Pentylenetetrazole Test Research Articles

4-Sulphamoylphenyl semicarbazones with anticonvulsant activity

A series of 4-sulphamoylphenyl semicarbazone derivatives were prepared starting from sulphanilamide and screened for anticonvulsant activity. The results indicated that greater protection was obtained in the maximal electroshock screen (MES) and subcutaneous strychnine (scSTY) than the subcutaneous pentylenetetrazole (scPTZ) tests. All the compounds showed low neurotoxicity when compared to the clinically used drugs. Compounds with substituted acetophenone ( 8-11) showed good activity in the rat oral MES screen. Seven compounds ( 6, 8-10, 12, 14 and 15) exhibited anticonvulsant activity greater than sodium valproate. Among the new derivatives evaluated, compound 10 emerged as the most active compound as indicated by its protection in the MES and scSTY screens and with low neurotoxicity. Seven compounds possessed sedative-hypnotic activity.

P2-077 Expression of human FE65 in APP transgenic mice is associated with a reduction in β-amyloid load

Traumatic brain injury (TBI) causes 10–20% of acquired epilepsy in humans, resulting in an ictogenic region that is often located in the cerebral cortex. The thalamus provides heavy projections to the cortex and the activity of thalamocortical pathways is controlled by GABAergic afferents from the reticular nucleus of the thalamus (RT). As rats with TBI induced by lateral fluid-percussion injury (FPI) undergo epileptogenesis, we hypothesized that damage to the parvalbumin (PARV)-immunoreactive (ir) neurons in the RT is associated with seizure susceptibility after lateral FPI. To address this hypothesis, adult Sprague–Dawley rats (n = 13) were injured with lateral FPI. At 6 months post-TBI, each animal underwent a pentylenetetrazol (PTZ) seizure susceptibility test and 2 weeks of continuous video-electroencephalography (EEG) monitoring for detection of the occurrence of spontaneous seizures. Thereafter, the brain was processed for PARV immunohistochemistry. We (a) estimated the total number of PARV-ir neurons in the RT using unbiased stereology, (b) measured the volume of the ventroposteromedial (VPM) and ventroposterolateral (VPL) nuclei of the thalamus, which receive PARV-ir inputs from the RT and project to the perilesional cortex, (c) quantified the density of PARV-ir terminals in the VPM–VPL, and (d) studied the expression of GABAA receptor subunits in a separate group of rats using laser-dissection of the thalamus followed by Real-Time polymerase chain reaction (RT-PCR) array studies. At 6 months post-TBI, only 64% of PARV-ir neurons were remaining in the RT ipsilaterally (p < 0.001 as compared to controls) and 84% contralaterally (p < 0.05). Accordingly, the volume of the ipsilateral RT was 58% of that in controls ipsilaterally (p < 0.001) and 90% contralaterally (p > 0.05). Also, the volume of the VPM–VPL was only 51% of that in controls ipsilaterally (p < 0.001) and 91% contralaterally (p < 0.05). The density of PARV-ir axonal labeling was remarkably increased in the lateral aspects of the VPM and VPL (both p < 0.001). Expression of the ε- and θ-subunits of the GABAA receptor was down-regulated (0.152, p < 0.01 and 0.302, p < 0.05, respectively), which could relate to the inclusion of the hypothalamus into the tissue analyzed with RT-PCR arrays. In controls, the lower the number of PARV-ir neurons in the RT, the higher the seizure susceptibility in the PTZ test. Rats with TBI showed seizure susceptibility comparable to that in controls with the lowest number of PARV-ir neurons in the RT. Our data show that the RT and VPM–VPL undergo remarkable degeneration after lateral-FPI which results in reorganization of PARV-ir terminals in the VPM–VPL. The contribution of RT damage to seizure susceptibility and post-traumatic epileptogenesis deserves further studies.

Synthesis and neurotropic activity of silyl propargyl alcohols and sulfides

AbstractNew silicon derivatives of hetaryl propargyl sulfides and propargyl alcohols were synthesized using phase‐transfer catalytic and organometallic methods. These compounds were tested for acute toxicity and neurotropic activity in the pentylenetetrazole test, and for phenamine hypothermia, phenamine hyperactivity and passive avoidance response tests. We have found that the silyl propargyl alcohols and sulfides are low toxicity compounds, the LD50 being 700–1300 mg kg−1. In the PAR test, the synthesized compounds exerted some memory‐improving activity. For di‐1‐(3‐methyl‐3‐hydroxybutyn‐1‐yl)methyl(3‐iodopropyl)silane (16) the effect was statistically significant and amounted to 250% of the control level. In the pentylenetetrazole test, all compounds possessed anticonvulsant activity, the most active compounds being 3‐(benzoxazolylthio)‐1‐propynyl(trimethyl)silane (6) and di‐[2‐(1‐hydroxycyclohexyl)ethynyl]methyl(3‐iodopropyl)silane (17). The phenamine‐induced hyperactivity was significantly elevated after treatment with (3‐trimethylsilyl‐2‐propynyl)thiobenzene (1) or di‐[1‐(3‐methyl‐3‐hydroxybutyn‐1‐yl)diphenylsilane (12). Our data show that these silicon derivatives of hetaryl propargyl sulfides and propargyl alcohols possess certain memory improving and anticonvulsant activity that should be studied in detail to evaluate the receptor systems involved. Copyright © 2004 John Wiley &amp; Sons, Ltd.

Testosterone modulation of seizure susceptibility is mediated by neurosteroids 3α-androstanediol and 17β-estradiol

Testosterone modulates seizure susceptibility in animals and humans, but the underlying mechanisms are obscure. Here, testosterone modulation of seizure susceptibility is hypothesized to occur through its conversion to neurosteroids with “anticonvulsant” and “proconvulsant” actions, and hence the net effect of testosterone on neural excitability and seizure activity depends on the levels of distinct testosterone metabolites. Testosterone undergoes metabolism to neurosteroids via two distinct pathways. Aromatization of the A-ring converts testosterone into 17β-estradiol. Reduction of testosterone by 5α-reductase generates 5α-dihydrotestosterone (DHT), which is then converted to 3α-androstanediol (3α-Diol), a powerful GABA A receptor-modulating neurosteroid with anticonvulsant properties. Systemic doses of testosterone decreased seizure threshold in rats and increased the incidence and severity of pentylenetetrazol (PTZ)-induced seizures in mice. These proconvulsant effects of testosterone were associated with increases in plasma 17β-estradiol and 3α-Diol concentrations. Pretreatment with letrozole, an aromatase inhibitor that blocks the conversion of testosterone to 17β-estradiol, significantly inhibited testosterone-induced exacerbation of seizures. The 5α-reductase inhibitor finasteride significantly reduced 3α-Diol levels and also blocked letrozole's ability to inhibit the proconvulsant effects of testosterone. The 5α-reduced metabolites of testosterone, DHT and 3α-Diol, had powerful anticonvulsant activity in the PTZ test. Letrozole or finasteride had no effect on seizure protection by DHT and 3α-Diol, but indomethacin partially reversed DHT actions. 3α-Diol but not 3β-androstanediol, a GABA A receptor-inactive stereoisomer, suppressed 4-aminopyridine-induced spontaneous epileptiform bursting in rat hippocampal slices. Thus, testosterone-derived neurosteroids 3α-Diol and 17β-estradiol could contribute to the net cellular actions of testosterone on neural excitability and seizure susceptibility.

Evaluation of anticonvulsant activity of N-(p-aminobenzoyl)-1,2,3,4-tetrahydro-4-methylquinoline

Anticonvulsant activity of N-(p-aminobenzoyl)-1,2,3,4-tetrahydro-4-methylquinoline (NMQ), a newly synthesized ameltolide analogue, was investigated with regards to efficacy, lethality and neurotoxicity in mice. In vivo microdialysis experiments on freely moving rats were also performed in search for the possible effect of NMQ on cortical amino acid neurotransmitters. Similar to ameltolide, intraperitoneally given NMQ exerted it protective effect exclusively in maximal electroshock seizure (MES), but not in pentylenetetrazole test. However, in comparison with ameltolide which exhibited the median effective dose (ED50) of 1.08 mg/kg body weight (B.W.), NMQ was less effective (ED50 = 77.62 mg/kg B.W.). Based on the finding that no lethality was observed in mice being given NMQ up to 1000 mg/kg B.W. while the median lethality dose (LD50) of ameltolide was observed at 63 mg/kg B.W., NMQ appeared to be superior to ameltolide with regards to safety. The median neurotoxic dose (TD50) from the rotarod test was found to be 320 and 9 mg/kg B.W. for NMQ and ameltolide respectively, resulting in lower protective index (PI=TD50/ED50) of NMQ (4.12) than that of ameltolide (8.33). Thus, it could be anticipated that therapeutic dose of NMQ which seemed to be safe would produce more pronounced motor impairment than that of ameltolide. In microdialysis study on freely moving rats, it was found out that neither NMQ nor ameltolide was able to exert significant changes on the level of cortical brain amino acid neurotransmitters, namely, aspartate, glutamate, glycine and GABA. Therefore, some mechanisms other than alteration in brain amino acid neurotransmitters should underlie anticonvulsant activity exhibited by these two compounds in MES test. Furthermore, based on similarity in pharmacological screening profile of NMQ and ameltolide observed in the present study, it is suggestive that these two compounds may possess rather similar mechanism of action.

Valproic Acid‐Hydrophilic Cyclodextrin Complexes and Valproic Acid‐Solid Dispersions: Evaluation of Their Potential Pharmaceutical Use

The purpose of this study was to evaluate the potential use of two novel solid formulations of valproic acid (VPA) prepared by complexation with hydrophilic cyclodextrins (CDs) as hydroxypropyl‐β‐ and sulfobutylether‐β‐cyclodextrin and by solid dispersion (SD) in hydrophilic carriers as polyethylene glycol 6000 (PEG 6000) and polyvinylpyrrolidone K‐30 (PVP K‐30). The corresponding cyclodextrin‐based complexes were prepared by the freeze‐drying method while the solid dispersions were obtained by the solvent method. Valproic acid solubility improved by CDs complexation and solid dispersion techniques. Comparison of dissolution profiles with that of VPA sodium salt (NaVP) was made by using release parameters such as dissolution efficiency, percent of drug dissolved after 60 min, and difference and similarity factors. Based on difference and similarity factors, it can be concluded that all the VPA formulations possess dissolution profiles essentially equivalent to those of NaVP at pH 6. However, this conclusion is not confirmed by using the analysis of variance (ANOVA) approach, indicating some significant differences between some SD‐based formulations and NaVP at that pH value. Preliminary pharmacological studies in the pentylenetetrazole test in rats showed some important differences among the SD‐based formulations, NaVP, and VPA as oil/water emulsion. Some implications and limitations of the investigated formulations are discussed.

Preclinical evaluation of anticonvulsant activity of N-(p-aminobenzoyl)-1,2,3,4-tetrahydroquinoline

Anticonvulsant activity of N-(p-aminobenzoyl)-1,2,3,4- tetrahydro-quinoline (NTQ), a newly synthesized ameltolide analog, was investigated with regards to efficacy and toxicity in mice. Additionally, its effect on NMDA receptors was also performed on NR1a/NR2B expressed in Xenopus oocytes. NTQ, given intraperitoneally, was able to protect the animals in both maximal electroshock seizure and pentylenetetrazole (PTZ) tests, while ameltolide was effective only in the MES. NTQ was less potent than ameltolide, exhibiting the median effective dose (ED50) of 13.33 mg/kg body weight (B.W.), whereas the corresponding value of ameltolide was 0.96 mg/kg B.W. Ameltolide seemed to possess better safety profile than NTQ as indicated by the relative safety margin (LD50/ED50) of 65.28 for ameltolide and 44.97 for NTQ. Furthermore, based on the finding that the median neurotoxic dose (TD50) established by rotarod test was 37.28 and 7.18 mg/kg B.W. for ameltolide and NTQ respectively, ameltolide appeared to have more favorable protective index (TD50/ED50) than NTQ. Further experiment using Xenopus oocyte with NMDA receptor composing of NR1a and NR2B subunits was performed to probe for the effect of NTQ and ameltolide on NMDA-induced current. While NTQ and ameltolide did not induce any changes in current or a shift in membrane potential of oocyte, both of them significantly inhibited NMDA-induced current demonstrating the IC50 of 0.10 and 0.12 ?M respectively. Therefore, it is likely that inhibition of excitation of NMDA receptor may, at least in part, accounted for its anticonvulsant activity. In conclusion, the present study has identified NTQ as a broad-spectrum anticonvulsant agent, albeit its lower safety margin and protective index. Inhibition of NMDA receptor may partly contribute to anticonvulsant activity of these two compounds. Further structural modification of NTQ to improve its safety while preserving a broad-spectrum anticonvulsant activity should be carried out.

Pharmacodynamic interaction studies with topiramate in the pentylenetetrazol and maximal electroshock seizure models

There is emerging evidence to support the efficacy of some antiepileptic drug (AED) combinations in refractory epilepsy. Definitive clinical studies are, however, difficult to perform. Experimental seizure models can be employed to identify potentially useful combinations for subsequent clinical evaluation. We have investigated the anticonvulsant effects of topiramate (TPM) in combination with 13 other AEDs in the pentylenetetrazol (PTZ) and maximal electroshock (MES) seizure models. Single drugs and combinations were administered by intraperitoneal injection and anticonvulsant effects determined at 1-hour post-dosing. TPM was without significant effect in the PTZ test. In contrast, phenobarbital, primidone, ethosuximide, sodium valproate, felbamate and tiagabine all increased the latency to the first generalised seizure. Combinations of TPM and active adjunctive drug were universally effective. Combinations of TPM with clobazam, lamotrigine and levetiracetam were also anticonvulsant, despite the inactivity of the constituent compounds when administered alone. TPM reduced the incidence of MES-induced seizures in a dose-dependent manner, as did phenobarbital, phenytoin, primidone, carbamazepine, sodium valproate, clobazam, lamotrigine, felbamate and tiagabine. All combination treatments were similarly effective. These findings suggest that combinations of TPM with lamotrigine and levetiracetam may demonstrate anticonvulsant synergism and merit further investigation in additional model systems and with recourse to more quantitative mathematical analysis.

Right-sided vagus nerve stimulation reduces generalized seizure severity in rats as effectively as left-sided

As currently utilized, vagus nerve stimulation (VNS) is applied to the cervical trunk of the left vagus nerve to suppress seizures clinically. Demonstration that VNS can also reduce seizure severity when electrodes are placed on the right cervical vagus nerve in rats would provide empirical evidence that the antiepileptic effects of VNS are not an exclusive property of the left vagus nerve. Rats were implanted with a custom cuff electrode on either the left or right cervical vagus nerve. Two days later, continuous VNS was begun in half the rats with left-sided and half with right-sided electrodes. The remaining rats were connected to the stimulator, but did not receive VNS. After 30 s, pentylenetetrazole (PTZ) was administered systemically and seizures were rated by a blinded observer. The PTZ test was repeated two days later, with VNS administered to the previously unstimulated rats, while the others received no stimulation. VNS significantly reduced the severity of PTZ-induced seizures in rats regardless of the side of stimulation as compared to their no-VNS (control condition) seizure severity. No significant differences in efficacy existed based on the side of stimulation. These results indicate that right-sided VNS in rats is just as effective as left-sided VNS, suggesting that fibers necessary for seizure suppression are not unique to the left vagus nerve.

Anticonvulsant properties of acetone, a brain ketone elevated by the ketogenic diet.

The ketogenic diet (KD), a treatment for drug-resistant epilepsy, elevates brain acetone. Acetone has been shown to suppress experimental seizures. Whether elevation of acetone is the basis of the anticonvulsant effects of the KD and whether acetone, like the KD, antagonizes many different types of seizures, however, is unknown. This study investigated the spectrum of the anticonvulsant effects of acetone in animal seizure models. Rats were injected with acetone intraperitoneally. Dose-response effects were measured in four different models: (1) the maximal electroshock test, which models human tonic-clonic seizures; (2) the subcutaneous pentylenetetrazole test, which models human typical absence seizures; (3) the amygdala kindling test, which models human complex partial seizures with secondary generalization; and (4) the AY-9944 test, which models chronic atypical absence seizures, a component of the Lennox-Gastaut syndrome. Acetone suppressed seizures in all of the models, with the following ED(50)'s (expressed in mmol/kg): maximal electroshock, 6.6; pentylenetetrazole, 9.7; generalized kindled seizures, 13.1; focal kindled seizures, 26.5; AY-9944, 4.0. Acetone appears to have a broad spectrum of anticonvulsant effects. These effects parallel the effects of the KD. Elevation of brain acetone therefore may account for the efficacy of the KD in intractable epilepsy.

The effect of the ‘classic’ ketogenic diet on animal seizure models

Bough et al. have recently demonstrated anticonvulsant effects of the ‘classic’ ketogenic diet (KD) in the pentylenetetrazol infusion model in rats. Proconvulsant effects were seen, however, when the ‘classic’ diet was tested against maximal electroshock (MES) seizures. These differing results may reflect the fact that the two models involve different kinds of epileptogenic stimulus, or, as Bough et al. note that the two tests involve different stimulation paradigms. The pentylenetetrazol infusion paradigm is a threshold test, whereas the MES test employs a stimulus which is well above threshold. The present experiments were designed to test the effects of the ‘classic’ KD against seizures triggered in rats by both threshold and suprathreshold levels of electricity and pentylenetetrazol. The threshold tests employed were the pentylenetetrazol infusion test, and the threshold electroconvulsive shock (ECS) test. The subcutaneous pentylenetetrazol (scMET) test was also included, since it is sometimes considered to be a ‘threshold’ test. The suprathreshold tests employed were the maximal pentylenetetrazol test (MMT) and the maximal electroshock test (MES). The KD failed to suppress seizures in either of the tests involving suprathreshold stimulation (MMT and MES), although there was a significant increase in latency in the MMT test. Small but significant threshold elevations (15–20%) were seen, however, in both the pentylenetetrazol infusion test and the ECS threshold test. No seizure suppression was seen in the scMET test, which actually employs a suprasthreshold stimulus. These data indicate that the KD has significant anticonvulsant effects against both chemically and electrically triggered seizures, but that they consist of small elevations in threshold which will be seen only when threshold measures are used.

Anticonvulsant properties of the methanolic extract of Cyperus articulatus (Cyperaceae)

The methanolic extract of rhizomes of Cyperus articulatus, a plant used in traditional medicine in Africa and Latin America for many diseases, possesses anticonvulsant activity in mice. This extract protected mice against maximal electroshock (MES)- and pentylenetetrazol (PTZ)-induced seizures. It also delayed the onset of seizures induced by isonicotinic acid hydrazide and strongly antagonized N-methyl- d-aspartate-induced turning behavior. The ED 50 for protection against seizures was 306 (154–541) mg/kg intraperitoneally (i.p.) for the PTZ test and 1005 (797–1200) mg/kg i.p. for the MES test. The ED 50 of methanolic extract against N-methyl- d-aspartate-induced turning behavior was 875 (623–1123) mg/kg i.p. C. articulatus L. methanolic extract protected 54% of mice from seizures induced by strychnine at the dose of 1000 mg/kg i.p. but had no or a moderate effect only against picrotoxin- or bicuculline-induced seizures. With these effects, the rhizome of C. articulatus L. possesses anticonvulsant properties in animals that might explain its use as a traditional medicine for epilepsy in Africa.

Anticonvulsant activity of N-palmitoylethanolamide, a putative endocannabinoid, in mice.

The purpose of this study was to evaluate in mice the anticonvulsant potential of N-palmitoylethanolamide, a putative endocannabinoid that accumulates in the body during inflammatory processes. N-palmitoylethanolamide was injected intraperitoneally (i.p.) in mice and evaluated for anticonvulsant activity [in maximal electroshock seizure (MES) and chemical-induced convulsions] and for neurologic impairment (rotorod). It was compared with anandamide and with different palmitic acid analogues as well as with reference anticonvulsants (AEDs) injected under the same conditions. The MES test showed, after i.p. administration to mice, that N-palmitoy]ethanolamide had an median effective dose (ED50) value comparable to that of phenytoin (PHT; 8.9 and 9.2 mg/kg, respectively). In the subcutaneous pentylenetetrazol test and in the 3-mercaptropropionic acid test, it was effective only against tonic convulsions. N-palmitoylethanolamide was devoid of neurologic impairment < or = 250 mg/kg, yielding a high protective index. N-palmitoylethanolamide, an endogenous compound with antiinflammatory and analgesic activities, is a potent AED in mice. Its precise mechanism of action remains to be elucidated.

Anticonvulsant properties of N-salicyloyltryptamine in mice

A new tryptamine analogue, N-salicyloyltryptamine (STP), a potential central nervous system (CNS) depressant, was tested in the pentylenetetrazol (PTZ) and maximal electroshock (MES) models of epilepsy in mice. When administered concurrently, STP (100 mg/kg ip) significantly reduced the number of animals that exhibited PTZ-induced seizures and eliminated the extensor reflex of maximal electric-induced seizures test in 50% of the experimental animals. In addition, it showed protection in the PTZ test by diminishing the death rate.

Amino acid derivatives with anticonvulsant activity.

A series of benzylamides of N-alkylated, N-acylated or free nine cyclic and one linear amino acids as potential anticonvulsants have been synthesized. The structures of the obtained compounds were designed on the basis of the previously determined structure and physicochemical properties/anticvonvulsant activity relationship of the formerly synthesized compounds of this type. The obtained compounds were evaluated in mice after intraperitoneal (i.p.) administration, by maximal electroshock seizure test (MES test), subcutaneous (s.c.) pentylenetetrazol test (s.c. PTZ test) and by the rotarod neurotoxicity test (Tox test). The results were the basis for their classification into one of three classes of the Anticonvulsant Screening Project (ASP) of the Antiepileptic Drug Development Program (ADDP) of the NIH. Three selected compounds were tested quantitatively in rats after oral administration. The MES ED50, s.c. PTZ ED50, Tox TD50 were determined and their protective index (PI) values were calculated. Anticonvulsant activity of the most promising compound (15) was examined in different seizure models. The respective ED50 and PI values of this compound were as follows: against bicuculline, 73 and 1.4; against PTZ, 47 and 2.2; against strychnine, 73 and 1.4; against pilocarpine 156, and 0.7; against kainic acid (2-carboxy-4-isopropenyl-3-pyrrolidineacetic acid), 39 and 2.6; against AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid), 10 and 10.3 and against NMDA (N-methyl-D-Aspartic acid), 114 and 0.9.

Dietary fat, ketosis, and seizure resistance in rats on the ketogenic diet.

Fat is the major component of the ketogenic diet (KD), yet no studies have examined whether the type of fat used in the diet can be optimized to provide additional benefits. The purpose of the present experiments was to compare the efficiency of different fats in inducing ketosis and affording seizure resistance. The effects of KDs that incorporate lard, butter, medium-chain triglycerides (MCT), or flaxseed oil or a mixture of the latter three fats were examined in rats fed KD for up to 98 days. The maximal electroshock (MES) or pentylenetetrazole (PTZ) threshold tests were used to assess seizure susceptibility in two separate experiments. The rank order of induced ketosis was MCT > mixture > or = flaxseed oil > or = lard = butter > or = control. MES failed to reveal anticonvulsant effects, but the PTZ test indicated that up to 50% of rats fed the KD were seizure protected (p < 0.05). The measures of seizure protection, seizure incidence and score, did not correlate, however, with the level of ketosis in the range of 0. 7-5.2 mmol/L for beta-hydroxybutyrate. In the long-term study, flaxseed oil KD maintained stable ketosis throughout 98 days, whereas ketones declined with lard and butter KD to the control level. Seizure protection with the versions of the KD did not improve with the higher level of ketosis. The focus of the KD improvement, therefore, is not the achievement of higher ketosis per se but rather designing a diet that provides steady ketosis, exploits advantages of certain fats for neurological development or seizure protection via a nonketogenic mechanism, and is nutritionally balanced.

Models of Epilepsy: Electroshock and Chemical Induced Convulsions in the Mouse

AbstractEpilepsy is a disorder of the central nervous system that is characterized by seizures. This unit describes protocols for identifying and differentiating the antiseizure or anticonvulsant activity of novel test substances. Variations of two basic test methods using mice are described: blockade of electroshock‐induced convulsions (the maximal electroshock test) and blockade of chemical‐induced convulsions (the pentylenetetrazole test). This unit also describes variations of the same methods that can be used to assess potential proconvulsant activity of test substances in safety evaluation studies.

The AMPA/kainate receptor antagonist, LY 300164, increases the anticonvulsant effects of diazepam.

The aim of this study was to evaluate the influence of 7-acetyl-5-(4-aminophenyl)-8,9-dihydro-8-methyl-7H-1,3-dioxolo(4,5 H)-2,3-benzodiazepine (LY 300164), a selective non-competitive antagonist at alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)/kainate receptors, on the protection provided by diazepam against electrically- and chemically-evoked seizures in rodents. LY 300164 (2 mg/kg) was devoid of any significant action upon each seizure parameter in kindled rats (seizure severity, seizure duration, after-discharge duration). LY 300164 (5 mg/kg) exerted a significant anticonvulsive effect as regards seizure and after-discharge durations. Combined treatment with LY 300164 (2 mg/kg) and diazepam (0.3125-1.25 mg/kg) resulted in the clear-cut anticonvulsive activity. It is noteworthy that the antiseizure potency of the combined treatment (diazepam 1.25 mg/kg plus LY 300164 2 mg/kg) was comparable to that of diazepam (10-20 mg/kg) alone. The combination of diazepam (1.25 mg/kg) with LY 300164 (2 mg/kg) did not induce any significant motor impairment in the rotorod test or memory deficit in the passive-avoidance task. In contrast, diazepam alone (10-20 mg/kg) had pronounced adverse effects in kindled animals. LY 300164 (up to 2 mg/kg) did not influence the threshold for electro- and pentylenetetrazol-induced convulsions but potentiated the anticonvulsive action of diazepam in the maximal electroshock and pentylenetetrazol test in mice, the ED50s of the benzodiazepine being reduced from 13 to 8.7 and from 0.29 to 0.049 mg/kg, respectively. As shown in the passive-avoidance task, combination of LY 300164 (2 mg/kg) with diazepam (8.7 mg/ kg) produced significant motor and long-term memory impairment. Diazepam alone (at the dose equal to its ED50 against maximal electroshock) also caused motor and memory deficits in mice. Interaction at the pharmacokinetic level, at least in plasma, can be excluded, because LY 300164 (2 mg/kg) did not affect the free plasma diazepam concentration. In conclusion, LY 300164 potentiates the protective action of diazepam in some animal models of seizures. This profitable interaction may create a new approach for the treatment of drug resistant epilepsy or status epilepticus.

Synthesis and structure activity study of N‐1 substituted ( S )‐(+)‐5‐ n ‐propyl‐2‐iminohydantoins as potential anticonvulsant agents

A series of (S)-(+)-5-n-propyl-2-iminohydantoins with various N-1 substituents were synthesized and tested for anticonvulsant activity to better understand the structure–activity relationship (SAR) of 2-iminohydantoins. Compounds with N-1 phenoxycarbonyl (2), ethoxycarbonyl (6), t-butoxycarbonyl (7), propoxycarbonyl (12), and p-methyl phenoxycarbonyl (14) groups provided the most substantial anticonvulsant activity against the maximal electroshock seizure (MES) test with ED50 values in the range of 72–124 mg/kg. All of the above compounds except 7 also showed activity against the pentylenetetrazol (PTZ) test with ED50 values in the range of 65–178 mg/kg. Compound 6 provided the highest protective index (PI) value against the PTZ test, while 7 provided the highest PI value against the MES test. All significantly active compounds against the MES test (1, 2, 6, 7, 12, and 14) possessed aliphatic hydrocarbon chains of relatively small carbon length or aryl/arylalkyl groups not greater than benzyl in the carbamate moiety. Longer or larger than a benzyl group (3, 5, 8, 9, 10, and 11) or a saturated six-member ring (4) destroyed the activity. In addition, N-1 methoxycarbonyl substituted compound (13) was also devoid of significant activity. These results suggest that steric size of the substituent at N-1 oxycarbonyl sidechain in the 2-iminohydantoin molecule plays an important role in providing anticonvulsant activity, and that an alkyl substituent with a proper size further enhances PTZ anticonvulsant activity while maintaining MES activity. Drug Dev. Res. 47:17–26, 1999. © 1999 Wiley-Liss, Inc.

Anticonvulsant activities of 4-(4?-fluorophenoxy) benzaldehyde semicarbazone

A series of aryloxyaryl semicarbazones had been shown previously to possess significant anticonvulsant activity in the maximal electroshock screen in both rats and mice as well as in the subcutaneous pentylenetetrazol test in mice. One member of this series, namely 4-(4′-fluorophenoxy)benzaldehyde semicarbazone (Compound IV), was selected for detailed studies with a view to determining whether it should proceed to full-scale preclinical evaluation; these results are reported herein. After intraperitoneal injection, Compound IV afforded protection in the Frings audiogenic mouse test. In addition, it had activity in the rat corneal kindling screen after oral administration and in the rat hippocampal kindling screen after intraperitoneal administration, but it was virtually inactive in the amygdala kindling test in rats. When administered by the intravenous route to genetically susceptible epileptic chickens, Compound IV and eight analogs prevented convulsions induced by alternating strobe lights. Compound IV did not display proconvulsant properties when examined in the timed intravenous test in mice nor did this compound cause significant effects on liver weights, microsomal protein yields, and various hepatic enzymes after oral administration to rats. Intraperitoneal injection of Compound IV afforded little or no protection to mice who had received subcutaneously convulsive doses of bicuculline, picrotoxin, or strychnine. This compound did not elevate γ-aminobutyric acid levels or inhibit γ-aminobutyric acid uptake. Ion-imaging and electrophysiological experiments suggested that the mode of action of this compound could be on calcium and sodium channels. In most of these experiments, Compound IV was superior to the widely used antiepileptic drug phenytoin. Drug Dev. Res. 46:112–125, 1999. © 1999 Wiley-Liss, Inc.