RESUMO
Drug-induced convulsion is a serious concern in drug development, such that the convulsion liability of drug candidates must be evaluated in preclinical safety studies. However, information on the differences among species regarding their sensitivity to convulsions induced by convulsant drugs in humans remains limited. Here, we selected 11 test articles from several pharmacological classes and compared the sensitivities of three types of laboratory animal to convulsion. All 11 test articles were examined in mice via intraperitoneal injection and in rats via intravenous bolus; and 6 of the 11 test articles, selected mainly based on availabilities of data on drug plasma concentrations in humans at convulsion, were examined in non-human primates (NHPs) via intravenous infusion. Plasma concentrations of the test articles shortly after convulsion onset or 5 min after administration were measured. All 11 articles tested in mice, 10 of 11 articles tested in rats, and all 6 articles tested in NHPs induced convulsion with premonitory signs. Although there was a general tendency that rats and NHPs exhibited convulsions at lower plasma drug concentrations than did mice, the plasma concentrations at convulsion onset were generally comparable, within 3-fold differences, across the animal species. We conclude that the mice, rats, and NHPs examined in the present study generally showed similar sensitivities to convulsion induced by the test articles. Thus, each of these laboratory animals can be used for the assessment of convulsion risk in the early stages of drug development, depending on throughput, cost, and test article-specific requirements.
Assuntos
Avaliação Pré-Clínica de Medicamentos , Convulsões , Especificidade da Espécie , Animais , Convulsões/induzido quimicamente , Medição de Risco , Camundongos , Ratos , Masculino , Convulsivantes/toxicidade , Humanos , Animais de Laboratório , Injeções IntraperitoneaisRESUMO
INTRODUCTION: Excessive anxiety is a mental disorder, and its treatment involves the use of benzodiazepines, a class of drugs that enhance the effects of the neurotransmitter gamma-aminobutyric acid (GABA) at the GABAA receptor. Anxiety disorders are frequent comorbidities in patients with epilepsy, and it has been speculated that anxiety disorders and epileptic seizures share common neurobiological mechanisms. However, conflicting results regarding anxiolytic and anxiogenic effects have been reported in animal models of epilepsy induced by pentylenetetrazole (PTZ) injections, and the causes of this discrepancy are unknown. We hypothesized that anxiety-like behaviors would change dynamically according to the changes in epilepsy susceptibility that occur during the PTZ kindling process. Therefore, we attempted to change anxiety-like behaviors bidirectionally depending on the number of PTZ injections. METHODS: Adult male rats were injected with PTZ 20 times every other day, and stages of seizure onset were classified according to the Racine staging system. Anxiety-like behaviors were measured after 10 and 20 injections. The control group was injected with an equal volume of saline solution. Anxiety-like behaviors were investigated using the open-field, light/dark transition, elevated plus maze, and social interaction tests. RESULTS: Bimodal changes in seizure stage were observed in response to PTZ kindling. The increase in the seizure stage was transiently suppressed after 10 injections, and this decrease in epileptic sensitivity disappeared after 20 injections. However, none of the rats reached a fully kindled state after 20 PTZ injections. After 10 PTZ injections, anxiety-like behaviors decreased compared with those of the control group in the open field, light/dark transition, and elevated plus-maze tests. The anxiolytic effects correlated with the seizure stage in individual rats. After 20 PTZ injections, anxiety-like behaviors returned to control levels. CONCLUSION: PTZ kindling induced bimodal changes in the seizure stage. Anxiety-like behaviors decreased with transient decrease in epileptic sensitivity and returned to control levels with the disappearance of these states. These findings suggest a common neurobiological mechanism underlying anxiety disorders and epileptic seizures. In addition, the discrepancy in the previous studies, in which anxiety levels increase or decrease in PTZ-kindled animals, may be due to examination at different phases of the kindling process.
Assuntos
Ansiedade , Convulsivantes , Modelos Animais de Doenças , Excitação Neurológica , Pentilenotetrazol , Convulsões , Animais , Masculino , Excitação Neurológica/efeitos dos fármacos , Ansiedade/etiologia , Ansiedade/induzido quimicamente , Convulsões/induzido quimicamente , Convulsões/psicologia , Convulsivantes/toxicidade , Ratos , Ratos Sprague-Dawley , Aprendizagem em Labirinto/efeitos dos fármacos , Comportamento Exploratório/efeitos dos fármacos , Teste de Campo Aberto , Interação Social/efeitos dos fármacosRESUMO
Seizures occur when there is a hyper-excitation of the outer layer of the brain, with subsequent excessive synchrony in a group of neurons. According to the World Health Organization (WHO), an estimated 50 million people are affected by this disease, a third of whom are resistant to the treatments available on the market. Caffeine (1,3,7-trimethylxanthine), which belongs to the purine alkaloid family, is the most widely consumed psychoactive drug in the world. It is ingested by people through drinks containing this substance, such as coffee, and as an adjuvant in analgesic therapy with non-steroidal antiflammatory drugs. The present study evaluated the electrocorticographic changes observed in the hippocampus of Wistar rats subjected to acute doses of caffeine (150â¯mg/kg i.p), which represents a toxic dose of caffeine corresponding to an estimated acute intake of more than 12 cups of coffee to record its convulsant activity. Our results showed, for the first time, that the administration of high doses of caffeine (150â¯mg/kg i.p.) in rats caused an increase in the spectral distribution of power in all frequency bands and suggested the appearance of periods of ictal and interictal peaks in the electrocorticogram (ECog). We have also shown that the anticonvulsants phenytoin, diazepam and phenobarbital have a satisfactory response when associated with caffeine.
Assuntos
Anticonvulsivantes , Cafeína , Convulsivantes , Hipocampo , Ratos Wistar , Convulsões , Animais , Cafeína/farmacologia , Cafeína/administração & dosagem , Hipocampo/efeitos dos fármacos , Masculino , Convulsões/fisiopatologia , Convulsões/induzido quimicamente , Convulsões/tratamento farmacológico , Anticonvulsivantes/farmacologia , Anticonvulsivantes/administração & dosagem , Convulsivantes/farmacologia , Ratos , Eletrocorticografia , Relação Dose-Resposta a DrogaRESUMO
Epilepsy, a chronic neurological disorder characterized by recurrent unprovoked seizures, presents a substantial challenge in approximately one-third of cases exhibiting resistance to conventional pharmacological treatments. This study investigated the effect of 4-allyl-2,6-dimethoxyphenol, a phenolic compound derived from various natural sources, in different models of induced seizures and its impact on animal electroencephalographic (EEG) recordings. Adult male Swiss albino mice were pre-treated (i.p.) with a dose curve of 4-allyl-2,6-dimethoxyphenol (50, 100, or 200â¯mg/kg), its vehicle (Tween), or standard antiepileptic drug (Diazepam; or Phenytoin). Subsequently, the mice were subjected to different seizure-inducing models - pentylenetetrazole (PTZ), 3-mercaptopropionic acid (3-MPA), pilocarpine (PILO), or maximal electroshock seizure (MES). EEG analysis was performed on other animals surgically implanted with electrodes to evaluate brain activity. Significant results revealed that animals treated with 4-allyl-2,6-dimethoxyphenol exhibited increased latency to the first myoclonic jerk in the PTZ and PILO models; prolonged latency to the first tonic-clonic seizure in the PTZ, 3-MPA, and PILO models; reduced total duration of tonic-clonic seizures in the PTZ and PILO models; decreased intensity of convulsive seizures in the PTZ and 3-MPA models; and diminished mortality in the 3-MPA, PILO, and MES models. EEG analysis indicated an increase in the percentage of total power attributed to beta waves following 4-allyl-2,6-dimethoxyphenol administration. Notably, the substance protected from behavioral and electrographic seizures in the PTZ model, preventing increases in the average amplitude of recording signals while also inducing an increase in the participation of theta and gamma waves. These findings suggest promising outcomes for the tested phenolic compound across diverse pre-clinical seizure models, highlighting the need for further comprehensive studies to elucidate its underlying mechanisms and validate its clinical relevance in epilepsy management.
Assuntos
Anticonvulsivantes , Modelos Animais de Doenças , Eletroencefalografia , Eletrochoque , Pentilenotetrazol , Convulsões , Animais , Masculino , Convulsões/tratamento farmacológico , Convulsões/induzido quimicamente , Convulsões/fisiopatologia , Camundongos , Anticonvulsivantes/farmacologia , Pentilenotetrazol/toxicidade , Eletroencefalografia/efeitos dos fármacos , Anisóis/farmacologia , Relação Dose-Resposta a Droga , Pilocarpina/toxicidade , Encéfalo/efeitos dos fármacos , Encéfalo/fisiopatologia , Ácido 3-Mercaptopropiônico/farmacologia , Convulsivantes/toxicidadeRESUMO
Abnormal patterns of brain connectivity characterize epilepsy. However, little is known about these patterns during the stages preceding a seizure induced by pentylenetetrazol (PTZ). To investigate brain connectivity in male Wistar rats during the preictal phase of PTZ-induced seizures (60 mg/kg), we recorded local field potentials in the primary motor (M1) cortex, the ventral anterior (VA) nucleus of the thalamus, the hippocampal CA1 area, and the dentate gyrus (DG) during the baseline period and after PTZ administration. While there were no changes in power density between the baseline and preictal periods, we observed an increase in directional functional connectivity in theta from the hippocampal formation to M1 and VA, as well as in middle gamma from DG to CA1 and from CA1 to M1, and also in slow gamma from M1 to CA1. These findings are supported by increased phase coherence between DG-M1 in theta and CA1-M1 in middle gamma, as well as enhanced phase-amplitude coupling of delta-middle gamma in M1 and delta-fast gamma in CA1. Interestingly, we also noted a slight decrease in phase synchrony between CA1 and VA in slow gamma. Together, these results demonstrate increased functional connectivity between brain regions during the PTZ-induced preictal period, with this increase being particularly driven by the hippocampal formation.
Assuntos
Encéfalo , Pentilenotetrazol , Ratos Wistar , Convulsões , Animais , Pentilenotetrazol/farmacologia , Masculino , Convulsões/induzido quimicamente , Convulsões/fisiopatologia , Encéfalo/efeitos dos fármacos , Encéfalo/fisiopatologia , Ratos , Vias Neurais/fisiopatologia , Vias Neurais/efeitos dos fármacos , Modelos Animais de Doenças , Eletroencefalografia/métodos , Região CA1 Hipocampal/efeitos dos fármacos , Região CA1 Hipocampal/fisiopatologia , Convulsivantes/toxicidade , Convulsivantes/farmacologia , Ondas Encefálicas/efeitos dos fármacos , Ondas Encefálicas/fisiologia , Córtex Motor/efeitos dos fármacos , Córtex Motor/fisiopatologiaRESUMO
GABA modulators such as phenobarbital (PB) and sodium channel blockers such as phenytoin (PHT) have long been the mainstay of pharmacotherapy for the epilepsies. In the context of neonatal seizures, both PB and PHT display incomplete clinical efficacy. Moreover, in animal models, neonatal exposure to these medications result in neurodegeneration raising concerns about safety. Cenobamate, a more recently approved medication, displays unique pharmacology as it is both a positive allosteric modulator of GABA-A receptors, and a voltage-gated sodium channel blocker. While cenobamate is approved for adult use, its efficacy and safety profile against neonatal seizures is poorly understood. To address this gap, we assessed the efficacy and safety of cenobamate in immature rodents. Postnatal day (P)7 rat pups were pretreated with cenobamate and challenged with the chemoconvulsant pentylenetetrazole (PTZ) to screen for anti-seizure effects. In a separate experiment, P7 rats were treated with cenobamate, and brains were processed to assess induction of cell death. Cenobamate displays dose-dependent anti-seizure efficacy in neonatal rats. Unlike PHB and PHT, it does not induce neurotoxicity in P7 rats. Thus, cenobamate may be effective at treating neonatal seizures while avoiding unwanted neurotoxic side effects such as cell death.
Assuntos
Animais Recém-Nascidos , Anticonvulsivantes , Carbamatos , Morte Celular , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Ratos Sprague-Dawley , Convulsões , Animais , Convulsões/induzido quimicamente , Convulsões/tratamento farmacológico , Anticonvulsivantes/farmacologia , Ratos , Morte Celular/efeitos dos fármacos , Carbamatos/farmacologia , Carbamatos/uso terapêutico , Clorofenóis/farmacologia , Pentilenotetrazol/toxicidade , Masculino , Feminino , Convulsivantes/toxicidade , Encéfalo/efeitos dos fármacos , TetrazóisRESUMO
Zebrafish larvae exposed to chemoconvulsants show behavioral seizures and electrographic abnormalities similar to the other mammalian models, making it a potential tool in epilepsy research. During the embryonic stage, zebrafish remains transparent which enables real-time developmental detection and in-situ gene/protein expression. However, pigmentation during the larval stage restricts transparency. Phenylthiourea (1-phenyl-2-thiourea; PTU) is a commonly used pigmentation blocker that maintains larval transparency. It is widely used along with chemoconvulsants to study in situ expressions in epileptic larvae, however, its effect on seizures largely remains unknown. Therefore, in the present study, the effect of PTU-mediated depigmentation was studied on pentylenetetrazol (PTZ)-induced seizures in zebrafish larvae. After spawning, the fish embryos were subjected to standard depigmentation protocol using 0.13 mM PTU. At 7-days post fertilization seizures were induced using 8 mM PTZ. PTU exposure significantly reduced PTZ-mediated hyperactive responses indicated by decreased distance travelled and swimming velocity of the larvae. Furthermore, PTU-exposed depigmented larvae also showed an increase in the latency to the onset of PTZ-mediated clonic-like seizures. The results concluded that PTU depigmentation protocol reduces the seizurogenic response of PTZ, hence its usage for imaging zebrafish larvae must be carefully monitored to avoid erroneous results.
Assuntos
Larva , Pentilenotetrazol , Feniltioureia , Convulsões , Peixe-Zebra , Animais , Peixe-Zebra/embriologia , Larva/efeitos dos fármacos , Feniltioureia/farmacologia , Convulsões/induzido quimicamente , Pigmentação/efeitos dos fármacos , Modelos Animais de Doenças , ConvulsivantesRESUMO
Neuroinflammation during the neonatal period has been linked to disorders such as autism and epilepsy. In this study, we investigated the early life behavioral consequences of a single injection of lipopolysaccharide (LPS) at postnatal day 10 (PD10) in mice. To assess deficits in communication, we performed the isolation-induced ultrasonic vocalizations (USVs) test at PD12. To determine if early life immune stimulus could alter seizure susceptibility, latency to flurothyl-induced generalized seizures was measured at 4 hours (hrs), 2 days, or 5 days after LPS injections. LPS had a sex-dependent effect on USV number. LPS-treated male mice presented significantly fewer USVs than LPS-treated female mice. However, the number of calls did not significantly differ between control and LPS for either sex. In male mice, we found that downward, short, and composite calls were significantly more prevalent in the LPS treatment group, while upward, chevron, and complex calls were less prevalent than in controls (p < 0.05). Female mice that received LPS presented a significantly higher proportion of short, frequency steps, two-syllable, and composite calls in their repertoire when compared with female control mice (p < 0.05). Seizure latency was not altered by early-life inflammation at any of the time points measured. Our findings suggest that early-life immune stimulation at PD10 disrupts vocal development but does not alter the susceptibility to flurothyl-induced seizures during the neonatal period. Additionally, the effect of inflammation in the disruption of vocalization is sex-dependent.
Assuntos
Animais Recém-Nascidos , Lipopolissacarídeos , Convulsões , Caracteres Sexuais , Vocalização Animal , Animais , Feminino , Vocalização Animal/efeitos dos fármacos , Vocalização Animal/fisiologia , Camundongos , Masculino , Lipopolissacarídeos/farmacologia , Lipopolissacarídeos/toxicidade , Convulsões/induzido quimicamente , Flurotila/toxicidade , Suscetibilidade a Doenças/induzido quimicamente , Convulsivantes/toxicidade , Modelos Animais de DoençasRESUMO
The voltage-gated calcium channel subunit α2δ-2 controls calcium-dependent signaling in neurons, and loss of this subunit causes epilepsy in both mice and humans. To determine whether mice without α2δ-2 demonstrate hippocampal activation or histopathological changes associated with seizure activity, we measured expression of the activity-dependent gene c-fos and various histopathological correlates of temporal lobe epilepsy (TLE) in hippocampal tissue from wild-type (WT) and α2δ-2 knock-out (CACNA2D2 KO) mice using immunohistochemical staining and confocal microscopy. Both genotypes demonstrated similarly sparse c-fos and ΔFosB expressions within the hippocampal dentate granule cell layer (GCL) at baseline, consistent with no difference in basal activity of granule cells between genotypes. Surprisingly, when mice were assayed 1â h after handling-associated convulsions, KO mice had fewer c-fos-positive cells but dramatically increased ΔFosB expression in the dentate gyrus compared with WT mice. After administration of a subthreshold pentylenetetrazol dose, however, KO mice dentate had significantly more c-fos expression compared with WT mice. Other histopathological markers of TLE in these mice, including markers of neurogenesis, glial activation, and mossy fiber sprouting, were similar between WT and KO mice, apart from a small but statistically significant increase in hilar mossy cell density, opposite to what is typically found in mice with TLE. This suggests that the differences in seizure-associated dentate gyrus function in the absence of α2δ-2 protein are likely due to altered functional properties of the network without associated structural changes in the hippocampus at the typical age of seizure onset.
Assuntos
Canais de Cálcio , Hipocampo , Camundongos Knockout , Proteínas Proto-Oncogênicas c-fos , Convulsões , Animais , Camundongos , Canais de Cálcio/metabolismo , Canais de Cálcio/genética , Convulsivantes/toxicidade , Modelos Animais de Doenças , Hipocampo/metabolismo , Hipocampo/patologia , Camundongos Endogâmicos C57BL , Neurônios/metabolismo , Neurônios/patologia , Pentilenotetrazol , Proteínas Proto-Oncogênicas c-fos/metabolismo , Convulsões/metabolismo , Convulsões/genética , Convulsões/patologiaRESUMO
Natural compounds are increasingly being studied for their potential neuroprotective effects against inflammatory neurological diseases. Epilepsy is a common neurological disease associated with inflammatory processes, and around 30% of people with epilepsy do not respond to traditional treatments. Some flavonoids, when taken along with antiseizure medications can help reduce the likelihood of drug-resistant epilepsy. Baicalin, a plant-based compound, has been shown to possess pharmacological properties such as anti-inflammatory, neuroprotective, anticonvulsant, and antioxidant activities. In this study, we tested the effect of baicalin on an established model of pharmacologically induced seizure in zebrafish using measures of both locomotor behavior and calcium imaging of neuronal activity. The results of our study showed that, at the tested concentration, and contrary to other studies in rodents, baicalin did not have an anti-seizure effect in zebrafish larvae. However, given its known properties, other concentrations and approaches should be explored to determine if it could potentially have other beneficial effects, either alone or when administered in combination with classic antiseizure medications.
Assuntos
Cálcio , Flavonoides , Larva , Neurônios , Pentilenotetrazol , Convulsões , Peixe-Zebra , Animais , Flavonoides/farmacologia , Convulsões/tratamento farmacológico , Convulsões/induzido quimicamente , Larva/efeitos dos fármacos , Cálcio/metabolismo , Neurônios/efeitos dos fármacos , Modelos Animais de Doenças , Anticonvulsivantes/farmacologia , Relação Dose-Resposta a Droga , Convulsivantes/toxicidade , Locomoção/efeitos dos fármacos , Atividade Motora/efeitos dos fármacosRESUMO
Drug-induced convulsions are a major challenge to drug development because of the lack of reliable biomarkers. Using machine learning, our previous research indicated the potential use of an index derived from heart rate variability (HRV) analysis in non-human primates as a biomarker for convulsions induced by GABAA receptor antagonists. The present study aimed to explore the application of this methodology to other convulsants and evaluate its specificity by testing non-convulsants that affect the autonomic nervous system. Telemetry-implanted males were administered various convulsants (4-aminopyridine, bupropion, kainic acid, and ranolazine) at different doses. Electrocardiogram data gathered during the pre-dose period were employed as training data, and the convulsive potential was evaluated using HRV and multivariate statistical process control. Our findings show that the Q-statistic-derived convulsive index for 4-aminopyridine increased at doses lower than that of the convulsive dose. Increases were also observed for kainic acid and ranolazine at convulsive doses, whereas bupropion did not change the index up to the highest dose (1/3 of the convulsive dose). When the same analysis was applied to non-convulsants (atropine, atenolol, and clonidine), an increase in the index was noted. Thus, the index elevation appeared to correlate with or even predict alterations in autonomic nerve activity indices, implying that this method might be regarded as a sensitive index to fluctuations within the autonomic nervous system. Despite potential false positives, this methodology offers valuable insights into predicting drug-induced convulsions when the pharmacological profile is used to carefully choose a compound.
Assuntos
4-Aminopiridina , Frequência Cardíaca , Aprendizado de Máquina , Convulsões , Animais , Masculino , Convulsões/induzido quimicamente , Frequência Cardíaca/efeitos dos fármacos , 4-Aminopiridina/efeitos adversos , Ácido Caínico/toxicidade , Convulsivantes/toxicidade , Ranolazina , Bupropiona/toxicidade , Bupropiona/efeitos adversos , Eletrocardiografia/efeitos dos fármacos , Relação Dose-Resposta a Droga , Sistema Nervoso Autônomo/efeitos dos fármacos , Sistema Nervoso Autônomo/fisiopatologia , Telemetria , BiomarcadoresRESUMO
This study verified the effects of the natural compounds berberine and hesperidin on seizure development and cognitive impairment triggered by pentylenetetrazole (PTZ) in zebrafish. Adult animals were submitted to a training session in the inhibitory avoidance test and, after 10â¯minutes, they received an intraperitoneal injection of 25, 50, or 100â¯mg/kg berberine or 100 or 200â¯mg/kg hesperidin. After 30â¯minutes, the animals were exposed to 7.5â¯mM PTZ for 10â¯minutes. Animals were submitted to the test session 24â¯h after the training session to verify their cognitive performance. Zebrafish larvae were exposed to 100⯵M or 500⯵M berberine or 10⯵M or 50⯵M hesperidin for 30â¯minutes. After, larvae were exposed to PTZ and had the seizure development evaluated by latency to reach the seizure stages I, II, and III. Adult zebrafish pretreated with 50â¯mg/kg berberine showed a longer latency to reach stage III. Zebrafish larvae pretreated with 500⯵M berberine showed a longer latency to reach stages II and III. Hesperidin did not show any effect on seizure development both in larvae and adult zebrafish. Berberine and hesperidin pretreatments prevented the memory consolidation impairment provoked by PTZ-induced seizures. There were no changes in the distance traveled in adult zebrafish pretreated with berberine or hesperidin. In larval stage, berberine caused no changes in the distance traveled; however, hesperidin increased the locomotion. Our results reinforce the need for investigating new therapeutic alternatives for epilepsy and its comorbidities.
Assuntos
Aprendizagem da Esquiva , Berberina , Hesperidina , Pentilenotetrazol , Convulsões , Peixe-Zebra , Animais , Pentilenotetrazol/farmacologia , Berberina/farmacologia , Berberina/administração & dosagem , Hesperidina/farmacologia , Convulsões/induzido quimicamente , Convulsões/prevenção & controle , Aprendizagem da Esquiva/efeitos dos fármacos , Consolidação da Memória/efeitos dos fármacos , Transtornos da Memória/induzido quimicamente , Transtornos da Memória/prevenção & controle , Masculino , Modelos Animais de Doenças , Convulsivantes/farmacologia , Larva/efeitos dos fármacos , Relação Dose-Resposta a Droga , Anticonvulsivantes/farmacologiaRESUMO
Picrotoxin (PTX), a convulsant of plant origin, has been used in many studies as research tool. PTX is the open channel blocker of the GABAA receptor (GABAAR). Being in the pore, PTX initiates transfer of the channel to the closed state and thus it falls into the "trap". The consequence of this PTX trapping is so-called aftereffect, i.e. continuation of the blockade of the GABA-induced chloride current (IGABA) after removal of PTX from the external solution. The present work shows that the positive allosteric modulators (PAMs) of the GABAA receptor, allopregnanolone (Allo) and zolpidem (Zolp) as well as a high concentration of GABA shortened the PTX aftereffect. Experiments were carried out on isolated Purkinje neurons of the rat cerebellum using the whole-cell patch-clamp method. IGABA was induced by applications of 5 µM GABA (EC30) for 1 s with 30 s intervals. 50 µM PTX completely blocked IGABA, and recovery upon PTX washout occurred with a time constant (τrec) of 20.2 min. 1 µM Allo reduced the blocking effect of PTX by 30% and accelerated the recovery of IGABA by almost 10 times (τrec = 2.4 min). 0.5 µM Zolp did not change the IGABA block in the presence of PTX but accelerated the recovery of IGABA by more than 3 times (τrec = 5.6 min). Increasing the GABA concentration to 20 µM did not change the blocking effect of PTX, but accelerated recovery by 6 times (τrec = 3.3 min). The mechanism of the shortening of the PTX aftereffect is presumably the expansion of the GABAAR pore in the presence of PAMs and a high concentration of the agonist and, as a consequence, the escape of PTX from the "trap". The work describes new pharmacological properties of Allo and Zolp.
Assuntos
Convulsivantes , Receptores de GABA-A , Ratos , Animais , Picrotoxina/farmacologia , Pregnanolona/farmacologia , Ácido gama-Aminobutírico/farmacologiaRESUMO
BACKGROUND: Status epilepticus (SE) is a type of epileptic activity characterized by a failure of the inhibitory mechanisms that limit seizures, which are mainly regulated by the GABAergic system. This imbalance increases glutamatergic neurotransmission and consequently produces epileptic activity. It is also associated with oxidative stress due to an imbalance between reactive oxygen species (ROS) and antioxidant defences. Unfortunately, long-term treatment with anti-epileptic drugs (AEDs) may produce hepatotoxicity, nephrotoxicity, and haematological alterations. In this way, some secondary metabolites of plants have been used to ameliorate the deterioration of nervous system disorders through their antioxidant properties, in addition to their anticonvulsant effects. An example is Centella asiatica, a plant noted to have a reputed neuroprotective effect related to its antioxidant activity. However, similar to conventional drugs, natural molecules may produce side effects when consumed in high doses, which could occur with Centella asiatica. Therefore, we aimed to evaluate the effect of a standardized extract of Centella asiatica L. Urb with tested anticonvulsant activity on biochemical and haematological parameters in rats subjected to lithium/pilocarpine-induced seizures. METHODS: Twenty-eight adult male Wistar rats were randomly divided into four groups (n = 7 each): vehicle (purified water), Centella asiatica (200 and 400 mg/kg), and carbamazepine (CBZ) (300 mg/kg) as a pharmacological control of anticonvulsant activity. Treatments were administered orally every 24 h for 35 consecutive days. On Day 36, SE was induced using the lithium/pilocarpine model (3 mEq/kg, i.p. and 30 mg/kg s.c., respectively), and the behavioural and biochemical effects were evaluated. RESULTS: Centella asiatica 400 mg/kg increased the latency to the first generalized seizure and SE onset and significantly reduced the time to the first generalized seizure compared to values in the vehicle group. Biochemical parameters, i.e., haematic cytometry, blood chemistry, and liver function tests, showed no significant differences among the different treatments. CONCLUSION: The dose of Centella asiatica that produces anticonvulsant activity in the lithium/pilocarpine model devoid of hepatotoxicity, nephrotoxicity, and alterations in haematological parameters suggests that the standardized extract of this plant could be of utility in the development of new safe therapies for the treatment of convulsions associated with epilepsy.
Assuntos
Centella , Doença Hepática Induzida por Substâncias e Drogas , Ratos , Animais , Ratos Wistar , Anticonvulsivantes/farmacologia , Anticonvulsivantes/uso terapêutico , Antioxidantes/uso terapêutico , Lítio/uso terapêutico , Pilocarpina/uso terapêutico , Convulsivantes/uso terapêutico , Centella/química , Convulsões/induzido quimicamente , Convulsões/tratamento farmacológico , Doença Hepática Induzida por Substâncias e Drogas/tratamento farmacológicoRESUMO
A common way to investigate epilepsy and the effect of antiepileptic pharmaceuticals is to analyze the movement patterns of zebrafish larvae treated with different convulsants like pentylenetetrazol (PTZ), pilocarpine, etc. Many articles have been written on this topic, but the research methods and exact settings are not sufficiently defined in most. Here we designed and executed a series of experiments to optimize and standardize the zebrafish epilepsy model. We found that during the light and the dark trials, the zebrafish larvae moved significantly more in the light, independent of the treatment, both in PTZ and pilocarpine-treated and the control groups. As expected, zebrafish larvae treated with convulsants moved significantly more than the ones in the control group, although this difference was higher between the individuals treated with PTZ than pilocarpine. When examining the optimal observation time, we divided the half-hour period into 5-minute time intervals, and between these, the first 5 minutes were found to be the most different from the others. There were fewer significant differences in the total movement of larvae between the other time intervals. We also performed a linear regression analysis with the cumulative values of the distance moved during the time intervals that fit the straight line. In conclusion, we recommend 30 minutes of drug pretreatment followed by a 10-minute test in light conditions with a 5-minute accommodation time. Our result paves the way toward improved experimental designs using zebrafish to develop novel pharmaceutical approaches to treat epilepsy.
Assuntos
Epilepsia , Pentilenotetrazol , Animais , Pentilenotetrazol/toxicidade , Peixe-Zebra , Convulsivantes/toxicidade , Pilocarpina/farmacologia , Larva , Epilepsia/induzido quimicamente , Epilepsia/tratamento farmacológico , Anticonvulsivantes/farmacologia , Anticonvulsivantes/uso terapêutico , Modelos Animais de DoençasRESUMO
Nitric oxide (NO) participates in processes such as endothelium-dependent vasodilation and neurotransmission/neuromodulation. The role of NO in epilepsy is controversial, attributing it to anticonvulsant but also proconvulsant properties. Clarification of this dual effect of NO might lead to the development of new antiepileptic drugs. Previous results in our laboratory indicated that this contradictory role of NO in seizures could depend on the nitric oxide synthase (NOS) isoform involved, which could play opposite roles in epileptogenesis, one of them being proconvulsant but the other anticonvulsant. The effect of convulsant drugs on neuronal NO (nNO) and endothelial NO (eNO) levels was investigated. Considering the distribution of neuronal and endothelial NOS in neurons and astrocytes, resp., primary cultures of neurons and astrocytes were used as a study model. The effects of convulsant drugs pentylenetetrazole, thiosemicarbazide, 4-aminopyridine and bicuculline on NO levels were studied, using a spectrophotometric method. Their effects on NO levels in neurons and astrocytes depend on the concentration and time of treatment. These convulsant drugs caused an increase in nNO, but a decrease in eNO was proportional to the duration of treatment in both cases. Apparently, nNO possesses convulsant properties mediated by its effect on the glutamatergic and GABAergic systems, probably through GABAA receptors. Anticonvulsant properties of eNO may be the consequence of its effect on endothelial vasodilation and its capability to induce angiogenesis. Described effects last as seizures do. Considering the limitations of these kinds of studies and the unexplored influence of inducible NO, further investigations are required.
Assuntos
Convulsivantes , Óxido Nítrico , Humanos , Convulsivantes/efeitos adversos , Anticonvulsivantes/farmacologia , Anticonvulsivantes/uso terapêutico , Óxido Nítrico Sintase Tipo III , Inibidores Enzimáticos/farmacologia , Convulsões/induzido quimicamente , Convulsões/tratamento farmacológico , Pentilenotetrazol/farmacologia , NeurôniosRESUMO
Status epilepticus (SE) is a life-threatening medical emergency with significant morbidity and mortality. SE is associated with a robust and sustained increase in serum glucocorticoids, reaching concentrations sufficient to activate the dense population of glucocorticoid receptors (GRs) expressed among hippocampal excitatory neurons. Glucocorticoid exposure can increase hippocampal neuron excitability; however, whether activation of hippocampal GRs during SE exacerbates seizure severity remains unknown. To test this, a viral strategy was used to delete GRs from a subset of hippocampal excitatory neurons in adult male and female mice, producing hippocampal GR knockdown mice. Two weeks after GR knockdown, mice were challenged with the convulsant drug pilocarpine to induce SE. GR knockdown had opposing effects on early vs late seizure behaviors, with sex influencing responses. For both male and female mice, the onset of mild behavioral seizures was accelerated by GR knockdown. In contrast, GR knockdown delayed the onset of more severe convulsive seizures and death in male mice. Concordantly, GR knockdown also blunted the SE-induced rise in serum corticosterone in male mice. GR knockdown did not alter survival times or serum corticosterone in females. To assess whether loss of GR affected susceptibility to SE-induced cell death, within-animal analyses were conducted comparing local GR knockdown rates to local cell loss. GR knockdown did not affect the degree of localized neuronal loss, suggesting cell-intrinsic GR signaling neither protects nor sensitizes neurons to acute SE-induced death. Overall, the findings reveal that hippocampal GRs exert an anti-convulsant role in both males and females in the early stages of SE, followed by a switch to a pro-convulsive role for males only. Findings reveal an unexpected complexity in the interaction between hippocampal GR activation and the progression of SE.
Assuntos
Receptores de Glucocorticoides , Estado Epiléptico , Camundongos , Masculino , Feminino , Animais , Receptores de Glucocorticoides/metabolismo , Corticosterona , Estado Epiléptico/induzido quimicamente , Estado Epiléptico/metabolismo , Hipocampo/metabolismo , Convulsões/induzido quimicamente , Convulsões/metabolismo , Glucocorticoides/metabolismo , Pilocarpina/toxicidade , ConvulsivantesRESUMO
Electrocorticography signals, the intracranial recording of electrical signatures of the brain, are recorded by non-penetrating planar electrode arrays placed on the cortical surface. Flexible electrode arrays minimize the tissue damage upon implantation. This work shows the design and development of a 32-channel flexible microelectrode array to record electrocorticography signals from the rat's brain. The array was fabricated on a biocompatible flexible polyimide substrate. A titanium/gold layer was patterned as electrodes, and a thin polyimide layer was used for insulation. The fabricated microelectrode array was mounted on the exposed somatosensory cortex of the right hemisphere of a rat after craniotomy and incision of the dura. The signals were recorded using OpenBCI Cyton Daisy Biosensing Boards. The array faithfully recorded the baseline electrocorticography signals, the induced epileptic activities after applying a convulsant, and the recovered baseline signals after applying an antiepileptic drug. The signals recorded by such fabricated microelectrode array from anesthetized rats demonstrate its potential to monitor electrical signatures corresponding to epilepsy. Finally, the time-frequency analyses highlight the difference in spatiotemporal features of baseline and evoked epileptic discharges.
Assuntos
Eletrocorticografia , Titânio , Animais , Anticonvulsivantes , Convulsivantes , Eletrodos Implantados , Ouro , Microeletrodos , Ratos , RoedoresRESUMO
RATIONALE: Synthetic cannabinoid receptor agonists (SCRAs) are found in illicit smoking products, such as "K2" or "Spice." Convulsions are commonly reported adverse effects of SCRAs but are poorly understood. OBJECTIVES: We determined convulsant effects of SCRAs AB-PINACA, and 5F-ADB-PINACA in adult male NIH Swiss mice, and then determined if convulsant effects of AB-PINACA, 5F-AB-PINACA, 5F-ADB-PINACA, and JWH-018 elicited seizure-like effects using EEG. METHODS: Mice were administered SCRAs or pentylenetetrazole (PTZ) and placed in observation chambers where convulsant effects were scored. The capacity of the CB1R antagonist rimonabant, the benzodiazepine diazepam, or the non-specific CYP450 inhibitor 1-aminobenzotriazole (1-ABT) to attenuate convulsant effects was determined. Other mice were prepared with EEG headmounts to ascertain whether observed convulsions occurred concurrently with seizure-like effects by assessing root-mean-square (RMS) power, high amplitude EEG spike analysis, and videography. RESULTS: Mice receiving AB-PINACA or 5F-ADB-PINACA exhibited dose-dependent convulsant effects that were blocked by 10 mg/kg rimonabant pretreatment but not by pretreatment with 10 mg/kg diazepam; these convulsant effects were not altered in the presence of 100 mg/kg 1-ABT. Repeated administration of 10 mg/kg AB-PINACA and 3 mg/kg 5F-ADB-PINACA produced partial tolerance to convulsant effects but did not lead to cross-tolerance to PTZ-induced convulsions. In EEG studies, convulsant doses of AB-PINACA, 5F-AB-PINACA, 5F-ADB-PINACA, and JWH-018 did not produce seizures concomitantly with convulsions. CONCLUSIONS: These data extend previous findings of convulsant effects of SCRAs and suggest that convulsant effects of AB-PINACA, 5F-AB-PINACA, 5F-ADB-PINACA, and JWH-018 are CB1R-mediated but are not associated with electroencephalographic seizures. These results further suggest that benzodiazepines may not effectively treat convulsions elicited by SCRA use in humans.
Assuntos
Canabinoides , Transtornos Relacionados ao Uso de Substâncias , Animais , Benzodiazepinas , Agonistas de Receptores de Canabinoides/farmacologia , Canabinoides/farmacologia , Convulsivantes , Diazepam , Eletroencefalografia , Humanos , Indazóis , Indóis , Masculino , Camundongos , Naftalenos , Pentilenotetrazol/toxicidade , Receptor CB1 de Canabinoide , Rimonabanto , Convulsões/induzido quimicamente , Valina/análogos & derivadosRESUMO
BACKGROUND: Essential oils (EOs) with pro-convulsant properties are known to cause seizures and may worsen migraine. Here we report five cases of cluster headache (CH) secondary to the usage of toothpastes containing pro-convulsant EOs. METHODS: Patients were identified from the headache clinics of three tertiary care hospitals in south India. Detailed history, examination, and brain magnetic resonance imaging were done in all patients. CH was diagnosed according to the International Classification of Headache Disorders, 3rd edition. Descriptive statistics were used to analyze data. RESULTS: We had five cases of EO-related CH (EORCH), from February 2020 to August 2021; three females and two males, with age ranging from 19 to 54 years. Three had new onset CH, while two had previous cluster attacks which had become refractory to medications for the past 1 year. The toothpastes contained EOs of camphor, eucalyptus, sage, thujone, clove, and fennel in various combinations. These toothpastes were used for a period of at least 3 months in those with new onset CH and for 12 months or more by those with chronic CH. After stopping the usage of these toothpastes, the CH attacks resolved completely within 5-10 days in all patients. In one patient we re-challenged with the same toothpaste and got the CH attack after a period of 2 months. None of the patients had recurrence of CH attacks at follow-up, ranging from 1 to 2 years. CONCLUSION: EOs with pro-convulsive properties may trigger and sustain CH. Physicians may consider inquiring about the exposure to these pro-convulsant EOs in patients with CH and may consider advising the discontinuation of products like toothpastes containing them as a possible means of CH remission.