Nitric oxide, epileptic seizures, and action of antiepileptic drugs

Nitric oxide (NO) plays a variety of physiological and pathological roles in mammalian cells. In the central nervous system NO may behave as a second messenger, neuromodulator, and neurotransmitter, which may suggest an essential role of this gaseous molecule in epilepsy and epileptogenesis. The aim of this review is to survey the current literature in terms of experimental and clinical evidence of anti- or proconvulsive properties of NO and its implications in the anticonvulsive action of antiepileptic drugs. Up-to-date multiple NO synthase (NOS) inhibitors and donors of NO were used in a plethora of seizure models (e.g. electrically and pharmacologically-evoked convulsions, amygdala-kindled seizures). Reported results vary depending on the seizure model, kind and doses of pharmacological tools used in experiments, and route of drug administration. The most thoroughly tested NOS inhibitor was 7- nitroindazole (7-NI), which presented anticonvulsive properties in most known models of seizures. The clear-cut proconvulsant action of 7-NI was observed only in kainate-, nicotine-, and soman-induced convulsions in rodents. This NOS inhibitor enhanced the anticonvulsant action of almost all available classic and second-generation antiepileptic drugs except tiagabine, felbamate, and topiramate. The effect of NG-nitro-L-arginine methyl ester was not so unambiguous. In pentylenetetrazole, pictotoxin, and N-methyl-Daspartate seizure models the inhibitor exhibited dose-dependent bidirectional action. NG-nitro-L-arginine methyl ester potentiated the efficacy of diazepam and clonazepam, diminished that of valproate and phenobarbital, but did not affect the anticonvulsant action of phenytoin and ethosuximide. On the other hand, NG-nitro-L-arginine, was anticonvulsant in nicotine-, glutamate-, and hyperbaric O2- evoked seizures, and proconvulsant in pilocarpine-, kainate-, bicuculline-, aminophylline-, and 4-aminopyridine-induced convulsions. NG-nitro-L-arginine remained without effect on the anticonvulsant action of both classic (valproate, phenobarbital, diazepam) and new generation (oxcarbazepine, felbamate, and ethosuximide) antiepileptic drugs. The action of ethosuximide was even impaired. Summing up, in the present state of knowledge the only reasonable conclusion is that NO behaves as a neuromodulator with dual - proconvulsive or anticonvulsive - action.     

阿司匹林干预癫痫大鼠的自发性发作药理机制研究

目的研究阿司匹林对大鼠癫痫发作的影响,并从炎症反应、细胞凋亡两个方面探索其作用机制。方法建立氯化锂-匹鲁卡品(LICL-PILO)大鼠癫痫模型将大鼠随机分为正常对照组(N)、模型组(S)和阿司匹林干预组(A组)分别于建模后0、3、24h给予阿司匹林(20mg·kg~(-1)·d~(-1)),记为A-0组、A-3组、A-24组。建模后3d,利用免疫荧光检测海马内多种炎症细胞因子及凋亡因子的含量;利用Western blot检测NF-κBp65蛋白和凋亡相关蛋白含量;建模后10d,录像观察大鼠癫痫发作(≥4级)的时间、频率;连续观察10d后,使用Neu N染色检测海马内神经元的丢失情况。结果 (1)建模后3d,与S组相比,N组、A-0组及A-24组的NF-κB和Bax显著降低(P<0.05);A-3组、A-24组的Bcl-2和Bcl-2/Bax则显著升高(P<0.05);(2)与S组和A-0组相比,N组、A-3组和A-24组Bcl-2m RNA和Bcl-2/Bax显著升高(P<0.05);而IL-1β、TNF-a、NF-κB和Bax m RNA则显著降低(P<0.05);(3)各阿司匹林干预组癫痫发作的时间和频率均显著低于S组(P<0.01);但各干预组间差异无统计学意义(P>0.05);(4)建模后20d,在海马内CA1、CA3和Hilus区,N组和各阿司匹林干预组(A-0组、A-3组、A-24组)神经元数目均显著高于S组(P<0.05)。结论阿司匹林通过抑制炎症反应和细胞凋亡,降低癫痫后神经元的丢失,进而降低癫痫的发作时间及频率。     

Hyperhomocysteinemia in epileptic patients on new antiepileptic drugs

Purpose : Older enzyme‐inducing antiepileptic drugs (AEDs) may induce supraphysiologic plasma concentrations of total (t) homocysteine (Hcy). The aim of the present study was to investigate the effect of new AEDs on plasma tHcy levels. Methods : Patients 18–50 years of age, on AEDs monotherapy, with no other known cause of hyper‐tHcy were enrolled. Plasma tHcy, folate, vitamin B₁₂, and AEDs levels were determined by standard high‐performance liquid chromatography (HPLC) methods. Methylenetetrahydrofolate‐reductase (MTHFR) polymorphisms were checked using Puregene genomic DNA purification system (Gentra, Celbio, Italy). A group of healthy volunteers matched for age and sex was taken as control. Results : Two hundred fifty‐nine patients (151 on newer and 108 on older AEDs) and 231 controls were enrolled. Plasma tHcy levels were significantly higher [mean values, standard error (SE) 16.8, 0.4 vs. 9.1, 0.2 μm ; physiologic range 5–13 μm ] and folate lower (6.3, 0.1 vs. 9.3, 0.1 nm ; normal > 6.8 nm ) in patients compared to controls. Patients treated with oxcarbazepine, topiramate, carbamazepine, and phenobarbital exhibited mean plasma tHcy levels above the physiologic range [mean values (SE) 16 (0.8), 19.1 (0.8), 20.5 (1.0), and 18.5 (1.5) μm , respectively]. Conversely, normal tHcy concentrations were observed in the lamotrigine and levetiracetam groups [both 11.1 (0.5) μm ]. Discussion : Oxcarbazepine and topiramate might cause hyper‐tHcy, most likely because of the capacity of these agents to induce the hepatic enzymes. Because literature data suggest that hyper‐tHcy may contribute to the development of cerebrovascular diseases and brain atrophy, a supplement of folate can be considered in these patients to normalize plasma tHcy.     

Long-lasting antiepileptic effects of levetiracetam against epileptic seizures in the spontaneously epileptic rat (SER): differentiation of levetiracetam from conventional antiepileptic drugs

PURPOSE: Some evidence suggests that levetiracetam (LEV) possesses antiepileptogenic characteristics. The purpose of this study was to investigate the time course of seizure protection by LEV compared with that of phenytoin (PHT), phenobarbital (PB), valproate (VPA), and carbamazepine (CBZ) in the spontaneously epileptic rat (SER). The SER is a double mutant (tm/tm, zi/zi) showing both tonic convulsions and absence-like seizures. METHODS: The effect of single (40, 80, and 160 mg/kg, i.p.) and 5-day (80 mg/kg/day, i.p.) administration of LEV on tonic convulsions and absence-like seizures in SERs were studied. Tonic convulsions induced by blowing air onto the animal's head at 5-min intervals for 30 min and spontaneous absence-like seizures characterized by 5- to 7-Hz spike-wave-like complexes in the cortical and hippocampal EEG were recorded for 30 min. In the single-administration study, observations for seizure activity were performed once before and 3 times (45, 75, and 135 min) after drug administration. In the 5-day administration study, seizure observation was performed 4 times for 30 min (once before and 3 times after drug administration) during the 5-day drug-administration period, and continued once a day until 8 days after the final administration. The antiepileptic effects of 5-day administration of conventional AEDs (PHT, PB, VPA, and CBZ) were examined by using similar methods. RESULTS: Tonic convulsions and absence-like seizures were inhibited by a single administration of LEV at 80 and 160 mg/kg, i.p., but not significantly at 40 mg/kg, i.p. When LEV was repeatedly administered at 80 mg/kg/day, i.p., for 5 days to SERs, the inhibitory effects on seizures increased with administration time. The number of tonic convulsions and absence-like seizures were significantly reduced to 39.1% and 38.4% compared with previous values, respectively, after 5-day LEV administration. Furthermore, significant inhibition of tonic convulsions was detected 相似文献   

Reduction of antiepileptic drug dosage for monitoring epileptic seizures

Eleven epileptic patients, candidates for surgical treatment, were examined in order to localize epileptic foci. The daily doses of antiepileptic drugs (AEDs) were reduced by fifty per cent or less, and the reduced dosages were maintained until a seizure had occurred. The reduction resulted in seizures within five days among all patients, and the number of seizures increased significantly in comparison with the five-day period before AED reduction. The seizures so provoked were typical for each patient, as confirmed by clinical observation and video-EEG telemetry. No status epilepticus or withdrawal psychosis occurred. The AED concentrations at the time of the seizures were generally within the reference values.     

Effects of antiepileptic drugs on evoked potentials in epileptic children

To evaluate the visual and auditory function in children and adolescents who are undergoing monotherapy with sodium valproate, carbamazepine, and phenobarbital visual-evoked potentials and brainstem auditory-evoked potentials were measured in 58 epileptic patients (30 males and 28 females), ages 13.7 ± 6.9 years. Fifty healthy sex- and age-matched children served as controls. The measurements were performed before the beginning of therapy and after 12 months. Before the beginning of therapy, there were no significant differences in visual- and auditory-evoked potentials between the control group and the three groups of epileptic children. After 12 months of therapy, patients treated with carbamazepine demonstrated a significant (P < 0.001) increase of P100 latencies when compared with baseline data and control values; moreover, these patients exhibited a significant increase of peak latencies of waves I-III-V and interpeak interval I-V at auditory second evaluation. The patients treated with sodium valproate manifested a significant (P < 0.05) increase in VEP P100 latencies. On the contrary, children receiving phenobarbital did not manifest any significant abnormality at visual- and auditory-evoked potentials measurements. Our study demonstrates that for patients treated with carbamazepine and sodium valproate, an electrophysiologic dysfunction of visual and auditory sensory pathways can be present after 12 months of treatment.     

Homocysteine levels in epileptic children receiving antiepileptic drugs

The aim of this study is to investigate the homocysteine, folic acid, and vitamin B(12) levels in epileptic children receiving antiepileptic drugs. A total of 25 children with idiopathic epilepsy (8 valproate, 11 carbamazepine, and 6 oxcarbazepine) and 10 healthy children were included in the study. The mean homocysteine, folic acid, and vitamin B(12) levels in the study group were 7.57 +/- 3.78 micromol/L (normal = 5-15 micromol/L), 10.19 +/- 4.05 ng/mL (normal = 3.0-17 ng/mL), and 428.20 +/- 256.12 pg/mL (normal = 193-983 pg/mL), respectively. The differences between the mean plasma homocysteine, folic acid, and vitamin B(12) levels of the study and control groups were not significant (P = .522; P = .855; P = .798, respectively). However, plasma homocysteine levels were higher than the normal cutoff point accepted for childhood in 4 (16%) of the study patients. Out of these 4 children, 3 were from the carbamazepine group and 1 was from the valproate group. Although the number of the study patients is limited, the authors recommend assessment of plasma homocysteine, serum vitamin B(12), and folic acid levels in children receiving enzyme-inducing antiepileptic drugs.     

Screening and characterization of antiepileptic drugs with rapidly recurring hippocampal seizures in rats

A method to efficiently screen antiepileptic drugs (AED) for their actions against complex partial and secondarily generalized seizures is presented. The procedure relies on rapidly recurring hippocampal seizures (RRHS) in rats which are first used to bring epileptic responses to a stable, fully kindled state and then to test 3 parameters--behavioral seizures, electrographic seizures, and afterdischarge thresholds--before and after drug administration. With the methods described, the effects of a given drug treatment can be thoroughly determined in a single study period. Quantitative determinations of dose-response, time-action and relative potency characteristics are readily ascertained. A battery of known AED, encompassing those in common clinical use, was studied with this system. Kindled motor seizures (classes 4 and 5) were more readily suppressed than limbic behavioral seizures (classes 1-3). Electrographic seizures were usually, but not always, shortened concurrently with suppression of behavioral seizures. Under the conditions of this study, afterdischarge thresholds were not elevated, indicating that a critical role of AED is to counteract seizure spread and prolongation. The overall behavior of the RRHS test system with AED was identical to that with traditional amygdala kindled seizures and results were in good agreement with the clinical responsiveness of the kinds of seizures that these experimental systems model. The features of RRHS make it a useful system for screening new agents for antiepileptic effects, even in circumstances where little or no information about the drug under study is available.     

Effect of drugs on electroclinical types of epileptic seizures in Lennox-Gastaut syndrome]

The therapeutics results with the use of different drugs (diazepam, nitrazepam, clonazepam, diphenylhydantoin, barbiturates--phenobarbital and primidone--, sodium dipropylacetate and ACTH) in twenty-nine patients with Lennox--Gastaut syndrome are carefully analysed. The effect of each drug on seizures (tonic, tonic-clonic, clonic, myoclonic or myoclonic-atonic, atonic and atypical absences) during the first month of each treatment is discussed. The "specific" use of each drug on the various forms of epileptic seizures is determined and the possibility of crisis control with reduction of the drugs dosage is verified.     

Effects of A1 receptor agonist/antagonist on spontaneous seizures in pilocarpine-induced epileptic rats

Adenosine is an endogenous anticonvulsant that activates pre- and postsynaptic adenosine A₁ receptors. A₁ receptor agonists increase the latency for the development of seizures and status epilepticus following pilocarpine administration. Although hippocampal adenosine is increased in the chronic phase of the pilocarpine model, it is not known whether the modulation of A₁ receptors may influence the frequency of spontaneous recurrent seizures (SRS). Here, we tested the hypothesis that the A1 receptor agonist RPia ([R]-N-phenylisopropyladenosine) and the A1 antagonist DPCPX (8-Cyclopentyl-1,3-dipropylxanthine) administered to chronic pilocarpine epileptic rats would respectively decrease and increase the frequency of SRS and hippocampal excitability. Four months after Pilo-induced SE, chronic epileptic rats were video-monitored for the recording of SRS before (basal) and after a 2-week treatment with RPia (25 μg/kg) or DPCPX (50 μg/kg). Following sacrifice, brain slices were studied with electrophysiology. We found that rats given RPia had a 93% nonsignificant reduction in the frequency of seizures compared with their own pretreatment baseline. In contrast, the administration of DPCPX resulted in an 87% significant increase in seizure rate. Nontreated epileptic rats had a similar frequency of seizures along the study. Corroborating our behavioral data, in vitro recordings showed that slices from animals previously given DPCPX had a shorter latency to develop epileptiform activity, longer and higher DC shifts, and higher spike amplitude compared with slices from nontreated Pilo controls. In contrast, smaller spike amplitude was recorded in slices from animals given RPia. In summary, the administration of A1 agonists reduced hippocampal excitability but not the frequency of spontaneous recurrent seizures in chronic epileptic rats, whereas A1 receptor antagonists increased both.     

Retrospective analysis of the effectiveness of first-line antiepileptic drugs for generalized onset and unclassified epileptic seizures in Chinese children

Background and purpose  

Based on the time until treatment failure, we retrospectively analyzed 389 children to compare the long-term effectiveness of first-line antiepileptic drugs (AEDs) in children with generalized onset or unclassified epileptic seizures.     

癫痫持续发作时间与大鼠海马苔藓纤维发芽程度及自发性痫性发作的关系

目的探讨癫痫持续状态(SE)发作时间与致痫大鼠海马苔藓纤维发芽(MFS)程度及自发性痫性发作的关系。方法 104只雄性成年SD大鼠,随机分为对照组和3个SE实验组,建立氯化锂-重复低剂量匹罗卡品致痫大鼠模型;诱发SE30min(A组)、60min(B组)、90min(C组)后注射水合氯醛终止发作。各组大鼠自SE终止发作后于相同实验条件下普通饲养45d,观察大鼠行为及脑电图(EEG)的变化,记录自发性痫性发作的发生率。通过苏木精-伊红染色、Nissl染色和Timm硫化银组织化学染色方法观察各实验组海马MFS情况。结果氯化锂-重复低剂量匹罗卡品成功诱导大鼠SE的发生,发作程度均达Ⅳ级以上,EEG类似人类颞叶癫痫。80%的大鼠癫痫持续状态均发展为自发痫性发作,与SE时间无关。与对照组相比,实验A、B、C三组双侧海马CA3区均表现MFS(P0.05)。实验B组与A、C组相比,CA3区MFS明显增加(P0.05)。结论氯化锂-重复低剂量匹罗卡品可诱导SE,癫痫持续发作60min后终止的大鼠海马CA3区MFS明显增加,SE发作时间与海马MFS程度并不一定呈正相关。     

7-nitroindazole differentially affects the anticonvulsant activity of antiepileptic drugs against amygdala-kindled seizures in rats

PURPOSE: The objective of this study was to evaluate the interaction of the preferential brain nitric oxide synthase (NOS) inhibitor, 7-nitroindazole (7-NI), with conventional antiepileptic drugs (AEDs) against amygdala-kindled seizures in rats. METHODS: Experiments were performed on fully kindled rats. Adverse effects were evaluated with the rotorod test, which assesses motor coordination, and the passive-avoidance task, which assesses memory. Plasma levels of AEDs were measured by immunofluorescence. RESULTS: 7-NI (up to 100 mg/kg) failed to modify seizure parameters. However, it reduced the severity and duration of kindled seizures when coadministered with otherwise ineffective doses of carbamazepine (CBZ) (10-20 mg/kg) or phenobarbital (PB) (20 mg/kg). Combinations of 7-NI with valproate (VPA), diphenylhydantoin (DPH), or clonazepam (CLO) were not protective. L-Arginine (500 mg/kg) did not reverse the seizure-suppressing interactions between 7-NI and the conventional AEDs. The combinations of 7-NI and CBZ or PB did not impair performance in the rotorod test. Coadministration of 7-NI with CBZ did not affect long-term memory, and 7-NI given with PB didn't affect the mnemonic effect of PB. Finally, 7-NI did not affect the free plasma levels of CBZ or PB. CONCLUSIONS: Pharmacokinetic interactions do not seem to account for the anticonvulsant effects of 7-NI combined with CBZ or PB. Central nitric oxide (NO) is possibly not involved in the synergism between 7-NI and these AEDs.     

Cognitive functions, epileptic syndromes and antiepileptic drugs.

Cognitive function of patients on monotherapy specific for their epileptic syndrome has been studied infrequently. We evaluated 7 patients with symptomatic localised epilepsies (SEL) on phenytoin aged 30 +/- 12 (mean +/- standard deviation) years, 8 with idiopathic generalised epilepsies on sodium valproate aged 18 +/- 4 years, 16 with SEL on carbamazepine aged 28 +/- 11 years, and 35 healthy controls aged 27 +/- 11 years. All subjects were of normal intelligence, educated appropriately to age, and led productive lives in the community. Two of the patients on carbamazepine and one on valproate had less than five partial, absence or myoclonic seizures monthly, the remaining were controlled. Carbamazepine serum concentrations were 12 +/- 5 micrograms/ml, phenytoin were 23 +/- 7, and valproate were 62 +/- 23 (mean +/- sd). Tests included immediate recall and recognition for pictures, Stroop test, delayed recall and recognition of pictures. Patients on phenytoin and valproate performed significantly worse than controls on immediate recall, and patients on carbamazepine performed significantly worse than controls in Stroop test (p < 0.01). The results indicate relatively minor effects of the epileptic syndromes and of phenytoin, carbamazepine and valproate on cognition of patients with controlled epilepsy leading productive lives in the community. We conclude that the cognitive deficit found in chronic epileptic patients on poly-therapeutic drug regimen must be multifactorial, and that future studies need to control for all possible variables in order to achieve meaningful results.