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Several lines of evidence suggest that antidepressant drugs may act by modulating neuroplasticity pathways in key brain areas like the hippocampus. We have reported that chronic treatment with fasudil, a Rho-associated protein kinase inhibitor, prevents both chronic stress-induced depressive-like behavior and morphological changes in CA1 area. Here, we examined the ability of fasudil to (i) prevent stress-altered behaviors, (ii) influence the levels/phosphorylation of glutamatergic receptors and (iii) modulate signaling pathways relevant to antidepressant actions. 89 adult male Sprague-Dawley rats received intraperitoneal fasudil injections (10 mg/kg/day) or saline vehicle for 18 days. Some of these animals were daily restraint-stressed from day 5-18 (2.5 h/day). 24 hr after treatments, rats were either evaluated for behavioral tests (active avoidance, anxiety-like behavior and object location) or euthanized for western blot analyses of hippocampal whole extract and synaptoneurosome-enriched fractions. We report that fasudil prevents stress-induced impairments in active avoidance, anxiety-like behavior and novel location preference, with no effect in unstressed rats. Chronic stress reduced phosphorylations of ERK-2 and CREB, and decreased levels of GluA1 and GluN2A in whole hippocampus, without any effect of fasudil. However, fasudil decreased synaptic GluA1 Ser831 phosphorylation in stressed animals. Additionally, fasudil prevented stress-decreased phosphorylation of GSK-3ß at Ser9, in parallel with an activation of the mTORC1/4E-BP1 axis, both in hippocampal synaptoneurosomes, suggesting the activation of the AKT pathway. Our study provides evidence that chronic fasudil treatment prevents chronic stress-altered behaviors, which correlated with molecular modifications of antidepressant-relevant signaling pathways in hippocampal synaptoneurosomes.
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The entactogen MDMA (3,4-methylenedioxy-methamphetamine, "Ecstasy") exerts its psychotropic effects acting primarily as a substrate of the serotonin transporter (SERT) to induce a non-exocytotic release of serotonin. Nevertheless, the roles of specific positions of the aromatic ring of MDMA associated with the modulation of typical entactogenic effects, using analogs derived from the MDMA template, are still not fully understood. Among many possibilities, aromatic halogenation of the phenylalkylamine moiety may favor distribution to the brain due to increased lipophilicity, and sometimes renders psychotropic substances of high affinity for their molecular targets and high potency in humans. In the present work, a new MDMA analog brominated at C(2) of the aromatic ring (2-Br-4,5-MDMA) has been synthesized and pharmacologically characterized in vitro and in vivo. First, binding competition experiments against the SERT-blocker citalopram were carried out in human platelets and compared with MDMA. Besides, its effects on platelet aggregation were performed in platelet enriched human plasma using collagen as aggregation inductor. Second, as platelets are considered an appropriate peripheral model for estimating central serotonin availability, the functional effects of 2-Br-4,5-MDMA and MDMA on ATP release during human platelet aggregation were evaluated. The results obtained showed that 2-Br-4,5-MDMA exhibits higher affinity for SERT than MDMA and fully abolishes both platelet aggregation and ATP release, resembling the pharmacological profile of citalopram. Subsequent in vivo evaluation in rats at three dose levels showed that 2-Br-4,5-MDMA lacks all key MDMA-like behavioral responses in rats, including hyperlocomotion, enhanced active avoidance conditioning responses and increased social interaction. Taken together, the results obtained are consistent with the notion that 2-Br-4,5-MDMA should not be expected to be an MDMA-like substrate of SERT, indicating that aromatic bromination at C(2) modulates the pharmacodynamic properties of the substrate MDMA, yielding a citalopram-like compound.
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Several studies have shown that a single exposure to stress may improve or impair learning and memory processes, depending on the timing in which the stress event occurs with relation to the acquisition phase. However, to date there is no information about the molecular changes that occur at the synapse during the stress-induced memory modification and after a recovery period. In particular, there are no studies that have evaluated-at the same time-the temporality of stress and stress recovery period in hippocampal short-term memory and the effects on dendritic spine morphology, along with variations in N-methyl-D-aspartate (NMDA) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunits. The aim of our study was to take a multidimensional approach to investigate concomitant behavioral, morphological and molecular changes induced by a single restraint stress exposure (2.5 h) and a recovery period of 6 and 24 h in rats. We found that acute stress elicited a reduced preference to explore an object placed in a novel position (a hippocampal-dependent task). These changes were accompanied by increased activity of LIM kinase I (LIMK; an actin-remodeling protein) and increased levels of NR2A subunits of NMDA receptors. After 6 h of recovery from stress, rats showed similar preference to explore an object placed in a novel or familiar position, but density of immature spines increased in secondary CA1 apical dendrites, along with a transient rise in GluA2 AMPA receptor subunits. After 24 h of recovery from stress, the animals showed a preference to explore an object placed in a novel position, which was accompanied by a normalization of NMDA and AMPA receptor subunits to control values. Our data suggest that acute stress produces reversible molecular and behavioral changes 24 h after stress, allowing a full reestablishment of hippocampal-related memory. Further studies need to be conducted to deepen our understanding of these changes and their reciprocal interactions.Adaptive stress responses are a promising avenue to develop interventions aiming at restoring hippocampal function impaired by repetitive stress exposure.
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Dopamine oxidation in the pathway leading to neuromelanin formation generates the ortho-quinone aminochrome, which is potentially neurotoxic but normally rapidly converted by DT-diaphorase to nontoxic leukoaminochrome. However, when administered exogenously into rat striatum, aminochrome is able to produce damage to dopaminergic neurons. Because of a recent report that substantia nigra pars compacta (SNpc) tyrosine hydroxylase (T-OH) levels were unaltered by aminochrome when there was cell shrinkage of dopaminergic neurons along with a reduction in striatal dopamine release, the following study was conducted to more accurately determine the role of DT-diaphorase in aminochrome neurotoxicity. In this study, a low dose of aminochrome (0.8 nmol) with or without the DT-diaphorase inhibitor dicoumarol (0.2 nmol) was injected into the left striatum of rats. Intrastriatal 6-hydroxydopamine (6-OHDA, 32 nmol) was used as a positive neurotoxin control in other rats. Two weeks later, there was significant loss in numbers of T-OH immunoreactive fibers in SNpc, also a loss in cell density in SNpc, and prominent apomorphine (0.5 mg/kg sc)-induced contralateral rotations in rats that had been treated with aminochrome, with aminochrome/dicoumarol, or with 6-OHDA. Findings demonstrate that neurotoxic aminochrome is able to exert neurotoxicity only when DT-diaphorase is suppressed-implying that DT-diaphorase is vital in normally suppressing toxicity of in vivo aminochrome, generated in the pathway towards neuromelanin formation.
Assuntos
Inibidores Enzimáticos/uso terapêutico , Indolquinonas/toxicidade , NAD(P)H Desidrogenase (Quinona)/metabolismo , Síndromes Neurotóxicas/etiologia , Neurotoxinas/toxicidade , Animais , Dicumarol/farmacologia , Modelos Animais de Doenças , Masculino , Oxirredução/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Técnicas Estereotáxicas , Tirosina 3-Mono-Oxigenase/metabolismoRESUMO
Background: To establish an educational environment that ensures the quality of the teaching-learning process is a challenge for any educational institution. The questionnaire DREEM (Dundee Ready Educational Environment Measure) is used to identify strengths and weaknesses of an educational environment and to compare different medical schools. Aim: To evaluate the changes in the perception of educational environment by students of the Schools of Medicine of the University of Zaragoza, UZar (Spain) and the University of Chile, UCh (Chile) at two points in their curricula. Material and Methods: DREEM questionnaire was answered by 90 students from the UZar and 87 students of the UCh, when they were in the first year (2009) and in the fourth year of their career (2012). Results: At both universities the overall mean scores of DREAM were significantly higher in students in their first year than those obtained in the fourth year (137.5/118.3 for UZar and 128.6/118.8 for UCh). Items with worse perception in the fourth year were observed in subscales Learning Perception and Atmosphere Perception. Items with good evaluation (≥ 3.0) were the subscales Perception of teachers, academic self-perception, perception of Environment and Social Self-perception. Conclusions: The perception of Chilean and Spanish students about their educational environments indicates that the stage of their medical training is more important than the geographical context or educational institution.
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Humanos , Adulto Jovem , Faculdades de Medicina , Estudantes de Medicina/psicologia , Currículo , Educação de Graduação em Medicina , Avaliação Educacional , Percepção , Meio Social , Espanha , Fatores de Tempo , Chile , Inquéritos e Questionários , Estudos Longitudinais , Estatísticas não ParamétricasRESUMO
L-Dopa continues to be the gold drug in Parkinson's disease (PD) treatment from 1967. The failure to translate successful results from preclinical to clinical studies can be explained by the use of preclinical models which do not reflect what happens in the disease since these induce a rapid and extensive degeneration; for example, MPTP induces a severe Parkinsonism in only 3 days in humans contrasting with the slow degeneration and progression of PD. This study presents a new anatomy and develops preclinical model based on aminochrome which induces a slow and progressive dysfunction of dopaminergic neurons. The unilateral injection of aminochrome into rat striatum resulted in (1) contralateral rotation when the animals are stimulated with apomorphine; (2) absence of significant loss of tyrosine hydroxylase-positive neuronal elements both in substantia nigra and striatum; (3) cell shrinkage; (4) significant reduction of dopamine release; (5) significant increase in GABA release; (6) significant decrease in the number of monoaminergic presynaptic vesicles; (7) significant increase of dopamine concentration inside of monoaminergic vesicles; (8) significant increase of damaged mitochondria; (9) significant decrease of ATP level in the striatum (10) significant decrease in basal and maximal mitochondrial respiration. These results suggest that aminochrome induces dysfunction of dopaminergic neurons where the contralateral behavior can be explained by aminochrome-induced ATP decrease required both for anterograde transport of synaptic vesicles and dopamine release. Aminochrome could be implemented as a new model neurotoxin to study Parkinson's disease.
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Neurônios Dopaminérgicos/efeitos dos fármacos , Indolquinonas/farmacologia , Doença de Parkinson/patologia , Trifosfato de Adenosina/metabolismo , Animais , Comportamento Animal/efeitos dos fármacos , Cromatografia Líquida de Alta Pressão , Corpo Estriado/metabolismo , Modelos Animais de Doenças , Dopamina/análise , Neurônios Dopaminérgicos/metabolismo , Neurônios Dopaminérgicos/patologia , Humanos , Indolquinonas/síntese química , Indolquinonas/química , Masculino , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Consumo de Oxigênio/efeitos dos fármacos , Consumo de Oxigênio/fisiologia , Doença de Parkinson/metabolismo , Doença de Parkinson/veterinária , Ratos , Ratos Sprague-Dawley , Substância Negra/metabolismo , Vesículas Sinápticas/metabolismo , Tirosina 3-Mono-Oxigenase/metabolismo , Ácido gama-Aminobutírico/análiseRESUMO
BACKGROUND: To establish an educational environment that ensures the quality of the teaching-learning process is a challenge for any educational institution. The questionnaire DREEM (Dundee Ready Educational Environment Measure) is used to identify strengths and weaknesses of an educational environment and to compare different medical schools. AIM: To evaluate the changes in the perception of educational environment by students of the Schools of Medicine of the University of Zaragoza, UZar (Spain) and the University of Chile, UCh (Chile) at two points in their curricula. MATERIAL AND METHODS: DREEM questionnaire was answered by 90 students from the UZar and 87 students of the UCh, when they were in the first year (2009) and in the fourth year of their career (2012). RESULTS: At both universities the overall mean scores of DREAM were significantly higher in students in their first year than those obtained in the fourth year (137.5/118.3 for UZar and 128.6/118.8 for UCh). Items with worse perception in the fourth year were observed in subscales Learning Perception and Atmosphere Perception. Items with good evaluation (≥ 3.0) were the subscales Perception of teachers, academic self-perception, perception of Environment and Social Self-perception. CONCLUSIONS: The perception of Chilean and Spanish students about their educational environments indicates that the stage of their medical training is more important than the geographical context or educational institution.
Assuntos
Currículo , Educação de Graduação em Medicina , Avaliação Educacional , Faculdades de Medicina , Estudantes de Medicina , Chile , Humanos , Estudos Longitudinais , Percepção , Meio Social , Espanha , Estatísticas não Paramétricas , Estudantes de Medicina/psicologia , Inquéritos e Questionários , Fatores de Tempo , Adulto JovemRESUMO
Chronic stress promotes cognitive impairment and dendritic spine loss in hippocampal neurons. In this animal model of depression, spine loss probably involves a weakening of the interaction between pre- and postsynaptic cell adhesion molecules, such as N-cadherin, followed by disruption of the cytoskeleton. N-cadherin, in concert with catenin, stabilizes the cytoskeleton through Rho-family GTPases. Via their effector LIM kinase (LIMK), RhoA and ras-related C3 botulinum toxin substrate 1 (RAC) GTPases phosphorylate and inhibit cofilin, an actin-depolymerizing molecule, favoring spine growth. Additionally, RhoA, through Rho kinase (ROCK), inactivates myosin phosphatase through phosphorylation of the myosin-binding subunit (MYPT1), producing actomyosin contraction and probable spine loss. Some micro-RNAs negatively control the translation of specific mRNAs involved in Rho GTPase signaling. For example, miR-138 indirectly activates RhoA, and miR-134 reduces LIMK1 levels, resulting in spine shrinkage; in contrast, miR-132 activates RAC1, promoting spine formation. We evaluated whether N-cadherin/ß-catenin and Rho signaling is sensitive to chronic restraint stress. Stressed rats exhibit anhedonia, impaired associative learning, and immobility in the forced swim test and reduction in N-cadherin levels but not ß-catenin in the hippocampus. We observed a reduction in spine number in the apical dendrites of CA1 pyramidal neurons, with no effect on the levels of miR-132 or miR-134. Although the stress did not modify the RAC-LIMK-cofilin signaling pathway, we observed increased phospho-MYPT1 levels, probably mediated by RhoA-ROCK activation. Furthermore, chronic stress raises the levels of miR-138 in accordance with the observed activation of the RhoA-ROCK pathway. Our findings suggest that a dysregulation of RhoA-ROCK activity by chronic stress could potentially underlie spine loss in hippocampal neurons.
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Caderinas/metabolismo , Espinhas Dendríticas/metabolismo , Depressão/patologia , Hipocampo/patologia , Neurônios/ultraestrutura , Quinases Associadas a rho/metabolismo , Animais , Aprendizagem da Esquiva , Peso Corporal/fisiologia , Depressão/etiologia , Modelos Animais de Doenças , Masculino , MicroRNAs/genética , MicroRNAs/metabolismo , Neurônios/patologia , Ratos , Ratos Sprague-Dawley , Estatísticas não Paramétricas , Estresse Fisiológico , Sacarose/metabolismo , Edulcorantes/metabolismo , Natação/psicologia , beta Catenina/genética , beta Catenina/metabolismoRESUMO
Prenatal stress causes predisposition to cognitive and emotional disturbances and is a risk factor towards the development of neuropsychiatric conditions like depression, bipolar disorders and schizophrenia. The extracellular protein Reelin, expressed by Cajal-Retzius cells during cortical development, plays critical roles on cortical lamination and synaptic maturation, and its deregulation has been associated with maladaptive conditions. In the present study, we address the effect of prenatal restraint stress (PNS) upon Reelin expression and signaling in pregnant rats during the last 10 days of pregnancy. Animals from one group, including control and PNS exposed fetuses, were sacrificed and analyzed using immunohistochemical, biochemical, cell biology and molecular biology approaches. We scored changes in the expression of Reelin, its signaling pathway and in the methylation of its promoter. A second group included control and PNS exposed animals maintained until young adulthood for behavioral studies. Using the optical dissector, we show decreased numbers of Reelin-positive neurons in cortical layer I of PNS exposed animals. In addition, neurons from PNS exposed animals display decreased Reelin expression that is paralleled by changes in components of the Reelin-signaling cascade, both in vivo and in vitro. Furthermore, PNS induced changes in the DNA methylation levels of the Reelin promoter in culture and in histological samples. PNS adult rats display excessive spontaneous locomotor activity, high anxiety levels and problems of learning and memory consolidation. No significant visuo-spatial memory impairment was detected on the Morris water maze. These results highlight the effects of prenatal stress on the Cajal-Retzius neuronal population, and the persistence of behavioral consequences using this treatment in adults, thereby supporting a relevant role of PNS in the genesis of neuropsychiatric diseases. We also propose an in vitro model that can yield new insights on the molecular mechanisms behind the effects of prenatal stress.
Assuntos
Moléculas de Adesão Celular Neuronais/genética , Metilação de DNA , Proteínas da Matriz Extracelular/genética , Exposição Materna , Transtornos Mentais/etiologia , Proteínas do Tecido Nervoso/genética , Efeitos Tardios da Exposição Pré-Natal , Regiões Promotoras Genéticas , Serina Endopeptidases/genética , Estresse Fisiológico , Estresse Psicológico , Animais , Animais Recém-Nascidos , Antígenos Nucleares/genética , Antígenos Nucleares/metabolismo , Comportamento Animal , Moléculas de Adesão Celular Neuronais/metabolismo , Córtex Cerebral/metabolismo , Quinase 5 Dependente de Ciclina/metabolismo , Modelos Animais de Doenças , Proteínas da Matriz Extracelular/metabolismo , Feminino , Proteínas do Tecido Nervoso/metabolismo , Neurônios/metabolismo , Gravidez , Ratos , Proteína Reelina , Serina Endopeptidases/metabolismo , Transdução de SinaisRESUMO
Fluoxetine is currently being administered for long-term maintenance and for prophylactic reasons following the remission of depressive symptoms and several other psychiatric and neurological conditions. We have previously found that in naïve adult male rats, repetitive administration of fluoxetine induced maturation of telencephalic dendritic spines. This finding was associated with the presence of a higher proportion of GluA2- and GluN2A-containing glutamate receptors. To gain further insight into the possible consequences of such synaptic re-organization on learning and memory processes, we evaluated hippocampal- and non-hippocampal-dependent memories following administration of 0.7 mg/kg fluoxetine for four weeks. Standard behavioral tasks were used: the Morris Water Maze (MWM) and Object Location Memory (OLM) tasks to assess spatial memory and the Novel Object Recognition (NOR) task to assess recognition memory. We found that treated rats showed normal learning and short-term memory (1 h post-learning). However, either recent (24 h) or remote (17 days) memories were impaired depending upon the task. Interestingly, spatial memory impairment spontaneously reverted after 6 weeks of fluoxetine withdrawal.