Pentylenetetrazole Kindling Model Research Articles

Effects of pentylenetetrazole-induced seizures on metabolomic profiles of rat brain

Epilepsy is one of the most common neurological disorders and approximately one-third of patients with epilepsy are resistant to treatment. In order to develop our understanding of the metabolic changes occurring during seizure a metabolomic approach was employed. Using a pentylenetetrazole (PTZ) kindling model of epilepsy metabolomic analysis of brain extracts from the cerebellum, brain stem, prefrontal cortex and hippocampus was performed. Principal component analysis (PCA) of the 1H NMR derived data revealed a distinct metabolic profile for each brain region. In order to assess the changes occurring following seizure partial least square discriminant analysis (PLS-DA) models for each brain region for PTZ-kindled and control animals were constructed. For all the brain regions good predictive models were built and the discriminating metabolites were identified. Results following one injection of PTZ indicated that the changes observed in the cerebellum and hippocampus were mainly due to seizure. In the hippocampus of PTZ-kindled animals the metabolites changing included lactate, succinate, GABA, NAA, choline and taurine. Analysis of the cerebellum of PTZ-kindled animals revealed changes in lactate, myo-inositol, choline, GABA, creatine, succinate, phosphocholine and GPC. Overall, the results indicate that seizure may be associated with an increase in energy demand, altered neurotransmitter balance and an increase in neuronal loss and gliosis.

Preferential increase in the hippocampal synaptic vesicle protein 2A (SV2A) by pentylenetetrazole kindling

The present study evaluated the expressional levels of synaptic vesicle protein 2A (SV2A) and other secretary machinery proteins (i.e., soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complexes, Munc18-1, N-ethylmaleimide-sensitive factor (NSF) and soluble N-ethylmaleimide-sensitive factor attachment protein (SNAP)) in a pentylenetetrazole (PTZ) kindling model. Repeated administration of sub-convulsive PTZ (40 mg/kg, i.p.) progressively increased seizure susceptibility in mice and consistently induced clonic seizures in most animals tested at 15 days after the treatment. Western blot analysis revealed that, among the secretary machinery proteins examined, hippocampal SV2A was selectively elevated by PTZ kindling. PTZ kindling-induced SV2A expression appeared region-specific and the SV2A levels in the cerebral cortex or cerebellum were unaltered. In addition, SV2A expression by PTZ kindling was prominent in the hilar region of the dentate gyrus (DG) where GABAergic interneurons are located, but not in other hippocampal regions (e.g., the stratum lucidum of the CA3 and synaptic layers surrounding CA1 or CA3 pyramidal neurons). These findings suggest that PTZ kindling preferentially elevates SV2A expression in the hippocampus probably as a compensatory mechanism to activate the inhibitory neurotransmission.

Effects of pentylenetetrazol-induced brief convulsive seizures on spatial memory and fear memory

Previous studies have demonstrated that in the pentylenetetrazol (PTZ) kindling model, recurrent seizures either impair or have no effect on learning and memory. However, the effects of brief seizures on learning and memory remain unknown. Here, we found that a single injection of a convulsive dose of PTZ (50 mg/kg, ip) induced brief seizures in Sprague–Dawley rats. Administration of PTZ before training impaired the acquisition of spatial memory in the Morris water maze (MWM) and fear memory in contextual fear conditioning. However, the administration of PTZ immediately after training did not affect memory consolidation in either task. These findings suggest that brief seizures have different effects on acquisition and consolidation of spatial and fear memory.

Ketogenic diet is antiepileptogenic in pentylenetetrazole kindled mice and decrease levels of N-acylethanolamines in hippocampus

The ketogenic diet (KD) is used for the treatment of refractory epilepsy in children, however, the mechanism(s) remains largely unknown. Also, the antiepileptogenic potential in animal models of epilepsy has been poorly addressed. Activation of cannabinoid type-1 receptor (CB 1-R) upon seizure activity may mediate neuroprotection as may several N-acylethanolamines. It is unknown how the KD interfere with the endocannabinoid system. We investigated the antiepileptogenic potential of the KD in the pentylenetetrazole kindling model in young mice and measured the hippocampal levels of CB 1-R by Western blot and of endocannabinoids and N-acylethanolamines by mass spectrometry. The KD significantly decreased incidence and severity of seizures, and significantly increased the latency to clonic convulsions. There were no changes in levels of endocannabinoids or CB 1-R expression by either seizure activity or type of diet. The level of oleoylethanolamide as well as the sum of N-acylethanolamines were significantly decreased by the KD, but were unaffected by seizure activity. The study shows that the KD had clear antiepileptogenic properties in the pentylenetetrazole kindling model and does not support a role of endocannabinoids in this model. The significance of the decreased hippocampal level of oleoylethanolamide awaits further studies.

Pharmacological screening of Malian medicinal plants used against epilepsy and convulsions

Ethnopharmacological relevance Several medicinal plants are used in Mali to treat epilepsy and convulsions. So far, no studies have investigated the pharmacological effect of these plants. Aims The aim of this study was to investigate the in vitro and in vivo antiepileptic potential of the ethanolic extracts of 11 Malian medicinal plants. Materials and methods The extracts were screened for antiepileptic properties in the mouse cortical wedge preparation and in the [ 3H]-flumazenil binding assay. Two of the plant extracts were investigated for anticonvulsive properties in the pentylenetetrazol (PTZ) kindling model in mice. Possible side effects on motor impairment were evaluated using the rota-rod test. Results Extracts of 10 of the 11 medicinal plants showed affinity to the benzodiazepine binding site on the GABA A receptor. Seven of the 11 extracts inhibited the spontaneous discharges (SEDs) in the mouse cortical wedge preparation, with the extracts of Flueggea virosa and Psorospermum senegalense being the most potent. However, when tested for in vivo anticonvulsive properties these two extracts failed to show any effect on PTZ-induced seizures in mice. Conclusions The pharmacological screening of the ethanolic extracts of 11 Malian medicinal plants in vitro lead to the identification of several extracts with potential anticonvulsant properties.

Endogenous dynorphin in epileptogenesis and epilepsy: anticonvulsant net effect via kappa opioid receptors

Neuropsychiatric disorders are one of the main challenges of human medicine with epilepsy being one of the most common serious disorders of the brain. Increasing evidence suggest neuropeptides, particularly the opioids, play an important role in epilepsy. However, little is known about the mechanisms of the endogenous opioid system in epileptogenesis and epilepsy. Therefore, we investigated the role of endogenous prodynorphin-derived peptides in epileptogenesis, acute seizure behaviour and epilepsy in prodynorphin-deficient mice. Compared with wild-type littermates, prodynorphin knockout mice displayed a significantly reduced seizure threshold as assessed by tail-vein infusion of the GABA(A) antagonist pentylenetetrazole. This phenotype could be entirely rescued by the kappa receptor-specific agonist U-50488, but not by the mu receptor-specific agonist DAMGO. The delta-specific agonist SNC80 decreased seizure threshold in both genotypes, wild-type and knockout. Pre-treatment with the kappa selective antagonist GNTI completely blocked the rescue effect of U-50488. Consistent with the reduced seizure threshold, prodynorphin knockout mice showed faster seizure onset and a prolonged time of seizure activity after intracisternal injection of kainic acid. Three weeks after local injection of kainic acid into the stratum radiatum CA1 of the dorsal hippocampus, prodynorphin knockout mice displayed an increased extent of granule cell layer dispersion and neuronal loss along the rostrocaudal axis of the ipsi- and partially also of the contralateral hippocampus. In the classical pentylenetetrazole kindling model, dynorphin-deficient mice showed significantly faster kindling progression with six out of eight animals displaying clonic seizures, while none of the nine wild-types exceeded rating 3 (forelimb clonus). Taken together, our data strongly support a critical role for dynorphin in the regulation of hippocampal excitability, indicating an anticonvulsant role of kappa opioid receptors, thereby providing a potential target for antiepileptic drugs.

Pentylenetetrazol kindling in rats: Is neurodegeneration associated with manifestations of convulsive activity?

Structural changes in neurons and measures of oxidative stress were studied in the hippocampus of rats tolerant (ST) and sensitive (SS) to developing clonic-tonic seizures in conditions of pentylenetetrazol kindling. Sequences of 11 injections of pentylenetetrazol significantly decreased the number of normal neurons in hippocampal field CA1 in SS rats, this effect being seen in both hippocampal field CA1 and the dentate fascia in ST rats. Decreases in the numbers of normal neurons were accompanied by increases in the numbers of damaged cells in field CA4 in rats of both groups. After 21 injections, decreases in the numbers of normal neurons were seen in field CA1 in both SS and ST rats, while the numbers of damaged neurons were significantly greater than control only in ST rats in fields CA1 and CA4. The glutathione level was significantly lower in the hippocampus in both groups of rats than in controls. Thus, rats " tolerant" to developing convulsions show signs of oxidative stress and neurodegenerative changes in the hippocampus. This suggests that oxidative neuron damage leading to neurodegeneration in the pentylenetetrazol kindling model is not directly associated with convulsive activity.

Study of Antiepileptic Effect of Extracts from Acorus tatarinowii Schott

To study the antiepileptic properties of extracts from rhizomes of Acorus tatarinowii Schott (ATS). The decoction and volatile oil were extracted from rhizomes of ATS by traditional decocting and supercritical CO(2) fluid extraction (SFE-CO(2)) methods. Maximal electroshock (MES), pentylenetetrazol (PTZ) maximal seizure, and prolonged PTZ kindling models were used to test their anticonvulsive properties. The gamma-aminobutyric acid (GABA) immunohistochemical reaction (IR) was used to study GABAergic neuron changes in the PTZ kindling model and the effects of treatment. Both decoction (dose; 10-20 g/kg) and volatile oil (1.25 g/kg) of ATS decreased the convulsive rate significantly in the MES model. Decoction of ATS was shown to be effective in the PTZ model with both decreased convulsive and mortality rates. The volatile oil of ATS failed to prevent seizures in the dose range tested, although prolonged seizure latency and decreased mortality were found at a dose of 1.25 g/kg. In the PTZ kindling model, GABA-IR neurons decreased obviously compared with the normal group. In the groups treated with the decoction and volatile oil, the seizure intensity decreased significantly after treatment. Increased GABA-IR neurons also were found when compared with PTZ kindling controls. Morphologic observation also showed that GABA-IR neuron damage was less severe in the drug-treated groups. Both decoction and volatile oil extracted from the rhizome of Acorus tatarinowii Schott have anticonvulsive effects. The volatile oil is shown to be less effective for PTZ-induced convulsions. Both extracts can prevent convulsions as well as convulsion-related GABAergic neuron damage in the brain in the prolonged PTZ kindling model.

Down-regulation of dopamine D 1 and D 2 receptors in the basal ganglia of PTZ kindling model of epilepsy: effects of angiotensin IV

The present study examined the effect of pentylenetetrazol (PTZ) induced kindling as well as the action of the hexapeptide angiotensin IV (ANG IV) on the dopamine (DA) D 1 and D 2 receptor binding in the basal ganglia of the mouse brain. By using quantitative receptor autoradiography, it was found that PTZ kindling led to a decrease in DA D 2 receptor density (about 20%) in all regions of the neostriatum (NS) as well as in the olfactory tubercle (OT), the nucleus accumbens (NA) and the globus pallidus, which persisted 24 h and 7 days after the kindling procedure. PTZ induced kindling also elicited a decrease in DA D 1 receptor binding sites (about 10%), which however was, restricted to the rostral NS (rNA) and NA. ANG IV (0.2 mg/kg), injected prior to PTZ, not only prevented the development of the kindling process but it also reversed the kindling-induced down-regulation of both DA receptors to the control levels. Furthermore ANG IV induced an area-specific increase of DA D 1 receptor density above control levels in the dorsal part of rNS. These findings suggest that DA D 2 receptors could mainly contribute to epileptogenesis in the PTZ kindling model, whereas the role of DA D 1 receptors is limited to particular regions in the basal ganglia. The anticonvulsant effect of ANG IV pretreatment might be influenced by a DA-related mechanism and particularly by preventing D 2 receptor down-regulation as well as by an adaptive area-specific increase in DA D 1 receptors.

Effects of compounds acting on GABA B receptors in the pentylenetetrazole kindling model of epilepsy in mice

The involvement of GABA B receptors in the behavioural and epileptic electrocortical discharges occurring in chemical kindling induced by repeated treatments with a subconvulsant dose of pentylenetetrazole (25 mg/kg i.p.) has been investigated in CD1 mice. Behavioural and electrocorticographic epileptic seizures following kindling induced by pentylenetetrazole (25 mg/kg i.p.) were attenuated or completely antagonized in a dose–dependent manner by the GABA B receptor agonist R–baclofen (2 and 6 mg/kg) whilst the GABA B receptor antagonist 3–amino–propyl–diethoxy–methyl–phosphinic acid (CGP 35348, 25, 50 or 100 mg/kg) and 3–[1–(S)–(3,4–dichloro–phenyl–ethyl]amino–2–(S)–hydroxy–propyl–benzyl–phosphinic acid (CGP 55845A, 10 or 20 mg/kg) produced a more rapid development of kindling and an increase in behavioural and electrocorticographic epileptic changes. In addition, all GABA B receptor antagonists were able to induce an increase in Fos and Jun protein expression in pentylenetetrazole (25 mg/kg i.p.) treated mice whilst the GABA B receptor agonist R–baclofen (2 or 6 mg/kg) attenuated the expression of Fos and Jun protein, at cortical and limbic structures. In order to study the persistence of changes induced by pentylenetetrazole kindling, different groups of mice were rechallenged with a kindling stimulus 15 or 30 days after withdrawal from the last injection of vehicle+pentylenetetrazole, R–baclofen+pentylenetetrazole or GABA B receptor antagonists+pentylenetetrazole. The groups receiving GABA B receptor antagonists+pentylenetetrazole showed a higher incidence of seizures following the kindling stimulus than mice receiving vehicle+pentylenetetrazole whilst animals treated with R–baclofen were protected from the kindling stimulus. The different effects observed following repeated treatment with the GABA B receptor agonist and antagonist used revealed that GABA B receptors are able to affect the development of the epileptic kindling state induced by pentylenetetrazole.

Anticonvulsant effect of felbamate in the pentylenetetrazole kindling model of epilepsy in the rat.

The present study was designed to examine the ability of felbamate, a novel antiepileptic agent, to antagonize the increase in seizure severity (i.e., chemical kindling) produced by chronic treatment with initially subconvulsant doses of pentylenetetrazol (PTZ). Rats were treated with PTZ (30 mg/kg, i.p., three times a week) for 8 consecutive weeks. Two other groups of rats received felbamate (300 or 400 mg/kg, i.p.), 90 min before each dose of PTZ. Pretreatment with felbamate at either dose prevented the progression of rank of seizures during chronic treatment with PTZ. Thus, the mean seizure score by the end of the chronic treatment (0-5 scale) was 0 in vehicle treated controls, 3.3 in rats treated with PTZ alone, 1.5 in rats treated with PTZ plus felbamate (300 mg/kg, i.p.) and 0.9 in the group treated with PTZ plus felbamate (400 mg/kg, i.p.). Felbamate also antagonized the long-term increase in the sensitivity to the convulsant effects of GABA function inhibitors observed in PTZ-kindled rats. Thus, the administration of a challenge dose of isoniazid (120 mg/kg, s.c.), picrotoxin (1.5 mg/kg, i.p.) or PTZ itself (15 mg/kg, i.p.), 15 to 45 days after the end of the chronic treatment regimen, induced convulsions in > 80% of PTZ-kindled rats and in < 20% of rats treated with PTZ + felbamate (400 mg/kg). The results are discussed in terms of the multiple mechanisms that can contribute to the anticonvulsant action of felbamate in the PTZ kindling model of epilepsy.

Aspects of the pentylenetetrazol kindling model of epileptogenesis in the rat

The kindling model of epileptogenesis is characterized by the induction of a persistent reduction of seizure threshold after repeated exposures of the brain to stimuli which were initially subconvulsive. We studied the ability of repeated injections of pentylenetetrazol (PTZ) to induce kindling. Subconvulsive doses of PTZ (20–25 mg/kg, i.p.) were administered to rats every 4 days for a total of 21 treatments. The convulsive response score of PTZ-treated rats remained elevated upon challenge with 22.5 mg/kg PTZ after a 3-week PTZ-free period. Studies on the mechanisms involved in PTZ-induced kindling revealed that hepatic microsomal P-450 concentrations were unchanged after chronic PTZ treatment. No significant changes in brain amino acids, including GABA and taurine, two neuroinhibitory amino acids which have been implicated in the regulation of seizure phenomena, were found in PTZ-kindled animals.