Effect of anticonvulsants on seizures developing in the course of daily administration of pentetrazol to rats

Progressive behavioral and electroencephalographic (EEG) changes were examined following daily administration of pentetrazol (PTZ) to rats. A dose (40 mg/kg/day i.p.) of PTZ which, on the first day, induced clonic convulsions with spike and wave complexes, over several days progressively increased its effect and finally induced ‘violent convulsions’ with EEG seizures of high frequency components. In rats showing these violent convulsions, the PTZ convulsive threshold was decreased and, even after a 4- to 10-month resting period, the violent convulsion was elicited with the same dose of PTZ. Trimethadione and phenobarbital in doses blocking clonic convulsion in normal rats, did not suppress these violent convulsions. Higher doses of the two drugs were necessary to suppress the violent convulsion. Diphenylhydantoin did not suppress either type of convulsions. It is suggested that the progressive development of seizure by PTZ is a kindling effect and that a part of the neuronal mechanisms by which the violent convulsion occurs is involved in the mechanisms underlying the clonic convulsion.     

Tolerance to the anti-pentylenetetrazole effects of diazepam in the mouse

The protective effects of acute and chronic diazepam administration (4 mg/kg) against seizures induced by pentylenetetrazole (PTZ) and picrotoxin were investigated. Considering the incidence of tonic-clonic convulsions, tolerance to the protective effects of diazepam was evident by day 5 if the mice were challenged with PTZ (120 mg/kg), by day 10 if the challenge was picrotoxin (8 mg/kg) and by day 20 if the challenge was PTZ (105 mg/kg). Diazepam retained its protective effects against tonic-clonic convulsions induced by PTZ (90 and 60 mg/kg) for 45 days, but the incidence of myoclonic jerks revealed tolerance after 5 days.     

Anticonvulsant activity of carbamazepine and N6-L-phenylisopropyladenosine in rabbits. Relationship to adenosine receptors in central nervous system

The present work deals with an EEG and behavioral study on the effects of carbamazepine (CBZ) and N6-L-phenylisopropyladenosine (L-PIA) against the convulsions due to caffeine and pentylenetetrazole (PTZ) in rabbits. Pretreatment with L-PIA (1, 3 and 4 mg/kg) caused a dose-related inhibition of the motor convulsions and the EEG "grand mal" ictal seizure induced by caffeine (75 mg/kg IV). On the contrary, L-PIA given at the high dose of 5 mg/kg IV partially inhibited the EEG and motor seizures elicited by PTZ (20 mg/kg IV). CBZ completely antagonized the EEG and motor convulsions induced by caffeine, while exerted only a protective action towards the EEG and motor convulsions due to PTZ. The administration of an ineffective dose of CBZ (5 mg/kg IV) was able to enhance the protective action of L-PIA towards caffeine-induced convulsions. This synergistic action between CBZ and L-PIA is also present towards the spike-and-wave complexes elicited by PTZ (10 mg/kg). These results confirm that the purinergic system plays an important role in the regulation of the CNS excitability. They suggest therefore, that the anticonvulsant properties of CBZ may be at least partially explained by an influence of this drug on the purinergic system.     

Effect of phosphamidon on convulsive behavior and biochemical parameters: modulation by progesterone and 4′-chlorodiazepam in rats

Phosphamidon (PHOS) has been shown to affect nervous system adversely. The present study was designed to explore the modulation of the effects of PHOS on convulsions by neurosteroids, progesterone (PROG), and 4′-chlorodiazepam (4′-CD), in both acute and chronic seizure models. In acute study, seizures were induced by either pentylenetetrazole (PTZ) injection or maximal electroshock seizures, while in the chronic study, kindling was induced by injecting PTZ (30 mg/kg, s.c.) on alternate days three times in a week. Oxidative stress was assessed in the brain by measuring the levels of malondialdehyde (MDA), acetylcholinesterase (AChE), and non-protein thiol (NP-SH). PROG and 4′-CD were able to modulate the PHOS-induced convulsions in acute PTZ convulsions as well as in chronic kindling model. However, they failed to reverse the derangements in oxidative stress parameters of MDA and NP-SH produced by PHOS in kindled animals. PROG significantly increased the AChE activity in untreated rats, while PROG and 4′-CD reversed the AChE activity inhibition induced by PHOS. The study indicates a possible anticonvulsive mechanism of neurosteroids, since both PROG and 4′-CD reversed PHOS-induced inhibition of AChE activity. The neurosteroids seem to play a protective role in PHOS-induced convulsions besides their antioxidant property.     

Hesperidin potentiates the neuroprotective effects of diazepam and gabapentin against pentylenetetrazole-induced convulsions in mice: Possible behavioral,biochemical and mitochondrial alterations

Aim:

Epilepsy is a chronic neurological disorder with complex pathophysiology. Several evidences suggest a role of oxidative stress and mitochondrial dysfunction in pathophysiology of epilepsy. Hesperidin (Hesp) acts as a powerful anti-oxidant agent against superoxide, singlet oxygen, and hydroxyl radicals. Thus, this study was undertaken to evaluate the possible neuroprotective mechanism of Hesp against pentylenetetrazole (PTZ)-induced convulsions in mice.

Materials and Methods:

Sixty males Laca mice (20-25 g) were randomly divided into 10 treatment groups (n = 6). Seven days pretreatment of Hesp (100, 200 mg/kg, p.o.) was carried out before PTZ (80 mg/kg, intraperitoneal [i.p.]) challenge, whereas diazepam (DZP) (0.2, 0.5 mg/kg) and gabapentin (Gbp) (10, 20 mg/kg) were administered i.p. 30 min before PTZ administration, that is, on 7^th day. Following PTZ challenge, severity of convulsions (onset of jerks, myoclonic seizures, extensor phase and death), brain anti-oxidant enzyme levels and mitochondrial complex enzymes activities were estimated.

Results:

Single i.p. PTZ (80 mg/kg) challenge demonstrated severe convulsions, oxidative damage (raised lipid peroxidation [LPO], nitrite concentration as well as depleted reduced glutathione, superoxide dismutase and catalase levels), and depletion of mitochondrial enzyme Complex (I, II, IV) activities. Hesp (200 mg/kg), DZP (0.5 mg/kg) and Gbp (20 mg/kg) pretreatments attenuated PTZ induced behavioral, biochemical and mitochondrial alterations. However, administration of Hesp (100 mg/kg) in combination with DZP (0.2 mg/kg) or Gbp (10 mg/kg) potentiated their neuroprotective effect, which was significant as compared to their effects in PTZ treated animals.

Conclusion:

Hesp possesses potent anticonvulsant activity which might be mediated through modulation of gamma-amino butyric acid/benzodiazepine receptor action.KEY WORDS: Mitochondrial dysfunction, myoclonic jerks, oxidative stress, seizure     

Anticonvulsant activity of fraction isolated from ethanolic extract of heartwood of Cedrus deodara

The heartwood of Cedrus deodara is traditionally used for the treatment of neurological disorders in India. In this study, the compound 3,4-bis(3,4-dimethoxyphenyl)furan-2,5-dione (BDFD) isolated from the ethanolic extract of C. deodara was evaluated for its anticonvulsant activity. The experimental studies were carried out in albino mice (18–22 g) and rats (180–220 g), employing different models of convulsions. The N-methyl-d-aspartic acid (NMDA)-induced lethality test and estimation of brain gamma-aminobutyric acid (GABA) were carried out to investigate the mechanism of action of this compound. BDFD gave dose-dependent protection against pentylenetetrazole (PTZ)-, pilocarpine- and 6-Hz-induced convulsions but it could not inhibit NMDA-induced lethality. Motor incoordination was displayed when the BDFD dose exceeded 400 mg/kg, whereas the therapeutic dose was below 100 mg/kg in the PTZ, pilocarpine and 6-Hz models (39–90 mg/kg). Furthermore, brain GABA estimation revealed that this compound increases the GABA level. BDFD dose levels up to 150 mg/kg did not prevent NMDA-induced lethality, which proves its weak influence on the excitatory neurotransmitter glutamate. The findings of the experiments on various animal models clearly demonstrated that BDFD possesses anticonvulsant activity by enhancing inhibitory GABAminergic neurotransmission.     

Toxic effects of Triclosan on the detoxification system and breeding of Daphnia magna

The toxic effects of different concentrations of Triclosan (TCS) (1–128 μg/L) on Daphnia magna (D. magna) were investigated by acute (48 h) and chronic (21-day) toxicity tests. The response of antioxidase system and Phase I metabolism process of D. magna exposed to TCS were investigated by measuring a series of biomarkers including glutathione S-transferase (GST), catalase (CAT), superoxide dismutase (SOD), malondialdehyde (MDA), 7-ethoxyresorufin O-deethylase (EROD), Erythromycin N-demethylase (ERND) and Aminopyrine N-demethylase (APND). The 48 h LC₅₀ of TCS was 330 μg/L for D. magna. In the chronic test, total number of neonates per female, body length and the intrinsic rate of natural increase (r) of D. magna increased at the low exposure concentrations (1–16 μg/L) and decreased at the high concentrations (64–128 μg/L), while the total number of molting per adult decreased continually. The GST and CAT activities showed no significant increase in all treatments, and SOD activities were induced after 24-h exposure and inhibited after 48-h exposure at 4–128 μg/L of concentrations. The MDA content increased after 6-h exposure but decreased after 48-h exposure at 4–128 μg/L. EROD activities initially increased after 6-h exposure, but decreased after 24 and 48-h exposure, ERND and APND activities showed a similar temporal pattern among different treatments groups. SOD, MDA and APND were sensitive to TCS, thus they are suitable as potential biomarkers for the exposure to TCS.     

Protective effect of D-002, a mixture of beeswax alcohols, against indomethacin-induced gastric ulcers and mechanism of action

D-002, a mixture of higher aliphatic beeswax alcohols, produces gastroprotective and antioxidant effects. To investigate the gastroprotective effect of D-002 against indomethacin-induced ulcers, oxidative variables and myeloperoxidase (MPO) activity in the rat gastric mucosa were examined. Rats were randomized into six groups: a negative vehicle control and five indomethacin (50 mg/kg) treated groups, comprising a positive control, three groups treated orally with D-002 (5, 25 and 100 mg/kg) and one group with omeprazole 20 mg/kg intraperitoneally (ip). The contents of malondialdehyde (MDA), protein carbonyl groups (PCG), hydroxyl radical generation and catalase (CAT), glutathione peroxidase (GSH-PX), superoxide dismutase (SOD) and MPO enzyme activities in the rat gastric mucosa were assessed. Indomethacin increased the content of MDA and PCG, the generation of *OH radical and MPO enzyme activity, while it decreased the CAT, GSH-PX and SOD activities as compared to the negative controls. D-002 (5–100 mg/kg) significantly and dose-dependently reduced indomethacin-induced ulceration to 75 %. Also, D-002 decreased the content of MDA and PCG, the generation of hydroxyl radicals and MPO activity as compared to the positive controls. The highest dose of D-002 (100 mg/kg) increased significantly GSH-PX and SOD activities, while all doses used increased CAT activities. Omeprazole 20 mg/kg, the reference drug, reduced significantly the ulcers (93 %), MDA and PCG, the generation of hydroxyl radicals and MPO activity, and increased the CAT, GSH-PX and SOD activities. D-002 treatment produced gastroprotective effects against indomethacin-induced gastric ulceration, which can be related to the reduction of hydroxyl radical generation, lipid peroxidation, protein oxidation and MPO activity, and to the increase of the antioxidant enzymes activities in the rat gastric mucosa.     

Effect of orally administered dextromethorphan on theophylline- and pentylenetetrazol-induced seizures in rats

Dextromethorphan, widely used as an antitussive, has recently been shown to protect animals against maximal electroshock and excitatory amino acid (N-methyl-D-aspartate)-induced convulsions. Its protective efficacy against theophylline-induced seizures was determined in this investigation in view of the limited effectiveness of presently available anticonvulsants against this manifestation of serious theophylline intoxication. Rats were pretreated with an oral dose of dextromethorphan (50 mg/kg) or saline solution. Fifteen minutes later, the rats were infused intravenously with theophylline [approximately 11 mg/(kg.min)] until the onset of maximal seizures. Pretreatment with dextromethorphan was associated with a significant decrease in the concentrations of theophylline in the cerebrospinal fluid and serum at the pharmacologic endpoint. To further explore this unanticipated effect, a similar experiment was performed with the convulsant pentylenetetrazol (PTZ), which was infused at a rate of approximately 3.4 mg/(kg.min) until the onset of maximal seizures. Dextromethorphan-pretreated animals required a significantly larger dose of PTZ than did controls to produce the first myoclonic jerk, but a significantly smaller dose of the convulsant to produce maximal seizures. Serum and cerebrospinal fluid concentrations of PTZ at onset of maximal seizures were significantly lower in dextromethorphan-treated than in control animals. The proconvulsant activity of dextromethorphan with respect to theophylline-induced maximal seizures is similar to that of phenytoin, and is consistent with other pharmacologic evidence of such similarity.     

Influence of lithium on the anticonvulsant activity of carbamazepine

The present study was undertaken to see whether the recently reported synergism between lithium and carbamazepine (CBZ) in mania also extends against convulsions. The anti-convulsant effect of various doses of CBZ was assessed in albino rats pretreated with vehicle or lithium salt (0.54 mEg/kg/day, p.o. for 9 days). The animals were subjected to 3 tests: maximum electro shock seizures (MES); minimum electro convulsive thresholds (MET) and pentylenetetrazol (PTZ)-induced convulsions: abolition of hind limb extension after electro shock, increases in the MET for appearance of neck jerk and absence of convulsions for one hr after PTZ were taken as parameters of the anticonvulsive effect respectively. In the MES and MET tests lithum did not alter the anticonvulsive effect of CBZ. Lithium, however, potentiated the anticonvulsant effect of CBZ against PTZ-induced convulsions.     

The use of the dog electroencephalogram (EEG) in safety pharmacology to evaluate proconvulsant risk

INTRODUCTION: The dog is frequently used for cardiovascular safety pharmacology and for toxicology studies, but is not often used for central nervous system (CNS) safety pharmacology purposes. We have therefore examined the electroencephalogram (EEG) in conscious dogs by means of radio-telemetry methods using the proconvulsant agent pentylenetetrazole (PTZ) as reference substance. Assessment of proconvulsant risk is an important aspect of CNS safety evaluation and the EEG is a sensitive technique for identifying pathologic brain activity, most importantly paroxysmal activity. METHODS: Dogs were implanted with epidural electrodes wired to subcutaneously placed radiotransmitters. Following baseline recording, the test substance was administered and the EEG and electromyogram (EMG) activities were recorded from dogs placed in slings. The EEG was assessed visually for abnormal activity and dogs were also continuously observed for the appearance of overt convulsive activity. The PTZ infusion was stopped and diazepam was administered as soon as clear and sustained EEG effects and/or behavioural symptoms occurred. RESULTS: Slow i.v. infusion of PTZ (1.5 mg/kg/min) induced clear paroxysmal effects on the EEG trace in the form of spike and wave trains of 4-5 Hz. Paroxysmal activity associated with clonic convulsions occurred between 17 and 36 min after the start of infusion (a mean of 24 min) but in most cases paroxysmal activity was observed approximately 60 s prior to any overt convulsive activity. DISCUSSION: These data show the usefulness of the telemetered dog EEG in safety pharmacology. The dog EEG is appropriate in situations where results from cardiovascular and CNS safety tests in the same species are required, or where the use of other species is contraindicated because of metabolic or pharmacokinetic particularities.     

苦李根对铅染毒大鼠血清SOD活性及肝组织MDA含量的影响

摘 要:目的 观察苦李根提取物（RCE）对铅中毒大鼠体内超氧化物歧化酶（SOD）活性和丙二醛（MDA）含量的影响。方法 将SD大鼠分成4组，以醋酸铅（20mg·kg-1）灌胃染毒，隔天一次，连续六次，给予依地酸钙钠（0.1g·kg-1）及苦李根提取物（1g·kg-1，0.5g·kg-1）,用试剂盒法检测血清SOD活性及肝脏MDA含量。结果 苦李根能显著升高铅中毒大鼠SOD活性和降低MDA含量（p<0.05, p<0.01）。结论 苦李根能对抗大鼠铅中毒引起SOD活性降低和MDA含量升高。     

Antiepileptic effects of two Rho-kinase inhibitors, Y-27632 and fasudil, in mice

BACKGROUND AND PURPOSE: Rho/Rho-kinase signalling is involved in many cellular events, including some in the CNS. However, the role of this pathway in epilepsy has not yet been assessed. Therefore, we determined the effects of two Rho-kinase inhibitors, Y-27632 and fasudil, on seizures induced by pentylenetetrazole (PTZ) or maximal electroconvulsive shock (MES). EXPERIMENTAL APPROACH: Effects of Y-27632 (5-10 mg kg(-1)) and fasudil (5-25 mg kg(-1)) on duration of myoclonic jerks, clonic and tonic convulsions, tonic hindlimb extensions and percentage of tonic convulsion index, as well as recovery latency for righting reflex were investigated in mice stimulated with PTZ (65 mg kg(-1)) or MES (50 Hz, 50 mA and 0.4 s). These inhibitors were also tested on a model of kindling induced by PTZ (35 mg kg(-1), for 11 days). Membrane and cytosolic levels of RhoA protein were measured in brain homogenates from kindled mice. KEY RESULTS: Y-27632 and fasudil diminished onset of myoclonic jerks, clonic convulsions and tonic hindlimb extensions in mice given PTZ. These inhibitors suppressed the percentage of tonic convulsion index and recovery latency for righting reflex in the mice excited with MES. Western blotting demonstrated that Rho translocation to plasma membrane increased in the brain homogenates obtained from PTZ-kindled mice. However, the Rho-kinase inhibitors at the given doses did not change motor coordination of the mice. CONCLUSIONS AND IMPLICATIONS: Rho/Rho-kinase signalling may play a role in epilepsy induced by PTZ and MES. Furthermore, Rho-kinase inhibitors could be novel important antiepileptic agents.     

Antiepileptogenic effects of borneol in pentylenetetrazole-induced kindling in mice

Borneol, a bicyclic monoterpene, can easily cross the blood brain barrier and was found to possess gamma amino butyric acid (GABA) modulatory effect. The present study was aimed at investigating the antiepileptogenic effect of borneol in the pentylenetetrazole (PTZ)-induced kindling besides its ability to suppress oxidative stress and neuroinflammatory marker, glial fibrillary acidic protein (GFAP). Repeated administration of a subconvulsive dose of PTZ (35 mg/kg, i.p.) on every alternate day for 4 weeks produced kindling in mice. Borneol (5, 10, and 25 mg/kg, i.p.) and diazepam (1 mg/kg, i.p.) were given as a pretreatment prior to each PTZ injection during the progression of kindling. Oxidative stress parameters such as superoxide dismutase (SOD), reduced glutathione (GSH), catalase (CAT), and lipid peroxidation (LPO) were assessed at the end of the study. Neuronal damage was assessed by hematoxylin and eosin staining technique. GFAP was also evaluated in the hippocampus region of the brain by using immunohistochemistry. Borneol significantly suppressed the process of epileptogenesis in PTZ-kindled mice. The biochemical alterations induced by PTZ kindling were ameliorated in borneol-treated animals which was indicated by decreased LPO and increased SOD, GSH, CAT levels. The distinct neuronal damage observed in the kindled group was counteracted by borneol. Furthermore, it decreased the levels of GFAP which was manifested by reduced immunostaining. The above results are suggestive of the antiepileptogenic potential of borneol in the PTZ-induced kindling model of epilepsy, and thus, it could be a prospective molecule in the treatment of epilepsy.     

Anticonvulsant activity of MK-801 and nimodipine alone and in combination against pentylenetetrazole and strychnine

The effects of the N-methyl-D-aspartate receptor antagonist MK-801 and the dihydropyridine calcium channel antagonist nimodipine were assessed for their anticonvulsant activity alone and in combination against clonic convulsions to pentylenetetrazole (PTZ) and strychnine (STR) in mice. Nimodipine (2-20 mg/kg) and MK-801 (0.1 and 0.5 mg/kg) did not affect the number of mice displaying clonic convulsions to PTZ. However, nimodipine in a dose-dependent manner increased (100%) the latency to clonic convulsions and lethality (mortality from tonic extension convulsions and respiratory failure) following PTZ. In contrast, MK-801 did not increase the latency to PTZ convulsions, but prevented the lethal effects of PTZ. When combined, MK-801 and nimodipine produced a significant reduction in the number of animals (40-60%) displaying PTZ convulsions and a greater increase in the latency to PTZ convulsions than did nimodipine alone. In contrast, MK-801 decreased the onset time, and increased the severity of STR convulsions. A combination of MK-801 and nimodipine which afforded significant protection against PTZ convulsions did not affect STR convulsions. These findings suggest that MK-801 and nimodipine, while possessing significant anticonvulsant activity on their own, produce a potent anticonvulsant synergism against PTZ but not STR.     

Behavioral and genotoxic evaluation of rosmarinic and caffeic acid in acute seizure models induced by pentylenetetrazole and pilocarpine in mice

The goal of this study was to investigate the effects of rosmarinic acid (RA) and caffeic acid (CA) in the acute pentylenetetrazole (PTZ) and pilocarpine (PIL) seizure models. We also evaluated the effect of RA and CA on the diazepam (DZP)-induced sleeping time test and its possible neuroprotective effect against the genotoxic damage induced by PTZ and PIL. Mice were treated intraperitoneally (i.p.) with saline, RA (2 or 4 mg/kg), or CA (4 or 8 mg/kg) alone or associated to low-dose DZP. After, mice received a single dose of PTZ (88 mg/kg) or PIL (250 mg/kg) and were monitored for the percentage of seizures and the latency to first seizure (LFS) >3 s. Vigabatrin and DZP were used as positive controls. In the DZP-induced sleeping time test, mice were treated with RA and CA and 30 min after receiving DZP (25 mg/kg, i.p.). The alkaline comet assay was performed after acute seizure tests to evaluate the antigenotoxic profiles of RA and CA. The doses of RA and CA tested alone did not reduce the occurrence of seizures induced by PTZ or PIL. The association of 4 mg/kg RA + low-dose DZP was shown to increase LFS in the PTZ model, compared to the group that received only the DZP. In the DZP-induced sleeping time test, the latency to sleep was reduced by 4 mg/kg RA and 8 mg/kg CA. The PTZ-induced genotoxic damage was not prevented by RA or CA, but the PIL-induced genotoxic damage was decreased by pretreatment with 4 mg/kg RA (in cortex) and 4 mg/kg CA (in hippocampus). In conclusion, RA and CA presented neuroprotective effect against PIL-induced genotoxic damage and reduced the latency to DZP-induced sleep. Of the rosmarinic acid, 4 mg/kg enhanced the DZP effect in the increase of latency to clonic PTZ-induced seizures.     

Alteration of pentylenetetrazole-induced seizure threshold by chronic administration of ginger (Zingiber officinale) extract in male mice

Abstract

Context: Zingiber officinale Roscoe (Zingiberaceae), or ginger, used in traditional Chinese medicine, has antioxidant activity and neuroprotective effects. The effects of this plant on clonic seizure have not yet been studied.

Objective: The present study evaluated the anticonvulsant effect of ginger in a model of clonic seizures induced with pentylenetetrazole (PTZ) in male mice.

Materials and methods: The anticonvulsant effect of Z. officinale was investigated using i.v. PTZ-induced seizure models in mice. Different doses of the hydroethanolic extract of Z. officinale (25, 50, and 100?mg/kg) were administered intraperitonal (i.p.), daily for 1 week before induction of PTZ. Phenobarbital sodium (30?mg/kg), a reference standard, was also tested for comparison. The effect of ginger on to the appearance of three separate seizure endpoints, e.g., myoclonic, generalized clonic, and tonic extension phase, was recorded.

Results: Hydroethanolic extract of Z. officinale significantly increased the onset time of myoclonic seizure at doses of 25–100?mg/kg (55.33?±?1.91 versus 24.47?±?1.33?mg/kg, p?<?0.001) and significantly prevented generalized clonic (74.64?±?3.52 versus 47.72?±?2.31?mg/kg, p?<?0.001) and increased the threshold for the forelimb tonic extension (102.6?±?5.39 versus 71.82?±?7.82?mg/kg, p?<?0.01) seizure induced by PTZ compared with the control group.

Discussion and conclusion: Based on the results, the hydroethanolic extract of ginger has anticonvulsant effects, possibly through an interaction with inhibitory and excitatory systems, antioxidant mechanisms, and oxidative stress inhibition.     

Magnesium sulfate treatment against sarin poisoning: dissociation between overt convulsions and recorded cortical seizure activity

Sarin, a potent organophosphate cholinesterase inhibitor, induces an array of toxic effects including convulsions. Many antidotal treatments contain anticonvulsants to block seizure activity and the ensuing brain damage. Magnesium sulfate (MGS) is used to suppress eclamptic seizures in pregnant women with hypertension and was shown to block kainate-induced convulsions. Magnesium sulfate was evaluated herein as an anticonvulsant against sarin poisoning and its efficacy was compared with the potent anticonvulsants midazolam (MDZ) and caramiphen (CRM). Rats were exposed to a convulsant dose of sarin (96 μg/kg, im) and 1 min later treated with the oxime TMB4 and atropine to increase survival. Five minutes after initiation of convulsions, MGS, CRM, or MDZ were administered. Attenuation of tonic–clonic convulsions was observed following all these treatments. However, radio-telemetric electro-corticography (ECoG) monitoring demonstrated sustained seizure activity in MGS-injected animals while this activity was completely blocked by MDZ and CRM. This disrupted brain activity was associated with marked increase in brain translocator protein levels, a marker for brain damage, measured 1 week following exposure. Additionally, histopathological analyses of MGS-treated group showed typical sarin-induced brain injury excluding the hippocampus that was partially protected. Our results clearly show that MGS demonstrated misleading features as an anticonvulsant against sarin-induced seizures. This stems from the dissociation observed between overt convulsions and seizure activity. Thus, the presence or absence of motor convulsions may be an unreliable indicator in the assessment of clinical status and in directing adequate antidotal treatments following exposure to nerve agents in battle field or terror attacks.     

Anticonvulsant effects of bis-1,4-dihydropyridines and the probable role of L-type calcium channels suggested by docking simulations

The influx/efflux of calcium (Ca²⁺) ions through channels in cellular membranes plays a pivotal role in many physiological and physiopathological processes. Among these are those involved in the physiopathology of epileptic seizures. Hence, the control of permeability of ions through these channels is considered a strategy for the development of anticonvulsant drugs. According to the previous reports, dihydropyridine derivatives have proven to be Ca²⁺ channel blockers and have anticonvulsive properties, presumably by means of their action on L-type Ca²⁺ channels (LCCs). The aim of the present study was to determine the anticonvulsant effects of four bis-1,4-dihydropyridines (bis-DHPs) in male CF1 mice (25–30 g bw) using two experimental models: maximal electroshock (MES, which induces convulsions with an alternating current of 60 Hz) and pentylenetetrazole administration (PTZ, 90 mg/kg administered i.p.). Additionally, the binding mode was explored with a docking study on a 3-D model of an LCC. The four bis-DHPs herein tested showed a protective effect in relation to the number of convulsions induced by MES, the recovery time after a convulsion, and the duration of the tonic phase. However, only bis-DHPs 01–03 reduced the duration of the clonic phase, and these compounds also produced a significant protective effect against the convulsions induced by PTZ administration. This effect may be related to the interaction of bis-DHPs with a cluster of aromatic residues (Tyr1152, Tyr1463, and Phe1159) involved in blocking calcium flow, as suggested by docking studies.     

Comparative profiles of sodium valproate and ethosuximide on electro-behavioural correlates in gamma-hydroxybutyrate and pentylenetetrazol induced absence seizures in rats

Sodium valproate (VPA) and ethosuximide (ESM) were compared on behavioural and EEG changes in gamma-hydroxybutyrate (GHB) and pentylenetetrazole (PTZ) rat models of Absence Seizures (AS). Both GHB, 100 mg/kg i.p. and PTZ, 20 mg/kg i.p., produced repetitive episodes of staring and immobility with concomitant 6 to 9 Hz spike and wave discharges (SWDs) in the EEG. The parameters used for drug evaluation were the number and duration of SWDs/hour. Though the number of SWDs/hour produced by GHB and PTZ were not significantly different, the duration of SWDs was significantly longer in GHB treated rats (P < 0.001) VPA and ESM, at 200 mg/kg i.p., reduced SWD number and duration in GHB pretreated rats, whereas ESM, 50 mg/kg i.p., was four times more effective than VPA, 200 mg/kg i.p., in the PTZ model. Phenytoin (PHY) 20 and Carbamazepine (CBZ) 10 mg/kg i.p., worsened AS, a feature which has also been reported clinically. Both rat models of experimental AS can be used to defect potential anti-absence activity in new chemical entities.