The role of technical, biological and pharmacological factors in the laboratory evaluation of anticonvulsant drugs. IV. Protective indices

Animal Models of Drug-Resistant Epilepsy as Tools for Deciphering the Cellular and Molecular Mechanisms of Pharmacoresistance and Discovering More Effective Treatments

In the last 30 years, over 20 new anti-seizure medicines (ASMs) have been introduced into the market for the treatment of epilepsy using well-established preclinical seizure and epilepsy models. Despite this success, approximately 20-30% of patients with epilepsy have drug-resistant epilepsy (DRE). The current approach to ASM discovery for DRE relies largely on drug testing in various preclinical model systems that display varying degrees of ASM drug resistance. In recent years, attempts have been made to include more etiologically relevant models in the preclinical evaluation of a new investigational drug. Such models have played an important role in advancing a greater understanding of DRE at a mechanistic level and for hypothesis testing as new experimental evidence becomes available. This review provides a critical discussion of the pharmacology of models of adult focal epilepsy that allow for the selection of ASM responders and nonresponders and those models that display a pharmacoresistance per se to two or more ASMs. In addition, the pharmacology of animal models of major genetic epilepsies is discussed. Importantly, in addition to testing chemical compounds, several of the models discussed here can be used to evaluate other potential therapies for epilepsy such as neurostimulation, dietary treatments, gene therapy, or cell transplantation. This review also discusses the challenges associated with identifying novel therapies in the absence of a greater understanding of the mechanisms that contribute to DRE. Finally, this review discusses the lessons learned from the profile of the recently approved highly efficacious and broad-spectrum ASM cenobamate.

Bumetanide potentiates the anti-seizure and disease-modifying effects of midazolam in a noninvasive rat model of term birth asphyxia

Birth asphyxia and the resulting hypoxic-ischemic encephalopathy (HIE) are highly associated with perinatal and neonatal death, neonatal seizures, and an adverse later-life outcome. Currently used drugs, including phenobarbital and midazolam, have limited efficacy to suppress neonatal seizures. There is a medical need to develop new therapies that not only suppress neonatal seizures but also prevent later-life consequences. We have previously shown that the loop diuretic bumetanide does not potentiate the effects of phenobarbital in a rat model of birth asphyxia. Here we compared the effects of bumetanide (0.3 or 10 mg/kg i.p.), midazolam (1 mg/kg i.p.), and a combination of bumetanide and midazolam on neonatal seizures and later-life outcomes in this model. While bumetanide at either dose was ineffective when administered alone, the higher dose of bumetanide markedly potentiated midazolam's effect on neonatal seizures. Median bumetanide brain levels (0.47-0.53 µM) obtained with the higher dose were in the range known to inhibit the Na-K-Cl-cotransporter NKCC1 but it remains to be determined whether brain NKCC1 inhibition was underlying the potentiation of midazolam. When behavioral and cognitive alterations were examined over three months after asphyxia, treatment with the bumetanide/midazolam combination, but not with bumetanide or midazolam alone, prevented impairment of learning and memory. Furthermore, the combination prevented the loss of neurons in the dentate hilus and aberrant mossy fiber sprouting in the CA3a area of the hippocampus. The molecular mechanisms that explain that bumetanide potentiates midazolam but not phenobarbital in the rat model of birth asphyxia remain to be determined.

Preclinical common data elements for general pharmacological studies (pharmacokinetic sample collection, tolerability, and drug administration). A report of the TASK3-WG1A General Pharmacology Working Group of the ILAE/AES Joint Translational Task Force

Growing concerns over rigor and reproducibility of preclinical studies, including consistency across laboratories and translation to clinical populations, have triggered efforts to harmonize methodologies. This includes the first set of preclinical common data elements (CDEs) for epilepsy research studies, as well as Case Report Forms (CRFs) for widespread use in epilepsy research. The General Pharmacology Working Group of the ILAE/AES Task Force (TASK3-WG1A) has continued in this effort by adapting and refining CDEs/CRFs to address specific study design areas as they relate to preclinical drug screening: general pharmacology, pharmacokinetics (PK) and pharmacodynamics (PD), and tolerability. This work has expanded general pharmacology studies to include dose records, PK/PD, tolerability, and elements of rigor and reproducibility. Tolerability testing CRFs included rotarod and Irwin/Functional Observation Battery (FOB) assays. The material provided in the form of CRFs can be delivered for widespread use within the epilepsy research community.

Klotho ameliorated cognitive deficits in a temporal lobe epilepsy rat model by inhibiting ferroptosis

Cognitive deficits are among the most common comorbidities of temporal lobe epilepsy (TLE). Ferroptosis associated with the accumulation of iron overload-dependent lipid peroxidation produces significant cognitive deficits in TLE. The anti-aging protein, klotho, has been shown to exert neuroprotective effects while enhancing cognition in neurodegenerative disorders. However, the role of klotho in TLE progression has not been established. In this study, we evaluated the effects and underlying mechanisms of klotho in a rat model of TLE induced by lithium-chloride and pilocarpine (LiCl-Pilo). The expression of klotho was found to be inhibited in the hippocampus following LiCl-Pilo induced TLE in rats. An adeno-virus (AAV), which mediated klotho overexpression (AAV-KL) was injected into the bilateral hippocampus of the rat models. After 3 weeks, rats were treated through intraperitoneal injections of LiCl-Pilo. After 9 weeks, AAV-KL was found to have significantly induced klotho overexpression in the hippocampus, effectively ameliorated cognitive deficits and exerted neuroprotective effects in LiCl-Pilo induced TLE rat models. Klotho significantly prevented ferroptosis and iron overload. Meanwhile, klotho regulated the expressions of divalent metal transporter 1 (DMT 1) and ferroportin (FPN) that were associated with iron accumulation in the hippocampus. Furthermore, klotho significantly elevated glutathione peroxidase-4 (GPX-4) and glutathione (GSH) levels while suppressed reactive oxygen species (ROS) levels. In conclusion, klotho ameliorated cognitive deficits and exerted neuroprotective effects by inhibiting ferroptosis in LiCl-Pilo induced TLE rat models.

Single-Target Versus Multi-Target Drugs Versus Combinations of Drugs With Multiple Targets: Preclinical and Clinical Evidence for the Treatment or Prevention of Epilepsy

Rationally designed multi-target drugs (also termed multimodal drugs, network therapeutics, or designed multiple ligands) have emerged as an attractive drug discovery paradigm in the last 10-20 years, as potential therapeutic solutions for diseases of complex etiology and diseases with significant drug-resistance problems. Such agents that modulate multiple targets simultaneously are developed with the aim of enhancing efficacy or improving safety relative to drugs that address only a single target or to combinations of single-target drugs. Although this strategy has been proposed for epilepsy therapy >25 years ago, to my knowledge, only one antiseizure medication (ASM), padsevonil, has been intentionally developed as a single molecular entity that could target two different mechanisms. This novel drug exhibited promising effects in numerous preclinical models of difficult-to-treat seizures. However, in a recent randomized placebo-controlled phase IIb add-on trial in treatment-resistant focal epilepsy patients, padsevonil did not separate from placebo in its primary endpoints. At about the same time, a novel ASM, cenobamate, exhibited efficacy in several randomized controlled trials in such patients that far surpassed the efficacy of any other of the newer ASMs. Yet, cenobamate was discovered purely by phenotype-based screening and its presumed dual mechanism of action was only described recently. In this review, I will survey the efficacy of single-target vs. multi-target drugs vs. combinations of drugs with multiple targets in the treatment and prevention of epilepsy. Most clinically approved ASMs already act at multiple targets, but it will be important to identify and validate new target combinations that are more effective in drug-resistant epilepsy and eventually may prevent the development or progression of epilepsy.

The autophagy-enhancing drug carbamazepine improves neuropathology and motor impairment in mouse models of Machado-Joseph disease

AIMS

Machado-Joseph disease (MJD), or spinocerebellar ataxia type 3 (SCA3), is the most common autosomal dominantly-inherited ataxia worldwide and is characterised by the accumulation of mutant ataxin-3 (mutATXN3) in different brain regions, leading to neurodegeneration. Currently, there are no available treatments able to block disease progression. In this study, we investigated whether carbamazepine (CBZ) would activate autophagy and mitigate MJD pathology.

METHODS

The autophagy-enhancing activity of CBZ and its effects on clearance of mutATXN3 were evaluated using in vitro and in vivo models of MJD. To investigate the optimal treatment regimen, a daily or intermittent CBZ administration was applied to MJD transgenic mice expressing a truncated human ATXN3 with 69 glutamine repeats. Motor behaviour tests and immunohistology was performed to access the alleviation of MJD-associated motor deficits and neuropathology. A retrospective study was conducted to evaluate the CBZ effect in MJD patients.

RESULTS

We found that CBZ promoted the activation of autophagy and the degradation of mutATXN3 in MJD models upon short or intermittent, but not daily prolonged, treatment regimens. CBZ up-regulated autophagy through activation of AMPK, which was dependent on the myo-inositol levels. In addition, intermittent CBZ treatment improved motor performance, as well as prevented neuropathology in MJD transgenic mice. However, in patients, no evident differences in SARA scale were found, which was not unexpected given the small number of patients included in the study.

CONCLUSIONS

Our data support the autophagy-enhancing activity of CBZ in the brain and suggest this pharmacological approach as a promising therapy for MJD and other polyglutamine disorders.

Effect of acute and chronic exposure to lovastatin on the anticonvulsant action of classical antiepileptic drugs in the mouse maximal electroshock-induced seizure model

Numerous studies indicate neuroprotective activity of statins, commonly used cholesterol lowering drugs in epilepsy and several other neurological diseases. Promising anti-convulsant and neuroprotective effects of statins, attributed to their anti-excitotoxic and anti-inflammatory action were reported in several animals' seizure models. To determine the effects of acute (single) and chronic (once daily for 7 consecutive days) administration of lovastatin on the protective activity of four classical antiepileptic drugs such as carbamazepine, phenobarbital, phenytoin and valproate in the mouse maximal electroshock seizure model. Seizure activity (maximal electroconvulsions) in mice were generated by alternating current delivered via ear-clip electrodes. Adverse-effect profile of lovastatin combinations with the tested antiepileptic drugs was assessed in the chimney test (motor performance). Total brain concentrations of antiepileptic drugs were evaluated with the fluorescence polarization immunoassay technique as a measure of the pharmacokinetic interaction between drugs. Lovastatin administered acutely or chronically (5-20 mg/kg) did not significantly affect the threshold for electroconvulsions in mice. Acute lovastatin (10 mg/kg) significantly enhanced the anticonvulsant effect of valproate, which was accompanied with a 34% significant increase in total brain concentration of valproate. Acute lovastatin in combination with phenytoin impaired motor performance by notably decreasing the TD₅₀ value of phenytoin. Chronic lovastatin (10 mg/kg) markedly enhanced the anticonvulsant potential of phenytoin. Acute lovastatin increased anticonvulsant action of valproate but also significantly raised level of valproate in brain after combined administration suggesting pharmacokinetic nature of interaction. The combinations of chronic lovastatin combined with phenytoin can potentially enhance the anticonvulsant potency of phenytoin.

Interactions among Lacosamide and Second-Generation Antiepileptic Drugs in the Tonic-Clonic Seizure Model in Mice

Combination therapy with two or three antiseizure medications (ASMs) is sometimes a preferred method of treatment in epilepsy patients. (1) Background: To detect the most beneficial combination among three ASMs, a screen test evaluating in vivo interactions with respect to their anticonvulsant properties, was conducted on albino Swiss mice; (2) Methods: Classification of interactions among lacosamide (LCM) and selected second-generation ASMs (lamotrigine (LTG), pregabalin (PGB), oxcarbazepine (OXC), and topiramate (TPM)) was based on the isobolographic analysis in the mouse maximal electroshock-induced seizure (MES) model. Interactions among LCM and second-generation ASMs were visualized using a polygonogram; (3) Results: In the mouse MES model, synergy was observed for the combinations of LCM + TPM + PGB and LCM + OXC + PGB. Additivity was reported for the other combinations tested i.e., LCM + LTG + TPM, LCM + LTG + PGB, LCM + LTG + OXC, and LCM + OXC + TPM in this seizure model. No adverse effects associated with triple ASM combinations, containing LCM and second-generation ASMs were observed in mice; (4) Conclusions: The combination of LCM + TPM + PGB was the most beneficial combination among the tested in this study, offering synergistic suppression of tonic-clonic seizures in mice subjected to the MES model. Both the isobolographic analysis and polygonogram method can be recommended for experimental epileptology when classifying interactions among the ASMs.

Synthesis, Anticonvulsant, and Antinociceptive Activity of New 3-(2-Chlorophenyl)- and 3-(3-Chlorophenyl)-2,5-dioxo-pyrrolidin-1-yl-acetamides

The new series of 3-(2-chlorophenyl)- and 3-(3-chlorophenyl)-pyrrolidine-2,5-dione-acetamide derivatives as potential anticonvulsant and analgesic agents was synthesized. The compounds obtained were evaluated in the following acute models of epilepsy: maximal electroshock (MES), psychomotor (6 Hz, 32 mA), and subcutaneous pentylenetetrazole (scPTZ) seizure tests. The most active substance-3-(2-chlorophenyl)-1-{2-[4-(4-fluorophenyl)piperazin-1-yl]-2-oxoethyl}-pyrrolidine-2,5-dione (6) showed more beneficial ED₅₀ and protective index values than the reference drug—valproic acid (68.30 mg/kg vs. 252.74 mg/kg in the MES test and 28.20 mg/kg vs. 130.64 mg/kg in the 6 Hz (32 mA) test, respectively). Since anticonvulsant drugs are often effective in neuropathic pain management, the antinociceptive activity for two the promising compounds—namely, 6 and 19—was also investigated in the formalin model of tonic pain. Additionally, for the aforementioned compounds, the affinity for the voltage-gated sodium and calcium channels, as well as GABA_A and TRPV1 receptors, was determined. As a result, the most probable molecular mechanism of action for the most active compound 6 relies on interaction with neuronal voltage-sensitive sodium (site 2) and L-type calcium channels. Compounds 6 and 19 were also tested for their neurotoxic and hepatotoxic properties and showed no significant cytotoxic effect.

The ups and downs of alkyl-carbamates in epilepsy therapy: How does cenobamate differ?

Since 1955, several alkyl-carbamates have been developed for the treatment of anxiety and epilepsy, including meprobamate, flupirtine, felbamate, retigabine, carisbamate, and cenobamate. They have each enjoyed varying levels of success as antiseizure drugs; however, they have all been plagued by the emergence of serious and sometimes life-threatening adverse events. In this review, we compare and contrast their predominant molecular mechanisms of action, their antiseizure profile, and where possible, their clinical efficacy. The preclinical, clinical, and mechanistic profile of the prototypical γ-aminobutyric acidergic (GABAergic) modulator phenobarbital is included for comparison. Like phenobarbital, all of the clinically approved alkyl-carbamates share an ability to enhance inhibitory neurotransmission through modulation of the GABA_A receptor, although the specific mechanism of interaction differs among the different drugs discussed. In addition, several alkyl-carbamates have been shown to interact with voltage-gated ion channels. Flupirtine and retigabine share an ability to activate K⁺ currents mediated by KCNQ (Kv7) K⁺ channels, and felbamate, carisbamate, and cenobamate have been shown to block Na⁺ channels. In contrast to other alkyl-carbamates, cenobamate seems to be unique in its ability to preferentially attenuate the persistent rather than transient Na⁺ current. Results from recent randomized controlled clinical trials with cenobamate suggest that this newest antiseizure alkyl-carbamate possesses a degree of efficacy not witnessed since felbamate was approved in 1993. Given that ceno-bamate's mechanistic profile is unique among the alkyl-carbamates, it is not clear whether this impressive efficacy reflects an as yet undescribed mechanism of action or whether it possesses a unique synergy between its actions at the GABA_A receptor and on persistent Na⁺ currents. The high efficacy of cenobamate is, however, tempered by the risk of serious rash and low tolerability at higher doses, meaning that further safety studies and clinical experience are needed to determine the true clinical value of cenobamate.

1,2,4-Triazole-based anticonvulsant agents with additional ROS scavenging activity are effective in a model of pharmacoresistant epilepsy

There are numerous studies supporting the contribution of oxidative stress to the pathogenesis of epilepsy. Prolonged oxidative stress is associated with the overexpression of ATP-binding cassette transporters, which results in antiepileptic drugs resistance. During our studies, three 1,2,4-triazole-3-thione derivatives were evaluated for the antioxidant activity and anticonvulsant effect in the 6 Hz model of pharmacoresistant epilepsy. The investigated compounds exhibited 2-3 times more potent anticonvulsant activity than valproic acid in 6 Hz test in mice, which is well-established preclinical model of pharmacoresistant epilepsy. The antioxidant/ROS scavenging activity was confirmed in both single-electron transfer-based methods (DPPH and CUPRAC) and during flow cytometric analysis of total ROS activity in U-87 MG cells. Based on the enzymatic studies on human carbonic anhydrases (CAs), acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), one can assume that the herein investigated drug candidates will not impair the cognitive processes mediated by CAs and will have minimal off-target cholinergic effects.

Polygonogram and isobolographic analysis of interactions between various novel antiepileptic drugs in the 6-Hz corneal stimulation-induced seizure model in mice

Pharmacotherapy with two antiepileptic drugs in combination is usually prescribed to epilepsy patients with refractory seizures. The choice of antiepileptic drugs in combination should be based on synergistic cooperation of the drugs with respect to suppression of seizures. The selection of synergistic interactions between antiepileptic drugs is challenging issue for physicians, especially, if 25 antiepileptic drugs are currently available and approved to treat epilepsy patients. The aim of this study was to determine all possible interactions among 5 second-generation antiepileptic drugs (gabapentin (GBP), lacosamide (LCM), levetiracetam (LEV), pregabalin (PGB) and retigabine (RTG)) in the 6-Hz corneal stimulation-induced seizure model in adult male albino Swiss mice. The anticonvulsant effects of 10 various two-drug combinations of antiepileptic drugs were evaluated with type I isobolographic analysis associated with graphical presentation of polygonogram to visualize the types of interactions. Isobolographic analysis revealed that 7 two-drug combinations of LEV+RTG, LEV+LCM, GBP+RTG, PGB+LEV, GBP+LEV, PGB+RTG, PGB+LCM were synergistic in the 6-Hz corneal stimulation-induced seizure model in mice. The additive interaction was observed for the combinations of GBP+LCM, GBP+PGB, and RTG+LCM in this seizure model in mice. The most beneficial combination, offering the highest level of synergistic suppression of seizures in mice was that of LEV+RTG, whereas the most additive combination that protected the animals from seizures was that reporting additivity for RTG+LCM. The strength of interaction for two-drug combinations can be arranged from the synergistic to the additive, as follows: LEV+RTG > LEV+LCM > GBP+RTG > PGB+LEV > GBP+LEV > PGB+RTG > PGB+LCM > GBP+LCM > GBP+PGB > RTG+LCM.

Anticonvulsant and neurotoxic effects of a novel 1,2,4-triazole-3-thione derivative (TPF-34) and its isobolographic interaction profile with classical antiepileptic drugs in mice

BACKGROUND

Anticonvulsant and acute toxic effects of 5-[(3-fluorophenyl)ethyl]-4-(n-hexyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (TPF-34)-a candidate for novel antiepileptic drug-were examined in the maximal electroshock-induced seizure (MES) model and rotarod test in mice. The interaction profile of TPF-34 with four classical antiepileptic drugs (carbamazepine, phenobarbital, phenytoin and valproate) was also studied in the mouse MES model.

METHODS

Both ED₅₀ and TD₅₀ values for TPF-34 were determined at four treatment times (15, 30, 60 and 120 min after i.p. administration) in the MES model and rotarod test in adult male albino Swiss mice, respectively. The influence of TPF-34 on the protective anticonvulsant action of carbamazepine, phenobarbital, phenytoin and valproate in the mouse MES model was assessed with isobolographic analysis of interaction. Total brain antiepileptic drug concentrations were measured with fluorescence polarization immunoassay.

RESULTS

TPF-34, when administered alone at four pretreatment times (15, 30, 60 and 120 min before experiments), possessed a favorable preclinical profile with the protective index (a ratio of TD₅₀ and ED₅₀ values) ranging from 2.89 to 3.53. Moreover, TPF-34, when combined with carbamazepine, phenobarbital, phenytoin and valproate, exerted an additive interaction in the MES model in mice. TPF-34 had no impact on total brain antiepileptic drug concentrations in mice.

CONCLUSIONS

A protective index value higher than 3 allows recommending TPF-34 as a promising antiepileptic drug candidate for further preclinical testing using other experimental seizure models. The additive interaction of TPF-34 with carbamazepine, phenobarbital, phenytoin and valproate in the mouse MES model is worthy of recommendation to further clinical studies.

A face-to-face comparison of the intra-amygdala and intrahippocampal kainate mouse models of mesial temporal lobe epilepsy and their utility for testing novel therapies

OBJECTIVE

Intracranial (intrahippocampal or intra-amygdala) administration of kainate in rodents leads to spatially restricted brain injury and development of focal epilepsy with characteristics that resemble mesial temporal lobe epilepsy. Such rodent models are used both in the search for more effective antiseizure drugs (ASDs) and in the development of antiepileptogenic strategies. However, it is not clear which of the models is best suited for testing different types of epilepsy therapies.

METHODS

In the present study, we performed a face-to-face comparison of the intra-amygdala kainate (IAK) and intrahippocampal kainate (IHK) mouse models using the same mouse inbred strain (C57BL/6). For comparison, some experiments were performed in mouse outbred strains.

RESULTS

Intra-amygdala kainate injection led to more severe status epilepticus and higher mortality than intrahippocampal injection. In male C57BL/6 mice, the latent period to spontaneous recurrent seizures (SRSs) was short or absent in both models, whereas a significantly longer latent period was determined in NMRI and CD-1 outbred mice. When SRSs were recorded from the ipsilateral hippocampus, relatively frequent electroclinical seizures were determined in the IAK model, whereas only infrequent electroclinical seizures but extremely frequent focal electrographic seizures were determined in the IHK model. As a consequence of the differences in SRS frequency, prolonged video-electroencephalographic monitoring and drug administration were needed for testing efficacy of the benchmark ASD carbamazepine in the IAK model, whereas acute drug testing was possible in the IHK model. In both models, carbamazepine was only effective at high doses, indicating ASD resistance to this benchmark drug.

SIGNIFICANCE

We found a variety of significant differences between the IAK and IHK models, which are important when deciding which of these models is best suited for studies on novel epilepsy therapies. The IAK model appears particularly interesting for studies on disease-modifying treatments, whereas the IHK model is well suited for studying the antiseizure activity of novel ASDs against difficult-to-treated focal seizures.

Klotho deficiency affects the spine morphology and network synchronization of neurons

Klotho-deficient mice rapidly develop cognitive impairment and show some evidence of the onset of neurodegeneration. However, it is impossible to investigate the long-term consequences on the brain because of the dramatic shortening of lifespan caused by systemic klotho deficiency. As klotho expression is downregulated with advancing organismal age, understanding the mechanisms of klotho action is important for developing novel strategies to support healthy brain aging. Previously, we reported that klotho-deficient mice show enhanced long-term potentiation prior to the onset of cognitive impairment. To inform this unusual phenotype, herein, we examined neuronal structure and in vitro synaptic function. Our results indicate that klotho deficiency causes the population of dendritic spines to shift towards increased head diameter and decreased length consistent with mature, mushroom type spines. Multi-electrode array recordings from klotho-deficient neurons show increased synchronous firing and activity changes reflective of increased neuronal network activity. Supplementation of the neuronal growth media with recombinant shed klotho corrected some but not all of the activity changes caused by klotho deficiency. Last, in vivo we found that klotho-deficient mice have a decreased latency to induced seizure activity. Together these data show that klotho-deficient memory impairments are underpinned by structural and functional changes that may preclude ongoing normal cognition.

The effects of dairy products on seizure tendency in mice

Epilepsy is a common neurological disorder which occurs as a result of a spontaneous electrical discharge in the brain. According to recent studies there might be a relationship between specific diet and seizure occurrence. Casein is an important protein of milk which often causes hypersensitivity. It seems the release of inflammatory cytokines during the process of immune system response alter the blood-brain-barrier (BBB) integrity and lead to neuronal inflammation which could constitute on epileptogenic focus. On the other hand, several studies represent full-fat milk or higher fat dairy products as an effective anti-inflammatory factor which elevate seizure threshold. The aim of present study was investigation of acute and chronic effects of dairy products including dough (a yogurt-based beverage), cheese, low and high fat yogurt and milk on pentylenetetrazole (PTZ)-induced seizures or electroshock in mice. The results of study indicated that lower fat dairy products reduced seizure threshold in intravenous PTZ-induced seizure as well as reduction in myoclonic and clonic jerk latencies in intraperitoneal PTZ-induced seizure. High fat products or cheese reduced seizure activity in both PTZ-induced models. Meanwhile both acute and chronic administration of dairy products had no effect on an electroshock-induced seizure. Therefore, diet-related seizures may depend upon the method which seizures are provoked.

Effect of carbamazepine on spontaneous recurrent seizures recorded from the dentate gyrus in rats with kainate-induced epilepsy

OBJECTIVE

Animal models of chronic epilepsy with spontaneous recurrent seizures (SRSs) may be useful in the discovery and mechanistic analyses of antiseizure drugs (ASDs). Carbamazepine (CBZ), a widely used ASD with a well-defined mechanism, was analyzed in this proof-of-principle study to determine how a traditional ASD affects the properties of SRSs.

METHODS

The effects of CBZ on electrographic SRSs recorded from the dentate gyrus were studied in freely behaving rats using a repeated, low-dose kainate model of acquired epilepsy with a repeated-measures, crossover protocol.

RESULTS

Almost all seizure durations were >20 seconds. Both seizure likelihood and duration appeared to be similar between 1 and 8 hours after individual CBZ injections. CBZ-induced decreases in seizure frequency were not significant at 10 mg/kg; however, at 30 mg/kg, seizure frequency was significantly reduced for convulsive but not nonconvulsive seizures. At 100 mg/kg, CBZ strongly suppressed both convulsive and nonconvulsive seizures. Although CBZ had a dose-dependent effect on seizure frequency, CBZ did not affect seizure duration at any dose. The preceding interictal interval did not affect seizure duration; however, at 30 mg/kg CBZ, nearly all seizures were nonconvulsive when the interictal interval was <30 minutes (ie, during clusters).

SIGNIFICANCE

Increased doses of CBZ (10-100 mg/kg) suppressed the frequency but not the duration of convulsive and nonconvulsive seizures in the repeated, low-dose kainate model. The repeated-measures, crossover protocol, which requires relatively few animals and compensates for progressive increases in seizure frequency during epileptogenesis after status epilepticus, allowed quantitative analyses of clinically relevant and translatable properties of SRSs.

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.

Interleukin-1 Receptor in Seizure Susceptibility after Traumatic Injury to the Pediatric Brain

Epilepsy after pediatric traumatic brain injury (TBI) is associated with poor quality of life. This study aimed to characterize post-traumatic epilepsy in a mouse model of pediatric brain injury, and to evaluate the role of interleukin-1 (IL-1) signaling as a target for pharmacological intervention. Male mice received a controlled cortical impact or sham surgery at postnatal day 21, approximating a toddler-aged child. Mice were treated acutely with an IL-1 receptor antagonist (IL-1Ra; 100 mg/kg, s.c.) or vehicle. Spontaneous and evoked seizures were evaluated from video-EEG recordings. Behavioral assays tested for functional outcomes, postmortem analyses assessed neuropathology, and brain atrophy was detected by ex vivo magnetic resonance imaging. At 2 weeks and 3 months post-injury, TBI mice showed an elevated seizure response to the convulsant pentylenetetrazol compared with sham mice, associated with abnormal hippocampal mossy fiber sprouting. A robust increase in IL-1β and IL-1 receptor were detected after TBI. IL-1Ra treatment reduced seizure susceptibility 2 weeks after TBI compared with vehicle, and a reduction in hippocampal astrogliosis. In a chronic study, IL-1Ra-TBI mice showed improved spatial memory at 4 months post-injury. At 5 months, most TBI mice exhibited spontaneous seizures during a 7 d video-EEG recording period. At 6 months, IL-1Ra-TBI mice had fewer evoked seizures compared with vehicle controls, coinciding with greater preservation of cortical tissue. Findings demonstrate this model's utility to delineate mechanisms underlying epileptogenesis after pediatric brain injury, and provide evidence of IL-1 signaling as a mediator of post-traumatic astrogliosis and seizure susceptibility.SIGNIFICANCE STATEMENT Epilepsy is a common cause of morbidity after traumatic brain injury in early childhood. However, a limited understanding of how epilepsy develops, particularly in the immature brain, likely contributes to the lack of efficacious treatments. In this preclinical study, we first demonstrate that a mouse model of traumatic injury to the pediatric brain reproduces many neuropathological and seizure-like hallmarks characteristic of epilepsy. Second, we demonstrate that targeting the acute inflammatory response reduces cognitive impairments, the degree of neuropathology, and seizure susceptibility, after pediatric brain injury in mice. These findings provide evidence that inflammatory cytokine signaling is a key process underlying epilepsy development after an acquired brain insult, which represents a feasible therapeutic target to improve quality of life for survivors.

Additive interactions between retigabine and oxcarbazepine in the chimney test and the model of generalized tonic-clonic seizures in mice

Introduction. Patients with pharmacoresistant epilepsy are usually treated with two or more antiepileptic drugs (AEDs). The search for therapeutically efficacious AED combinations is still a challenging issue for clinicians and epileptologists throughout the world.

Aim. To determine the interaction profile for the combination of retigabine (RTG) and oxcarbazepine (OXC) in both, the model of tonic-clonic seizures, the maximal electroshock (MES)-induced seizure model and chimney test (motor performance) in adult male albino Swiss mice.

Methods. Isobolographic analysis (type I) was applied to characterize interactions for the combination of RTG with OXC with respect to its anticonvulsant and acute side (neurotoxic) effects, as determined in the MES and chimney tests, respectively.

Results. The combination of RTG with OXC at the fixed-ratios of 1:3, 1:1 and 3:1 produced additive interactions in the MES test in mice. Similarly, the combination of RTG with OXC at the fixed-ratio of 1:1 produced additive interaction with a tendency towards sub-additivity in the chimney test in mice. Measurement of total brain concentrations of both AEDs revealed that RTG did not affect total brain concentrations of OXC and inversely, OXC had no impact on RTG’s total brain concentrations, confirming pharmacodynamic interaction between the drugs.

Conclusions. The additive pharmacodynamic interactions in both the MES and chimney tests in mice were observed for the combination of RTG with OXC.

Knockout of P-glycoprotein does not alter antiepileptic drug efficacy in the intrahippocampal kainate model of mesial temporal lobe epilepsy in mice

Pharmacoresistance to antiepileptic drugs (AEDs) is a major challenge in epilepsy therapy, affecting at least 30% of patients. Thus, there is considerable interest in the mechanisms responsible for such pharmacoresistance, with particular attention on the specific cellular and molecular factors that lead to reduced drug sensitivity. Current hypotheses of refractory epilepsy include the multidrug transporter hypothesis, which posits that increased expression or function of drug efflux transporters, such as P-glycoprotein (Pgp), in brain capillaries reduces the local concentration of AEDs in epileptic brain regions to subtherapeutic levels. In the present study, this hypothesis was addressed by evaluating the efficacy of six AEDs in wildtype and Pgp deficient Mdr1a/b(-/-) mice in the intrahippocampal kainate model of mesial temporal lobe epilepsy. In this model, frequent focal electrographic seizures develop after an initial kainate-induced status epilepticus. These seizures are resistant to major AEDs, but the mechanisms of this resistance are unknown. In the present experiments, the focal nonconvulsive seizures were resistant to carbamazepine and phenytoin, whereas high doses of valproate and levetiracetam exerted moderate and phenobarbital and diazepam marked anti-seizure effects. All AEDs suppressed generalized convulsive seizures. No significant differences between wildtype and Pgp-deficient mice were observed in anti-seizure drug efficacies. Also, the individual responder and nonresponder rates in each experiment did not differ between mouse genotypes. This does not argue against the multidrug transporter hypothesis in general, but indicates that Pgp is not involved in the mechanisms explaining that focal electrographic seizures are resistant to some AEDs in the intrahippocampal mouse model of partial epilepsy. This was substantiated by the finding that epileptic wildtype mice do not exhibit increased Pgp expression in this model.

Anticonvulsant and antinociceptive activity of new amides derived from 3-phenyl-2,5-dioxo-pyrrolidine-1-yl-acetic acid in mice

The aim of the present experiments was to examine the anticonvulsant and antinociceptive activity of five new amides derived from 3-phenyl-2,5-dioxo-pyrrolidine-1-yl-acetic acid in animal models of seizures and pain. The antiseizure activity was investigated in three acute models of seizures, namely, the maximal electroshock (MES), the subcutaneous pentylenetetrazole (scPTZ), and 6Hz psychomotor seizure tests in mice. The antinociceptive properties were estimated in the formalin model of tonic pain, and in the oxaliplatin-induced neuropathic pain model in mice. Considering drug safety evaluation, acute neurological toxicity was determined in the rotarod test. Three tested compounds (3, 4, and 7) displayed a broad spectrum of anticonvulsant activity and showed better protective indices than those obtained for MES/scPTZ/6Hz active reference drug - valproic acid. Furthermore, three compounds (3, 4, and 6) demonstrated a significant antinociceptive effect in the formalin test, as well as antiallodynic activity in the oxaliplatin-induced neuropathic pain model. Among the tested agents, compounds 3 and 4 displayed not only antiseizure properties, but also collateral prominent analgesic properties. The in vitro binding study indicated that the plausible mechanism of action of chosen compound (4) was the influence on neuronal voltage-sensitive sodium (site 2) and L-type calcium channels.

Effects of acute and chronic administration of neurosteroid dehydroepiandrosterone sulfate on neuronal excitability in mice

Background

Neurosteroid dehydroepiandrosterone sulfate (DHEAS) has been associated with important brain functions, including neuronal survival, memory, and behavior, showing therapeutic potential in various neuropsychiatric and cognitive disorders. However, the antagonistic effects of DHEAS on γ-amino-butyric acid_A receptors and its facilitatory action on glutamatergic neurotransmission might lead to enhanced brain excitability and seizures and thus limit DHEAS therapeutic applications. The aim of this study was to investigate possible age and sex differences in the neuronal excitability of the mice following acute and chronic DHEAS administration.

Methods

DHEAS was administered intraperitoneally in male and female adult and old mice either acutely or repeatedly once daily for 4 weeks in a 10 mg/kg dose. To investigate the potential proconvulsant properties of DHEAS, we studied the effects of acute and chronic DHEAS treatment on picrotoxin-, pentylentetrazole-, and N-methyl-D-aspartate-induced seizures in mice. The effects of acute and chronic DHEAS administration on the locomotor activity, motor coordination, and body weight of the mice were also studied. We also investigated the effects of DHEAS treatment on [³H]flunitrazepam binding to the mouse brain membranes.

Results

DHEAS did not modify the locomotor activity, motor coordination, body weight, and brain [³H]flunitrazepam binding of male and female mice. The results failed to demonstrate significant effects of single- and long-term DHEAS treatment on the convulsive susceptibility in both adult and aged mice of both sexes. However, small but significant changes regarding sex differences in the susceptibility to seizures were observed following DHEAS administration to mice.

Conclusion

Although our findings suggest that DHEAS treatment might be safe for various potential therapeutic applications in adult as well as in old age, they also support subtle interaction of DHEAS with male and female hormonal status, which may underline observed sex differences in the relationship between DHEAS and various health outcomes.

Neto2-null mice have impaired GABAergic inhibition and are susceptible to seizures

Neto2 is a transmembrane protein that interacts with the neuron-specific K⁺-Cl⁻ cotransporter (KCC2) in the central nervous system (CNS). Efficient KCC2 transport is essential for setting the neuronal Cl⁻ gradient, which is required for fast GABAergic inhibition. Neto2 is required to maintain the normal abundance of KCC2 in neurons, and increases KCC2 function by binding to the active oligomeric form of this cotransporter. In the present study, we characterized GABAergic inhibition and KCC2-mediated neuronal chloride homeostasis in pyramidal neurons from adult hippocampal slices. Using gramicidin perforated patch clamp recordings we found that the reversal potential for GABA (E_GABA) was significantly depolarized. We also observed that surface levels of KCC2 and phosphorylation of KCC2 serine 940 (Ser940) were reduced in Neto2^−/− neurons compared to wild-type controls. To examine GABAergic inhibition we recorded spontaneous inhibitory postsynaptic currents (sIPSCs) and found that Neto2^−/− neurons had significant reductions in both their amplitude and frequency. Based on the critical role of Neto2 in regulating GABAergic inhibition we rationalized that Neto2-null mice would be prone to seizure activity. We found that Neto2-null mice demonstrated a decrease in the latency to pentylenetetrazole (PTZ)-induced seizures and an increase in seizure severity.

Design, synthesis and biological evaluation of new hybrid anticonvulsants derived from N-benzyl-2-(2,5-dioxopyrrolidin-1-yl)propanamide and 2-(2,5-dioxopyrrolidin-1-yl)butanamide derivatives

The purpose of this study was to synthesize the library of 33 new N-benzyl-2-(2,5-dioxopyrrolidin-1-yl)propanamides, 2-(3-methyl-2,5-dioxopyrrolidin-1-yl)propanamides, and 2-(2,5-dioxopyrrolidin-1-yl)butanamides as potential new hybrid anticonvulsant agents. These hybrid molecules join the chemical fragments of well-known antiepileptic drugs (AEDs) such as ethosuximide, levetiracetam, and lacosamide. The coupling reaction of the 2-(2,5-dioxopyrrolidin-1-yl)propanoic acid, 2-(3-methyl-2,5-dioxopyrrolidin-1-yl)propanoic acid, or 2-(2,5-dioxopyrrolidin-1-yl)butanoic acid with the appropriately substituted benzylamines in the presence of the coupling reagent, N,N-carbonyldiimidazole (CDI) generated the final compounds 4-36. Spectral data acquired via (1)H NMR, (13)C NMR, and LC-MS confirmed the chemical structures of the newly prepared compounds. The initial anticonvulsant screening was performed in mice intraperitoneally (ip), using the maximal electroshock seizure (MES) and subcutaneous pentylenetetrazole (scPTZ) seizure tests. The rotarod test determined the acute neurological toxicity (NT). The results of preliminary pharmacological screening revealed that 25 compounds showed protection in half or more of the animals tested in the MES and/or scPTZ seizure models at the fixed dose of 100mg/kg. The broad spectra of activity across the preclinical seizure models displayed compounds 4, 7, 8, 13, 15-18, 24, and 26. The quantitative pharmacological studies in mice demonstrated the highest protection for compounds 4 (ED50 MES=67.65 mg/kg, ED50scPTZ=42.83 mg/kg); 8 (ED50 MES=54.90 mg/kg, ED50scPTZ=50.29 mg/kg); and 20 (ED50scPTZ=47.39 mg/kg). These compounds were distinctly more potent and provided better safety profiles in the rotarod test compared to valproic acid or ethosuximide, which were used as model AEDs. Compound 8 underwent only a slight metabolic change by the human liver microsomes (HLMs), and also did not affect the activity of human cytochrome P450 isoform, CYP3A4, in the in vitro assays.

Studies on the anticonvulsant activity of 4-alkyl-1,2,4-triazole-3-thiones and their effect on GABAergic system

A series of 4-alkyl-5-(3-chlorobenzyl/2,3-dichlorophenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thiones (1a-14a) were designed, synthesized and screened for their anticonvulsant properties. Moreover, the acute adverse-effect profile of the active compounds (1a-7a, 12a) with respect to impairment of motor performance was evaluated in the chimney test. Among 4-alkyl-5-(3-chlorobenzyl)-2,4-dihydro-3H-1,2,4-triazole-3-thiones, ethyl, butyl, pentyl, hexyl, and heptyl derivatives administered intraperitoneally in a dose of 300 mg/kg protected 100% of the tested animals at four pretreatment times (i.e., 15, 30, 60, 120 min). Taking into account the median effective and toxic doses as well as the time-course profile of anticonvulsant activity, 5-(3-chlorobenzyl)-4-hexyl-2,4-dihydro-3H-1,2,4-triazole-3-thione (4a) was proposed as the best tolerated and the most promising potential drug candidate. Finally, a radioligand binding assay was used to check whether the anticonvulsant activity of 4-alkyl-1,2,4-triazole-3-thiones was a result of their interactions (direct or allosteric) with GABAA receptor complex and/or their affinity to benzodiazepine (BDZ) binding sites.

Studies on the anticonvulsant activity and influence on GABA-ergic neurotransmission of 1,2,4-triazole-3-thione- based compounds

The anticonvulsant activity of several 1,2,4-triazole-3-thione derivatives on mouse maximal electroshock-induced seizures was tested in this study. Characteristic features of all active compounds were rapid onset of action and long lasting effect. Structure-activity observations showed that the probability of obtaining compounds exerting anticonvulsant activity was much higher when at least one of the phenyl rings attached to 1,2,4-triazole nucleus had a substituent at the para position. The obtained results, moreover, permit us to conclude that despite the structural similarity of loreclezole (second-generation anticonvulsant drug) and the titled compounds, their anticonvulsant activity is achieved via completely different molecular mechanisms.

Perampanel, an antagonist of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors, for the treatment of epilepsy: studies in human epileptic brain and nonepileptic brain and in rodent models

Perampanel [Fycompa, 2-(2-oxo-1-phenyl-5-pyridin-2-yl-1,2-dihydropyridin-3-yl)benzonitrile hydrate 4:3; Eisai Inc., Woodcliff Lake, NJ] is an AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptor antagonist used as an adjunctive treatment of partial-onset seizures. We asked whether perampanel has AMPA receptor antagonist activity in both the cerebral cortex and hippocampus associated with antiepileptic efficacy and also in the cerebellum associated with motor side effects in rodent and human brains. We also asked whether epileptic or nonepileptic human cortex is similarly responsive to AMPA receptor antagonism by perampanel. In rodent models, perampanel decreased epileptic-like activity in multiple seizure models. However, doses of perampanel that had anticonvulsant effects were within the same range as those engendering motor side effects. Perampanel inhibited native rat and human AMPA receptors from the hippocampus as well as the cerebellum that were reconstituted into Xenopus oocytes. In addition, with the same technique, we found that perampanel inhibited AMPA receptors from hippocampal tissue that had been removed from a patient who underwent surgical resection for refractory epilepsy. Perampanel inhibited AMPA receptor-mediated ion currents from all the tissues investigated with similar potency (IC50 values ranging from 2.6 to 7.0 μM). Cortical slices from the left temporal lobe derived from the same patient were studied in a 60-microelectrode array. Large field potentials were evoked on at least 45 channels of the array, and 10 μM perampanel decreased their amplitude and firing rate. Perampanel also produced a 33% reduction in the branching parameter, demonstrating the effects of perampanel at the network level. These data suggest that perampanel blocks AMPA receptors globally across the brain to account for both its antiepileptic and side-effect profile in rodents and epileptic patients.

Anticonvulsant profile of 2-ethylthio-7-methyl-4-(4-methylphenyl)pyrazolo[1,5-a][1,3,5]triazine

This work evaluates the central nervous effects in ICR strain mice of 2-ethylthio-7-methyl-4-(4-methylphenyl)pyrazolo[1,5-a][1,3,5]triazine (MH4b1), a compound obtained by an efficient one-step reaction of S,S-diethyl 4-methylbenzoylimidodithiocarbonate with 5-amino-3-methyl-1H-pyrazole, in order to assess its neuro-pharmacological profile. The tests applied were: maximal electroshock seizure (MES), pentylenetetrazole (PTZ) seizures, forced swimming, plus maze, marble burying, sleeping time, rota-rod and catalepsy. In addition, MH4b1 binding to the benzodiazepine site of the GABA-A receptor and MH4b1 inhibition of monoamine oxidase (MAO) subtypes A and B were evaluated. MH4b1 showed anticonvulsant effects in a dose dependent manner (30-300 mg/kg, p.o.) against MES and inhibition of MAO-B (IC50: 24.5 µM) without activity at the benzodiazepine site. These data suggest that MH4b1 has anticonvulsant properties related to MAO-B inhibition.

Antisense reduction of tau in adult mice protects against seizures

Tau, a microtubule-associated protein, is implicated in the pathogenesis of Alzheimer's Disease (AD) in regard to both neurofibrillary tangle formation and neuronal network hyperexcitability. The genetic ablation of tau substantially reduces hyperexcitability in AD mouse lines, induced seizure models, and genetic in vivo models of epilepsy. These data demonstrate that tau is an important regulator of network excitability. However, developmental compensation in the genetic tau knock-out line may account for the protective effect against seizures. To test the efficacy of a tau reducing therapy for disorders with a detrimental hyperexcitability profile in adult animals, we identified antisense oligonucleotides that selectively decrease endogenous tau expression throughout the entire mouse CNS--brain and spinal cord tissue, interstitial fluid, and CSF--while having no effect on baseline motor or cognitive behavior. In two chemically induced seizure models, mice with reduced tau protein had less severe seizures than control mice. Total tau protein levels and seizure severity were highly correlated, such that those mice with the most severe seizures also had the highest levels of tau. Our results demonstrate that endogenous tau is integral for regulating neuronal hyperexcitability in adult animals and suggest that an antisense oligonucleotide reduction of tau could benefit those with epilepsy and perhaps other disorders associated with tau-mediated neuronal hyperexcitability.

Loss of hippocampal interneurons and epileptogenesis: a comparison of two animal models of acquired epilepsy

Reduced hippocampal GABAergic inhibition is acknowledged to be associated with epilepsy. However, there are no studies that had quantitatively compared the loss of various interneuron populations in different models of epilepsy. We tested a hypothesis that the more severe the loss of hippocampal interneurons, the more severe was the epilepsy. Epileptogenesis was triggered in adult rats by status epilepticus (SE) (56 SE, 24 controls) or by traumatic brain injury (TBI) (45 TBI, 23 controls). The total number of hippocampal parvalbumin (PARV), cholecystokinin (CCK), calretinin (CR), somatostatin (SOM), or neuropeptide Y (NPY) positive neurons was estimated using unbiased stereology at 1 or 6 months post-insult. The rats with TBI had no spontaneous seizures but showed increased seizure susceptibility. Eleven of the 28 rats (39 %) in the SE group had spontaneous seizures. The most affected hippocampal area after TBI was the ipsilateral dentate gyrus, where 62 % of PARV-immunoreactive (ir) (p < 0.001 compared to controls), 77 % of CR-ir (p < 0.05), 46 % of SOM-ir (p < 0.001), and 59 % of NPY-ir (p < 0.001) cells remained at 1 month after TBI. At 6 months post-TBI, only 35 % of PARV-ir (p < 0.001 compared to controls), 63 % of CCK-ir (p < 0.01), 74 % of CR-ir (p < 0.001), 55 % of SOM-ir (p < 0.001), and 51 % of NPY-ir (p < 0.001) cells were remaining. Moreover, the reduction in PARV-ir, CCK-ir, and CR-ir neurons was bilateral (all p < 0.05). Substantial reductions in different neuronal populations were also found in subfields of the CA3 and CA1. In rats with epilepsy after SE, the number of PARV-ir neurons was reduced in the ipsilateral CA1 (80 % remaining, p < 0.05) and the number of NPY-ir neurons bilaterally in the dentate gyrus (33-37 %, p < 0.01) and the CA3 (54-57 %, p < 0.05). Taken together, interneuron loss was substantially more severe, widespread, progressive, and included more interneuron subclasses after TBI than after SE. Interneurons responsible for perisomatic inhibition were more vulnerable to TBI than those providing dendritic inhibition. Unlike expected, we could not demonstrate any etiology-independent link between the severity of hippocampal interneuron loss and the overall risk of spontaneous seizures.

Synthesis and anticonvulsant activity evaluation of 8-alkoxy-5-(4H-1,2,4-triazol-4-yl)quinoline derivatives

Two series of 8-alkoxy-5-(4H-1,2,4-triazol-4-yl)quinolines and 8-alkoxy-5-(2H-1,2,4-triazol-3-one-4-yl)quinolines were synthesized. The anticonvulsant activity of these compounds was evaluated with maximal electroshock seizure test and rotarod test. Among the synthesized compounds, 8-octoxy-5-(4H-1,2,4-triazol-4-yl)quinoline (4g) was the most active compound with ED(50) of 8.80 mg/kg, TD(50) of 176.03 mg/kg and protective index of 20.0. Its neurotoxicity was lower than all other synthesized compounds and also markedly lower than that of the reference drug carbamazepine. In addition, the potency of compound 4g against seizures induced by pentylenetetrazole, 3-mercaptopropionic acid, and bicuculline suggested its broad spectrum activity, and the mechanisms of action including inhibition of voltage-gated ion channels and modulation of GABAergic activity might involve in its anticonvulsant activity.

Synthesis, characterization and preliminary anticonvulsant evaluation of some 4-alkyl-1,2,4-triazoles

Designed and synthesized 4-alkyl-1,2,4-triazole-3-thione derivatives showed significant anticonvulsant activity, determined in the maximal electroshock-induced seizure (MES) test. The chemical structure of all new compounds was confirmed by spectral methods ((1)H NMR, (13)C NMR, IR, MS). A sensitive and selective method was elaborated for the determination of the anticonvulsant compounds levels in mice brain tissue, based on HPLC with diode array detector (DAD). Chromatographic tests showed that lack of anticonvulsant effect of two derivatives (15, 16) with long alkyl chains at N-4 position of the 1,2,4-triazole ring was due to the inability to cross the blood-brain barrier (BBB).