the cultured cortical neurons after OGD injury. Taken together, our findings suggest that IL-10 not only attenuates neuronal apoptosis, but also promotes neurite outgrowth and synapse formation via the JAK1/STAT3 signaling pathway in cultured primary cortical neurons after OGD injury.

IL-10 Promotes Neurite Outgrowth and Synapse Formation in Cultured Cortical Neurons after the Oxygen-Glucose Deprivation via JAK1/STAT3 Pathway

PubMed Central

Chen, Hongbin; Lin, Wei; Zhang, Yixian; Lin, Longzai; Chen, Jianhao; Zeng, Yongping; Zheng, Mouwei; Zhuang, Zezhong; Du, Houwei; Chen, Ronghua; Liu, Nan

2016-01-01

As a classic immunoregulatory and anti-inflammatory cytokine, interleukin-10 (IL-10) provides neuroprotection in cerebral ischemia in vivo or oxygen-glucose deprivation (OGD)-induced injury in vitro. However, it remains blurred whether IL-10 promotes neurite outgrowth and synapse formation in cultured primary cortical neurons after OGD injury. In order to evaluate its effect on neuronal apoptosis, neurite outgrowth and synapse formation, we administered IL-10 or IL-10 neutralizing antibody (IL-10NA) to cultured rat primary cortical neurons after OGD injury. We found that IL-10 treatment activated the Janus kinase 1 (JAK1)/signal transducers and activators of transcription 3 (STAT3) signaling pathway. Moreover, IL-10 attenuated OGD-induced neuronal apoptosis by down-regulating the Bax expression and up-regulating the Bcl-2 expression, facilitated neurite outgrowth by increasing the expression of Netrin-1, and promoted synapse formation in cultured primary cortical neurons after OGD injury. These effects were partly abolished by JAK1 inhibitor GLPG0634. Contrarily, IL-10NA produced opposite effects on the cultured cortical neurons after OGD injury. Taken together, our findings suggest that IL-10 not only attenuates neuronal apoptosis, but also promotes neurite outgrowth and synapse formation via the JAK1/STAT3 signaling pathway in cultured primary cortical neurons after OGD injury. PMID:27456198

The role of PDF neurons in setting the preferred temperature before dawn in Drosophila

PubMed Central

Tang, Xin; Roessingh, Sanne; Hayley, Sean E; Chu, Michelle L; Tanaka, Nobuaki K; Wolfgang, Werner; Song, Seongho; Stanewsky, Ralf; Hamada, Fumika N

2017-01-01

Animals have sophisticated homeostatic controls. While mammalian body temperature fluctuates throughout the day, small ectotherms, such as Drosophila achieve a body temperature rhythm (BTR) through their preference of environmental temperature. Here, we demonstrate that pigment dispersing factor (PDF) neurons play an important role in setting preferred temperature before dawn. We show that small lateral ventral neurons (sLNvs), a subset of PDF neurons, activate the dorsal neurons 2 (DN2s), the main circadian clock cells that regulate temperature preference rhythm (TPR). The number of temporal contacts between sLNvs and DN2s peak before dawn. Our data suggest that the thermosensory anterior cells (ACs) likely contact sLNvs via serotonin signaling. Together, the ACs-sLNs-DN2s neural circuit regulates the proper setting of temperature preference before dawn. Given that sLNvs are important for sleep and that BTR and sleep have a close temporal relationship, our data highlight a possible neuronal interaction between body temperature and sleep regulation. DOI: http://dx.doi.org/10.7554/eLife.23206.001 PMID:28463109

SLO-2 potassium channel is an important regulator of neurotransmitter release in Caenorhabditis elegans

PubMed Central

Liu, Ping; Chen, Bojun; Wang, Zhao-Wen

2014-01-01

Slo2 channels are prominent K+ channels in mammalian neurons but their physiological functions are not well understood. Here we investigate physiological functions and regulation of the C. elegans homologue SLO-2 in motor neurons through electrophysiological analyses of wild-type and mutant worms. We find that SLO-2 is the primary K+ channel conducting delayed outward current in cholinergic motor neurons, and one of two K+ channels with this function in GABAergic motor neurons. Loss-of-function mutation of slo-2 increases the duration and charge transfer rate of spontaneous postsynaptic current bursts at the neuromuscular junction, which are physiological signals used by motor neurons to control muscle cells, without altering postsynaptic receptor sensitivity. SLO-2 activity in motor neurons depends on Ca2+ entry through EGL-19, an L-type voltage-gated Ca2+ channel (CaV1), but not on other proteins implicated in either Ca2+ entry or intracellular Ca2+ release. Thus, SLO-2 is functionally coupled with CaV1 and regulates neurotransmitter release. PMID:25300429

Alternative Splicing in Neurogenesis and Brain Development.

PubMed

Su, Chun-Hao; D, Dhananjaya; Tarn, Woan-Yuh

2018-01-01

Alternative splicing of precursor mRNA is an important mechanism that increases transcriptomic and proteomic diversity and also post-transcriptionally regulates mRNA levels. Alternative splicing occurs at high frequency in brain tissues and contributes to every step of nervous system development, including cell-fate decisions, neuronal migration, axon guidance, and synaptogenesis. Genetic manipulation and RNA sequencing have provided insights into the molecular mechanisms underlying the effects of alternative splicing in stem cell self-renewal and neuronal fate specification. Timely expression and perhaps post-translational modification of neuron-specific splicing regulators play important roles in neuronal development. Alternative splicing of many key transcription regulators or epigenetic factors reprograms the transcriptome and hence contributes to stem cell fate determination. During neuronal differentiation, alternative splicing also modulates signaling activity, centriolar dynamics, and metabolic pathways. Moreover, alternative splicing impacts cortical lamination and neuronal development and function. In this review, we focus on recent progress toward understanding the contributions of alternative splicing to neurogenesis and brain development, which has shed light on how splicing defects may cause brain disorders and diseases.

GIRK Channels Modulate Opioid-Induced Motor Activity in a Cell Type- and Subunit-Dependent Manner

PubMed Central

Kotecki, Lydia; Hearing, Matthew; McCall, Nora M.; Marron Fernandez de Velasco, Ezequiel; Pravetoni, Marco; Arora, Devinder; Victoria, Nicole C.; Munoz, Michaelanne B.; Xia, Zhilian; Slesinger, Paul A.; Weaver, C. David

2015-01-01

G-protein-gated inwardly rectifying K+ (GIRK/Kir3) channel activation underlies key physiological effects of opioids, including analgesia and dependence. GIRK channel activation has also been implicated in the opioid-induced inhibition of midbrain GABA neurons and consequent disinhibition of dopamine (DA) neurons in the ventral tegmental area (VTA). Drug-induced disinhibition of VTA DA neurons has been linked to reward-related behaviors and underlies opioid-induced motor activation. Here, we demonstrate that mouse VTA GABA neurons express a GIRK channel formed by GIRK1 and GIRK2 subunits. Nevertheless, neither constitutive genetic ablation of Girk1 or Girk2, nor the selective ablation of GIRK channels in GABA neurons, diminished morphine-induced motor activity in mice. Moreover, direct activation of GIRK channels in midbrain GABA neurons did not enhance motor activity. In contrast, genetic manipulations that selectively enhanced or suppressed GIRK channel function in midbrain DA neurons correlated with decreased and increased sensitivity, respectively, to the motor-stimulatory effect of systemic morphine. Collectively, these data support the contention that the unique GIRK channel subtype in VTA DA neurons, the GIRK2/GIRK3 heteromer, regulates the sensitivity of the mouse mesolimbic DA system to drugs with addictive potential. PMID:25948263

Kv2.2: A Novel Molecular Target to Study the Role of Basal Forebrain GABAergic Neurons in the Sleep-Wake Cycle

PubMed Central

Hermanstyne, Tracey O.; Subedi, Kalpana; Le, Wei Wei; Hoffman, Gloria E.; Meredith, Andrea L.; Mong, Jessica A.; Misonou, Hiroaki

2013-01-01

Study Objectives: The basal forebrain (BF) has been implicated as an important brain region that regulates the sleep-wake cycle of animals. Gamma-aminobutyric acidergic (GABAergic) neurons are the most predominant neuronal population within this region. However, due to the lack of specific molecular tools, the roles of the BF GABAergic neurons have not been fully elucidated. Previously, we have found high expression levels of the Kv2.2 voltage-gated potassium channel on approximately 60% of GABAergic neurons in the magnocellular preoptic area and horizontal limb of the diagonal band of Broca of the BF and therefore proposed it as a potential molecular target to study this neuronal population. In this study, we sought to determine the functional roles of the Kv2.2-expressing neurons in the regulation of the sleep-wake cycle. Design: Sleep analysis between two genotypes and within each genotype before and after sleep deprivation. Setting: Animal sleep research laboratory. Participants: Adult mice. Wild-type and Kv2.2 knockout mice with C57/BL6 background. Interventions: EEG/EMG recordings from the basal state and after sleep-deprivation which was induced by mild aggitation for 6 h. Results: Immunostaining of a marker of neuronal activity indicates that these Kv2.2-expressing neurons appear to be preferentially active during the wake state. Therefore, we tested whether Kv2.2-expressing neurons in the BF are involved in arousal using Kv2.2-deficient mice. BF GABAergic neurons exhibited augmented expression of c-Fos. These knockout mice exhibited longer consolidated wake bouts than wild-type littermates, and that phenotype was further exacerbated by sleep deprivation. Moreover, in-depth analyses of their cortical electroencephalogram revealed a significant decrease in the delta-frequency activity during the nonrapid eye movement sleep state. Conclusions: These results revealed the significance of Kv2.2-expressing neurons in the regulation of the sleep-wake cycle. Citation: Hermanstyne TO; Subedi K; Le WW; Hoffman GE; Meredith AL; Mong JA; Misonou H. Kv2.2: a novel molecular target to study the role of basal forebrain GABAergic neurons in the sleep-wake cycle. SLEEP 2013;36(12):1839-1848. PMID:24293758

Activity-dependent downregulation of M-Type (Kv7) K⁺ channels surface expression requires the activation of iGluRs/Ca²⁺/PKC signaling pathway in hippocampal neuron.

PubMed

Li, Cai; Lu, Qing; Huang, Pengcheng; Fu, Tianli; Li, Changjun; Guo, Lianjun; Xu, Xulin

2015-08-01

M-type (Kv7) K(+) channels, encoded by KCNQ2-KCNQ5 genes, play a pivotal role in controlling neuronal excitability. However, precisely how neuronal activity regulates Kv7 channel translocation has not yet been fully defined. Here we reported activity-dependent changes in Kv7 channel subunits Kv7.2 and Kv7.3 surface expression by glutamate (glu). In the present study, we found that treatment with glutamate rapidly caused a specific decrease in M-current as well as Kv7 channel surface expression in primary cultured hippocampal neurons. The glutamate effects were mimicked by NMDA and AMPA. The glutamate effects on Kv7 channels were partially attenuated by pre-treatment of NMDA receptors antagonist d,l-APV or AMPA-KA receptors antagonist CNQX. The signal required Ca(2+) influx through L-type Ca(2+) channel and intracellular Ca(2+) elevations. PKC activation was involved in the glutamate-induced reduction of Kv7 channel surface expression. Moreover, a significant reduction of Kv7 channel surface expression occurred following glycine-induced "chem"-LTP in vitro and hippocampus-dependent behavioral learning training in vivo. These results demonstrated that activity-dependent reduction of Kv7 channel surface expression through activation of ionotropic glutamate receptors (iGluRs)/Ca(2+)/PKC signaling pathway might be an important molecular mechanism for regulation of neuronal excitability and synaptic plasticity. Copyright © 2015 Elsevier Ltd. All rights reserved.

The intellectual disability gene Kirrel3 regulates target-specific mossy fiber synapse development in the hippocampus.

PubMed

Martin, E Anne; Muralidhar, Shruti; Wang, Zhirong; Cervantes, Diégo Cordero; Basu, Raunak; Taylor, Matthew R; Hunter, Jennifer; Cutforth, Tyler; Wilke, Scott A; Ghosh, Anirvan; Williams, Megan E

2015-11-17

Synaptic target specificity, whereby neurons make distinct types of synapses with different target cells, is critical for brain function, yet the mechanisms driving it are poorly understood. In this study, we demonstrate Kirrel3 regulates target-specific synapse formation at hippocampal mossy fiber (MF) synapses, which connect dentate granule (DG) neurons to both CA3 and GABAergic neurons. Here, we show Kirrel3 is required for formation of MF filopodia; the structures that give rise to DG-GABA synapses and that regulate feed-forward inhibition of CA3 neurons. Consequently, loss of Kirrel3 robustly increases CA3 neuron activity in developing mice. Alterations in the Kirrel3 gene are repeatedly associated with intellectual disabilities, but the role of Kirrel3 at synapses remained largely unknown. Our findings demonstrate that subtle synaptic changes during development impact circuit function and provide the first insight toward understanding the cellular basis of Kirrel3-dependent neurodevelopmental disorders.

Control of arousal by the orexin neurons

PubMed Central

Alexandre, Chloe; Andermann, Mark L; Scammell, Thomas E

2013-01-01

The orexin-producing neurons in the lateral hypothalamus play an essential role in promoting arousal and maintaining wakefulness. These neurons receive a broad variety of signals related to environmental, physiological and emotional stimuli; they project to almost every brain region involved in the regulation of wakefulness; and they fire most strongly during active wakefulness, high motor activation, and sustained attention. This review focuses on the specific neuronal pathways through which the orexin neurons promote wakefulness and maintain high level of arousal, and how recent studies using optogenetic and pharmacogenetic methods have demonstrated that the locus coeruleus, the tuberomammillary nucleus, and the basal forebrain are some of the key sites mediating the arousing actions of orexins. PMID:23683477

Microtubule-regulating proteins and cAMP-dependent signaling in neuroblastoma differentiation.

PubMed

Muñoz-Llancao, Pablo; de Gregorio, Cristian; Las Heras, Macarena; Meinohl, Christopher; Noorman, Kevin; Boddeke, Erik; Cheng, Xiaodong; Lezoualc'h, Frank; Schmidt, Martina; Gonzalez-Billault, Christian

2017-03-01

Neurons are highly differentiated cells responsible for the conduction and transmission of information in the nervous system. The proper function of a neuron relies on the compartmentalization of their intracellular domains. Differentiated neuroblastoma cells have been extensively used to study and understand the physiology and cell biology of neuronal cells. Here, we show that differentiation of N1E-115 neuroblastoma cells is more pronounced upon exposure of a chemical analog of cyclic AMP (cAMP), db-cAMP. We next analysed the expression of key microtubule-regulating proteins in differentiated cells and the expression and activation of key cAMP players such as EPAC, PKA and AKAP79/150. Most of the microtubule-promoting factors were up regulated during differentiation of N1E-115 cells, while microtubule-destabilizing proteins were down regulated. We observed an increase in tubulin post-translational modifications related to microtubule stability. As expected, db-cAMP increased PKA- and EPAC-dependent signalling. Consistently, pharmacological modulation of EPAC activity instructed cell differentiation, number of neurites, and neurite length in N1E-115 cells. Moreover, disruption of the PKA-AKAP interaction reduced these morphometric parameters. Interestingly, PKA and EPAC act synergistically to induce neuronal differentiation in N1E-115. Altogether these results show that the changes observed in the differentiation of N1E-115 cells proceed by regulating several microtubule-stabilizing factors, and the acquisition of a neuronal phenotype is a process involving concerted although independent functions of EPAC and PKA. © 2017 Wiley Periodicals, Inc.

PeakCaller: an automated graphical interface for the quantification of intracellular calcium obtained by high-content screening.

PubMed

Artimovich, Elena; Jackson, Russell K; Kilander, Michaela B C; Lin, Yu-Chih; Nestor, Michael W

2017-10-16

Intracellular calcium is an important ion involved in the regulation and modulation of many neuronal functions. From regulating cell cycle and proliferation to initiating signaling cascades and regulating presynaptic neurotransmitter release, the concentration and timing of calcium activity governs the function and fate of neurons. Changes in calcium transients can be used in high-throughput screening applications as a basic measure of neuronal maturity, especially in developing or immature neuronal cultures derived from stem cells. Using human induced pluripotent stem cell derived neurons and dissociated mouse cortical neurons combined with the calcium indicator Fluo-4, we demonstrate that PeakCaller reduces type I and type II error in automated peak calling when compared to the oft-used PeakFinder algorithm under both basal and pharmacologically induced conditions. Here we describe PeakCaller, a novel MATLAB script and graphical user interface for the quantification of intracellular calcium transients in neuronal cultures. PeakCaller allows the user to set peak parameters and smoothing algorithms to best fit their data set. This new analysis script will allow for automation of calcium measurements and is a powerful software tool for researchers interested in high-throughput measurements of intracellular calcium.

Effect of Mimosa pudica (Linn.) extract on anxiety behaviour and GABAergic regulation of 5-HT neuronal activity in the mouse.

PubMed

Ayissi Mbomo, Rigobert; Gartside, Sasha; Ngo Bum, Elizabeth; Njikam, Njifutie; Okello, Ed; McQuade, Richard

2012-04-01

Mimosa pudica (Linn.) (M. pudica L.) is a plant used in some countries to treat anxiety and depression. In the present study we investigated the effects of an aqueous extract of M. pudica L. on mouse anxiety-like behaviour using the elevated T maze, and on regulation of dorsal raphe nucleus (DRN) 5-hydroxytryptamine (5-HT) neuronal activity using an in-vitro mouse brain slice preparation. Acute treatment with M. pudica L. extract had an anxiolytic effect on behaviour in the elevated T maze, specifically on inhibitory avoidance behaviour. Acute application of the extract alone had no effect on the activity of DRN 5-HT neurones. However, when co-applied with the GABA(A) receptor agonist THIP (4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol), the extract enhanced the inhibitory effect of the THIP on DRN 5-HT neurones. These observed effects of M. pudica L. on both behaviour and GABA modulation of 5-HT neuronal activity are similar to the effects of diazepam, the established anxiolytic and positive modulator of the GABA(A) receptor. This study suggests that the aqueous extract of M. pudica L. contains a positive modulator of GABA(A) receptor function and provides impetus for further investigation of the neuropharmacologically active constituents of the extract.

Activation of Muscarinic M1 Acetylcholine Receptors Induces Long-Term Potentiation in the Hippocampus

PubMed Central

Dennis, Siobhan H.; Pasqui, Francesca; Colvin, Ellen M.; Sanger, Helen; Mogg, Adrian J.; Felder, Christian C.; Broad, Lisa M.; Fitzjohn, Steve M.; Isaac, John T.R.; Mellor, Jack R.

2016-01-01

Muscarinic M1 acetylcholine receptors (M1Rs) are highly expressed in the hippocampus, and their inhibition or ablation disrupts the encoding of spatial memory. It has been hypothesized that the principal mechanism by which M1Rs influence spatial memory is by the regulation of hippocampal synaptic plasticity. Here, we use a combination of recently developed, well characterized, selective M1R agonists and M1R knock-out mice to define the roles of M1Rs in the regulation of hippocampal neuronal and synaptic function. We confirm that M1R activation increases input resistance and depolarizes hippocampal CA1 pyramidal neurons and show that this profoundly increases excitatory postsynaptic potential-spike coupling. Consistent with a critical role for M1Rs in synaptic plasticity, we now show that M1R activation produces a robust potentiation of glutamatergic synaptic transmission onto CA1 pyramidal neurons that has all the hallmarks of long-term potentiation (LTP): The potentiation requires NMDA receptor activity and bi-directionally occludes with synaptically induced LTP. Thus, we describe synergistic mechanisms by which acetylcholine acting through M1Rs excites CA1 pyramidal neurons and induces LTP, to profoundly increase activation of CA1 pyramidal neurons. These features are predicted to make a major contribution to the pro-cognitive effects of cholinergic transmission in rodents and humans. PMID:26472558

The Microtubule-Associated Protein Doublecortin-Like Regulates the Transport of the Glucocorticoid Receptor in Neuronal Progenitor Cells

PubMed Central

Fitzsimons, Carlos P.; Ahmed, Suaad; Wittevrongel, Christiaan F. W.; Schouten, Theo G.; Dijkmans, Thomas F.; Scheenen, Wim J. J. M.; Schaaf, Marcel J. M.; Ronald de Kloet, E.; Vreugdenhil, Erno

2008-01-01

In neuronal cells, activated glucocorticoid receptor (GR) translocates to the nucleus guided by the cytoskeleton. However, the detailed mechanisms underlying GR translocation remain unclear. Using gain and loss of function studies, we report here for the first time that the microtubule-associated protein doublecortin-like (DCL) controls GR translocation to the nucleus. DCL overexpression in COS-1 cells, neuroblastoma cells, and rat hippocampus organotypic slice cultures impaired GR translocation and decreased GR-dependent transcriptional activity, measured by a specific reporter gene assay, in COS-1 cells. Moreover, DCL and GR directly interact on microtubule bundles formed by DCL overexpression. A C-terminal truncated DCL with conserved microtubule-bundling activity did not influence GR translocation. In N1E-115 mouse neuroblastoma cells and neuronal progenitor cells in rat hippocampus organotypic slice cultures, laser-scanning confocal microscopy showed colabeling of endogenously expressed DCL and GR. In these systems, RNA-interference-mediated DCL knockdown hampered GR translocation. Thus, we conclude that DCL expression is tightly regulated to adequately control GR transport. Because DCL is primarily expressed in neuronal progenitor cells, our results introduce this microtubule-associated protein as a new modulator of GR signaling in this cell type and suggest the existence of cell-specific mechanisms regulating GR translocation to the nucleus. PMID:17975023

Endogenous purinergic signaling is required for osmotic volume regulation of retinal glial cells.

PubMed

Wurm, Antje; Lipp, Stephan; Pannicke, Thomas; Linnertz, Regina; Krügel, Ute; Schulz, Angela; Färber, Katrin; Zahn, Dirk; Grosse, Johannes; Wiedemann, Peter; Chen, Ju; Schöneberg, Torsten; Illes, Peter; Reichenbach, Andreas; Bringmann, Andreas

2010-03-01

Intense neuronal activity in the sensory retina is associated with a volume increase of neuronal cells (Uckermann et al., J. Neurosci. 2004, 24:10149) and a decrease in the osmolarity of the extracellular space fluid (Dmitriev et al., Vis. Neurosci. 1999, 16:1157). Here, we show the existence of an endogenous purinergic mechanism that prevents hypoosmotic swelling of retinal glial (Müller) cells in mice. In contrast to the cells from wild-type mice, hypoosmotic stress induced rapid swelling of glial cell somata in retinal slices from mice deficient in P2Y(1), adenosine A(1) receptors, or ecto-5'-nucleotidase (CD73). Consistently, glial cell bodies in retinal slices from wild-type mice displayed osmotic swelling when P2Y(1) or A(1) receptors, or CD73, were pharmacologically blocked. Exogenous ATP, UTP, and UDP inhibited glial swelling in retinal slices, while the swelling of isolated glial cells was prevented by ATP but not by UTP or UDP, suggesting that uracil nucleotides indirectly regulate the glial cell volume via activation of neuronal P2Y(4/6) and neuron-to-glia signaling. It is suggested that autocrine/paracrine activation of purinergic receptors and enzymes is crucially involved in the regulation of the glial cell volume.

Deletion of Tsc2 in Nociceptors Reduces Target Innervation, Ion Channel Expression, and Sensitivity to Heat

PubMed Central

Carlin, Dan; Golden, Judith P.; Monk, Kelly R.

2018-01-01

Abstract The mechanistic target of rapamycin complex 1 (mTORC1) is known to regulate cellular growth pathways, and its genetic activation is sufficient to enhance regenerative axon growth following injury to the central or peripheral nervous systems. However, excess mTORC1 activation may promote innervation defects, and mTORC1 activity mediates injury-induced hypersensitivity, reducing enthusiasm for the pathway as a therapeutic target. While mTORC1 activity is required for full expression of some pain modalities, the effects of pathway activation on nociceptor phenotypes and sensory behaviors are currently unknown. To address this, we genetically activated mTORC1 in mouse peripheral sensory neurons by conditional deletion of its negative regulator Tuberous Sclerosis Complex 2 (Tsc2). Consistent with the well-known role of mTORC1 in regulating cell size, soma size and axon diameter of C-nociceptors were increased in Tsc2-deleted mice. Glabrous skin and spinal cord innervation by C-fiber neurons were also disrupted. Transcriptional profiling of nociceptors enriched by fluorescence-associated cell sorting (FACS) revealed downregulation of multiple classes of ion channels as well as reduced expression of markers for peptidergic nociceptors in Tsc2-deleted mice. In addition to these changes in innervation and gene expression, Tsc2-deleted mice exhibited reduced noxious heat sensitivity and decreased injury-induced cold hypersensitivity, but normal baseline sensitivity to cold and mechanical stimuli. Together, these data show that excess mTORC1 activity in sensory neurons produces changes in gene expression, neuron morphology and sensory behavior. PMID:29766046

A transcription factor collective defines the HSN serotonergic neuron regulatory landscape

PubMed Central

Artacho, Alejandro; Jimeno-Martín, Ángela; Chirivella, Laura; Weinberg, Peter

2018-01-01

Cell differentiation is controlled by individual transcription factors (TFs) that together activate a selection of enhancers in specific cell types. How these combinations of TFs identify and activate their target sequences remains poorly understood. Here, we identify the cis-regulatory transcriptional code that controls the differentiation of serotonergic HSN neurons in Caenorhabditis elegans. Activation of the HSN transcriptome is directly orchestrated by a collective of six TFs. Binding site clusters for this TF collective form a regulatory signature that is sufficient for de novo identification of HSN neuron functional enhancers. Among C. elegans neurons, the HSN transcriptome most closely resembles that of mouse serotonergic neurons. Mouse orthologs of the HSN TF collective also regulate serotonergic differentiation and can functionally substitute for their worm counterparts which suggests deep homology. Our results identify rules governing the regulatory landscape of a critically important neuronal type in two species separated by over 700 million years. PMID:29553368

Galanin-Expressing GABA Neurons in the Lateral Hypothalamus Modulate Food Reward and Noncompulsive Locomotion

PubMed Central

Hoang, John; Bruce-Keller, Annadora; Berthoud, Hans-Rudolf; Morrison, Christopher D.

2017-01-01

The lateral hypothalamus (LHA) integrates reward and appetitive behavior and is composed of many overlapping neuronal populations. Recent studies associated LHA GABAergic neurons (LHAGABA), which densely innervate the ventral tegmental area (VTA), with modulation of food reward and consumption; yet, LHAGABA projections to the VTA exclusively modulated food consumption, not reward. We identified a subpopulation of LHAGABA neurons that coexpress the neuropeptide galanin (LHAGal). These LHAGal neurons also modulate food reward, but lack direct VTA innervation. We hypothesized that LHAGal neurons may represent a subpopulation of LHAGABA neurons that mediates food reward independent of direct VTA innervation. We used chemogenetic activation of LHAGal or LHAGABA neurons in mice to compare their role in feeding behavior. We further analyzed locomotor behavior to understand how differential VTA connectivity and transmitter release in these LHA neurons influences this behavior. LHAGal or LHAGABA neuronal activation both increased operant food-seeking behavior, but only activation of LHAGABA neurons increased overall chow consumption. Additionally, LHAGal or LHAGABA neuronal activation similarly induced locomotor activity, but with striking differences in modality. Activation of LHAGABA neurons induced compulsive-like locomotor behavior; while LHAGal neurons induced locomotor activity without compulsivity. Thus, LHAGal neurons define a subpopulation of LHAGABA neurons without direct VTA innervation that mediate noncompulsive food-seeking behavior. We speculate that the striking difference in compulsive-like locomotor behavior is also based on differential VTA innervation. The downstream neural network responsible for this behavior and a potential role for galanin as neuromodulator remains to be identified. SIGNIFICANCE STATEMENT The lateral hypothalamus (LHA) regulates motivated feeding behavior via GABAergic LHA neurons. The molecular identity of LHAGABA neurons is heterogeneous and largely undefined. Here we introduce LHAGal neurons as a subset of LHAGABA neurons that lack direct innervation of the ventral tegmental area (VTA). LHAGal neurons are sufficient to drive motivated feeding and locomotor activity similar to LHAGABA neurons, but without inducing compulsive-like behaviors, which we propose to require direct VTA innervation. Our study integrates galanin-expressing LHA neurons into our current understanding of the neuronal circuits and molecular mechanisms of the LHA that contribute to motivated feeding behaviors. PMID:28539422

Myosin light chain kinase facilitates endocytosis of synaptic vesicles at hippocampal boutons.

PubMed

Li, Lin; Wu, Xiaomei; Yue, Hai-Yuan; Zhu, Yong-Chuan; Xu, Jianhua

2016-07-01

At nerve terminals, endocytosis efficiently recycles vesicle membrane to maintain synaptic transmission under different levels of neuronal activity. Ca(2+) and its downstream signal pathways are critical for the activity-dependent regulation of endocytosis. An activity- and Ca(2+) -dependent kinase, myosin light chain kinase (MLCK) has been reported to regulate vesicle mobilization, vesicle cycling, and motility in different synapses, but whether it has a general contribution to regulation of endocytosis at nerve terminals remains unknown. We investigated this issue at rat hippocampal boutons by imaging vesicle endocytosis as the real-time retrieval of vesicular synaptophysin tagged with a pH-sensitive green fluorescence protein. We found that endocytosis induced by 200 action potentials (5-40 Hz) was slowed by acute inhibition of MLCK and down-regulation of MLCK with RNA interference, while the total amount of vesicle exocytosis and somatic Ca(2+) channel current did not change with MLCK down-regulation. Acute inhibition of myosin II similarly impaired endocytosis. Furthermore, down-regulation of MLCK prevented depolarization-induced phosphorylation of myosin light chain, an effect shared by blockers of Ca(2+) channels and calmodulin. These results suggest that MLCK facilitates vesicle endocytosis through activity-dependent phosphorylation of myosin downstream of Ca(2+) /calmodulin, probably as a widely existing mechanism among synapses. Our study suggests that MLCK is an important activity-dependent regulator of vesicle recycling in hippocampal neurons, which are critical for learning and memory. The kinetics of vesicle membrane endocytosis at nerve terminals has long been known to depend on activity and Ca(2+) . This study provides evidence suggesting that myosin light chain kinase increases endocytosis efficiency at hippocampal neurons by mediating Ca(2+) /calmodulin-dependent phosphorylation of myosin. The authors propose that this signal cascade may serve as a common pathway contributing to the activity-dependent regulation of vesicle endocytosis at synapses. © 2016 International Society for Neurochemistry.

Novel β-catenin target genes identified in thalamic neurons encode modulators of neuronal excitability

PubMed Central

2012-01-01

Background LEF1/TCF transcription factors and their activator β-catenin are effectors of the canonical Wnt pathway. Although Wnt/β-catenin signaling has been implicated in neurodegenerative and psychiatric disorders, its possible role in the adult brain remains enigmatic. To address this issue, we sought to identify the genetic program activated by β-catenin in neurons. We recently showed that β-catenin accumulates specifically in thalamic neurons where it activates Cacna1g gene expression. In the present study, we combined bioinformatics and experimental approaches to find new β-catenin targets in the adult thalamus. Results We first selected the genes with at least two conserved LEF/TCF motifs within the regulatory elements. The resulting list of 428 putative LEF1/TCF targets was significantly enriched in known Wnt targets, validating our approach. Functional annotation of the presumed targets also revealed a group of 41 genes, heretofore not associated with Wnt pathway activity, that encode proteins involved in neuronal signal transmission. Using custom polymerase chain reaction arrays, we profiled the expression of these genes in the rat forebrain. We found that nine of the analyzed genes were highly expressed in the thalamus compared with the cortex and hippocampus. Removal of nuclear β-catenin from thalamic neurons in vitro by introducing its negative regulator Axin2 reduced the expression of six of the nine genes. Immunoprecipitation of chromatin from the brain tissues confirmed the interaction between β-catenin and some of the predicted LEF1/TCF motifs. The results of these experiments validated four genes as authentic and direct targets of β-catenin: Gabra3 for the receptor of GABA neurotransmitter, Calb2 for the Ca2+-binding protein calretinin, and the Cacna1g and Kcna6 genes for voltage-gated ion channels. Two other genes from the latter cluster, Cacna2d2 and Kcnh8, appeared to be regulated by β-catenin, although the binding of β-catenin to the regulatory sequences of these genes could not be confirmed. Conclusions In the thalamus, β-catenin regulates the expression of a novel group of genes that encode proteins involved in neuronal excitation. This implies that the transcriptional activity of β-catenin is necessary for the proper excitability of thalamic neurons, may influence activity in the thalamocortical circuit, and may contribute to thalamic pathologies. PMID:23157480

Regulation of C. elegans presynaptic differentiation and neurite branching via a novel signaling pathway initiated by SAM-10

PubMed Central

Zheng, Qun; Schaefer, Anneliese M.; Nonet, Michael L.

2011-01-01

Little is known about transcriptional control of neurite branching or presynaptic differentiation, events that occur relatively late in neuronal development. Using the Caenorhabditis elegans mechanosensory circuit as an in vivo model, we show that SAM-10, an ortholog of mammalian single-stranded DNA-binding protein (SSDP), functions cell-autonomously in the nucleus to regulate synaptic differentiation, as well as positioning of, a single neurite branch. PLM mechanosensory neurons in sam-10 mutants exhibit abnormal placement of the neurite branch point, and defective synaptogenesis, characterized by an overextended synaptic varicosity, underdeveloped synaptic morphology and disrupted colocalization of active zone and synaptic vesicles. SAM-10 functions coordinately with Lim domain-binding protein 1 (LDB-1), demonstrated by our observations that: (1) mutations in either gene show similar defects in PLM neurons; and (2) LDB-1 is required for SAM-10 nuclear localization. SAM-10 regulates PLM synaptic differentiation by suppressing transcription of prk-2, which encodes an ortholog of the mammalian Pim kinase family. PRK-2-mediated activities of SAM-10 are specifically involved in PLM synaptic differentiation, but not other sam-10 phenotypes such as neurite branching. Thus, these data reveal a novel transcriptional signaling pathway that regulates neuronal specification of neurite branching and presynaptic differentiation. PMID:21115607

Regulation of C. elegans presynaptic differentiation and neurite branching via a novel signaling pathway initiated by SAM-10.

PubMed

Zheng, Qun; Schaefer, Anneliese M; Nonet, Michael L

2011-01-01

Little is known about transcriptional control of neurite branching or presynaptic differentiation, events that occur relatively late in neuronal development. Using the Caenorhabditis elegans mechanosensory circuit as an in vivo model, we show that SAM-10, an ortholog of mammalian single-stranded DNA-binding protein (SSDP), functions cell-autonomously in the nucleus to regulate synaptic differentiation, as well as positioning of, a single neurite branch. PLM mechanosensory neurons in sam-10 mutants exhibit abnormal placement of the neurite branch point, and defective synaptogenesis, characterized by an overextended synaptic varicosity, underdeveloped synaptic morphology and disrupted colocalization of active zone and synaptic vesicles. SAM-10 functions coordinately with Lim domain-binding protein 1 (LDB-1), demonstrated by our observations that: (1) mutations in either gene show similar defects in PLM neurons; and (2) LDB-1 is required for SAM-10 nuclear localization. SAM-10 regulates PLM synaptic differentiation by suppressing transcription of prk-2, which encodes an ortholog of the mammalian Pim kinase family. PRK-2-mediated activities of SAM-10 are specifically involved in PLM synaptic differentiation, but not other sam-10 phenotypes such as neurite branching. Thus, these data reveal a novel transcriptional signaling pathway that regulates neuronal specification of neurite branching and presynaptic differentiation.

Enhanced anorexigenic signaling in lean obesity resistant syndecan-3 null mice

PubMed Central

Zheng, Qiao; Zhu, Jinling; Shanabrough, Marya; Borok, Erzsebet; Benoit, Stephen C.; Horvath, Tamas L.; Clegg, Deborah J.; Reizes, Ofer

2010-01-01

Obesity is associated with increased risk of diabetes, cardiovascular disease and several types of cancers. The hypothalamus is a region of the brain critical in the regulation of body weight. One of the critical and best studied hypothalamic circuits is comprised of the melanocortinergic orexigenic agouti -related protein (AgRP) and anorexigenic α-melanocyte stimulating hormone (α-MSH) neurons. These neurons project axons to the same hypothalamic target neurons and balance each other’s activity leading to body weight regulation. We previously showed that the brain proteoglycan syndecan-3 regulates feeding behavior and body weight, and syndecan-3 null (SDC-3−/−) mice are lean and obesity resistant. Here we show that the melanocortin agonist MTII potently suppresses food intake and activates the hypothalamic paraventricular nuclei (PVN) in SDC-3−/− mice based on c-fos immunoreactivity. Interestingly, we determined that the AgRP neuropeptide is reduced in the PVN of SDC-3−/− mice compared to wild type mice. In contrast, neuropeptide Y, coexpressed in the AgRP neuron, is not differentially expressed nor is the counteracting neuropeptide αMSH. These findings are unprecedented and indicate that AgRP protein localization can be selectively regulated within the hypothalamus resulting in altered neuropeptide response and tone. PMID:20923696

Arctic ground squirrel (Spermophilus parryii) hippocampal neurons tolerate prolonged oxygen– glucose deprivation and maintain baseline ERK1/2 and JNK activation despite drastic ATP loss

PubMed Central

Christian, Sherri L; Ross, Austin P; Zhao, Huiwen W; Kristenson, Heidi J; Zhan, Xinhua; Rasley, Brian T; Bickler, Philip E; Drew, Kelly L

2009-01-01

Oxygen–glucose deprivation (OGD) initiates a cascade of intracellular responses that culminates in cell death in sensitive species. Neurons from Arctic ground squirrels (AGS), a hibernating species, tolerate OGD in vitro and global ischemia in vivo independent of temperature or torpor. Regulation of energy stores and activation of mitogen-activated protein kinase (MAPK) signaling pathways can regulate neuronal survival. We used acute hippocampal slices to investigate the role of ATP stores and extracellular signal-regulated kinase (ERK)1/2 and Jun NH2-terminal kinase (JNK) MAPKs in promoting survival. Acute hippocampal slices from AGS tolerated 30 mins of OGD and showed a small but significant increase in cell death with 2 h OGD at 37°C. This tolerance is independent of hibernation state or season. Neurons from AGS survive OGD despite rapid ATP depletion by 3 mins in interbout euthermic AGS and 10 mins in hibernating AGS. Oxygen–glucose deprivation does not induce JNK activation in AGS and baseline ERK1/2 and JNK activation is maintained even after drastic depletion of ATP. Surprisingly, inhibition of ERK1/2 or JNK during OGD had no effect on survival, whereas inhibition of JNK increased cell death during normoxia. Thus, protective mechanisms promoting tolerance to OGD by AGS are downstream from ATP loss and are independent of hibernation state or season. PMID:18398417

Striatal dopamine neurotransmission: regulation of release and uptake

PubMed Central

Sulzer, David; Cragg, Stephanie J.; Rice, Margaret E.

2016-01-01

Dopamine (DA) transmission is governed by processes that regulate release from axonal boutons in the forebrain and the somatodendritic compartment in midbrain, and by clearance by the DA transporter, diffusion, and extracellular metabolism. We review how axonal DA release is regulated by neuronal activity and by autoreceptors and heteroreceptors, and address how quantal release events are regulated in size and frequency. In brain regions densely innervated by DA axons, DA clearance is due predominantly to uptake by the DA transporter, whereas in cortex, midbrain, and other regions with relatively sparse DA inputs, the norepinephrine transporter and diffusion are involved. We discuss the role of DA uptake in restricting the sphere of influence of DA and in temporal accumulation of extracellular DA levels upon successive action potentials. The tonic discharge activity of DA neurons may be translated into a tonic extracellular DA level, whereas their bursting activity can generate discrete extracellular DA transients. PMID:27141430

GLP-1 Receptor Stimulation of the Lateral Parabrachial Nucleus Reduces Food Intake: Neuroanatomical, Electrophysiological, and Behavioral Evidence

PubMed Central

Richard, Jennifer E.; Farkas, Imre; Anesten, Fredrik; Anderberg, Rozita H.; Dickson, Suzanne L.; Gribble, Fiona M.; Reimann, Frank; Jansson, John-Olov; Liposits, Zsolt

2014-01-01

The parabrachial nucleus (PBN) is a key nucleus for the regulation of feeding behavior. Inhibitory inputs from the hypothalamus to the PBN play a crucial role in the normal maintenance of feeding behavior, because their loss leads to starvation. Viscerosensory stimuli result in neuronal activation of the PBN. However, the origin and neurochemical identity of the excitatory neuronal input to the PBN remain largely unexplored. Here, we hypothesize that hindbrain glucagon-like peptide 1 (GLP-1) neurons provide excitatory inputs to the PBN, activation of which may lead to a reduction in feeding behavior. Our data, obtained from mice expressing the yellow fluorescent protein in GLP-1-producing neurons, revealed that hindbrain GLP-1-producing neurons project to the lateral PBN (lPBN). Stimulation of lPBN GLP-1 receptors (GLP-1Rs) reduced the intake of chow and palatable food and decreased body weight in rats. It also activated lPBN neurons, reflected by an increase in the number of c-Fos-positive cells in this region. Further support for an excitatory role of GLP-1 in the PBN is provided by electrophysiological studies showing a remarkable increase in firing of lPBN neurons after Exendin-4 application. We show that within the PBN, GLP-1R activation increased gene expression of 2 energy balance regulating peptides, calcitonin gene-related peptide (CGRP) and IL-6. Moreover, nearly 70% of the lPBN GLP-1 fibers innervated lPBN CGRP neurons. Direct intra-lPBN CGRP application resulted in anorexia. Collectively, our molecular, anatomical, electrophysiological, pharmacological, and behavioral data provide evidence for a functional role of the GLP-1R for feeding control in the PBN. PMID:25116706

Heat shock protein 70.1 (Hsp70.1) affects neuronal cell fate by regulating lysosomal acid sphingomyelinase.

PubMed

Zhu, Hong; Yoshimoto, Tanihiro; Yamashima, Tetsumori

2014-10-03

The inducible expression of heat shock protein 70.1 (Hsp70.1) plays cytoprotective roles in its molecular chaperone function. Binding of Hsp70 to an endolysosomal phospholipid, bis(monoacylglycero)phosphate (BMP), has been recently shown to stabilize lysosomal membranes by enhancing acid sphingomyelinase (ASM) activity in cancer cells. Using the monkey experimental paradigm, we have reported that calpain-mediated cleavage of oxidized Hsp70.1 causes neurodegeneration in the hippocampal cornu ammonis 1 (CA1), whereas expression of Hsp70.1 in the motor cortex without calpain activation contributes to neuroprotection. However, the molecular mechanisms of the lysosomal destabilization/stabilization determining neuronal cell fate have not been elucidated. To elucidate whether regulation of lysosomal ASM could affect the neuronal fate, we analyzed Hsp70.1-BMP binding and ASM activity by comparing the motor cortex and the CA1. We show that Hsp70.1 being localized at the lysosomal membrane, lysosomal lipid BMP levels, and the lipid binding domain of Hsp70.1 are crucial for Hsp70.1-BMP binding. In the postischemic motor cortex, Hsp70.1 being localized at the lysosomal membrane could bind to BMP without calpain activation and decreased BMP levels, resulting in increasing ASM activity and lysosomal stability. However, in the postischemic CA1, calpain activation and a concomitant decrease in the lysosomal membrane localization of Hsp70.1 and BMP levels may diminish Hsp70.1-BMP binding, resulting in decreased ASM activity and lysosomal rupture with leakage of cathepsin B into the cytosol. A TUNEL assay revealed the differential neuronal vulnerability between the CA1 and the motor cortex. These results suggest that regulation of ASM activation in vivo by Hsp70.1-BMP affects lysosomal stability and neuronal survival or death after ischemia/reperfusion. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

Sarm1 deficiency impairs synaptic function and leads to behavioral deficits, which can be ameliorated by an mGluR allosteric modulator.

PubMed

Lin, Chia-Wen; Chen, Chiung-Ya; Cheng, Sin-Jhong; Hu, Hsiao-Tang; Hsueh, Yi-Ping

2014-01-01

Innate immune responses have been shown to influence brain development and function. Dysregulation of innate immunity is significantly associated with psychiatric disorders such as autism spectrum disorders and schizophrenia, which are well-known neurodevelopmental disorders. Recent studies have revealed that critical players of the innate immune response are expressed in neuronal tissues and regulate neuronal function and activity. For example, Sarm1, a negative regulator that acts downstream of Toll-like receptor (TLR) 3 and 4, is predominantly expressed in neurons. We have previously shown that Sarm1 regulates neuronal morphogenesis and the expression of inflammatory cytokines in the brain, which then affects learning ability, cognitive flexibility, and social interaction. Because impaired neuronal morphogenesis and dysregulation of cytokine expression may disrupt neuronal activity, we investigated whether Sarm1 knockdown affects the synaptic responses of neurons. We here show that reduced Sarm1 expression impairs metabotropic glutamate receptor (mGluR)-dependent long-term depression (LTD) formation but enhances N-methyl-D-aspartate receptor (NMDAR)-dependent long-term potentiation production in hippocampal CA1 neurons. The expression levels of post-synaptic proteins, including NR2a, NR1, Shank1 and Shank3, are also altered in Sarm1 knockdown mice, suggesting a role for Sarm1 in the maintenance of synaptic homeostasis. The addition of a positive allosteric modulator of mGluR5, CDPPB, ameliorates the LTD defects in slice recording and the behavioral deficits in social interaction and associative memory. These results suggest an important role for mGluR5 signaling in the function of Sarm1. In conclusion, our study demonstrates a role for Sarm1 in the regulation of synaptic plasticity. Through these mechanisms, Sarm1 knockdown results in the impairment of associative memory and social interactions in mice.

Prepubertal Development of Gonadotropin-Releasing Hormone Neuron Activity Is Altered by Sex, Age, and Prenatal Androgen Exposure.

PubMed

Dulka, Eden A; Moenter, Suzanne M

2017-11-01

Gonadotropin-releasing hormone (GnRH) neurons regulate reproduction though pulsatile hormone release. Disruption of GnRH release as measured via luteinizing hormone (LH) pulses occurs in polycystic ovary syndrome (PCOS), and in young hyperandrogenemic girls. In adult prenatally androgenized (PNA) mice, which exhibit many aspects of PCOS, increased LH is associated with increased GnRH neuron action potential firing. How GnRH neuron activity develops over the prepubertal period and whether this is altered by sex or prenatal androgen treatment are unknown. We hypothesized GnRH neurons are active before puberty and that this activity is sexually differentiated and altered by PNA. Dams were injected with dihydrotestosterone (DHT) on days 16 to 18 post copulation to generate PNA mice. Action potential firing of GFP-identified GnRH neurons in brain slices from 1-, 2-, 3-, and 4-week-old and adult mice was monitored. GnRH neurons were active at all ages tested. In control females, activity increased with age through 3 weeks, then decreased to adult levels. In contrast, activity did not change in PNA females and was reduced at 3 weeks. Activity was higher in control females than males from 2 to 3 weeks. PNA did not affect GnRH neuron firing rate in males at any age. Short-term action potential patterns were also affected by age and PNA treatment. GnRH neurons are thus typically more active during the prepubertal period than adulthood, and PNA reduces prepubertal activity in females. Prepubertal activity may play a role in establishing sexually differentiated neuronal networks upstream of GnRH neurons; androgen-induced changes during this time may contribute to the adult PNA, and possibly PCOS, phenotype. Copyright © 2017 Endocrine Society.

Local pruning of dendrites and spines by caspase-3-dependent and proteasome-limited mechanisms.

PubMed

Ertürk, Ali; Wang, Yuanyuan; Sheng, Morgan

2014-01-29

Synapse loss occurs normally during development and pathologically during neurodegenerative disease. Long-term depression, a proposed physiological correlate of synapse elimination, requires caspase-3 and the mitochondrial pathway of apoptosis. Here, we show that caspase-3 activity is essential--and can act locally within neurons--for regulation of spine density and dendrite morphology. By photostimulation of Mito-KillerRed, we induced caspase-3 activity in defined dendritic regions of cultured neurons. Within the photostimulated region, local elimination of dendritic spines and dendrite retraction occurred in a caspase-3-dependent manner without inducing cell death. However, pharmacological inhibition of inhibitor of apoptosis proteins or proteasome function led to neuronal death, suggesting that caspase activation is spatially restricted by these "molecular brakes" on apoptosis. Caspase-3 knock-out mice have increased spine density and altered miniature EPSCs, confirming a physiological involvement of caspase-3 in the regulation of spines in vivo.

Leptin regulates glutamate and glucose transporters in hypothalamic astrocytes

PubMed Central

Fuente-Martín, Esther; García-Cáceres, Cristina; Granado, Miriam; de Ceballos, María L.; Sánchez-Garrido, Miguel Ángel; Sarman, Beatrix; Liu, Zhong-Wu; Dietrich, Marcelo O.; Tena-Sempere, Manuel; Argente-Arizón, Pilar; Díaz, Francisca; Argente, Jesús; Horvath, Tamas L.; Chowen, Julie A.

2012-01-01

Glial cells perform critical functions that alter the metabolism and activity of neurons, and there is increasing interest in their role in appetite and energy balance. Leptin, a key regulator of appetite and metabolism, has previously been reported to influence glial structural proteins and morphology. Here, we demonstrate that metabolic status and leptin also modify astrocyte-specific glutamate and glucose transporters, indicating that metabolic signals influence synaptic efficacy and glucose uptake and, ultimately, neuronal function. We found that basal and glucose-stimulated electrical activity of hypothalamic proopiomelanocortin (POMC) neurons in mice were altered in the offspring of mothers fed a high-fat diet. In adulthood, increased body weight and fasting also altered the expression of glucose and glutamate transporters. These results demonstrate that whole-organism metabolism alters hypothalamic glial cell activity and suggest that these cells play an important role in the pathology of obesity. PMID:23064363

Neurotrophin signaling and visceral hypersensitivity.

PubMed

Qiao, Li-Ya

2014-06-01

Neurotrophin family are traditionally recognized for their nerve growth promoting function and are recently identified as crucial factors in regulating neuronal activity in the central and peripheral nervous systems. The family members including nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3) are reported to have distinct roles in the development and maintenance of sensory phenotypes in normal states and in the modulation of sensory activity in disease. This paper highlights receptor tyrosine kinase (Trk) -mediated signal transduction by which neurotrophins regulate neuronal activity in the visceral sensory reflex pathways with emphasis on the distinct roles of NGF and BDNF signaling in physiologic and pathophysiological processes. Viscero-visceral cross-organ sensitization exists widely in human diseases. The role of neurotrophins in mediating neural cross talk and interaction in primary afferent neurons in the dorsal root ganglia (DRG) and neurotrophin signal transduction in the context of cross-organ sensitization are also discussed.

A Hypothalamic Switch for REM and Non-REM Sleep.

PubMed

Chen, Kai-Siang; Xu, Min; Zhang, Zhe; Chang, Wei-Cheng; Gaj, Thomas; Schaffer, David V; Dan, Yang

2018-03-07

Rapid eye movement (REM) and non-REM (NREM) sleep are controlled by specific neuronal circuits. Here we show that galanin-expressing GABAergic neurons in the dorsomedial hypothalamus (DMH) comprise separate subpopulations with opposing effects on REM versus NREM sleep. Microendoscopic calcium imaging revealed diverse sleep-wake activity of DMH GABAergic neurons, but the galanin-expressing subset falls into two distinct groups, either selectively activated (REM-on) or suppressed (REM-off) during REM sleep. Retrogradely labeled, preoptic area (POA)-projecting galaninergic neurons are REM-off, whereas the raphe pallidus (RPA)-projecting neurons are primarily REM-on. Bidirectional optogenetic manipulations showed that the POA-projecting neurons promote NREM sleep and suppress REM sleep, while the RPA-projecting neurons have the opposite effects. Thus, REM/NREM switch is regulated antagonistically by DMH galaninergic neurons with intermingled cell bodies but distinct axon projections. Copyright © 2018 Elsevier Inc. All rights reserved.

A pair of dopamine neurons target the D1-like dopamine receptor DopR in the central complex to promote ethanol-stimulated locomotion in Drosophila.

PubMed

Kong, Eric C; Woo, Katherine; Li, Haiyan; Lebestky, Tim; Mayer, Nasima; Sniffen, Melissa R; Heberlein, Ulrike; Bainton, Roland J; Hirsh, Jay; Wolf, Fred W

2010-04-01

Dopamine is a mediator of the stimulant properties of drugs of abuse, including ethanol, in mammals and in the fruit fly Drosophila. The neural substrates for the stimulant actions of ethanol in flies are not known. We show that a subset of dopamine neurons and their targets, through the action of the D1-like dopamine receptor DopR, promote locomotor activation in response to acute ethanol exposure. A bilateral pair of dopaminergic neurons in the fly brain mediates the enhanced locomotor activity induced by ethanol exposure, and promotes locomotion when directly activated. These neurons project to the central complex ellipsoid body, a structure implicated in regulating motor behaviors. Ellipsoid body neurons are required for ethanol-induced locomotor activity and they express DopR. Elimination of DopR blunts the locomotor activating effects of ethanol, and this behavior can be restored by selective expression of DopR in the ellipsoid body. These data tie the activity of defined dopamine neurons to D1-like DopR-expressing neurons to form a neural circuit that governs acute responding to ethanol.

Stress-Induced CDK5 Activation Disrupts Axonal Transport via Lis1/Ndel1/Dynein.

PubMed

Klinman, Eva; Holzbaur, Erika L F

2015-07-21

Axonal transport is essential for neuronal function, and defects in transport are associated with multiple neurodegenerative diseases. Aberrant cyclin-dependent kinase 5 (CDK5) activity, driven by the stress-induced activator p25, also is observed in these diseases. Here we show that elevated CDK5 activity increases the frequency of nonprocessive events for a range of organelles, including lysosomes, autophagosomes, mitochondria, and signaling endosomes. Transport disruption induced by aberrant CDK5 activation depends on the Lis1/Ndel1 complex, which directly regulates dynein activity. CDK5 phosphorylation of Ndel1 favors a high affinity Lis1/Ndel/dynein complex that blocks the ATP-dependent release of dynein from microtubules, inhibiting processive motility of dynein-driven cargo. Similar transport defects observed in neurons from a mouse model of amyotrophic lateral sclerosis are rescued by CDK5 inhibition. Together, these studies identify CDK5 as a Lis1/Ndel1-dependent regulator of transport in stressed neurons, and suggest that dysregulated CDK5 activity contributes to the transport deficits observed during neurodegeneration. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Glucosensing by GnRH Neurons: Inhibition by Androgens and Involvement of AMP-Activated Protein Kinase

PubMed Central

Roland, Alison V.

2011-01-01

GnRH neurons integrate steroidal and metabolic cues to regulate fertility centrally. Central glucoprivation reduces LH secretion, which is governed by GnRH release, suggesting GnRH neuron activity is modulated by glucose availability. Here we tested whether GnRH neurons can sense changes in extracellular glucose, and whether glucosensing is altered by the steroids dihydrotestosterone (DHT) and/or estradiol (E). Extracellular recordings were made from GnRH neurons in brain slices from ovariectomized (OVX) mice ± DHT and/or E implants. Firing rate was reduced by a switch from 4.5 to 0.2 mm glucose in cells from OVX, OVX+E, and OVX+DHT+E mice, but not OVX+DHT mice. This suggests that androgens reduce the sensitivity of GnRH neurons to changes in extracellular glucose, but E mitigates this effect. Next we investigated potential mechanisms. In the presence of the ATP-sensitive potassium channel antagonist tolbutamide, glucosensing persisted. In contrast, glucosensing was attenuated in the presence of compound C, an antagonist of AMP-activated protein kinase (AMPK), suggesting a role for AMPK in glucosensing. The AMPK activator N1-(b-d-ribofuranosyl)-5-aminoimidazole-4-carboxamide (AICAR) mimicked the effect of low glucose and was less effective in cells from DHT-treated mice. The effect of DHT to diminish responses to low glucose and AICAR was abolished by blockade of fast synaptic transmission. Both AICAR and low glucose activated a current with a reversal potential near −50 mV, suggesting a nonspecific cation current. These studies indicate that glucosensing is one mechanism by which GnRH neurons sense fuel availability and point to a novel role for AMPK in the central regulation of fertility. PMID:21393446

Cholesterol up-regulates neuronal G protein-gated inwardly rectifying potassium (GIRK) channel activity in the hippocampus.

PubMed

Bukiya, Anna N; Durdagi, Serdar; Noskov, Sergei; Rosenhouse-Dantsker, Avia

2017-04-14

Hypercholesterolemia is a well known risk factor for the development of neurodegenerative disease. However, the underlying mechanisms are mostly unknown. In recent years, it has become increasingly evident that cholesterol-driven effects on physiology and pathophysiology derive from its ability to alter the function of a variety of membrane proteins including ion channels. Yet, the effect of cholesterol on G protein-gated inwardly rectifying potassium (GIRK) channels expressed in the brain is unknown. GIRK channels mediate the actions of inhibitory brain neurotransmitters. As a result, loss of GIRK function can enhance neuron excitability, whereas gain of GIRK function can reduce neuronal activity. Here we show that in rats on a high-cholesterol diet, cholesterol levels in hippocampal neurons are increased. We also demonstrate that cholesterol plays a critical role in modulating neuronal GIRK currents. Specifically, cholesterol enrichment of rat hippocampal neurons resulted in enhanced channel activity. In accordance, elevated currents upon cholesterol enrichment were also observed in Xenopus oocytes expressing GIRK2 channels, the primary GIRK subunit expressed in the brain. Furthermore, using planar lipid bilayers, we show that although cholesterol did not affect the unitary conductance of GIRK2, it significantly enhanced the frequency of channel openings. Last, combining computational and functional approaches, we identified two putative cholesterol-binding sites in the transmembrane domain of GIRK2. These findings establish that cholesterol plays a critical role in modulating GIRK activity in the brain. Because up-regulation of GIRK function can reduce neuronal activity, our findings may lead to novel approaches for prevention and therapy of cholesterol-driven neurodegenerative disease. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

VMAT2-Mediated Neurotransmission from Midbrain Leptin Receptor Neurons in Feeding Regulation

PubMed Central

Lu, Yungang; Xu, Pingwen; Isingrini, Elsa; Xu, Yong

2017-01-01

Abstract Leptin receptors (LepRs) expressed in the midbrain contribute to the action of leptin on feeding regulation. The midbrain neurons release a variety of neurotransmitters including dopamine (DA), glutamate and GABA. However, which neurotransmitter mediates midbrain leptin action on feeding remains unclear. Here, we showed that midbrain LepR neurons overlap with a subset of dopaminergic, GABAergic and glutamatergic neurons. Specific removal of vesicular monoamine transporter 2 (VMAT2) in midbrain LepR neurons (KO mice) disrupted DA accumulation in vesicles, but failed to cause a significant change in the evoked release of either glutamate or GABA to downstream neurons. While KO mice showed no differences on chow, they presented a reduced high-fat diet (HFD) intake and resisted to HFD-induced obesity. Specific activation of midbrain LepR neurons promoted VMAT2-dependent feeding on chow and HFD. When tested with an intermittent access to HFD where first 2.5-h HFD eating (binge-like) and 24-h HFD feeding were measured, KO mice exhibited more binge-like, but less 24-h HFD feeding. Interestingly, leptin inhibited 24-h HFD feeding in controls but not in KO mice. Thus, VMAT2-mediated neurotransmission from midbrain LepR neurons contributes to both binge-like eating and HFD feeding regulation. PMID:28560316

Neurons in the pontomedullary reticular formation receive converging inputs from the hindlimb and labyrinth.

PubMed

Miller, Derek M; DeMayo, William M; Bourdages, George H; Wittman, Samuel R; Yates, Bill J; McCall, Andrew A

2017-04-01

The integration of inputs from vestibular and proprioceptive sensors within the central nervous system is critical to postural regulation. We recently demonstrated in both decerebrate and conscious cats that labyrinthine and hindlimb inputs converge onto vestibular nucleus neurons. The pontomedullary reticular formation (pmRF) also plays a key role in postural control, and additionally participates in regulating locomotion. Thus, we hypothesized that like vestibular nucleus neurons, pmRF neurons integrate inputs from the limb and labyrinth. To test this hypothesis, we recorded the responses of pmRF neurons to passive ramp-and-hold movements of the hindlimb and to whole-body tilts, in both decerebrate and conscious felines. We found that pmRF neuronal activity was modulated by hindlimb movement in the rostral-caudal plane. Most neurons in both decerebrate (83% of units) and conscious (61% of units) animals encoded both flexion and extension movements of the hindlimb. In addition, hindlimb somatosensory inputs converged with vestibular inputs onto pmRF neurons in both preparations. Pontomedullary reticular formation neurons receiving convergent vestibular and limb inputs likely participate in balance control by governing reticulospinal outflow.

Neurons in the pontomedullary reticular formation receive converging inputs from the hindlimb and labyrinth

PubMed Central

Miller, Derek M.; DeMayo, William M.; Bourdages, George H.; Wittman, Samuel; Yates, Bill J.; McCall, Andrew A.

2017-01-01

The integration of inputs from vestibular and proprioceptive sensors within the central nervous system is critical to postural regulation. We recently demonstrated in both decerebrate and conscious cats that labyrinthine and hindlimb inputs converge onto vestibular nucleus neurons. The pontomedullary reticular formation (pmRF) also plays a key role in postural control, and additionally participates in regulating locomotion. Thus, we hypothesized that like vestibular nucleus neurons, pmRF neurons integrate inputs from the limb and labyrinth. To test this hypothesis, we recorded the responses of pmRF neurons to passive ramp-and-hold movements of the hindlimb and to whole-body tilts, in both decerebrate and conscious felines. We found that pmRF neuronal activity was modulated by hindlimb movement in the rostral-caudal plane. Most neurons in both decerebrate (83% of units) and conscious (61% of units) animals encoded both flexion and extension movements of the hindlimb. Additionally, hindlimb somatosensory inputs converged with vestibular inputs onto pmRF neurons in both preparations. Pontomedullary reticular formation neurons receiving convergent vestibular and limb inputs likely participate in balance control by governing reticulospinal outflow. PMID:28188328

Prolyl Isomerase Pin1 Regulates Neuronal Differentiation via β-Catenin

PubMed Central

Nakamura, Kazuhiro; Kosugi, Isao; Lee, Daniel Y.; Hafner, Angela; Sinclair, David A.

2012-01-01

The Wnt/β-catenin pathway promotes proliferation of neural progenitor cells (NPCs) at early stages and induces neuronal differentiation from NPCs at late stages, but the molecular mechanisms that control this stage-specific response are unclear. Pin1 is a prolyl isomerase that regulates cell signaling uniquely by controlling protein conformation after phosphorylation, but its role in neuronal differentiation is not known. Here we found that whereas Pin1 depletion suppresses neuronal differentiation, Pin1 overexpression enhances it, without any effects on gliogenesis from NPCs in vitro. Consequently, Pin1-null mice have significantly fewer upper layer neurons in the motor cortex and severely impaired motor activity during the neonatal stage. A proteomic approach identified β-catenin as a major substrate for Pin1 in NPCs, in which Pin1 stabilizes β-catenin. As a result, Pin1 knockout leads to reduced β-catenin during differentiation but not proliferation of NPCs in developing brains. Importantly, defective neuronal differentiation in Pin1 knockout NPCs is fully rescued in vitro by overexpression of β-catenin but not a β-catenin mutant that fails to act as a Pin1 substrate. These results show that Pin1 is a novel regulator of NPC differentiation by acting on β-catenin and provides a new postphosphorylation signaling mechanism to regulate developmental stage-specific functioning of β-catenin signaling in neuronal differentiation. PMID:22645310

Regulation of Neuronal Cav3.1 Channels by Cyclin-Dependent Kinase 5 (Cdk5)

PubMed Central

González-Ramírez, Ricardo; González-Billault, Christian; Felix, Ricardo

2015-01-01

Low voltage-activated (LVA) T-type Ca2+ channels activate in response to subthreshold membrane depolarizations and therefore represent an important source of Ca2+ influx near the resting membrane potential. In neurons, these proteins significantly contribute to control relevant physiological processes including neuronal excitability, pacemaking and post-inhibitory rebound burst firing. Three subtypes of T-type channels (Cav3.1 to Cav3.3) have been identified, and using functional expression of recombinant channels diverse studies have validated the notion that T-type Ca2+ channels can be modulated by various endogenous ligands as well as by second messenger pathways. In this context, the present study reveals a previously unrecognized role for cyclin-dependent kinase 5 (Cdk5) in the regulation of native T-type channels in N1E-115 neuroblastoma cells, as well as recombinant Cav3.1channels heterologously expressed in HEK-293 cells. Cdk5 and its co-activators play critical roles in the regulation of neuronal differentiation, cortical lamination, neuronal cell migration and axon outgrowth. Our results show that overexpression of Cdk5 causes a significant increase in whole cell patch clamp currents through T-type channels in N1E-115 cells, while siRNA knockdown of Cdk5 greatly reduced these currents. Consistent with this, overexpression of Cdk5 in HEK-293 cells stably expressing Cav3.1channels upregulates macroscopic currents. Furthermore, using site-directed mutagenesis we identified a major phosphorylation site at serine 2234 within the C-terminal region of the Cav3.1subunit. These results highlight a novel role for Cdk5 in the regulation of T-type Ca2+ channels. PMID:25760945

Regulation of neuronal cav3.1 channels by cyclin-dependent kinase 5 (Cdk5).

PubMed

Calderón-Rivera, Aida; Sandoval, Alejandro; González-Ramírez, Ricardo; González-Billault, Christian; Felix, Ricardo

2015-01-01

Low voltage-activated (LVA) T-type Ca2+ channels activate in response to subthreshold membrane depolarizations and therefore represent an important source of Ca2+ influx near the resting membrane potential. In neurons, these proteins significantly contribute to control relevant physiological processes including neuronal excitability, pacemaking and post-inhibitory rebound burst firing. Three subtypes of T-type channels (Cav3.1 to Cav3.3) have been identified, and using functional expression of recombinant channels diverse studies have validated the notion that T-type Ca2+ channels can be modulated by various endogenous ligands as well as by second messenger pathways. In this context, the present study reveals a previously unrecognized role for cyclin-dependent kinase 5 (Cdk5) in the regulation of native T-type channels in N1E-115 neuroblastoma cells, as well as recombinant Cav3.1channels heterologously expressed in HEK-293 cells. Cdk5 and its co-activators play critical roles in the regulation of neuronal differentiation, cortical lamination, neuronal cell migration and axon outgrowth. Our results show that overexpression of Cdk5 causes a significant increase in whole cell patch clamp currents through T-type channels in N1E-115 cells, while siRNA knockdown of Cdk5 greatly reduced these currents. Consistent with this, overexpression of Cdk5 in HEK-293 cells stably expressing Cav3.1channels upregulates macroscopic currents. Furthermore, using site-directed mutagenesis we identified a major phosphorylation site at serine 2234 within the C-terminal region of the Cav3.1subunit. These results highlight a novel role for Cdk5 in the regulation of T-type Ca2+ channels.

Functional and morphological characterization of glutamate transporters in the rat locus coeruleus

PubMed Central

Medrano, M C; Gerrikagoitia, I; Martínez-Millán, L; Mendiguren, A; Pineda, J

2013-01-01

Background and Purpose Excitatory amino acid transporters (EAATs) in the CNS contribute to the clearance of glutamate released during neurotransmission. The aim of this study was to explore the role of EAATs in the regulation of locus coeruleus (LC) neurons by glutamate. Experimental Approach We measured the effect of different EAAT subtype inhibitors/enhancers on glutamate- and KCl-induced activation of LC neurons in rat slices. EAAT2–3 expression in the LC was also characterized by immunohistochemistry. Key Results The EAAT2–5 inhibitor DL-threo-β-benzyloxaspartic acid (100 μM), but not the EAAT2, 4, 5 inhibitor L-trans-pyrrolidine-2,4-dicarboxylic acid (100 μM) or the EAAT2 inhibitor dihydrokainic acid (DHK; 100 μM), enhanced the glutamate- and KCl-induced activation of the firing rate of LC neurons. These effects were blocked by ionotropic, but not metabotrobic, glutamate receptor antagonists. DHK (100 μM) was the only EAAT inhibitor that increased the spontaneous firing rate of LC cells, an effect that was due to inhibition of EAAT2 and subsequent AMPA receptor activation. Chronic treatment with ceftriaxone (200 mg·kg−1 i.p., once daily, 7 days), an EAAT2 expression enhancer, increased the actions of glutamate and DHK, suggesting a functional impact of EAAT2 up-regulation on the glutamatergic system. Immuhistochemical data revealed the presence of EAAT2 and EAAT3 surrounding noradrenergic neurons and EAAT2 on glial cells in the LC. Conclusions and Implications These results remark the importance of EAAT2 and EAAT3 in the regulation of rat LC by glutamate. Neuronal EAAT3 would be responsible for terminating the action of synaptically released glutamate, whereas glial EAAT2 would regulate tonic glutamate concentrations in this nucleus. PMID:23638698

Maintenance of neural activities in torpid Rhinolophus ferrumequinum bats revealed by 2D gel-based proteome analysis.

PubMed

Yin, Qiuyuan; Zhang, Yijian; Dong, Dong; Lei, Ming; Zhang, Shuyi; Liao, Chen-Chung; Pan, Yi-Hsuan

2017-08-01

Bats are the only mammals capable of self-powered flying. Many bat species hibernate in winter. A reversible control of cerebral activities is critical for bats to accommodate a repeated torpor-arousal cycle during hibernation. Little is known about the molecular mechanisms that regulate neuronal activities in torpid bats. In this study, Rhinolophus ferrumequinum bat brain proteins were fractionated, and their abundance in active and torpid states was compared. Results of 2D gel-based proteomics showed that 38% of identified proteins with a significant change in abundance are involved in synaptic vesicle recycling and cytoskeletal integrity. Changes in the abundance of proteins related to RNA splicing, proteostasis, redox homeostasis, mitochondrial function, and energy metabolism were also detected. In addition, the levels of GNAO1 (guanine nucleotide-binding protein G αo subunit), an important modulator of neuronal transmembrane signaling, were significantly increased in the insoluble protein fraction of torpid bats; this may be due to GNAO1 palmitoylation making it insoluble. Our data provide molecular evidence for the maintenance of neuronal activities in torpid bats and suggest that a reversible palmitoylation of the G protein plays a role in the regulation of neuronal activities during bat hibernation. Copyright © 2017 Elsevier B.V. All rights reserved.

Endocytosis contributes to BMP2-induced Smad signalling and neuronal growth.

PubMed

Hegarty, Shane V; Sullivan, Aideen M; O'Keeffe, Gerard W

2017-03-16

Bone morphogenetic protein 2 (BMP2) is a neurotrophic factor which induces the growth of midbrain dopaminergic (DA) neurons in vitro and in vivo, and its neurotrophic effects have been shown to be dependent on activation of BMP receptors (BMPRs) and Smad 1/5/8 signalling. However, the precise intracellular cascades that regulate BMP2-BMPR-Smad-signalling-induced neurite growth remain unknown. Endocytosis has been shown to regulate Smad 1/5/8 signalling and differentiation induced by BMPs. However, these studies were carried out in non-neural cells. Indeed, there are scant reports regarding the role of endocytosis in BMP-Smad signalling in neurons. To address this, and to further characterise the mechanisms regulating the neurotrophic effects of BMP2, the present study examined the role of dynamin-dependent endocytosis in BMP2-induced Smad signalling and neurite growth in the SH-SY5Y neuronal cell line. The activation, temporal kinetics and magnitude of Smad 1/5/8 signalling induced by BMP2 were significantly attenuated by dynasore-mediated inhibition of endocytosis in SH-SY5Y cells. Furthermore, BMP2-induced increases in neurite length and neurite branching in SH-SY5Y cells were significantly reduced following inhibition of dynamin-dependent endocytosis using dynasore. This study demonstrates that BMP2-induced Smad signalling and neurite growth is regulated by dynamin-dependent endocytosis in a model of human midbrain dopaminergic neurons. Copyright © 2017 Elsevier B.V. All rights reserved.

The insulator protein BEAF-32 is required for Hippo pathway activity in the terminal differentiation of neuronal subtypes.

PubMed

Jukam, David; Viets, Kayla; Anderson, Caitlin; Zhou, Cyrus; DeFord, Peter; Yan, Jenny; Cao, Jinshuai; Johnston, Robert J

2016-07-01

The Hippo pathway is crucial for not only normal growth and apoptosis but also cell fate specification during development. What controls Hippo pathway activity during cell fate specification is incompletely understood. In this article, we identify the insulator protein BEAF-32 as a regulator of Hippo pathway activity in Drosophila photoreceptor differentiation. Though morphologically uniform, the fly eye is composed of two subtypes of R8 photoreceptor neurons defined by expression of light-detecting Rhodopsin proteins. In one R8 subtype, active Hippo signaling induces Rhodopsin 6 (Rh6) and represses Rhodopsin 5 (Rh5), whereas in the other subtype, inactive Hippo signaling induces Rh5 and represses Rh6. The activity state of the Hippo pathway in R8 cells is determined by the expression of warts, a core pathway kinase, which interacts with the growth regulator melted in a double-negative feedback loop. We show that BEAF-32 is required for expression of warts and repression of melted Furthermore, BEAF-32 plays a second role downstream of Warts to induce Rh6 and prevent Rh5 fate. BEAF-32 is dispensable for Warts feedback, indicating that BEAF-32 differentially regulates warts and Rhodopsins. Loss of BEAF-32 does not noticeably impair the functions of the Hippo pathway in eye growth regulation. Our study identifies a context-specific regulator of Hippo pathway activity in post-mitotic neuronal fate, and reveals a developmentally specific role for a broadly expressed insulator protein. © 2016. Published by The Company of Biologists Ltd.

Developmental regulation of N-methyl-D-aspartate- and kainate-type glutamate receptor expression in the rat spinal cord

NASA Technical Reports Server (NTRS)

Stegenga, S. L.; Kalb, R. G.

2001-01-01

Spinal motor neurons undergo experience-dependent development during a critical period in early postnatal life. It has been suggested that the repertoire of glutamate receptor subunits differs between young and mature motor neurons and contributes to this activity-dependent development. In the present study we examined the expression patterns of N-methyl-D-aspartate- and kainate-type glutamate receptor subunits during the postnatal maturation of the spinal cord. Young motor neurons express much higher levels of the N-methyl-D-aspartate receptor subunit NR1 than do adult motor neurons. Although there are eight potential splice variants of NR1, only a subgroup is expressed by motor neurons. With respect to NR2 receptor subunits, young motor neurons express NR2A and C, while adult motor neurons express only NR2A. Young motor neurons express kainate receptor subunits GluR5, 6 and KA2 but we are unable to detect these or any other kainate receptor subunits in the adult spinal cord. Other spinal cord regions display a distinct pattern of developmental regulation of N-methyl-D-aspartate and kainate receptor subunit expression in comparison to motor neurons. Our findings indicate a precise spatio-temporal regulation of individual subunit expression in the developing spinal cord. Specific combinations of subunits in developing neurons influence their excitable properties and could participate in the emergence of adult neuronal form and function.

A transgenic mouse for imaging activity-dependent dynamics of endogenous Arc mRNA in live neurons.

PubMed

Das, Sulagna; Moon, Hyungseok C; Singer, Robert H; Park, Hye Yoon

2018-06-01

Localized translation plays a crucial role in synaptic plasticity and memory consolidation. However, it has not been possible to follow the dynamics of memory-associated mRNAs in living neurons in response to neuronal activity in real time. We have generated a novel mouse model where the endogenous Arc/Arg3.1 gene is tagged in its 3' untranslated region with stem-loops that bind a bacteriophage PP7 coat protein (PCP), allowing visualization of individual mRNAs in real time. The physiological response of the tagged gene to neuronal activity is identical to endogenous Arc and reports the true dynamics of Arc mRNA from transcription to degradation. The transcription dynamics of Arc in cultured hippocampal neurons revealed two novel results: (i) A robust transcriptional burst with prolonged ON state occurs after stimulation, and (ii) transcription cycles continue even after initial stimulation is removed. The correlation of stimulation with Arc transcription and mRNA transport in individual neurons revealed that stimulus-induced Ca 2+ activity was necessary but not sufficient for triggering Arc transcription and that blocking neuronal activity did not affect the dendritic transport of newly synthesized Arc mRNAs. This mouse will provide an important reagent to investigate how individual neurons transduce activity into spatiotemporal regulation of gene expression at the synapse.

PINK1 Primes Parkin-Mediated Ubiquitination of PARIS in Dopaminergic Neuronal Survival.

PubMed

Lee, Yunjong; Stevens, Daniel A; Kang, Sung-Ung; Jiang, Haisong; Lee, Yun-Il; Ko, Han Seok; Scarffe, Leslie A; Umanah, George E; Kang, Hojin; Ham, Sangwoo; Kam, Tae-In; Allen, Kathleen; Brahmachari, Saurav; Kim, Jungwoo Wren; Neifert, Stewart; Yun, Seung Pil; Fiesel, Fabienne C; Springer, Wolfdieter; Dawson, Valina L; Shin, Joo-Ho; Dawson, Ted M

2017-01-24

Mutations in PTEN-induced putative kinase 1 (PINK1) and parkin cause autosomal-recessive Parkinson's disease through a common pathway involving mitochondrial quality control. Parkin inactivation leads to accumulation of the parkin interacting substrate (PARIS, ZNF746) that plays an important role in dopamine cell loss through repression of proliferator-activated receptor gamma coactivator-1-alpha (PGC-1α) promoter activity. Here, we show that PARIS links PINK1 and parkin in a common pathway that regulates dopaminergic neuron survival. PINK1 interacts with and phosphorylates serines 322 and 613 of PARIS to control its ubiquitination and clearance by parkin. PINK1 phosphorylation of PARIS alleviates PARIS toxicity, as well as repression of PGC-1α promoter activity. Conditional knockdown of PINK1 in adult mouse brains leads to a progressive loss of dopaminergic neurons in the substantia nigra that is dependent on PARIS. Altogether, these results uncover a function of PINK1 to direct parkin-PARIS-regulated PGC-1α expression and dopaminergic neuronal survival. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

Activation of serotonin 2C receptors in dopamine neurons inhibits binge-like eating in mice

PubMed Central

Xu, Pingwen; He, Yanlin; Cao, Xuehong; Valencia-Torres, Lourdes; Yan, Xiaofeng; Saito, Kenji; Wang, Chunmei; Yang, Yongjie; Hinton, Antentor; Zhu, Liangru; Shu, Gang; Myers, Martin G.; Wu, Qi; Tong, Qingchun; Heisler, Lora K.; Xu, Yong

2016-01-01

Background Neural networks that regulate binge eating remain to be identified, and effective treatments for binge eating are limited. Methods We combined neuroanatomical, pharmacological, electrophysiological, Cre-lox, and chemogenetic approaches to investigate the functions of 5-HT 2C receptor (5-HT2CR) expressed by dopamine (DA) neurons in the regulation of binge-like eating behavior in mice. Results We showed that 5-HT stimulates DA neural activity through a 5-HT2CR-mediated mechansim, and activation of this midbrain 5-HT-DA neural circuit effectively inhibits binge-like eating behavior in mice. Notably, 5-HT medications, including fluoxetine, d-Fenfluramine, and lorcaserin (a selective 5-HT2CR agonist), act upon 5-HT2CRs expressed by DA neurons to inhibit binge-like eating in mice. Conclusions We identified the 5-HT2CR population in DA neurons as one potential target for anti-binge therapies, and provided pre-clinical evidence that 5-HT2CR agonists could be used to treat binge eating. PMID:27516377

PPARγ ablation sensitizes proopiomelanocortin neurons to leptin during high-fat feeding

PubMed Central

Long, Lihong; Toda, Chitoku; Jeong, Jing Kwon; Horvath, Tamas L.; Diano, Sabrina

2014-01-01

Activation of central PPARγ promotes food intake and body weight gain; however, the identity of the neurons that express PPARγ and mediate the effect of this nuclear receptor on energy homeostasis is unknown. Here, we determined that selective ablation of PPARγ in murine proopiomelanocortin (POMC) neurons decreases peroxisome density, elevates reactive oxygen species, and induces leptin sensitivity in these neurons. Furthermore, ablation of PPARγ in POMC neurons preserved the interaction between mitochondria and the endoplasmic reticulum, which is dysregulated by HFD. Compared with control animals, mice lacking PPARγ in POMC neurons had increased energy expenditure and locomotor activity; reduced body weight, fat mass, and food intake; and improved glucose metabolism when exposed to high-fat diet (HFD). Finally, peripheral administration of either a PPARγ activator or inhibitor failed to affect food intake of mice with POMC-specific PPARγ ablation. Taken together, our data indicate that PPARγ mediates cellular, biological, and functional adaptations of POMC neurons to HFD, thereby regulating whole-body energy balance. PMID:25083994

PPARγ ablation sensitizes proopiomelanocortin neurons to leptin during high-fat feeding.

PubMed

Long, Lihong; Toda, Chitoku; Jeong, Jing Kwon; Horvath, Tamas L; Diano, Sabrina

2014-09-01

Activation of central PPARγ promotes food intake and body weight gain; however, the identity of the neurons that express PPARγ and mediate the effect of this nuclear receptor on energy homeostasis is unknown. Here, we determined that selective ablation of PPARγ in murine proopiomelanocortin (POMC) neurons decreases peroxisome density, elevates reactive oxygen species, and induces leptin sensitivity in these neurons. Furthermore, ablation of PPARγ in POMC neurons preserved the interaction between mitochondria and the endoplasmic reticulum, which is dysregulated by HFD. Compared with control animals, mice lacking PPARγ in POMC neurons had increased energy expenditure and locomotor activity; reduced body weight, fat mass, and food intake; and improved glucose metabolism when exposed to high-fat diet (HFD). Finally, peripheral administration of either a PPARγ activator or inhibitor failed to affect food intake of mice with POMC-specific PPARγ ablation. Taken together, our data indicate that PPARγ mediates cellular, biological, and functional adaptations of POMC neurons to HFD, thereby regulating whole-body energy balance.

Dorsal Raphe Serotonin Neurons Mediate CO2-Induced Arousal from Sleep.

PubMed

Smith, Haleigh R; Leibold, Nicole K; Rappoport, Daniel A; Ginapp, Callie M; Purnell, Benton S; Bode, Nicole M; Alberico, Stephanie L; Kim, Young-Cho; Audero, Enrica; Gross, Cornelius T; Buchanan, Gordon F

2018-02-21

Arousal from sleep in response to CO 2 is a critical protective phenomenon. Dysregulation of CO 2 -induced arousal contributes to morbidity and mortality from prevalent diseases, such as obstructive sleep apnea and sudden infant death syndrome. Despite the critical nature of this protective reflex, the precise mechanism for CO 2 -induced arousal is unknown. Because CO 2 is a major regulator of breathing, prevailing theories suggest that activation of respiratory chemo- and mechano-sensors is required for CO 2 -induced arousal. However, populations of neurons that are not involved in the regulation of breathing are also chemosensitive. Among these are serotonin (5-HT) neurons in the dorsal raphe nucleus (DRN) that comprise a component of the ascending arousal system. We hypothesized that direct stimulation of these neurons with CO 2 could cause arousal from sleep independently of enhancing breathing. Dialysis of CO 2 -rich acidified solution into DRN, but not medullary raphe responsible for modulating breathing, caused arousal from sleep. Arousal was lost in mice with a genetic absence of 5-HT neurons, and with acute pharmacological or optogenetic inactivation of DRN 5-HT neurons. Here we demonstrate that CO 2 can cause arousal from sleep directly, without requiring enhancement of breathing, and that chemosensitive 5-HT neurons in the DRN critically mediate this arousal. Better understanding mechanisms underlying this protective reflex may lead to interventions to reduce disease-associated morbidity and mortality. SIGNIFICANCE STATEMENT Although CO 2 -induced arousal is critical to a number of diseases, the specific mechanism is not well understood. We previously demonstrated that serotonin (5-HT) neurons are important for CO 2 -induced arousal, as mice without 5-HT neurons do not arouse to CO 2 Many have interpreted this to mean that medullary 5-HT neurons that regulate breathing are important in this arousal mechanism. Here we found that direct application of CO 2 -rich aCSF to the dorsal raphe nucleus, but not the medullary raphe, causes arousal from sleep, and that this arousal was lost with genetic ablation or acute inhibition of 5-HT neurons. We propose that 5-HT neurons in the dorsal raphe nucleus can be activated directly by CO 2 to cause arousal independently of respiratory activation. Copyright © 2018 the authors 0270-6474/18/381915-11$15.00/0.

Central Control of Brown Adipose Tissue Thermogenesis

PubMed Central

Morrison, Shaun F.; Madden, Christopher J.; Tupone, Domenico

2011-01-01

Thermogenesis, the production of heat energy, is an essential component of the homeostatic repertoire to maintain body temperature during the challenge of low environmental temperature and plays a key role in elevating body temperature during the febrile response to infection. Mitochondrial oxidation in brown adipose tissue (BAT) is a significant source of neurally regulated metabolic heat production in many species from mouse to man. BAT thermogenesis is regulated by neural networks in the central nervous system which responds to feedforward afferent signals from cutaneous and core body thermoreceptors and to feedback signals from brain thermosensitive neurons to activate BAT sympathetic nerve activity. This review summarizes the research leading to a model of the feedforward reflex pathway through which environmental cold stimulates BAT thermogenesis and includes the influence on this thermoregulatory network of the pyrogenic mediator, prostaglandin E2, to increase body temperature during fever. The cold thermal afferent circuit from cutaneous thermal receptors, through second-order thermosensory neurons in the dorsal horn of the spinal cord ascends to activate neurons in the lateral parabrachial nucleus which drive GABAergic interneurons in the preoptic area (POA) to inhibit warm-sensitive, inhibitory output neurons of the POA. The resulting disinhibition of BAT thermogenesis-promoting neurons in the dorsomedial hypothalamus activates BAT sympathetic premotor neurons in the rostral ventromedial medulla, including the rostral raphe pallidus, which provide excitatory, and possibly disinhibitory, inputs to spinal sympathetic circuits to drive BAT thermogenesis. Other recently recognized central sites influencing BAT thermogenesis and energy expenditure are also described. PMID:22389645

Asymmetric localization of natural antisense RNA of neuropeptide sensorin in Aplysia sensory neurons during aging and activity.

PubMed

Kadakkuzha, Beena M; Liu, Xin-An; Narvaez, Maria; Kaye, Alexandra; Akhmedov, Komolitdin; Puthanveettil, Sathyanarayanan V

2014-01-01

Despite the advances in our understanding of transcriptome, regulation and function of its non-coding components continue to be poorly understood. Here we searched for natural antisense transcript for sensorin (NAT-SRN), a neuropeptide expressed in the presynaptic sensory neurons of gill-withdrawal reflex of the marine snail Aplysia californica. Sensorin (SRN) has a key role in learning and long-term memory storage in Aplysia. We have now identified NAT-SRN in the central nervous system (CNS) and have confirmed its expression by northern blotting and fluorescent RNA in situ hybridization. Quantitative analysis of NAT-SRN in micro-dissected cell bodies and processes of sensory neurons suggest that NAT-SRN is present in the distal neuronal processes along with sense transcripts. Importantly, aging is associated with reduction in levels of NAT-SRN in sensory neuron processes. Furthermore, we find that forskolin, an activator of CREB signaling, differentially alters the distribution of SRN and NAT-SRN. These studies reveal novel insights into physiological regulation of natural antisense RNAs.

A PDF/NPF neuropeptide signaling circuitry of male Drosophila melanogaster controls rival-induced prolonged mating.

PubMed

Kim, Woo Jae; Jan, Lily Yeh; Jan, Yuh Nung

2013-12-04

A primary function of males for many species involves mating with females for reproduction. Drosophila melanogaster males respond to the presence of other males by prolonging mating duration to increase the chance of passing on their genes. To understand the basis of such complex behaviors, we examine the genetic network and neural circuits that regulate rival-induced Longer-Mating-Duration (LMD). Here, we identify a small subset of clock neurons in the male brain that regulate LMD via neuropeptide signaling. LMD requires the function of pigment-dispersing factor (PDF) in four s-LNv neurons and its receptor PDFR in two LNd neurons per hemisphere, as well as the function of neuropeptide F (NPF) in two neurons within the sexually dimorphic LNd region and its receptor NPFR1 in four s-LNv neurons per hemisphere. Moreover, rival exposure modifies the neuronal activities of a subset of clock neurons involved in neuropeptide signaling for LMD. Copyright © 2013 Elsevier Inc. All rights reserved.

A PDF/NPF neuropeptide signaling circuitry of male Drosophila melanogaster controls rival-induced prolonged mating

PubMed Central

Kim, Woo Jae; Jan, Lily Yeh; Jan, Yuh Nung

2013-01-01

SUMMARY A primary function of males for many species involves mating with females for reproduction. Drosophila melanogaster males respond to the presence of other males by prolonging mating duration to increase the chance of passing on their genes. To understand the basis of such complex behaviors, we examine the genetic network and neural circuits that regulate rival-induced longer mating duration (LMD). Here we identify a small subset of clock neurons in the male brain that regulate LMD via neuropeptide signaling. LMD requires the function of pigment-dispersing factor (PDF) in four s-LNv neurons and its receptor PDFR in two LNd neurons per hemisphere, as well as the function of neuropeptide F (NPF) in two neurons within the sexually dimorphic LNd region and its receptor NPFR1 in four s-LNv neurons per hemisphere. Moreover, rival exposure modifies the neuronal activities of a subset of clock neurons involved in neuropeptide signaling for LMD. PMID:24314729

Modulation of body temperature and LH secretion by hypothalamic KNDy (kisspeptin, neurokinin B and dynorphin) neurons: A novel hypothesis on the mechanism of hot flushes

PubMed Central

Rance, Naomi E.; Dacks, Penny A.; Mittelman-Smith, Melinda A.; Romanovsky, Andrej A.; Krajewski-Hall, Sally J.

2013-01-01

Despite affecting millions of individuals, the etiology of hot flushes remains unknown. Here we review the physiology of hot flushes, CNS pathways regulating heat-dissipation effectors, and effects of estrogen on thermoregulation in animal models. Based on the marked changes in hypothalamic kisspeptin, neurokinin B and dynorphin (KNDy) neurons in postmenopausal women, we hypothesize that KNDy neurons play a role in the mechanism of flushes. In the rat, KNDy neurons project to preoptic thermoregulatory areas that express the neurokinin 3 receptor (NK3R), the primary receptor for NKB. Furthermore, activation of NK3R in the median preoptic nucleus, part of the heat-defense pathway, reduces body temperature. Finally, ablation of KNDy neurons reduces cutaneous vasodilatation and partially blocks the effects of estrogen on thermoregulation. These data suggest that arcuate KNDy neurons relay estrogen signals to preoptic structures regulating heat-dissipation effectors, supporting the hypothesis that KNDy neurons participate in the generation of flushes. PMID:23872331

TRAF family member-associated NF-kappa B activator (TANK) expression increases in injured sensory neurons and is transcriptionally regulated by Sox11.

PubMed

Salerno, K M; Jing, X; Diges, C M; Davis, B M; Albers, K M

2013-02-12

Peripheral nerve injury evokes rapid and complex changes in gene transcription and cellular signaling pathways. Understanding how these changes are functionally related is essential for developing new approaches that accelerate and improve nerve regeneration. Toward this goal we found that nerve injury induces a rapid and significant up-regulation of the transcription factor Sox11 in dorsal root ganglia (DRG) neurons. Gain and loss of function studies have shown this increase is essential for normal axon regeneration. To determine how Sox11 impacts neuronal gene expression, DRG neurons were treated with Sox11 siRNA to identify potential transcriptional targets. One gene significantly reduced by Sox11 knockdown was TRAF (tumor necrosis factor (TNF) receptor-associated factor)-associated NF-κB activator (TANK). Here we show that TANK is expressed in DRG neurons, that TANK expression is increased in response to peripheral nerve injury and that Sox11 overexpression in vitro increases TANK expression. Injury and in vitro overexpression were also found to preferentially increase TANK transcript variant 3 and a larger TANK protein isoform. To determine if Sox11 regulates TANK transcription bioinformatic analysis was used to identify potential Sox-binding motifs within 5kbp of the TANK 5' untranslated region (UTR) across several mammalian genomes. Two sites in the mouse TANK gene were examined. Luciferase expression assays coupled with site-directed mutagenesis showed each site contributes to enhanced TANK promoter activity. In addition, chromatin immunoprecipitation assays showed direct Sox11 binding in regions containing the two identified Sox motifs in the mouse TANK 5'-UTR. These studies are the first to show that TANK is expressed in DRG neurons, that TANK is increased by peripheral nerve injury and that the regulation of TANK expression is, at least in part, controlled by the injury-associated transcription factor Sox11. Copyright © 2012 IBRO. Published by Elsevier Ltd. All rights reserved.

TRAF family member-associated NF-kappa B activator (TANK) expression increases in injured sensory neurons and is transcriptionally regulated by Sox11

PubMed Central

Salerno, Kathleen M.; Jing, Xiaotang; Diges, Charlotte M.; Davis, Brian M.; Albers, Kathryn M.

2013-01-01

Peripheral nerve injury evokes rapid and complex changes in gene transcription and cellular signaling pathways. Understanding how these changes are functionally related is essential for developing new approaches that accelerate and improve nerve regeneration. Towards this goal we found that nerve injury induces a rapid and significant up-regulation of the transcription factor Sox11 in dorsal root ganglia (DRG) neurons. Gain and loss of function studies have shown this increase is essential for normal axon regeneration. To determine how Sox11 impacts neuronal gene expression, DRG neurons were treated with Sox11 siRNA to identify potential transcriptional targets. One gene significantly reduced by Sox11 knockdown was TRAF (tumor necrosis factor (TNF) receptor-associated factor)-associated NF-κB activator (TANK). Here we show that TANK is expressed in DRG neurons, that TANK expression is increased in response to peripheral nerve injury and that Sox11 overexpression in vitro increases TANK expression. Injury and in vitro overexpression were also found to preferentially increase TANK transcript variant 3 and a larger TANK protein isoform. To determine if Sox11 regulates TANK transcription bioinformatic analysis was used to identify potential Sox binding motifs within 5 kbp of the TANK 5’ untranslated region (UTR) across several mammalian genomes. Two sites in the mouse TANK gene were examined. Luciferase expression assays coupled with site-directed mutagenesis showed each site contributes to enhanced TANK promoter activity. In addition, chromatin immunoprecipitation assays showed direct Sox11 binding in regions containing the two identified Sox motifs in the mouse TANK 5’-UTR. These studies are the first to show that TANK is expressed in DRG neurons, that TANK is increased by peripheral nerve injury and that the regulation of TANK expression is, at least in part, controlled by the injury-associated transcription factor Sox11. PMID:23201825

Cholesterol efflux is differentially regulated in neurons and astrocytes: implications for brain cholesterol homeostasis

PubMed Central

Chen, Jing; Zhang, Xiaolu; Kusumo, Handojo; Costa, Lucio G.; Guizzetti, Marina

2012-01-01

Disruption of cholesterol homeostasis in the central nervous system (CNS) has been associated with neurological, neurodegenerative, and neurodevelopmental disorders. The CNS is a closed system with regard to cholesterol homeostasis, as cholesterol-delivering lipoproteins from the periphery cannot pass the blood-brain-barrier and enter the brain. Different cell types in the brain have different functions in the regulation of cholesterol homeostasis, with astrocytes producing and releasing apolipoprotein E and lipoproteins, and neurons metabolizing cholesterol to 24(S)-hydroxycholesterol. We present evidence that astrocytes and neurons adopt different mechanisms also in regulating cholesterol efflux. We found that in astrocytes cholesterol efflux is induced by both lipid-free apolipoproteins and lipoproteins, while cholesterol removal from neurons is triggered only by lipoproteins. The main pathway by which apolipoproteins induce cholesterol efflux is through ABCA1. By upregulating ABCA1 levels and by inhibiting its activity and silencing its expression, we show that ABCA1 is involved in cholesterol efflux from astrocytes but not from neurons. Furthermore, our results suggest that ABCG1 is involved in cholesterol efflux to apolipoproteins and lipoproteins from astrocytes but not from neurons, while ABCG4, whose expression is much higher in neurons than astrocytes, is involved in cholesterol efflux from neurons but not astrocytes. These results indicate that different mechanisms regulate cholesterol efflux from neurons and astrocytes, reflecting the different roles that these cell types play in brain cholesterol homeostasis. These results are important in understanding cellular targets of therapeutic drugs under development for the treatments of conditions associated with altered cholesterol homeostasis in the CNS. PMID:23010475

The Serum Response Factor and a Putative Novel Transcription Factor Regulate Expression of the Immediate-Early Gene Arc/Arg3.1 in Cultured Cortical Neurons

PubMed Central

Pintchovski, Sean A.; Peebles, Carol L.; Kim, Hong Joo; Verdin, Eric; Finkbeiner, Steven

2010-01-01

The immediate-early effector gene Arc/Arg3.1 is robustly upregulated by synaptic activity associated with learning and memory. Here we show in primary cortical neuron culture that diverse stimuli induce Arc expression through new transcription. Searching for regulatory regions important for Arc transcription, we found nine DNaseI-sensitive nucleosome-depleted sites at this genomic locus. A reporter gene encompassing these sites responded to synaptic activity in an NMDA receptor–dependent manner, consistent with endogenous Arc mRNA. Responsiveness mapped to two enhancer regions ∼6.5 kb and ∼1.4 kb upstream of Arc. We dissected these regions further and found that the proximal enhancer contains a functional and conserved “Zeste-like” response element that binds a putative novel nuclear protein in neurons. Therefore, activity regulates Arc transcription partly by a novel signaling pathway. We also found that the distal enhancer has a functional and highly conserved serum response element. This element binds serum response factor, which is recruited by synaptic activity to regulate Arc. Thus, Arc is the first target of serum response factor that functions at synapses to mediate plasticity. PMID:19193899

MicroRNA-134 activity in somatostatin interneurons regulates H-Ras localization by repressing the palmitoylation enzyme, DHHC9.

PubMed

Chai, Sunghee; Cambronne, Xiaolu A; Eichhorn, Stephen W; Goodman, Richard H

2013-10-29

MicroRNA-134 (miR-134) serves as a widely accepted model for microRNA function in synaptic plasticity. In this model, synaptic activity stimulates miR-134 expression, which then regulates dendrite growth and spine formation. By using a ratiometric microRNA sensor, we found, unexpectedly, that miR-134 activity in cortical neurons was restricted to interneurons. Using an assay designed to trap microRNA-mRNA complexes, we determined that miR-134 interacted directly with the mRNA encoding the palmitoylation enzyme, DHHC9. This enzyme is known to palmitoylate H-Ras, a modification required for proper membrane trafficking. Treatment with bicuculline, a GABAA receptor antagonist, decreased DHHC9 expression in somatostatin-positive interneurons and membrane localization of an H-Ras reporter in a manner that depended on miR-134. Thus, although miR-134 has been proposed to affect all types of neurons, we showed that functionally active miR-134 is produced in only a selected population of neurons where it influences the expression of targets, such as DHHC9, that regulate membrane targeting of critical signaling molecules.

Differential Regulation of Action Potential Shape and Burst-Frequency Firing by BK and Kv2 Channels in Substantia Nigra Dopaminergic Neurons

PubMed Central

Kimm, Tilia; Khaliq, Zayd M.

2015-01-01

Little is known about the voltage-dependent potassium currents underlying spike repolarization in midbrain dopaminergic neurons. Studying mouse substantia nigra pars compacta dopaminergic neurons both in brain slice and after acute dissociation, we found that BK calcium-activated potassium channels and Kv2 channels both make major contributions to the depolarization-activated potassium current. Inhibiting Kv2 or BK channels had very different effects on spike shape and evoked firing. Inhibiting Kv2 channels increased spike width and decreased the afterhyperpolarization, as expected for loss of an action potential-activated potassium conductance. BK inhibition also increased spike width but paradoxically increased the afterhyperpolarization. Kv2 channel inhibition steeply increased the slope of the frequency–current (f–I) relationship, whereas BK channel inhibition had little effect on the f–I slope or decreased it, sometimes resulting in slowed firing. Action potential clamp experiments showed that both BK and Kv2 current flow during spike repolarization but with very different kinetics, with Kv2 current activating later and deactivating more slowly. Further experiments revealed that inhibiting either BK or Kv2 alone leads to recruitment of additional current through the other channel type during the action potential as a consequence of changes in spike shape. Enhancement of slowly deactivating Kv2 current can account for the increased afterhyperpolarization produced by BK inhibition and likely underlies the very different effects on the f–I relationship. The cross-regulation of BK and Kv2 activation illustrates that the functional role of a channel cannot be defined in isolation but depends critically on the context of the other conductances in the cell. SIGNIFICANCE STATEMENT This work shows that BK calcium-activated potassium channels and Kv2 voltage-activated potassium channels both regulate action potentials in dopamine neurons of the substantia nigra pars compacta. Although both channel types participate in action potential repolarization about equally, they have contrasting and partially opposite effects in regulating neuronal firing at frequencies typical of bursting. Our analysis shows that this results from their different kinetic properties, with fast-activating BK channels serving to short-circuit activation of Kv2 channels, which tend to slow firing by producing a deep afterhyperpolarization. The cross-regulation of BK and Kv2 activation illustrates that the functional role of a channel cannot be defined in isolation but depends critically on the context of the other conductances in the cell. PMID:26674866

Differential Regulation of Action Potential Shape and Burst-Frequency Firing by BK and Kv2 Channels in Substantia Nigra Dopaminergic Neurons.

PubMed

Kimm, Tilia; Khaliq, Zayd M; Bean, Bruce P

2015-12-16

Little is known about the voltage-dependent potassium currents underlying spike repolarization in midbrain dopaminergic neurons. Studying mouse substantia nigra pars compacta dopaminergic neurons both in brain slice and after acute dissociation, we found that BK calcium-activated potassium channels and Kv2 channels both make major contributions to the depolarization-activated potassium current. Inhibiting Kv2 or BK channels had very different effects on spike shape and evoked firing. Inhibiting Kv2 channels increased spike width and decreased the afterhyperpolarization, as expected for loss of an action potential-activated potassium conductance. BK inhibition also increased spike width but paradoxically increased the afterhyperpolarization. Kv2 channel inhibition steeply increased the slope of the frequency-current (f-I) relationship, whereas BK channel inhibition had little effect on the f-I slope or decreased it, sometimes resulting in slowed firing. Action potential clamp experiments showed that both BK and Kv2 current flow during spike repolarization but with very different kinetics, with Kv2 current activating later and deactivating more slowly. Further experiments revealed that inhibiting either BK or Kv2 alone leads to recruitment of additional current through the other channel type during the action potential as a consequence of changes in spike shape. Enhancement of slowly deactivating Kv2 current can account for the increased afterhyperpolarization produced by BK inhibition and likely underlies the very different effects on the f-I relationship. The cross-regulation of BK and Kv2 activation illustrates that the functional role of a channel cannot be defined in isolation but depends critically on the context of the other conductances in the cell. This work shows that BK calcium-activated potassium channels and Kv2 voltage-activated potassium channels both regulate action potentials in dopamine neurons of the substantia nigra pars compacta. Although both channel types participate in action potential repolarization about equally, they have contrasting and partially opposite effects in regulating neuronal firing at frequencies typical of bursting. Our analysis shows that this results from their different kinetic properties, with fast-activating BK channels serving to short-circuit activation of Kv2 channels, which tend to slow firing by producing a deep afterhyperpolarization. The cross-regulation of BK and Kv2 activation illustrates that the functional role of a channel cannot be defined in isolation but depends critically on the context of the other conductances in the cell. Copyright © 2015 the authors 0270-6474/15/3516404-14$15.00/0.

PKC regulates capsaicin-induced currents of dorsal root ganglion neurons in rats.

PubMed

Zhou, Y; Zhou, Z S; Zhao, Z Q

2001-10-01

Capsaicin activates a non-specific cation conductance in a subset of dorsal root ganglion (DRG) neurons. The inward current and membrane potential of acutely isolated DRG neurons were examined using whole-cell patch recording methods. We report here that the current and voltage responses activated by capsaicin were markedly increased by phorbol 12-myristate 13-acetate (PMA), an activator of protein kinase C (PKC). The mean current, after application of 0.3 microM PMA, was 153.5+/-5.7% of control (n=32) in Ca(2+)-free external solution and 181.6+/-6.8% of control (n=15) in standard external solution. Under current-clamp conditions, 0.3 microM PMA facilitated capsaicin-induced depolarization and action potential generation. Bindolylmaleimide I (BIM), a specific inhibitor of PKC activity, abolished the effect of PMA. In addition, capsaicin-evoked current was attenuated to 68.3+/-5.0% of control (n=13) by individual administration of 1 microM BIM in standard external solution, while 0.3 microM BIM did not have this effect. These data suggest that PKC can directly regulate the capsaicin response in DRG neurons, which could increase nociceptive sensory transmission and contribute to hyperalgesia.

SRF phosphorylation by glycogen synthase kinase-3 promotes axon growth in hippocampal neurons.

PubMed

Li, Cong L; Sathyamurthy, Aruna; Oldenborg, Anna; Tank, Dharmesh; Ramanan, Narendrakumar

2014-03-12

The growth of axons is an intricately regulated process involving intracellular signaling cascades and gene transcription. We had previously shown that the stimulus-dependent transcription factor, serum response factor (SRF), plays a critical role in regulating axon growth in the mammalian brain. However, the molecular mechanisms underlying SRF-dependent axon growth remains unknown. Here we report that SRF is phosphorylated and activated by GSK-3 to promote axon outgrowth in mouse hippocampal neurons. GSK-3 binds to and directly phosphorylates SRF on a highly conserved serine residue. This serine phosphorylation is necessary for SRF activity and for its interaction with MKL-family cofactors, MKL1 and MKL2, but not with TCF-family cofactor, ELK-1. Axonal growth deficits caused by GSK-3 inhibition could be rescued by expression of a constitutively active SRF. The SRF target gene and actin-binding protein, vinculin, is sufficient to overcome the axonal growth deficits of SRF-deficient and GSK-3-inhibited neurons. Furthermore, short hairpin RNA-mediated knockdown of vinculin also attenuated axonal growth. Thus, our findings reveal a novel phosphorylation and activation of SRF by GSK-3 that is critical for SRF-dependent axon growth in mammalian central neurons.

Neuron-to-glia signaling mediated by excitatory amino acid receptors regulates ErbB receptor function in astroglial cells of the neuroendocrine brain.

PubMed

Dziedzic, Barbara; Prevot, Vincent; Lomniczi, Alejandro; Jung, Heike; Cornea, Anda; Ojeda, Sergio R

2003-02-01

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

A PI3-kinase-mediated negative feedback regulates neuronal excitability.

PubMed

Howlett, Eric; Lin, Curtis Chun-Jen; Lavery, William; Stern, Michael

2008-11-01

Use-dependent downregulation of neuronal activity (negative feedback) can act as a homeostatic mechanism to maintain neuronal activity at a particular specified value. Disruption of this negative feedback might lead to neurological pathologies, such as epilepsy, but the precise mechanisms by which this feedback can occur remain incompletely understood. At one glutamatergic synapse, the Drosophila neuromuscular junction, a mutation in the group II metabotropic glutamate receptor gene (DmGluRA) increased motor neuron excitability by disrupting an autocrine, glutamate-mediated negative feedback. We show that DmGluRA mutations increase neuronal excitability by preventing PI3 kinase (PI3K) activation and consequently hyperactivating the transcription factor Foxo. Furthermore, glutamate application increases levels of phospho-Akt, a product of PI3K signaling, within motor nerve terminals in a DmGluRA-dependent manner. Finally, we show that PI3K increases both axon diameter and synapse number via the Tor/S6 kinase pathway, but not Foxo. In humans, PI3K and group II mGluRs are implicated in epilepsy, neurofibromatosis, autism, schizophrenia, and other neurological disorders; however, neither the link between group II mGluRs and PI3K, nor the role of PI3K-dependent regulation of Foxo in the control of neuronal excitability, had been previously reported. Our work suggests that some of the deficits in these neurological disorders might result from disruption of glutamate-mediated homeostasis of neuronal excitability.

GABAA receptor dependent synaptic inhibition rapidly tunes KCC2 activity via the Cl--sensitive WNK1 kinase.

PubMed

Heubl, Martin; Zhang, Jinwei; Pressey, Jessica C; Al Awabdh, Sana; Renner, Marianne; Gomez-Castro, Ferran; Moutkine, Imane; Eugène, Emmanuel; Russeau, Marion; Kahle, Kristopher T; Poncer, Jean Christophe; Lévi, Sabine

2017-11-24

The K + -Cl - co-transporter KCC2 (SLC12A5) tunes the efficacy of GABA A receptor-mediated transmission by regulating the intraneuronal chloride concentration [Cl - ] i . KCC2 undergoes activity-dependent regulation in both physiological and pathological conditions. The regulation of KCC2 by synaptic excitation is well documented; however, whether the transporter is regulated by synaptic inhibition is unknown. Here we report a mechanism of KCC2 regulation by GABA A receptor (GABA A R)-mediated transmission in mature hippocampal neurons. Enhancing GABA A R-mediated inhibition confines KCC2 to the plasma membrane, while antagonizing inhibition reduces KCC2 surface expression by increasing the lateral diffusion and endocytosis of the transporter. This mechanism utilizes Cl - as an intracellular secondary messenger and is dependent on phosphorylation of KCC2 at threonines 906 and 1007 by the Cl - -sensing kinase WNK1. We propose this mechanism contributes to the homeostasis of synaptic inhibition by rapidly adjusting neuronal [Cl - ] i to GABA A R activity.

Regulatory role of calpain in neuronal death

PubMed Central

Cheng, Si-ying; Wang, Shu-chao; Lei, Ming; Wang, Zhen; Xiong, Kun

2018-01-01

Calpains are a group of calcium-dependent proteases that are over activated by increased intracellular calcium levels under pathological conditions. A wide range of substrates that regulate necrotic, apoptotic and autophagic pathways are affected by calpain. Calpain plays a very important role in neuronal death and various neurological disorders. This review introduces recent research progress related to the regulatory mechanisms of calpain in neuronal death. Various neuronal programmed death pathways including apoptosis, autophagy and regulated necrosis can be divided into receptor interacting protein-dependent necroptosis, mitochondrial permeability transition-dependent necrosis, pyroptosis and poly (ADP-ribose) polymerase 1-mediated parthanatos. Calpains cleave series of key substrates that may lead to cell death or participate in cell death. Regarding the investigation of calpain-mediated programed cell death, it is necessary to identify specific inhibitors that inhibit calpain mediated neuronal death and nervous system diseases. PMID:29623944

Electrical Hyperexcitation of Lateral Ventral Pacemaker Neurons Desynchronizes Downstream Circadian Oscillators in the Fly Circadian Circuit and Induces Multiple Behavioral Periods

PubMed Central

Nitabach, Michael N.; Wu, Ying; Sheeba, Vasu; Lemon, William C.; Strumbos, John; Zelensky, Paul K.; White, Benjamin H.; Holmes, Todd C.

2008-01-01

Coupling of autonomous cellular oscillators is an essential aspect of circadian clock function but little is known about its circuit requirements. Functional ablation of the pigment-dispersing factor-expressing lateral ventral subset (LNV ) of Drosophila clock neurons abolishes circadian rhythms of locomotor activity. The hypothesis that LNVs synchronize oscillations in downstream clock neurons was tested by rendering the LNVs hyperexcitable via transgenic expression of a low activation threshold voltage-gated sodium channel. When the LNVs are made hyperexcitable, free-running behavioral rhythms decompose into multiple independent superimposed oscillations and the clock protein oscillations in the dorsal neuron 1 and 2 subgroups of clock neurons are phase-shifted. Thus, regulated electrical activity of the LNVs synchronize multiple oscillators in the fly circadian pacemaker circuit. PMID:16407545

Novel para-phenyl substituted diindolylmethanes protect against MPTP neurotoxicity and suppress glial activation in a mouse model of Parkinson's disease.

PubMed

De Miranda, Briana R; Popichak, Katriana A; Hammond, Sean L; Miller, James A; Safe, Stephen; Tjalkens, Ronald B

2015-02-01

The orphan nuclear receptor NR4A2 (Nurr1) constitutively regulates inflammatory gene expression in glial cells by suppressing DNA binding activity of NF-κB. We recently reported that novel 1,1-bis(3'-indolyl)-1-(p-substitutedphenyl)methane (C-DIM) compounds that activate NR4A family nuclear receptors in cancer lines also suppress inflammatory gene expression in primary astrocytes and prevent loss of dopaminergic neurons in mice exposed to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and probenecid (MPTPp). In this study, we postulated that the basis for this neuroprotection involves blockade of glial activation and subsequent expression of NF-κB-regulated inflammatory genes. To examine this mechanism, we treated transgenic NF-κB/EGFP reporter mice with MPTPp for 7 days (MPTPp7d) followed by daily oral gavage with either vehicle (corn oil; MPTPp14d) or C-DIMs containing p-methoxyphenyl (C-DIM5), p-hydroxyphenyl (C-DIM8), or p-chlorophenyl (C-DIM12) groups. Each compound conferred significant protection against progressive loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc), even when given after 7 days of dosing with MPTPp. C-DIM12 had the greatest neuroprotective activity in MPTPp-treated mice, and was also the most potent compound in suppressing activation of microglia and astrocytes, expression of cytokines and chemokines in quantitative polymerase chain reaction (qPCR) array studies, and in reducing expression of NF-κB/EGFP in the SN. C-DIM12 prevented nuclear export of Nurr1 in dopaminergic neurons and enhanced expression of the Nurr1-regulated proteins tyrosine hydroxylase and the dopamine transporter. These data indicate that NR4A-active C-DIM compounds protect against loss of dopamine neurons in the MPTPp model of PD by preventing glial-mediated neuronal injury and by supporting a dopaminergic phenotype in TH-positive neurons in the SNpc. © The Author 2014. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Ca2+-induced uncoupling of Aplysia bag cell neurons.

PubMed

Dargaei, Zahra; Standage, Dominic; Groten, Christopher J; Blohm, Gunnar; Magoski, Neil S

2015-02-01

Electrical transmission is a dynamically regulated form of communication and key to synchronizing neuronal activity. The bag cell neurons of Aplysia are a group of electrically coupled neuroendocrine cells that initiate ovulation by secreting egg-laying hormone during a prolonged period of synchronous firing called the afterdischarge. Accompanying the afterdischarge is an increase in intracellular Ca2+ and the activation of protein kinase C (PKC). We used whole cell recording from paired cultured bag cell neurons to demonstrate that electrical coupling is regulated by both Ca2+ and PKC. Elevating Ca2+ with a train of voltage steps, mimicking the onset of the afterdischarge, decreased junctional current for up to 30 min. Inhibition was most effective when Ca2+ entry occurred in both neurons. Depletion of Ca2+ from the mitochondria, but not the endoplasmic reticulum, also attenuated the electrical synapse. Buffering Ca2+ with high intracellular EGTA or inhibiting calmodulin kinase prevented uncoupling. Furthermore, activating PKC produced a small but clear decrease in junctional current, while triggering both Ca2+ influx and PKC inhibited the electrical synapse to a greater extent than Ca2+ alone. Finally, the amplitude and time course of the postsynaptic electrotonic response were attenuated after Ca2+ influx. A mathematical model of electrically connected neurons showed that excessive coupling reduced recruitment of the cells to fire, whereas less coupling led to spiking of essentially all neurons. Thus a decrease in electrical synapses could promote the afterdischarge by ensuring prompt recovery of electrotonic potentials or making the neurons more responsive to current spreading through the network. Copyright © 2015 the American Physiological Society.

The effects of prostaglandin E2 on the firing rate activity of thermosensitive and temperature insensitive neurons in the ventromedial preoptic area of the rat hypothalamus.

PubMed

Ranels, Heather J; Griffin, John D

2003-02-21

In response to an immune system challenge with lipopolysaccharide (LPS), recent work has shown that Fos immunoreactivity is displayed by neurons in the ventromedial preoptic area of the hypothalamus (VMPO). In addition, neurons in this region show distinct axonal projections to the anterior perifornical area (APFx) and the paraventricular nucleus (PVN). It has been hypothesized that neurons within the VMPO integrate their local responses to temperature with changes in firing activity that result from LPS induced production of prostaglandin E(2) (PGE(2)). This may be an important mechanism by which the set-point regulation of thermoeffector neurons in the APFx and PVN is altered, resulting in hyperthermia. To characterize the firing rate activity of VMPO neurons, single-unit recordings were made of neuronal extracellular activity in rat hypothalamic tissue slices. Based on the slope of firing rate as a function of tissue temperature, neurons were classified as either warm sensitive or temperature insensitive. Neurons were then treated with PGE(2) (200 nM) while tissue temperature was held at a constant level ( approximately 36 degrees C). The majority of temperature insensitive neurons responded to PGE(2) with an increase in firing rate activity, while warm sensitive neurons showed a reduction in firing rate. This suggests that both warm sensitive and temperature insensitive neurons in the VMPO may play critical and contrasting roles in the production of a fever during an acute phase response to infection.

CREB at the Crossroads of Activity-Dependent Regulation of Nervous System Development and Function.

PubMed

Belgacem, Yesser H; Borodinsky, Laura N

2017-01-01

The central nervous system is a highly plastic network of cells that constantly adjusts its functions to environmental stimuli throughout life. Transcription-dependent mechanisms modify neuronal properties to respond to external stimuli regulating numerous developmental functions, such as cell survival and differentiation, and physiological functions such as learning, memory, and circadian rhythmicity. The discovery and cloning of the cyclic adenosine monophosphate (cAMP) responsive element binding protein (CREB) constituted a big step toward deciphering the molecular mechanisms underlying neuronal plasticity. CREB was first discovered in learning and memory studies as a crucial mediator of activity-dependent changes in target gene expression that in turn impose long-lasting modifications of the structure and function of neurons. In this chapter, we review the molecular and signaling mechanisms of neural activity-dependent recruitment of CREB and its cofactors. We discuss the crosstalk between signaling pathways that imprints diverse spatiotemporal patterns of CREB activation allowing for the integration of a wide variety of stimuli.

The autism associated MET receptor tyrosine kinase engages early neuronal growth mechanism and controls glutamatergic circuits development in the forebrain

PubMed Central

Peng, Yun; Lu, Zhongming; Li, Guohui; Piechowicz, Mariel; Anderson, Miranda; Uddin, Yasin; Wu, Jie; Qiu, Shenfeng

2015-01-01

The human MET gene imparts a replicated risk for autism spectrum disorder (ASD), and is implicated in the structural and functional integrity of brain. MET encodes a receptor tyrosine kinase, MET, which plays a pleiotropic role in embryogenesis and modifies a large number of neurodevelopmental events. Very little is known, however, on how MET signaling engages distinct cellular events to collectively affect brain development in ASD-relevant disease domains. Here, we show that MET protein expression is dynamically regulated and compartmentalized in developing neurons. MET is heavily expressed in neuronal growth cones at early developmental stages and its activation engages small GTPase Cdc42 to promote neuronal growth, dendritic arborization, and spine formation. Genetic ablation of MET signaling in mouse dorsal pallium leads to altered neuronal morphology indicative of early functional maturation. In contrast, prolonged activation of MET represses the formation and functional maturation of glutamatergic synapses. Moreover, manipulating MET signaling levels in vivo in the developing prefrontal projection neurons disrupts the local circuit connectivity made onto these neurons. Therefore, normal time-delimited MET signaling is critical in regulating the timing of neuronal growth, glutamatergic synapse maturation and cortical circuit function. Dysregulated MET signaling may lead to pathological changes in forebrain maturation and connectivity, and thus contribute to the emergence of neurological symptoms associated with ASD. PMID:26728565

The impact of the glial spatial buffering on the K(+) Nernst potential.

PubMed

Noori, H R

2011-09-01

Astrocytes play a critical role in CNS metabolism, regulation of volume and ion homeostasis of the interstitial space. Of special relevance is their clearance of K(+) that is released by active neurons into the extracellular space. Mathematical analysis of a modified Nernst equation for the electrochemical equilibrium of neuronal plasma membranes, suggests that K(+) uptake by glial cells is not only relevant during neuronal activity but also has a non-neglectable impact on the basic electrical membrane properties, specifically the resting membrane potential, of neurons and might be clinically valuable as a factor in the genetics and epigenetics of the epilepsy and tuberous sclerosis complex.

Neuronal avalanches and coherence potentials

NASA Astrophysics Data System (ADS)

Plenz, D.

2012-05-01

The mammalian cortex consists of a vast network of weakly interacting excitable cells called neurons. Neurons must synchronize their activities in order to trigger activity in neighboring neurons. Moreover, interactions must be carefully regulated to remain weak (but not too weak) such that cascades of active neuronal groups avoid explosive growth yet allow for activity propagation over long-distances. Such a balance is robustly realized for neuronal avalanches, which are defined as cortical activity cascades that follow precise power laws. In experiments, scale-invariant neuronal avalanche dynamics have been observed during spontaneous cortical activity in isolated preparations in vitro as well as in the ongoing cortical activity of awake animals and in humans. Theory, models, and experiments suggest that neuronal avalanches are the signature of brain function near criticality at which the cortex optimally responds to inputs and maximizes its information capacity. Importantly, avalanche dynamics allow for the emergence of a subset of avalanches, the coherence potentials. They emerge when the synchronization of a local neuronal group exceeds a local threshold, at which the system spawns replicas of the local group activity at distant network sites. The functional importance of coherence potentials will be discussed in the context of propagating structures, such as gliders in balanced cellular automata. Gliders constitute local population dynamics that replicate in space after a finite number of generations and are thought to provide cellular automata with universal computation. Avalanches and coherence potentials are proposed to constitute a modern framework of cortical synchronization dynamics that underlies brain function.

Selective Ablation of GIRK Channels in Dopamine Neurons Alters Behavioral Effects of Cocaine in Mice.

PubMed

McCall, Nora M; Kotecki, Lydia; Dominguez-Lopez, Sergio; Marron Fernandez de Velasco, Ezequiel; Carlblom, Nicholas; Sharpe, Amanda L; Beckstead, Michael J; Wickman, Kevin

2017-02-01

The increase in dopamine (DA) neurotransmission stimulated by in vivo cocaine exposure is tempered by G protein-dependent inhibitory feedback mechanisms in DA neurons of the ventral tegmental area (VTA). G protein-gated inwardly rectifying K + (GIRK/Kir3) channels mediate the direct inhibitory effect of GABA B receptor (GABA B R) and D 2 DA receptor (D 2 R) activation in VTA DA neurons. Here we examined the effect of the DA neuron-specific loss of GIRK channels on D 2 R-dependent regulation of VTA DA neuron excitability and on cocaine-induced, reward-related behaviors. Selective ablation of Girk2 in DA neurons did not alter the baseline excitability of VTA DA neurons but significantly reduced the magnitude of D 2 R-dependent inhibitory somatodendritic currents and blunted the impact of D 2 R activation on spontaneous activity and neuronal excitability. Mice lacking GIRK channels in DA neurons exhibited increased locomotor activation in response to acute cocaine administration and an altered locomotor sensitization profile, as well as increased responding for and intake of cocaine in an intravenous self-administration test. These mice, however, showed unaltered cocaine-induced conditioned place preference. Collectively, our data suggest that feedback inhibition to VTA DA neurons, mediated by GIRK channel activation, tempers the locomotor stimulatory effect of cocaine while also modulating the reinforcing effect of cocaine in an operant-based self-administration task.

Regulation of Brain-Derived Neurotrophic Factor Exocytosis and Gamma-Aminobutyric Acidergic Interneuron Synapse by the Schizophrenia Susceptibility Gene Dysbindin-1.

PubMed

Yuan, Qiang; Yang, Feng; Xiao, Yixin; Tan, Shawn; Husain, Nilofer; Ren, Ming; Hu, Zhonghua; Martinowich, Keri; Ng, Julia S; Kim, Paul J; Han, Weiping; Nagata, Koh-Ichi; Weinberger, Daniel R; Je, H Shawn

2016-08-15

Genetic variations in dystrobrevin binding protein 1 (DTNBP1 or dysbindin-1) have been implicated as risk factors in the pathogenesis of schizophrenia. The encoded protein dysbindin-1 functions in the regulation of synaptic activity and synapse development. Intriguingly, a loss of function mutation in Dtnbp1 in mice disrupted both glutamatergic and gamma-aminobutyric acidergic transmission in the cerebral cortex; pyramidal neurons displayed enhanced excitability due to reductions in inhibitory synaptic inputs. However, the mechanism by which reduced dysbindin-1 activity causes inhibitory synaptic deficits remains unknown. We investigated the role of dysbindin-1 in the exocytosis of brain-derived neurotrophic factor (BDNF) from cortical excitatory neurons, organotypic brain slices, and acute slices from dysbindin-1 mutant mice and determined how this change in BDNF exocytosis transsynaptically affected the number of inhibitory synapses formed on excitatory neurons via whole-cell recordings, immunohistochemistry, and live-cell imaging using total internal reflection fluorescence microscopy. A decrease in dysbindin-1 reduces the exocytosis of BDNF from cortical excitatory neurons, and this reduction in BDNF exocytosis transsynaptically resulted in reduced inhibitory synapse numbers formed on excitatory neurons. Furthermore, application of exogenous BDNF rescued the inhibitory synaptic deficits caused by the reduced dysbindin-1 level in both cultured cortical neurons and slice cultures. Taken together, our results demonstrate that these two genes linked to risk for schizophrenia (BDNF and dysbindin-1) function together to regulate interneuron development and cortical network activity. This evidence supports the investigation of the association between dysbindin-1 and BDNF in humans with schizophrenia. Copyright © 2016 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

Regulated internalization of NMDA receptors drives PKD1-mediated suppression of the activity of residual cell-surface NMDA receptors.

PubMed

Fang, Xiao-Qian; Qiao, Haifa; Groveman, Bradley R; Feng, Shuang; Pflueger, Melissa; Xin, Wen-Kuan; Ali, Mohammad K; Lin, Shuang-Xiu; Xu, Jindong; Duclot, Florian; Kabbaj, Mohamed; Wang, Wei; Ding, Xin-Sheng; Santiago-Sim, Teresa; Jiang, Xing-Hong; Salter, Michael W; Yu, Xian-Min

2015-11-19

Constitutive and regulated internalization of cell surface proteins has been extensively investigated. The regulated internalization has been characterized as a principal mechanism for removing cell-surface receptors from the plasma membrane, and signaling to downstream targets of receptors. However, so far it is still not known whether the functional properties of remaining (non-internalized) receptor/channels may be regulated by internalization of the same class of receptor/channels. The N-methyl-D-aspartate receptor (NMDAR) is a principal subtype of glutamate-gated ion channel and plays key roles in neuronal plasticity and memory functions. NMDARs are well-known to undergo two types of regulated internalization - homologous and heterologous, which can be induced by high NMDA/glycine and DHPG, respectively. In the present work, we investigated effects of regulated NMDAR internalization on the activity of residual cell-surface NMDARs and neuronal functions. In electrophysiological experiments we discovered that the regulated internalization of NMDARs not only reduced the number of cell surface NMDARs but also caused an inhibition of the activity of remaining (non-internalized) surface NMDARs. In biochemical experiments we identified that this functional inhibition of remaining surface NMDARs was mediated by increased serine phosphorylation of surface NMDARs, resulting from the activation of protein kinase D1 (PKD1). Knockdown of PKD1 did not affect NMDAR internalization but prevented the phosphorylation and inhibition of remaining surface NMDARs and NMDAR-mediated synaptic functions. These data demonstrate a novel concept that regulated internalization of cell surface NMDARs not only reduces the number of NMDARs on the cell surface but also causes an inhibition of the activity of remaining surface NMDARs through intracellular signaling pathway(s). Furthermore, modulating the activity of remaining surface receptors may be an effective approach for treating receptor internalization-induced changes in neuronal functions of the CNS.

BDNF regulates the translation of a select group of mRNAs by a mammalian target of rapamycin-phosphatidylinositol 3-kinase-dependent pathway during neuronal development.

PubMed

Schratt, Gerhard M; Nigh, Elizabeth A; Chen, Wen G; Hu, Linda; Greenberg, Michael E

2004-08-18

Local regulation of mRNA translation plays an important role in axon guidance, synaptic development, and neuronal plasticity. Little is known, however, regarding the mechanisms that control translation in neurons, and only a few mRNAs have been identified that are locally translated within axon and dendrites. Using Affymetrix gene arrays to identify mRNAs that are newly associated with polysomes after exposure to BDNF, we identified subsets of mRNAs for which translation is enhanced in neurons at different developmental stages. In mature neurons, many of these mRNAs encode proteins that are known to function at synapses, including CamKIIalpha, NMDA receptor subunits, and the postsynaptic density (PSD) scaffolding protein Homer2. BDNF regulates the translation of Homer2 locally in the synaptodendritic compartment by activating translational initiation via a mammalian target of rapamycin-phosphatidylinositol 3-kinase-dependent pathway. These findings suggest that BDNF likely regulates synaptic function by inducing the local synthesis of numerous synaptic proteins. The local translation of the cytoskeleton-associated protein Homer2 in particular might have important implications for growth cone dynamics and dendritic spine development.

Regulation of GABAA receptors by fragile X mental retardation protein

PubMed Central

Liu, Baosong; Li, Lijun; Chen, Juan; Wang, Zefen; Li, Zhiqiang; Wan, Qi

2013-01-01

Fragile X syndrome (FXS) is caused by the loss of fragile X mental retardation protein (FMRP). The deficiency of GABAA receptors (GABAARs) is implicated in FXS. However, the underlying mechanisms remain unclear. To investigate the effect of FMRP on GABAARs, we transfected FMRP cDNAs in rat cortical neurons. We measured the protein expression of GABAARs and phosphatase PTEN, and recorded GABAAR-mediated whole-cell currents in the transfected neurons. We show that the transfection of FMRP cDNAs causes increased protein expression of GABAARs in cortical neurons, but GABAAR-mediated whole-cell currents are not potentiated by FMRP transfection. These results suggest the possibility that intracellular signaling antagonizing GABAAR activity may play a role in inhibiting GABAAR function in FMRP-transfected neurons. We further show that FMRP transfection results in an enhanced protein expression of PTEN, which contributes to the inhibition of GABAAR function in FMRP-transfected neurons. These results indicate that GABAARs are regulated by FMRP through both an up-regulation of GABAAR expression and a PTEN enhancement-induced inhibition of GABAAR function, suggesting that an abnormal regulation of GABAAR and PTEN by the loss of FMRP underlies the pathogenesis of FXS. PMID:24044036

Manganese- and 1-methyl-4-phenylpyridinium-induced neurotoxicity display differences in morphological, electrophysiological and genome-wide alterations: implications for idiopathic Parkinson's disease.

PubMed

Mythri, Rajeswara Babu; Raghunath, Narayana Reddy; Narwade, Santosh Chandrakant; Pandareesh, Mirazkar Dasharatha Rao; Sabitha, Kollarkandi Rajesh; Aiyaz, Mohamad; Chand, Bipin; Sule, Manas; Ghosh, Krittika; Kumar, Senthil; Shankarappa, Bhagyalakshmi; Soundararajan, Soundarya; Alladi, Phalguni Anand; Purushottam, Meera; Gayathri, Narayanappa; Deobagkar, Deepti Dileep; Laxmi, Thenkanidiyoor Rao; Srinivas Bharath, Muchukunte Mukunda

2017-11-01

Idiopathic Parkinson's disease and manganese-induced atypical parkinsonism are characterized by movement disorder and nigrostriatal pathology. Although clinical features, brain region involved and responsiveness to levodopa distinguish both, differences at the neuronal level are largely unknown. We studied the morphological, neurophysiological and molecular differences in dopaminergic neurons exposed to the Parkinson's disease toxin 1-methyl-4-phenylpyridinium ion (MPP + ) and manganese (Mn), followed by validation in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and Mn mouse models. Morphological analysis highlighted loss of neuronal processes in the MPP + and not the Mn model. Cellular network dynamics of dopaminergic neurons characterized by spike frequency and inter-spike intervals indicated major neuronal population (~ 93%) with slow discharge rates (0-5 Hz). While MPP + exposure suppressed the firing of these neurons, Mn neither suppressed nor elevated the neuronal activity. High-throughput transcriptomic analysis revealed up-regulation of 694 and 603 genes and down-regulation of 428 and 255 genes in the MPP + and Mn models respectively. Many differentially expressed genes were unique to either models and contributed to neuroinflammation, metabolic/mitochondrial function, apoptosis and nuclear function, synaptic plasticity, neurotransmission and cytoskeleton. Analysis of the Janus kinase-signal transducer and activator of transcription pathway with implications for neuritogenesis and neuronal proliferation revealed contrasting profile in both models. Genome-wide DNA methylomics revealed differences between both models and substantiated the epigenetic basis of the difference in the Janus kinase-signal transducer and activator of transcription pathway. We conclude that idiopathic Parkinson's disease and atypical parkinsonism have divergent neurotoxicological manifestation at the dopaminergic neuronal level with implications for pathobiology and evolution of novel therapeutics. Cover Image for this issue: doi. 10.1111/jnc.13821. © 2017 International Society for Neurochemistry.

Caspase inhibition in select olfactory neurons restores innate attraction behavior in aged Drosophila.

PubMed

Chihara, Takahiro; Kitabayashi, Aki; Morimoto, Michie; Takeuchi, Ken-ichi; Masuyama, Kaoru; Tonoki, Ayako; Davis, Ronald L; Wang, Jing W; Miura, Masayuki

2014-06-01

Sensory and cognitive performance decline with age. Neural dysfunction caused by nerve death in senile dementia and neurodegenerative disease has been intensively studied; however, functional changes in neural circuits during the normal aging process are not well understood. Caspases are key regulators of cell death, a hallmark of age-related neurodegeneration. Using a genetic probe for caspase-3-like activity (DEVDase activity), we have mapped age-dependent neuronal changes in the adult brain throughout the lifespan of Drosophila. Spatio-temporally restricted caspase activation was observed in the antennal lobe and ellipsoid body, brain structures required for olfaction and visual place memory, respectively. We also found that caspase was activated in an age-dependent manner in specific subsets of Drosophila olfactory receptor neurons (ORNs), Or42b and Or92a neurons. These neurons are essential for mediating innate attraction to food-related odors. Furthermore, age-induced impairments of neural transmission and attraction behavior could be reversed by specific inhibition of caspase in these ORNs, indicating that caspase activation in Or42b and Or92a neurons is responsible for altering animal behavior during normal aging.

Overactivity of Liver-Related Neurons in the Paraventricular Nucleus of the Hypothalamus: Electrophysiological Findings in db/db Mice

PubMed Central

Gao, Hong; Molinas, Adrien J.R.; Qiao, Xin

2017-01-01

Preautonomic neurons in the paraventricular nucleus (PVN) of the hypothalamus play a large role in the regulation of hepatic functions via the autonomic nervous system. Activation of hepatic sympathetic nerves increases glucose and lipid metabolism and contributes to the elevated hepatic glucose production observed in the type 2 diabetic condition. This augmented sympathetic output could originate from altered activity of liver-related PVN neurons. Remarkably, despite the importance of the brain-liver pathway, the cellular properties of liver-related neurons are not known. In this study, we provide the first evidence of overall activity of liver-related PVN neurons. Liver-related PVN neurons were identified with a retrograde, trans-synaptic, viral tracer in male lean and db/db mice and whole-cell patch-clamp recordings were conducted. In db/db mice, the majority of liver-related PVN neurons fired spontaneously; whereas, in lean mice the majority of liver-related PVN neurons were silent, indicating that liver-related PVN neurons are more active in db/db mice. Persistent, tonic inhibition was identified in liver-related PVN neurons; although, the magnitude of tonic inhibitory control was not different between lean and db/db mice. In addition, our study revealed that the transient receptor potential vanilloid type 1-dependent increase of excitatory neurotransmission was reduced in liver-related PVN neurons of db/db mice. These findings demonstrate plasticity of liver-related PVN neurons and a shift toward excitation in a diabetic mouse model. Our study suggests altered autonomic circuits at the level of the PVN, which can contribute to autonomic dysfunction and dysregulation of neural control of hepatic functions including glucose metabolism. SIGNIFICANCE STATEMENT A growing body of evidence suggests the importance of the autonomic control in the regulation of hepatic metabolism, which plays a major role in the development and progression of type 2 diabetes mellitus. Despite the importance of the brain-liver pathway, the overall activity of liver-related neurons in control and diabetic conditions is not known. This is a significant gap in knowledge, which prevents developing strategies to improve glucose homeostasis via altering the brain-liver pathway. One of the key findings of our study is the overall shift toward excitation in liver-related hypothalamic neurons in the diabetic condition. This overactivity may be one of the underlying mechanisms of elevated sympathetic activity known in metabolically compromised patients and animal models. PMID:29038244

Overactivity of Liver-Related Neurons in the Paraventricular Nucleus of the Hypothalamus: Electrophysiological Findings in db/db Mice.

PubMed

Gao, Hong; Molinas, Adrien J R; Miyata, Kayoko; Qiao, Xin; Zsombok, Andrea

2017-11-15

Preautonomic neurons in the paraventricular nucleus (PVN) of the hypothalamus play a large role in the regulation of hepatic functions via the autonomic nervous system. Activation of hepatic sympathetic nerves increases glucose and lipid metabolism and contributes to the elevated hepatic glucose production observed in the type 2 diabetic condition. This augmented sympathetic output could originate from altered activity of liver-related PVN neurons. Remarkably, despite the importance of the brain-liver pathway, the cellular properties of liver-related neurons are not known. In this study, we provide the first evidence of overall activity of liver-related PVN neurons. Liver-related PVN neurons were identified with a retrograde, trans-synaptic, viral tracer in male lean and db/db mice and whole-cell patch-clamp recordings were conducted. In db/db mice, the majority of liver-related PVN neurons fired spontaneously; whereas, in lean mice the majority of liver-related PVN neurons were silent, indicating that liver-related PVN neurons are more active in db/db mice. Persistent, tonic inhibition was identified in liver-related PVN neurons; although, the magnitude of tonic inhibitory control was not different between lean and db/db mice. In addition, our study revealed that the transient receptor potential vanilloid type 1-dependent increase of excitatory neurotransmission was reduced in liver-related PVN neurons of db/db mice. These findings demonstrate plasticity of liver-related PVN neurons and a shift toward excitation in a diabetic mouse model. Our study suggests altered autonomic circuits at the level of the PVN, which can contribute to autonomic dysfunction and dysregulation of neural control of hepatic functions including glucose metabolism. SIGNIFICANCE STATEMENT A growing body of evidence suggests the importance of the autonomic control in the regulation of hepatic metabolism, which plays a major role in the development and progression of type 2 diabetes mellitus. Despite the importance of the brain-liver pathway, the overall activity of liver-related neurons in control and diabetic conditions is not known. This is a significant gap in knowledge, which prevents developing strategies to improve glucose homeostasis via altering the brain-liver pathway. One of the key findings of our study is the overall shift toward excitation in liver-related hypothalamic neurons in the diabetic condition. This overactivity may be one of the underlying mechanisms of elevated sympathetic activity known in metabolically compromised patients and animal models. Copyright © 2017 the authors 0270-6474/17/3711140-11$15.00/0.

Visual perception and imagery: a new molecular hypothesis.

PubMed

Bókkon, I

2009-05-01

Here, we put forward a redox molecular hypothesis about the natural biophysical substrate of visual perception and visual imagery. This hypothesis is based on the redox and bioluminescent processes of neuronal cells in retinotopically organized cytochrome oxidase-rich visual areas. Our hypothesis is in line with the functional roles of reactive oxygen and nitrogen species in living cells that are not part of haphazard process, but rather a very strict mechanism used in signaling pathways. We point out that there is a direct relationship between neuronal activity and the biophoton emission process in the brain. Electrical and biochemical processes in the brain represent sensory information from the external world. During encoding or retrieval of information, electrical signals of neurons can be converted into synchronized biophoton signals by bioluminescent radical and non-radical processes. Therefore, information in the brain appears not only as an electrical (chemical) signal but also as a regulated biophoton (weak optical) signal inside neurons. During visual perception, the topological distribution of photon stimuli on the retina is represented by electrical neuronal activity in retinotopically organized visual areas. These retinotopic electrical signals in visual neurons can be converted into synchronized biophoton signals by radical and non-radical processes in retinotopically organized mitochondria-rich areas. As a result, regulated bioluminescent biophotons can create intrinsic pictures (depictive representation) in retinotopically organized cytochrome oxidase-rich visual areas during visual imagery and visual perception. The long-term visual memory is interpreted as epigenetic information regulated by free radicals and redox processes. This hypothesis does not claim to solve the secret of consciousness, but proposes that the evolution of higher levels of complexity made the intrinsic picture representation of the external visual world possible by regulated redox and bioluminescent reactions in the visual system during visual perception and visual imagery.

Coordinated regulation of neuronal mRNA steady-state levels through developmentally controlled intron retention

PubMed Central

Yap, Karen; Lim, Zhao Qin; Khandelia, Piyush; Friedman, Brad; Makeyev, Eugene V.

2012-01-01

Differentiated cells acquire unique structural and functional traits through coordinated expression of lineage-specific genes. An extensive battery of genes encoding components of the synaptic transmission machinery and specialized cytoskeletal proteins is activated during neurogenesis, but the underlying regulation is not well understood. Here we show that genes encoding critical presynaptic proteins are transcribed at a detectable level in both neurons and nonneuronal cells. However, in nonneuronal cells, the splicing of 3′-terminal introns within these genes is repressed by the polypyrimidine tract-binding protein (Ptbp1). This inhibits the export of incompletely spliced mRNAs to the cytoplasm and triggers their nuclear degradation. Clearance of these intron-containing transcripts occurs independently of the nonsense-mediated decay (NMD) pathway but requires components of the nuclear RNA surveillance machinery, including the nuclear pore-associated protein Tpr and the exosome complex. When Ptbp1 expression decreases during neuronal differentiation, the regulated introns are spliced out, thus allowing the accumulation of translation-competent mRNAs in the cytoplasm. We propose that this mechanism counters ectopic and precocious expression of functionally linked neuron-specific genes and ensures their coherent activation in the appropriate developmental context. PMID:22661231

Coordinated regulation of neuronal mRNA steady-state levels through developmentally controlled intron retention.

PubMed

Yap, Karen; Lim, Zhao Qin; Khandelia, Piyush; Friedman, Brad; Makeyev, Eugene V

2012-06-01

Differentiated cells acquire unique structural and functional traits through coordinated expression of lineage-specific genes. An extensive battery of genes encoding components of the synaptic transmission machinery and specialized cytoskeletal proteins is activated during neurogenesis, but the underlying regulation is not well understood. Here we show that genes encoding critical presynaptic proteins are transcribed at a detectable level in both neurons and nonneuronal cells. However, in nonneuronal cells, the splicing of 3'-terminal introns within these genes is repressed by the polypyrimidine tract-binding protein (Ptbp1). This inhibits the export of incompletely spliced mRNAs to the cytoplasm and triggers their nuclear degradation. Clearance of these intron-containing transcripts occurs independently of the nonsense-mediated decay (NMD) pathway but requires components of the nuclear RNA surveillance machinery, including the nuclear pore-associated protein Tpr and the exosome complex. When Ptbp1 expression decreases during neuronal differentiation, the regulated introns are spliced out, thus allowing the accumulation of translation-competent mRNAs in the cytoplasm. We propose that this mechanism counters ectopic and precocious expression of functionally linked neuron-specific genes and ensures their coherent activation in the appropriate developmental context.

Control of arousal by the orexin neurons.

PubMed

Alexandre, Chloe; Andermann, Mark L; Scammell, Thomas E

2013-10-01

The orexin-producing neurons in the lateral hypothalamus play an essential role in promoting arousal and maintaining wakefulness. These neurons receive a broad variety of signals related to environmental, physiological and emotional stimuli; they project to almost every brain region involved in the regulation of wakefulness; and they fire most strongly during active wakefulness, high motor activation, and sustained attention. This review focuses on the specific neuronal pathways through which the orexin neurons promote wakefulness and maintain high level of arousal, and how recent studies using optogenetic and pharmacogenetic methods have demonstrated that the locus coeruleus, the tuberomammillary nucleus, and the basal forebrain are some of the key sites mediating the arousing actions of orexins. Copyright © 2013 Elsevier Ltd. All rights reserved.