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Introduction: The close relationship between inflammatory processes and epileptic seizures is already known, although the exact pathophysiological mechanism is unclear. In this study, the anticonvulsant capacity of piroxicam, an anti-inflammatory drug, was evaluated. A rat pentylenetetrazole kindling model was used.Methods: Male Wistar rats, 8-9 weeks old, received piroxicam (0.15 and 0.30 mg/kg), diazepam (2 mg/kg) or saline for 14 days, and PTZ, on alternate days. Intraperitoneal was chosen as the route of administration. The intensity of epileptic seizures was assessed using a modified Racine scale. The open field test and object recognition analysis were performed at the beginning of the study to ensure the safety of the drugs used. At the end of the protocol, the animals were euthanized to measure the levels of inflammatory (TNF-a and IL-6) and anti-inflammatory (IL-10) cytokines in the cortex, hippocampus, and serum.Results:There were no changes in the open field test and object recognition analysis. Piroxicam was found to decrease Racine scale scores at both concentrations. The reported values for IL-6 levels remained steady in all structures, whereas the TNF-alpha level in the cortex was higher in animals treated with piroxicam than in the saline and diazepam subjects. Finally, animals treated with the anti-inflammatory drug presented reduced IL-10 levels in the cortex and hippocampus.onclusions: Using inflammation as a guiding principle, the anticonvulsant effect of PIRO could be associated with the hippocampal circuits, since this structure showed no increase in inflammatory cytokines.
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Anticonvulsivantes , Modelos Animais de Doenças , Excitação Neurológica , Piroxicam , Ratos Wistar , Animais , Piroxicam/farmacologia , Masculino , Excitação Neurológica/efeitos dos fármacos , Anticonvulsivantes/farmacologia , Ratos , Pentilenotetrazol , Convulsões/tratamento farmacológico , Citocinas/metabolismo , Diazepam/farmacologia , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Anti-Inflamatórios não Esteroides/farmacologia , Anti-Inflamatórios não Esteroides/administração & dosagem , Relação Dose-Resposta a Droga , Epilepsia/tratamento farmacológicoRESUMO
Epilepsy is a chronic condition characterized by recurrent spontaneous seizures. The interaction between astrocytes and neurons has been suggested to play a role in the abnormal neuronal activity observed in epilepsy. However, the exact way astrocytes influence neuronal activity in the epileptogenic brain remains unclear. Here, using the PTZ-induced kindling mouse model, we evaluated the interaction between astrocyte and synaptic function by measuring astrocytic Ca2+ activity, neuronal excitability, and the excitatory/inhibitory balance in the hippocampus. Compared to control mice, hippocampal slices from PTZ-kindled mice displayed an increase in glial fibrillary acidic protein (GFAP) levels and an abnormal pattern of intracellular Ca2+-oscillations, characterized by an increased frequency of prolonged spontaneous transients. PTZ-kindled hippocampal slices also showed an increase in the E/I ratio towards excitation, likely resulting from an augmented release probability of excitatory inputs without affecting inhibitory synapses. Notably, the alterations in the release probability seen in PTZ-kindled slices can be recovered by reducing astrocyte hyperactivity with the reversible toxin fluorocitrate. This suggests that astroglial hyper-reactivity enhances excitatory synaptic transmission, thereby impacting the E/I balance in the hippocampus. Altogether, our findings support the notion that abnormal astrocyte-neuron interactions are pivotal mechanisms in epileptogenesis.
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Epilepsia , Excitação Neurológica , Camundongos , Animais , Pentilenotetrazol/efeitos adversos , Astrócitos/metabolismo , Epilepsia/metabolismo , Excitação Neurológica/metabolismo , Convulsões/metabolismo , Hipocampo/metabolismoRESUMO
Recent evidence suggests that P-glycoprotein (P-gp) overexpression mediates hyperexcitability and is associated with epileptogenesis. Transcranial focal electrical stimulation (TFS) delays epileptogenesis and inhibits P-gp overexpression after a generalized seizure. Here, first we measured P-gp expression during epileptogenesis and second, we assessed if TFS antiepileptogenic effect was related with P-gp overexpression avoidance. Male Wistar rats were implanted in right basolateral amygdala and stimulated daily for electrical amygdala kindling (EAK), P-gp expression was assessed during epileptogenesis in relevant brain areas. Stage I group showed 85% increase in P-gp in ipsilateral hippocampus (p < 0.001). Stage III group presented 58% and 57% increase in P-gp in both hippocampi (p < 0.05). Kindled group had 92% and 90% increase in P-gp in both hippocampi (p < 0.01), and 93% and 143% increase in both neocortices (p < 0.01). For the second experiment, TFS was administrated daily after each EAK stimulation for 20 days and P-gp concentration was assessed. No changes were found in the TFS group (p > 0.05). Kindled group showed 132% and 138% increase in P-gp in both hippocampi (p < 0.001) and 51% and 92% increase in both cortices (p < 0.001). Kindled + TFS group presented no changes (p > 0.05). Our experiments revealed that progression of EAK is associated with increased P-gp expression. These changes are structure-specific and dependent on seizure severity. EAK-induced P-gp overexpression would be associated with neuronal hyperexcitability and thus, epileptogenesis. P-gp could be a novel therapeutical target to avoid epileptogenesis. In accordance with this, TFS inhibited P-gp overexpression and interfered with EAK. An important limitation of the present study is that P-gp neuronal expression was not evaluated under the different experimental conditions. Future studies should be carried out to determine P-gp neuronal overexpression in hyperexcitable networks during epileptogenesis. The TFS-induced lessening of P-gp overexpression could be a novel therapeutical strategy to avoid epileptogenesis in high-risk patients.
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BACKGROUND: Deep brain stimulation (DBS) of the anterior nucleus of the thalamus (ANT) is an emerging therapy to provide seizure control in patients with refractory epilepsy, although its therapeutic mechanisms remain elusive. OBJECTIVE: We tested the hypothesis that ANT-DBS might interfere with the kindling process using three experimental groups: PTZ, DBS-ON and DBS-OFF. METHODS: 79 male rats were used in two experiments and exposed to chemical kindling with pentylenetetrazole (PTZ, 30 mg/kg i.p.), delivered three times a week for a total of 18 kindling days (KD). These animals were divided into two sets of three groups: PTZ (n = 26), DBS-ON (n = 28) and DBS-OFF (n = 25). ANT-DBS (130 Hz, 90 µs, and 200 µA) was paired with PTZ injections, while DBS-OFF group, although implanted remained unstimulated. After KD 18, the first set of PTZ-treated animals and an additional group of 11 naïve rats were euthanized for brain extraction to study adenosine kinase (ADK) expression. To observe possible long-lasting effects of ANT stimulation, the second set of animals underwent a 1-week treatment and stimulation-free period after KD 18 before a final PTZ challenge. RESULTS: ANT-DBS markedly attenuated kindling progression in the DBS-ON group, which developed seizure scores of 2.4 on KD 13, whereas equivalent seizure scores were reached in the DBS-OFF and PTZ groups as early as KD5 and KD6, respectively. The incidence of animals with generalized seizures following 3 consecutive PTZ injections was 94%, 74% and 21% in PTZ, DBS-OFF and DBS-ON groups, respectively. Seizure scores triggered by a PTZ challenge one week after cessation of stimulation revealed lasting suppression of seizure scores in the DBS-ON group (2.7 ± 0.2) compared to scores of 4.5 ± 0.1 for the PTZ group and 4.3 ± 0.1 for the DBS-OFF group (P = 0.0001). While ANT-DBS protected hippocampal cells, the expression of ADK was decreased in the DBS-ON group compared to both PTZ (P < 0.01) and naïve animals (P < 0.01). CONCLUSIONS: Our study demonstrates that ANT-DBS interferes with the kindling process and reduced seizure activity was maintained after a stimulation free period of one week. Our findings suggest that ANT-DBS might have additional therapeutic benefits to attenuate seizure progression in epilepsy.
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Núcleos Anteriores do Tálamo , Estimulação Encefálica Profunda , Excitação Neurológica , Adenosina Quinase/metabolismo , Adenosina Quinase/farmacologia , Animais , Excitação Neurológica/fisiologia , Masculino , Pentilenotetrazol , Ratos , Convulsões/induzido quimicamente , Convulsões/metabolismo , Convulsões/terapiaRESUMO
Epilepsy is the most common neurological condition worldwide and is largely associated with memory impairment, both in human as well as animal models. Furthermore, differences in seizure onset and severity have already been observed between the sexes. The induction of epilepsy through multiple systemic injections of pentylenetetrazole (PTZ), a protocol known as chemical kindling, is a well-established tool for studies regarding epileptogenesis, as well as the efficacy of antiseizure medication. The aim of this study was to compare possible sex-related differences in seizure severity, memory, neuronal damage as well as the effects of the estrous cycle on seizure severity. Male (nâ¯=â¯10) and Female (nâ¯=â¯11) animals received 30â¯mg/kg i.p. injections three days a week for 6â¯weeks and, after the last application, were tested for short and long-term memory. Control, Male (nâ¯=â¯8) and Female (nâ¯=â¯5) groups did not receive PTZ injections. Although PTZ did not promote important changes into the estrous cycle phases throughout the entire experiment, female animals presented lower seizure scores but had both short and long-term memory impairments associated with cell loss in the hippocampus and anterior cingulate area. Male rats presented higher seizure scores associated with pronounced cell loss, but only long-term memory deficits. Our results demonstrate that the PTZ kindling protocol results in higher seizure scores with increased vulnerability in male rats, but female rats displayed more intense memory deficits.
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Excitação Neurológica , Pentilenotetrazol , Animais , Feminino , Humanos , Masculino , Transtornos da Memória/induzido quimicamente , Pentilenotetrazol/toxicidade , Ratos , Ratos Wistar , Memória EspacialRESUMO
Objetivo: Describir la fisiopatología de las manifestaciones neurológicas por infección con COVID-19. Método: Revisión sistemática de 22 articulos relacionados con el objetivo de investigación, procedentes de la base de datos PubMed. Resultados: Dentro de las manifestaciones clínicas del COVID-19 en el SNP, se hallaron en los reportes clínicos, disminución parcial de la capacidad de percibir olores, denominada hiposmia y reducción total de la misma, denominada anosmia, así mismo otros pacientes o en los mismos que reportaron el anterior síntoma, refirieron haber perdido la capacidad para distinguir sabores, así la hipogeusia, y la ageusia también iban de la mano con la hiposmia. Conclusión: Se ha demostrado que el SARS-CoV-2 tiene un tropismo por las células del sistema nervioso, lo cual significaría una afectación al sistema nervioso que demás puede ser afectado por la tormenta de citoquinas, que a su vez pueden desarrollar un daño directo al parénquima neuronal.
Objective: To describe the pathophysiology of neurological manifestations due to infection with COVID-19. Methods: Systematic review of 22 articles related to the research objective, from the PubMed database. Results: Among the clinical manifestations of COVID-19 in the PNS, in the clinical reports, partial reduction of the ability to perceive odors, called hyposmia and total reduction of the same, called anosmia, as well as other patients or in the same patients who reported the previous symptom, reported having lost the ability to distinguish flavors, thus hypogeusia and ageusia also went hand in hand with hyposmia. Conclusion: SARS-CoV-2 has been shown to have a tropism for nervous system cells, which would mean an affectation to the nervous system that can be further affected by the cytokine storm, which in turn can develop direct damage to the neuronal parenchyma.
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The present study evaluated the protective effect of 1-(7-chloroquinolin-4-yl)-5-methyl-N-phenyl-1H-1,2,3-triazole-4-carboxamide (QTCA-1) on seizure severity, oxidative stress, and memory disorder in a pentylenetetrazole (PTZ)-kindling model in mice. Male Swiss mice were treated with QTCA-1 (10 mg/kg, intragastrically (i.g.)) or phenobarbital (PHEN) (10 mg/kg; i.g.), 30 min before the injection of PTZ (35 mg/kg, intraperitoneally (i.p.)). Treatments with QCTA-1 or PHEN and PTZ were performed once every 48 h (on the 1st, 3rd, 5th, 7th, 9th and 11th days). After each PTZ injection, the animals were observed for 30 min to assess the stage of seizure intensity. Behavioral parameters were evaluated from the 12th day until the 16th day of the experimental protocol. On the 16th day, mice were euthanized, and the cerebral cortex and hippocampus of mice were removed to determine the thiobarbituric acid reactive species (TBARS) and reactive species (RS) levels, and superoxide dismutase (SOD), Na+/K+-ATPase and acetylcholinesterase (AChE) activities. Our results demonstrated that QTCA-1 significantly decreased the seizure stage score in PTZ-kindled mice. QCTA-1 protected against memory impairment induced by PTZ. QTCA-1 normalized oxidative stress and Na+/K+-ATPase activity in the cerebral structures of PTZ-kindled mice. The effect of QTCA-1 treatment was similar to the positive control used in this study (PHEN). AChE activity did not change in the cerebral structures in PTZ- kindling mice. In conclusion, QCTA-1 may be a promising tool for the treatment of epileptogenesis and epilepsy-associated comorbidity (memory impairment). QCTA-1 to prevent these alterations may involve the reduction of oxidative stress and normalization of Na+/K+-ATPase activity.
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Excitação Neurológica , Pentilenotetrazol , Acetilcolinesterase/metabolismo , Animais , Anticonvulsivantes/farmacologia , Antioxidantes/farmacologia , Encéfalo/metabolismo , Comorbidade , Masculino , Camundongos , Estresse Oxidativo , Pentilenotetrazol/farmacologia , QuinolinasRESUMO
Epilepsies are neurological disorders characterized by chronic seizures and their related neuropsychiatric comorbidities, such as anxiety. The Transient Receptor Potential Vanilloid type-1 (TRPV1) channel has been implicated in the modulation of seizures and anxiety-like behaviors in preclinical models. Here, we investigated the impact of chronic epileptic seizures in anxiety-like behavior and TRPV1 channels expression in a genetic model of epilepsy, the Wistar Audiogenic Rat (WAR) strain. WARs were submitted to audiogenic kindling (AK), a preclinical model of temporal lobe epilepsy (TLE) and behavioral tests were performed in the open-field (OF), and light-dark box (LDB) tests 24 h after AK. WARs displayed increased anxiety-like behavior and TRPV1R expression in the hippocampal CA1 area and basolateral amygdala nucleus (BLA) when compared to control Wistar rats. Chronic seizures increased anxiety-like behaviors and TRPV1 and FosB expression in limbic and brainstem structures involved with epilepsy and anxiety comorbidity, such as the hippocampus, superior colliculus, and periaqueductal gray matter. Therefore, these results highlight previously unrecognized alterations in TRPV1 expression in brain structures involved with TLE and anxiogenic-like behaviors in a genetic model of epilepsy, the WAR strain, supporting an important role of TRPV1 in the modulation of neurological disorders and associated neuropsychiatric comorbidities.
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Abstract Recent studies suggested that safranal exerts anticonvulsant properties. The present study aimed to investigate the effect of safranal on epileptic activities in the amygdala electrical kindling model in male rats. Animals were implanted with a recording electrode on the skull and a tripolar in the amygdala. After 10 days of recovery, the afterdischarge (AD) threshold of each animal was determined and stimulated once daily the AD threshold for full kindling development. Then, parameters including afterdischarge duration (ADD), stage 4 latency (S4L), stage 5 duration (S5D), and stimulation threshold were determined before and after injection of safranal (0.05, 0.1, 0.2 ml/ kg; i.p). While the dose of 0.05 ml/kg had no significant effect, the dose of 0.1 ml/kg increased the AD threshold as well as S4L and decreased the S5D (P<0.05). Injection of 0.2 ml/kg of the safranal significantly decreased the ADD and S5D (P<0.05) and 83.3% of animals had no stage 4 and stage 5 of kindling (P<0.001). Based on the obtained data safranal has anticonvulsant effects dosedependently. It seems that a dose of 0.2 ml/kg is the minimum effective dose. Further investigation is warranted to conduct the clinical implications for the treatment of epileptic disorders
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Animais , Masculino , Ratos , Convulsões/prevenção & controle , Epilepsia/patologia , Anticonvulsivantes/administração & dosagem , Tonsila do Cerebelo/fisiopatologiaRESUMO
The phenomenon of Forced Normalization (FN) was first described by Landolt in 1953, who described the disappearance of epileptiform discharges in the EEG of patients with epilepsy, concomitant with the development of psychotic symptoms. Later, Tellenbach coined the term "alternative psychosis" referring specifically to the alternation between clinical phenomena. Finally, in 1991, Wolf observed a degenerative process involved in the phenomenon, which he called "paradoxical normalization." Initially, FN was explained through experimental models in animals and the demonstration of the kindling phenomenon, in its electrical and pharmacological subdivisions. At this stage of research on the epileptic phenomenon, repetitive electrical stimuli applied to susceptible regions of the brain (hippocampus and amygdala) were considered to explain the pathophysiological basis of temporal lobe epileptogenesis. Likewise, through pharmacological manipulation, especially of dopaminergic circuits, psychiatric comorbidities began to find their basic mechanisms. With the development of new imaging techniques (EEG/fMRI), studies in the area started to focus on the functional connectivity (FC) of different brain regions with specific neuronal networks, which govern emotions. Thus, a series of evidence was produced relating the occurrence of epileptic discharges in the limbic system and their consequent coactivation and deactivation of these resting-state networks. However, there are still many controversies regarding the basic mechanisms of network alterations related to emotional control, which will need to be studied with a more homogeneous methodology, in order to try to explain this interesting neuropsychiatric phenomenon with greater accuracy.
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The Wistar audiogenic rat (WAR) strain is used as an animal model of epilepsy, which when submitted to acute acoustic stimulus presents tonic-clonic seizures, mainly dependent on brainstem (mesencephalic) structures. However, when WARs are exposed to chronic acoustic stimuli (audiogenic kindling-AK), they usually present tonic-clonic seizures, followed by limbic seizures, after recruitment of forebrain structures such as the cortex, hippocampus and amygdala. Although some studies have reported that hypothalamic-hypophysis function is also altered in WAR through modulating vasopressin (AVP) and oxytocin (OXT) secretion, the role of these neuropeptides in epilepsy still is controversial. We analyzed the impact of AK and consequent activation of mesencephalic neurocircuits and the recruitment of forebrain limbic (LiR) sites on the hypothalamic-neurohypophysial system and expression of Avpr1a and Oxtr in these structures. At the end of the AK protocol, nine out of 18 WARs presented LiR. Increases in both plasma vasopressin and oxytocin levels were observed in WAR when compared to Wistar rats. These results were correlated with an increase in the expressions of heteronuclear (hn) and messenger (m) RNA for Oxt in the paraventricular nucleus (PVN) in WARs submitted to AK that presented LiR. In the paraventricular nucleus, the hnAvp and mAvp expressions increased in WARs with and without LiR, respectively. There were no significant differences in Avp and Oxt expression in supraoptic nuclei (SON). Also, there was a reduction in the Avpr1a expression in the central nucleus of the amygdala and frontal lobe in the WAR strain. In the inferior colliculus, Avpr1a expression was lower in WARs after AK, especially those without LiR. Our results indicate that both AK and LiR in WARs lead to changes in the hypothalamic-neurohypophysial system and its receptors, providing a new molecular basis to better understaind epilepsy.
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Epilepsia Reflexa , Hipotálamo/metabolismo , Excitação Neurológica/fisiologia , Sistemas Neurossecretores/metabolismo , Neuro-Hipófise/metabolismo , Estimulação Acústica , Animais , Modelos Animais de Doenças , Epilepsia Reflexa/genética , Epilepsia Reflexa/metabolismo , Epilepsia Reflexa/patologia , Epilepsia Reflexa/fisiopatologia , Regulação da Expressão Gênica , Hipocampo/metabolismo , Hipocampo/patologia , Hipocampo/fisiopatologia , Hipotálamo/patologia , Hipotálamo/fisiopatologia , Excitação Neurológica/patologia , Masculino , Sistemas Neurossecretores/patologia , Sistemas Neurossecretores/fisiopatologia , Ocitocina/sangue , Ocitocina/genética , Ocitocina/metabolismo , Neuro-Hipófise/patologia , Neuro-Hipófise/fisiopatologia , Ratos , Ratos Wistar , Convulsões/genética , Convulsões/metabolismo , Convulsões/fisiopatologia , Convulsões/psicologia , Vasopressinas/sangue , Vasopressinas/genética , Vasopressinas/metabolismoRESUMO
This study evaluated the effect of lacosamide (LCM) on biochemical and mitochondrial parameters after PTZ kindling in mice. Male mice were treated on alternative days for a period of 11 days with LCM (20, 30, or 40 mg/kg), saline, or diazepam (2 mg/kg), before PTZ administration (50 mg/kg). The hippocampi were collected to evaluate free radicals, the activities of superoxide dismutase (SOD), catalase (CAT), and the mitochondrial complexes I-III, II, and II-III, as well as Bcl-2 and cyclo-oxygenase-2 (COX-2) expressions. Hippocampi, blood, and bone marrow were collected for genotoxic and mutagenic evaluations. LCM 40 mg/kg increased latency and decreased percentage of seizures, only on the 3rd day of observation. The dose of 30 mg/kg only showed positive effects on the percentage of seizures on the 2nd day of observation. LCM decreased free radicals and SOD activity and the dose of 40 mg/kg were able to increase CAT activity. LCM 30 and 40 mg/kg improved the enzymatic mitochondrial activity of the complex I-III and LCM 30 mg/kg improved the activity of the complex II. In the comet assay, the damage induced by PTZ administration was reduced by LCM 20 and 30 mg/kg. The dose of 20 mg/kg increased COX-2 expression while the highest dose used, 40 mg/kg, was able to reduce this expression when compared to the group treated with LCM 20 mg/kg. Although LCM did not produce the antiepileptogenic effect in vivo, it showed the neuroprotective effect against oxidative stress, bioenergetic dysfunction, and DNA damage induced by the repeated PTZ administration.
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Excitação Neurológica/efeitos dos fármacos , Lacosamida/farmacologia , Fármacos Neuroprotetores/farmacologia , Animais , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Masculino , Camundongos , Camundongos Endogâmicos , PentilenotetrazolRESUMO
Research on the prevention of post-traumatic epilepsy (PTE) has seen remarkable advances regarding its physiopathology in recent years. From the search for biomarkers that might be used to indicate individual susceptibility to the development of new animal models and the investigation of new drugs, a great deal of knowledge has been amassed. Various groups have concentrated efforts in generating new animal models of traumatic brain injury (TBI) in an attempt to provide the means to further produce knowledge on the subject. Here we forward the hypothesis that restricting the search of biomarkers and of new drugs to prevent PTE by using only a limited set of TBI models might hamper the understanding of this relevant and yet not preventable medical condition.
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Animais , Epilepsia Pós-Traumática/etiologia , Epilepsia Pós-Traumática/prevenção & controle , Modelos Animais de Doenças , Lesões Encefálicas Traumáticas/complicações , Lesões Encefálicas Traumáticas/prevenção & controle , BiomarcadoresRESUMO
Background: Clinical and experimental evidence indicates that olfactory stimulation modulates limbic seizures, either blocking or inducing ictal activity. Objective: We aim to evaluate the behavioral and electroencephalographic (EEGraphic) effects of dihydro-2,4,5-trimethylthiazoline (TMT) olfactory exposure on limbic seizures induced by amygdala rapid kindling (ARK). Materials and Methods: Wistar male rats (280-300 g) underwent stereotaxic surgery for electrode implantation in piriform cortex (PC), hippocampal formation (HIP), and amygdaloid complex (AMYG). Part of the animals was exposed to a saturated chamber with water or TMT, while others had ARK and olfactory exposure prior to the 21st stimulus. Behavioral responses were measured by traditional seizure severity scales (Racine and Pinel and Rovner) and/or by sequential analysis/neuroethology. The electrographic activity of epileptogenic limbic networks was quantified by the occurrence of the first and second EEG afterdischarges, comparing the 1st and 21st stimulus. The spectral analysis [Fast Fourier Transform (FFT)] of the first afterdischarge was performed at the 21st stimulus. Results: TMT olfactory exposure reduced the seizure severity in kindled rats, altering the displayed behavioral sequence. Moreover, TMT decreased the occurrence of first and second afterdischarges, at the 21st stimulus, and altered the spectral features. Conclusions: Both behavioral and EEGraphic evaluations indicated that TMT, a potent molecule with strong biological relevance, in fact, "predator odor," suppressed the epileptiform activity in limbic networks.
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Epilepsy is characterized by a progressive predisposition to suffer seizures due to neuronal hyperexcitability, and one of its most common co-morbidities is cognitive decline. In animal models of chronic epilepsy, such as kindling, electrically induced seizures impair long-term potentiation (LTP), deteriorating learning and memory performance. Astrocytes are known to actively modulate synaptic plasticity and neuronal excitability through Ca2+-dependent gliotransmitter release. It is unclear, however, if astroglial Ca2+ signaling could contribute to the development of synaptic plasticity alterations in the epileptic hippocampus. By employing electrophysiological tools and Ca2+ imaging, we found that glutamatergic CA3-CA1 synapses from kindled rats exhibit an impairment in theta burst (TBS) and high frequency stimulation (HFS)-induced LTP, which is accompanied by an increased probability of neurotransmitter release (Pr) and an abnormal pattern of astroglial Ca2+-dependent transients. Both the impairment in LTP and the Pr were reversed by inhibiting purinergic P2Y1 receptors (P2Y1R) with the specific antagonist MRS2179, which also restored the spontaneous and TBS-induced pattern of astroglial Ca2+-dependent signals. Two consecutive, spaced TBS protocols also failed to induce LTP in the kindled group, however, this impairment was reversed and a strong LTP was induced when the second TBS was applied in the presence of MRS2179, suggesting that the mechanisms underlying the alterations in TBS-induced LTP are likely associated with an aberrant modulation of the induction threshold for LTP. Altogether, these results indicate that P2Y1R inhibition rescues both the pattern of astroglial Ca2+-activity and the plastic properties of CA3-CA1 synapses in the epileptic hippocampus, suggesting that astrocytes might take part in the mechanisms that deteriorate synaptic plasticity and thus cause cognitive decline in epileptic patients.
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Astrócitos/metabolismo , Cálcio/metabolismo , Epilepsia/fisiopatologia , Plasticidade Neuronal/fisiologia , Receptores Purinérgicos P2Y1/metabolismo , Animais , Região CA1 Hipocampal/metabolismo , Potenciais Pós-Sinápticos Excitadores/fisiologia , Potenciação de Longa Duração/fisiologia , Ratos , Receptores de N-Metil-D-Aspartato/metabolismo , Sinapses/fisiologiaRESUMO
There is increasing recognition that, in a high percentage of cases, bipolar disorder is a progressive illness. Multiple types of sensitization (or increased reactivity to repetition of the same stimulus) drive illness progression. One of the clearest is that of episode sensitization, where increased numbers of prior episodes are associated with: faster recurrences; more dysfunction; disability; social, educational, and employment deficits; suicide; medical comorbidities; cognitive dysfunction; and an increased incidence of dementia in old age. Repetition of stressors and bouts of substance abuse can also result in sensitization. Each type of sensitization appears to have an epigenetic basis, such that preventing sensitization should minimize the accumulation of adverse epigenetic chemical marks on DNA, histones, and microRNA. New data emphasize the importance of early, consistent intervention after an initial manic episode. The cognitive dysfunction associated with a first episode improves only if there are no further episode recurrences during the next year. A randomized study has also shown that comprehensive multimodal prophylactic intervention for 2 years leads to improvements in illness course extending over a total of 6 years. Intensive treatment of the earliest stages of bipolar disorder can thus exert lasting positive effects on the course of illness.
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Humanos , Transtorno Bipolar/prevenção & controle , Transtorno Bipolar/epidemiologia , Transtornos Relacionados ao Uso de Substâncias , Recidiva , Comorbidade , Progressão da DoençaRESUMO
The Wistar Audiogenic Rat (WAR) strain is a genetic model of epilepsy, specifically brainstem-dependent tonic-clonic seizures, triggered by acute auditory stimulation. Chronic audiogenic seizures (audiogenic kindling) mimic temporal lobe epilepsy, with significant participation of the hippocampus, amygdala, and cortex. The objective of the present study was to characterize the mitochondrial energy metabolism in hippocampus and cortex of WAR and verify its relationship with seizure severity. Hippocampus of WAR naïve (no seizures) presented higher oxygen consumption in respiratory states related to the maximum capacities of phosphorylation and electron transfer system, elevated mitochondrial density, lower GSH/GSSG and catalase activity, and higher protein carbonyl and lactate contents, compared with their Wistar counterparts. Audiogenic kindling had no adding functional effect in WAR, but in Wistar, it induced the same alterations observed in the audiogenic strain. In the cortex, WAR naïve presented elevated mitochondrial density, lower GSH/GSSG and catalase activity, and higher protein carbonyl levels. Chronic acoustic stimulation in Wistar induced the same alterations in cortex and hippocampus. Mainly in the hippocampus, WAR naïve presented elevated mRNA expression of glucose, lactate and excitatory amino acids transporters, several glycolytic enzymes, lactate dehydrogenase, and Na+/K+ ATPase in neurons and in astrocytes. In vivo treatment with mitochondrial uncoupler 2,4-dinitrophenol (DNP) or N-acetylcysteine (NAC) in WAR had no effect on mitochondrial metabolism, but lowered oxidative stress. Unlike DNP, NAC downregulated all enzyme genes involved in glucose and lactate uptake, and metabolism in neurons and astrocytes. Additionally, it was able to reduce brainstem seizure severity in WAR. In conclusion, in WAR naïve animals, both cerebral cortex and hippocampus display elevated mitochondrial density and/or activity associated with oxidative damage, glucose and lactate metabolism pathways upregulation, and increased Na+/K+ ATPase mRNA expression. Only in vivo treatment with NAC was able to reduce seizure severity of kindled WARs, possibly via down regulation of glucose/lactate metabolism. Taken together, our results are a clear contribution to the field of mitochondrial metabolism associated to epileptic seizures.
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BACKGROUND: Variation in the temporal patterns of electrical pulses in stimulation trains has opened a new field of opportunity for the treatment of neurological disorders, such as pharmacoresistant temporal lobe epilepsy. Whether this novel type of stimulation affects epileptogenesis remains to be investigated. OBJECTIVE: The purpose of this study was to analyze the effects of temporally irregular deep brain stimulation on kindling-induced epileptogenesis in rats. METHODS: Temporally irregular deep brain stimulation was delivered at different times with respect to the kindling stimulation. Behavioral and electrographic changes on kindling acquisition were compared with a control group and a temporally regular deep brain stimulation-treated group. The propagation of epileptiform activity was analyzed with wavelet cross-correlation analysis, and interictal epileptiform discharge ratios were obtained. RESULTS: Temporally irregular deep brain stimulation delivered in the epileptogenic focus during the interictal period shortened the daily afterdischarge duration, slowed the progression of seizure stages, diminished the generalized seizure duration and interfered with the propagation of epileptiform activity from the seizure onset zone to the ipsi- and contralateral motor cortex. We also found a negative correlation between seizure severity and interictal epileptiform discharges in rats stimulated with temporally irregular deep brain stimulation. CONCLUSION: These results provide evidence that temporally irregular deep brain stimulation interferes with the establishment of epilepsy by delaying epileptogenesis by almost twice as long in kindling animals. Thus, temporally irregular deep brain stimulation could be a preventive approach against epilepsy.
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Estimulação Encefálica Profunda/métodos , Modelos Animais de Doenças , Epilepsia/terapia , Excitação Neurológica/fisiologia , Animais , Estimulação Elétrica/métodos , Epilepsia/fisiopatologia , Masculino , Ratos , Ratos Wistar , Convulsões/fisiopatologia , Convulsões/terapia , Fatores de TempoRESUMO
The purpose of this study is to determine the activation of the extrinsic and intrinsic apoptotic pathways in the cerebellum of rats exposed to amygdaloid electrical kindling. Western blot analyses were carried out for caspase-8 and caspase-9, Bid, Bax, and Bcl-2 in the cerebellum and immunohistochemistry of Bid, Bax, cytochrome C, and VDAC (voltage-dependent anion channels) in the cerebellar cortex of Wistar male rats with 0, 15, and 45 kindling stimulations. In the experimental group of 45 stimuli, we observed an increase in protein activation of caspase-9 and truncated Bid and Bax, in addition to a decrease in expression of pro-caspase-8 and the anti-apoptotic protein Bcl-2, determined by Western blot. Moreover, we observed a cytosolic immunopositivity for cytochrome C and a mitochondrial immunolocalization for truncated Bid and Bax in the group of 45 stimuli. In this work, we found an increase of caspase-8, a cysteine-protease that can activate caspase-3 triggering extrinsic apoptosis by signaling of death receptors. However, it also can activate the intrinsic pathway releasing Bid, which performs mitochondrial translocation of Bax, inactivating Bcl-2 and allowing the release of cytochrome C through the opening of the mitochondrial permeability transition pore, promoting the activation of caspase-9 which activates caspase-3, the main executor caspase of apoptosis. Therefore, it is concluded that there is an activation of the intrinsic and extrinsic apoptotic pathways in the cerebellum of rats exposed to the kindling model. Apoptosis signaling pathways can be analyzed as an important developing object of research about the epileptic activity. Graphical Abstract.
Assuntos
Proteínas Reguladoras de Apoptose/genética , Apoptose/fisiologia , Cerebelo/fisiologia , Excitação Neurológica , Tonsila do Cerebelo/fisiologia , Animais , Proteínas Reguladoras de Apoptose/biossíntese , Córtex Cerebelar/fisiologia , Eletrodos Implantados , Imuno-Histoquímica , Masculino , Ratos , Ratos WistarRESUMO
Temporal lobe epilepsy is often accompanied by behavioral, electroencephalographic and autonomic abnormalities. Amygdala kindling has been used as an experimental model to study epileptogenesis. Although amygdala kindling has been extensively investigated in the context of its clinical relevance to the epilepsies, potential associated respiratory alterations are not well known. Here, our main objective was to better investigate the mechanisms involved in respiratory physiology impairment in the amygdala rapid kindling (ARK) model of epileptogenesis. Male Wistar rats with electrodes implanted into the amygdaloid complex were used. After recovery from surgery, the rats were subjected to electrical stimulation of basolateral amygdala for 2 consecutive days (10â¯stimuli/day). The ventilatory parameters were evaluated by whole body plethysmography. Thereafter, animals were also exposed to hypercapnia (7% CO2) for 3â¯h to evaluate fos protein expression in several nuclei involved in respiratory control. We observed a significant reduction in ventilation during the ictal phase elicited by ARK. We also found that 10â¯days after ARK, baseline ventilation as well as the hypercapnia ventilatory response (7% CO2) were reduced compared to control rats. The number of fos-immunoreactive neurons in the retrotrapezoid nucleus, raphe magnus and nucleus of the solitary tract were also reduced after ARK. Our results showed that ARK was able to impair breathing function, demonstrating a strong coupling between amygdala and the respiratory neurons in the brainstem, with potential impact in respiratory failures, frequently fatal, during or after epileptic seizures in chronic animal models and in patients.