Papers by Luciene Covolan
Os modelos experimentais da pilocarpina e do acido cainico, em diversos aspectos mimetizam a epil... more Os modelos experimentais da pilocarpina e do acido cainico, em diversos aspectos mimetizam a epilepsia de lobo temporal de humanos. Utilizando este dois modelos, decidimos avaliar a lesao neuronal nas diversas fases do processo epileptico. A identificacao de neuronios lesados apos status epilepticus (SE) ou crises espontaneas recorrentes (CERs) foi estudada predominantemente atraves da utilizacao de uma tecnica de impregnacao pela prata que permite a visualizacao de tais neuronios, corados em marrom, contra um fundo amarelo-caramelo, constituido pelos demais elementos (nao lesados) do tecido nervoso. O SE e consequentes CERs foram induzidos pela administracao sistemica de pilocarpina (320 mg/kg) ou de acido cainico (1O mg/kg). Parte do nosso objetivo foi avaliar a lesao neuronal frente a diferentes duracoes de SE induzido pela pilocarpina. Nossos resultados indicam que mesmo um SE de curtissima duracao determina lesao neuronal. Tambem avaliamos a lesao neuronal que sucede ao SE indu...
Aging and Disease, Aug 30, 2011
In the present study, we investigated the possible additive effects of epilepsy and aging on the ... more In the present study, we investigated the possible additive effects of epilepsy and aging on the expression of m1 muscarinic acetylcholine receptors (AChR) in the rat hippocampus. Young (3 months) and Aged (20 months) male, Wistar rats were treated with pilocarpine to induce status epilepticus (SE). Immunohistochemical procedure for m1 AChR detection was performed 2 months after pilocarpine-induced SE. In the CA1 pyramidal region m1 AChR staining was significantly decreased in aged epileptic animals when compared to young epileptic and aged control rats, indicating that the aging effect is worsened by the epileptic condition. However, the Nissl-stained cell analysis indicated that the number of pyramidal CA1 neurons was similarly reduced in both epileptic groups, young and aged animals. Therefore, our data suggest that the progressive reduction of m1 AChR expression in CA1 pyramidal cells of aged epileptic rats might bear relevance to the associated progressive cognitive impairment.
Apoptosis 24Â h after pilocarpine-induced status epilepticus. No significant differences were fou... more Apoptosis 24Â h after pilocarpine-induced status epilepticus. No significant differences were found in hippocampal caspase 3 activity when animals who developed pilocarpine-induced SE with or without DBS were compared to controls. (TIFF 94 kb)
ABSTRACT: In the present study, we investigated the possible additive effects of epilepsy and agi... more ABSTRACT: In the present study, we investigated the possible additive effects of epilepsy and aging on the expression of m1 muscarinic acetylcholine receptors (AChR) in the rat hippocampus. Young (3 months) and Aged (20 months) male, Wistar rats were treated with pilocarpine to induce status epilepticus (SE). Immunohistochemical procedure for m1 AChR detection was performed 2 months after pilocarpine-induced SE. In the CA1 pyramidal region m1 AChR staining was significantly decreased in aged epileptic animals when compared to young epileptic and aged control rats, indicating that the aging effect is worsened by the epileptic condition. However, the Nissl-stained cell analysis indicated that the number of pyramidal CA1 neurons was similarly reduced in both epileptic groups, young and aged animals. Therefore, our data suggest that the progressive reduction of m1 AChR expression in CA1 pyramidal cells of aged epileptic rats might bear relevance to the associated progressive cognitive i...
Brain Research Bulletin, 2019
In rat, we tested how 1 hour of ANT DBS affects the cell activity in the circuit of Papez. Redu... more In rat, we tested how 1 hour of ANT DBS affects the cell activity in the circuit of Papez. Reduction of cell excitability is demonstrated after high frequency ANT DBS using in vivo MRI. The results rely on the reduced uptake of manganese, a Ca 2+ competitor, by active cells. The reduced cell activity in the whole circuit of Papez may underlies the ANT DBS mechanism to reduce spontaneous seizures.
Translational Psychiatry, 2015
Chronic ventromedial prefrontal cortex (vmPFC) deep brain stimulation (DBS) improves depressive-l... more Chronic ventromedial prefrontal cortex (vmPFC) deep brain stimulation (DBS) improves depressive-like behaviour in rats via serotonergic and neurotrophic-related mechanisms. We hypothesise that, in addition to these substrates, DBS-induced increases in hippocampal neurogenesis may also be involved. Our results show that stress-induced behavioural deficits in the sucrose preference test, forced swim test, novelty-suppressed feeding test (NSFT) and elevated plus maze were countered by chronic vmPFC DBS. In addition, stressed rats receiving stimulation had significant increases in hippocampal neurogenesis, PFC and hippocampal brain-derived neurotrophic factor levels. To block neurogenesis, stressed animals given DBS were injected with temozolomide. Such treatment reversed the anxiolytic-like effect of stimulation in the NSFT without significantly affecting performance in other behavioural tests. Taken together, our findings suggest that neuroplastic changes, including neurogenesis, may be involved in specific anxiolytic effects of DBS without affecting its general antidepressant-like response.
Physical Biology, 2015
The excitability of neuronal networks is strongly modulated by changes in pH. The origin of these... more The excitability of neuronal networks is strongly modulated by changes in pH. The origin of these changes, however, is still under debate. The high complexity of neural systems justifies the use of computational simulation to investigate mechanisms that are possibly involved. Simulated neuronal activity includes non-synaptic epileptiform events (NEA) induced in hippocampal slices perfused with high-K(+) and zero-Ca(2+), therefore in the absence of the synaptic circuitry. A network of functional units composes the NEA model. Each functional unit represents one interface of neuronal/extracellular space/glial segments. Each interface contains transmembrane ionic transports, such as ionic channels, cotransporters, exchangers and pumps. Neuronal interconnections are mediated by gap-junctions, electric field effects and extracellular ionic fluctuations modulated by extracellular electrodiffusion. Mechanisms investigated are those that change intracellular and extracellular ionic concentrations and are able to affect [H(+)]. Our simulations suggest that the intense fluctuations in intra and extracellular concentrations of Na(+), K(+) and Cl(-) that accompany NEA are able to affect the combined action of the Na(+)/H(+) exchanger (NHE), [HCO(-)(3)]/Cl(-) exchanger (HCE), H(+) pump and the catalytic activity of intra and extracellular carbonic anhydrase. Cellular volume changes and extracellular electrodiffusion are responsible for modulating pH.
Journal of Neuroinflammation, 2015
Background: Status epilepticus (SE) is a severe condition that may lead to hippocampal cell loss ... more Background: Status epilepticus (SE) is a severe condition that may lead to hippocampal cell loss and epileptogenesis. Some of the mechanisms associated with SE-induced cell death are excitotoxicity, neuroinflammation, and apoptosis. Objective: The objective of the present study is to test the hypothesis that DBS has anti-inflammatory and antiapoptotic effects when applied during SE. Methods: Rats undergoing pilocarpine-induced SE were treated with anterior thalamic nucleus (AN) deep brain stimulation (DBS). Inflammatory changes and caspase 3 activity were measured within 1 week of treatment. Results: In pilocarpine-treated rats, DBS countered the significant increase in hippocampal caspase 3 activity and interleukin-6 (IL-6) levels that follows SE but had no effect on tumor necrosis factor α (TNFα). Conclusions: DBS has anti-inflammatory and antiapoptotic effects when given to animals undergoing status.
Neurobiology of Learning and Memory, 2015
Prematurely-born infants are exposed to multiple invasive procedures while in the intensive care ... more Prematurely-born infants are exposed to multiple invasive procedures while in the intensive care unit. Newborn rats and humans have similar behavioral responses to noxious stimulation. Previous studies have shown that early noxious stimuli may alter dentate gyrus neurogenesis and the behavioral repertoire of adult rats. We evaluated the late effects of noxious stimulation administered during different phases of development on two spatial memory tests; object recognition (OR) and Morris water maze (WM) tests. Noxious stimulation was induced by an intra-plantar injection of complete Freund's adjuvant (CFA) on postnatal (P) day 1 (group P1) or 8 (P8). Control animals were not stimulated. Behavioral tests were conducted on P60 in both male and female animals. In the WM, three domains were evaluated: acquisition, probe trial performance and reversal re-acquisition. The number of Nissl stained cells in the dentate granule cell layer was assessed by stereological counting. The OR test revealed that P1 male rats had poor long-term memory compared to the control and P8 groups. In the WM, no short-or longterm memory differences were detected between early postnatal-stimulated male and female rats and their respective controls. However, the ability to find the hidden platform in a new position was reduced in P1 male rats. The number of dentate granule cells in P8 males was higher than in all other groups. This study demonstrates that noxious stimulation on P1 results in spatial learning deficits in male animals, but does not disrupt the development of the hippocampus-dependent strategies of learning and memory.
Journal of Stem Cell Research & Therapy, 2014
A considerable number of epileptic patients had become resistant to antiepileptic drugs, justifyi... more A considerable number of epileptic patients had become resistant to antiepileptic drugs, justifying the need for development of new therapeutic strategies to treat epilepsy. The use of mesenchymal stem cells is an innovative and accessible strategy for the treatment of neuronal disorders, due to their involvement in immunoregulatory mechanisms, trophic and anti-apoptotic action. Objective: Based on this evidence, we evaluated the protective effect of mesenchymal cells from adipose tissue (MCAT) by behavioral and inflammatory responses against convulsive seizure induced by maximum electroconvulsive shock (MES). Methods: MCAT cells were transplanted into the hippocampus of adult male mice, and ten days after the transplantation MES stimulation was applied to induce a generalized tonic-clonic seizure. To evaluate the anticonvulsant activity of MCAT cells, we evaluated the parameters involved with: protection and reduction in the duration of tonic phase, reduction in the mortality rate, and alteration in the hippocampal gene expression of IL-1beta, IL-6, IL-4, IL-10, caspase-1, iNOS and TNFα. Results: MCAT cells transplanted into the hippocampus altered the convulsive threshold, showed anticonvulsant effect by protecting from tonic seizures and mortality and reduced the hippocampal expression of transcripts related to inflammatory response such as IL-1beta, IL-6, caspase-1 and iNOS and increased the level of anti-inflammatory interleukin IL-4. Conclusion: The anticonvulsant effects of the MCAT cells on acute convulsive seizure may be related to inhibitory factors and immunomodulatory mechanisms assigned to mesenchymal cells in the hippocampus. These anticonvulsants mechanisms of MCAT cells bring strong therapeutic implications for the control of epileptic seizures.
Frontiers in Neurology, 2015
Magnetic resonance imaging (MRI) is an excellent non-invasive tool to investigate biological syst... more Magnetic resonance imaging (MRI) is an excellent non-invasive tool to investigate biological systems. The administration of the paramagnetic divalent ion manganese (Mn 2+) enhances MRI contrast in vivo. Due to similarities between Mn 2+ and calcium (Ca 2+), the premise of manganese-enhanced MRI (MEMRI) is that the former may enter neurons and other excitable cells through voltage-gated Ca 2+ channels. As such, MEMRI has been used to trace neuronal pathways, define morphological boundaries, and study connectivity in morphological and functional imaging studies. In this article, we provide a brief overview of MEMRI and discuss recently published data to illustrate the usefulness of this method, particularly in animal models.
Epilepsy Research, 1996
It is still a question of much debate whether single epileptic seizures can cause cell loss. Desp... more It is still a question of much debate whether single epileptic seizures can cause cell loss. Despite the clinical impression that epilepsy in general is a progressive disorder, experimental evidence is not conclusive on this point. Recently, it has been shown that electrically-induced afterdischarges of less than 2 min may induce structural impairments in neurons. Here we evaluated whether spontaneous seizures would lead to similar impairments. Chronic spontaneous recurrent seizures were induced with pilocarpine (320 mg/kg, i.p.). Animals were sacrificed from 1 to 6 h either after single or multiple seizures. A Golgi-like sensitive silver-impregnation procedure was used to reveal injured neurons. Silver-impregnated dark neurons were never found in control animals nor in epileptic animals that had no behavioral seizures in the 8 h prior to sacrifice. After spontaneous seizures (injured) dark neurons were mostly interneurons and were present in hippocampus (CA1 stratum radiatum), amygdala, piriform cortex and other limbic structures. Animals with multiple seizures had a higher number of dark cells than animals with single seizures. Our findings suggest that even single generalized spontaneous tonic-clonic seizures can induce long-lasting morphological changes. Our results favor the idea that epilepsy is a progressive disorder where one seizure begets the next.
Anais da Academia Brasileira de Ciências, 2000
Dentate granule cells are generally considered to be relatively resistant to excitotoxicity and h... more Dentate granule cells are generally considered to be relatively resistant to excitotoxicity and have been associated to robust synaptogenesis after neuronal damage. Synaptic reorganization of dentate granule cell axons, the mossy fibers, has been suggested to be relevant for hyperexcitability in human temporal lobe epilepsy and animal models. A recent hypothesis has suggested that mossy fiber sprouting is dependent on newly formed dentate granule cells. However, we have recently demonstrated that cycloheximide (CHX) can block the mossy fiber sprouting that would be otherwise induced by different epileptogenic agents and do not interfere with epileptogenesis in those models. Here, we investigated cell damage and neurogenesis in the dentate gyrus of pilocarpine-or kainate-treated animals with or without the co-administration of CHX. Dentate granule cells were highly vulnerable to pilocarpine induced-status epilepticus (SE), but hardly damaged by kainate induced-SE. CHX-pretreatment markedly reduced the number of injured neurons after pilocarpine-induced SE. Induction of SE dramatically increased the mitotic rate of KA and KA + CHX treated animals. Induction of SE in animals injected with pilocarpine alone led to increases of between two to sevenfold in the mitotic rate of dentate granule cells as compared to increases of between five and thirtyfold for pilocarpine+CHX animals. These observations indicate that in presence of cycloheximide the increase of the mitotic rate after pilocarpine-induced SE may be due to protection of a vulnerable precursor cell population that would otherwise degenerate. We further suggest that the mossy fiber sprouting and neurogenesis of granule cells are not necessarily related events.-(September 14, 1999) .
Stress, 2020
Most chronic stress protocols are too laborious or do not abide by the two main characteristics o... more Most chronic stress protocols are too laborious or do not abide by the two main characteristics of the stress concept: uncontrollability and unpredictability. The goal of this study was to establish a simple and reliable model of chronic stress, while maintaining the main features of the concept. Animals were exposed to chronic movement restraint with variable duration (2, 4 or 6 h, in an unpredictable schedule) for 3 weeks and assessed in several physiological and behavioral readouts known to reflect chronic stress states. Body weight, levels of plasma corticosterone, hippocampal pro-and anti-inflammatory cytokines, anxiety-like (novelty suppressed feeding and elevated plus maze) and motivated behaviors (sucrose negative contrast test and forced swim test) were evaluated three days after the end of the chronic protocol. Stressed animals had a lower body weight gain, higher levels of cytokines in the hippocampus, reduced suppression of a low concentration sucrose solution and increased immobility in the forced swim test. Based on these data, we suggest that chronic movement restraint with variable duration may be a suitable and simple protocol for the study of changes induced by chronic stress and for the testing of possible treatments relevant to psychiatry.
Neurobiology of Disease, Aug 13, 2014
Recent studies in patients with treatment-resistant depression have shown similar results with th... more Recent studies in patients with treatment-resistant depression have shown similar results with the use of deep brain stimulation (DBS) in the subcallosal cingulate gyrus (SCG), ventral capsule/ventral striatum (VC/VS) and nucleus accumbens (Acb). As these brain regions are interconnected, one hypothesis is that by stimulating these targets one would just be influencing different relays in the same circuitry. We investigate behavioral, immediate early gene expression, and functional connectivity changes in rats given DBS in homologous regions, namely the ventromedial prefrontal cortex (vmPFC), white matter fibers of the frontal region (WMF) and nucleus accumbens. We found that DBS delivered to the vmPFC, Acb but not WMF induced significant antidepressant-like effects in the FST (31%, 44%, and 17% reduction in immobility compared to controls). Despite these findings, stimulation applied to these three targets induced distinct patterns of regional activity and functional connectivity. ...
Magnetic resonance images are useful in the study of experimental models of temporal lobe epileps... more Magnetic resonance images are useful in the study of experimental models of temporal lobe epilepsy. The manganese-enhanced MRI (MEMRI) technique is of interest since it combines the effects caused by manganese on the increased contrast in activated cell populations, when competing with calcium in synaptic transmission. Thus, the purpose of this study was to investigate the temporal evolution of the contrast related to manganese in the acute phase of temporal lobe epilepsy induced by systemic pilocarpine and compare it to the expression of the c-Fos protein. During this phase, the intensity of the MEMRI signal was analyzed at three different time points (5, 15 or 30 minutes) after the onset of status epilepticus (SE). The group that was maintained in status epilepticus for 30 minutes showed a decrease in intensity of the signal in CA1 and the dentate gyrus (DG). There were no differences between the control group and the other groups treated with pilocarpine. The expression of the pr...
European Journal of Neuroscience
Although it is known that nociceptive stimulation in the first postnatal week in rats is useful t... more Although it is known that nociceptive stimulation in the first postnatal week in rats is useful to model preterm pain, resulting in activation of specific brain areas, as assessed in vivo using manganese‐enhanced magnetic resonance imaging (MEMRI), little is known about its long‐term effects and sex specificity. Here we aimed to investigate whether inflammatory pain induced in male and female adult rats modify the pattern of brain activation between animals subjected or not to neonatal pain. For this, Complete Freund's adjuvant (CFA) was injected into the left hind paw of rat pups on postnatal day 1 (P1) or P8 to induce inflammatory response. During adulthood, CFA‐treated and control animals were injected with CFA 1 hr prior MRI. MEMRI has the ability to enhance the contrast of selective brain structures in response to a specific stimulus, as the pain. MEMRI responses were consistent with activation of nociceptive pathways and these responses were reduced in animals treated with CFA on P1, but increased in animals treated on P8, mainly in the female group. In agreement, P8 female group showed exacerbated responses in the thermal nociceptive test. Using MEMRI, we conclude that the natural ability of adult rats to recognize and react to pain exposition is modified by neonatal painful exposition, mainly among females.
The dopaminergic system is implicated in several cognitive processes including memory, attention ... more The dopaminergic system is implicated in several cognitive processes including memory, attention and executive functions. This study was a double-blind, placebo-randomized trial designed to investigate the effect of dopamine D2receptor blockade on episodic and working memory and particularly the relationship between executive functions, working memory capacity and long-term memory (LTM). Subjects ingested a single oral dose (4 mg) of haloperidol, a dopamine D2receptor antagonist or placebo. Multiple linear regression using generalized linear models and a generalized estimating equation were used for statistical analyses. The results demonstrated that haloperidol impaired episodic memory (free recall of words and prose recall), working memory capacity-WMC (operation span task-OSPAN) and highly demanding executive functions (random number generation - RNG). In addition, it demonstrated that despite the large impairment in the RNG task performance in the haloperidol group, it did not a...
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Papers by Luciene Covolan