Biomedical subjects

S J Czuczwar

Publications and source records attributed to S J Czuczwar.

At least 19 recordsLinked to original sources

PubMed1992

Anticonvulsant activity of carbamazepine and diphenylhydantoin against maximal electroshock in mice chronically treated with aminophylline.

The anticonvulsant activities of both carbamazepine and diphenylhydantoin alone (after a single intraperitoneal administration) or combined with aminophylline were studied against maximal electroshock-induced convulsions in male mice. Aminophylline (injected acutely at 50 mg/kg) significantly increased the ED50 values of both antiepileptics. Given for three days, aminophylline (50 mg/kg, twice daily) still impaired the potency of both antiepileptics and after chronic aminophylline administration a further decrease in the protective activity of carbamazepine and diphenylhydantoin was found. Specifically, after 14 days of aminophylline treatment, ED50s for carbamazepine and diphenylhydantoin were 26 and 19 mg/kg, respectively. These ED50s were significantly elevated compared to values determined after acute aminophylline treatment (21.2 and 14.9 mg/kg, respectively). Plasma levels of both antiepileptics were unaffected by chronic aminophylline which seems to exclude a pharmacokinetic interaction in terms of total plasma levels at least. The present results clearly indicate that the aminophylline-induced impairment of the anticonvulsant activity of carbamazepine and diphenylhydantoin is enhanced over time. This may render aminophylline a hazardous drug to epileptic patients who are prescribed this smooth muscle relaxant.

Aminophylline↗

PubMed1992

Influence of flunarizine, nicardipine and nimodipine on the anticonvulsant activity of different antiepileptic drugs in mice.

Only flunarizine (40 mg/kg, i.p.) significantly raised the threshold for electroconvulsions in mice (ear-clip electrodes, 0.2 sec stimulus duration, tonic hindlimb extension as an endpoint), whilst nicardipine and nimodipine (up to 80 mg/kg) was ineffective in this respect. Further, flunarizine (10 and 20 mg/kg) potentiated the efficacy of carbamazepine and valproate against maximum electroshock (50 mA)-induced seizures and, in the dose of 20 mg/kg, enhanced that of diphenylhydantoin. In addition, this calcium channel inhibitor was without influence upon the total levels of these antiepileptics in plasma. Nicardipine (5 and 10 mg/kg) and nimodipine (10 and 20 mg/kg) increased the protective potential of carbamazepine and nimodipine (20 mg/kg) also decreased the ED50 of diphenylhydantoin against maximum electroshock. However, nicardipine distinctly increased the level of carbamazepine in plasma, whilst nimodipine did not affect the level of both antiepileptics in plasma. The combined treatment of calcium channel inhibitors and antiepileptic drugs, providing a 50% protection against maximum electroshock, did not significantly change the motor performance of mice in the chimney test, when compared with antiepileptic drugs, given alone at their ED50s, against maximum electroshock-induced convulsions. The present results give further support to the idea of the combined use of some calcium channel inhibitors and antiepileptic drugs in the treatment of human epilepsy.

Animals↗

PubMed1992

Antiparkinsonian drugs memantine and trihexyphenidyl potentiate the anticonvulsant activity of valproate against maximal electroshock-induced seizures.

Memantine increased the threshold for electroconvulsions, when administered at 1.0-6.0 mg/kg (i.p.) and given in subthreshold doses of 0.0156, 0.0625, 0.125 and 0.5 mg/kg (i.p.) potentiated the protective efficacy of valproate, against maximal electroshock (50 mA)-induced seizures in mice, lowering the ED50 from 235 to 197, 172, 164 and 130 mg/kg, respectively. Trihexyphenidyl, applied in doses of 30 and 50 mg/kg (i.p.), did not influence the electroconvulsive threshold per se but when combined with valproate, strongly enhanced its anticonvulsant activity against maximal electroshock-induced seizures lowering the ED50 from 206 to 103 and 46 mg/kg, respectively. The chimney test and retention testing in mice revealed that administration of memantine at 0.5 mg/kg (i.p.) or trihexyphenidyl at 30 mg/kg (i.p.) together with valproate in doses of 130 or 103 mg/kg (i.p.), respectively, resulted in motor impairment and caused impairment of long-term memory, similar to the effects of valproate alone, when applied at its ED50 against maximal electroshock. Neither memantine nor trihexyphenidyl altered the total level of valproate in plasma. It may be concluded that the potentiation of the anticonvulsant activity of valproate, by memantine and trihexyphenidyl, is not associated with a pharmacokinetic interaction.

Animals↗

PubMed1991

Influence of MK-801 on the anticonvulsant activity of antiepileptics.

MK-801 (a potent non-competitive antagonist of N-methyl-D-aspartic acid-mediated events) in subcutaneous doses of 0.1 and 0.2 mg/kg increased the threshold for electroconvulsions and in doses of 0.0031 and 0.0125 mg/kg enhanced the protective activity of valproate against maximal electroshock-induced convulsions in mice. Valproate-induced side-effects (evaluated by means of dark-avoidance acquisition and retention testing and the chimney test) at its ED50 against maximal electroshock (i.e. 268 mg/kg) were pronounced whereas they were absent in the case of a combined treatment with MK-801 (0.0125 mg/kg) and valproate (91 mg/kg). This treatment provided 50% protection against maximal electroshock-induced seizures. Moreover, MK-801 (0.0125 and 0.05 mg/kg) potentiated the anticonvulsant action of phenobarbital, reducing phenobarbital-induced motor impairment totally at 0.05 mg/kg, but did not influence the protection offered by carbamazepine and diphenylhydantoin at 0.05 mg/kg. The N-methyl-D-aspartic acid antagonist did not affect the total plasma levels of either valproate or phenobarbital (as measured by immunofluorescence), so a pharmacokinetic interaction, in terms of total plasma levels at least, is unlikely to be involved in the observed effects. The finding that the combined treatment of MK-801 with valproate or phenobarbital, apart from the distinct potentiation of their anticonvulsant activities, is devoid of side-effects should be carefully considered.

Animals↗

PubMed1991

Influence of antidepressant drugs on seizure susceptibility and the anticonvulsant activity of valproate in mice.

The tricyclic antidepressants, amitriptyline (20-30 mg/kg, i.p.) and imipramine (30-40 mg/kg), provided a significant protection against electro-convulsions (12 mA, 0.2 s stimulus duration) but desipramine (up to 40 mg/kg) remained ineffective. On the other hand, all drugs, amitriptyline (10 mg/kg), desipramine (20 mg/kg), and imipramine (20 mg/kg) distinctly potentiated the protective efficacy of valproate against maximal electroshock, reducing its ED 50 values from 255 mg/kg to 150, 135, and 128 mg/kg, respectively. In one case the plasma valproate level was measured and it was evident that desipramine (20 mg/kg) did not affect the plasma level of this antiepileptic.

Amitriptyline↗

PubMed1991

Influence of CGS 15943 A (a nonxanthine adenosine antagonist) on the protection offered by a variety of antiepileptic drugs against maximal electroshock-induced seizures in mice.

CGS 15943 A (a nonxanthine adenosine antagonist) was studied on the protective efficacy of carbamazepine (60 min prior to the convulsive test), diazepam (60 min), diphenylhydantoin (120 min), phenobarbital (120 min), and valproate (30 min) against maximal electroshock-induced convulsions in mice. Moreover, the influence of the adenosine antagonist on 2-chloroadenosine (1 mg/kg, 20 min prior to the test)- and valproate (250 mg/kg, 30 min)-induced inhibitions of locomotor activity was also studied. CGS 15943 A (1 mg/kg) was given 15 min before both tests and all the drugs were administered i.p.. The adenosine antagonist (1 mg/kg) remained without influence upon the protective activity of all studied antiepileptics, reflected by their respective ED50 values against maximal electroshock. However, both 2-chloroadenosine and valproate-induced inhibitions of locomotor activity were attenuated by CGS 15943 A, which alone did not affect this parameter. However, CGS 15943 A (5 mg/kg) diminished the protection offered by diphenylhydantoin, increasing its ED50 value from 13 to 16 mg/kg. It may be concluded that the protection provided by common antiepileptic drugs against electroconvulsions seems independent of adenosine-mediated inhibition. In the case of diphenylhydantoin, one may suggest the involvement of purinergic transmission in the final anticonvulsant effect.

Adenosine↗

PubMed1990

Effects of calcium channel inhibitors upon the efficacy of common antiepileptic drugs.

Diltiazem and nifedipine (both 1.25 mg/kg) markedly potentiated the protective action of carbamazepine and diphenylhydantoin against maximal electroshock-induced seizures in mice. These calcium channel inhibitors retained their activity at lower doses. Diltiazem and nifedipine (2.5 mg/kg) also moderately potentiated the efficacy of phenobarbital and valproate. Verapamil (up to 10 mg/kg) was not effective against the action carbamazepine, diphenylhydantoin, phenobarbital, and valproate. None of the calcium channel inhibitors used (up to 40 mg/kg) influenced aminophylline-induced convulsions and mortality. Moreover, the anti-aminophylline activity of valproate and phenobarbital was not potentiated by the calcium channel inhibitors in doses up to 10 mg/kg. Further, combination of carbamazepine, ethosuximide, and trimethadione with the calcium channel inhibitors (up to 10 mg/kg) did not offer any protection against aminophylline-induced convulsions. It can be concluded that calcium channel inhibitors enhance the protective efficacy of some antiepileptics against electroconvulsions. A pharmacokinetic interaction does not seem to be responsible for this effect.

Aminophylline↗

PubMed1990

Differential effects of agents enhancing purinergic transmission upon the antielectroshock efficacy of carbamazepine, diphenylhydantoin, diazepam, phenobarbital, and valproate in mice.

L-phenylisopropyladenosine (L-PIA; a preferential A1 adenosine agonist-0.05 mg/kg) offered no protection against electroconvulsions in mice but potentiated the anticonvulsant action of diazepam and valproate against maximal electroshock-induced seizures, decreasing the respective ED50 values from 9.5 to 4.0 mg/kg and from 250 to 185 mg/kg. However, it remained without effect on the protective activity of phenobarbital, carbamazepine and diphenylhydantoin. 5'-N-ethylcarboxamidoadenosine (NECA; a preferential A2 adenosine agonist-0.5 mg/kg) potentiated the efficacy of valproate. On the other hand, NECA (1 mg/kg) diminished the anticonvulsant action of phenobarbital (ED50 was elevated from 16.5 to 20.5 mg/kg), possessing no effect upon the protective action of carbamazepine. In addition, papaverine (20 mg/kg) significantly enhanced the protective efficacy of valproate and up to 40 mg/kg remained without influence upon the protective action of carbamazepine. However, papaverine (20 and 40 mg/kg) inhibited the anticonvulsive potential of phenobarbital. In the light of the results obtained A1 and A2 adenosine receptor-mediated events seem to possess different influences upon the protective effects of antiepileptic drugs.

Adenosine↗

PubMed1990

Influence of calcium channel inhibitors upon the anticonvulsant efficacy of common antiepileptics against pentylenetetrazol-induced convulsions in mice.

Among three calcium channel inhibitors studied, nifedipine (20 mg/kg) moderately inhibited pentylenetetrazol (115 mg/kg, s.c.)-induced convulsions, whilst diltiazem (up to 20 mg/kg) and verapamil (up to 20 mg/kg) were without effect. The combinations of nifedipine (10 and 20 mg/kg) with valproate (100 mg/kg) or phenobarbital (6.25 mg/kg) resulted in significant protection against pentylenetetrazol-induced seizures. Combined treatment of nifedipine (5-20 mg/kg) with ethosuximide (100 mg/kg) also provided a clearcut anticonvulsant action. The antiepileptic drugs alone, in the above doses, were ineffective. The combination of diltiazem (10-20 mg/kg) and ethosuximide (100 mg/kg) produced protection against pentylenetetrazol, comparable to that of ethosuximide (200 mg/kg) alone. No pharmacokinetic interactions were found in the case of ethosuximide, whilst nifedipine (10 mg/kg) increased the levels of phenobarbital and valproate in plasma. The combination of diltiazem with the remaining antiepileptics were ineffective. Verapamil (up to 20 mg/kg) was without effect upon the action of the antiepileptic drugs tested. Finally, none of the calcium channel inhibitors studied influenced the action of diazepam (0.2 mg/kg). It may be concluded that combinations of ethosuximide, with either nifedipine or diltiazem, may be promising for the treatment of absence epilepsy.

Animals↗

PubMed1989

Effect of aminophylline upon the protective activity of common antiepileptic drugs and their plasma levels in mice.

Aminophylline (50 mg/kg) decreased the protective efficacy of carbamazepine (20 mg/kg), diphenylhydantoin (8-12 mg/kg), phenobarbital (20 and 25 mg/kg), and valproate (250 and 300 mg/kg) against electroconvulsions in mice. On the other hand, aminophylline (5 mg/kg) was devoid of such activity. Plasma levels of antiepileptic drugs were measured with the help of the Abbott TDx analyzer and after administration of carbamazepine (20 mg/kg), diphenylhydantoin (10 mg/kg), phenobarbital (25 mg/kg), and valproate (250 mg/kg) were as follows: 8.61, 6.48, 24.3 and 329 micrograms/ml, respectively. Aminophylline (50 mg/kg) remained without any significant influence upon these plasma levels. This may lead to the conclusion that aminophylline-induced reversal of antiepileptic drug activity is not dependent upon a pharmacokinetic mechanism and probably occurs at the neuronal level.

Aminophylline↗

PubMed1987

Inhibition of aminophylline-induced convulsions in mice by antiepileptic drugs and other agents.

Common antiepileptic drugs and agents affecting different neurotransmitter systems were studied against aminophylline (280 mg/kg i.p.)-induced convulsions in mice. All drugs and agents were administered i.p. Diazepam and phenobarbital antagonized the whole seizure pattern and the respective ED50 values for the clonic phase were 3.5 and 62 mg/kg. Valproate at 500 mg/kg protected fewer than 50% of mice against the clonic phase. The remaining antiepileptics (acetazolamide, up to 1,000 mg/kg; carbamazepine and diphenylhydantoin, up to 50 mg/kg; ethosuximide, 500 mg/kg and trimethadione, 400 mg/kg) were totally ineffective in this respect. Propranolol (up to 20 mg/kg), baclofen (20 mg/kg), gamma-hydroxybutyric acid (300 mg/kg), aminooxyacetic acid (20 mg/kg), clonidine (up to 0.2 mg/kg), ketamine (30 mg/kg), atropine (20 mg/kg), papaverine (50 mg/kg) and L-phenylisopropyladenosine (2 mg/kg) did not affect the clonic phase either. Only antagonists of N-methyl-D-aspartic acid excitation, 2-amino-5-phosphonopentanoic acid and 2-amino-7-phosphonoheptanoic acid afforded protection against aminophylline-induced clonic seizure activity. The results show that aminophylline convulsions are relatively resistant to antiepileptic drugs and suggest that antagonists of excitatory transmission are potential antiaminophylline drugs.

2-Amino-5-phosphonovalerate↗

PubMed1987

Effect of microinjections of gamma-vinyl GABA or isoniazid into substantia nigra on the development of amygdala kindling in rats.

The effects of bilateral microinjections into the substantia nigra pars reticulata of gamma-vinyl GABA and isoniazid, i.e., drugs which manipulate GABA-mediated inhibition, were studied on kindling and kindled seizures induced by daily stimulation of the amygdala in rats. In comparison to saline-injected controls, both gamma-vinyl GABA (5 or 10 micrograms) and isoniazid (150 micrograms/side) retarded the rate of kindling development as measured by the increase in seizure severity. The duration of the motor seizures and the duration of afterdischarges recorded from the stimulated amygdala were less sensitive to the anticonvulsant effect of both drugs, although significant reductions were measured during kindling acquisition. In fully kindled rats, only gamma-vinyl GABA exerted significant effects on kindled seizures, whereas isoniazid was ineffective after intranigral injection, suggesting that the kindling acquisition period is more sensitive to alterations in GABA-mediated transmission than the fully kindled state. The data provide further evidence that the substantia nigra is involved in the development and expression of kindled seizures.

4-Aminobutyrate Transaminase↗

PubMed1987

Effects of aminophylline and enprofylline on the protective activity of phenobarbital against amygdala-kindled seizures in rats.

Two xanthine derivatives, aminophylline and enprofylline, were tested on the protective activity of phenobarbital, 20 mg/kg i.p. (60 min before the test) against amygdala-kindled seizures in female rats. Enprofylline, 27.8 mg/kg i.p. (0.143 mmol/kg) 30 min, and aminophylline, 10 mg/kg i.p. (0.043 mmol/kg) 30 min, did not modify any kindling parameter. Aminophylline, 30 mg/kg (0.143 mmol of theophylline/kg), considerably increased seizure and afterdischarge durations. Aminophylline, 30 mg/kg, abolished the effect of phenobarbital (20 mg/kg) upon these seizure parameters. Both values reached the level observed in animals treated with aminophylline alone. Aminophylline, 10 mg/kg, only moderately increased afterdischarge duration in phenobarbital (20 mg/kg)-treated group. Enprofylline, 27.8 mg/kg, was devoid of any action upon the protection offered by phenobarbital in this model of epilepsy.

Aminophylline↗

PubMed1987

Comparison of drugs with different selectivity for central alpha 1-and alpha 2-adrenoceptors in animal models of epilepsy.

The effects of two drugs which differ in selectivity for central alpha 1- and alpha 2-adrenoceptors were compared in different animal models of epilepsy. Clonidine, a selective alpha2-adrenoceptor agonist, up to 0.5 mg/kg i.p. was inactive against electroconvulsions in mice, but decreased the threshold for electroconvulsions in rats, whereas it exerted anticonvulsant effects against seizures induced by pentylenetetrazol in mice, amygdala kindling in rats and air blast stimulation in seizure-sensitive gerbils. In gerbils, the anticonvulsant effect of clonidine was counteracted by pretreatment with the alpha2-antagonist yohimbine (2.5 mg/kg i.p.), but not by the alpha 1-selective antagonist corynanthine (10 mg/kg i.p.). St 587 [2-(2-chloro-5-trifluoromethylphenylimino)imidazolidine], a highly alpha 1-selective agonist which easily penetrates into the brain, up to 20 mg/kg i.p. exerted no effects on the thresholds for electroshock and pentylenetetrazol-induced seizures in mice and rats, but displayed significant anticonvulsant efficacy in kindled rats and epileptic gerbils. In gerbils, corynanthine but not yohimbine antagonized the anticonvulsant effect of St 587. The data indicate that, at least in certain seizure models, anticonvulsant effects can be reached via stimulation of both alpha 1- and alpha 2-adrenoceptors.

Animals↗

PubMed1986

Seizures produced by pilocarpine: neuropathological sequelae and activity of glutamate decarboxylase in the rat forebrain.

Morphological analysis of brains from rats receiving a convulsant dose of the muscarinic cholinergic agonist, pilocarpine hydrochloride (380 mg/kg), revealed a widespread damage to the forebrain as assessed by light microscopy 5-7 days after seizures. The substantia nigra, olfactory cortex, amygdala, hippocampus, septum, temporal cortex and thalamus underwent prominent morphological injury and cell loss. A concurrent assessment of the activity of L-glutamate decarboxylase (GAD), the gamma-aminobutyrate (GABA) synthesizing enzyme, demonstrated marked deficits in GAD activity in the brain regions undergoing morphological insult. Diazepam, 10 mg/kg, and scopolamine hydrochloride, 10 mg/kg, administered 30 min prior to the injection of pilocarpine, 380 mg/kg, prevented acute behavioral and electrographic, and long-term morphological and biochemical sequelae of seizures. These findings suggest that the muscarinic antagonist, scopolamine, and the anticonvulsant benzodiazepine, diazepam, may aid in preventing extensive brain damage related to pathological muscarinic cholinergic overactivity. The similarity of the topography of the damage and deficits in the GAD activity in brains of rats treated with pilocarpine indicates that GABAergic neurons are lost in the subregions of the brain preferentially sensitive to the convulsant action of pilocarpine.

Animals↗

PubMed1986

Studies on the involvement of dopamine D-1 and D-2 receptors in the anticonvulsant effect of dopamine agonists in various rodent models of epilepsy.

Dopamine agonists with different selectivity for dopamine D-1 and D-2 receptors in the brain were tested for their effects: on thresholds for maximal electroshock seizures in mice and rats and for pentylenetetrazol-induced clonic seizures in mice; on seizures induced by air blast stimulation in gerbils, and on seizures induced by amygdala-kindling in rats. The mixed D-1/D-2 agonist apomorphine exerted anticonvulsant effects in all models except kindling. In gerbils and mice, the anticonvulsant action of apomorphine could be antagonized by the D-2 selective dopamine antagonist sulpiride. When injected alone, sulpiride exerted no significant effect on seizure activity. The preferential D-2 receptor agonists lisuride and (+)-PHNO [+)-4-propyl-9-hydroxynaphthoxazine) differed in their profile of action. Both compounds displayed anticonvulsant efficacy in gerbils, while only lisuride proved capable of reducing kindled seizure severity. (+)-PHNO increased the threshold for electroconvulsions in mice while lisuride was ineffective in this respect or even decreased the threshold. The reverse was obtained in regard to electroshock seizures in rats. The threshold for seizures induced by pentylenetetrazol in mice was increased significantly by lisuride but not by (+)-PHNO. The selective dopamine D-1 receptor agonist SKF 38393-A exerted no anticonvulsant effect in any seizure test except a moderate increase of the electroconvulsive threshold in mice. In contrast, the dopamine precursor L-DOPA (injected after pretreatment with carbidopa) proved capable of reducing seizure activity in all models. In mice, the increase in the threshold for maximal electroshock seizures induced by L-DOPA was significantly reduced by sulpiride, which also attenuated the anticonvulsant effect of L-DOPA in gerbils. Collectively, the data indicate that dopamine D-2 receptors mediate the anticonvulsant effect of dopamine agonist and, at least in part, of L-DOPA whereas D-1 receptors seem not to be involved.

Animals↗

PubMed1986

Anticonvulsant action of 1,3-dimethyl-5-aminoadamantane. Pharmacological studies in rodents and baboon, Papio papio.

The anticonvulsant actions of memantine (1,3-dimethyl-5-aminoadamantane) have been evaluated in mice (seizures induced by maximal electroshock, pentylenetetrazol, bicuculline, picrotoxin, 3-mercaptopropionic acid and N-methyl-D,L-aspartic acid) and in photosensitive baboons, Papio Papio (clonic responses to intermittent photic stimulation). Memantine, 5-20 mg/kg, raised the threshold for electroconvulsions and protected mice against the tonic hind limb extension in pentylenetetrazol-, bicuculline-, picrotoxin- and 3-mercaptopropionic acid-induced seizures, but was ineffective against the clonic phase of chemically-induced seizures. In the baboons, no protection against photomyoclonic responses was observed within 5 h after the intravenous administration of memantine, 1-9 mg/kg. Amantadine, 100 mg/kg, reduced the protective effect of memantine against electroconvulsions. Apomorphine, haloperidol, pimozide, spiroperidol and bicuculline did not modify the anticonvulsant activity of memantine in electroconvulsions. These studies demonstrate an anticonvulsant action of memantine in rodents and suggest that dopaminergic mechanisms do not contribute to its mechanism of action.

Amantadine↗

PubMed1986

Is amygdala kindling in rats a model for drug-resistant partial epilepsy?

Amygdala-kindled female rats were used to compare the effects of seven antiepileptic drugs that are clinically used for treatment of partial epilepsy with complex symptomatology, on generalized seizures, focal seizures, or electrographic seizure activity at the focus. As a second approach of drug evaluation, drug effects on mean latency, severity, and duration of the seizures were determined. Anticonvulsant potencies obtained were compared with those determined in the maximal electroshock seizure test in female rats. Phenobarbital, phenytoin, carbamazepine, valproic acid, diazepam, clonazepam, but not primidone dose-dependently suppressed generalized motor seizures in kindled rats; however, except for the benzodiazepines, ED50S were substantially higher than those determined in the maximal electroshock seizure test. Compared with their effect on generalized motor seizures, all drugs were much less potent in blocking focal seizures and afterdischarges recorded from the amygdala. The data suggest that with respect to behavioral and pharmacologic characteristics of the amygdala kindling model, fully kindled rats may be a useful model for drug-resistant complex partial seizures with secondary generalization. Results of experiments with novel inhibitors of GABA uptake, which were inactive in the maximal electroshock seizure test but highly potent against kindled seizures, suggest that such drugs might be more effective than current antiepileptic drugs for treatment of partial epilepsy.

Animals↗