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Background Epilepsy is a disorder characterized by recurrent seizures that affects 1% of the population. However, the neurochemical alterations observed in epilepsy are not fully understood. There are different animal models of epilepsy, such as genetic or drug induced. In the present study, we utilize Wistar Audiogenic Rats (WAR), a murine strain that develops seizures in response to high intensity audio stimulation, in order to investigate abnormalities in glutamatergic and GABAergic systems. Methods Synaptosomes and glial plasmalemmal vesicles were prepared from hippocampus and cortex, respectively. Glutamate and GABA release and uptake were assayed by monitoring the fluorescence and using L-[3H]-radiolabeled compounds. Glutamate and calcium concentration in the synaptosomes were also measured. The expression of neuronal calcium sensor 1 (NCS-1) was determined by western blot. Results Glutamate and GABA release evoked by KCl was decreased in WAR compared to control Wistar rats. Calcium independent release was not considerably different in both groups. The total amount of glutamate of synaptosomes, as well as glutamate uptake by synaptosomes and GPV were also decreased in WAR in comparison with the controls. In addition, [Ca2+]i of hippocampal synaptosomes, as well as NCS-1 expression in the hippocampus, were increased in WAR in comparison with controls. Conclusion In conclusion, our results suggest that WAR have important alterations in the glutamatergic and GABAergic pathways, as well as an increased expression of NCS-1 in the hippocampus and inferior colliculus. These alterations may be linked to the spreading of hyperexcitability and recruitment of various brain regions.

Increasing body of evidence suggests that inflammatory and neurotrophic factors might be important for epileptogenesis. Most animal studies demonstrated altered levels of these mediators in drug-induced models of seizures and epilepsy. In the present study, we investigated the production of cytokines and a neurotrophin in the brain of Wistar Audiogenic Rats (WAR), a genetic model of epilepsy, stimulated with high-intensity sound. Four hours after stimulation, animals were decapitated and the hippocampus, inferior colliculus, striatum and cortex were removed for evaluation of the levels of interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α and brain derived neurotrophic factor (BDNF). All the cytokines and BDNF levels were increased in the cortex. Increased levels of TNF-α and IL-6 were also observed in the striatum. Finally, TNF-α also increased in the inferior colliculus after the seizures induced by high-intensity sound. Although different studies have demonstrated that the levels of cytokines and BDNF increase in animal models of epilepsy induced by chemical stimuli, we provided here evidence that these mediators are also increased in WAR, a genetic model of epilepsy. Thus, the observed increase in these mediators might be involved in the pathophysiology of epilepsy.

Calcium ion participates in the regulation of neural transmission and the presynaptic release of neurotransmitters. It is also involved in epileptic events, cardiac arrhythmias and abnormal conduction of stimuli. The purpose of the present study was to evaluate the effects of nifedipine, a calcium channel blocker, on epileptic seizures and on reperfusion arrhythmias in rats prone to audiogenic epileptic seizures (Wistar audiogenic rats, WAR) and in normal Wistar rats (N = 6/group). The seizure severity index was applied after an intraperitoneal injection of 20 or 40 mg/kg nifedipine (N20 and N40 groups, respectively). The Langendorff technique was used to analyze cardiac function, as well as the incidence and severity of the reperfusion arrhythmias after ligature and release of the left coronary artery in rats treated or not with nifedipine. We found that nifedipine treatment decreased seizure severity (0.94 ± 0.02 for WAR; 0.70 ± 0.10 for WAR + N20; 0.47 ± 0.08 for WAR + N40) and increased the latent period (13 ± 2 s for WAR; 35 ± 10 s for WAR + N20; 48 ± 7 s for WAR + N40) for the development of seizures in WAR. Furthermore, the incidence and severity of the reperfusion arrhythmias were lower in WAR and normal Wistar rats injected with nifedipine. In WAR, these effects were mediated, at least in part, by a decrease in heart rate. Thus, our results indicate that nifedipine may be considered to be a potential adjuvant drug for epilepsy treatment, especially in those cases associated with cardiac rhythm abnormalities.

A non-hygroscopic pharmaceutical composition was obtained following a host-guest strategy that used the anticonvulsant drug sodium valproate (VA) and α-cyclodextrin. The pharmaceutical composition was fully characterized by thermal analyses (TG/DTG, DSC), X-ray powder diffraction and by 1H, 13C, hydrogen relaxation times (T 1) and 2D-ROESY NMR techniques. Isothermal titration calorimetry (ITC) was used to determine the VA:α-CD 1:1 stoichiometry as well as to calculate the equilibrium constant (K) and thermodynamic energies of interaction (ΔGo, ΔHo and TΔSo).

Previous work from our laboratory has shown that naïve Wistar Audiogenic Rats (WARs), a genetic model of reflex epilepsy in which seizures are induced by high-intensity sound stimulation (120 dB SPL), are seizure-prone to a variety of pro-convulsive stimuli (e.g., transauricular electroshock, pentylenetetrazole and pilocarpine). On the other hand, repetitive acoustic stimulation of WARs causes a slow recruitment of limbic structures, known as audiogenic kindling, changing seizure expression to include behavior characteristic of temporal-lobe epilepsy. Thus, our hypothesis is that WARs have facilitated acoustic-limbic projections when compared to Wistar controls. Wistar controls (n = 9) and WARs (n = 9) underwent EEG electrode implants in the cortex-Cx, amygdaloid complex-AMY and inferior colliculus-IC and received one low current transauricular electrical stimulus (ES) daily, for three consecutive days, with intensities of 10, 20 and 30 mA, respectively. The video-electroencephalographic activity was recorded 1 min before and 4 min after ES. Our results confirm previously described data indicating a greater susceptibility of WARs to seizure. However, low current ES (e.g., 20 mA) triggered epileptiform activity in the AMY only after epileptiform EEG was visible in the Cx and IC electrode leads. The AMY after-discharge continued even though no evident epileptiform activity was present in the Cx. In conclusion, our results add electrophysiological data to previously published behavioral evidence of WAR enhanced susceptibility to ES seizures and, also, support the hypothesis that the acoustic-limbic circuitry is facilitated even in unkindled WARs.

Aryl semicarbazones can be considered a novel class of compounds presenting anticonvulsant activity. In order to improve the efficiency and bioavailability of benzaldehyde semicarbazone (BS) we used the host–guest strategy and β-cyclodextrin (β-CD) to prepare a BS/β-CD 1:1 inclusion compound, which was characterized by thermal analyses (TG, DTG, DSC), XRD powder pattern diffraction analyses, infrared data and 1H, 13C, 2D-ROESY NMR and 1H relaxation times. The BS/β-CD inclusion compound was tested in rats using the maximum electroshock (MES) screen. The minimum dose necessary to produce anticonvulsant activity decreased from 100 mg/Kg (ip or vo) for the free semicarbazone to 25 mg/Kg/vo (75%) and 15 mg/Kg/ip (85%), indicating that the host–guest strategy that uses β-CD and BS is very effective and could be successfully employed in the preparation of pharmaceutical formulationof anticonvulsants.

Plasma glucose and lactate, hepatic glycogen and epididymal adipose tissue lipogenesis and lipolysis were studied in Wistar audiogenic rats (WARs), a genetic model of epilepsy, under three experimental conditions, i.e., before, 3 min after and 10 min after seizures induced by intense sound exposure. Plasma glucose increased 3 min after the seizure onset and rose to a peak after 10 min. Hepatic glycogen decreased significantly in susceptible audiogenic rats compared to nonepileptic controls, even before sound stimulation. A marked ( approximately 10-fold) rise was observed in plasma lactate levels 3 and 10 min after the seizures compared to the response of the control group. Lipogenic activity showed a marked decrease even after stimulation with 25 ng/ml insulin. Based on these results, WARs showed reduced isoproterenol-stimulated lipolysis compared to control animals, whereas basal levels only differed significantly at 10 min after seizure activity. In conclusion, it can be inferred from these results that (a) the increase in plasma glucose after stimulation might result from sequential interaction of autonomic activation at seizure onset; (b) excessive muscular activity was at least partially responsible for the steady rise in plasma lactate concentrations; (c) audiogenic seizures, which increase adrenergic activity, induce desensitization of the beta-adrenergic lipolytic pathway in epididymal adipose tissue; (d) genetic selection for audiogenic seizure susceptibility results in pronounced alterations at multiple levels of metabolic regulation.

This work evaluates the seizure susceptibility of nai;ve female Wistar Audiogenic rats (WARs), a genetic model of reflex epilepsy in which seizures are induced by high-intensity sound stimulation (120 dB SPL), to other pro-convulsive stimuli: transauricular electroshock (ES), pentylenetetrazole (PTZ) and pilocarpine (PILO). Normal Wistar rats from the main breeding stock of the Institute of Biological Sciences, UFMG were taken as controls. Electroshock seizures were induced through a pair of ear-clip electrodes (10 mA, at a frequency of 60 Hz, applied for 1 s). In order to test WAR susceptibility to chemically induced seizures, animals were treated either with PTZ (37.5 mg/kg i.p.) or PILO (200, 270 and 300 mg/kg i.p.). Seizure severity was evaluated by appropriate behavioral severity index scales (SI) specific to each epilepsy model and tested for statistical significance using the non-parametric Mann-Whitney Rank Sum test. Results show a significantly greater susceptibility of WARs for ES (SI(WAR)=3+/-3/3, SI(Wistar)=1+/-1/1; median+/-interquartile range 25%/75%, P

Background Cardiac dysfunction is one of the possible causes of sudden unexpected death in epilepsy (SUDEP). Therefore, it was the objective of this study to evaluate the cardiac and electrocardiographic parameters after seizures induced by maximal electroshock (MES) in Wistar rats. Methods Electroshock seizures were induced in Wistar rats through a pair of ear-clip electrodes (10mA at a frequency of 60Hz applied for one second). In vivo electrocardiography (ECG) was performed in awake animals for analysis of heart rate variability (HRV) and cardiac rhythm. Ex vivo the Langendorff technique was used to analyze cardiac function and observe the incidence and severity of reperfusion arrhythmias. Results Convulsive seizures triggered by MES induced profound abnormalities in cardiac rhythm with serious electrocardiographic changes including ST-elevation, bundle branch block, atrioventricular nodal escape rhythm and premature ventricular contractions. ECG analysis demonstrated a consistent period of postictal bradyarrhythmia resulting in a transiently irregular cardiac rhythm with highly variable and prolonged QRS complexes and RR, PR, QT and QTc intervals. HRV evaluation revealed an increase in the high-frequency range of the power, suggesting an imbalance in the autonomic control of the heart with a postictal enhancement of parasympathetic tone. In addition, we observed in isolated heart a decrease in systolic tone and an increase in the coronary flow, heart rate and incidence/duration of ischemia–reperfusion arrhythmias. Conclusion The present study supports a relationship betweem seizures, cardiac dysfunction and cardiac arrhythmias. This relationship may partially account for the occurrence of SUDEP.

Epilepsy is a neurological disorder associated with excitatory and inhibitory imbalance within the underlying neural network. This study evaluated inhibitory γ-amino-butyric acid (GABA)ergic modulation in the CA1 region of the hippocampus of male Wistar rats and Wistar audiogenic rats (aged 90 ± 3 days), a strain of inbred animals susceptible to audiogenic seizures. Field excitatory postsynaptic potentials and population spike complexes in response to Schaffer collateral fiber stimulation were recorded in hippocampal slices before and during application of picrotoxin (50 µM, 60 min), a GABA A antagonist, and the size of the population spike was quantified by measuring its amplitude and slope. In control audiogenic-resistant Wistar rats (N = 9), picrotoxin significantly increased both the amplitude of the population spike by 51 ± 19% and its maximum slope by 73 ± 21%. In contrast, in slices from Wistar audiogenic rats (N = 6), picrotoxin caused no statistically significant change in population spike amplitude (33 ± 46%) or slope (11 ± 29%). Data are reported as means ± SEM. This result indicates a functional reduction of GABAergic neurotransmission in hippocampal slices from Wistar audiogenic rats.

Our working hypothesis is that constant interpulse interval (IPI) electrical stimulation would resonate with endogenous epileptogenic reverberating circuits, inducing seizures, whereas a random interinterval electrical stimulation protocol would promote desynchronization of such neural networks, producing an anticonvulsant effect. Male Wistar rats were stereotaxically implanted with a bipolar electrical stimulation electrode in the amygdala. Pentylenetetrazole (10 mg/ml/min) was continuously infused through an intravenous catheter to induce seizures while four different patterns of temporally coded electrical stimulation were applied: periodic stimulation (PS), pseudo-randomized IPI stimulation (LH), restrictively randomized IPI stimulation (IH), and bursts of 20-ms IPIs (burst). PS decreased the pentylenetetrazole threshold to forelimb clonus, whereas IH increased the threshold to forelimb clonus and to generalized tonic–clonic seizures. We hypothesize that PS facilitates forelimb clonus by reverberating with epileptogenic circuits in the limbic system, whereas IH delays forelimb clonus and generalized tonic–clonic seizures by desynchronizing the epileptic neural networks in the forebrain–midbrain–hindbrain circuits.

INTRODUÇÃO: Epilepsia e depressão são duas das mais freqüentes morbidades que acometem o sistema nervoso central. Vários estudos mostram que muitas pessoas com epilepsia são também acometidas de depressão. OBJETIVO: Alertar quanto à prevalência da comorbidade depressão/epilepsia e a importância do tratamento concomitante das duas entidades, bem como auxiliar na escolha da melhor abordagem terapêutica. MÉTODO: Foi realizada uma pesquisa no HighWire Press no período de 1996-2007, utilizando-se os descritores: depression, epilepsy, seizures, treatment, além de referências cruzadas dos artigos selecionados e análise adicional de referências na literatura específica do tema. RESULTADOS: Apesar da grande influência negativa dos transtornos de humor na qualidade de vida de pessoas com epilepsia, existe uma injustificada resistência dos clínicos em tratar concomitantemente ambas as enfermidades. CONCLUSÃO: Apesar das evidências, existe ainda uma demora em iniciar o tratamento da depressão em pacientes com epilepsia, com prejuízo da qualidade de vida. É necessário que neurologistas e psiquiatras estejam preparados para conduzir satisfatoriamente esses casos. INTRODUCTION: Epilepsy and depression are two of the most frequent central nervous system disorders. Some studies have shown that many individuals with epilepsy also suffer of depression. OBJECTIVE: To warning about the prevalence of co-morbidity of depression/epilepsy and the importance of the concomitant treatment of the two entities, as well as to assist in the choice of the best therapeutic approach. METHOD: A searching in the HighWire Press in the period of 1996-2007 was carried out, using the describers: depression, epilepsy, seizures, treatment, crossed references of selected articles and additional analysis of references in the specific literature. RESULTS: Despite the negative influence of the mood disorders in the quality of life of patients with epilepsy, there is an unjustified resistance of physicians in treating both diseases. CONCLUSIONS: Neurologists and psychiatrists should be prepared to treat these patients successfully and thus improve the quality of life of patients with epilepsy.

The aim of the present study was to investigate the status of jejunal absorption and peripheral metabolism of glucose in Wistar Audiogenic Rats (WAR), a genetic model of epilepsy, after seizures induced by intensive sound exposure. The jejunal loop of rats was isolated and infused (0.5 mL min(-1)) with Tyrode solution containing twice the normal concentrations of glucose, sodium, and potassium. Samples were taken at 5 or 10-min intervals over a 40-min period. At the end of the experiment, samples of liver and gastrocnemius muscle were taken to measure the levels of glycogen, glucose-6-phosphate, fructose-6-phosphate and glucose transporter-4 (GLUT4). Hepatic glucose-6-phosphate increased in WAR submitted to audiogenic seizure (21.90 +/- 3.08) as compared to non-susceptible Wistar rats (8.12 +/- 0.87) and to WAR not submitted to audiogenic stimulation (5.17 +/- 0.97). In addition, an increase in hepatic fructose-6-phosphate, an intermediate metabolite of the glycolytic pathway, was observed in WAR submitted to audiogenic seizure (5.98 +/- 0.99) compared to non-susceptible Wistar rats (2.38 +/- 0.53). According to the present results, jejunal absorption of glucose was not changed by seizures. However, generalized tonic-clonic seizures produced by sound stimulation resulted in a decrease in muscle glycogen content. In addition, our results demonstrated that the concentration of GLUT4 in the gastrocnemius muscle of WAR was 1.6-fold higher than that observed in resistant rats and that the audiogenic stimulus led to decreased concentration of this receptor in the muscle of WAR animals.

The Wistar Audiogenic Rat (WAR) is a genetic model of reflex epilepsy with seizures induced by high-intensity sound stimulation (120 dB SPL). In spite of the known neural substrates involved in WAR seizure phenotype, neuroendocrine hypothalamic neurons were never investigated. In this work, AVP immunohistochemistry in the hypothalamus and radioimmunoassay (RIA) in plasma and in hypothalamic and hypophysial tissues were performed on both controls and WARs in order to evaluate the dynamics of AVP release due to seizure induction. Susceptible animals (WARs) displayed at least tonic-clonic convulsions followed by clonic spasms, while resistant Wistar rats (R) had no convulsive behavior. Animals were sacrificed at 3 instances: basal condition (without stimulus) and at 3 and 10 min after sound stimulation. For the immunohistochemistry AVP study, brains were harvested and processed by the avidin-biotin-peroxidase detection method. Optic densitometry was used for quantifying AVP labeling in supraoptic (SON) and paraventricular (PVN) hypothalamic nuclei. SON presented higher densitometry levels (%D--relative to background) for both WARs and R when compared to PVN. Nevertheless, both nuclei presented a marked decrease, referenced to basal levels, in %D for WARs at 3 min (approximately 35%) against a discrete change for R (approximately 90%). RIA results were significantly higher in the hypophysis of WARs when compared to R rats, at 3 min. Also, at 3 min, plasma AVP in WARs (89.32 +/- 24.81 pg/mL) were higher than in R (12.01 +/- 2.39 pg/mL). We conclude, based on the AVP releasing profiles, that vasopressinergic hypothalamic neurons are recruited during the audiogenic seizure of WARs.

The neurochemical mechanisms involved in post-ictal antinociception remain to be elucidated. Application of electroconvulsive shock (ECS) to rats results in post-ictal antinociception. The objective of this study was to identify endogenous substances that could participate in antinociception during post-ictal depression induced by ECS (70 mA, 60 Hz, 1 s). Antinociception was measured by the rat paw-pressure test, in which increased sensitivity is induced by intraplantar injection of carrageenan. This test proved to be efficient in detecting the electroshock-induced antinociception. Intense post-ictal antinociception was observed over a period of 30 min after the end of the seizure. It was used nonspecific opioid and specific vasopressin antagonists and the prolactin (PRL) release inhibitor to test the reversal of antinociception. Administration of naloxone (5, 7.5 and 10 mg/kg) blocked the post-ictal antinociception. The V(1) (125 microg/kg) and V(2) (250 microg/kg) vasopressin receptor antagonists ([beta-mercapto-beta,beta-cyclopentamethylenepropionyl(1),O-Et-Tyr(2),Val(4),Arg(8)]-vasopressin and [adamantaneacetyl(1),O-Et-d-Tyr(2),Val(4),Abu(6),Arg(8,9)]-vasopressin) also inhibited the nociceptive response. The antinociception blockade was more intense after administration of the V(1) receptor antagonist. Bromocriptine (4, 8 and 12 mg/kg) was able to reverse antinociception behavior during the post-ictal period. Morphine (1, 2 and 4 mg/kg), vasopressin (12.5, 100 and 400 microg/kg) and prolactin (100, 200 and 400 microg/kg) administration promoted a higher nociceptive threshold. It was administered the three substances with their respective antagonists to verify the opioidergic pathway and vasopressin and prolactin release interactions, and as a positive control. We observed that the tested mediators were released in an independent manner, indicating no interference in which other.

It was previously reported that systemic administration of dipyrone inhibited the tonic component of generalized tonic-clonic seizures in both the electroshock and the audiogenic seizure models. The aim of the present study was to investigate the mechanisms involved in the anticonvulsant action of dipyrone by assessing the role of nitric oxide and opioids in the electroshock (female 60- to 90-day-old Wistar rats, N = 5-11) and audiogenic seizure (female 60- to 90-day-old Wistar audiogenic rats, N = 5-11) models of epilepsy. Naloxone (5 mg/kg, sc) significantly reversed the anticonvulsant effect of dipyrone in rats submitted to the induction of audiogenic seizures (ANOVA/Bonferroni's test), suggesting the involvement of opioid peptides in this action. In the electroshock model no reversal of the anticonvulsant effect of dipyrone by naloxone (5 mg/kg, sc) was demonstrable. The acute (120 mg/kg, ip) and chronic (25 mg/kg, ip, twice a day/4 days) administration of L-NOARG did not reverse the anticonvulsant action of dipyrone in the audiogenic seizure model, suggesting that the nitric oxide pathway does not participate in such effect. Indomethacin (10, 20 and 30 mg/kg, ip) used for comparison had no anticonvulsant effect in the audiogenic seizure model. In conclusion, opioid peptides but not nitric oxide seem to be involved in the anticonvulsant action of dipyrone in audiogenic seizures.

Trace metals are involved in the mechanisms of CNS excitability, including epilepsy. In this study, atomic absorption spectrophotometry was used to determine concentrations of Mg(2+), Cu(2+) and Zn(2+) in plasma (microg/ml) and hair (microg/g) samples. Differential profiles of trace metals were detected in rats displaying three different kinds of seizures, i.e. acute audiogenic seizures (generalized tonic-clonic type GTC) and audiogenic kindling (limbic type; LS) in Wistar Audiogenic Rats (WARs) and electroshock-induced seizures (ES) in Wistar non-epileptic rats (resistant). Significantly lower Zn(2+) concentrations were observed in the plasma of WARs (0.80+/-0.02) compared with resistants (0.89+/-0.03) in the basal (non-seizing) condition. After GTC, WARs showed lower Zn(2+) levels (0.64+/-0.12) while both Mg(2+) (12.56+/-1.51) and Cu(2+) (0.81+/-0.14) were higher than in non-seizing WARs. After ES-induced seizures only Mg(2+) changed, being higher than in the basal condition (11.78+/-2.25 and 8.90+/-0.95). In hair, basal levels of Mg(2+) and Cu(2+) (192.49+/-36.73 and 13.33+/-1.76) were higher whereas Zn(2+) (136.53+/-15.67) was lower in WARs than in resistants. WARs submitted to 0, 3 and 25 stimuli presented higher Mg(2+) concentrations as the number of stimuli increased. In animals receiving the same number of stimuli, Zn(2+) levels were higher for animals displaying GTC (151.09+/-5.53) than those displaying LS (128.07+/-8.51). In conclusion, seizure type (limbic or generalized tonic-clonic) and number of stimuli seem to be the determinant factors for changes in Zn(2+) and Mg(2+) levels, respectively.

The convulsions of approximately 25% of epileptics are inadequately controlled by currently available medication; therefore the preparation of new antiepileptic drugs is of great interest. Aryl semicarbazones can be considered a new class of compounds presenting anticonvulsant activity. In addition, they can be orally administered and are more active as anticonvulsants than mephenytoin or phenobarbital. However, one disadvantage of these compounds is their low water solubility. As a strategy to circumvent this problem, a 1:1 inclusion compound of benzaldehyde semicarbazone (BS) and hydroxypropyl-beta-cyclodextrin (HP-beta-CD) was prepared and characterized. The anticonvulsant activities of the free semicarbazone and of the inclusion compound were evaluated in rats using the maximum electroshock and audiogenic seizures screenings. In both tests the minimum dose of compound necessary to produce activity decreases from 100mg/kg for the free semicarbazone to 35 mg/kg for the inclusion compound, indicating a significant increase in the bio-availability of the drug.

Purpose Cardiac dysfunction is one of the possible causes of sudden unexpected death in epilepsy (SUDEP). Therefore, the objective of this study was to evaluate cardiac and electrocardiographic parameters in rats with audiogenic epileptic seizures (WAR – Wistar audiogenic rats). Methods In vivo arterial pressure, heart rate (HR), autonomic tone and electrocardiography (ECG) were measured in awake animals in order to examine cardiac function and rhythm. Ex vivo , the Langendorff technique was used to analyze the cardiac function and the severity of reperfusion arrhythmias. In vitro , confocal microscopy was used to evaluate calcium transient parameters of isolated ventricular cardiomyocytes. Results In vivo autonomic tone evaluation revealed enhanced sympathetic activity, changes in cardiac function with increased systolic arterial pressure and higher basal HR in WAR. In addition, ECG analysis demonstrated electrical alterations with prolongation of the QT interval and QRS complex in these animals. Ex vivo , we observed a decrease in systolic tone and HR and an increase in the duration of ischemia/reperfusion arrhythmias in WAR. Moreover, intracellular Ca 2+ handling analysis revealed an increase in the peak of calcium and calcium transient decay in audiogenic rats. Treatment with atenolol (β1-adrenergic antagonist) normalized the systolic tone, reduced cardiac hypertrophy and the associated increase in the susceptibility to reperfusion arrhythmias observed in WAR. Conclusion We present evidence that chronic disturbances in sympathetic tone in WAR cause increases the risk to life-threatening arrhythmias. Our results support a relationship between seizures, cardiac dysfunction and cardiac arrhythmias, which may contribute to the occurrence of SUDEP.

O objetivo desse trabalho foi investigar os efeitos do peptídeo natriurético atrial (ANP) sobre a susceptibilidade a crises audiogênica e induzida por pentilenotetrazol (PTZ). Foi avaliada a relação entre a susceptibilidade à crise audiogênica e o ANP. Ratos Wistar e WistarAudiogenic Rats (WAR) foram eutanasiados por decapitação e as concentrações de ANP no plasma e átrios foram determinadas por radioimunoensaio. O grupo WAR apresentou maior concentração de ANP no plasma e átrios. A expressão do gene para ANP foi determinadapela técnica de RT-PCR em receptores do tipo A e C, no rim. Não houve diferença entre os grupos para a expressão relativa do RNAm para o receptor do tipo A. Porém, o grupo WAR apresentou maior expressão relativa do RNAm para o receptor do tipo C. O próximo passofoi verificar se o ANP diretamente favoreceria a excitabilidade neuronal no modelo PTZ. Wistar machos receberam agudamente 2 L (icv) de salina (0,9%) ou diferentes doses de ANP (9,8 ; 98 ; 326,5 pmol/animal). O mesmo tratamento foi repetido na presença da isatina. Após o tratamento, os animais receberam PTZ e foi avaliado o limiar de crise. Nenhuma diferença foi observada entre os tratamentos. Como o ANP não favoreceu a excitabilidade neuronal no modelo de crise induzida por PTZ foram investigados as relações entre os parâmetros que controlam o balanço hidroeletrolítico e a excitabilidade neuronal no modelode crise audiogênica. Ratos Wistar e WAR foram colocados em gaiolas metabólicas. Durante 16 dias os animais receberam água ad libitum. Nesse período, ratos WAR ingeriram maior volume de água, excretaram maior volume de urina, com menor osmolalidade e maior quantidade de sódio e apresentaram maior taxa de filtração glomerular. Não houve diferença nas concentrações plasmáticas de sódio, potássio e osmolalidade e na depuração de água livre. Como não houve diferença nos parâmetros do balanço hidroeletrolítico que indiretamente influenciam a excitabilidade neuronal, a hipótese seguinte foi avaliar os efeitos do ANP na atividade do eixo hipotálamo-hipofisário sobre a homeostase. Os ratos WAR foram submetidos à privação de água por um período de 72 horas. Após a eutanásia foram quantificadas as concentrações de ANP no plasma e nos átrios, a expressão gênica do ANP em receptores do tipo A e C no rim, as concentrações de sódio e osmolalidade no plasma. A privação de água promoveu redução nas concentrações plasmáticas e atrais de ANP. Mesmos desidratados ratos WAR apresentaram maior concentração de ANP no plasma eno átrio. Porém, todas as diferenças observadas anteriormente em relação aos parâmetros do balanço hidroeletrolítico foram extintas. Em síntese, há relação entre a susceptibilidade à crise audiogênica e o ANP. Mas, essa associação não está relacionada com os parâmetrosdo balanço hidroeletrolítico que favorecem a excitabilidade neuronal. É um mecanismo para compensar a maior ingestão de água. A ativação das estruturas hipotalâmicas que participam do balanço hidroeletrolítico mostrou que o modelo de crise audiogênica apresenta uma alteração comportamental em relação à ingestão de água. Além disso, oANP não exerceu efeitos pro ou anticonvulsivante em crises induzidas por PTZ. The aim of this study was to investigate the effects of atrial natriuretic peptide (ANP) on the susceptibility to audiogenic seizures and those induced by pentylenetetrazole (PTZ). The relationship between ANP and susceptibility to audiogenic seizure was evaluated. Wistar rats and Wistar Audiogenic Rats (WAR) were sacrificed and the concentrations of ANP in plasma and atria were determined by radioimmunoassay. The WAR group was found to have a higher concentration of ANP in plasma and in the atrium. The expression of the gene for ANP was determined by RT-PCR for receptor type A and C in the kidney. There was nodifference between groups for the relative expression of mRNA for the type A receptor. However, the group WAR was found to have a higher relative expression of mRNA the type C receptor. The next step was to determine whether ANP directly favored neuronal excitability in the PTZ model. Wistar rats acutely received 2 L (icv) of saline (0.9%) ordifferent doses of ANP (9.8, 98, 326.5 pmol / animal). The same treatment was repeated in the presence of isatin. After treatment, the animals received PTZ and the seizure threshold was evaluated. No difference was observed between treatments. As the ANP did not favorthe neuronal excitability in the model of seizure induced by PTZ, the relationship between the parameters that control the fluid balance and neuronal excitability in the model of audiogenic seizure was investigated. WAR and Wistar rats were placed in metabolic cages. For 16 daysthe animals received water ad libitum. During this period, WAR rats had higher intake of drinking water excreted higher urine volume with lower osmolality and increased amount of sodium and were found to have a higher glomerular filtration rate. There was no difference in plasma concentrations of sodium, potassium and osmolality and free water clearance. Since there was no difference in the parameters of fluid balance that indirectly influences neuronal excitability, the next hypothesis was to evaluate the effects of ANP on the activity on the hypothalamic -pituitary homeostasis. WAR rats underwent water deprivation for a period of 72 hours. After the sacrifice, the concentrations of ANP were quantified in plasma and atrium, the expression of the gene for ANP in the receptors of type A and C in the kidney and sodium and plasma osmolality. The water deprivation promoted a reduction in plasma ANP and in the atrium. However, all previously differences observed in relation to the parameters of fluid balance were extinguished. In short, there is a relationship between susceptibility to audiogenic seizure and the ANP. However this association is not related to the parameters of fluid balance favoring neuronal excitability. It is a mechanism to compensate the higherintake of drinking water. The activation of the hypothalamic structures involved in fluid balance showed that the model of audiogenic seizure presents a behavioral change. In addition, the ANP has no effect pro or anticonvulsant on PTZ-induced seizures.

Apesar da disponibilidade de vários fármacos anticonvulsivantes, um terço dos pacientes com epilepsia continuam a apresentar crises. Em certos casos, os fármacos disponíveis são eficazes, mas promovem efeitos colaterais e toxicidade incompatíveis com a manutenção do tratamento. O Bromo Benzaldeído Semicarbazona (BrBS) é um composto da classe das semicarbazonas, o qual apresenta boa eficácia terapêutica e baixa toxicidade. O objetivo desse trabalho foi investigar a atividade anticonvulsivante do BrBS no modelo de crise audiogênica (CA) em ratas wistar audiogênicas (WAR), em crises induzidas por pentilenotetrazol (PTZ) em ratos Wistar e em cães sem raça definida. No modelo de CA, foram analisados os parâmetros de índice de gravidade (IS), latência e porcentagem de ocorrência de primeira corrida (C1) e crise generalizada tônica clônica (CVT). No modelo de PTZ em ratos, foram analisados os limiares de PTZ para ocorrência dos comportamentos abalo mioclônico (AM), mioclonia parcial (MP) e crise generalizada tônico-clônica (CVT). No modelo de PTZ em cães foram analisados os limiares de PTZ para ocorrência dos comportamentos mioclonia parcial (MP) e abalo mioclônico generalizado (AMG). No modelo de CA em WARs, na dose máxima (400 mg/kg), o BrBS bloqueou todos os comportamentos relacionados a crise (IS=0) para todos os animais sem apresentar efeitos colaterais evidentes. A porcentagem de animais que apresentou o comportamento CVT diminuiu em 50 % nas doses de 100 e 150 mg/kg em relação ao controle. A porcentagem de animais que apresentou C1 diminuiu9 em 43 % na dose de 200 mg/kg, acompanhado do aumento da sua latência em relação ao controle. No modelo de PTZ em ratos, o BrBS apresentou um modelo de regressão quadrática na curva dose-resposta dos três comportamentos avaliados. Não foi observado efeito pró-convulsivante. As doses 150 e 200 mg/kg foram eficazes no AM. A dose de 200 mg/kg foi eficaz no MP e CVT, com decréscimo significativo na dose de 400 mg/kg para AM e CVT. O cão mostrou ser um modelo estável para o estudo de crise convulsiva por PTZ. No entanto, o BrBS não foi eficaz na crise induzida por PTZ em cão. Foi observado a ocorrência de dois grupos de animais com respostasdistintas ao BrBS. Isso sugere a existência de animais com diferentesrespostas farmacológicas à crise convulsiva. Podemos concluir que o BrBS, apresentou ótima eficácia no modelo de crise generalizada em WARs, moderada atividade, dependente de dose, no modelo de crises parciais e generalizadas de PTZ em ratos e ausência de efeito no modelo de crises parciais e generalizadas de PTZ em cães. Despite the availability of wide range of anticonvulsant drugs, at least 25% of patients continue to have seizures. Furthermore, among those in whom seizures are effectively inhibited, substantial number of patients experience persistent and undesirable effects of these drugs. BrBS is a semicarbazone compound that has shown to possess excellent anticonvulsant activity in rats, besides their low or absent neurotoxicity. The objective of this present study was examine the ability of BrBS to prevent audiogenic seizures (AS) in Wistar Audiogenic Rats (WAR) and seizures induced by Pentilenetetrazole (PTZ) in Wistar rats and mongrel dogs. The behaviors observed in the WARs were severity index (IS), latency to the first wild running episode (FR), latency to the tonic-clonic phase (TCS) and the presence or absence of these seizurecomponents. The endpoints used to evaluate the threshold for PTZ in ratswas the first myoclonic twitch (MT), partial clonus (PC) and generalized tonicclonic seizure (TCS). In dogs, PTZ model was evaluated by the threshold for generalized myoclonic twitch (MT) and partial clonus (PC). In the AS, the maximum dose of BrBS tested (400 mg/kg) blocked all the seizure components (IS = 0) for all animals and no adverse effect was noted. At the dose of 200 mg/kg, BrBS suppress the FR in 43% of rats and only 28 % still showed the TCS. The doses of 100 and 150 mg/kg, BrBS suppressed 50 % of the TCS in the rats. In the PTZ model in rats a restricted dose response was found for the three behaviors tested. No proconvulsant properties were observed. At the doses of 150 and 200 mg/kg, BrBS effectively increased the threshold for MT. The effective dose for PC and TCS was 200 mg/kg. The 11 anticonvulsant effect decreased at 400 mg/kg for MT and TCS components.The mongrel dogs showed to be a suitable model for PTZ seizures studies. However, BrBS showed no anticonvulsant efficacy in this model. Two groups of animals were characterized in their responses to BrBS anticonvulsant activity. These results suggest the existence of animals with individual differences in pharmacological anticonvulsant responses. In conclusion, this study showed the pharmacology efficacy of BrBS against AS in WAR model, against partial and generalized seizure in PTZ model in rats and no activity against PTZ model in dogs.

O sistema circulatório é essencial para a manutenção da homeostase do organismo. A regulação neural do sistema cardiovascular envolve a ativação de vários grupos de sensores localizados na periferia gerando informações que são enviadas para o sistema nervoso central, e a modulação dessa informação no SNC com conseqüente modulação do sistema nervoso autônomo. Entre os sensores periféricos podemos destacar os barorreceptores arteriais, receptores cardiopulmonares e os quimiorreceptores periféricos. A área A5 é uma região localizada no tronco encefálico, mais especificamente na ponte, constituída por um grupamento de neurônios noradrenérgicos. Estudos neuroanatômicos identificaram conexões da área A5 com várias áreas envolvidas no controle cardiovascular. Estudo realizado em nosso laboratório demonstrou que a estimulação da área A5 promove resposta pressora e taquicárdica e ainda atribuiu aos neurônios noradrenérgicos dessa área um papel essencial ao componente pressor do quimiorreflexo em ratos não anestesiados. Estudos anteriores demonstraram que alterações dos níveis de pressão arterial modificam a atividade espontânea dos neurônios da área A5, modificações estas dependentes da integridade das vias aferentes barorreceptoras. No entanto o papel da área A5 na integração das respostas barorreflexas em ratos não anestesiado permanece por ser melhor investigado. Dessa forma procuramos nesse trabalho avaliar a neurotransmissão do componente simpato-excitatório do quimiorreflexo na área A5, bem como avaliar a participação desta área na regulação do componente cardíaco do barorreflexo, em ratos não-anestesiados. Em nossos resultados observamos que o antagonista glutamatérgico ionotrópico ácido kinurênico, assim como o antagonista glutamatérgico metabotrópico MCPG, não alteraram as respostas cardiovasculares induzidas pela estimulação do 13 quimiorreflexo. Também observamos que o bloqueio dos receptores gabaérgicos da área A5 não resultou em alteração da pressão arterial basal, bem como não alterou a resposta pressora do quimiorreflexo, sugerindo que a neurotransmissão da resposta simpato-excitatória deste reflexo na área A5 não ocorre por desinibição de seus neurônios. Outro achado do presente estudo indica que a sensibilidade da bradicardia bem como da taquicardia barorreflexa não foram alteradas após a inibição da área A5. O conjunto destes resultados indica que o neurotransmissor L-glutamato, não está envolvido na integração do componente simpato-excitatório da resposta quimiorreflexa. Em relação ao barorreflexo concluímos que a área A5 não participa de forma importante da modulação do controle barorreflexo da freqüência cardíaca. The circulatory system is essential for the maintenance of body homeostasis. Neural regulation of the cardiovascular system involves the activation of several groups of peripheral sensors that generates the information to central nervous system, with consequent modulation of the autonomic nervous system. Among the peripheral sensors the arterial baroreceptors, the cardiopulmonary receptors and the peripheral chemoreceptors can be highlighted. The A5 area is a region localized in the brainstem, more precisely in the pons, and is comprised of noradrenergic neurons. Neuroanatomy studies have identified connections between the A5 area and several areas involved in cardiovascular control. Previous studies conducted in our laboratory demonstrated that stimulation of the A5 area produced large pressor response and tachycardia. Additionally, this study demonstrated the essential role of this area in the chemoreflex pressor component in unanesthetized rats. Other studies have demonstrated that alterations in arterial pressure modified the spontaneous activity of the A5 area neurons, in within modifications depends of baroreceptor afferent input integrity. However, the role of the A5 area in the integration of baroreflex responses in unanesthetized rats still needs to be further investigated.Moreover, we evaluated the neurotransmission of the chemoreflex sympatho-excitatory component within the A5 area, as well, we evaluated the participation of this area in the cardiac baroreflex regulation, in unanesthetized rats. In our findings, both the ionotropic glutamatergic antagonist kynurenic acid, as well as the metabotropic glutamatergic antagonist MCPG, did not altered cardiovascular responses induced by chemoreflex stimulation. We also demonstrated that the blockade of gabaergic receptors of the A5 area did not result in alterations in basal arterial pressure. Additionally, this blockade did not alter the chemoreflex pressor response, suggesting that the sympatho-excitatory neurotransmission in the 16 A5 area does not occur through disinhibition of these neurons. Other findings from the present study indicate that the sensitivity of baroreflex bradycardia as well as the baroreflex tachycardia was not altered after the inhibition of the A5 area. Together these results indicate that the L-glutamate neurotransmitter was not involved in the integration of the sympatho-excitatory component of the chemoreflex response. Our data also showed that the A5 area does not participate in baroreflex control of heart rate.