Induced Tonic Seizures Research Articles

Antiepileptic Activity of Indian Filbert Fruit Extract in Experimental Animal Models

Aim: To screen the antiepileptic activity of ethanolic fruit extract of Indian filbert.
 Methodology: The cleaned, dried and powdered fruits of Indian filbert were subjected to extraction.Preliminary Phytochemical studies were carried out for the presence secondary metabolites.Acute toxicity and anticonvulsant effect on maximal electroshock induced seizures and metrazol (pentylenetetrazole) induced seizures carried out in experimental animals.
 Results: Preliminary phytochemical studies showed the presence of steroids, triterpenoids, flavonoids, carbohydrates. Acute toxicity of ethanolic extract of fruits were found to be safe up to 2000 mg/kg body weight Ethanolic extract of Indian (100,200 and 400 mg/kg) significantly reduced the duration of seizures induced by maximal electroshock (MES) as well as protected animals from metrazol induced tonic seizures and the results were found to be significant (P=0.05) when compared to control
 Conclusions: The presence of triterpenoids, steroids and flavonoid might be responsible for the antiepileptic activity of the fruit extract of Indian filbert.

Evaluation of Anticonvulsant Activities of Eryngium caucasicum with Maximal Electroshock and Kindling Model of Seizure in Mice

Background: Eryngium species is reported to have variety of activities and has been used in traditional medicine for many years. In spite of the CNS and antioxidant activity of E. caucasicum, nothing is known about its anticonvulsant activity. Objectives: In this study, we aimed to evaluate the anticonvulsant activities of methanolic extracts of E. caucasicum on maximal electroshock (MES) and pentylenetetrazole (PTZ)-induced seizures in mice. Materials and Methods: The anticonvulsant activities of methanolic and polyphenolic extracts of E. caucasicum inflorescence at doses of 250, 500 and 1000 mg kg-1 were determined by Pentylenetetrazole (PTZ) and maximal electroshock (MES)-induced convulsions in mice. Results: Normal saline treated mice showed tonic hind limb extension for duration of 12.35 ± 0.46 seconds in the MES model. Methanolic extract at 250 and 500 mg kg-1 and polyphenolic extract at 200 mg kg-1 induced maximum protection against seizures, and polyphenolic extract at 200 mg kg-1 had 66.6% protection. PTZ (100 mg kg-1) induced tonic seizures in all the control mice. The most rapid onset of seizure relating to polyphenolic extract (50 mg kg-1) before PTZ was 9.59 ± 23.56 seconds and it was 103.0 ± 6.36 seconds at 200 mg kg-1. Conclusions: E. caucasicum methanolic and polyphenolic extracts had an antiepileptic effect against seizures induced by PTZ in mice, but the effect of polyphenolic extract was more potent.

Alantolactone and isoalantolactone suppress maximal electroshock-induced tonic seizures in mice

Introduction and objective. The aim of this study was to perform the anticonvulsant screening test to determine whether two sesquiterpene lactones (alantolactone and isoalantolactone) isolated from herbs and medicinal plants offer a distinct protection against maximal electroshock (MES)-induced tonic seizures in mice. Materials and methods. The screening test was performed for alantolactone and isoalantolactone administered intraperitoneally in a constant dose of 300 mg/kg at 4 various pretreatment times (i.e., 15, 30, 60 and 120 min.) before the MES test. Tonic hind limb extension (seizure activity) was evoked in adult male albino Swiss mice by a current (sine-wave, 25 mA, 500 V, 50 Hz, 0.2 s stimulus duration) delivered via ear-clip electrodes. Subsequently, the median effective doses (ED 50 values) for alantolactone and isoalantolactone were determined in the MES test in mice. Results. In the screening test, both compounds produced a 37.5% protection against MES-induced tonic seizures in mice, when administered i.p. at 15 min. prior to the MES test. In contrast, alantolactone and isoalantolactone administered i.p. at 30, 60 and 120 min. prior to the test produced no anticonvulsant activity in mice subjected to the MES test. The experimentallyderived ED 50 values for alantolactone and isoalantolactone, administered intraperitoneally at 15 min. before the MES test, were 322 (281–369) mg/kg and 336 (285–396) mg/kg, respectively. Conclusions. Alantolactone and isoalantolactone (2 sesquiterpene lactones) are worth considering as potentially favourable compounds in epileptology, if the results from this study could be extrapolated into clinical settings.

Ivabradine (a hyperpolarization activated cyclic nucleotide-gated channel blocker) elevates the threshold for maximal electroshock-induced tonic seizures in mice

BackgroundThe aim of this study was to determine the effect of ivabradine (a hyperpolarization activated cyclic nucleotide-gated channel (HCN) blocker) on the threshold for maximal electroshock (MEST)-induced tonic seizures in mice. MethodsElectroconvulsionswere produced inmice bymeans of a current (sine-wave, 50Hz,maximum500V, strength from3–10mA, ear-clip electrodes, 0.2-s stimulus duration, tonic hindlimb extension taken as the endpoint). ResultsIvabradine administered intraperitoneally (ip), 60min before the MEST test, at doses of 5 and 10mg/kg, did not alter the threshold for maximal electroconvulsions in mice. In contrast, ivabradine at doses of 15 and 20mg/kg significantly elevated the threshold for maximal electroconvulsions in mice (p<0.05 and p<0.001, respectively). Linear regression analysis of ivabradine doses and their corresponding threshold increases allowed determination of the threshold increasing doses by 20 and 50% (TID20 and TID50 values) that elevate the threshold in drug-treated animals over the threshold in control animals. The experimentally derived TID20 and TID50 values for ivabradine were 8.70 and 18.29mg/kg, respectively. ConclusionsBased on this preclinical study, one can ascertain that ivabradine dose-dependently increased the threshold for MEST-induced seizures, suggesting the antiseizure activity of the compound in this seizure model in mice.

Effects of various naturally occurring compounds (arbutin, borneol, esculetin, esculin, ellagic acid, gallic acid, hesperidine, piperitol, piperonal, quercetin, thymoquinone and ursolic acid) against maximal electroshock-induced seizures in mice

The aim of this study was to perform the anticonvulsant screening test to select some naturally occurring substances isolated from herbs and medicinal plants that could offer a distinct protection against maximal electroshock (MES)-induced tonic seizures in mice. The screening test was performed for 12 substances (i.e., arbutin, borneol, esculetin, esculin, ellagic acid, gallic acid, hesperidine, piperitol, piperonal, quercetin, thymoquinone and ursolic acid) administered intraperitoneally in a constant dose of 300 mg/kg at various pretreatment times (i.e., 15, 30, 60 and 120 min.) before the MES test. Results indicate that only borneol produced a 75% protection against MES-induced tonic seizures in mice, when administered i.p. at 15 min. prior to the MES test. Borneol administered i.p. at 30 min before the MES test protected a 37.5% of animals tested, whereas the compound administered i.p. at 60 min. prior to the test exerted barely a 12.5% protection against MES-induced tonic seizures. In contrast, borneol administered i.p. at 120 min. prior to the test produced no anticonvulsant activity in mice subjected to the MES test. The remaining substances tested in the mouse MES model (i.e., arbutin, esculetin, esculin, ellagic acid, gallic acid, hesperidine, piperitol, piperonal, quercetin and ursolic acid) exerted no or negligible anti-seizure activity after their i.p. administration to mice. In conclusion, borneol is worthy of consideration as a potentially favorable compound in epileptology, if the results from this study could be extrapolated into clinical settings.

Anticonvulsant activity of Nylandtia spinosa L. Dumont (Polygalaceae) aqueous and methanol leaf extracts in mice

Aqueous and methanol leaf extracts of Nylandtia spinosa L. Dumont (Polygalaceae) were evaluated for anticonvulsant activity against tonic seizures produced in mice by pentylenetetrazole (PTZ), bicuculline, picrotoxin, and N-methyl-DL-aspartic acid (NMDLA). Aqueous leaf extract of N. spinosa (50-400 mg/kg, i.p.) and methanol extract (50-400 mg/kg, i.p.) significantly attenuated PTZ (95 mg/kg, i.p.)-induced tonic seizures. Doses of 400 mg/kg (i.p.) and 100-400 mg/kg (i.p.) of aqueous extract of N. spinosa significantly delayed the onset of tonic seizures elicited by bicuculline (35 mg/kg, i.p.) and picrotoxin (12 mg/kg, i.p.), respectively. Methanol extract (200-400 mg/kg, i.p.) and (50-400 mg/kg, i.p.) significantly delayed the onset of tonic seizures induced by bicuculline (35 mg/kg, i.p.) and picrotoxin (12 mg/kg, i.p.), respectively, whereas 400 mg/kg (i.p.) significantly reduced the incidence of picrotoxin (12 mg/kg, i.p.)-induced seizures. Both aqueous and methanol leaf extracts of N. spinosa did not affect NMDLA (400 mg/kg, i.p.)-induced tonic seizures. Phenobarbitone (12.5 mg/kg, i.p.) and diazepam (0.5 mg/kg, i.p.) antagonized tonic seizures induced by PTZ (95 mg/kg, i.p.), bicuculline (35 mg/kg, i.p.), and picrotoxin (12 mg/kg, i.p.) but did not affect NMDLA (400 mg/kg, i.p.)-induced seizures. Phenytoin (30 mg/kg, i.p.) did not alter the tonic seizures produced by either PTZ (95 mg/kg, i.p.), bicuculline -2-(35 mg/kg, i.p.), or picrotoxin (12 mg/kg, i.p.). The results obtained indicate that both aqueous and methanol leaf extracts of N. spinosa possess anticonvulsant property, thus justifying the use of the plant by traditional medicine practitioners in the treatment of epilepsy. The relatively high LD(50) of greater than 3600 mg/kg (p.o.) and 1780 mg/kg (i.p.) obtained with the aqueous extract suggest that the plant is relatively safe in mice. The phytochemical analysis carried out showed the presence of tannins, saponins, reducing sugars, alkaloids, flavonoids, triterpene steroids, and cardiac glycosides in the plant material.

Gamma-aminobutyric acid and mefloquine-induced seizures in mice

The role of GABAergic mechanism in the convulsant effect of mefloquine was investigated in mice. Mefloquine dose dependently induced tonic seizures in mice. Aminooxyacetic acid, diaminobutyric acid and muscimol significantly protected mice against mefloquine-induced seizures by significantly delaying the onset and decreasing the incidence of the seizures. Bicuculline and picrotoxin significantly enhanced the seizure producing effect of mefloquine and also significantly antagonised the protective effect of muscimol against the seizures. Phenobarbitone and diazepam effectively protected mice against mefloquine-induced seizures. Phenytoin did not alter mefloquine-induced seizures. These data indicate that GABA mechanisms might be involved in seizures produced by mefloquine in mice.

GABA-B receptor activation in the rat globus pallidus potently suppresses pentylenetetrazol-induced tonic seizures

To determine the involvement of the globus pallidus in mediating epilepsy, the effects of microinjection of a GABA uptake blocker (tiagabine), a benzodiazepine agonist (zolpidem) and a GABA-B receptor agonist (baclofen) on pentylenetetrazol (PTZ)-induced tonic seizure were examined in adult rats. Administration of PTZ induced tonic seizures in all control animals, accompanied with a 100% mortality rate. Pretreatment with bilateral intrapallidal microinjection of tiagabine (1 mM) suppressed the incidence of tonic seizures to 67.7% and reduced the mortality rate to 16.7%. Furthermore, the latency to tonic seizures was 1,275 +/- 277 s, which was significantly longer than that of the corresponding control animals (319 +/- 225 s). On the other hand, administration of zolpidem (1 mM) was without significant effects on the mortality rate, the incidence and latency of the tonic seizure. In sharp contrast, microinjection of baclofen (1 mM) completely suppressed PTZ-induced tonic seizures and reduced the mortality rate to 0%. This effect was largely abolished by co-injection of the GABA-B receptor antagonist CGP55845. To elucidate the direct cellular action of baclofen, the excitability and membrane potential of globus pallidus neurons were studied by cell-attached and whole-cell patch-clamp recordings in the brain slice. Bath application of baclofen (50 microM) significantly reduced the firing of these neurons, and was often accompanied by a clear membrane hyperpolarization, in a CGP55845-sensitive manner. These data suggest that activation of GABA-B receptors in globus pallidus could significantly modulate PTZ-induced tonic seizures.

GABA-B Receptor Activation in the Rat Globus pallidus Potently Suppresses Pentylenetetrazol-Induced Tonic Seizures

To determine the involvement of the globus pallidus in mediating epilepsy, the effects of microinjection of a GABA uptake blocker (tiagabine), a benzodiazepine agonist (zolpidem) and a GABA-B receptor agonist (baclofen) on pentylenetetrazol (PTZ)-induced tonic seizure were examined in adult rats. Administration of PTZ induced tonic seizures in all control animals, accompanied with a 100% mortality rate. Pretreatment with bilateral intrapallidal microinjection of tiagabine (1 mM) suppressed the incidence of tonic seizures to 67.7% and reduced the mortality rate to 16.7%. Furthermore, the latency to tonic seizures was 1,275 ± 277 s, which was significantly longer than that of the corresponding control animals (319 ± 225 s). On the other hand, administration of zolpidem (1 mM) was without significant effects on the mortality rate, the incidence and latency of the tonic seizure. In sharp contrast, microinjection of baclofen (1mM) completely suppressed PTZ-induced tonic seizures and reduced the mortality rate to 0%. This effect was largely abolished by co-injection of the GABA-B receptor antagonist CGP55845. To elucidate the direct cellular action of baclofen, the excitability and membrane potential of globus pallidus neurons were studied by cell-attached and whole-cell patch-clamp recordings in the brain slice. Bath application of baclofen (50 µM) significantly reduced the firing of these neurons, and was often accompanied by a clear membrane hyperpolarization, in a CGP55845-sensitive manner. These data suggest that activation of GABA-B receptors in globus pallidus could significantly modulate PTZ-induced tonic seizures.

Effects of seizure repetition on postictal and interictal neurocardiac regulation in the rat.

Human epilepsy is associated with abnormalities in cardiac regulation, as measured by reductions of heart rate variability (HRV) and approximate entropy (ApEn), but it is not known how these abnormalities are related to seizure experience. Baseline electrocardiogram (ECG) was recorded from seizure-naive rats. They were subjected daily to maximal electroshock (MES), which induced tonic seizures with hindlimb extension, for a total of 10 days. ECG was obtained for 30 min before and after the first and last seizure. R-R variability, spectral variability, and ApEn were calculated to determine changes in pre- and postictal cardiac regulation. Before the last seizure, interictal parameters were compared with baseline values to determine changes in interictal HRV as a consequence of seizure repetition. Postictal values obtained after the last seizure were compared with the initial postictal data to look for changes in postictal cardiac regulation. During the postictal state, a mild, but significant, loss of ApEn was present after either the first or last seizure. Seizure repetition induced loss of R-R variability and high-frequency spectral band, which was present both interictally and postictally. The results suggest that convulsive seizures are associated with an immediate reduction of the complexity of cardiac rhythm regulation, as reflected by reductions of ApEn. Seizure repetition may induce long-term neural abnormalities in neurocardiac regulatory systems, especially parasympathetic, which limit appropriate autonomic responses. These acquired abnormalities may, in turn, predispose individuals to cardiac arrhythmia and sudden unexpected death in epilepsy.

Anticonvulsant activity of aqueous extract of Leonotis leonurus.

Water extract of Leonotis leonurus was tested for anticonvulsant activity against seizures produced in mice by pentylenetetrazole, picrotoxin, bicuculline and N-methyl-DL-aspartic acid (intraperitoneal injections). L. leonurus extract in the doses of 200 and 400 mg/kg respectively protected 37.5% and 50% of animals used and significantly (p < 0.05; Student's t-test) delayed pentylenetetrazole (90 mg/kg)-induced tonic seizures. Similarly, the same doses of L. leonurus extract significantly (p < 0.05; Student's t-test) delayed the onset of tonic seizures produced by picrotoxin (8 mg/kg) and N-methyl-DL-aspartic acid (400 mg/kg). However, all the doses of aqueous extract of L leonurus used did not alter the seizures induced by bicuculline (20 mg/kg) to any significant extent. The data suggest that the extract of L. leonurus has anticonvulsant activity and may probably be acting through non-specific mechanisms, since it affects both gabaergic and glutaminergic systems. High performance liquid chromatography (HPLC) and phytochemical tests carried out respectively show a spectrum profile, characteristic of L. leonurus and the presence of alkaloids, saponins and tannins in the extract.

Involvement of proprioceptive feedback in brainstem-triggered convulsions.

In rodents, specific motor components of generalized convulsive seizures depend on two distinct anatomic substrates: (a) forebrain networks are responsible for facial and forelimb clonus with or without rearing and falling; and (b) brainstem networks are responsible for running-bouncing fits and tonic convulsions. To investigate the requirement of proprioceptive inputs in the generation of these two different types of seizures, we compared the effects of neuromuscular blockade by D-tubocurarine on the EEG expression of brainstem- and forebrain-triggered seizures. Unilateral electrical stimulations were applied for 50 consecutive days in freely moving male adult rats through a bipolar electrode aimed at the dorsal hippocampus (n = 5), the occipital cortex (n = 4), the inferior colliculus (n = 6), or the midbrain reticular formation (n = 6). Two days after the last stimulation, rats were paralyzed with d-tubocurarine and stimulated in the same way. In brainstem structures, the first electrical stimulation induced tonic seizures concomitant with low-voltage cortical activity; repetition of daily stimulations progressively induced tonic-clonic seizures associated with high-amplitude cortical spike-wave discharges. After immobilization by d-tubocurarine, brainstem stimulations failed to induce any EEG paroxysm. In forebrain structures, repeated electrical stimulations produced a classic kindling with progressive occurrence of clonic seizures associated with large cortical discharges; d-tubocurarine left unchanged the EEG pattern of these latter seizures. These data suggest that proprioceptive reafferentation resulting from movement is necessary for the generation of self-sustained brainstem seizures but is not implicated in the elaboration of forebrain seizures.

The role of technical, biological and pharmacological factors in the laboratory evaluation of anticonvulsant drugs. VI. Seasonal influences on maximal electroshock and pentylenetetrazol seizure thresholds.

There is strong evidence for circadian rhythmicity in certain seizure types, whereas only a few studies have addressed the possibility of seasonal rhythms in convulsive activity. In the present experiments, seizure thresholds to different types of seizures were determined twice per month over a period of 13 months in mice under controlled environmental conditions, i.e., constant photoperiod, temperature, humidity, and food. Each group of animals was used for only one experiment, and the age of the mice used per month was the same throughout the study. Furthermore, all experiments were done at the same time in the morning to avoid circadian variation. Thresholds for the following seizure types were determined: (1) tonic hindlimb seizures induced by electrical (transauricular) stimulation; (2) myoclonic seizures induced by intravenous (i.v.) infusion of pentylenetetrazol (PTZ); (3) generalized clonic seizures in response to i.v. PTZ; and (4) tonic forelimb seizures induced by PTZ. A significant seasonality was determined for myoclonic and clonic PTZ seizure thresholds with highest thresholds between February and April and lowest thresholds between July and September. No clear seasonality was seen for chemically or electrically induced tonic seizures. Determination of plasma corticosterone did not disclose any seasonal rhythm in adrenal corticosteroid production that resembled the circannual variation in myoclonic and clonic seizure thresholds. In conclusion, our experiments suggest the existence of seasonal rhythms in PTZ seizure thresholds in laboratory animals despite standardized environmental conditions. A possible explanation for the findings may be the known seasonal alteration of the geomagnetic field which, by its effect on the pineal production of melatonin, may act as a seasonal synchronizor ("zeitgeber") in animals in the absence of other synchronizing forces, such as seasonal changes in photoperiod and ambient temperature.

Effect of the glycine/NMDA receptor partial agonist, D-cycloserine, on seizure threshold and some pharmacodynamic effects of MK-801 in mice

Acute treatment of mice with D-cycloserine (a high efficacy, partial agonist at strychnine-insensitive glycine receptors) resulted in dose- and time-dependent increases in the threshold for electrically induced tonic seizures. This anticonvulsant effect was observed at doses which did not induce motor impairment, as determined by the rotarod test. Despite the relatively high intrinsic efficacy of D-cycloserine at glycine receptors, this drug did not produce proconvulsant effects in mice at any of the doses (5–320 mg/kg) or time points examined. Prolonged treatment with D-cycloserine led to a reduction of its anticonvulsant effect. Similar to D-cycloserine, the uncompetitive N- methyl- D-aspartate (NMDA receptor antagonist, MK-801 (dizocilpine), dose dependently increased the electroconvulsive threshold. Combined treatment with MK-801 and D-cycloserine led to significant anticonvulsant effects, but these effects were simply additive and not synergistic. In contrast to anticonvulsant activity, the motor impairing effect of MK-801 was markedly potentiated by D-cycloserine. The data substantiate that high efficacy glycine/NMDA receptor partial agonists such as D-cycloserine exert anticonvulsant activity at non-toxic doses. The finding that motor impairing but not anticonvulsant effects of MK-801 were potentiated by D-cycloserine suggests that different pharmacodynamic actions of NMDA receptor antagonists are differentially modulated by the glycine receptor, which could be related to the regional heterogeneity of the NMDA receptor complex in the brain.

Search for an antidote to electroconvulsion and lethality in aminophylline-sensitized mice

Diazepam (10 mg/kg i.p.) or MK-801 (0.25 mg/kg i.p.) offered complete protection against corneal electroshock (30 mA × 0.2 s)-induced tonic seizures and lethality but failed to protect from aminophylline (150 mg/kg i.p.) + electroshock (15 mA × 0.2 s)-induced tonic seizures and lethality in mice. The diazepam (2.5 mg/kg i.p.) and MK-801 (0.25 mg/kg i.p.) comnination completely protected the mice from aminophylline + electroshock-induced seizures and lethality. Sodium valproate (500 mg/kg i.p.) protected the mice from electroshock (30 mA) per se and aminophylline + electroshock (15 mA)-induced seizure and lethality. The present study established the neurosensitizing potential of a single, non-convulsive dose of aminophylline for electroconvulsion due to subthreshold intensity electroshock and demonstrated the prophylactic efficacy of sodium valproate and the synergistic therapeutic potential of diazepam and MK-801 combination against such seizure attacks.

In vivo interaction of a polyamine with the NMDA receptor

We have investigated the ability of spermidine to modulate N-methyl-DL-aspartic acid (NMDLA)-induced tonic seizures in mice. Here we present evidence that the polyamine site may not normally be fully activated and that interactions at this site may have important consequences in the whole animal

Securinine alkaloids: A new class of GABA receptor antagonist

Experiments were undertaken to determine the site of action of securinine and related convulsant indolizidines. All of these compounds induced tonic seizures in mice, with CD 50 values ranging from 11 to 87 mg/kg. The CD 50 for bicuculline was found to be 8 mg/kg. Equilibrium binding assays revealed that securinine and dihydrosecurinine inhibit [ 3H]GABA binding to rat brain membranes with an IC 50 of approximately 50 μM, which is some 7 times less potent than bicuculline. Allosecurinine and virosecurinine have IC 50 values greater than 1 mM. Both dihydrosecurinine and securinine inhibited GABA-stimulated benzodiazepine binding in rat brain membranes, though they were somewhat weaker than bicuculline in this respect. Other binding assays revealed that securinine and its analogs were inactive as inhibitors of bicuculline-insensitive GABA binding, benzodiazepine, cholinergic muscarinic, and β-adrenergic receptor binding. In addition, while thiocyanate ion increased the apparent binding potency of bicuculline 10-fold, it had little effect on that of securinine. Extracellular electrophysiological studies on neurons in the cat spinal cord indicated that securinine and dihydrosecurinine blocked the inhibitory action of GABA while having no effect on that of glycine. Allo- and virosecurinine were much less active as GABA receptor antagonists in this test. These results suggest that, like bicuculline, securinine and dihydrosecurinine are selective antagonists of GABA recognition sites on mammalian central neurons.

Development and persistence of kindled seizures after repeated injections of pentylenetetrazol in rats and guinea pigs.

Pentylenetetrazol (PTZ) was injected into rats (30 or 35 mg/kg) and guinea pigs (40 or 45 mg/kg) daily or every second day. A progressive development of seizure activity after this treatment was observed. Doses ineffective after the first injection induced tonic seizures after 20 injections. Both kinds of treated animals immediately developed tonic seizures when PTZ was injected after a few months interruption for one time only. The results support the assumption that seizures induced by chronic injection of PTZ are similar to kindled seizures evoked by daily electrical stimulation and can be regarded as a model of epileptogenesis.