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Previous issue date: 2011-11-29 / Schizophrenia is a severe mental illness characterized by positive and negative symptoms and cognitive deficits. This pathology is still poorly understood. Reduction of glutamatergic neurotransmission by NMDA receptor antagonists mimics disease symptoms. Many animal models have shown their importance in the study of this disease and the zebrafish has been proposed as a promissor model to study the in vivo effects of several drugs and to discover new pharmacological targets. In this study we characterized the behavioral syndrome produced by the NMDA receptor antagonist, MK-801, exposure in zebrafish and investigated the ability of antipsychotic drugs to reverse the schizophrenia-like symptoms. MK-801 (20 μM) increased the locomotor behavior as measured by the number of line crossings, distance traveled, and the mean speed in the tank test after 15, 30, and 60 min of exposure. The antipsychotics sulpiride, olanzapine, and haloperidol counteracted MK-801-induced hyperactivity on all parameters analyzed and at doses that, given alone, had no effect on spontaneous locomotor activity. Modeling social interaction and cognitive impairment in animals can be of great benefit in the effort to develop novel treatments for negative and cognitive symptoms of schizophrenia. Results showed that MK-801 (5 μM) given pre-training hindered memory formation while both atypical antipsychotics sulpiride (250 μM) and olanzapine (50 μM) improved MK-801-induced amnesia. The same change was observed in the social interaction task, where atypical antipsychotics reversed the MK-801-induced social interaction deficit whereas the typical antipsychotic haloperidol (9 μM) was ineffective to reverse those behavioral deficits. Some evidence suggests that changes in the purinergic system, more specifically in adenosinergic activity, could be involved in the physiopathology of schizophrenia. In this study, we demonstrated that haloperidol treatment (9 μM) was able to decrease ATP hydrolysis (35%), whereas there were no significant changes in ADP and AMP hydrolysis in brain membranes. Adenosine deaminase activity in membrane fractions was significantly inhibited (38%) after haloperidol treatment when compared to the control group. Furthermore, haloperidol exposure also led to a decrease in NTPDase gene expression (entpd2_mq and entpd3), and adenosine deaminase (adal). Considering that the enzyme Na+,K+-ATPase is essencial to brain normal function, we evaluated the effect of MK-801 and antipsychotic drugs on activity this enzyme. Our results showed that MK-801 treatment significantly decreased Na+,K+-ATPase activity, and all antipsychotics tested prevented such effects. Moreover, it is known that oxidative stress may be associated with the physiopathology of schizophrenia and the Na+,K+-ATPase is particularly susceptible to free radical attack. We showed that MK-801 treatment did not alter reactive oxygen/nitrogen species by 2′7′-dichlorofluorscein (DCF) oxidation assay, but increased the levels of thiobarbituric acid reactive substances (TBARS), when compared to controls. The antipsychotics sulpiride, olanzapine, and haloperidol prevented the increase of TBARS caused by MK-801. Therefore, we demonstrated that zebrafish might present some behavioral and biochemical features observed in schizophrenia, being considered a promising animal model able to contribute for providing information on potential treatments and disease characteristics. / A esquizofrenia ? uma doen?a mental grave caracterizada por sintomas positivos, negativos e d?ficits cognitivos que ainda ? pouco compreendida. A redu??o da neurotransmiss?o glutamat?rgica por antagonistas dos receptores NMDA mimetiza os sintomas da esquizofrenia. Muitos modelos animais t?m mostrado sua import?ncia para o estudo dessa doen?a, e o peixe-zebra tem sido proposto como um modelo promissor para estudar os efeitos in vivo de v?rias drogas e descobrir novos alvos farmacol?gicos. Neste estudo caracterizamos a s?ndrome comportamental produzida pela exposi??o ao antagonista do receptor NMDA, MK-801, no peixe zebra, e investigamos a capacidade dos f?rmacos antipsic?ticos em reverter estes sintomas. MK-801 (20 μM) aumentou o comportamento locomotor que foi medido pelo n?mero de linhas cruzadas, a dist?ncia percorrida e a velocidade m?dia no aqu?rio teste, ap?s 15, 30 e 60 min de exposi??o. Os antipsic?ticos sulpirida, olanzapina e haloperidol reverteram as altera??es locomotoras induzidas pelo MK-801 em todos os par?metros testados, e em doses que administrado isoladamente n?o tiveram efeito sobre a atividade locomotora. Modelos de intera??o social e d?ficits cognitivos em animais pode ser de grande utilidade para o desenvolvimento de novos tratamentos para os sintomas negativos e cognitivos da esquizofrenia. Os resultados mostraram que o MK-801 (5 μM) administrado antes do treino impediu a forma??o da mem?ria, enquanto ambos os antipsic?ticos at?picos sulpirida (250 μM) e olanzapina (50 μM) melhoraram a amn?sia. A mesma altera??o foi observada na tarefa de intera??o social, onde os antipsic?ticos at?picos reverteram o d?ficit de intera??o social induzida pelo MK-801, enquanto o antipsic?tico tipico testado, o haloperidol (9 μM), n?o foi capaz de reverter esse d?ficit comportamental. Algumas evid?ncias sugerem que mudan?as no sistema purin?rgico, mais especificamente na atividade adenosin?rgica, poderiam estar envolvidos na fisiopatologia da esquizofrenia. Nesse estudo, mostramos que o tratamento com haloperidol (9 μM) foi capaz de diminuir a hidr?lise de ATP (35%), enquanto que n?o houve mudan?as significativas na hidr?lise de ADP e AMP em membranas cerebrais. A atividade da ADA em fra??es de membrana tamb?m foi inibida significativamente (38%) ap?s o tratamento com haloperidol, quando comparado ao grupo controle. Al?m disso, a exposi??o ao haloperidol tamb?m promoveu uma diminui??o na express?o g?nica das NTPDases (entpd2_mq e entpd3) e adenosina desaminase (adal). Considerando que a enzima Na+, K+- ATPase ? essencial para a fun??o cerebral normal, avaliamos os efeitos do MK-801 e farmacos antipsic?ticos na atividade desta enzima. Nossos resultados mostraram que o tratamento com MK-801 diminuiu significativamente a atividade da Na+, K+-ATPase, e todos os antipsic?ticos testados impediram tais efeitos. Sabe-se que o estresse oxidativo pode estar associado com a fisiopatologia da esquizofrenia e que a Na+,K+-ATPase ? particularmente suscet?vel ao ataque de radicais livres. Mostramos que o tratamento com MK-801 n?o alterou as esp?cies reativas de oxig?nio/nitrog?nio pelo ensaio de oxida??o 2'7'-diclorofluorosce?na (DCF), mas aumentou os n?veis de subst?ncias reativas ao ?cido tiobarbit?rico (TBARS). Os antipsic?ticos haloperidol, sulpirida e olanzapina preveniram o aumento nos n?veis de TBARS induzidos pelo MK-801. Portanto, demonstramos que o peixe zebra pode apresentar algumas caracter?sticas comportamentais e bioqu?micas observadas na esquizofrenia, sendo considerado um promissor modelo animal capaz de contribuir na obten??o de informa??es sobre potenciais tratamentos e caracter?sticas da doen?a.
| Identifer | oai:union.ndltd.org:IBICT/oai:tede2.pucrs.br:tede/5421 |
| Date | 29 November 2011 |
| Creators | Bender, Kelly Juliana Seibt |
| Contributors | Bonan, Carla Denise |
| Publisher | Pontif?cia Universidade Cat?lica do Rio Grande do Sul, Programa de P?s-Gradua??o em Biologia Celular e Molecular, PUCRS, BR, Faculdade de Bioci?ncias |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
| Format | application/pdf |
| Source | reponame:Biblioteca Digital de Teses e Dissertações da PUC_RS, instname:Pontifícia Universidade Católica do Rio Grande do Sul, instacron:PUC_RS |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | 8198246930096637360, 600, 600, 36528317262667714 |
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