Naringin ameliorates pentylenetetrazol-induced seizures and associated oxidative stress,inflammation, and cognitive impairment in rats: Possible mechanisms of neuroprotection

Oxidative stress and cognitive impairment are associated with PTZ-induced convulsions. Naringin is a bioflavonoid present in the grapefruit. It is a potent antioxidant, and we evaluated its effect on PTZ-induced convulsions. Rats were pretreated with normal saline, naringin (20, 40, and 80 mg/kg, i.p.), or diazepam (5 mg/kg, i.p.) 30 min prior to the administration of PTZ. The administration of PTZ induced myoclonic jerks and generalized tonic–clonic seizures (GTSs). We observed that naringin significantly prolonged the induction of myoclonic jerks dose-dependently. Naringin (80 mg/kg, i.p.) pretreatment protected all rats, and this protective effect was annulled by the GABA_A receptor antagonist, flumazenil. In addition, naringin reduced brain MDA and TNF-α levels and conserved GSH. The pretreatment also enhanced the performance of rats in the passive avoidance task. Our observations highlight the antioxidant, antiinflammatory, and anticonvulsant potential of naringin. Also, naringin modulates the GABA_A receptor to produce anticonvulsant effects and to ameliorate cognitive impairment.     

Interactions between angiotensin II, GABA and diazepam in convulsive seizures

In experiments on male mice, we studied the effects of gamma-aminobutyric acid (GABA), angiotensin II (AT II), administered intracerebroventricularly, diazepam, injected intraperitoneally, and combinations of GABA + AT II and diazepam + AT II on convulsive seizures induced by pentylenetetrazol (PTZ) (80 mg/kg subcutaneously) and 3-mercaptopropionic acid (3-MPA) (40 mg/kg intraperitoneally). The anticonvulsant effects of GABA and diazepam on PTZ-induced seizures were increased by AT II in doses which did not significantly influence seizures. AT II applied together with GABA or diazepam in ineffective doses provoked a strong anticonvulsant effect on both PTZ- and 3-MPA-induced seizures. These results indicate that the anticonvulsant effects of GABA and diazepam on PTZ- and 3-MPA-induced seizures might effectively be potentiated by the octapeptide AT II. It is suggested that AT II operates as an endocoid acting on GABA, respectively benzodiazepine recognition sites in the CNS.     

Timed pentylenetetrazol infusion test: a comparative analysis with s.c.PTZ and MES models of anticonvulsant screening in mice.

The intravenous pentylenetetrazol (i.v.PTZ) seizure test provides threshold dose for induction of seizures in individual animals. In the present study, the i.v. and s.c.PTZ seizure models in mice were compared for seizure pattern, intra- and interanimal variability. Anticonvulsant activities of several antiepileptic drugs (AEDs) at non-ataxic dose levels were evaluated in the PTZ and maximal electroshock (MES) seizure tests. In the i.v.PTZ test, at 0.5 ml/min rate of administration, the mean threshold PTZ doses for induction of clonus and tonic extensor were 44.17 and 99.59 mg/kg, respectively. The intra- and interanimal variabilities in the seizure response were low in the i.v.PTZ as compared to the s.c.PTZ model. Phenobarbital sodium, ethosuximide, sodium valproate, diazepam, tiagabine, oxcarbazepine and zonisamide enhanced threshold or onset latency for clonus in the i.v. and s.c.PTZ tests, respectively. Levetiracetam and pregabalin were active in the i.v.PTZ test, but had no effect in the s.c.PTZ test. Ability of AEDs to protect from tonic extensor was compared in the MES and i.v.PTZ tests. For this effect, phenobarbital sodium, phenytoin, carbamazepine, sodium valproate, gabapentin, oxcarbazepine, zonisamide and pregabalin were effective in the i.v.PTZ and MES tests. Ethosuximide, diazepam and levetiracetam were effective in the i.v.PTZ test, but not the MES test. On the contrary, lamotrigine and topiramate were active in the MES, but not the i.v.PTZ test. These results indicate that it is advantageous to use i.v.PTZ test as an acute seizure model for screening of antiepileptic drugs. This model can identify molecules with varied mechanism of action and broad clinical utility in the treatment of epilepsy.     

Selective antiepileptic effects of N-palmitoylethanolamide, a putative endocannabinoid

PURPOSE: The purpose of this study was to determine whether N-palmitoylethanolamide (PEA), a putative endocannabinoid, would be effective against kindled amygdaloid seizures. For a comparison with earlier work, we also tested the effectiveness of PEA against pentylenetetrazol (PTZ)-induced convulsions. METHODS: Kindling electrodes were implanted bilaterally in the amygdala in 32 Long-Evans rats. After the kindling of generalized (stage 5) seizures, the effects of PEA administration [i.p.; 1, 10, 100 mg/kg in dimethylsulfoxide (DMSO)] were evaluated for anticonvulsant activity. PEA (40 mg/kg, i.p. in DMSO) also was tested for anticonvulsant activity against PTZ-induced convulsions (75 mg/kg, i.p.). RESULTS: After i.p. administration of PEA, kindled rats displayed an increased latency to clonus at the 1-mg/kg dose. No other dose-dependent effects were noted. When tested against PTZ-induced convulsions, PEA protected against tonic convulsions and prolonged the latency between convulsive episodes. CONCLUSIONS: PEA produces antiepileptic effects, but does not completely suppress seizures. The mechanism of action of PEA remains to be defined.     

Chronic treatment with diazepam or the inverse benzodiazepine receptor agonist FG 7142 causes differential changes in the effects of GABA receptor stimulation

Daily treatment of mice with diazepam leads to the development of tolerance to the anxiolytic and anticonvulsant effect of the benzodiazepine, while daily treatment with the proconvulsant benzodiazepine receptor inverse agonist FG 7142 produces sensitization to its effects in that seizures develop (chemical kindling). In the present study, the effects of GABA receptor stimulation were studied 2 days after termination of 13 days treatment with diazepam, 20 mg/kg i.p./day, and FG 7142, 40 mg/kg i.p./day. For GABA receptor stimulation, the GABA agonist progabide was chosen because among several GABA receptor stimulants tested it was the only compound that induced increases in seizure threshold in non-toxic doses. Using the threshold for maximal (tonic extension) electroconvulsions as a measure for anticonvulsant efficacy, the anticonvulsant effect of progabide (100 mg/kg i.p.) was unchanged after chronic treatment with diazepam but was lost in FG 7142 kindled animals. Conversely, the hypothermic effect of progabide was reduced after treatment with diazepam but not with FG 7142. Baseline seizure threshold was unchanged 2 days after chronic administration of diazepam but increased in the FG 7142 pretreated mice. The data indicate that tolerance to benzodiazepines and kindling by FG 7142 are associated with different changes in GABA receptor function.     

The effects of coenzyme Q10 on seizures in mice: The involvement of nitric oxide

Coenzyme Q10 is a potent antioxidant in both mitochondria and lipid membranes. It has also been recognized to have an effect on gene expression. This study was designed to investigate whether acute or subchronic treatment with coenzyme Q10 altered the seizures induced by pentylenetetrazole or electroshock in mice. We also evaluated the involvement of nitric oxide in the effects of coenzyme Q10 in pentylenetetrazole-induced seizure models. Acute oral treatment with different doses of coenzyme Q10 did not affect the seizure in intraperitoneal pentylenetetrazole, intravenous pentylenetetrazole, and electroshock models in mice. Subchronic oral administration of coenzyme Q10 (100 mg/kg or more) increased time latencies to the onset of myoclonic jerks and clonic seizures induced by intraperitoneal pentylenetetrazole and at the doses of 25 mg/kg or more increased the seizure threshold induced by intravenous infusion of pentylenetetrazole. Subchronic doses of coenzyme Q10 (50 mg/kg or more) also decreased the incidence of tonic seizures in the electroshock-induced seizure model. Moreover, acute treatment with the precursor of nitric oxide synthesis, l-arginine (60 mg/kg), led to a significant potentiation of the antiseizure effects of subchronic administration of coenzyme Q10 (400 mg/kg in intraperitoneal and 6.25 mg/kg in intravenous pentylenetetrazole tests). Acute treatment with l-NAME (5 mg/kg), a nonspecific nitric oxide synthase inhibitor, significantly attenuated the antiseizure effects of subchronic doses of coenzyme Q10 in both seizure models induced by pentylenetetrazole. On the other hand, acute administration of aminoguanidine (100 mg/kg), a specific inducible nitric oxide synthase inhibitor, did not affect the seizures in mice treated with subchronic doses of coenzyme Q10 in both intraperitoneal and intravenous pentylenetetrazole tests. In conclusion, only subchronic and not acute administration of coenzyme Q10 attenuated seizures induced by pentylenetetrazole or electroshock. We also demonstrated, for the first time, the interaction between nitric oxide and coenzyme Q10 in antiseizure activity probably through the induction of constitutive nitric oxide synthase.     

Probing the role of the sodium/calcium exchanger in pentylenetetrazole-induced generalized seizures in rats

The Na⁺/Ca²⁺ exchanger (NCX) is thought to play an important role in the pathogenesis of pentylenetetrazole (PTZ)-induced tonic flexion in mice. Here, I investigated the expression of PTZ-induced generalized clonic and tonic–clonic seizures in rats, using two potent NCX reverse mode inhibitors, KB-R7943 and SN-6 for NCX subtypes 3 (NCX3) and 1 (NCX1), respectively. Pretreatment with KB-R7943 (3, 10, and 30 mg/kg; p.o.) significantly reduced the expression of PTZ-induced generalized seizures with clonic and tonic–clonic components in 12–62% and 25–62% of the treated animals, respectively. In the remaining animals that exhibited seizures, KB-R7943 (3 mg/kg; p.o.) pretreatment significantly delayed the onset of the first seizure episode and reduced the seizure severity. Following pretreatment with SN-6 (0.3, 1, 3, 10, and 30 mg/kg; p.o.), clonic and tonic–clonic PTZ-induced generalized seizures were reduced in 25–50% and 38–63% of treated animals, respectively. SN-6 (0.3, 1, and 3 mg/kg; p.o.) also significantly reduced PTZ-induced seizure severity scores, but did not alter seizure latencies. KB-R7943 (3 and 30 mg/kg; p.o.) or SN-6 (3 and 30 mg/kg; p.o.) administration potentiated the sub-anticonvulsant dose of diazepam (2.5 mg/kg; i.p.) that suppresses clonic and tonic–clonic PTZ-induced seizures. These findings suggested that Ca²⁺ influx via the NCX in reverse mode contributes to a neuronal hyperexcitability that leads to clonic and tonic–clonic generalized seizures and that the NCX1 and NCX3 isoforms may serve as novel molecular targets for seizure suppression.     

Mirtazapine does not affect pentylenetetrazole- and maximal electroconvulsive shock-induced seizures in mice

Mirtazapine is an antidepressant exhibiting both noradrenergic and serotonergic activity. We have investigated the effects of mirtazapine on pentylenetetrazole (PTZ)- and maximal electroconvulsive shock (MES)-induced seizures in mice. Mirtazapine (1.25-20mg/kg) or saline was administered, and locomotor activity was evaluated for 30 min. One hour after administration of mirtazapine (1.25-5mg/kg) or saline, PTZ (80 mg/kg) was injected intraperitoneally into the mice. Immediately afterward, times of onset of the first myoclonic jerk (FMJ), generalized clonic seizures (GCS), and tonic extension (TE) were recorded. In the MES groups, we used the MES protocol to induce convulsions characterized by tonic hindlimb extension. Similarly, 1h after mirtazapine or saline administration, an electroshock was evoked by ear-clip electrodes to induce convulsion. Mirtazapine, at 10 and 20 mg/kg, depressed locomotor activity. Doses of 1.25-5mg/kg had no significant effect on the time of onset of FMJ, GCS, or TE induced by PTZ; on the duration of GCS and TE; or on the latency to reinstatement of the righting reflex after MES administration. Our results suggest that mirtazapine neither aggravates nor alleviates PTZ- or MES-induced seizures in mice.     

Vigabatrin in low doses selectively suppresses the clonic component of audiogenically kindled seizures in rats

PURPOSE: The effect of systemic administration of the gamma-aminobutyric acid (GABA)-transaminase inhibitor vigabatrin (VGB) on different components of convulsions was tested in the model of audiogenically kindled seizures, which consist of brainstem (running, tonus) and forebrain (clonus) elements. METHODS: Audiogenically susceptible rats of Krushinsky-Molodkina (KM), Wistar, and WAG/Rij strains received repeated sound stimulation (60 dB, 10-80 kHz) until kindled audiogenic seizures were reliably elicited. Kindled audiogenic seizures consisted of running, tonic, and generalized clonic phases in KM rats (severe audiogenic seizures) and of running and Racine stage 5 facial/forelimb clonus in Wistar and WAG/Rij rats (moderate seizures). Vehicle, 100, or 200 mg/kg of VGB was intraperitoneally injected 2, 4 and 24 h before the induction of kindled audiogenic seizures. RESULTS: At both doses, VGB did not change the seizure latency and the duration of running and tonic convulsions, but suppressed clonic ones in all rat strains. In KM rats, the mean duration of posttonic clonus was significantly reduced at 24 h after 100 mg/kg and from 4 h after 200 mg/kg. In Wistar and WAG/Rij rats, the mean duration of facial/forelimb clonus was reduced from 4 and 2 h after 100- and 200-mg/kg administration, respectively; 24 h after the high-dose injection, clonus was completely blocked in all rats of both strains. No difference in efficacy of VGB between Wistar and WAG/Rij rats was observed. CONCLUSIONS: VGB more effectively suppresses clonic convulsions than running and tonic ones in audiogenically kindled rats. It is supposed that this selective anticonvulsive effect of VGB results from different sensitivities of forebrain and brainstem epileptic networks to the presumed GABA enhancement.     

Rofecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor increases pentylenetetrazol seizure threshold in mice: possible involvement of adenosinergic mechanism

Multiple lines of investigations have explored the role of cyclooxygenases (COX) in epilepsy and related neuropsychiatric disorders. Cyclooxygenase particularly, COX-2 expression was found to increase in brain during seizure paradigms. The present study was carried out to investigate the effect of rofecoxib, a selective COX-2 inhibitor against pentylenetetrazol (PTZ i.v.) seizure threshold in mice. The study was further extended to elucidate the possible involvement of adenosinergic mechanism in mediating its anticonvulsant action. Minimal dose of PTZ (i.v., mg/kg) needed to induce different phases (myoclonic jerks, generalized clonus and tonic extension) of PTZ convulsions were noted as an index of seizure threshold. Acute administration of rofecoxib (4mg/kg, i.p.) before PTZ infusion produced an elevation of seizure threshold for all the phases of convulsions. A lower dose of rofecoxib (2mg/kg, i.p.) showed an increase in PTZ seizure threshold for the onset of myoclonic jerks and tonic extension phases but not for generalized clonus. A still lower dose of rofecoxib (1mg/kg, i.p.) failed to increase the threshold in any of the convulsive phases induced by PTZ i.v. infusion. Pretreatment with sub-effective dose of rofecoxib (1mg/kg, i.p.) enhanced the action of sub-protective doses of either adenosine (25mg/kg, i.p.) or 2-chloroadenosine (1 or 2mg/kg, i.p.) in increasing the seizure threshold. On the contrary, treatment with caffeine (100 or 200mg/kg, i.p.) or theophylline (50 or 100mg/kg, i.p.), both non-selective A(1)/A(2) adenosine receptor antagonists reversed the anticonvulsant effect of rofecoxib (4mg/kg, i.p.). Further, dipyridamole (5mg/kg, i.p.), an adenosine uptake inhibitor displayed an anticonvulsant effect with rofecoxib (1mg/kg, i.p.). The study for the first time demonstrated the possible involvement of adenosinergic system in the anticonvulsant effects of rofecoxib against PTZ i.v. seizure threshold paradigm in mice.     

Testosterone reduces pentylenetetrazole-induced ictal activity of wildtype mice but not those deficient in type I 5α-reductase

Testosterone’s (T) anti-seizure effects may be mediated in part by actions of its 5α-reduced metabolites. To test this hypothesis, T was administered to knockout mice deficient in the 5α-reductase type I enzyme and wildtype controls and their ictal activity following pentylenetetrazole (PTZ; 85 mg/kg i.p.) was compared to mice administered vehicle. T to wildtype mice increased latencies to forelimb clonus, tonic clonic seizures, hindlimb extension, and death compared to that seen with vehicle administration. Moreover, incidence of tonic clonic seizures and hindlimb extension were reduced in wildtype mice administered T compared to vehicle-administered mice. T administration to wildtype mice reduced ictal activity compared to T to knockout mice, which were not different than vehicle-administered control mice. T to wildtype mice increased the latencies and decreased the incidence of forelimb clonus compared to T to knockout mice, which were not different from vehicle-administered mice. These data are consistent with T having anti-convulsant effects and that 5α-reduced metabolites may mitigate some of T’s anti-seizure effects.     

Anticonvulsant effects of acute and repeated fluoxetine treatment in unstressed and stressed mice

Comorbidity of epilepsy and depression is not rare. Stress can affect both depression and seizures. Therefore, it is important to know whether an antidepressant drug has pro- or anticonvulsant properties and whether these properties will be modified by stress. We tested the effects of the antidepressant drug fluoxetine on the seizure threshold for picrotoxin in unstressed and swim-stressed mice. The mice were, prior to exposure to swim stress and the intravenous infusion of picrotoxin (a non-competitive GABA(A) receptor antagonist), pretreated with fluoxetine (a selective serotonin reuptake inhibitor), either acutely or repeatedly (5 days), and the latency to the onset of two convulsant signs and death was registered. The convulsant signs were running/bouncing clonus and tonic hindlimb extension. As expected, swim stress enhanced the seizure threshold for picrotoxin. Fluoxetine (20 mg/kg ip) given acutely increased in unstressed and swim-stressed mice the dose of picrotoxin producing tonic hindlimb extension and in unstressed mice the dose of picrotoxin producing death. Neither 10 nor 20 mg/kg of fluoxetine affected doses of picrotoxin needed to produce running bouncing/clonus. Repeated treatment with fluoxetine (20 mg/kg ip) enhanced significantly in unstressed and swim-stressed mice doses of picrotoxin needed to produce tonic hindlimb extension and death, and in stressed mice also the dose of picrotoxin producing running/bouncing clonus. The results demonstrate that the antidepressant drug fluoxetine, given acutely or repeatedly, shows anticonvulsant properties against convulsions induced in unstressed and swim-stressed mice by antagonist of GABA(A) receptors, picrotoxin. Swim stress failed to modify the anticonvulsant properties of fluoxetine.     

Morphine sensitization in the pentylenetetrazole-induced clonic seizure threshold in mice: role of nitric oxide and μ receptors

Behavioral sensitization occurs after repeated administration of μ-opioid receptor agonists following a drug-free period. It seems that the changes in dopaminergic systems induced by μ-opioid receptor agonists play a crucial role in behavioral sensitization to opioids. Nitric oxide also plays a role in some behavioral effects of morphine, including sensitization to the locomotor-stimulating effect. This study investigated whether morphine sensitization appears in seizure threshold and the possible role of μ-opioid receptor and nitric oxide in this sensitization. Sensitization was produced by daily injections of morphine (0.1, 0.5, 1, 5, 15, or 30 mg/kg), followed by a 10-day washout period. Then the challenge test was performed using morphine (0.1, 0.5, 1, 5, 15, or 30 mg/kg) in different groups. To assess clonic seizure threshold, pentylenetetrazole (PTZ) was administered intravenously. Subcutaneous administration of morphine (0.1 and 0.5 mg/kg) induced sensitization in PTZ-induced clonic seizures in mice. Intraperitoneal administration of L-NAME (20 mg/kg), a nonselective inhibitor of nitric oxide synthase, or naltrexone (10 mg/kg), an opioid receptor antagonist, along with morphine inhibited morphine-induced sensitization in PTZ-induced seizure threshold. In conclusion, at low doses, morphine induces sensitization in PTZ-induced clonic seizures in mice probably as a result of the interaction with μ-receptors and nitric oxide.     

Long-term Treatment with some Methylxanthines Decreases the Susceptibility to Bicuculline- and Pentylenetetrazol-induced Seizures in Mice. Relationship to c-ios Expression and Receptor Binding

The effects of long-term oral administration of low doses of caffeine (0.3 g/l) and its metabolites theophylline, theobromine and paraxanthine (each at 0.5 g/l in drinking water) on bicuculline- and pentylenetetrazol (PTZ) -induced seizures and c-fos expression were studied in mice. In addition, adenosine and benzodiazepine receptor density was examined. The plasma levels of the methylxanthines were much higher during the active period at night than during the day. The maximal level of caffeine was 14 μM. Brain theophylline levels (8-13 nmol/g) tended to be higher and more constant than brain caffeine levels in caffeine-consuming mice. Clonic seizures induced by bicuculline (4 mg/kg i.p.) were significantly reduced in severity by 14 day caffeine treatment and mortality was also reduced. Long-term treatment with caffeine metabolites was less effective. The seizures induced by PTZ (60 mg/kg i.p.) were also significantly reduced by long-term caffeine treatment. After bicuculline or PTZ treatment, c-fos mRNA expression was weaker in the cerebral cortex in animals receiving caffeine, irrespective of whether the animals had seizures or not. No significant changes in the binding of adenosine receptor ligands or benzodiazepines were seen after long-term caffeine treatment. These results show that long-term treatment with caffeine in a dose that is commonly seen in humans decreases the seizures induced by bicuculline, and to a lesser extent, those induced by PTZ. This may be related to a decreased neuronal excitability. The effect is due to the combined effects of theophylline, to which caffeine is metabolized in brain, and of caffeine itself, but could not be ascribed to changes in A₁ and A_2A adenosine or benzodiazepine receptors.     

Sildenafil influences the anticonvulsant activity of vigabatrin and gabapentin in the timed pentylenetetrazole infusion test in mice

Sildenafil, a selective phosphodiesterase 5 (PDE5) inhibitor, has recently been reported to affect convulsant activity in some animal models of seizures and epilepsy. Moreover, its influence on the protective activity of some antiepileptic drugs (AEDs) was also noted. The aim of the present study was to investigate the effect of sildenafil on the anticonvulsant potential of gabapentin (GBP) and vigabatrin (VGB) in the timed intravenous (i.v.) pentylenetetrazole (PTZ) test in mice. The chimney test, the passive avoidance task and the grip strength test were used to estimate some possible side effects caused by the studied AEDs and their combinations with sildenafil. Total brain and free plasma concentrations of GBP and VGB were determined to evaluate the characteristics of interactions. Our studies revealed that GBP (25-100mg/kg) increases the threshold for the forelimb tonic extension, whereas VGB raises thresholds both, for myoclonic (200-600mg/kg) and generalized clonic (400-600mg/kg) seizures in the used model of seizures. GBP at sub-effective dose of 12.5mg/kg co-administered with sildenafil at doses of 10 and 20mg/kg significantly increases the threshold for tonic seizures in the i.v. PTZ test in mice. Combination of sub-effective dose of VGB (200mg/kg) with sildenafil at a dose of 5mg/kg also showed significant anticonvulsant activity against clonic seizures. The studied AEDs and their combinations with sildenafil did not produce any changes in the motor coordination, long-term memory and muscular strength in mice. Sildenafil did not influence total brain and free plasma concentrations of GBP and VGB. Interactions between the studied AEDs and sildenafil were pharmacodynamic in nature and for that reason they are worthy of consideration in the clinical practice.     

Behavioral analysis of amygdaloid kindling in beagle dogs and the effects of clonazepam, diazepam, phenobarbital, diphenylhydantoin, and flunarizine on seizure manifestation

This paper describes the behavioral changes seen in beagle dogs during kindling and reports on the effects of clonazepam, diazepam, phenobarbital, diphenylhy-dantoin, and flunarizine on kindled seizures. Eight dogs were implanted stereotaxically in the right basolateral amygdala. After recovery, they were stimulated once daily at stimulation parameters evoking mastication in the first sessions. Generalized tonic-clonic seizures developed rapidly in all dogs with an intermediate stage of facial clonus, head nodding, and profuse salivation. Kindled seizures began with facial clonus, head nodding, and salivation, and were followed by opisthotonos, lifting of the contralateral forepaw, falling over backward, clonicity of the hind legs, tonic extension of the forelegs and hindlegs, quiescence, myoclonic jerking or running seizures; and terminated with wetshaking. Diazepam (2.5 mg/kg) and phenobarbital (10 mg/kg) inhibited all phenomena in all animals. Clonazepam (≥0.63 mg/kg) and flunarizine (≥5 mg/kg) protected two of three animals against tonic and clonic seizures, but clonazepam was ineffective against facial clonus. Diphenylhydantoin was ineffective at doses to 40 mg/kg. Spontaneous seizures were seen occasionally in all animals. Four dogs died after developing status epilepticus. Kindling in dogs occurred rapidly and did not show the five stages seen in rats, and when kindled, animals were susceptible to the development of spontaneous seizures and status epilepticus.     

An examination of the proconvulsant actions of pyrethroid insecticides using pentylenetetrazol and amygdala kindling seizure models

Pyrethroid insecticides have recently been purported to possess strong proconvulsant potential. The seizure-inducing properties of two pyrethroids were assessed by pentylenetetrazol (PTZ) seizure models (repeated ip, suprathreshold ip, and iv), and electrical kindling of the amygdala. The efficacy of po versus ip routes of deltamethrin administration was compared using iv-PTZ administration and tests of locomotor activity in a figure-eight maze. Both po and ip deltamethrin produced comparable decreases in motor activity indicating the effectiveness of both of these exposure routes on biological activity. The Type I pyrethroid, cismethrin (15 mg/kg, po), produced a 17% reduction in the threshold dosage of ip-PTZ required to induce a seizure, while delaying the onset of generalized seizure activity. The Type II pyrethroid, deltamethrin (10 mg/kg, po), failed to alter threshold or latency to seizure onset, but did increase seizure duration. No differences were revealed between po (0, 10, 15 mg/kg) or ip (0, 1, 10 mg/kg) administered deltamethrin on seizure thresholds or durations following iv-PTZ. Seizure severity, however, was enhanced by pyrethroids administered po in the iv-PTZ and suprathreshold-ip PTZ tests, ip deltamethrin was without effect. Cismethrin (0, 8, 15 mg/kg) and deltamethrin (0, 6, 10 mg/kg) administered po daily, 2 hours prior to electrical kindling stimulation facilitated amygdala kindling to a minimal but equivalent degree at the highest dosage. This dosage also evoked strong behavioral signs of toxicity. Deltamethrin also induced spontaneous seizures in partially kindled animals in the absence of stimulation. Thus strong evidence of proconvulsant activity of pyrethroids was not evident. The primary effects were limited to an enhancement of seizure severity in response to PTZ (tonic seizures) and the provocation of spontaneous seizures in partially kindled animals.     

Diphenyl diselenide and 2,3-dimercaptopropanol increase the PTZ-induced chemical seizure and mortality in mice

The aim of the present study was to evaluate the interaction between a classic GABAergic antagonist -- pentylenetetrazol (PTZ) with an organoselenium compound -- diphenyl diselenide (PhSe)(2) and with the metal chelating agent -- 2,3 dimercaptopropanol (BAL). Mice were pre-treated with 150 micromol/kg (PhSe)(2) or BAL (250, 500 or 1000 micromol/kg) before treatment with PTZ. Pre-treatment with (PhSe)(2) reduced the latency for PTZ-induced seizure at doses of 40 and 60 mg/kg and cause a decrease in the latency for PTZ-induced death at the dose of 60 mg/kg. However, treatment with PTZ at dose of 80 mg/kg was not affected by (PhSe)(2) pre-treatment. Pre-treatment with BAL reduced the latency for PTZ-induced seizure at doses of 40 and 50 mg/kg. In addition, the latency for PTZ-induced death at the dose of 40 mg/kg was decreased significantly by pre-treatment with all doses of BAL. At the dose of 50mg/kg, a significant decrease in the latency for death occurred only in mice pre-treated with 500 and 1000 micromol/kg of BAL. Our results indicate that the PTZ-induced chemical seizures and mortality was enhanced by (PhSe)(2) and BAL. These results indicated that (PhSe)(2) and BAL interact with PTZ possibly by modulating the GABAergic system.     

一氧化氮合酶抑制剂对戊四氮诱导大鼠点燃模型及该酶阳性神经元的影响

目的：探讨一氧化氮（ＮＯ）在癫癎 发病中的作用．方法：ｉｐ ４０ｍｇ·ｋｇ－１·ｄ－１戊四氮 ３０ｍｉｎ前注射 ２５ｍｇ·ｋｇ－１的 ＮＧ－硝基－左旋－精氨酸（Ｌ－ＮＮＡ）,连续 ２２ｄ,观察两组的行为改变及点燃串,同时对 ３组动物海马,大脑皮质一氧化氮合酶（ＮＯＳ）阳性神经元的变化输入图像扫描仪,对其胞体平均灰度值进行比较。结果：Ｌ－ＮＮＡ可明显抑制戊四氮点燃模型;戊四氮点燃大鼠模型海马,大脑皮质神经元的ＮＯＳ活性显著增高．结论：ＮＯ参与了戊四氮点燃模型的形成。     

Long-term reduction of benzodiazepine receptor density in the rat cerebellum by acute seizures and kindling and its recovery 6 months later by a pentylenetetrazole challenge

Seizures induced by an acute pentylenetetrazole (50 mg/kg) injection were accompanied by a long-term (at 1-48 h, but not on day 7) decrease in the density (B(max)) of [3H]-diazepam binding to benzodiazepine receptors in rat cerebellar cortex with no change in affinity (K(d)). Kindling for 24 days by daily administrations of pentylenetetrazole (20 mg/kg) led to the same decrease in benzodiazepine receptor density (at 1-48 h, but not on day 7) as that observed after a single dose of pentylenetetrazole (50 mg/kg). This suggests a common mechanism for both acute and kindling-induced seizures, dependent on the long-term receptor changes. The increased susceptibility to seizures persisted for 6 months after the termination of kindling, with BDZ receptor density in cerebellar cortex reduced almost by half. In age-matched controls, an acute dose of PTZ (30 mg/kg) induced seizures and decrease in both B(max) and K(d) of [3H]-diazepam binding. In kindled rats, at 6 months post-kindling, the same dose of PTZ (30 mg/kg) restored the benzodiazepine receptor density to the level found 6 months before, at the time of termination of kindling. Also, the severity of seizures was enhanced in the kindled rats. The results are discussed in terms of a balance of inhibitory and excitatory processes, in which the reduced BDZ receptor density at 6 months post-kindling may represent a compensatory reaction to outbalance some alterations in excitatory systems that have been reported to be induced by kindling.