Transient anticonvulsant effects of time-restricted feeding in the 6-Hz mouse model.

INTRODUCTION: Intermittent fasting enhances neural bioenergetics, is neuroprotective, and elicits antioxidant effects in various animal models. There are conflicting findings on seizure protection, where intermittent fasting regimens often cause severe weight loss resembling starvation which is unsustainable long-term. Therefore, we tested whether a less intensive intermittent fasting regimen such as time-restricted feeding (TRF) may confer seizure protection. METHODS: Male CD1 mice were assigned to either ad libitum-fed control, continuous 8 h TRF, or 8 h TRF with weekend ad libitum food access (2:5 TRF) for one month. Body weight, food intake, and blood glucose levels were measured. Seizure thresholds were determined at various time points using 6-Hz and maximal electroshock seizure threshold (MEST) tests. Protein levels and mRNA expression of genes, enzyme activity related to glucose metabolism, as well as mitochondrial dynamics were assessed in the cortex and hippocampus. Markers of antioxidant defence were evaluated in the plasma, cortex, and liver. RESULTS: Body weight gain was similar in the ad libitum-fed and TRF mouse groups. In both TRF regimens, blood glucose levels did not change between the fed and fasted state and were higher during fasting than in the ad libitum-fed groups. Mice in the TRF group had increased seizure thresholds in the 6-Hz test on day 15 and on day 19 in a second cohort of 2:5 TRF mice, but similar seizure thresholds at other time points compared to ad libitum-fed mice. Continuous TRF did not alter MEST seizure thresholds on day 28. Mice in the TRF group showed increased maximal activity of pyruvate dehydrogenase in the cortex, which was accompanied by increased protein levels of mitochondrial pyruvate carrier 1 in the cortex and hippocampus. There were no other major changes in protein or mRNA levels associated with energy metabolism and mitochondrial dynamics in the brain, nor markers of antioxidant defence in the brain, liver, or plasma. CONCLUSIONS: Both continuous and 2:5 TRF regimens transiently increased seizure thresholds in the 6-Hz model at around 2 weeks, which coincided with stability of blood glucose levels during the fed and fasted periods. Our findings suggest that the lack of prolonged anticonvulsant effects in the acute electrical seizure models employed may be attributed to only modest metabolic and antioxidant adaptations found in the brain and liver. Our findings underscore the potential therapeutic value of TRF in managing seizure-related conditions.

Alterations in Rat Hippocampal Glutamatergic System Properties after Prolonged Febrile Seizures.

Febrile seizures during early childhood may result in central nervous system developmental disorders. However, the specific mechanisms behind the impact of febrile seizures on the developing brain are not well understood. To address this gap in knowledge, we employed a hyperthermic model of febrile seizures in 10-day-old rats and tracked their development over two months. Our objective was to determine the degree to which the properties of the hippocampal glutamatergic system are modified. We analyzed whether pyramidal glutamatergic neurons in the hippocampus die after febrile seizures. Our findings indicate that there is a reduction in the number of neurons in various regions of the hippocampus in the first two days after seizures. The CA1 field showed the greatest susceptibility, and the reduction in the number of neurons in post-FS rats in this area appeared to be long-lasting. Electrophysiological studies indicate that febrile seizures cause a reduction in glutamatergic transmission, leading to decreased local field potential amplitude. This impairment could be attributable to diminished glutamate release probability as evidenced by decreases in the frequency of miniature excitatory postsynaptic currents and increases in the paired-pulse ratio of synaptic responses. We also found higher threshold current causing hind limb extension in the maximal electroshock seizure threshold test of rats 2 months after febrile seizures compared to the control animals. Our research suggests that febrile seizures can impair glutamatergic transmission, which may protect against future seizures.

Additive Anticonvulsant Profile and Molecular Docking Analysis of 5,5'-Diphenylhydantoin Schiff Bases and Phenytoin.

Four 5,5'-diphenylhydantoin Schiff bases possessing different aromatic species (SB1-SB4) were recently synthesized and characterized using spectroscopic and electrochemical tools. The present study aimed to ascertain the anticonvulsant activity of the novel phenytoin derivatives SB1-Ph, SB2-Ph, SB3-Ph, and SB4-Ph, containing different electron-donor and electron-acceptor groups, and their possible mechanism of action. The SB2-Ph exhibited the highest potency to suppress the seizure spread with ED50 = 8.29 mg/kg, comparable to phenytoin (ED50 = 5.96 mg/kg). While SB2-Ph did not produce neurotoxicity and sedation, it decreased locomotion and stereotypy compared to control. When administered in combination, the four Schiff bases decreased the phenytoin ED50 by more than 2× and raised the protective index by more than 7× (phenytoin+SB2-Ph). The strongest correlation between in-vivo and docking study results was found for ligands' interaction energies with kappa and delta receptors. These data, combined with the worst interaction energies of our ligands with the mu receptor, suggest that the primary mechanism of their action involves the kappa and delta receptors, where the selectivity to the kappa receptor leads to higher biological effects. Our findings suggest that the four Schiff bases might be promising candidates with potential applications as a safe and effective adjuvant in epilepsy.

Identification of New Antiseizure Medication Candidates in Preclinical Animal Studies.

Epilepsy is a multifactorial neurologic disease that often leads to many devastating disabilities and an enormous burden on the healthcare system. Until now, drug-resistant epilepsy has presented a major challenge for approximately 30% of the epileptic population. The present article summarizes the validated rodent models of seizures employed in pharmacological researches and comprehensively reviews updated advances of novel antiseizure candidates in the preclinical phase. Newly discovered compounds that demonstrate antiseizure efficacy in preclinical trials will be discussed in the review. It is inspiring that several candidates exert promising antiseizure activities in drug-resistant seizure models. The representative compounds consist of derivatives of hybrid compounds that integrate multiple approved antiseizure medications, novel positive allosteric modulators targeting subtype-selective γ-Aminobutyric acid type A receptors, and a derivative of cinnamamide. Although the precise molecular mechanism, pharmacokinetic properties, and safety are not yet fully clear in every novel antiseizure candidate, the adapted approaches to design novel antiseizure medications provide new insights to overcome drug-resistant epilepsy.

Alterations in the Properties of the Rat Hippocampus Glutamatergic System in the Lithium-Pilocarpine Model of Temporal Lobe Epilepsy.

Status epilepticus (SE) triggers many not yet fully understood pathological changes in the nervous system that can lead to the development of epilepsy. In this work, we studied the effects of SE on the properties of excitatory glutamatergic transmission in the hippocampus in the lithium-pilocarpine model of temporal lobe epilepsy in rats. The studies were performed 1 day (acute phase), 3 and 7 days (latent phase), and 30 to 80 days (chronic phase) after SE. According to RT-qPCR data, expression of the genes coding for the AMPA receptor subunits GluA1 and GluA2 was downregulated in the latent phase, which may lead to the increased proportion of calcium-permeable AMPA receptors that play an essential role in the pathogenesis of many CNS diseases. The efficiency of excitatory synaptic neurotransmission in acute brain slices was decreased in all phases of the model, as determined by recording field responses in the CA1 region of the hippocampus in response to the stimulation of Schaffer collaterals by electric current of different strengths. However, the frequency of spontaneous excitatory postsynaptic potentials increased in the chronic phase, indicating an increased background activity of the glutamatergic system in epilepsy. This was also evidenced by a decrease in the threshold current causing hindlimb extension in the maximal electroshock seizure threshold test in rats with temporal lobe epilepsy compared to the control animals. The results suggest a series of functional changes in the properties of glutamatergic system associated with the epilepsy development and can be used to develop the antiepileptogenic therapy.

Design, Synthesis, and Pharmacology of New Triazole-Containing Quinolinones as CNS Active Agents.

Epilepsy and major depressive disorder are the two of the most common central nervous system (CNS) diseases. Clinicians and patients call for new antidepressants, antiseizure medicines, and in particular drugs for depression and epilepsy comorbidities. In this work, a dozen new triazole-quinolinones were designed, synthesized, and investigated as CNS active agents. All compounds reduced the immobility time significantly during the forced swim test (FST) in mice at the dosage of 50 mg/kg. Compounds 3f-3j gave superior performance over fluoxetine in the FST with more reductions of the immobility time. Compound 3g also reduced immobility time significantly in a tail suspension test (TST) at the dosage of 50 mg/kg, though its anti-immobility activity was inferior to that of fluoxetine. An open field test was carried out and it eliminated the false-positive possibility of 3g in the FST and TST, which complementarily supported the antidepressant activity of 3g. We also found that almost all compounds except 3k exhibited antiseizure activity in the maximal electroshock seizure (MES) model at 100 or 300 mg/kg. Compounds 3c, 3f, and 3g displayed the ED50 of 63.4, 78.9, and 84.9 mg/kg, and TD50 of 264.1, 253.5, and 439.9 mg/kg, respectively. ELISA assays proved that the mechanism for the antiseizure and antidepressant activities of compound 3g was via affecting the concentration of GABA in mice brain. The molecular docking study showed a good interaction between 3g and the amino acid residue of the GABAA receptor. Excellent drug-like properties and pharmacokinetic properties of compound 3a-l were also predicted by Discovery Studio. These findings provided a new skeleton to develop agents for the treatment of epilepsy and depression comorbidities.

Importance of Pharmacophore in Designing Anticonvulsant Agents.

Drug design is one of the critical aspects of the drug development process. The present review focused on different heterocyclic molecules having anticonvulsant activity with structural diversity and common pharmacophoric features. For the first time (1995), Dimmock and his team introduced specific arrangements of three important pharmacophores for anticonvulsant activity. These pharmacophores include two hydrophobic binding sites and one hydrogen binding site. After a few years (2012), Pandeya modified Dimmock's concept by adding one more pharmacophoric feature as an electron donor in the previously suggested pharmacophoric arrangement of the anticonvulsant. As a result, numerous scientists designed anticonvulsant drugs based on Dimmock's and Pandeya's concept. In addition, marketed anticonvulsant preparation containing Riluzole, Phenobarbital, Progabide, Ralitoline, etc., also holds the suggested pharmacophores by Dimmock and Pandeya's pharmacophoric concept. This review mainly focuses on the compilation of reported scientific literature in the last decade on the pharmacophoric features of different heterocyclic anticonvulsants, which will help develop new anticonvulsants.

In vitro and in vivo anti-seizure activity of hydromethanolic extract and fractions of Pterolobium stellatum.

ETHNOPHARMACOLOGICAL RELEVANCE: In Ethiopia, the whole plant juice of Pterolobium stellatum is used to treat seizures and epilepsy. AIM OF THE STUDY: To investigate the antiseizure activity of hydromethanolic crude extract and fractions collected from leaves of P. stellatum using both in vitro, and in vivo seizure models in mice. MATERIALS AND METHODS: Fresh leaves of P. stellatum were collected from Awash Melka, Addis Ababa, Ethiopia. An 80% crude methanol extract was further fractionated to produce petroleum ether, chloroform, butanol, and aqueous fractions. Anti-seizure activity of the crude extract and fractions (petroleum ether, chloroform, butanol, and water) were assessed at a concentration of 0.7 mg/ml using the in vitro 0 Mg2+ model of seizures in mouse brain slices prepared from 14- to 21-day-old C57BL/6 mice. The maximal electroshock seizure (MES) model and the pentylenetetrazol (PTZ) seizure model for seizures were performed on male BALB/c mice using 400 mg/kg and 800 mg/kg of crude 80% methanol extract, as well as the four fractions described above. Diazepam and phenytoin were used as positive controls for PTZ and MES test respectively. RESULTS: Addition of 0.7 mg/ml of crude 80% methanol extract of P. stellatum prevented the onset of SLEs in most brain slices in the 0 Mg2+in vitro model of seizures, with similar efficacy to diazepam (3 µM). The same extract at 400 and 800 mg/kg was efficacious in reducing the hindlimb extension time in the MES model and delaying the onset of myoclonic convulsions in the PTZ model, although not to the same extent as phenytoin (10 mg/kg) or diazepam (5 mg/kg). The chloroform and water fractions of the crude extract also showed significant anti-seizure activity across all three models whilst the non-polar petroleum ether and butanol fractions did not. The UPLC-MS analysis indicated the presence of gallic acid, ellagic acid, kaempferol, myricitrin, isoquercitrin and quercitirin in the crude extract. Gallic acid and ellagic acid were observed in chloroform fraction and in the water fraction ellagic acid, kaempferol, myricitrin and isoquercitrin were detected. CONCLUSION: The crude hydromethanolic extract of P. stellatum has significant anti-seizure activity. The chloroform and aqueous fractions have antiseizure activity. The extracts have previously identified compounds with anticonvulsant activity which indicates the antiseizure potential of the plant.

Glyceryl triacetate feeding in mice increases plasma acetate levels but has no anticonvulsant effects in acute electrical seizure models.

INTRODUCTION: Acetate has been shown to have neuroprotective and anti-inflammatory effects. It is oxidized by astrocytes and can thus provide auxiliary energy to the brain in addition to glucose. Therefore, we hypothesized that it may protect against seizures, which is investigated here by feeding glyceryl triacetate (GTA), to provide high amounts of acetate without raising sodium or acid levels. METHOD: CD1 male mice were fed controlled diets with or without GTA for up to three weeks. Body weights, blood glucose levels, plasma short-chain fatty acid levels, and other hematological parameters were monitored. Seizure thresholds were determined in 6 Hz and maximal electroshock seizure threshold (MEST) tests. Antioxidant capacities were evaluated in the cerebral cortex and plasma using a ferric reducing antioxidant power (FRAP) assay and Trolox equivalent antioxidant capacity assay. RESULTS: Body weight gain was similar with both diets with and without GTA in two experiments. Glyceryl triacetate-fed groups showed 2-3- and 1.6-fold increased acetate and propionate levels in plasma, respectively. Glucose levels were unaltered in blood collected from the tail tip but increased in trunk blood. No differences were found in the activity of cerebral cortex acetyl-CoA synthetase. In the 6 Hz threshold test, seizure thresholds were lower by 3 mA and 2.4 mA after 8 and 14 days, respectively, in the GTA compared to the control diet-fed group, but showed no difference on day 16, showing that GTA has small, but inconsistent proconvulsant effects in this model. In MEST tests, a slightly increased seizure threshold (1 mA) was found on day 19 in the GTA-fed group, but not in another experiment on day 21. There were no differences in antioxidant capacity in plasma or cortex between the two groups. CONCLUSION: Glyceryl triacetate feeding showed no antioxidant effects nor beneficial changes in acute electrical seizure threshold mouse models, despite its ability to increase plasma acetate levels.

Anticonvulsant activity of methanolic extract of Withania cogulans in mice.

Mental and neurological diseases including depression, Parkinson's disease, dementia, epilepsy, anxiety disorders and bipolar disorders account for a considerable amount of the world's disease burden. Unfortunately, drugs used in the treatment of neurological diseases are expensive, symptomatic and they produce undesirable side effects. People from different cultures prefer to use medicinal plants for the treatment of various ailments ranging from plain to perplex disorders because they are most affordable, cost effective and easily accessible source of treatment in the primary healthcare system throughout the world. Withania coagulans, an erect grayish under-shrub belongs to family Solanaceae. It is common in Pakistan, East India, Iran and Afghanistan. The objective of this study was to analyze the anti-seizure activity of crude methanolic extract of Withania coagulans fruits (MeWc). For screening of this activity, maximal electroshock seizures model (MES) and chemically-induced seizures models were used. In maximal electroshock seizures test MeWc showed significant dose dependent percent protection against hind-limb tonic extension; significant and dose-dependent increase in latency to myoclonic jerks and tonic clonic convulsions and decrease in seizures duration were observed in PTZ-induced seizures. In strychnine-induced convulsions MeWc significantly increased latency to hind-limb tonic extension and percent protection from death in a dose-dependent manner. Thus, it was inferred from the experiments that extract of Withania coagulans showed anticonvulsant activity.

Synthesis of ring-opened derivatives of triazole-containing quinolinones and their antidepressant and anticonvulsant activities.

Based on the potent antidepressant and anticonvulsant activities of the triazole-containing quinolinones reported in our previous work, a series of ring-opened derivatives of them were designed, synthesized in this work. Their antidepressant and anticonvulsant activities were screened using the forced swimming test (FST) and the maximal electroshock seizure test (MES), respectively. The results showed that compounds 4a, 5a, 6c-6e, 6g-6i, and 7 led to significant reductions in the accumulated immobility time in the FST at a dose of 50 mg/kg. Especially compound 7 exhibited higher levels of efficacy than the reference standard fluoxetine in the FST and the tail suspension test. The results of an open field test excluded the possibility of central nervous stimulation of 7, which further confirmed its antidepressant effect. Meanwhile, compounds 6a-6i and 7 showed different degrees of anticonvulsant activity in mice at the doses range from 300 to 30 mg/kg in the MES. Among them, compounds 6e and 7 displayed the ED50 of 38.5 and 32.7 mg/kg in the MES, and TD50 of 254.6 and 245.5 mg/kg, respectively. No one showed neurotoxicity at the dose of 100 mg/kg. The preliminary investigation forward to their mechanism indicated that regulation of GABAergic system might contribute to their anticonvulsive and anti-depressive action.

Adjuvant role of Ocimum sanctum hydroalcoholic extract with carbamazepine and phenytoin in experimental model of acute seizures.

PURPOSE: This study assessed adjuvant potential of Ocimum sanctum hydroalcoholic extract (OSHE) with antiepileptic drugs (AEDs) carbamazepine (CBZ) and phenytoin (PHT) in maximal electroshock seizure (MES) model in male Wistar rats. MATERIAL AND METHODS: Pharmacodynamic effect of OSHE (1000 mg/kg) was assessed through seizure protection potential, neurobehavioral tests and oxidative stress estimation in MES model after 14 days administration of OSHE alone or combination with maximal (M) and sub-maximal (SM) dose of CBZ or PHT. Pharmacokinetic interaction of OSHE with AEDs was also assessed after 14 days of drug treatment. RESULTS: OSHE per se showed 50% protection against MES-induced seizures. Combination of OSHE with AEDs' SM dose enhanced its seizure protection potential. Significant reduction in duration of tonic hind limb extension was observed in CBZ-SM + OSHE as compared to control group (p = 0.006). Among neurobehavioral tests in Morris water maze test rats of CBZ-M + OSHE took significantly less time to reach the platform (p = 0.022) and spent more time in target quadrant (p = 0.016) as compared to other groups. Similarly, rats of PHT-SM + OSHE group spent significantly more time in the target quadrant (p = 0.013). In elevated plus maze test, CBZ-M + OSHE had significantly decreased transfer latency compared to other groups (p = 0.013). OSHE alone treated group had significantly lower oxidative stress as compared to other groups. No significant pharmacokinetic interaction was observed between OSHE and AEDs (CBZ, PHT). CONCLUSION: Ocimum's potential of enhanced seizure protection and neuroprotection along with minimal drug interaction with AEDs substantiate its adjuvant role in the management of epilepsy.

Anticonvulsant Effect of Alcea aucheri on Pentylenetetrazole and Maximal Electroshock Seizures in Mice.

INTRODUCTION: This study was designed to investigate the possible anticonvulsant effect of acute administration of an aqueous extract of flowers of Alcea aucheri (EFA) in two in vivo seizure models. METHODS: Seizures were induced in male adult Swiss mice by administration of Pentylenetetrazol (PTZ) or Maximal Electroshock (MES). Mice were randomly subjected to receive saline, EFA (8.75-175 mg.kg-1), or diazepam intraperitoneally (i.p.) 15 or 30 min before PTZ injection. In another experiment, mice were treated (i.p.) with saline, EFA (8.75-350 mg.kg-1), or phenytoin 15 or 30 min before the MES test. Diazepam and phenytoin were used as reference drugs. RESULTS: EFA (175 mg.kg-1) significantly increased the PTZ-induced seizure threshold compared with the saline control group 15 min after its administration. In the MES test, the extract (35 mg.kg-1) increased the latency to onset of tonic Hind Limb Extension (HLE) (seizure activity) compared with the saline group 15 min after treatment. Also, 30 min after treatment, EFA (35, 70, and 175 mg.kg-1) increased the latency to onset of the seizure, decreased the duration of the seizure (70 mg.kg-1), and decreased seizure occurrence (350 mg.kg-1) compared with those of the saline group. At both time points, the extract at all doses significantly reduced the mortality rate compared with the saline group. CONCLUSION: These findings provide evidence of a possible anticonvulsant effect of A. aucheri in PTZ and MES seizure models in mice.

Pharmacokinetic and pharmacodynamic analysis of (2S,3S)-sec-butylpropylacetamide (SPD) in rats and pigs-A CNS-active stereoisomer of SPD.

OBJECTIVES: To advance the development of (2S,3S)-sec-butylpropylacetamide (SPD) as a new treatment for acute repetitive seizures (ARS), by studying its pharmacokinetics (PK) in pigs and its PK-pharmacodynamic (PK-PD) correlation in rats. METHODS: Two (2S,3S)-SPD intramuscular formulations (FA and FB ) were administered to pigs and rats and blood samples were withdrawn at different times after dosing. Major PK parameters were estimated in both species. PD analysis was conducted in rats utilizing the maximal-electroshock seizure threshold (MEST) test. Because ARS treatment requires a rapid action, the MEST test allows comparative evaluation of (2S,3S)-SPD intramuscular injection on rat susceptibility to electroconvulsive shock at various times after dosing. RESULTS: In rats, (2S,3S)-SPD plasma exposure increased proportionally following intramuscular dosing (20, 25 and 40 mg/kg) of FA and FB . Peak plasma concentration (Cmax ) was obtained at 1-2 hours after dosing and ranged between 6.8 and 9.4 mg/L. (2S,3S)-SPD plasma concentration at 10 minutes after dosing (C10 ) ranged between 2.1 and 3.5 mg/mL, and its half-life ranged between 0.9 and 2.3 hours. The highest C10 value, which may indicate rapid activity onset, and the highest Cmax were observed following administration of FA (40 mg/kg): C10  = 3.5 mg/L and Cmax  = 9.5 mg/L. In the MEST test, (2S,3S)-SPD (20 and 60 mg/kg) significantly raised the tonic seizure threshold compared to vehicle at 4, 7, 10, and 20 minutes after dosing, with a 1.6-fold increase at 20 minutes, which coincided with (2S,3S)-SPD brain Cmax . Following intramuscular dosing of (2S,3S)-SPD (12 mg/kg) to pigs of FA and FB , a Cmax value of 0.9 mg/L was obtained 0.42 and 0.75 hours after dosing, respectively. (2S,3S)-SPD C10 was 0.27 mg/L (FA ) and 0.49 mg/L (FB ). (2S,3S)-SPD clearance, volume of distribution, and half-life were 2 L/h/kg, 18-28 L/kg, and 6.1-9.7 hours, respectively. SIGNIFICANCE: (2S,3S)-SPD demonstrated a good PK-PD correlation in the rat MEST test, with a rapid onset. (2S,3S)-SPD first PK study in pigs showed that doses >12 mg/kg are required to achieve in pigs the plasma concentrations associated with activity at the rat MEST test.

Equilibrative Nucleoside Transporters-1 Inhibitors Act as Anti-epileptic Agents by Inhibiting Glutamatergic Transmission.

Background and Purpose: Adenosine dysregulation is associated with the occurrence of the epilepsy and equilibrative nucleoside transporters-1 (ENT-1) functions as an important regulator of extracellular adenosine in the brain. This study was aimed to prove the anti-epileptic effect of BBB permeable ENT-1 inhibitors, JMF1907 and J4, on animal models of various epilepsy, and the mechanisms that are involved. Experimental Approach: Maximal electroshock seizure (MES), pentylenetetrazol (PTZ)-induced seizure and kindling models were used as mouse models of generalized tonic-clonic epilepsy, generalized myoclonic epilepsy, and partial epilepsy, respectively. The epilepsy frequency, duration, and Racine score were evaluated. Whole-cell recordings were made from the hippocampal dentate granule cells by using a patch-clamp technique in the brain slice of the mice. Key Results: In MES, JMF1907 at a dose of 5 mg kg-1 was efficacious in decreasing hindlimb extension, while J4 did not decrease hindlimb extension until a higher dose (10 mg kg-1). Both JMF1907 and J4 were more potent in lengthening onset latency than ethosuximide (ETH) in PTZ-induced myoclonic epilepsy model, whereas ETH had better effects on the Racine score. In kindling model, JMF1907 and J4 at a dose of 1 mg kg-1 had effects on seizure frequency and duration, and the effects of JMF1907 were comparable with those of carbamazepine. Both JMF1907 and J4 can reduce the glutamatergic spontaneous excitatory post-synaptic currents (sEPSCs) frequency. The maximal inhibition was about 50% for JMF1907 at a concentration of 1 µg L-1, whereas J4 only inhibited 40% of sEPSCs frequency at a dose of 10 µg L-1. Conclusion and Implications: ENT-1 inhibitors, JMF1907 and J4, showed anti-epileptic effects in different epilepsy models and the effects involved pre-synaptic neuronal modulation.

Design, synthesis, and evaluation of anticonvulsant activities of benzoxazole derivatives containing the 1,2,4-triazolone moiety.

A novel series of benzoxazole derivatives containing 1,2,4-triazolone (5a-m) was designed. These compounds were synthesized in order to screen their anticonvulsant activities by the maximal electroshock seizure (MES) model and the subcutaneous pentylenetetrazole (sc-PTZ) seizure model in mice. The rotarod test was used to evaluate their neurotoxicities. Most of the compounds showed anti-MES activities at 100 and 300 mg/kg. Compound 5f, which showed potential anticonvulsant activity in the MES model with ED50 values of 22.0 mg/kg, was considered as the most promising one in this study. It exhibited greater safety than that of carbamazepine and valproate regarding neurotoxicity. The efficacy of compound 5f in inhibiting the tonic seizures and death induced by the convulsants 3-mercaptopropionic acid and BIC was also verified. In an enzyme-linked immunosorbent assay, compound 5f and the positive drug phenytoin significantly increased the γ-aminobutyric acid (GABA) level in the mouse brain. Further, pretreatment with an inhibitor of the GABA synthesizing enzyme dramatically raised the ED50 value of 5f in the MES model. These results confirmed that the compound 5f plays its anticonvulsive action via regulating the GABA function in the brain. Also, a docking study of the compound 5f in the benzodiazepine (BZD) binding site of the GABAA receptor confirmed possible binding of the compound 5f with BZD receptors.

Threshold for maximal electroshock seizures (MEST) at three developmental stages in young mice.

Early brain development after birth is extremely dynamic, suggesting that potential functional changes occur during this period. In this study, the maximal electroshock seizure threshold (MEST) was used to explore the electrophysiological variation among three developmental stages in young mice (no more than 5 weeks old). The induced electroshock seizure (ES) behavior of early postnatal mice (1-2-weeks old) differed from that during weaning (3 weeks old) and early puberty (4-5-weeks old). Thus, we further explored their respective characteristic responses to the ES parameters. When the stimulation current (SC) was limited to 4.0 mA, only the 1-2-week-old mice were induced to exhibit ES behavior at voltages of 30 V and 40 V, indicating they were more sensitive to maximal electroshock seizure (MES) (response to lower voltage). Surprisingly, however, they showed substantially lower mortality than the older groups under higher voltage conditions (60, 100, 160, and 200 V), suggesting better tolerance to the SC. We also found that when the current limit decreased to 3.5 mA, the 4-5-week-olds mice exhibited stable ES behavior with low mortality, while for 3-week-olds mice, the SC limit required to be reduced to 1.5 mA. In conclusion, our findings showed that neural sensitivity to MES was significantly different in young mice before puberty. Thus, greater attention should be given to distinguishing the developmental period of mice, especially in electrophysiological examination.

Interactions of Mexiletine with Novel Antiepileptic Drugs in the Maximal Electroshock Test in Mice: An Isobolographic Analysis.

The aim of the study was to evaluate precisely the type of interactions between mexiletine (an antiarrhythmic drug) and four new generation antiepileptic drugs: lamotrigine, oxcarbazepine, topiramate and pregabalin in the maximal electroshock test in mice (MES). The isobolographic analysis was used to assess the nature of interactions between the tested drugs. Total brain concentrations of antiepileptics were also measured to detect possible pharmacokinetic interactions. The results obtained indicated that the mixture of mexiletine and pregabalin at the fixed ratios of 1:1 and 3:1 led to supra-additive interaction in terms of seizure suppression, while the proportion of 1:3 occurred additive. Synergism was also demonstrated for the combination of mexiletine and topiramate in all three proportions. Combinations of mexiletine with lamotrigine and mexiletine with oxcarbazepine were found to be additive. Adverse-effect profiles of mexiletine, antiepileptics and drug combinations were evaluated in the chimney test (motor coordination) and step-through passive-avoidance task (long-term memory). Mexiletine and drug combinations did not impair long-term memory. Moreover, all combinations of mexiletine with lamotrigine, oxcarbazepine and topiramate had no significant effect on motor coordination. However, the results from the chimney test indicated that pregabalin, administered alone at its ED50 dose from the MES-test, significantly impaired motor performance. Similar adverse effects were observed when mexiletine was co-administered with pregabalin at the fixed-dose ratio combinations of 1:1 and 1:3. However, reduction of pregabalin dose at the fixed ratio of 3:1 seems to prevent significant motor impairment. The results may indicate that mexiletine can be considered as an adjunctive drug in antiepileptic treatment, particularly in patients with concomitant cardiac arrhythmia.

Beneficial Combination of Lacosamide with Retigabine in Experimental Animals: An Isobolographic Analysis.

BACKGROUND/AIM: To isobolographically determine the types of interactions that occur between retigabine and lacosamide (LCM; two third-generation antiepileptic drugs) with respect to their anticonvulsant activity and acute adverse effects (sedation) in the maximal electroshock-induced seizures (MES) and chimney test (motor performance) in adult male Swiss mice. METHODS: Type I isobolographic analysis for nonparallel dose-response effects for the combination of retigabine with LCM (at the fixed-ratio of 1:1) in both the MES and chimney test in mice was performed. Brain concentrations of retigabine and LCM were measured by high-pressure liquid chromatography (HPLC) to characterize any pharmacokinetic interactions occurring when combining these drugs. RESULTS: Linear regression analysis revealed that retigabine had its dose-response effect line nonparallel to that of LCM in both the MES and chimney tests. The type I isobolographic analysis illustrated that retigabine combined with LCM (fixed-ratio of 1:1) exerted an additive interaction in the mouse MES model and sub-additivity (antagonism) in the chimney test. With HPLC, retigabine and LCM did not mutually change their total brain concentrations, thereby confirming the pharmacodynamic nature of the interaction. CONCLUSION: LCM combined with retigabine possesses a beneficial preclinical profile (benefit index ranged from 2.07 to 2.50) and this 2-drug combination is worth recommending as treatment plan to patients with pharmacoresistant epilepsy.