RESUMEN
Antipsychotic agents are used for the treatment of psychotic symptoms in patients with several brain disorders, such as schizophrenia. Atypical and typical antipsychotics differ regarding their clinical and side-effects profile. Haloperidol is a representative typical antipsychotic drug and has potent dopamine receptor antagonistic functions; however, atypical antipsychotics have been developed and characterized an important advance in the treatment of schizophrenia and other psychotic disorders. Purine nucleotides and nucleosides, such as ATP and adenosine, constitute a ubiquitous class of extracellular signaling molecules crucial for normal functioning of the nervous system. Indirect findings suggest that changes in the purinergic system, more specifically in adenosinergic activity, could be involved in the pathophysiology of schizophrenia. We investigated the effects of typical and atypical antipsychotics on ectonucleotidase and adenosine deaminase (ADA) activities, followed by an analysis of gene expression patterns in zebrafish brain. Haloperidol treatment (9 µM) was able to decrease ATP hydrolysis (35%), whereas there were no changes in hydrolysis of ADP and AMP in brain membranes after antipsychotic exposure. Adenosine deamination in membrane fractions was inhibited (38%) after haloperidol treatment when compared to the control; however, no changes were observed in ADA soluble fractions after haloperidol exposure. Sulpiride (250 µM) and olanzapine (100 µM) did not alter ectonucleotidase and ADA activities. Haloperidol also led to a decrease in entpd2_mq, entpd3 and adal mRNA transcripts. These findings demonstrate that haloperidol is an inhibitor of NTPDase and ADA activities in zebrafish brain, suggesting that purinergic signaling may also be a target of pharmacological effects promoted by this drug.
Asunto(s)
Adenosina Desaminasa/metabolismo , Adenosina Trifosfatasas/metabolismo , Antipsicóticos/farmacología , Encéfalo/efectos de los fármacos , Encéfalo/enzimología , Pez Cebra/fisiología , Animales , Benzodiazepinas/farmacología , Femenino , Haloperidol/farmacología , Hidrólisis , Masculino , Olanzapina , Sulpirida/farmacología , Proteínas de Pez Cebra/metabolismoRESUMEN
Schizophrenia is a debilitating mental disorder with a global prevalence of 1% and its etiology remains poorly understood. In the current study we investigated the influence of antipsychotic drugs on the effects of MK-801 administration, which is a drug that mimics biochemical changes observed in schizophrenia, on Na(+), K(+)-ATPase activity and some parameters of oxidative stress in zebrafish brain. Our results showed that MK-801 treatment significantly decreased Na(+), K(+)-ATPase activity, and all antipsychotics tested prevented such effects. Acute MK-801 treatment did not alter reactive oxygen/nitrogen species by 2'7'-dichlorofluorscein (H2DCF) oxidation assay, but increased the levels of thiobarbituric acid reactive substances (TBARS), when compared with controls. Some antipsychotics such as sulpiride, olanzapine, and haloperidol prevented the increase of TBARS caused by MK-801. These findings indicate oxidative damage might be a mechanism involved in the decrease of Na(+), K(+)-ATPase activity induced by MK-801. The parameters evaluated in this study had not yet been tested in this animal model using the MK-801, suggesting that zebrafish is an animal model that can contribute for providing information on potential treatments and disease characteristics.
Asunto(s)
Antipsicóticos/farmacología , Química Encefálica/efectos de los fármacos , Maleato de Dizocilpina/antagonistas & inhibidores , Maleato de Dizocilpina/farmacología , Antagonistas de Aminoácidos Excitadores/farmacología , Estrés Oxidativo/efectos de los fármacos , ATPasa Intercambiadora de Sodio-Potasio/metabolismo , Pez Cebra/metabolismo , Animales , Benzodiazepinas/farmacología , Femenino , Fluoresceínas/metabolismo , Haloperidol/farmacología , Peroxidación de Lípido/efectos de los fármacos , Masculino , Membranas/efectos de los fármacos , Membranas/metabolismo , Proteínas del Tejido Nervioso/análisis , Proteínas del Tejido Nervioso/metabolismo , Olanzapina , Especies de Nitrógeno Reactivo/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Sulpirida/farmacología , Sustancias Reactivas al Ácido Tiobarbitúrico/metabolismoRESUMEN
Adenosine exerts neuromodulatory functions with mostly inhibitory effects, being considered an endogenous anticonvulsant. The hydrolysis of ATP by ectonucleotidases is an important source of adenosine, and adenosine deaminase (ADA) contributes to the regulation of this nucleoside concentration through its deamination. In this study, we tested the effect of pentylenetetrazole (PTZ)-induced seizures on ectonucleotidase and ADA activities in adult zebrafish brain. Our results have demonstrated that PTZ treatments did not alter ectonucleotidase and ADA activities in membranes and soluble fraction, respectively. However, ecto-ADA activity was significantly decreased in brain membranes of animals exposed to 5mM and 15 mM PTZ treatments (22.4% and 29.5%, respectively) when compared to the control group. Semiquantitative RT-PCR analysis did not show significant changes after the PTZ exposure on ADA gene expression. The decreased adenosine deamination observed in this study suggests a modulation of extracellular adenosine levels during PTZ-induced seizures in zebrafish.
Asunto(s)
Adenosina/metabolismo , Encéfalo/anatomía & histología , Encéfalo/metabolismo , Convulsivantes/farmacología , Pentilenotetrazol/farmacología , Convulsiones/inducido químicamente , Convulsiones/fisiopatología , Adenosina Desaminasa/metabolismo , Animales , Desaminación , Pirofosfatasas/metabolismo , Pez CebraRESUMEN
Schizophrenia is a severe mental illness characterized by positive and negative symptoms and cognitive deficits. Reduction of glutamatergic neurotransmission by NMDA receptor antagonists mimics symptoms of schizophrenia. 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. Studies have demonstrated that these behavioral changes are, in some cases, sensitive to remediation by antipsychotic drugs. The zebrafish has been proposed as a candidate to study the in vivo effects of several drugs and to discover new pharmacological targets. In the current study we investigated the ability of antipsychotic drugs to reverse schizophrenia-like symptoms produced by the NMDA receptor antagonist MK-801. Results showed that MK-801 (5µM) given pre-training hindered memory formation while both atypical antipsychotics sulpiride (250µM) and olanzapine (50µM) 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 (9µM) was ineffective to reverse those behavioral deficits. Therefore, MK-801-treated zebrafish showed some behavioral features observed in schizophrenia, such as cognitive and social interaction deficits, which were reverted by current available atypical drugs.
Asunto(s)
Antipsicóticos/uso terapéutico , Trastornos del Conocimiento/inducido químicamente , Trastornos del Conocimiento/tratamiento farmacológico , Maleato de Dizocilpina/toxicidad , Relaciones Interpersonales , Análisis de Varianza , Animales , Reacción de Prevención/efectos de los fármacos , Conducta Animal/efectos de los fármacos , Modelos Animales de Enfermedad , Interacciones Farmacológicas , Masculino , Estadísticas no Paramétricas , Pez CebraRESUMEN
Lithium has been used as an effective antimanic drug in humans and it is well known for its effects on neuropsychiatric disorders and neuronal communication. ATP and adenosine are important signaling molecules, and most nerves release ATP as a fast co-transmitter together with classical neurotransmitters such as acetylcholine. In this study, we evaluated the in vitro and in vivo effects of lithium on acetylcholinesterase and ectonucleotidase activities in zebrafish brain. There was a significant inhibition of ADP hydrolysis after in vivo exposure to lithium at 5 and 10 mg/l (27.6% and 29% inhibition, respectively), whereas an inhibitory effect was observed for AMP hydrolysis only at 10 mg/l (30%). Lithium treatment in vivo also significantly decreased the acetylcholinesterase activity at 10 mg/l (21.9%). The mRNA transcript levels of the genes encoding for these enzymes were unchanged after exposure to 5 and 10 mg/l lithium chloride. In order to directly evaluate the action of lithium on enzyme activities, we tested the in vitro effect of lithium at concentrations ranging from 1 to 1000 µM. There were no significant changes in zebrafish brain ectonucleotidase and acetylcholinesterase activities at all concentrations tested in vitro. Our findings show that lithium treatment can alter ectonucleotidase and acetylcholinesterase activities, which may regulate extracellular nucleotide, nucleoside, and acetylcholine levels. These data suggest that cholinergic and purinergic signaling may be targets of the pharmacological effects induced by this compound.
Asunto(s)
Acetilcolinesterasa/metabolismo , Encéfalo/efectos de los fármacos , Inhibidores de la Colinesterasa/farmacología , Litio/farmacología , Nucleótidos/metabolismo , Pez Cebra/metabolismo , Acetilcolinesterasa/genética , Adenosina Trifosfatasas/genética , Adenosina Trifosfatasas/metabolismo , Animales , Encéfalo/enzimología , Encéfalo/metabolismo , Relación Dosis-Respuesta a Droga , Femenino , Expresión Génica/efectos de los fármacos , Hidrólisis , Masculino , Nucleótidos/genética , Reacción en Cadena de la Polimerasa de Transcriptasa InversaRESUMEN
Iron is one the most abundant metals on the earth being essential for living organisms even though its free form can be toxic. The overload of this metal may be related with some disorders, like Alzheimer and Parkinson diseases, and hemochromatosis in the liver. The aim of the present study was to evaluate the effects of iron on acetylcholinesterase (AChE) activity in brain and liver of zebrafish and to investigate the possible correlation with the iron content in these tissues. Different corresponding concentrations of iron were tested using in vitro (0.018, 0.268, and 2.6 mM) and in vivo (1, 15, and 150 mg/l) assays. The in vitro studies showed that iron promoted a significant increase in AChE activity in brain (52%) and liver (53%) at the higher concentration (2.6 mM). In the in vivo assays, a significant increase in this enzyme activity was observed in the presence of 15 mg/l in both, brain (62%) and liver tissue (70%). Semiquantitative RT-PCR did not reveal significant changes in acetylthiocholinesterase mRNA levels. Moreover, we observed that iron content was significantly increased in liver tissue when exposed to 15 (226%) and 150 mg/l (200%). These results indicate that iron can promote significant alterations in AChE activity which probably is not directly related to the iron content in zebrafish tissues.
Asunto(s)
Acetilcolinesterasa/metabolismo , Regulación Enzimológica de la Expresión Génica/efectos de los fármacos , Hierro/toxicidad , Pez Cebra/metabolismo , Animales , Encéfalo/efectos de los fármacos , Encéfalo/enzimología , Relación Dosis-Respuesta a Droga , Femenino , Hígado/efectos de los fármacos , Hígado/enzimología , MasculinoRESUMEN
Aluminum is a metal that is known to impact fish species. The zebrafish has been used as an attractive model for toxicology and behavioral studies, being considered a model to study environmental exposures and human pathologies. In the present study, we have investigated the effect of aluminum exposure on brain acetylcholinesterase activity and behavioral parameters in zebrafish. In vivo exposure of zebrafish to 50 µg/L AlCl(3) for 96 h at pH 5.8 significantly increased (36%) acetylthiocholine hydrolysis in zebrafish brain. There were no changes in acetylcholinesterase (AChE) activity when fish were exposed to the same concentration of AlCl(3) at pH 6.8. In vitro concentrations of AlCl(3) varying from 50 to 250 µM increased AChE activity (28% to 33%, respectively). Moreover, we observed that animals exposed to AlCl(3) at pH 5.8 presented a significant decrease in locomotor activity, as evaluated by the number of line crossings (25%), distance traveled (14.1%), and maximum speed (24%) besides an increase in the absolute turn angle (12.7%). These results indicate that sublethal levels of aluminum might modify behavioral parameters and acetylcholinesterase activity in zebrafish brain.
Asunto(s)
Acetilcolinesterasa/metabolismo , Compuestos de Aluminio/toxicidad , Conducta Animal/efectos de los fármacos , Encéfalo/efectos de los fármacos , Cloruros/toxicidad , Exposición a Riesgos Ambientales/efectos adversos , Contaminantes Ambientales/toxicidad , Cloruro de Aluminio , Animales , Encéfalo/enzimología , Pruebas de Enzimas , Femenino , Humanos , Concentración de Iones de Hidrógeno , Masculino , Actividad Motora/efectos de los fármacos , Pez CebraRESUMEN
Glutamate N-methyl-d-aspartate (NMDA) receptor antagonists, such as dizocilpine (MK-801), elicit schizophrenia-like symptoms in humans and a behavioral syndrome in rodents, characterized by hyperlocomotion and stereotyped actions, which is antagonized by antipsychotic drugs. Animal models of schizophrenia have been established and used for the development of new antipsychotic drugs. In this work we characterized the behavioral effects of MK-801 and investigated the effect of typical and atypical antipsychotic treatments on locomotor activity as well on the hyperlocomotion induced by MK-801 in zebrafish. MK-801 (20 microM) 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. All tested antipsychotics counteracted MK-801-induced hyperactivity on all parameters analyzed and at doses that, given alone, had no effect on spontaneous locomotor activity. The results suggest a similar profile between typical and atypical antipsychotics in the reversal of locomotor disorders induced by MK-801. Moreover, an anxiolytic effect was verified at 30 and 60 min of MK-801 exposure, which was not reversed by antipsychotics tested in this work. In addition, olanzapine, which alone caused an anxiolytic response, when given with MK-801 potentiated the latter's effect on anxiety. In this work we demonstrated the value of the zebrafish, a simple to use animal model, in developing some behavioral features observed in schizophrenia, which may indicate a new approach for drug screening.
Asunto(s)
Antipsicóticos/farmacología , Maleato de Dizocilpina/antagonistas & inhibidores , Alucinógenos/antagonistas & inhibidores , Hipercinesia/prevención & control , Animales , Maleato de Dizocilpina/farmacología , Antagonistas de Aminoácidos Excitadores/farmacología , Femenino , Alucinógenos/farmacología , Hipercinesia/inducido químicamente , Masculino , Actividad Motora/efectos de los fármacos , Pez CebraRESUMEN
Mercury is a widespread environmental contaminant that is neurotoxic even at very low concentrations. In this study we investigated the effects of mercury chloride on soluble and membrane adenosine deaminase (ADA) activity and gene expression in zebrafish brain. Inhibition of ADA activity was observed in the soluble fraction at 5-250 microM HgCl(2) (84.6-92.6%, respectively), whereas inhibition occurred at 50-250 microM in membrane fractions (20.9-26%, respectively). We performed in vitro experiments with chelants (EDTA and DTT) to test if these compounds prevented or reversed the inhibition caused by HgCl(2) and found that the inhibition was partially or fully abolished. The effect on ADA activity in soluble and membrane fractions was evaluated after acute (24h) and subchronic (96h) in vivo exposure of zebrafish to 20 microg/l HgCl(2). ADA activity in the soluble fraction was decreased after both acute (24.5%) and subchronic (40.8%) exposures, whereas in brain membranes the enzyme was inhibited only after subchronic exposure (21.9%). Semiquantitative RT-PCR analysis showed that HgCl(2) did not alter ADA gene expression. This study demonstrated that ADA activity was inhibited by mercury and this effect might be related to the neurotoxicity of this heavy metal.
Asunto(s)
Adenosina Desaminasa/metabolismo , Encéfalo/efectos de los fármacos , Desinfectantes/farmacología , Cloruro de Mercurio/farmacología , Pez Cebra/anatomía & histología , Actinas/genética , Actinas/metabolismo , Adenosina Desaminasa/clasificación , Adenosina Desaminasa/genética , Análisis de Varianza , Animales , Encéfalo/enzimología , Encéfalo/fisiopatología , Quelantes/farmacología , Ditiotreitol/farmacología , Relación Dosis-Respuesta a Droga , Ácido Edético/farmacologíaRESUMEN
Antipsychotic agents are widely used for the treatment of psychotic symptoms in patients with several brain disorders. Antipsychotic drugs principally affect dopamine systems with the newer ones also affecting serotonin, norepinephrine, and histamine systems. Other transmitter systems can be involved with selected antipsychotic drugs but effects on cholinergic system are less known. Considerable evidence has shown that complex interactions between dopaminergic and cholinergic systems are critical for the proper regulation of motor control and memory. These neurotransmitter systems have been studied in zebrafish, which has recently become a focus of neurobehavioral studies. Therefore, we have evaluated the in vitro and in vivo effects of sulpiride, olanzapine, and haloperidol on acetylcholinesterase activity and ache expression pattern in zebrafish brain. For in vitro studies, all drugs were able to promote a decrease on acetylcholinesterase activity. For in vivo studies, olanzapine and sulpiride exposure did not change acetylcholinesterase activity. In contrast, this enzyme activity was significantly increased at 5 and 9 microM haloperidol (29.9% and 20.4%, respectively). Haloperidol exposure was able to increase acetylcholinesterase mRNA transcripts. These findings have suggested that the alterations in zebrafish acetylcholinesterase could reveal molecular mechanisms related to cholinergic signaling induced by antipsychotic treatment.
Asunto(s)
Acetilcolinesterasa/biosíntesis , Antipsicóticos/farmacología , Encéfalo/enzimología , Regulación Enzimológica de la Expresión Génica/fisiología , Animales , Benzodiazepinas/farmacología , Encéfalo/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Activación Enzimática/efectos de los fármacos , Activación Enzimática/fisiología , Femenino , Regulación Enzimológica de la Expresión Génica/efectos de los fármacos , Haloperidol/farmacología , Masculino , Olanzapina , Pez CebraRESUMEN
Haloperidol (HAL), olanzapine (OLZ), and sulpiride (SULP) are antipsychotic drugs widely used in the pharmacotherapy of psychopathological symptoms observed in schizophrenia or mood-related psychotic symptoms in affective disorders. Here, we tested the in vitro effects of different concentrations of a typical (HAL) and two atypical (OLZ and SULP) antipsychotic drugs on ectonucleotidase activities from zebrafish brain membranes. HAL inhibited ATP (28.9%) and ADP (26.5%) hydrolysis only at 250 microM. OLZ decreased ATPase activity at all concentrations tested (23.8-60.7%). SULP did not promote significant changes on ATP hydrolysis but inhibited ADP hydrolysis at 250 microM (25.6%). All drugs tested, HAL, OLZ, and SULP, did not promote any significant changes on 5'-nucleotidase activity in the brain membranes of zebrafish. These findings demonstrated that antipsychotic drugs could inhibit NTPDase activities whereas did not change 5'-nucleotidase. Such modulation can alter the adenosine levels, since the ectonucleotidase pathway is an important source of extracellular adenosine. Thus, it is possible to suggest that changes promoted by antipsychotic drugs in the bilayer membrane could alter the NTPDase activities, modulating extracellular ATP and adenosine levels.