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1.
Acta Physiol (Oxf) ; 230(4): e13562, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32969183
2.
CNS Neurosci Ther ; 26(3): 355-366, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-31571389

RESUMO

AIMS: Histamine H3 receptor (H3R) antagonists/inverse agonists increase vigilance. We studied brain histaminergic pathways under hyperammonemia and the transcriptome of receptors and their signaling cascades to provide a rationale for wake-promoting therapies. METHODS: We analyzed histamine-induced long-lasting depression of corticostriatal synaptic transmission (LLDhist). As the expression of dopamine 1 receptors (D1R) is upregulated in LGS-KO striatum where D1R-H3R dimers may exist, we investigated actions of H3R and D1R agonists and antagonists. We analyzed transcription of selected genes in cortex and dorsal striatum in a mouse model of inborn hyperammonemia (liver-specific glutamine synthetase knockout: LGS-KO) and compared it with human hepatic encephalopathy. RESULTS: LGS-KO mice showed significant reduction of the direct depression (DD) but not the long-lasting depression (LLD) by histamine. Neither pharmacological activation nor inhibition of D1R significantly affected DDhist and LLDhist in WT striatum, while in LGS-KO mice D1R activation suppressed LLDhist. Histaminergic signaling was found unchanged at the transcriptional level except for the H2R. A study of cAMP-regulated genes indicated a significant reduction in the molecular signature of wakefulness in the diseased cortex. CONCLUSIONS: Our findings provide a rationale for the development of aminergic wake-promoting therapeutics in hyperammonemic disorders.

3.
Neuropharmacology ; 143: 327-338, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30219501

RESUMO

Histaminergic (HA) neurons located in the tuberomamillary nucleus (TMN) of the posterior hypothalamus fire exclusively during waking and support many physiological functions. We investigated the role of the endovanilloid N-oleoyldopamine (OLDA) in TMN, where dopamine synthesis and its conjugation with oleic acid likely occur. We show that several known targets of OLDA including TRPV1 and cannabinoid receptors are expressed in HA neurons. In contrast to capsaicin, which failed to increase firing of HA neurons in TRPV1 knockout mice (TRPVI KO), OLDA was still able to induce excitation. This excitation was not sensitive to the blockade of cannabinoid receptors 1 and 2 and could result from OLDA interaction with GPR119, as the ligand of GPR119, oleoylethanolamide (OEA), also increased the firing of HA neurons. However, we ruled out this possibility as OEA- (but not OLDA-) excitation was abolished by the PPAR (peroxisome proliferator activated receptor) alpha antagonist MK886. The dopamine uptake blocker nomifensine blanked OLDA-excitation and dopamine receptor antagonists abolished the OLDA action in TRPV1 KO mice. Therefore OLDA excites HA neurons through multiple targets suggesting a central role of the histaminergic system in the behavioral stimulation seen after systemic OLDA application.


Assuntos
Dopamina/análogos & derivados , Histamina/metabolismo , Região Hipotalâmica Lateral/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Neurotransmissores/farmacologia , Animais , Dopamina/farmacologia , Região Hipotalâmica Lateral/citologia , Região Hipotalâmica Lateral/crescimento & desenvolvimento , Região Hipotalâmica Lateral/metabolismo , Potenciais da Membrana/efeitos dos fármacos , Potenciais da Membrana/fisiologia , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Neurônios/citologia , Neurônios/metabolismo , Técnicas de Patch-Clamp , Canais de Cátion TRPV/genética , Canais de Cátion TRPV/metabolismo , Técnicas de Cultura de Tecidos
4.
Neuropharmacology ; 119: 111-122, 2017 06.
Artigo em Inglês | MEDLINE | ID: mdl-28400256

RESUMO

N-oleoyl-dopamine (OLDA) is an amide of dopamine and oleic acid, synthesized in catecholaminergic neurons. The present study investigates OLDA targets in midbrain dopaminergic (DA) neurons. Substantia Nigra compacta (SNc) DA neurons recorded in brain slices were excited by OLDA in wild type mice. In transient receptor potential vanilloid 1 (TRPV1) knockout (KO) mice, however, SNc DA neurons displayed sustained inhibition of firing. In the presence of the dopamine type 2 receptor (D2R) antagonist sulpiride or the dopamine transporter blocker nomifensine no such inhibition was observed. Under sulpiride OLDA slightly excited SNc DA neurons, an action abolished upon combined application of the cannabinoid1 and 2 receptor antagonists AM251 and AM630. In ventral tegmental area (VTA) DA neurons from TRPV1 KO mice a transient inhibition of firing by OLDA was observed. Thus OLDA modulates the firing of nigrostriatal DA neurons through interactions with TRPV1, cannabinoid receptors and dopamine uptake. These findings suggest further development of OLDA-like tandem molecules for the treatment of movement disorders including Parkinson's disease.


Assuntos
Dopaminérgicos/farmacologia , Dopamina/análogos & derivados , Neurônios Dopaminérgicos/efeitos dos fármacos , Mesencéfalo/citologia , Canais de Cátion TRPV/metabolismo , Acrilamidas/farmacologia , Potenciais de Ação/efeitos dos fármacos , Fatores Etários , Animais , Animais Recém-Nascidos , Compostos Bicíclicos Heterocíclicos com Pontes/farmacologia , Antagonistas de Receptores de Canabinoides/farmacologia , Dopamina/farmacologia , Proteínas da Membrana Plasmática de Transporte de Dopamina/genética , Proteínas da Membrana Plasmática de Transporte de Dopamina/metabolismo , Proteínas Luminescentes/genética , Proteínas Luminescentes/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Inibição Neural/efeitos dos fármacos , Técnicas de Patch-Clamp , Piperidinas/farmacologia , Pirazóis/farmacologia , Canais de Cátion TRPV/antagonistas & inibidores , Canais de Cátion TRPV/genética , Tirosina 3-Mono-Oxigenase/metabolismo
5.
Sci Rep ; 7: 40190, 2017 01 09.
Artigo em Inglês | MEDLINE | ID: mdl-28067279

RESUMO

Genetic defects in ammonia metabolism can produce irreversible damage of the developing CNS causing an impairment of cognitive and motor functions. We investigated alterations in behavior, synaptic plasticity and gene expression in the hippocampus and dorsal striatum of transgenic mice with systemic hyperammonemia resulting from conditional knockout of hepatic glutamine synthetase (LGS-ko). These mice showed reduced exploratory activity and delayed habituation to a novel environment. Field potential recordings from LGS-ko brain slices revealed significantly reduced magnitude of electrically-induced long-term potentiation (LTP) in both CA3-CA1 hippocampal and corticostriatal synaptic transmission. Corticostriatal but not hippocampal slices from LGS-ko brains demonstrated also significant alterations in long-lasting effects evoked by pharmacological activation of glutamate receptors. Real-time RT-PCR revealed distinct patterns of dysregulated gene expression in the hippocampus and striatum of LGS-ko mice: LGS-ko hippocampus showed significantly modified expression of mRNAs for mGluR1, GluN2B subunit of NMDAR, and A1 adenosine receptors while altered expression of mRNAs for D1 dopamine receptors, the M1 cholinoreceptor and the acetylcholine-synthetizing enzyme choline-acetyltransferase was observed in LGS-ko striatum. Thus, inborn systemic hyperammonemia resulted in significant deficits in novelty acquisition and disturbed synaptic plasticity in corticostriatal and hippocampal pathways involved in learning and goal-directed behavior.


Assuntos
Encéfalo/fisiopatologia , Comportamento Exploratório , Glutamato-Amônia Ligase/deficiência , Hiperamonemia/genética , Hiperamonemia/psicologia , Plasticidade Neuronal , Animais , Encéfalo/metabolismo , Córtex Cerebral/fisiopatologia , Corpo Estriado/metabolismo , Corpo Estriado/fisiopatologia , Glutamato-Amônia Ligase/genética , Habituação Psicofisiológica , Hipocampo/metabolismo , Hipocampo/fisiopatologia , Hiperamonemia/congênito , Fígado/metabolismo , Masculino , Camundongos Knockout , Receptores de Dopamina D2/fisiologia , Receptores de N-Metil-D-Aspartato/fisiologia , Transmissão Sináptica
6.
Brain ; 139(Pt 2): 509-25, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26657517

RESUMO

Despite amyloid plaques, consisting of insoluble, aggregated amyloid-ß peptides, being a defining feature of Alzheimer's disease, their significance has been challenged due to controversial findings regarding the correlation of cognitive impairment in Alzheimer's disease with plaque load. The amyloid cascade hypothesis defines soluble amyloid-ß oligomers, consisting of multiple amyloid-ß monomers, as precursors of insoluble amyloid-ß plaques. Dissecting the biological effects of single amyloid-ß oligomers, for example of amyloid-ß dimers, an abundant amyloid-ß oligomer associated with clinical progression of Alzheimer's disease, has been difficult due to the inability to control the kinetics of amyloid-ß multimerization. For investigating the biological effects of amyloid-ß dimers, we stabilized amyloid-ß dimers by an intermolecular disulphide bridge via a cysteine mutation in the amyloid-ß peptide (Aß-S8C) of the amyloid precursor protein. This construct was expressed as a recombinant protein in cells and in a novel transgenic mouse, termed tgDimer mouse. This mouse formed constant levels of highly synaptotoxic soluble amyloid-ß dimers, but not monomers, amyloid-ß plaques or insoluble amyloid-ß during its lifespan. Accordingly, neither signs of neuroinflammation, tau hyperphosphorylation or cell death were observed. Nevertheless, these tgDimer mice did exhibit deficits in hippocampal long-term potentiation and age-related impairments in learning and memory, similar to what was observed in classical Alzheimer's disease mouse models. Although the amyloid-ß dimers were unable to initiate the formation of insoluble amyloid-ß aggregates in tgDimer mice, after crossbreeding tgDimer mice with the CRND8 mouse, an amyloid-ß plaque generating mouse model, Aß-S8C dimers were sequestered into amyloid-ß plaques, suggesting that amyloid-ß plaques incorporate neurotoxic amyloid-ß dimers that by themselves are unable to self-assemble. Our results suggest that within the fine interplay between different amyloid-ß species, amyloid-ß dimer neurotoxic signalling, in the absence of amyloid-ß plaque pathology, may be involved in causing early deficits in synaptic plasticity, learning and memory that accompany Alzheimer's disease.


Assuntos
Peptídeos beta-Amiloides/metabolismo , Transtornos Cognitivos/metabolismo , Plasticidade Neuronal/fisiologia , Placa Amiloide/metabolismo , Multimerização Proteica/fisiologia , Peptídeos beta-Amiloides/genética , Animais , Transtornos Cognitivos/genética , Transtornos Cognitivos/patologia , Hipocampo/metabolismo , Hipocampo/patologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Técnicas de Cultura de Órgãos , Placa Amiloide/genética , Placa Amiloide/patologia
7.
Neuropharmacology ; 106: 102-15, 2016 07.
Artigo em Inglês | MEDLINE | ID: mdl-26297536

RESUMO

Using a reporter mouse model with expression of the tomato fluorescent protein under the dopamine transporter promoter (Tmt-DAT) we discovered a new group of neurons in the histaminergic tuberomamillary nucleus (TMN), which, in contrast to tuberoinfundibular dopaminergic neurons of the dorsomedial arcuate nucleus, do not express tyrosine hydroxylase but can synthesize and store dopamine. Tmt-DAT neurons located within TMN share electrophysiological properties with histaminergic neurons: spontaneous firing at a membrane potential around -50 mV and presence of hyperpolarization-activated cyclic nucleotide-gated ion channels. Histamine (30 µM) depolarizes and excites Tmt-DAT neurons through H1R activation but inhibits histaminergic neurons through H3R activation thus allowing a pharmacological identification of the different neurons. Single-cell RT-PCR revealed that all histaminergic neurons expressing histidine decarboxylase (HDC) also express H3R. This includes neurons retrogradely traced from the striatum whose inhibition by a selective H3R agonist was indistinguishable from the whole population. Prolonged depolarization reduces the autoinhibition. The potency of histamine at H3R depends on membrane potential and on extracellular and intracellular calcium. Autoinhibition can be impaired by preincubation with capsaicin, a ligand of the calcium-permeable TRPV1 channel or by blockade of Ca(2+)-ATPase with thapsigargin. The pharmacology of autoinhibition is revisited and physiological conditions for its functionality are determined. Usage of reporter mouse models for the safe identification of aminergic neurons under pathophysiological conditions is recommended. This article is part of the Special Issue entitled 'Histamine Receptors'.


Assuntos
Histamina/metabolismo , Região Hipotalâmica Lateral/citologia , Região Hipotalâmica Lateral/metabolismo , Neurônios/citologia , Neurônios/metabolismo , Receptores Histamínicos H3/metabolismo , Animais , Cálcio/metabolismo , ATPases Transportadoras de Cálcio/metabolismo , Proteínas da Membrana Plasmática de Transporte de Dopamina/genética , Proteínas da Membrana Plasmática de Transporte de Dopamina/metabolismo , Feminino , Histidina Descarboxilase/metabolismo , Região Hipotalâmica Lateral/efeitos dos fármacos , Masculino , Potenciais da Membrana/efeitos dos fármacos , Potenciais da Membrana/fisiologia , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Inibição Neural/efeitos dos fármacos , Inibição Neural/fisiologia , Neurônios/efeitos dos fármacos , Receptores Histamínicos H1/metabolismo , Canais de Cátion TRPV/metabolismo , Técnicas de Cultura de Tecidos
8.
Neural Plast ; 2015: 458123, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25821602

RESUMO

Age-related alterations in the expression of genes and corticostriatal synaptic plasticity were studied in the dorsal striatum of mice of four age groups from young (2-3 months old) to old (18-24 months of age) animals. A significant decrease in transcripts encoding neuronal nitric oxide (NO) synthase and receptors involved in its activation (NR1 subunit of the glutamate NMDA receptor and D1 dopamine receptor) was found in the striatum of old mice using gene array and real-time RT-PCR analysis. The old striatum showed also a significantly higher number of GFAP-expressing astrocytes and an increased expression of astroglial, inflammatory, and oxidative stress markers. Field potential recordings from striatal slices revealed age-related alterations in the magnitude and dynamics of electrically induced long-term depression (LTD) and significant enhancement of electrically induced long-term potentiation in the middle-aged striatum (6-7 and 12-13 months of age). Corticostriatal NO-dependent LTD induced by pharmacological activation of group I metabotropic glutamate receptors underwent significant reduction with aging and could be restored by inhibition of cGMP hydrolysis indicating that its age-related deficit is caused by an altered NO-cGMP signaling cascade. It is suggested that age-related alterations in corticostriatal synaptic plasticity may result from functional alterations in receptor-activated signaling cascades associated with increasing neuroinflammation and a prooxidant state.


Assuntos
Envelhecimento/genética , Expressão Gênica , Neostriado/fisiologia , Plasticidade Neuronal/genética , Óxido Nítrico/metabolismo , Transdução de Sinais/genética , Animais , Astrócitos/metabolismo , Proteína Glial Fibrilar Ácida , Proteínas de Fluorescência Verde , Masculino , Camundongos , Camundongos Transgênicos , Neostriado/enzimologia , Neostriado/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Óxido Nítrico Sintase/genética , Estresse Oxidativo/genética , Receptores de Dopamina D1/genética , Receptores de N-Metil-D-Aspartato/genética
9.
Cell Mol Neurobiol ; 34(6): 777-89, 2014 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-24798513

RESUMO

Breathing and vigilance are regulated by pH and CO2 levels in the central nervous system. The hypocretin/orexin (Hcrt/Orx)- and histamine (HA)-containing hypothalamic neurons synergistically control different aspects of the waking state. Acidification inhibits firing of most neurons but these two groups in the caudal hypothalamus are excited by hypercapnia and protons, similar to the chemosensory neurons in the brain stem. Activation of hypothalamic wake-on neurons in response to hypercapnia, seen with the c-Fos assay, is supported by patch-clamp recordings in rodent brain slices: Hcrt/Orx and HA neurons are excited by acidification in the physiological range (pH from 7.4 to 7.0). Multiple molecular mechanisms mediate wake-promoting effects of protons in HA neurons in the tuberomamillary nucleus (TMN): among them are acid-sensing ion channels, Na(+),K(+)-ATPase, group I metabotropic glutamate receptors (mGluRI). HA neurons are remarkably sensitive to the mGluRI agonist DHPG (threshold concentration 0.5 µM) and mGluRI antagonists abolish proton-induced excitation of HA neurons. Hcrt/Orx neurons are excited through block of a potassium conductance and release glutamate with their peptides in TMN. The two hypothalamic nuclei and the serotonergic dorsal raphe cooperate toward CO2/acid-induced arousal. Their interactions and molecular mechanisms of H(+)/CO2-induced activation are relevant for the understanding and treatment of respiratory and metabolic disorders related to sleep-waking such as obstructive sleep apnea and sudden infant death syndrome.


Assuntos
Canais Iônicos Sensíveis a Ácido/metabolismo , Potenciais de Ação/fisiologia , Hipotálamo/metabolismo , Neurônios/metabolismo , Animais , Ácido Glutâmico/metabolismo , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Neuropeptídeos/metabolismo , Orexinas
10.
PLoS One ; 8(4): e61733, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23637894

RESUMO

Taurine is a semi-essential sulfonic acid found at high concentrations in plasma and mammalian tissues which regulates osmolarity, ion channel activity and glucose homeostasis. The structural requirements of GABAA-receptors (GABAAR) gated by taurine are not yet known. We determined taurine potency and efficacy relative to GABA at different types of recombinant GABAAR occurring in central histaminergic neurons of the mouse hypothalamic tuberomamillary nucleus (TMN) which controls arousal. At binary α(1/2)ß(1/3) receptors taurine was as efficient as GABA, whereas incorporation of the γ(1/2) subunit reduced taurine efficacy to 60-90% of GABA. The mutation γ(2F77I), which abolishes zolpidem potentiation, significantly reduced taurine efficacy at recombinant and native receptors compared to the wild type controls. As taurine was a full- or super- agonist at recombinant αxß1δ-GABAAR, we generated a chimeric γ(2) subunit carrying the δ subunit motif around F77 (MTVFLH). At α(1/2)ß(1)γ2(MTVFLH) receptors taurine became a super-agonist, similar to δ-containing ternary receptors, but remained a partial agonist at ß3-containing receptors. In conclusion, using site-directed mutagenesis we found structural determinants of taurine's partial agonism at γ-containing GABAA receptors. Our study sheds new light on the ß1 subunit conferring the widest range of taurine-efficacies modifying GABAAR function under (patho)physiological conditions.


Assuntos
Agonistas de Receptores de GABA-A/farmacologia , Receptores de GABA-A/genética , Receptores de GABA-A/metabolismo , Taurina/farmacologia , Sequência de Aminoácidos , Animais , Agonistas de Receptores de GABA-A/metabolismo , Hipotálamo/citologia , Masculino , Camundongos , Dados de Sequência Molecular , Mutagênese Sítio-Dirigida , Mutação , Neurônios/citologia , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Subunidades Proteicas/química , Subunidades Proteicas/metabolismo , Piridinas/farmacologia , Receptores de GABA-A/química , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Alinhamento de Sequência , Taurina/metabolismo , Xenopus , Zolpidem , Ácido gama-Aminobutírico/metabolismo
11.
Eur J Pharmacol ; 710(1-3): 59-66, 2013 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-23603522

RESUMO

Histamine is involved in many physiological functions in the periphery and is an important neurotransmitter in the brain. It acts on metabotropic H1-H4 receptors mediating vasodilatation, bronchoconstriction and stimulation of gastric acid secretion. In the brain histamine is produced by neurons in the tuberomamillary nucleus (TMN), which controls arousal. Histamine is also a positive modulator of the inhibitory Cys-loop ligand-gated ion channel GABAA. We investigated now its effect on the second member of inhibitory Cys-loop ligand-gated ion channels, the strychnine sensitive glycine receptor. We expressed different human and rat glycine receptor subunits in Xenopus laevis oocytes and characterized the effect of histamine using the two electrode voltage clamp technique. Furthermore we investigated native glycine receptors in hypothalamic neurons using the patch-clamp technique. Histamine inhibited α1ß glycine receptors with an IC50 of 5.2±0.3 mM. In presence of 10 mM histamine the glycine dose-response curve was shifted, increasing the EC50 for glycine from 25.5±1.4 µM to 42.4±2.3 µM. In addition, histamine blocked the spontaneous activity of RNA-edited α3ß glycine receptors. Histamine inhibited glycine receptors expressed in hypothalamic TMN neurons with an IC50 of 4.6±0.3 mM. Our results give strong evidence that histamine is acting on the same binding site as glycine, being an inverse agonist that competitively antagonizes glycine receptors. Thus, we revealed histamine as an endogenous modulator of glycine receptors.


Assuntos
Histamina/farmacologia , Subunidades Proteicas/metabolismo , Receptores da Glicina/metabolismo , Animais , DNA Complementar/genética , Humanos , Hipotálamo/citologia , Masculino , Camundongos Endogâmicos C57BL , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Oócitos/efeitos dos fármacos , Oócitos/metabolismo , Subunidades Proteicas/antagonistas & inibidores , Subunidades Proteicas/genética , Ratos , Receptores da Glicina/antagonistas & inibidores , Receptores da Glicina/genética , Proteínas Recombinantes/metabolismo , Xenopus laevis/genética
12.
Arch Biochem Biophys ; 536(2): 122-30, 2013 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-23624382

RESUMO

Hepatic encephalopathy (HE)(1) is a neuropsychiatric disorder caused by chronic or acute liver failure. Nearly thirty years ago a hypothesis was formulated explaining the neuropathology of HE by increased GABAergic tone. Recent progress in the GABAA-receptor (GABAAR) molecular pharmacology and biochemistry as well as the physiology of GABAergic transmission provided better understanding of GABA's role in health and disease. A detailed analysis of neuronal populations and their GABAergic afferents affected in HE is still missing. The slow progress in understanding the pathology of GABAergic transmission in HE is due to the high complexity of brain circuitries controlled by multiple types of GABAergic interneurons and the large variety of GABAAR, which are differently affected by pathological conditions and not yet fully identified. The mechanisms of action of the GABAAR agonist taurine, allosteric positive modulators (inhibitory neurosteroids, anaesthetics, benzodiazepines and histamine) and inhibitors of the GABAAR (excitatory neurosteroids, Ro15-4513) are discussed with respect to HE pathophysiology. Perspectives for GABAergic drugs in the symptomatic treatment of HE are suggested.


Assuntos
Encéfalo/fisiopatologia , Encefalopatia Hepática/metabolismo , Encefalopatia Hepática/fisiopatologia , Receptores de GABA/metabolismo , Ácido gama-Aminobutírico/metabolismo , Animais , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Antagonistas GABAérgicos/uso terapêutico , Encefalopatia Hepática/tratamento farmacológico , Encefalopatia Hepática/genética , Humanos , Fígado/efeitos dos fármacos , Fígado/metabolismo , Fígado/fisiopatologia , Receptores de GABA/química , Receptores de GABA/genética
13.
Mol Cell Neurosci ; 56: 10-7, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23403072

RESUMO

Besides mediating most of the fast excitatory neurotransmission in the mammalian CNS, ionotropic glutamate receptors of the AMPA subtype (AMPARs) serve highly diverse functions in brain development controlling neuronal migration, synaptic growth, and synaptic maturation. Pioneering proteomic studies suggest that this functional diversity is met by a great molecular complexity in native AMPAR composition. Here, we have investigated the expression patterns of two recently identified AMPAR constituents, the cornichon homologues CNIH-2 and CNIH-3, and their assembly with the AMPAR core subunits GluA1-4 in developing rat brain. Unlike GluA1-4 expression, which is up-regulated during postnatal brain development, the two cornichon homologues show maximum mRNA and protein expression early after birth, which then decline towards adulthood. Despite rather reciprocal expression profiles, the overall ratio of CNIH-2/3 complexed with GluAs remains constant throughout development. Our data reveal an excess amount of AMPAR-free CNIH-2/3 early in development, which might serve the evolutionarily conserved role of cornichon as a cargo exporter. With progressing development, however, the amount of AMPAR-free CNIH-2/3 subsides, whereas the one being integrated into AMPAR complexes increases. Hence, the cornichon homologues CNIH-2/3 gain importance in their role as auxiliary subunits of native AMPARs during ontogeny, which reflects their functional evolution in phylogeny.


Assuntos
Receptores de AMPA/metabolismo , Animais , Encéfalo/crescimento & desenvolvimento , Encéfalo/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Filogenia , Ligação Proteica , Multimerização Proteica , Subunidades Proteicas/genética , Subunidades Proteicas/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ratos , Ratos Wistar , Receptores de AMPA/genética
14.
Arch Biochem Biophys ; 536(2): 176-82, 2013 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-23416740

RESUMO

Hyperammonemia is a major pathophysiological factor in encephalopathies associated with acute and chronic liver failure. On mouse brain slice preparations we analyzed the effects of ammonium on the characteristics of corticostriatal long-term potentiation (LTP) induced by high-frequency electrical stimulation (HFS) of cortical input and the long-lasting effects of pharmacological NMDA receptor (NMDAR) activation. Ammonium chloride exposure enhanced the expression of HFS-induced LTP at the expense of LTD and promoted the generation of NMDA-induced LTD. This treatment did not affect two NMDAR-independent forms of plasticity: taurine-induced LTP and histamine-induced LTD. Alterations in NMDA-induced plasticity were prevented by treatment with green tea polyphenols suggesting the contribution of oxidative stress to the expression of abnormal corticostriatal plasticity.


Assuntos
Antioxidantes/farmacologia , Corpo Estriado/efeitos dos fármacos , Corpo Estriado/fisiologia , Depressão Sináptica de Longo Prazo/efeitos dos fármacos , Polifenóis/farmacologia , Compostos de Amônio Quaternário/metabolismo , Chá , Animais , Antioxidantes/química , Catequina/química , Catequina/farmacologia , Estimulação Elétrica , Histamina/metabolismo , Hiperamonemia/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Polifenóis/química , Receptores de N-Metil-D-Aspartato/metabolismo , Taurina/metabolismo , Chá/química
15.
PLoS One ; 8(10)2013.
Artigo em Inglês | MEDLINE | ID: mdl-29364971

RESUMO

[This corrects the article DOI: 10.1371/journal.pone.0061733.].

17.
PLoS One ; 7(8): e42512, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22880010

RESUMO

Since ancient times ursodeoxycholic acid (UDCA), a constituent of bile, is used against gallstone formation and cholestasis. A neuroprotective action of UDCA was demonstrated recently in models of Alzheimer's disease and retinal degeneration. The mechanisms of UDCA action in the nervous system are poorly understood. We show now that UDCA promotes wakefulness during the active period of the day, lacking this activity in histamine-deficient mice. In cultured hypothalamic neurons UDCA did not affect firing rate but synchronized the firing, an effect abolished by the GABA(A)R antagonist gabazine. In histaminergic neurons recorded in slices UDCA reduced amplitude and duration of spontaneous and evoked IPSCs. In acutely isolated histaminergic neurons UDCA inhibited GABA-evoked currents and sIPSCs starting at 10 µM (IC(50) = 70 µM) and did not affect NMDA- and AMPA-receptor mediated currents at 100 µM. Recombinant GABA(A) receptors composed of α1, ß1-3 and γ2L subunits expressed in HEK293 cells displayed a sensitivity to UDCA similar to that of native GABA(A) receptors. The mutation α1V256S, known to reduce the inhibitory action of pregnenolone sulphate, reduced the potency of UDCA. The mutation α1Q241L, which abolishes GABA(A)R potentiation by several neurosteroids, had no effect on GABA(A)R inhibition by UDCA. In conclusion, UDCA enhances alertness through disinhibition, at least partially of the histaminergic system via GABA(A) receptors.


Assuntos
Antagonistas de Receptores de GABA-A/farmacologia , Histamina/metabolismo , Receptores de GABA-A/metabolismo , Ácido Ursodesoxicólico/farmacologia , Vigília/efeitos dos fármacos , Potenciais de Ação/efeitos dos fármacos , Administração Oral , Animais , Histamina/deficiência , Região Hipotalâmica Lateral/citologia , Região Hipotalâmica Lateral/efeitos dos fármacos , Região Hipotalâmica Lateral/fisiologia , Potenciais Pós-Sinápticos Inibidores/efeitos dos fármacos , Cinética , Camundongos , Proteínas Mutantes/metabolismo , Mutação/genética , Neurônios/efeitos dos fármacos , Neurônios/fisiologia , Picrotoxina/farmacologia , Receptores de GABA-A/genética , Proteínas Recombinantes/antagonistas & inibidores , Proteínas Recombinantes/metabolismo , Esteroides/farmacologia , Fatores de Tempo , Ácido Ursodesoxicólico/administração & dosagem
18.
J Neurochem ; 122(3): 545-56, 2012 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22639911

RESUMO

Hyperammonemia is a major pathophysiological factor in encephalopathies associated with acute and chronic liver failure. On mouse brain slice preparations, we analyzed the effects of ammonia on the characteristics of corticostriatal long-term depression (LTD) induced by electrical stimulation of cortical input or pharmacological activation of metabotropic glutamate receptors. Long exposure of neostriatal slices to ammonium chloride impaired the induction and/or expression of all studied forms of LTD. This impairment was reversed by the phosphodiesterase inhibitor zaprinast implying lowered cGMP signaling in LTD suppression. Polyphenols from green tea rescued short-term corticostriatal plasticity, but failed to prevent the ammonia-induced deficit of LTD. Zaprinast counteracts the ammonia-induced impairment of long-term corticostriatal plasticity and may thus improve fine motor skills and procedural learning in hepatic encephalopathy.


Assuntos
Amônia/farmacologia , Córtex Cerebral/citologia , Corpo Estriado/citologia , Depressão Sináptica de Longo Prazo/efeitos dos fármacos , Inibidores de Fosfodiesterase/farmacologia , Purinonas/farmacologia , Sinapses/efeitos dos fármacos , Animais , Antioxidantes/farmacologia , Biofísica , Córtex Cerebral/efeitos dos fármacos , Córtex Cerebral/fisiologia , Corpo Estriado/efeitos dos fármacos , Corpo Estriado/fisiologia , Cicloeximida/farmacologia , Interações Medicamentosas , Estimulação Elétrica , Técnicas In Vitro , Masculino , Metoxi-Hidroxifenilglicol/análogos & derivados , Metoxi-Hidroxifenilglicol/farmacologia , Camundongos , Camundongos Endogâmicos C57BL , Polifenóis/farmacologia , Inibidores da Síntese de Proteínas/farmacologia
19.
Front Syst Neurosci ; 6: 23, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22509157

RESUMO

The histaminergic neurons in the tuberomamillary nucleus (TMN) of the posterior hypothalamus are involved in the control of arousal. These neurons are sensitive to hypercapnia as has been shown in experiments examining c-Fos expression, a marker for increased neuronal activity. We investigated the mechanisms through which TMN neurons respond to changes in extracellular levels of acid/CO(2). Recordings in rat brain slices revealed that acidification within the physiological range (pH from 7.4 to 7.0), as well as ammonium chloride (5 mM), excite histaminergic neurons. This excitation is significantly reduced by antagonists of type I metabotropic glutamate receptors and abolished by benzamil, an antagonist of acid-sensing ion channels (ASICs) and Na(+)/Ca(2+) exchanger, or by ouabain which blocks Na(+)/K(+) ATPase. We detected variable combinations of 4 known types of ASICs in single TMN neurons, and observed activation of ASICs in single dissociated TMN neurons only at pH lower than 7.0. Thus, glutamate, which is known to be released by glial cells and orexinergic neurons, amplifies the acid/CO(2)-induced activation of TMN neurons. This amplification demands the coordinated function of metabotropic glutamate receptors, Na(+)/Ca(2+) exchanger and Na(+)/K(+) ATPase. We also developed a novel HDC-Cre transgenic reporter mouse line in which histaminergic TMN neurons can be visualized. In contrast to the rat, the mouse histaminergic neurons lacked the pH 7.0-induced excitation and displayed only a minimal response to the mGluR I agonist DHPG (0.5 µM). On the other hand, ammonium-induced excitation was similar in mouse and rat. These results are relevant for the understanding of the neuronal mechanisms controlling acid/CO(2)-induced arousal in hepatic encephalopathy and obstructive sleep apnoea. Moreover, the new HDC-Cre mouse model will be a useful tool for studying the physiological and pathophysiological roles of the histaminergic system.

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