Assessment of the Novel Anti-Seizure Potential of Validamycin A Using Zebrafish Epilepsy Model.

Epilepsy is a prevalent neurological disorder characterized by recurrent seizures. Validamycin A (VA) is an antibiotic fungicide that inhibits trehalase activity and is widely used for crop protection in agriculture. In this study, we identified a novel function of VA as a potential anti-seizure medication in a zebrafish epilepsy model. Electroencephalogram (EEG) analysis demonstrated that VA reduced pentylenetetrazol (PTZ)-induced seizures in the brains of larval and adult zebrafish. Moreover, VA reduced PTZ-induced irregular movement in a behavioral assessment of adult zebrafish. The developmental toxicity test showed no observable anatomical alteration when the zebrafish larvae were treated with VA up to 10 µM within the effective range. The median lethal dose of VA in adult zebrafish was > 14,000 mg/kg. These results imply that VA does not demonstrate observable toxicity in zebrafish at concentrations effective for generating anti-seizure activity in the EEG and alleviating abnormal behavior in the PTZ-induced epileptic model. Furthermore, the effectiveness of VA was comparable to that of valproic acid. These results indicate that VA may have a potentially safer anti-seizure profile than valproic acid, thus offering promising prospects for its application in agriculture and medicine.

Comparing the efficacy of anti-seizure medications using matched cohorts on a large insurance claims database.

Epilepsy is a severe chronic neurological disease affecting 60 million people worldwide. Primary treatment is with anti-seizure medicines (ASMs), but many patients continue to experience seizures. We used retrospective insurance claims data on 280,587 patients with uncontrolled epilepsy (UE), defined as status epilepticus, need for a rescue medicine, or admission or emergency visit for an epilepsy code. We conducted a computational risk ratio analysis between pairs of ASMs using a causal inference method, in order to match 1034 clinical factors and simulate randomization. Data was extracted from the MarketScan insurance claims Research Database records from 2011 to 2015. The cohort consisted of individuals over 18 years old with a diagnosis of epilepsy who took one of eight ASMs and had more than a year of history prior to the filling of the drug prescription. Seven ASM exposures were analyzed: topiramate, phenytoin, levetiracetam, gabapentin, lamotrigine, valproate, and carbamazepine or oxcarbazepine (treated as the same exposure). We calculated the risk ratio of UE between pairs of ASM after controlling for bias with inverse propensity weighting applied to 1034 factors, such as demographics, confounding illnesses, non-epileptic conditions treated by ASMs, etc. All ASMs exhibited a significant reduction in the prevalence of UE, but three drugs showed pair-wise differences compared to other ASMs. Topiramate consistently was associated with a lower risk of UE, with a mean risk ratio range of 0.68-0.93 (average 0.82, CI: 0.56-1.08). Phenytoin and levetiracetam were consistently associated with a higher risk of UE with mean risk ratio ranges of 1.11 to 1.47 (average 1.13, CI 0.98-1.65) and 1.15 to 1.43 (average 1.2, CI 0.72-1.69), respectively. Large-scale retrospective insurance claims data - combined with causal inference analysis - provides an opportunity to compare the effect of treatments in real-world data in populations 1,000-fold larger than those in typical randomized trials. Our causal analysis identified the clinically unexpected finding of topiramate as being associated with a lower risk of UE; and phenytoin and levetiracetam as associated with a higher risk of UE (compared to other studied drugs, not to baseline). However, we note that our data set for this study only used insurance claims events, which does not comprise actual seizure frequencies, nor a clear picture of side effects. Our results do not advocate for any change in practice but demonstrate that conclusions from large databases may differ from and supplement those of randomized trials and clinical practice and therefore may guide further investigation.

Value contribution of cenobamate for the treatment of Focal-Onset Seizures (FOS) in patients with drug-resistant epilepsy (DRE) in Spain through reflective Multi-Criteria Decision Analysis (MCDA).

INTRODUCTION: Epilepsy is one of the most common neurological conditions worldwide. The main goal of its treatment is to achieve seizure freedom without intolerable adverse effects. However, despite the availability of many anti-seizure medications, including the latest options, called third-generation anti-seizure medications (ASMs), approximately 40% of people with epilepsy present drug-resistant epilepsy (DRE). Cenobamate is the first ASM approved in Spain for the adjunctive treatment of Focal-Onset Seizures (FOS) in adult patients with DRE. In a chronic disease with a portfolio of available ASMs, the decision to introduce a new therapeutic alternative must follow a holistic evaluation of value provided. Reflective Multi-Criteria Decision Analysis (MCDA) methodology allows to determine the value contribution of a treatment in a given indication considering all relevant criteria for healthcare decision-making in a transparent and systematic manner from the perspective of relevant stakeholders. PURPOSE: The aim of this study was to determine the relative value contribution of cenobamate in the treatment of FOS in patients with DRE compared with third-generation ASMs using reflective MCDA-based methodology. METHODS: A systematic literature review (combining biomedical databases and grey literature sources) was performed to populate the Evidence and Value: Impact on DEcisionMaking (EVIDEM) MCDA framework adapted to determine what represents value in the management of FOS in patients with DRE in Spain. The study was conducted in two phases. The first took place in 2021 with a multi-stakeholder group of eight participants. The second phase was conducted in 2022 with a multi-stakeholder group of 32 participants. Participants were trained in MCDA methodology and scored four evidence matrices (cenobamate vs. brivaracetam, vs. perampanel, vs. lacosamide and vs. eslicarbazepine acetate). Results were analyzed and discussed in a group meeting through reflective MCDA discussion methodology. RESULTS: DRE is considered a very severe condition associated with many important unmet needs, mainly with regard to the lack of more effective treatments to achieve the ultimate goal of treatment. Compared to third-generation ASMs, cenobamate is perceived to have a better efficacy profile based on improvements in responder rate and seizure freedom. Regarding safety, it is considered to have a similar profile to alternatives and a positive quality-of-life profile. Cenobamate results in lower direct medical costs (excluding pharmacological) and indirect costs. Overall, cenobamate is regarded as providing a high therapeutic impact and supported by high-quality evidence. CONCLUSIONS: Based on reflective MCDA methodology and stakeholders' experience in clinical management of epilepsy in Spain, cenobamate is perceived as a value-added option for the treatment of patients with DRE when compared with third-generation ASMs.

Cost-effectiveness of surgical treatment compared to medical treatment in patients with drug-refractory epilepsy: A systematic review.

BACKGROUND AND PURPOSE: Approximately 30% of epilepsy patients develop a drug-refractory epilepsy, that is, seizures cannot be controlled with antiepileptic drugs. Surgery has been evaluated as an effective but costly form of treatment. The aim of this systematic review is to synthesize the available evidence on the cost-effectiveness of surgical treatment compared to medical treatment for these patients. METHOD: A systematic literature search was performed in MEDLINE, Embase, PsycINFO, Cochrane Library and the National Health Service Economic Evaluation Database until September 2022. Title, abstract and full-text screening were conducted by two researchers. Original studies published in English or German analyzing the cost-effectiveness of surgical compared to medical treatment were included. Study characteristics, effectiveness measures, costs and incremental cost-effectiveness ratios (ICERs) were extracted. The quality of studies was assessed using the Drummond checklist. RESULTS: Fourteen studies were included. Most studies evaluated surgery as cost-effective. The ICER per patient seizure free ranged from dominant to purchasing power parity US dollars (PPP-USD) 479,275. The ICER per 1% seizure reduction ranged from PPP-USD 227 to PPP-USD 342. The ICER per year without seizures was PPP-USD 4202 and the ICER per quality-adjusted life-year ranged from dominant to PPP-USD 90,874. The studies varied greatly in their methodology and time horizon. CONCLUSION: Surgical treatment is cost-effective compared to medical treatment, especially when a lifetime horizon is adopted. It is concluded that all disease-specific costs should be considered over a long period when assessing the cost-effectiveness of epilepsy treatment. From an economic perspective, efforts should be made to improve access to surgical treatment for patients with drug-refractory epilepsy.

Pharmacoeconomics Aspects of Antiepileptic Drugs in Pediatric Patients with Epilepsy.

OBJECTIVE: This study assessed the differentiation of treatment costs with newer and older antiepileptic drugs (AEDs) through its correlation with treatment effectiveness and an adverse event (AE) in pediatric patients with epilepsy (PPE). METHODS: PPE on monotherapy of AEDs for the last 6 months were screened for this study. Seizure frequency during the study was compared with that within 6 months before the study. The following parameters were also assessed: quality of life in epilepsy, Pittsburgh Sleep Quality Index, and Liverpool AEs Profile. An incremental cost-effectiveness ratio (ICER) analysis based on the costs of pharmacotherapy was also performed. RESULTS: Out of 80 PPE, 67 completed the study, and 13 PPE were lost after failing to meet the inclusion criteria. A total of 56.71% of PPE were on newer AEDs, and 43.28% were on older AEDs. Newer and older AEDs did not differ significantly in seizure frequency reduction and quality of life parameters, although these were improved significantly during the study period. As per ICER, newer AEDs need an additional EUR 36.82 per unit reduction in seizure frequency. CONCLUSION: Newer AEDs have comparatively better efficacy, although not significantly better than older AEDs. However, the additional cost per unit improvement is quite high with newer AEDs, necessitating pharmacoeconomic consideration in pediatric epilepsy treatment.

Redefining the age-specific therapeutic ranges of lamotrigine for patients with epilepsy: A step towards optimizing treatment and increasing cost-effectiveness.

OBJECTIVE: The pharmacokinetics of lamotrigine exhibits age-related characteristics. Nevertheless, current evidence regarding the therapeutic range of lamotrigine has been derived almost exclusively from studies in adult patients, and the applicability of this therapeutic range to the pediatric population remains unclear. The purpose of this study was to establish the appropriate age-specific therapeutic ranges of lamotrigine corresponding to adequate clinical responses for patients with epilepsy. METHODS: This prospective cohort study of therapeutic drug monitoring included 582 Chinese epilepsy patients receiving lamotrigine monotherapy. Patients were divided into three age-related subgroups: (1) toddler and school-age group (2-12 years old, n = 168), (2) adolescent group (12-18 years old, n = 171), and (3) adult group (>18 years old, n = 243). Patients with a reduction in seizure frequency of 50 % or greater than baseline were defined as responders, and the remaining patients were non-responders. The relationship between lamotrigine serum concentrations and clinical response was assessed using multivariate logistic regression analysis. A receiver operating characteristic curve was generated to determine the representative cut-off values of lamotrigine trough levels, to distinguish responders from non-responders. The upper margin of the therapeutic range of lamotrigine was determined by developing concentration-effect curves for the three age-related subgroups. RESULTS: The median trough levels of lamotrigine were significantly higher in responders than in non-responders from all three age-related groups (P < 0.0001). Results of logistic regression analysis revealed that higher serum concentrations of lamotrigine predicted a higher probability that seizure frequency would be reduced by more than 50 % compared to baseline (adjusted odds ratio: 1.228, 95 % CI: 1.137-1.327; P < 0.0001), and younger children were less likely to be responders (adjusted odds ratio: 1.027, 95 % CI: 1.012-1.043; P = 0.001). Based on a trade-off between sensitivity and specificity, the optimal cut-off values for lamotrigine trough concentrations corresponding to clinical response were 3.29 mg/L, 2.06 mg/L, and 1.61 mg/L in the toddler and school-age group, adolescent group, and adult group, respectively. By reducing interpatient variability, the results of the concentration-effect curves suggested no additional clinical benefit from a continued increase of doses for lamotrigine concentrations exceeding 9.08 mg/L, 8.43 mg/L, and 10.38 mg/L in the toddler and school-age group, adolescent group, and adult group, respectively. In conclusion, the therapeutic ranges of lamotrigine trough concentrations corresponding to adequate clinical response were 3.29-9.08 mg/L in the toddler and school-age group, 2.06-8.43 mg/L in the adolescent group, and 1.61-10.38 mg/L in the adult group. CONCLUSIONS: The study determined age-specific therapeutic ranges corresponding to optimal clinical efficacy for lamotrigine. Our findings lay the foundation for catalyzing novel opportunities to optimize treatment and reduce therapeutic costs. Based on the age-specific therapeutic ranges identified in this study, individualized and cost-effective algorithms for lamotrigine treatment of epilepsy patients may be developed and validated in larger cohort studies of therapeutic drug monitoring.

Histopathological and Biochemical Assessment of Neuroprotective Effects of Sodium Valproate and Lutein on the Pilocarpine Albino Rat Model of Epilepsy.

Epilepsy is one of the most frequent neurological disorders characterized by an enduring predisposition to generate epileptic seizures. Oxidative stress is believed to directly participate in the pathways of neurodegenerations leading to epilepsy. Approximately, one-third of the epileptic patients who suffer from seizures do not receive effective medical treatment. Sodium valproate (SVP) is a commonly used antiepileptic drug (AED); however, it has toxic effects. Lutein (L), a carotenoid, has potent antioxidant and anti-inflammatory properties. The aim of this study was to determine the neuroprotective effect of sodium valproate (SVP) and lutein (L) in a rat model of pilocarpine- (PLC-) induced epilepsy. To achieve this aim, fifty rats were randomly divided into five groups. Group I: control, group II: received PLC (400 mg/kg intraperitoneally), group III: received PLC + SVP (500 mg/kg orally), group IV: received PLC + SVP + L (100 mg/kg orally), and group V: received (PLC + L). Racine Scale (RC) and latency period to onset seizure were calculated. After eight weeks, the hippocampus rotarod performance and histological investigations were performed. Oxidative stress was investigated in hippocampal homogenates. Results revealed that SVP and L, given alone or in combination, reduced the RC significantly, a significant delay in latency to PLC-kindling onset, and improved rotarod performance of rats compared with the PLC group. Moreover, L was associated with a reduction of oxidative stress in hippocampal homogenate, a significant decrease in serum tumor necrosis factor-alpha (TNF-α) level, and inhibition of cerebral injury and displayed antiepileptic properties in the PLC-induced epileptic rat model. Data obtained from the current research elucidated the prominent neuroprotective, antioxidant, and anti-inflammatory activities of lutein in this model. In conclusion, lutein cotreatment with AEDs is likely to be a promising strategy to improve treatment efficacy in patients suffering from epilepsy.

Assessment of Memory Function in Pilocarpine-induced Epileptic Mice.

Cognitive impairment is one of the most common comorbidities in temporal lobe epilepsy. To recapitulate epilepsy-associated cognitive decline in an animal model of epilepsy, we generated pilocarpine-treated chronic epileptic mice. We present a protocol for three different behavioral tests using these epileptic mice: novel object location (NL), novel object recognition (NO), and pattern separation (PS) tests to evaluate learning and memory for places, objects, and contexts, respectively. We explain how to set the behavioral apparatus and provide experimental procedures for the NL, NO, and PS tests following an open field test that measures the animals' basal locomotor activities. We also describe the technical advantages of the NL, NO, and PS tests with respect to other behavioral tests for assessing memory function in epileptic mice. Finally, we discuss possible causes and solutions for epileptic mice failing to make 30 s of good contact with the objects during the familiarization sessions, which is a critical step for successful memory tests. Thus, this protocol provides detailed information about how to assess epilepsy-associated memory impairments using mice. The NL, NO, and PS tests are simple, efficient assays that are appropriate for the evaluation of different kinds of memory in epileptic mice.

Electrophysiological and Neurochemical Assessment of Selenium Alone or Combined with Carbamazepine in an Animal Model of Epilepsy.

The present study aims to evaluate the efficacy of selenium (Se) alone or combined with carbamazepine (CBZ) against the adverse effects induced by the chemoconvulsant pentylenetetrazole (PTZ) in the cortex of adult male rats. Electrocorticogram (ECoG) and oxidative stress markers were implemented to evaluate the differences between treated and untreated animals. Animals were divided into five groups: control group that received i.p. saline injection, PTZ-treated group that received a single i.p. injection of PTZ (60 mg/kg) for induction of seizures followed by a daily i.p. injection of saline, Se-treated group that received an i.p. injection of sodium selenite (0.3 mg/kg/day) after PTZ administration, CBZ-treated group that received orally CBZ (80 mg/kg/day) after PTZ administration, and combination (Se plus CBZ)-treated group that received an oral administration of CBZ (80 mg/kg/day) followed by an i.p. injection of sodium selenite (0.3 mg/kg/day) after PTZ administration. Quantitative analyses of the ECoG indices and the neurochemical parameters revealed that Se and CBZ have mitigated the adverse effects induced by PTZ. The main results were decrease in the number of epileptic spikes, restoring the normal distribution of slow and fast ECoG frequencies and attenuation of most of the oxidative stress markers. However, there was an increase in lipid perioxidation marker in combined treatment of CBZ and Se. The electrophysiological and neurochemical data proved the potential of these techniques in evaluating the treatment's efficiency and suggest that supplementation of Se with antiepileptic drugs (AEDs) may be beneficial in ameliorating most of the alterations induced in the brain as a result of seizure insults and could be recommended as an adjunct therapy with AEDs.

A weight of evidence assessment approach for adverse outcome pathways.

The adverse outcome pathway (AOP) is a framework to mechanistically link molecular initiating events to adverse biological outcomes. From a regulatory perspective, it is of crucial importance to determine the confidence for the AOP in question as well as the quality of data available in supporting this evaluation. A weight of evidence approach has been proposed for this task, but many of the existing frameworks for weight of evidence evaluation are qualitative and there is not clear guidance regarding how weight of evidence should be calculated for an AOP. In this paper we advocate the use of a subject matter expertise driven approach for weight of evidence evaluation based on criteria and metrics related to data quality and the strength of causal linkages between key events. As a demonstration, we notionally determine weight of evidence scores for two AOPs: Non-competitive ionotropic GABA receptor antagonism leading to epileptic seizures, and Antagonist-binding and stabilization of a co-repressor to the peroxisome proliferator-activated receptor α (PPARα) signaling complex ultimately causing starvation-like weight loss.

Behavioural and histopathological assessment of the effects of periodic fasting on pentylenetetrazol-induced seizures in rats.

OBJECTIVES: Periodic fasting (PF) was suggested to display antiepileptic and neuroprotective effects, which is in stark contrast to severe fasting or starvation. However, these beneficial effects seem to depend on the type and duration of the used feeding protocol. There are discrepancies concerning both antiepileptic and neuroprotective effects of a PF-diet during repetitive seizures in different epilepsy models. This study was designed to evaluate the effects of different PF protocols on behavioural and histopathological consequences of epilepsy in adult rats. METHODS: Recurrent generalized seizures were caused by repetitive injection of pentylenetetrazol (PTZ) for a period of 4 weeks every other day. While control animals had free access to food and water, animals on a PF-diet were on intermittent fasting for 24 hours every 48 hours for 4 weeks before (T1), after (T2), or both before and after (T3) the injection of PTZ. Behavioural studies were carried out after PTZ injections and histological investigations were performed after the experiments were completed. RESULTS: Seizure assessment showed that the severity of seizures was significantly decreased in groups T1 and T3 when compared with control rats. Dark neuron densities in hippocampal CA1 and CA3 areas were decreased in PF groups, but never in the temporal cortex. The PF-diet also decreased the number of terminal deoxynucleotidyl transferase-mediated dUTP nick end-labelling-positive neurons in the hippocampus in both areas and all PF-diet protocols. DISCUSSION: These results support the idea that a PF-diet has anticonvulsive and neuroprotective effects on epileptic rats but underlines that different PF-diet protocols can have varying effects. Anticonvulsive effects were strongest when the PF-diet started before the onset of excitotoxic injuries, the number of dark neurons was decreased and apoptosis was prevented by all PF-diet protocols investigated in this work. Further evaluation of PF-diet protocols for possible clinical anticonvulsant and neuroprotective effects is suggested.

Δ9-Tetrahydrocannabivarin suppresses in vitro epileptiform and in vivo seizure activity in adult rats.

PURPOSE: We assessed the anticonvulsant potential of the phytocannabinoid Δ9-tetrahydrocannabivarin (Δ9-THCV) by investigating its effects in an in vitro piriform cortex (PC) brain slice model of epileptiform activity, on cannabinoid CB1 receptor radioligand-binding assays and in a generalized seizure model in rats. METHODS: Δ9-THCV was applied before (10 µm Δ9-THCV) or during (10-50 µm Δ9-THCV) epileptiform activity induced by Mg²(+) -free extracellular media in adult rat PC slices and measured using multielectrode array (MEA) extracellular electrophysiologic techniques. The actions of Δ9-THCV on CB1 receptors were examined using [³H]SR141716A competition binding and [³5S]GTPγS assays in rat cortical membranes. Effects of Δ9-HCV (0.025-2.5 mg/kg) on pentylenetetrazole (PTZ)-induced seizures in adult rats were also assessed. RESULTS: After induction of stable spontaneous epileptiform activity, acute Δ9 -THCV application (≥ 20 µm) significantly reduced burst complex incidence and the amplitude and frequency of paroxysmal depolarizing shifts (PDSs). Furthermore, slices pretreated with 10 µm Δ9-THCV prior to induction of epileptiform activity exhibited significantly reduced burst complex incidence and PDS peak amplitude. In radioligand-binding experiments, Δ9-THCV acted as a CB1 receptor ligand, displacing 0.5 nm [³H]SR141716A with a Ki∼290 nm, but exerted no agonist stimulation of [³5S]GTPγS binding. In PTZ-induced seizures in vivo, 0.25 mg/kg Δ9-THCV significantly reduced seizure incidence. DISCUSSION: These data demonstrate that Δ9-THCV exerts antiepileptiform and anticonvulsant properties, actions that are consistent with a CB1 receptor-mediated mechanism and suggest possible therapeutic application in the treatment of pathophysiologic hyperexcitability states.

Assessment of regional differences in tariquidar-induced P-glycoprotein modulation at the human blood-brain barrier.

We attempted to assess regional differences in cerebral P-glycoprotein (P-gp) function by performing paired positron emission tomography (PET) scans with the P-gp substrate (R)-[(11)C]verapamil in five healthy subjects before and after i.v. infusion of tariquidar (2 mg/kg). Comparison of tariquidar-induced changes in distribution volumes (DVs) in 42 brain regions of interest (ROIs) failed to detect significant differences among brain ROIs. Statistical parametric mapping analysis of parametric DV images visualized symmetrical bilateral clusters with moderately higher DV increases in response to tariquidar administration in cerebellum, parahippocampal gyrus, olfactory gyrus, and middle temporal lobe and cortex, which might reflect moderately decreased P-gp function and expression.

Calorie-restricted ketogenic diet increases thresholds to all patterns of pentylenetetrazol-induced seizures: critical importance of electroclinical assessment.

PURPOSE: Thresholds to pentylenetetrazol (PTZ) seizures were usually based only on clinical symptoms. Our purpose was to use electroclinical patterns to assess the efficacy of a ketogenic and/or calorie-restricted diet on PTZ-induced seizures. METHODS: Forty 50-day-old rats were divided in four weight-matched groups and fed controlled diets: normocalorie carbohydrate (NC), hypocalorie carbohydrate (HC), normocalorie ketogenic (NK), and hypocalorie ketogenic (HK). After 21 days, blood glucose and beta-hydroxybutyrate levels were determined and seizures were induced by continuous infusion of PTZ. The clinical and EEG thresholds to each seizure pattern were compared between the different groups. RESULTS: The electroclinical course of PTZ-induced seizures was similar in all groups. The HK group exhibited higher thresholds than the other ones for most clinical features: absence (p = 0.003), first overt myoclonia (p = 0.028), clonic seizure (p = 0.006), and for EEG features: first spike (p = 0.036), first spike-and-wave discharge (p = 0.014), subcontinuous spike-and-wave discharges (p = 0.005). NK, HC, and NC groups were not significantly different from each other. Blood glucose and beta-hydroxybutyrate levels were not correlated with electroclinical seizure thresholds. After the clonic seizure, despite stopping PTZ infusion, a tonic seizure occurred in some animals, without significant difference regarding the diet. CONCLUSION: This approach permitted a precise study of the electroclinical course of PTZ-induced seizures. In addition to the usually studied first overt myoclonia, we clearly demonstrated the efficiency of a calorie restricted KD in elevating thresholds to most electroclinical seizure patterns. We confirmed the lack of efficiency of the KD to reduce seizure severity once the seizure has started.

The use of radiotelemetry to evaluate electrographic seizures in rats with kainate-induced epilepsy.

Temporal lobe epilepsy in humans is a chronic condition with a highly variable temporal evolution. Animal models of this disorder have been developed to recapitulate many of the characteristics seen in humans with temporal lobe epilepsy. These animal models generate chronic spontaneous electrographic and motor seizures with a progressive increase in frequency over many months. In order to understand the underlying cellular and molecular mechanisms driving epileptogenesis, a practical means for accurately assessing seizure progression over this extended time period must be devised. In this report, we describe the use of a three-channel radiotelemetry system to record spontaneous electrographic interictal "spikes" and seizure activity from the cortical surface and the two hippocampi. This approach has allowed continuous recording before, during, and several months after kainate-induced status epilepticus. The important advantages of this approach are the potential for long-term continuous electrographic recording with comparatively unrestricted behavior; the disadvantages include increased cost, surgical difficulty and lower frequency-response in the recordings.

Assessment of inhibition and epileptiform activity in the septal dentate gyrus of freely behaving rats during the first week after kainate treatment.

Mossy fiber reorganization has been hypothesized to restore inhibition months after kainate-induced status epilepticus. The time course of recovery of inhibition after kainate treatment, however, is not well established. We tested the hypothesis that if inhibition is decreased after kainate treatment, it is restored within the first week when little or no mossy fiber reorganization has occurred. Chronic in vivo recordings of the septal dentate gyrus were performed in rats before and 1, 4, and 7-8 d after kainate (multiple injections of 5 mg/kg, i.p.; n = 17) or saline (n = 11) treatment. Single and paired-pulse stimuli were used to assess synaptic inhibition. The first day after kainate treatment, only a fraction of rats showed multiple population spikes (35%), prolonged field postsynaptic potentials (76%), and loss of paired-pulse inhibition (29%) to perforant path stimulation. Thus, inhibition was reduced in only some of the kainate-treated rats. By 7-8 d after treatment, nearly all kainate-treated rats showed partial or full recovery in these response characteristics. Histological analysis indicated that kainate-treated rats had a significant decrease in the number of hilar neurons compared to controls, but Timm staining showed little to no mossy fiber reorganization. These results suggest that a decrease in synaptic inhibition in the septal dentate gyrus is not a prerequisite for epileptogenesis and that most of the recovery of inhibition occurs before robust Timm staining in the inner molecular layer.

A new approach for early assessment of the epileptogenic potential of quinolones.

The epileptogenic potential of pefloxacin and norfloxacin, two quinolone antibiotics, was investigated in vivo in three different animal species by measuring drug concentrations in cerebrospinal fluid (CSF), which is part of the biophase, at the onset of convulsions. Interestingly, the pefloxacin-to-norfloxacin concentration ratios in CSF were virtually constant across the species (7.0, 6.6, and 6.0 in mice, rats, and rabbits, respectively), suggesting that this approach could be used to predict the relative epileptogenic potential of quinolones in humans.

A combined cobalt and C-14 2-deoxyglucose approach to antiepileptic drug assessment.

The cobalt model of epilepsy, in combination with the C-14 2-deoxyglucose (2-DG) autoradiographic technique, was used to assess the effects of phenytoin (PHT) and ethosuximide (ESM), two antiepileptic drugs, and ketamine (KET), a drug with anticonvulsant properties, on brain activity. Nine days after the unilateral insertion of a cobalt rod into visual cortex, the nondrugged control rats showed the usual hypermetabolic regions of putative epileptogenic tissue both adjacent to the necrotic cortical cobalt rod implant zone and more distally in the connecting thalamus. PHT and ESM, given a single injections immediately before the 2-DG uptake and clearing period, diminished glucose uptake in the cobalt-induced hypermetabolic "patches" as well as in normal tissue. However, both drugs decreased 2-DG uptake more in the thalamic patches, than in the less hypermetabolic cortical patches, where the drug-induced depression in glucose metabolism was the same as for normal tissue. These findings suggest that PHT and ESM, regardless of their actions on cell receptors and membrane conductances, are ultimately of therapeutic value because more active nervous tissue (such as epileptic tissue) is more vulnerable to the depressing effects of these drugs than is less active tissue. KET, in contrast to PHT and ESM, did not depress metabolic activity throughout the brain generally and even clearly increased it in limbic system structures. Also in contrast to PHT and SEM, KET diminished activity in the cobalt-induced patches without reducing it in the normal tissue of the homotopic control regions. The more selective depressing action of KET, an N-methyl-D-aspartate (NMDA) antagonist, may be related to the role NMDA receptors play in supporting strong nervous activity. The discussion emphasizes the usefulness of a combined cobalt/2-DG approach to antiepileptic drug assessment.

Preclinical safety assessment of iomeprol for injection as contrast medium for myelography.

A series of pharmaco-toxicological investigations were carried out in animals in order to assess the neurotolerance of iomeprol, a new nonionic iodinated contrast medium. After intrathecal administration iomeprol was completely eliminated from the cerebrospinal fluid, rapidly cleared from the plasma and excreted unchanged through the kidneys. When administrated intrathecally, iomeprol did not significantly alter the behavioural functions or the physiological activities of the brain. Unlike other contrast media, iomeprol was devoid of any epileptogenic activity. The acute neurotoxicity of iomeprol was comparable with that of iopamidol, but less than that of iohexol, iotrolan and iodixanol. Iomeprol was well tolerated in both rats and dogs following weekly intrathecal administrations for four weeks of doses up to three times higher than those foreseen for clinical use. High neurotolerance in animals and favourable physico-chemical characteristics make iomeprol particularly suitable as a contrast medium for both myelography and cerebral ventriculography.