Efeito das tarefas comportamentais de habituação e esquiva inibitória sobre a fosforilação in vitro de proteínas do citoesqueleto de hipocampo de ratos

Neste trabalho utilizamos uma fração citoesquelética insolúvel em Triton X-100 obtida a partir de hipocampo de ratos adultos a qual era incubada com ³²P-ATP in vitro. As fosfoproteínas foram identificadas através de eletroforese bidimensional em condições de não equilíbrio, imunodetecção e através da utilização de um padrão de tubulina. São elas: NF-M, sinapsina 1, NF-L, α tubulina e GFAP. As atividades quinásicas endógenas dependentes de 2° mensageiro associadas à fração citoesquelética foram estudadas através da utilização de seus ativadores específicos. Os resultados indicaram que a fração citoesquelética possui duas atividades quinásicas endógenas dependentes de 2° mensageiro, as quais são: a quinase dependente de cálcio e calmodulina (CaM quinase) e a quinase dependente de AMP cíclico (quinase A). Para o estudo da atividade fosfatásica foi utilizada uma curva de concentrações crescentes (0,05; 0,5 e 5 μM) de ácido ocadaico, um potente inibidor de fosfatases. Os resultados mostraram que a PP2A encontra-se associada à fração citoesquelética, defosforilando as proteínas da fração citoesquelética. As tarefas comportamentais estudadas neste trabalho alteraram a fosforilação in vítro de quatro fosfoproteínas constituintes da fração citoesquelética insolúvel em Triton X-100. A tarefa de habituação diminuiu a incorporação de ³²P-ATP in vitro na a tubulina e na GFAP, enquanto que a esquiva inibitória aumentou a fosforilação in vitro nas duas subunidades dos neurofilamentos (NF-M e NF-L). Nenhuma das duas tarefas teve efeito sobre a incorporação de ³²P na sinapsina 1. Além disso, o choque não foi capaz de alterar a fosforilação in vitro de nenhuma das fosfoproteínas estudadas. Com o objetivo de verificar se as alterações encontradas na incorporação de ³²P in vitro nestas proteínas, deviam-se a alterações na atividade quinásica ou fosfatásica, foram feitas as curvas de defosforilação, nas quais os sistemas foram incubados durante os seguintes tempos: 5, 10, 20 e 30 minutos. Nenhuma alteração foi detectada nas curvas de defosforilação de frações citoesqueléticas obtidas de ratos submetidos às tarefas comportamentais. Este resultado sugere que a alteração encontrada na incorporação de ³²P in vitro aos 5 minutos de incubação pode ser atribuída a alterações nas atividades quinásicas associadas a fração citoesquelética de hipocampo de ratos

Administration of a histone deacetylase inhibitor into the basolateral amygdala enhances memory consolidation, delays extinction, and increases hippocampal BDNF levels

Gene expression related to the formation and modification of memories is regulated epigenetically by chromatin remodeling through histone acetylation. Memory formation and extinction can be enhanced by treatment with inhibitors of histone deacetylases (HDACs). The basolateral amygdala (BLA) is a brain area critically involved in regulating memory for inhibitory avoidance (IA). However, previous studies have not examined the effects of HDAC inhibition in the amygdala on memory for IA. Here we show that infusion of an HDAC inhibitor (HDACi), trichostatin A (TSA), into the BLA, enhanced consolidation of IA memory in rats when given at 1.5, 3, or 6 h posttraining, but not when the drug was infused immediately after training. In addition, intra-BLA administration of TSA immediately after retrieval delayed extinction learning. Moreover, we show that intra-BLA TSA in rats given IA training increased the levels of brain-derived neurotrophic factor in the dorsal hippocampus, but not in the BLA itself. These findings reveal novel aspects of the regulation of fear memory by epigenetic mechanisms in the amygdala

Antiapoptotic effects of cannabidiol in an experimental model of cognitive decline induced by brain iron overload

Iron accumulation in the brain has been recognized as a common feature of both normal aging and neurodegenerative diseases. Cognitive dysfunction has been associated to iron excess in brain regions in humans. We have previously described that iron overload leads to severe memory deficits, including spatial, recognition, and emotional memory impairments in adult rats. In the present study we investigated the effects of neonatal iron overload on proteins involved in apoptotic pathways, such as Caspase 8, Caspase 9, Caspase 3, Cytochrome c, APAF1, and PARP in the hippocampus of adult rats, in an attempt to establish a causative role of iron excess on cell death in the nervous system, leading to memory dysfunction. Cannabidiol (CBD), the main non-psychotropic component of Cannabis sativa, was examined as a potential drug to reverse iron-induced effects on the parameters analyzed. Male rats received vehicle or iron carbonyl (30 mg/kg) from the 12th to the 14th postnatal days and were treated with vehicle or CBD (10 mg/kg) for 14 days in adulthood. Iron increased Caspase 9, Cytochrome c, APAF1, Caspase 3 and cleaved PARP, without affecting cleaved Caspase 8 levels. CBD reversed iron-induced effects, recovering apoptotic proteins Caspase 9, APAF1, Caspase 3 and cleaved PARP to the levels found in controls. These results suggest that iron can trigger cell death pathways by inducing intrinsic apoptotic proteins. The reversal of iron-induced effects by CBD indicates that it has neuroprotective potential through its anti-apoptotic action

Measurement of the t(t)over-bar production cross section in pp collisions at root s=7 TeV in dilepton final states containing a tau

The top quark pair production cross section is measured in dilepton events with one electron or muon, and one hadronically decaying tau lepton from the decay t (t) over bar -> (l nu(l))((sic)(h)nu((sic)))b (b) over bar, (l = e, mu). The data sample corresponds to an integrated luminosity of 2.0 fb(-1) for the electron channel and 2.2 fb(-1) for the muon channel, collected by the CMS detector at the LHC. This is the first measurement of the t (t) over bar cross section explicitly including tau leptons in proton- proton collisions at root s = 7 TeV. The measured value sigma(t (t) over bar) = 143 +/- 14(stat) +/- 22(syst) +/- 3(lumi) pb is consistent with the standard model predictions

Measurement of quark- and gluon-like jet fractions using jet charge in PbPb and pp collisions at 5.02 TeV

The momentum-weighted sum of the electric charges of particles inside a jet, known as jet charge, is sensitive to the electric charge of the particle initiating the parton shower. This paper presents jet charge distributions in root sNN = 5.02 TeV lead-lead (PbPb) and proton-proton (pp) collisions recorded with the CMS detector at the LHC. These data correspond to integrated luminosities of 404 mu b(-1)and 27.4 pb(-1)for PbPb and pp collisions, respectively. Leveraging the sensitivity of the jet charge to fundamental differences in the electric charges of quarks and gluons, the jet charge distributions from simulated events are used as templates to extract the quark- and gluon-like jet fractions from data. The modification of these jet fractions is examined by comparing pp and PbPb data as a function of the overlap of the colliding Pb nuclei (centrality). This measurement tests the color charge dependence of jet energy loss due to interactions with the quark-gluon plasma. No significant modification between different centrality classes and with respect to pp results is observed in the extracted quark- and gluon-like jet fractions.Peer reviewe

Two different properties of short- and long-term memory

Rats were trained in one-trial step-down inhibitory avoidance and tested 1.5–9 h later or 1–4 days later in order to evaluate short- and long-term memory respectively. No extinction was observed when the animals were tested repeatedly at 1.5, 3, 4.5 and 6 h; when they were tested repeatedly at 9, 24, 48, 72 and 96 h, there was partial extinction. Exposure to an open field for 2 min, 1 h after training did not affect retention scores of animals tested at 1.5 or 3 h, had a slight amnestic effect on groups tested at 4.5 or 6 h, and markedly reduced retention scores in animals tested at 9 or 24 h from training. Thus, there were two clear behavioural differences between memory measured in the first few hours or in the following few days, which suggests that both involve different mechanisms

Bombesin receptor regulation of emotional memory

Mammalian bombesin-like peptides neuromedin B (NMB) and gastrin-releasing peptide (GRP) act by activating NMB receptors (NMBR, BBl) and GRP receptors (GRPR,BB2), respectively. These two bombesin receptors are members of the G-protein-coupled receptor (GPCR) superfamily.In the brain, NMBR and GRPR are highly expressed in the brain areas involved in memory processing and emotional responses, such as the hippocampus and the amygdaloid nuclei. An increasing number of pharmacological and genetic studies in rodents indicate that NMBRs and GRPRs in brain regions including the dorsal hippocampus,the nucleus tractus solitarius, the basolateral amygdala,and cortical areas, regulate memory formation and expression, particularly for memories related to emotionally arousing tasks. GRPR signaling interacts with multiple protein kinase pathways as well as with other neurotransmitter,hormone, and growth factor systems in influencing memory formation. Together with evidence from human studies, the findings from rodent experiments suggest that bombesin receptors may be therapeutic targets in brain disorders involving memory dysfunction and anxiety

Effect of inhibitory avoidance training on [3H]-glutamate binding in the hippocampus and parietal cortex of rats

Glutamate receptors have been implicated in memory formation. The aim of the present study was to determine the effect of inhibitory avoidance training on specific [3H]-glutamate binding to membranes obtained from the hippocampus or parietal cortex of rats. Adult male Wistar rats were trained (0.5-mA footshock) in a step-down inhibitory avoidance task and were sacrificed 0, 5, 15 or 60 min after training. Hippocampus and parietal cortex were dissected and membranes were prepared and incubated with 350 nM [3H]-glutamate (N = 4-6 per group). Inhibitory avoidance training induced a 29% increase in glutamate binding in hippocampal membranes obtained from rats sacrificed at 5 min (P<0.01), but not at 0, 15, or 60 min after training, and did not affect glutamate binding in membranes obtained from the parietal cortex. These results are consistent with previous evidence for the involvement of glutamatergic synaptic modification in the hippocampus in the early steps of memory formation