Long-term Treatment with some Methylxanthines Decreases the Susceptibility to Bicuculline- and Pentylenetetrazol-induced Seizures in Mice. Relationship to c-ios Expression and Receptor Binding

The effects of long-term oral administration of low doses of caffeine (0.3 g/l) and its metabolites theophylline, theobromine and paraxanthine (each at 0.5 g/l in drinking water) on bicuculline- and pentylenetetrazol (PTZ) -induced seizures and c-fos expression were studied in mice. In addition, adenosine and benzodiazepine receptor density was examined. The plasma levels of the methylxanthines were much higher during the active period at night than during the day. The maximal level of caffeine was 14 μM. Brain theophylline levels (8-13 nmol/g) tended to be higher and more constant than brain caffeine levels in caffeine-consuming mice. Clonic seizures induced by bicuculline (4 mg/kg i.p.) were significantly reduced in severity by 14 day caffeine treatment and mortality was also reduced. Long-term treatment with caffeine metabolites was less effective. The seizures induced by PTZ (60 mg/kg i.p.) were also significantly reduced by long-term caffeine treatment. After bicuculline or PTZ treatment, c-fos mRNA expression was weaker in the cerebral cortex in animals receiving caffeine, irrespective of whether the animals had seizures or not. No significant changes in the binding of adenosine receptor ligands or benzodiazepines were seen after long-term caffeine treatment. These results show that long-term treatment with caffeine in a dose that is commonly seen in humans decreases the seizures induced by bicuculline, and to a lesser extent, those induced by PTZ. This may be related to a decreased neuronal excitability. The effect is due to the combined effects of theophylline, to which caffeine is metabolized in brain, and of caffeine itself, but could not be ascribed to changes in A₁ and A_2A adenosine or benzodiazepine receptors.     

Comparative effects of topical perfusions of pentylenetetrazol in the mesencephalon and cerebral cortex of cats

Push-pull perfusions of pentylenetetrazol (PTZ) were carried out in the mesencephalon and cerebral cortex (orbitofrontal, motor, and suprasylvian) of “encéphale isolé” cats, while EEG recordings from motor cortices and EMG of facial muscles were obtained. There were significant differences between perfusions in the mesencephalic reticular formation (MRF) and in the cerebral cortex: (i) EEG spikes not accompanied by muscular contractions occurred during perfusion of cerebral cortex (motor cortex included), but never with perfusions in MRF. (ii) In some instances muscular tonic and clonic contractions occurred in the absence of EEG spikes when perfusing the mesencephalon, but never with cortical perfusions. (iii) Both MRF and cortical perfusions induced EEG spikes accompanied by myoclonic seizures; however, muscular seizures were practically of the same amplitude in both sides after perfusion of the MRF and were predominant in the contralateral side after cortical perfusions. In addition, significantly less perfusion time (total dose) of PTZ was needed to induce such events in the MRF than in the cerebral cortex. (iv) Generalized seizures induced by cortical perfusions showed a clear predominance of contractions in the muscles contralateral to the perfusion site, whereas perfusions in the MRF induced generalized seizures indistinguishable from those produced by i.v. administration of PTZ. Results suggest that PTZ generalized seizures, closely resembling the so called “primary generalized seizures,” result from activation of the MRF, whereas PTZ acting in the cerebral cortex produces a model of focal convulsions that may become secondarily generalized.     

一氧化氮合酶抑制剂对戊四氮诱导大鼠点燃模型及该酶阳性神经元的影响

目的：探讨一氧化氮（ＮＯ）在癫癎 发病中的作用．方法：ｉｐ ４０ｍｇ·ｋｇ－１·ｄ－１戊四氮 ３０ｍｉｎ前注射 ２５ｍｇ·ｋｇ－１的 ＮＧ－硝基－左旋－精氨酸（Ｌ－ＮＮＡ）,连续 ２２ｄ,观察两组的行为改变及点燃串,同时对 ３组动物海马,大脑皮质一氧化氮合酶（ＮＯＳ）阳性神经元的变化输入图像扫描仪,对其胞体平均灰度值进行比较。结果：Ｌ－ＮＮＡ可明显抑制戊四氮点燃模型;戊四氮点燃大鼠模型海马,大脑皮质神经元的ＮＯＳ活性显著增高．结论：ＮＯ参与了戊四氮点燃模型的形成。     

Atorvastatin Prevents Hippocampal Cell Death due to Quinolinic Acid-Induced Seizures in Mice by Increasing Akt Phosphorylation and Glutamate Uptake

Statins are cholesterol-lowering agents due to the inhibition of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase. Recent studies have shown statins possess pleiotropic effects, which appear to be independent from its cholesterol-lowering action. In this study, we investigated whether atorvastatin would have protective effects against hippocampal cell death promoted by quinolinic acid (QA)-induced seizures in mice. Mice were pretreated with Atorvastatin (1 or 10 mg/kg) or vehicle (saline, 0.9%), orally, once a day for 7 days before the intracerebroventricular (i.c.v.) QA infusion (36.8 nmol/site). Atorvastatin treatment with 1 mg/kg/day did not significantly prevent QA-induced seizures (13.34%). However, administration of atorvastatin 10 mg/kg/day prevented the clonic and/or tonic seizures induced by QA in 29.41% of the mice. Additionally, administration of atorvastatin 10 mg/kg/day significantly prevented QA-induced cell death in the hippocampus. Atorvastatin treatment promoted an increased Akt phosphorylation, which was sustained after QA infusion in both convulsed and non-convulsed mice. Moreover, atorvastatin pretreatment prevented the reduction in glutamate uptake into hippocampal slices induced by QA i.c.v. infusion. These results show that atorvastatin attenuated QA-induced hippocampal cellular death involving the Akt pathway and glutamate transport modulation. Therefore, atorvastatin treatment might be a useful strategy in the prevention of brain injury caused by the exacerbation of glutamatergic toxicity in neurological diseases such as epilepsy.     

Decreased expression of brain cAMP response element-binding protein gene following pentylenetetrazol seizure

The present study investigated whether the expression of the cAMP response element-binding protein (CREB) in the rat brain is altered following an acute self-limited seizure induced by pentylenetetrazol (PTZ). Male rats were injected intraperitoneally with a single convulsive dose (45 mg/kg) of PTZ, and the matched controls were given saline. For immunohistochemistry, animals were perfused with 4% parafomaldehyde at 24 h following PTZ seizures, and CREB immunoreactivity was examined in rat brain. For real-time RT-PCR, animals were sacrificed at 2 and 24 h and 1 week following PTZ seizures. Tissues from different rat brain regions were micropunched and subjected to real-time RT-PCR using Taqman probe. The CREB immunoreactive profiles were significantly decreased in CA3 and dentate gyrus of hippocampal formation, sensory cerebral cortex and thalamus at 24 h after PTZ seizures. Consistent with changes in CREB immunoreactivity, levels of CREB mRNA were significantly decreased in the hippocampus, cerebral cortex, amygdala and thalamus at 24 h after PTZ seizures. No significant change was found for CREB mRNA expression in these regions at 2 h or 1 week following PTZ seizures. These results show that a brief seizure caused a decline in CREB expression up to 24 h later.     

Chronic administration of atorvastatin induced anti-convulsant effects in mice: the role of nitric oxide

Atorvastatin has neuroprotective effects, and there is some evidence that nitric oxide is involved in atorvastatin effects. In this study, we evaluated whether the nitrergic system is involved in the anticonvulsant effects of chronic atorvastatin administration. Intravenous and intraperitoneal pentylenetetrazol were used to induce seizures in mice. Chronic atorvastatin treatment significantly increased the seizure threshold which is induced by both intravenous and intraperitoneal pentylenetetrazol. Intraperitoneal pentylenetetrazol also decreased the incidence of tonic seizure and death in atorvastatin-treated groups. Chronic co-administration of a non-selective nitric oxide synthase inhibitor, l-NAME, or a selective inducible nitric oxide synthase inhibitor, aminoguanidine, with atorvastatin inhibited atorvastatin-induced anticonvulsant effects in intravenous model of pentylenetetrazol. Acute injection of l-NAME or aminoguanidine inhibited the anticonvulsant effects of atorvastatin in both models of intravenous- and intraperitoneal-pentylenetetrazol-induced seizures. In conclusion, we demonstrated that nitric oxide signaling probably through inducible nitric oxide synthase could be involved in the anticonvulsant effects of atorvastatin.     

戊四氮点燃猫癫癎形成过程中局部脑血流和葡萄糖代谢的动态研究

目的研究戊四氮(PTZ)点燃猫癫核医学科形成过程中局部脑血流和葡萄糖代谢变化特征,确定癫核医学科形成相关脑区及其在癫核医学科形成过程中的作用。方法用单光子发射计算机断层显像(99mTcECDSPECT)和正电子发射断层显像(18FDGPET)观察10只PTZ点燃雄性家猫癫核医学科形成过程中,不同行为和脑电特征时期的局部脑血流和葡萄糖代谢的动态变化规律,以感兴趣区(ROI)法对各脑区的葡萄糖代谢作半定量分析,综合分析其相互关系。结果在点燃过程中,猫的部分脑区出现持续高血流灌注和高葡萄糖代谢。临床表现为发作性四肢强直以前,猫的前脑区(额区、基底结)出现高血流灌注和高葡萄糖代谢;出现全面性强直阵挛发作后,高血流灌注和高葡萄糖代谢区逐渐转移至丘脑、海马和梨状皮质。结论PTZ点燃过程中,大脑高血流灌注和高葡萄糖代谢区可能为癫核医学科形成相关脑区。随着抽搐程度的加重,高血流灌注和葡萄糖代谢区从大脑额区向后,向深部(主要集中于丘脑、海马和梨状皮质)转移。     

Nitric oxide content measured by ESR-spectroscopy in the rat brain is increased during pentylenetetrazole-induced seizures

Nitric oxide (NO) content in rat cerebral cortex was measured using Electron Spin Resonance (ESR) spectroscopy. A nearly fivefold elevation in NO content was found at the peak time of pentylenetetrazole (PTZ)-induced seizures. The administration of N-nitro-l-arginine (L-NNA), a competitive inhibitor of NO-synthase, at the dose of 250 mg/kg, completely prevented the NO increase induced by PTZ, although clonic convulsions in the animals have been observed. L-NNA (10 mg/kg) was shown to delay the onset of clonic seizures as well as to shorten the latency of the first convulsive twitch. The level of lipid peroxidation secondary products measured as the content of thiobarbituric acid reactive species (TBARS) was increased in the cerebral cortex of PTZ-treated rats. L-NNA (250 mg/kg) failed to prevent the increased TBARS level produced by PTZ. The results support the notion that NO may play a trigger role in the pathophysiology of convulsive seizures.     

阿托伐他汀对大鼠脑缺血再灌注后血脑屏障通透性的影响

目的 评估阿托伐他汀对大鼠脑缺血再灌注后血脑屏障通透性的影响。方法 采用常规尼龙线栓法制备SD大鼠脑缺血再灌注模型,并将大鼠随机分为假手术组、大脑中动脉阻断再灌注(Middle cerebral artery occlusion/reperfusion,MCAO/R)(对照)组和MCAO/R阿托伐他汀(治疗)组; 对照组和治疗组分别于脑缺血2 h再灌注24 h处死; 标准湿干法测定脑组织含水量; 实时聚合酶链反应(Real-time polymerase chain reaction,RT-PCR)检测基质金属蛋白酶-2(Matrix metalloproteinases-2,MMP-2)和基质金属蛋白酶-9(Matrix metalloproteinases-9,MMP-9)的mRNA表达水平; 应用免疫组化法测定Ⅳ型胶原蛋白(Ⅳ type collagen,CoⅣ)水平; 电镜观察显示血脑屏障超微结构的改变。结果 治疗组与对照组比较,脑组织含水量减少(P<0.01); 阿托伐他汀治疗显著降低了MMP-2和MMP-9的mRNA表达水平; 治疗组脑组织CoⅣ水平高于对照组(P<0.01); 电镜观察显示治疗组血脑屏障超微结构的改变明显好于对照组。结论 阿托伐他汀可以降低脑缺血再灌注大鼠血脑屏障的通透性,从而减轻脑水肿。     

Increased susceptibility to pentylenetetrazol following survival of cerebral malaria in mice

Malaria is considered a neglected disease and public health problem, affecting >200 million people worldwide. In the present study we used the Plasmodium berghei ANKA (PbA) model of experimental cerebral malaria (CM) in C57BL/6 mice. After rescue from CM and parasite clearance, animals were submitted to a seizure susceptibility test (45 days after infection) using a low dose of pentylenetetrazol (PTZ, 30 mg/kg) and monitored with use of behavioral and electroencephalography (EEG) methods. Mice rescued from CM presented a reduced latency to myoclonic and tonic–clonic seizures and an increased duration of tonic–clonic seizures. In addition, quantitative analysis of EEG revealed a decrease in relative power at beta frequency band in PbA‐infected animals after PTZ injection. Our results suggest that CM may lead to increased susceptibility to seizures in mice.     

Mapping of neuronal networks underlying generalized seizures induced by increasing doses of pentylenetetrazol in the immature and adult rat: a c‐Fos immunohistochemical study

Previous studies from our group have shown that pentylenetetrazol (PTZ)-induced status epilepticus (SE) leads to age-dependent acute and long-term metabolic and circulatory changes in immature rats. In order to define the neural substrates involved in PTZ seizures according to age, the purpose of the present study was to map the areas of cellular activation during seizures of increasing severity in 10-day-old (P10), 21-day-old (P21) and adult rats. Seizures were induced by repetitive injections of subconvulsive doses of PTZ. The total dose received by the animals ranged from 4 to 125 mg/kg. These doses induced a variety of seizure profiles including absence-like, clonic seizures and SE. The cellular activation was measured as the density of c-Fos immunoreactive cells in animals at 2 h after the onset of the seizures. In P10 rats receiving a behaviourally non-active dose of PTZ, c-Fos immunoreactivity appeared only in the amygdala. The dose of 40 mg/kg that induced absence-like seizures led to a weak c-Fos expression in the medial thalamus, some cortical areas and globus pallidus. Clonic seizures reinforced labelling in the previous areas and induced a spread of c-Fos immunoreactivity to other cortical areas, thalamus, hypothalamus and some brainstem nuclei. At that age, only SE led to a widespread and stronger expression of c-Fos which was, however, totally lacking in the midbrain, and remained incomplete in the brainstem and forebrain limbic system, including the hippocampus. In P21 and adult rats, the inactive dose of PTZ induced c-Fos immunoreactivity in thalamus and hypothalamus. With absence-like seizures, c-Fos labelling spread to the cerebral cortex, amygdala, septum and some brainstem regions. With clonic seizures, immunoreactivity was reinforced in all areas already activated by absence-like seizures, and appeared in the striatum, accumbens, brainstem and hippocampus, except in CA1. After SE, c-Fos was strongly expressed in all brain areas. The intensity of c-Fos labelling was higher in most regions of P21 compared to adult rats. These data are in agreement with the immaturity of cellular and synaptic connectivity in P10 rats, the known greater sensitivity of rats to various kinds of seizures during the third week of life and the nature of the neural substrates involved in PTZ seizures.     

Traxoprodil decreases pentylenetetrazol-induced seizures

Polyamines, including spermidine, facilitate seizures by positively modulating N-methyl-d-aspartate receptors (NMDAr). Although NMDAr antagonists decrease seizures, it remains to be determined whether traxoprodil, a selective antagonist at the NR2B subunit of the NMDAr, decreases seizures and whether spermidine facilitates pentylenetetrazol (PTZ)-induced seizures. Adult male Wistar rats were injected in the lateral ventricle with 0.9% NaCl (1μl, i.c.v.), spermidine (0.02, 0.2 or 2nmol/site, i.c.v.) or traxoprodil (0.2, 2 or 20nmol, i.c.v.) and with PTZ (35 or 70mg/kg, i.p.). The effect of orally administered traxoprodil (60mg/kg, p.o.) on seizures was also investigated. Latencies to clonic and generalized seizures, as well the total time spent in seizures were recorded by behavioral and electrographic methods (EEG). Spermidine (2nmol/site; i.c.v.) facilitated the seizures induced by a sub-threshold dose of PTZ (35mg/kg; i.p.), but did not alter seizure activity induced by a convulsant dose of PTZ (70mg/kg; i.p.). Traxoprodil (20nmol i.c.v.) increased the latency to generalized tonic-clonic seizures induced by PTZ (70mg/kg; i.p.). Traxoprodil (60mg/kg, p.o.) increased the latency to clonic and generalized seizures, and decreased the total time spent in seizures. These results support the role for the NR2B subunit in PTZ-induced seizures.     

Neurosteroid Withdrawal Model of Perimenstrual Catamenial Epilepsy

PURPOSE: Perimenstrual catamenial epilepsy, the increase in seizure frequency that some women with epilepsy experience near the time of menstruation, may in part be related to withdrawal of the progesterone metabolite allopregnanolone, an endogenous anticonvulsant neurosteroid that is a potent positive allosteric gamma-aminobutyric acidA (GABA(A)) receptor modulator. The objective of this study was to develop an animal model of perimenstrual catamenial epilepsy for use in evaluating drug-treatment strategies. METHODS: A state of prolonged high serum progesterone (pseudopregnancy) was induced in 26-day-old female rats by sequential injection of pregnant mares' serum gonadotropin and human chorionic gonadotropin. Neurosteroid withdrawal was induced by treatment with finasteride (100 mg/kg, i.p.), a 5alpha-reductase inhibitor that blocks the conversion of progesterone to allopregnanolone. Plasma progesterone and allopregnanolone levels were measured by gas chromatography/electron capture negative chemical ionization mass spectrometry. Seizure susceptibility was evaluated with the convulsant pentylenetetrazol (PTZ). RESULTS: Plasma allopregnanolone levels were markedly increased during pseudopregnancy (peak level, 55.1 vs. control diestrous level, 9.3 ng/mL) and were reduced by 86% 24 h after finasteride treatment (6.4 ng/mL). Progesterone levels were unaffected by finasteride. After finasteride-induced withdrawal, rats showed increased susceptibility to PTZ seizures. There was a significant increase in the number of animals exhibiting clonic seizures when challenged with subcutaneous PTZ (60 mg/kg) compared with control pseudopregnant animals not undergoing withdrawal and nonpseudopregnant diestrous females. The CD50 (50% convulsant dose) was 46 mg/kg, compared with 73 mg/kg in nonwithdrawn pseudopregnant animals and 60 mg/kg in diestrous controls. The threshold doses for induction of various seizure signs, measured by constant intravenous infusion of PTZ, were reduced by 30-35% in neurosteroid-withdrawing animals compared with control diestrous females. No change in threshold was observed in pseudopregnant rats treated from days 7 to 11 with finasteride, demonstrating that high levels of progesterone alone do not alter seizure reactivity. CONCLUSIONS: Neurosteroid withdrawal in pseudopregnant rats results in enhanced seizure susceptibility, providing an animal model of perimenstrual catamenial epilepsy that can be used for the evaluation of new therapeutic approaches.     

Pentylenetetrazol-induced status epilepticus up-regulates the expression of glucose transporter mRNAs but not proteins in the immature rat brain

Prolonged pentylenetetrazol (PTZ)-induced seizures increase cerebral energy demands in a region-specific manner. During PTZ seizures, cerebral glucose utilization increases over control levels in all brain regions at 10 days while 21-day-old rats exhibit increases, decreases or no change. To explore the effects of such acute changes in metabolic demand on the expression of glucose transporter proteins mediating glucose delivery to brain, we studied the consequences of PTZ seizures on GLUT1 and GLUT3 mRNAs and proteins between 1 and 72 h after seizure induction. At both ages, seizures induced a rapid up-regulation of GLUT1 and GLUT3 mRNAs which was prominent at 1 and 4 h, and was greater at 10 than at 21 days. By 24 h and 72 h, the levels of the mRNAs of the two transporter returned to control levels or were slightly down-regulated. The levels of GLUT1 and GLUT3 proteins were not affected by the seizures and only scattered decreases in GLUT3 protein were recorded, mainly in midbrain-brainstem areas. These data show that acute pentylenetetrazol seizures induce a rapid up-regulation of the GLUT1 and GLUT3 mRNAs, but do not result in measurable increases in protein levels, suggesting translational regulation.     

Experimental spike-and-wave discharges induced by pentylenetetrazol and tolerance to repeated injections: an electrophysiological and biochemical study

This study was designed to obtain experimental data to correlate duration of spike-and-wave (SW) paroxysms with levels of pentylenetetrazol (PTZ) in several brain regions after intraperitoneal (i.p.) administration of subconvulsive doses of PTZ in Wistar rats. The influence of subconvulsive doses of PTZ on blood-brain barrier (BBB) permeability and tolerance of PTZ to repeated injections were also studied. Intraperitoneal administration of subconvulsive doses of PTZ (25 mg/kg) in single doses resulted in SW activity which accounted for 20% of the continuous electrical brain activity recorded during the first hour after i.p. administration. Brain PTZ levels (cortex, midbrain, cerebellum) were within the range 19.2-34.9 micrograms/g. Repeated doses of PTZ showed a significant decrease in SW activity with no change in PTZ brain levels. As PTZ bioavailability was the same after either a single dose or after repeated doses, the decrease in SW activity may be due to PTZ tolerance. No alterations in the BBB were induced by PTZ subconvulsive doses. The experimental data reported in this study may be useful to quantify modifications of biochemical parameters or to evaluate antiepileptic drugs.     

The role of technical, biological and pharmacological factors in the laboratory evaluation of anticonvulsant drugs. III. Pentylenetetrazole seizure models

Although seizure models using systemic administration of the chemoconvulsant pentylenetetrazol (PTZ) for induction of generalized clonic seizures in rodents are widely employed to identify potential anticonvulsants, the important role of diverse technical, biological and pharmacological factors in interpretation of results obtained with these models is often not recognized. The aim of this study was to delineate factors other than sex, age, diet, climate, and circadian rhythms, which are generally known. For this purpose, experiments with 8 clinically established antiepileptic drugs were undertaken in the following PTZ models: (1) the threshold for different types of PTZ seizures, i.e., initial myoclonic twitch, generalized clonus with loss of righting reflexes, and tonic backward extension of forelimbs (forelimb tonus), in mice; (2) the traditional PTZ seizure test with s.c. injection of the CD97 for generalized clonic seizures in mice; and (3) the s.c. PTZ seizure test in rats. In rats, in addition to evaluating drug effects on generalized clonic seizures, a ranking system was used to determine drug effects on other seizure types. When drugs were dissolved in vehicles which themselves did not exert effects on seizure susceptibility, the most important factors which influenced drug potencies were: (1) bishaped dose-response curves, i.e., a decline in anticonvulsant dose-response at high doses of some drugs, leading to misinterpretations of drug efficacy if only a single high drug dosage is tested; (2) effects of route of PTZ administration (i.v. infusion vs. s.c. injection) on estimation of anticonvulsant potency; (3) species differences in drug metabolism; (4) differences in drug potencies calculated on the basis of administered doses compared to potency calculations based on 'active' drug concentrations in plasma; (5) qualitative and quantitative species differences in drug actions; (6) endpoints used for PTZ tests; (7) misleading predictions from PTZ seizure models. Analysis of anticonvulsant drug actions indicated that myoclonic or clonic seizures induced by i.v. or s.c. PTZ might be suitable for predicting efficacy against myoclonic petit mal seizures in humans, but certainly not to predict efficacy against absence seizures. Tonic seizures induced by PTZ were blocked by drugs, such as ethosuximide, which exert no effect on tonic seizures in humans. In order to reduce the variability among estimates of anticonvulsant activity in PTZ seizure models, the various factors delineated in this study should be rigidly controlled in experimental situations involving assay of anticonvulsant agents.     

Differential effects of NMDA antagonists microinjections into the nucleus reticularis pontis caudalis on seizures induced by pentylenetetrazol in the rat

It has been shown that NMDA antagonists block the tonic but not the clonic component of seizures when they are injected in the oral region of the rat pontine reticular formation (PRF). The participation of the caudal PRF in the effects of NMDA antagonists upon the tonic and the clonic components of generalized seizures induced by pentylenetetrazol (PTZ) is unknown. The aim of the present study was to evaluate the effects of unilateral microinjections of competitive and non-competitive NMDA antagonists, 2-amino-7-phosphonoheptanoic acid (AP-7) and dizocilpine (MK-801), respectively, into the nucleus reticularis pontis caudalis of the rat PRF upon seizures induced by PTZ (70 mg/kg i.p.). MK-801 induced a dose-related decrease both in the incidence of generalized tonic-clonic seizures (GTCS) and in the presence of spikes in the EEG. MK-801 also increased GTCS latency. On the contrary, AP-7 did not have effects on GTCS. Interestingly, it induced ipsilateral circling behavior. These results suggest that in the caudal region of the rat PRF only non-competitive NMDA antagonists should block the generation of tonic and clonic components of generalized seizures.     

Postnatal caffeine treatment affects differently two pentylenetetrazol seizure models in rats

Effects of repeated postnatal administration of caffeine (10 and 20 mg/kg s.c. daily from P7 to P11) were studied in two models of epileptic seizures characterized by spike-and-wave EEG rhythm in 18- and 25-day-old rats. Rhythmic metrazol activity (RMA, model of human absences) was induced by low dose of pentylenetetrazol (PTZ, 20 mg/kg or 40 mg/kg, i.p.) and minimal clonic seizures (model of human myoclonic seizures) by two successive doses of PTZ (20 and 40 mg/kg i.p.). Early postnatal caffeine treatment resulted in significant changes of RMA only in 18-day-old rats. Anticonvulsant effects were observed in RMA episodes elicited by the 20-mg/kg dose of PTZ in both caffeine groups whereas latency of RMA episodes induced by the 40-mg/kg dose was shortened and their duration was prolonged. No changes were found in 25-day-old animals. Incidence, EEG and motor pattern of minimal clonic seizures were not changed. Some animals in both control age groups exhibited transition to generalized tonic–clonic seizures. This type of seizures never appeared in caffeine-treated 25-day-old animals. Mixed effects of postnatal caffeine exposure were demonstrated; these predominantly anticonvulsant effects are age- and model-specific.     

Anticonvulsant,neuroprotective and behavioral effects of organic and conventional yerba mate (Ilex paraguariensis St. Hil.) on pentylenetetrazol-induced seizures in Wistar rats

Epilepsy, which is one of the most common neurological disorders, involves the occurrence of spontaneous and recurrent seizures that alter the performance of the brain and affect several sensory and behavioral functions. Oxidative damage has been associated with post-seizure neuronal injury, thereby increasing an individual's susceptibility to the occurrence of neurodegenerative disorders. The present study investigated the possible anticonvulsive and neuroprotective effects of organic and conventional yerba mate (Ilex paraguariensis), a plant rich in polyphenols, on pentylenetetrazol (PTZ)-induced seizures in Wistar rats. The behavioral and polyphenolic profiles of the yerba mate samples were also evaluated. Infusions of yerba mate (50 mg/kg) or distilled water were given to rats for fifteen days by oral gavage. On the 15th day the animals were subjected to open field test, and exploratory behavior was assessed. Subsequently, 60 mg/kg PTZ (i.p.) was administered, and animals were observed for the appearance of convulsions for 30 min. Latency for the first seizure, tonic–clonic and generalized seizures time, frequency of seizures and mortality induced by PTZ were recorded. The animals were then sacrificed, and the cerebellum, cerebral cortex and hippocampus were quickly removed and frozen to study the neuroprotective effects of yerba mate. The oxidative damage in lipids and proteins, nitric oxide levels, the activities of the antioxidant enzymes superoxide dismutase (Sod) and catalase (Cat) and non-enzymatic cellular defense (sulfhydryl protein) were quantified in all the tissues. The results showed that organic and conventional yerba mate infusions were able to reduce the frequency of seizures when compared to the PTZ group. Besides, organic yerba mate infusion decreases the tonic–clonic seizures time in relation to the PTZ group. It was also shown that organic and conventional yerba mate infusions reduced the oxidative damage in lipids and proteins and nitric oxide levels and prevented the decrease in Sod and Cat activities and sulfhydryl protein content when compared to the PTZ group in all the CNS tissues assayed. Organic and conventional yerba mate commercial samples did not change the behavior (locomotion, exploration or anxiety) of the treated animals. In both organic and conventional infusions, the presence of the polyphenols rutin, chlorogenic acid and their acyl derivatives were detected, which could be associated with the biological effects observed. These data indicate that yerba mate may provide new perspectives for the development of therapeutic approaches with natural compounds in the pharmaceutical area, both to reduce the convulsions’ frequency and to minimize the neuronal damage associated with recurrent seizures.     

Ralitoline: a reevaluation of anticonvulsant profile and determination of "active" plasma concentrations in comparison with prototype antiepileptic drugs in mice

Ralitoline (RLT) is a new thiazolidinone derivative with potent anticonvulsant activity in different seizure models. During Phase I studies, RLT was well tolerated in human volunteers and showed linear pharmacokinetics in the dose range tested (up to 150 mg). Since RLT will soon be entering clinical Phase II studies, we were interested in obtaining predictive data for effective plasma concentrations in patients. For this purpose, the anticonvulsant potency of RLT was determined in four seizure models in mice, and plasma levels were measured at time of peak drug effect. The four models were the threshold for maximal (tonic extension) electroshock seizures (MES), the threshold for clonic seizures determined by i.v. infusion of pentylenetetrazol (PTZ), the traditional MES test with supramaximal (50 mA) stimulation, and generalized clonic seizures induced by s.c. administration of PTZ. Furthermore, median minimal "neurotoxic" doses (TD50s) were determined by the rotorod and chimney test for calculation of protective indices. All data obtained for RLT were compared with data obtained with standard antiepileptic drugs: phenobarbital, phenytoin, valproate, and diazepam. The onset of anticonvulsant action after i.p. injection of RLT was very rapid, and the peak drug effect was already obtained after 2 min. In the MES models, RLT was the most potent compound. "Active" plasma levels ranged from approximately 300 ng/ml in the MES threshold test to approximately 1,300 ng/ml in the MES test. RLT was also capable of increasing the PTZ threshold, whereas, possibly because of its short duration of action in mice, it was not very active in the s.c. PTZ seizure test.(ABSTRACT TRUNCATED AT 250 WORDS)