Guilherme Shigueto Vilar Higa

University of São Paulo | USP · Institute of Chemistry (IQ)

Neuronal synchronization is important for communication between brain regions and plays a key role in learning. However, changes in connectivity can lead to hyper-synchronized states related to epileptic seizures that occur intermittently with asynchronous states. The activity-regulated cytoskeleton-associated protein (ARC) is related to synaptic a...

Important functions of the prefrontal cortex (PFC) are established during early life, when neurons exhibit enhanced synaptic plasticity and synaptogenesis. This developmental stage drives the organization of cortical connectivity, responsible for establishing behavioral patterns. Serotonin (5-HT) emerges among the most significant factors that modu...

The use of antidepressants during pregnancy benefits the mother's well-being, but the effects of such substances on neurodevelopment remain poorly understood. Moreover, the consequences of early exposure to antidepressants may not be immediately apparent at birth. In utero exposure to selective serotonin reuptake inhibitors (SSRIs) has been related...

It is well established that temporal lobe epilepsy (TLE) is often related to oxidative stress and neuroinflammation. Both processes subserve alterations observed in epileptogenesis and ultimately involve distinct classes of cells, including astrocytes, microglia, and specific neural subtypes. For this reason, molecules associated with oxidative str...

Neurons in the nervous system are submitted to distinct sources of noise, such as ionic-channel and synaptic noise, which introduces variability in their responses to repeated presentations of identical stimuli. This motivates the use of stochastic models to describe neuronal behavior. In this work, we characterize an intrinsically stochastic neuro...

Neurons in the nervous system are submitted to distinct sources of noise, such as ionic-channel and synaptic noise, which introduces variability in their responses to repeated presentations of identical stimuli. This motivates the use of stochastic models to describe neuronal behavior. In this work, we characterize an intrinsically stochastic neuro...

Depression is a prevalent disease in modern society, and has been linked to stressful events at early ages. Women are more susceptible to depression, and the neural basis for this are still under investigation. Serotonin is known to be involved in depression, and a decrease in 5HT1A expression is observed on temporal and cortical areas in both men...

Status epilepticus (SE) is a clinical emergency that can lead to the development of temporal lobe epilepsy (TLE). The development and maintenance of spontaneous seizures in TLE are linked to calcium (Ca+2)-dependent processes such as neuronal cell loss and pathological synaptic plasticity. It has been shown that SE produces an increase in ryanodine...

Self-sustained activity in the brain is observed in the absence of external stimuli and contributes to signal propagation, neural coding, and dynamic stability. It also plays an important role in cognitive processes. In this work, by means of studying intracellular recordings from CA1 neurons in rats and results from numerical simulations, we demo...

The brain can display self-sustained activity (SSA), which is the persistent firing of neurons in the absence of external stimuli. This spontaneous activity shows low neuronal firing rates and is observed in diverse in vitro and in vivo situations. In this work, we study the influence of excitatory/inhibitory balance, connection density, and networ...

Metaplasticity is the regulation of synaptic plasticity based on the history of previous synaptic activation. This concept was formulated after observing that synaptic changes in the visual cortex are not fixed, but dynamic, and dependent on the history of visual information flux. In visual cortical neurons, sustained synaptic stimulation activate...

Epilepsy is a disorder of the brain characterized by the predisposition to generate recurrent unprovoked seizures, which involves reshaping of neuronal circuitries based on intense neuronal activity. In this review, we first detailed the regulation of plasticity-associated genes, such as ARC, GAP-43, PSD-95, synapsin, and synaptophysin. Indeed, res...

The Zika virus (ZIKV) outbreak that occurred in the northeast of Brazil in 2015 led to alarming numbers of babies born with microcephaly in this region. Since then, several studies have evaluated the relationship between ZIKV infection and development of the malformation although the specific mechanistic interaction between ZIKV and human physiolog...

Anoxia is one of the most prevalent causes of neonatal morbidity and mortality, especially in preterm neonates, constituting an important public health problem due to permanent neurological sequelae observed in patients. Oxygen deprivation triggers a series of simultaneous cascades, culminating in cell death mainly located in more vulnerable metabo...

Epileptogenesis in the temporal lobe elicits regulation of gene expression and protein translation, leading to reorganization of neuronal networks. In this process, miRNAs were described as being regulated in a cell-specific manner, although mechanistics of miRNAs activity are poorly understood. The specificity of miRNAs on their target genes depen...

The toxicologic effects of copper (Cu) on tumor cells have been studied during the past decades, and it is suggested that Cu ion may trigger antiproliferative effects in vitro . However, in normal cells the toxicologic effects of high exposures of free Cu are not well understood. In this work, Cu uptake, the expression of genes associated with cell...

Como a mente funciona e qual a ligação do pensamento e a atividade biológica do encéfalo humano? Redes Neurais interconectadas com computadores simulam o cérebro humano. É sabido que o ser humano, desde a antiguidade, tem observado e filosofado a respeito da natureza, dos ciclos e demais fatores pertinentes à ciência que interferem em nossas vidas....

Em praticamente todas as células eucarióticas são encontradas diferenças de cargas elétricas entre as faces de suas membranas, sejam estas delimitadoras de organelas como a mitocôndria, seja a própria membrana celular. A diferença de potencial elétrico, também conhecida como potencial de membrana, geralmente apresenta valor negativo na face interna...

Gap junction (GJ) channels have been recognized as an important mechanism for synchronizing neuronal networks. Herein, we investigated the participation of GJ channels in the pilocarpine-induced status epilepticus (SE) by analyzing electrophysiological activity following the blockade of connexins (Cx)-mediated communication. In addition, we examine...

MicroRNAs (miRNAs) are short nucleotides sequences that regulate the expression of genes in different eukaryotic cell types. A tremendous amount of knowledge on miRNAs has rapidly accumulated over the last few years, revealing the growing interest in this field of research. On the other hand, clarifying the physiological regulation of gene expressi...

The control of gene expression by miRNAs has been widely investigated in different species and cell types. Following a probabilistic rather than a deterministic regimen, the action of these short nucleotide sequences on specific genes depends on intracellular concentration, which in turn reflects the balance between biosynthesis and degradation. Re...

In this study, we describe a simple and reliable method to study neuroprotective effects in living and organized neural tissue. This method, which was based on retinal explants for in vivo focal lesions, was conceived as a collection of modular procedures, which can be customized for particular demands. With this model, it is possible to combine im...

In the nervous system, control of gene expression by microRNAs (miRNAs) has been investigated in fundamental processes, such as development and adaptation to ambient demands. The action of these short nucleotide sequences on specific genes depends on intracellular concentration, which in turn reflects the balance of biosynthesis and degradation. Wh...

Accruing evidence indicates that connexin (Cx) channels in the gap junctions (GJ) are involved in neurodegeneration after injury. However, studies using KO animal models endowed apparently contradictory results in relation to the role of coupling in neuroprotection. We analyzed the role of Cx-mediated communication in a focal lesion induced by mech...

Electrical coupling provided by connexins (Cx) in gap junctions (GJ) plays important roles in both the developing and the mature retina. In mammalian nocturnal species, Cx36 is an essential component in the rod pathway, the retinal circuit specialized for night, scotopic vision. Here, we report the expression of Cx36 in a species (Gallus gallus) th...