Mécanismes cellulaires de l'induction du facteur de transcription Nur77 après un traitement aux antipsychotiques

Les antipsychotiques sont utilisés en clinique depuis plus de 50 ans pour pallier aux symptômes de la schizophrénie. Malgré une recherche intensive, les mécanismes cellulaires et moléculaires responsables de l’effet clinique de cette médication demeurent encore nébuleux. Ces drogues sont reconnues comme des antagonistes des récepteurs D2 de la dopamine et peuvent moduler la transcription génique dans le striatum. Au cours des recherches qui ont mené à l'écriture de cette thèse, nous avons exploré l’expression de Nur77, un facteur de transcription de la famille des récepteurs nucléaires, afin de caractériser le rôle de la dopamine, la sérotonine, l’adénosine et le glutamate dans la régulation génique contrôlée par les antagonistes D2. En premier lieu, nous avons examiné l’impact de la co-administration d’agents sérotonergiques et adrénergiques sur l’expression de l’ARNm de Nur77 induite par l’halopéridol, un antipsychotique de première génération. Nous avons observé que le 8-OH-DPAT et le MDL11939 préviennent partiellement l’induction de Nur77 dans le striatum. Au contraire, l’idazoxan potentialise l’effet de l’halopéridol sur l’expression de Nur77 alors que le prazosin reste sans effet. Ces résultats démontrent que l’expression striatale de Nur77 induite par l’halopéridol peut être modulée à la baisse avec un agoniste 5-HT1A ou un antagoniste 5-HT2A. Par la suite, nous avons évalué dans divers paradigmes expérimentaux l’effet de l’éticlopride, un antagoniste spécifique D2, afin d’explorer davantage le mécanisme de l’effet transcriptionnel des antagonistes D2. Étonnamment, la suppression de l’isoforme D2L chez la souris D2L KO ne réduit pas la réponse de l’éticlopride dans le striatum. Par contre, une lésion corticale avec l’acide iboténique bloque l’effet de l’éticlopride sur la transcription de Nur77, suggérant un rôle du glutamate. La combinaison d’un antagoniste des récepteurs métabotropes du glutamate de types 5 (mGluR5) et d’un antagoniste des récepteurs de l’adénosine A2A abolit complètement l’augmentation de la transcription de Nur77 induit par l’éticlopride dans le striatum. La modulation directe de l’expression striatale de Nur77 par les récepteurs mGluR5 et A2A a été confirmée dans un modèle de cultures organotypiques de tranches cérébrales. Ces résultats démontrent clairement que la modulation de l’expression génique dans le striatum, à la suite d’un traitement avec un antagoniste D2 pourrait être indépendante d’une interaction directe avec les récepteurs D2 post-synaptiques, et reposerait plutôt sur son interaction avec les récepteurs D2 hétérosynaptiques des afférences corticostriées et l’activation subséquente des récepteurs post-synaptiques du glutamate et de l’adénosine. En résumé, nos résultats suggèrent que l’interaction des antipsychotiques atypiques avec les récepteurs 5-HT2A et 5-HT1A pourrait expliquer la différence dans le patron d’expression génique induit par ces drogues en comparaison avec les antipsychotiques typiques. De plus, nos résultats révèlent un nouveau mécanisme d’action des antagonistes D2 et supportent un rôle primordial du glutamate et de l’adénosine dans les effets des antipsychotiques de première génération.

Reconnection at the high-latitude magnetopause during northward interplanetary magnetic field conditions

The Polar spacecraft had a prolonged encounter with the high-latitude dayside magnetopause on May 29, 1996. This encounter with the magnetopause occurred when the interplanetary magnetic field was directed northward. From the three-dimensional electron and ion distribution functions measured by the Hydra instrument, it has been possible to identify nearly all of the distinct boundary layer regions associated with high-latitude reconnection. The regions that have been identified are (1) the cusp; (2) the magnetopause current layer; (3) magnetosheath field lines that have interconnected in only the Northern Hemisphere; (4) magnetosheath field lines that have interconnected in only the Southern Hemisphere; (5) magnetosheath field lines that have interconnected in both the Northern and Southern Hemispheres; (6) magnetosheath that is disconnected from the terrestrial magnetic field; and (7) high-latitude plasma sheet field lines that are participating in magnetosheath reconnection. Reconnection over this time period was occurring at high latitudes over a broad local-time extent, interconnecting the magnetosheath and lobe and/or plasma sheet field lines in both the Northern and Southern Hemispheres. Newly closed boundary layer field lines were observed as reconnection occur-red first at high latitudes in one hemisphere and then later in the other. These observations establish the location of magnetopause reconnection during these northward interplanetary magnetic field conditions as being at high latitudes, poleward of the cusp, and further reinforce the general interpretation of electron and ion phase space density signatures as indicators of magnetic reconnection and boundary layer formation.

S100 beta Protein Expression: Gender- and Age-Related Daily Changes

S100 beta is a soluble protein released by glial cells mainly under the activation of the 5-HT1A receptor. It has been reported as a neuro-trophic and -tropic factor that promotes neurite maturation and outgrowth during development. This protein also plays a role in axonal stability and the plasticity underlying long-term potentiation in adult brains. The ability of S100 beta to rapidly regulate neuronal morphology raises the interesting point of whether there are daily rhythm or gender differences in S100 beta level in the brain. To answer this question, the S100 beta expression in adult female and male rats, as well as in adult female CD-21 and S100 beta -/- female mice, were investigated. Scintillation counting and morphometric analysis of the immunoreactivity of S100 beta, showed rhythmic daily expression. The female and male rats showed opposite cycles. Females presented the highest value at the beginning of the rest phase (5:00 h), while in males the maximum value appeared in the beginning of the motor activity period (21:00 h). These results confirm previous S100 beta evaluations in human serum and cerebrospinal fluid reporting the protein`s function as a biomarker for brain damage (Gazzolo et al. in Clin Chem 49:967-970, 2003; Clin Chim Acta 330:131-133, 2003; Pediatr Res 58:1170-1174, 2005), similar behavior was also observed for GFAP in relation to Alzheimer Disease (Fukuyama et al. in Eur Neurol 46:35-38, 2001). The data should be taken into account when considering S100 beta as a biomarker of health condition. In addition, the results raise questions on which structure or condition imposes these rhythms as well as on the physiological meaning of the observed gender differences.

Serotoninergic receptors in the anteroventral preoptic region modulate the hypoxic ventilatory response

Hypothalamus is a site of integration of the hypoxic and thermal stimuli on breathing and there is evidence that serotonin (5-HT) receptors in the anteroventral preoptic region (AVPO) mediate hypoxic hypothermia. Once 5-HT is involved in the hypoxic ventilatory response (HVR), we investigated the participation of the 5-HT receptors (5-HT1, 5-HT2 and 5-HT7) in the AVPO in the HVR. To this end, pulmonary ventilation (V-E) of rats was measured before and after intra-AVPO microinjection of methysergide (a 5-HT1 and 5-HT2 receptor antagonist), WAY-100635 (a 5-HT1A receptor antagonist) and SB-269970 (a 5-HT7 receptor antagonist), followed by 60 min of hypoxia exposure (7% O-2). Intra-AVPO microinjection of vehicles or 5-HT antagonists did not change VE during normoxic conditions. Exposure of rats to 7% O-2 evoked typical hypoxia-induced hyperpnea after vehicle microinjection, which was not affected by methysergide. WAY-100635 and SB-269970 treatment caused an increased HVR, due to a higher tidal volume. Therefore, the current data provide the evidence that 5-HT acting on 5-HT1A and 5-HT7 receptors in the AVPO exert an inhibitory modulation on the HVR. (c) 2005 Elsevier B.V. All rights reserved.

Efeito de pontas de pulverização na deposição e na dessecação em plantas de Brachiaria brizantha

Objetivou-se com este trabalho avaliar a eficiência de pontas de pulverização com diferentes vazões e tamanhos de gotas na deposição e na dessecação de plantas de Brachiaria brizantha cv. Marandu, além da quantificação das perdas da calda de pulverização para o solo. O delineamento experimental adotado foi o de blocos casualizados, com quatro repetições. Cada unidade experimental constituiu-se de três linhas de 5 m de comprimento, espaçadas de 1 m. A aplicação dos tratamentos foi realizada 16 meses após a semeadura da braquiária; 40 dias antes da aplicação foi realizada uma roçagem para uniformização da área. Foram avaliadas as pontas de pulverização de jato plano XR 11001 VS (100 L ha-1) e XR 11002 VS (200 L ha-1), jato cônico TX-4VS (100 L ha-1) e TX-8 VK (200 L ha-1), ponta com indução de ar AI 11002 VS (200 L ha-1) e jato plano duplo TJ60 11002 VS (200 L ha-1). A calda foi aplicada com o herbicida glyphosate na dose de 1.800 g ha-1, mais um traçador (FD&C nº1 2.000 ppm). Foram coletados imediatamente após a aplicação da calda 25 perfilhos por repetição, sendo lavadas separadamente as folhas e caules de cada perfilho em 150 ml de água destilada, para posterior quantificação do traçador em espectrofotômetro. Os dados foram ajustados à curva de regressão pelo modelo de Gompertz. Todas as pontas utilizadas foram eficientes na dessecação das plantas de B. brizantha, independentemente do volume utilizado, o que evidencia a possibilidade de redução do volume de aplicação e da dosagem do herbicida na dessecação de pastagens, considerando-se a utilização de herbicidas sistêmicos. Ressalta-se que houve diferença na quantidade e na uniformidade de distribuição da calda pulverizada nos alvos avaliados em função da ponta testada e, conseqüentemente, do volume utilizado.

Anxiolytic-like effect of way-100635 microinfusions into the median (but not dorsal) raphe nucleus in mice exposed to the plus-maze: influence of prior test experience

Studies in several laboratories have confirmed the anxiolytic potential of a wide range of 5-HT1A receptor antagonists in rats and mice, with recent evidence pointing to a postsynaptic site of action in the ventral hippocampus. It would, therefore, be predicted that blockade of 5-HT1A somatodendritic autoreceptors in the midbrain raphe nuclei should produce anxiogenic-like effects. To test this hypothesis, we investigated the effects of WAY-100635 microinfusions (0, 1.0 or 3.0 mug in 0.1 mul) into the dorsal (DRN) or median (MRN) raphe nuclei on behaviours displayed by male Swiss-Webster mice in the elevated plus-maze. As this test is sensitive to prior experience. The effects of intra-raphe infusions were examined both in maze-naive and maze-experienced subjects. Sessions, were videotaped and subsequently scored for conventional indices of anxiety (open arm avoidance) and locomotor activity (closed arm entries), as well as a range of ethological measures (e.g. risk assessment). In maze-naive mice, intra-MRN (but not intra-DRN) infusions of WAY-100635 (3.0 mug) increased open arm exploration and reduced risk assessment. Importantly, these effects could not be attributed to a general reduction in locomotor activity. A similar, though somewhat weaker, pattern of behavioural change was observed in maze-experienced animals. This unexpected anxiolytic effect of 5-HT1A autoreceptor blockade in the MRN cannot be accounted fur by a disinhibition of 5-HT release in forebrain targets (e.g. hippocampus and amygdala), where stimulation of postsynaptic 5-HT1A receptors enhances anxiety-like responses. However, as the MRN also projects to the periaqueductal gray matter (PAG), an area known to be sensitive to the anti-aversive effects or 5-HT, it is argued that present results may reflect increased 5-HT release at this crucial midbrain locus within the neural circuitry of defense. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Análise imunoistoquímica da distribuição de Serotonina, transportador de serotonina e receptores de serotonina no hipotálamo do sagui (callithrix jacchus)

The hypothalamus is a diencephalic portion located around the third ventricle below the hypothalamic sulcus, limited by the optic chiasm, and by the mammillary bodies, acting as a center that integrates behavioral and homeostatic functions. Serotonin is a neurotransmitter produced in limited sites in the midbrain and brain stem, but is distributed throughout the central nervous system and has many functions, acting through specific receptors that are also distributed throughout the nervous system. Using immunohistochemical techniques, the aim of this study was to delineate the hypothalamic nuclei of the marmoset (Callithrix jacchus) and study the distribution of serotonin transporter and serotonin receptors in the hypothalamus of this species. We used the Nissl method to determine the cytoarchitecture of the hypothalamic nuclei, and immunohistochemistry to reveal the presence of NeuN as a method to determine the contours of the hypothalamic nuclei. As a result, we found serotonin containing fibers and terminals throughout the rostrocaudal extent of the hypothalamus, more concentrated in some nuclei, and even absent in some. Like serotonin, serotonin transporter was observed between pre-optic area and tuberal region of the hypothalamus, in densities and distribution similar to serotonin. The 5-HT1A and 5-HT1B receptors were found with minor differences among itselves regarding the disposition and intensity of staining.

The GABAergic system contributes to the anxiolytic-like effect of essential oil from Cymbopogon citratus (lemongrass)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Use of the elevated T-maze to study anxiety in mice

We have recently suggested that the elevated T-maze (ETM) is not a useful test to study different types of anxiety in mice if a procedure similar to that originally validated for rats is employed. The present study investigated whether procedural (five exposures in the enclosed arm instead of three as originally described for rats) and structural (transparent walls instead of opaque walls) changes to the ETM leads to consistent inhibitory avoidance acquisition (IAA) and low escape latencies in mice. Results showed that five exposures to the ETM provoked consistent IAA, an effect that was independent of the ETM used. However, the ETM with transparent walls (ETMt) seemed to be more suitable for the study of conditioned anxiety (i.e. IAA) and unconditioned fear (escape) in mice, since IAA (low baseline latency with a gradual increase over subsequent exposures) and escape (low latency) profiles rendered it sensitive to the effects of anxiolytic and anxiogenic drugs. In addition to evaluation of drug effects on IAA and escape, the number of line crossings in the apparatus were used to control for locomotor changes. Results showed that whereas diazepam (1.0-2.0 mg/kg) and flumazenil (10-30 mg/kg) impaired IAA, FG 7142 (10-30 mg/kg) did not provoke any behavioral change. Significantly, none of these benzodiazepine (BDZ) receptor ligands modified escape latencies. The 5-HT1A partial receptor agonist buspirone (1.0-2.0 mg/kg) and the 5-HT releaser fenfluramine (0.15-0.30 mg/kg) impaired IAA and facilitated escape, while the full 5-HT1A receptor agonist, 8-OH-DPAT (0.05-0.1 mg/kg) and the 5-HT2B/2C receptor antagonist, SER 082 (0.5-2.0 mg/kg) failed to modify either response. mCPP (0.5-2.0 mg/kg), a 5-HT2B/2C receptor agonist, facilitated IAA but did not alter escape latency. Neither antidepressant utilized in the current study, imipramine (1.0-5.0 mg/kg) and moclobemide (3.0-10 mg/kg) affected IAA or escape performance in mice. The well-known anxiogenic drugs yohimbine (2.0-8.0 mg/kg) and caffeine (10-30 mg/kg) did not selectively affect IAA, although caffeine did impair escape latencies. Present results suggest the ETMt is useful for the study of conditioned anxiety in mice. However, upon proximal threats (e.g. open arm exposure), mice do not exhibit escape behavior as an immediate defensive strategy, suggesting that latency to leave open arm is not a useful parameter to evaluate unconditioned fear in this species. (C) 2003 Elsevier B.V. All rights reserved.

Cardiovascular responses produced by central injection of hydrogen peroxide in conscious rats

Reactive oxygen species (ROS) have been shown to modulate neuronal synaptic transmission and may play a role on the autonomic control of the cardiovascular system. In this study we investigated the effects produced by hydrogen peroxide (H 2O 2) injected alone or combined with the anti-oxidant agent N-acetil-l-cysteine (NAC) or catalase into the fourth brain ventricle (4th V) on mean arterial pressure and heart rate of conscious rats. Moreover the involvement of the autonomic nervous system on the cardiovascular responses to H 2O 2 into the 4th V was also investigated. Male Holtzman rats (280-320 g) with a stainless steel cannula implanted into the 4th V and polyethylene cannulas inserted into the femoral artery and vein were used. Injections of H 2O 2 (0.5, 1.0 and 1.5 μmol/0.2 μL, n = 6) into the 4th V produced transient (for 10 min) dose-dependent pressor responses. The 1.0 and 1.5 μmol doses of H 2O 2 also produced a long lasting bradycardia (at least 24 h with the high dose of H 2O 2). Prior injection of N-acetyl-l-cysteine (250 nmol/1 μL/rat) into the 4th V blockade the pressor response and attenuated the bradycardic response to H 2O 2 (1 μmol/0.5 μL/rat, n = 7) into the 4th V. Intravenous (i.v.) atropine methyl bromide (1.0 mg/kg, n = 11) abolished the bradycardia but did not affect the pressor response to H 2O 2. Prazosin hydrochloride (1.0 mg/kg, n = 6) i.v. abolished the pressor response but did not affect the bradycardia. The increase in the catalase activity (500 UEA/1 μL/rat injected into the 4th V) also abolished both, pressor and bradycardic responses to H 2O 2. The results suggest that increased ROS availability into 4th V simultaneously activate sympathetic and parasympathetic outflow inducing pressor and bradycardic responses. © 2006 Elsevier Inc. All rights reserved.

Influência do espaçamento e poda de produção sobre a produtividade e aspectos tecnológicos do maracujá amarelo

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Comportamento de genótipos de feijão (Phaseolus vulgaris L.) na época das águas em São Manuel - SP

Pós-graduação em Agronomia (Agricultura) - FCA

Estudo farmacológico e neuroquímico dos óleos essenciais de Cymbopogon citratus (D.C) Stapf e Citrus ayrantium L

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Validação farmacológica da preferência claro-escuro em Danio rerio

A ansiedade é uma desordem complexa e com grande relevância clínica, cujo estudo com modelos animais é importante para pesquisar sobre seus mecanismos e drogas para o seu tratamento. O zebrafish figura como um potencial modelo animal para pesquisas farmacológicas da ansiedade. Um modelo de ansiedade é a preferência claro-escuro, que já foi validado comportamentalmente em zebrafish, contudo necessita de uma validação farmacológica. Objetiva-se descrever a sensibilidade da preferência claro-escuro em zebrafish adultos para as drogas mais utilizadas na clínica da ansiedade, foram administradas pela imersão do animal na solução: Benzodiazepínicos (Clonazepam); Agonistas parciais 5-HT1A (Buspirona); Antidepressivo tricíclico (Imipramina); Antidepressivo ISRS (Fluoxetina e Paroxetina); Antipsicóticos (Haloperidol e Risperidona); Psicostimulante (Dietilpropiona); Beta bloqueadores (Propranolol) e Depressores do SNC (Etanol). Os parâmetros analisados foram o tempo despendido pelo animal no ambiente escuro, o tempo da primeira latência e número de alternâncias. O clonazepam administrado por 300s aumentou o tempo no escuro na menor concentração e reduziu a atividade locomotora, a administração durante 600s da concentração intermediária diminuiu o tempo no escuro e da primeira latência, assim como aumentou a atividade locomotora, indicando efeito ansiolítico. A buspirona aumentou o tempo de permanência no escuro provavelmente devido a redução da atividade motora. A imipramina e a fluoxetina aumentaram o tempo no escuro e da primeira latência e diminuíram o número de alternâncias, indicando ação ansiogênica. A paroxetina não alterou o tempo no escuro, entretanto aumentou o tempo da primeira latência e diminuiu a atividade locomotora. O haloperidol diminuiu a ansiedade na menor concentração, curiosamente aumentou a atividade motora na maior concentração, ao contrário da risperidona que diminuiu a atividade na maior concentração. A dietilpropriona não modificou o tempo no escuro, mas aumentou o tempo da primeira latência e diminuiu a atividade motora apenas na menor concentração. O propranolol reduziu somente o tempo no escuro. O etanol foi efetivo na redução da ansiedade com a concentração intermediária e diminuiu a atividade locomotora em uma concentração menor Os dados corroboram com relatos da literatura em Danio rerio tanto neste modelo em administração intraperitoneal como em outros modelos por administração hídrica e em roedores, quando foi possível a comparação.

Administração subcrônica de nicotina modifica as respostas neuroendócrina e neuroquímica induzidas pelo teste de natação forçada

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)