Subconvulsive Dose Of Pentylenetetrazole Research Articles

Delayed creatine supplementation counteracts reduction of GABAergic function and protects against seizures susceptibility after traumatic brain injury in rats

Traumatic brain injury (TBI) is a devastating disease frequently followed by behavioral disabilities including post-traumatic epilepsy (PTE). Although reasonable progress in understanding its pathophysiology has been made, treatment of PTE is still limited. Several studies have shown the neuroprotective effect of creatine in different models of brain pathology, but its effects on PTE is not elucidated. Thus, we decided to investigate the impact of delayed and chronic creatine supplementation on susceptibility to epileptic seizures evoked by pentylenetetrazol (PTZ) after TBI. Our experimental data revealed that 4 weeks of creatine supplementation (300 mg/kg, p.o.) initiated 1 week after fluid percussion injury (FPI) notably increased the latency to first myoclonic and tonic-clonic seizures, decreased the time spent in tonic-clonic seizure, seizure intensity, epileptiform discharges and spindle oscillations induced by a sub-convulsant dose of PTZ (35 mg/kg, i.p.). Interestingly, this protective effect persists for 1 week even when creatine supplementation is discontinued. The anticonvulsant effect of creatine was associated with its ability to reduce cell loss including the number of parvalbumin positive (PARV+) cells in CA3 region of the hippocampus. Furthermore, creatine supplementation also protected against the reduction of GAD67 levels, GAD activity and specific [3H]flunitrazepam binding in the hippocampus. These findings showed that chronic creatine supplementation may play a neuroprotective role on brain excitability by controlling the GABAergic function after TBI, providing a possible new strategy for the treatment of PTE.

Влияние анксиолитиков на тревожные реакции, обусловленные блокадой гамма-рецепторов, у крыс вистар и мышей инбредных линий BAKB/c и C57BL/6

Материалы V съезда фармакологов России «Научные основы поиска и создания новых лекарств» (14-18 мая 2018 года, г. Ярославль)

Treatment with lacosamide impedes generalized seizures in a rodent model of cortical dysplasia.

Epilepsy is a common neurologic disorder resulting in spontaneous, recurrent seizures. About 30-40% of patients are not responsive to pharmacologic therapies. This may be due to the differences between individual patients such as etiology, underlying pathophysiology, and seizure focus, and it highlights the importance of new drug discovery and testing in this field. Our goal was to determine the efficacy of lacosamide (LCM), a drug approved for the treatment of focal seizures, in a model of generalized epilepsy with cortical dysplasia (CD). We sought to compare LCM to levetiracetam (LEV), a drug that is currently used for the treatment of both partial and generalized epilepsy and to test its proficiency. Pregnant rats were irradiated to produce pups with malformed cortices in a model of CD, which will be referred to as the "first hit." Adult animals, developed normally (NL) and irradiated (XRT), were surgically implanted with electroencephalography (EEG) electrodes. Baseline EEG was recorded on all rats prior to pretreatments with either LCM, LEV, or placebo (PBO). After 30min, all rats were injected with a subconvulsive dose of pentylenetetrazole (PTZ), a γ-aminobutyric acid receptor A (GABAA ) antagonist used to provoke generalized seizures as a "second hit." LCM and LEV were both effective against seizures induced by PTZ. XRT rats had a higher seizure incidence with longer and more severe seizures than NL rats. Seizure duration was decreased with both LCM and LEV in all animals. In XRT rats, there was a significant reduction in acute seizure incidence and severity with both LCM and LEV after PTZ injection. Our results suggest that LCM could be used as a potential treatment option for generalized epilepsy with CD as the underlying pathology.

Effect of lamotrigine on seizure development in a rat pentylenetetrazole kindling model

IntroductionEpileptogenesis is a process of seizure development. Lamotrigine is a novel antiepileptic drug which is also used for antiepileptogenic research. Kindling models are recommended as potentially useful tools for antiepileptogenic treatment discovery. However, previous studies demonstrated that the antiepileptogenic effect of lamotrigine is controversial in the electrical kindling model. Chemical kindling such as with pentylenetetrazole is another kindling model. The aims of this study were to examine whether lamotrigine could prevent the development of seizure in pentylenetetrazole kindling rats.MethodsFemale rats were kindled by subconvulsive doses of pentylenetetrazole (35 mg/kg) once every other day for 15 times. Thereafter, the kindled rats received different doses of lamotrigine (5, 10 and 20 mg/kg) before pentylenetetrazole to observe the anticonvulsant effect. For the antiepileptogenic experiment, rats were kindled as the same way while pretreated (1 h) with different doses of lamotrigine (5, 10 and 20 mg/kg) before each injection of pentylenetetrazole. After a washout period for 1 week, the rats were administrated with pentylenetetrazole again for 3 times. The seizures were recorded each time. Later it was in vivo electrophysiological experiments followed with histologic analysis.ResultsFor the anticonvulsant experiment lamotrigine dose‐dependently suppressed pentylenetetrazole‐induced seizures. Here, 20 mg/kg of lamotrigine pretreatment significantly blocked the seizure development in rats for their seizure stages remained longer in 1–3 during the kindling phase. Mean seizure stages or generalized seizure durations in the 10 and 20 mg/kg lamotrigine pretreated groups were significantly lower or shorter when received 3 times of pentylenetetrazole after the washout period. Electrophysiological study also demonstrated 20 mg/kg of lamotrigine pretreatment obviously eliminated increased population spike amplitude in hippocampus. However, different doses of lamotrigine pretreatment could not alleviate severity of hippocampal neuronal damage.ConclusionsThe results suggest that adequate doses of lamotrigine can prevent seizure development in the pentylenetetrazole kindling rat model.

Mechanisms of histamine ameliorating memory impairment induced by pentylenetetrazole-kindling epilepsy in rats

Objective: To investigate the effects of neuronal histamine on spatial memory acquisition impairment in rats with pentylenetetrazole-kindling epilepsy, and to explore its mechanisms. Methods: A subconvulsive dose of pentylenetetrazole (35 mg/kg) was intraperitoneally injected in rats every 48 h to induce chemical kindling until fully kindled. Morris water maze was used to measure the spatial memory acquisition of the rats one week after fully pentylenetetrazole-kindled, and the histamine contents in different brain areas were measured spectrofluorometrically. Different dosages of hitidine (the precursor of histamine), pyrilamine (H1 receptor antagonist), and zolantidine (H2 receptor antagonist) were intraperitoneally injected, and their effects on spatial memory acquisition of the rats were observed. Results: Compared with control group, escape latencies were significantly prolonged on Morris water maze training day 2 and day 3 in pentylenetetrazole-kindling epilepsy rats (all P<0.05); and the histamine contents in hippocampus, thalamus and hypothalamus were decreased significantly (all P<0.05). Escape latencies were markedly shortened on day 3 by intraperitoneally injected with histidine 500 mg/kg, and on day 2 and day 3 by intraperitoneally injected with histidine 1000 mg/kg in pentylenetetrazole-kindling epilepsy rats (all P<0.05). The protection of histidine was reversed by zolantidine (10 and 20 mg/kg), but not by pyrilamine. Conclusion: Neuronal histamine can improve the spatial memory acquisition impairment in rats with pentylenetetrazole-kindling epilepsy, and the activation of H2 receptors is possibly involved in the protective effects of histamine.

Chronic 5-HT3 receptor antagonism ameliorates seizures and associated memory deficit in pentylenetetrazole-kindled mice

Our previous studies have suggested a strong involvement of serotonergic innervations in epileptogenesis and associated memory impairment. Several studies have suggested that the modulation of 5-HT3 receptors could serve as a promising tool for the management of epilepsy and memory deficit. The present study was envisaged to confirm this hypothesis. In this study, kindling was induced in male Swiss Albino mice using a subconvulsive dose of pentylenetetrazole (PTZ) (35mg/kg at 48±2h). Once the animals were kindled, they were treated with a vehicle, ondansetron (0.1, 0.5, 1mg/kg/day; i.p.), m-chlorophenylbiguanide (m-CPBG) (1mg/kg/day; i.p.), and ondansetron+m-CPBG for 20days. On days 5, 10, 15, and 20, they were administered a PTZ challenging dose (35mg/kg) to assess the seizure severity score; thereafter, memory was evaluated. After behavioral assessment on day 20, the animals were sacrificed and their brains were isolated to estimate cortical and hippocampal neurotransmitter levels (glutamate and gamma aminobutyric acid (GABA) by the high-performance liquid chromatography with the fluorescence detection method, and the nitrite level and acetylcholinesterase (AChE) activity by the microplate reader method). Ondansetron treatment significantly reduced the seizure severity and improved the acquisition performance in a dose-dependent manner. Neurochemical analysis suggested that ondansetron treatment significantly reduced the nitrite level and AChE activity in the cortex as well as in the hippocampus. The outcome of this study suggests the reduction in AChE activity and the nitrite level could be considered as protective mechanisms of ondansetron for amelioration of PTZ kindling and associated memory deficit.

Octreotide ameliorates inflammation and apoptosis in acute and kindled murine PTZ paradigms

In the present study, the role of octreotide (OCT) in pentylenetetrazole (PTZ) kindling as well as in acute convulsion models was evaluated. Mice were allocated in groups as (1) control saline; (2) acute PTZ (PTZ-a; 60mg/kg, i.p.), as a single convulsive dose; and (3) kindled (PTZ-k) receiving nine subconvulsive doses of PTZ (40mg/kg, i.p.) for 17days. Groups 4-7 received either valproic acid (VPA) 50mg/kg or OCT (50μg/kg, Sandostatin®) 30min by oral gavage before PTZ-a or PTZ-k. The median seizure stage, latency onset of first stage 4/5 seizures, and incidence of convulsing animals were recorded. Cortical dopamine (DA), tumor necrosis factor (TNF)-α, interleukin (IL)-10, caspase (Casp)-3, myeloperoxidase (MPO), and nitric oxide (NO) were assessed in addition to inducible nitric oxide synthase (iNOS) that was evaluated immunohistochemically in a different set of groups. OCT halted PTZ-induced epilepsy delaying convulsion latency via modulating MPO and TNF-α and normalizing IL-10 with both treatment regimens. In PTZ-k, it decreased Casp-3 activity, NO level, and iNOS immunoreactivity. OCT in both paradigms decreased DA concentration. The current investigation implicates a crucial role for OCT in modulating PTZ-induced kindling by regulating inflammatory and apoptotic effects.

Chaihushugan decoction exerts antiepileptic effects by increasing hippocampal glutamate metabolism in pentylenetetrazole-kindled rats

ObjectiveTo investigate the antiepileptic effects of Chaihushugan decoction (CHSGD) in rats with pentylenetetrazole (PTZ)-induced seizures and to discuss the impact of CHSGD on glutamate metabolism, a hypothesized underlying mechanism of seizure reduction. MethodsFifty Wistar rats were divided randomly into either control (n = 10) or experimental (n = 40) groups. Rats in the control group were administered physiological saline intraperitoneally. A sub-convulsive dose of PTZ (35 mg/kg) was administered intraperitoneally to rats in the experimental group to induce seizures. The fully PTZ-kindled rats were then randomly divided into five subgroups (n = 8 each) based on the following treatment categories: physiological saline, VPA (200 mg/kg), CHSGD (2.5 g/kg), CHSGD (5 g/kg), or CHSGD (10 g/kg), administered orally once per day, respectively. On day 28 following initiation of drug treatment, seizures were monitored. The rats were then sacrificed, and hippocampal dissections were performed for subsequent studies. ResultsCHSGD significantly prolonged the latency of myoclonic, clonic, and tonic seizures, while decreasing overall seizure rates in the kindled rats. The measured concentrations of 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) amino]-2-deoxy-d-glucose (2-NBDG) and glutamate were significantly lower in the hippocampi of kindled rats in groups treated with CHSGD compared with those treated with PTZ alone. In addition, CHSGD was found to up-regulate both the expression of glutamate transporter-1 (GLT-1) protein and the activity of glutamine synthetase (GS) in the hippocampi of kindled rats. ConclusionThese results suggest that CHSGD has antiepileptic effects on PTZ-induced seizures. The results further suggest an increase in glutamate metabolism at the synaptic cleft is a putative underlying mechanism of seizure reduction.

Pregabaline, gabapentin and nefedipine in pentylenetetrazole-kindled mice

Epilepsy is a big problem facing the society. There are a different modalities of treatment of epilepsy that extend for a long period. Pregabalin is classified as a miscellaneous analgesic and anticonvulsant and is structurally related to gabapentin. Most of antiepileptic drugs can reduce neuronal hyperexcitability by inhibiting ion channels including Ca channels. The current study aimed to evaluate the role of nifedpine in combination with pregabaline and gabapentin in pentylenetetrazole (PTZ)-kindled mice. Sixty mice were divided into 6 main groups (n=10), Positive control group treated by sub-convulsive dose of PTZ (35 mg/kg, i.p.), nifedipine treated group (20 mg/kg), Pregabaline treated group (40 mg/kg i.p.), Gabepentin treated group (200 mg/kg i.p.), Nifedipine + pregabaline group, Nifedipine+ gabapentin group. Pain tolerance measurement using right paw pad pressure tolerance was done. Our data indicate that gabapentin, pregabaline and nefidipine significantly decrease seizure activity in comparison to PTZ control mice (p<0.05) and these effects increase more significantly with combination of these drugs (p<0.009, p<0.011). In addition, gabapentin, pregabaline and nifedipine increase significantly pain tolerance in relation PTZ control mice (p<0.05) and coimplementation of both drugs either gabapentin with nifedpine or pregabaline with nifedipine show more synergistic significant effects on pain tolerance (p<0.001). In conclusion coapplication of these drugs together may lead to decrease of side effects and more control of epilepsy.

Anticonvulsant activity of the cyclooxygenase-2 (COX-2) inhibitor etoricoxib in pentylenetetrazole-kindled rats is associated with memory impairment

PurposeVarious selective and nonselective cyclooxygenase (COX) inhibitors are known to have effects on development and progression of seizures. In the present study, the effect of the selective COX-2 inhibitor etoricoxib on seizures, oxidative stress, and learning and memory was studied. MethodMale Wistar rats were kindled using subconvulsant dose of pentylenetetrazole (PTZ) (30mg/kg, i.p.), on alternating days until animals were fully kindled. After a one-week PTZ-free period, kindled rats were challenged with PTZ 30mg/kg, and the latency, duration, and severity of seizures were recorded. Etoricoxib was then administered intraperitoneally at 1mg/kg and 10mg/kg in kindled rats for nine days (days 6–14). On the ninth day of etoricoxib treatment, PTZ challenge (30mg/kg) was given, and seizure parameters were noted. On day 15, behavioral assessment was carried out. The Morris water maze (MWM) apparatus and the passive avoidance (PA) apparatus were used for studying cognitive impairment. The rats were then sacrificed, and malondialdehyde (MDA) and glutathione (GSH), markers of oxidative stress, were estimated in the brain samples. ResultsEtoricoxib at lower dose (1mg/kg) had an anticonvulsant effect which was reduced or reversed at higher dose (10mg/kg). Etoricoxib also impaired the learning and memory in rats as tested by passive avoidance and Morris water maze tests. ConclusionThe results of the present study suggest that use of etoricoxib, especially at low dose, in patients with epilepsy may not be detrimental with regard to seizure control. However, attention should be paid to cognitive parameters.

Atorvastatin prevents development of kindling by modulating hippocampal levels of dopamine, glutamate, and GABA in mice

PurposeAtorvastatin (ATV) is widely used for the treatment of dyslipidemias. Recent evidence has shown that ATV has protection effects against seizures. However, the effect of ATV on certain neurotransmitter and oxidative stress markers associated with seizures had not been reported. Therefore, the present study aimed to evaluate the effects of ATV on oxidative stress markers on whole brain and GABA, glutamate, and dopamine levels in the hippocampus of PTZ-kindled mice. Additionally, effects of ATV on animal models of seizures, anxiety, and depression were also assessed. Materials and methodsSwiss albino mice were given ATV (20, 40, and 80mg/kg/p.o.) in an acute study. On the seventh day, animals were subjected to various neurological and neurobehavioral tests, viz, increasing current electroshock (ICES) test, pentylenetetrazole (PTZ)-induced seizures, Elevated Plus Maze (EPM), and Forced Swim Test (FST). For the development of kindling, a subconvulsant dose of PTZ, i.e., 25mg/kg, i.p., was administered every other day, and ATV in all the three doses was administered daily. Seizure score was continuously monitored until the development of kindling. Thiobarbituric acid reacting species (TBARS), glutathione, dopamine, GABA, and glutamate levels were also assessed in the brain tissues of mice. ResultsThe results showed that in the ICES test, ATV 80mg/kg increased the seizure threshold to hind limb extension (HLE), and a complete protection against HLE was observed when ATV 80mg/kg was combined with a subanticonvulsant dose of phenytoin. Atorvastatin in all the tested doses suppressed the development of kindling, reduced lipid peroxidation, and increased glutathione levels. All doses of ATV maintained the normal levels of glutamate, GABA, and dopamine in kindled mice. ConclusionAtorvastatin possesses anticonvulsant activity against electroconvulsions. It was found to suppress the development of PTZ kindling, presumably altering the redox status and hippocampal levels of dopamine, glutamate, and GABA.

Adjuvant Anticholinesterase Therapy for the Management of Epilepsy‐Induced Memory Deficit: A Critical Pre‐clinical Study

Epilepsy is one of the major neurological disorders still awaiting safer drugs with improved antiepileptic effect and lesser side effects. Apart from epilepsy itself, AEDs also have been shown to induce cognitive impairment in patients with epilepsy. There are limited data for the treatment of this menace. As cholinergic approach has widely been practiced for the restoration of memory in various neurodegenerative disorders, this study was envisaged to evaluate add on effect of acetylcholinesterase inhibitor (tacrine) with phenytoin in pentylenetetrazole-kindling-induced learning and memory deficit in mice. In this study, mice were kindled using subconvulsive dose of pentylenetetrazole (35mg/kg, i.p.; at interval of 48±2hr) and successfully kindled animals were divided into different groups and treated with vehicle, phenytoin and phenytoinin in combination with tacrine (0.3mg/kg), atropine (1mg/kg) and tacrine + atropine. Effect of different interventions on learning and memory was evaluated using elevated plus maze and passive shock avoidance on days 5, 10, 15 and 20. Phenytoin-treated kindled animals were associated with learning and memory deficit, while tacrine supplementation improved memory deficit with increased seizure severity score. Atropine treatment significantly reversed the protective effect of tacrine. Neurochemical findings also support the behavioural finding of the study. Our results suggest the use of anticholinesterases, with better seizure tolerance, for the management of cognitive impairment of epilepsy, as adjunct therapy.

Metformin protects against seizures, learning and memory impairments and oxidative damage induced by pentylenetetrazole-induced kindling in mice

Cognitive impairment, the most common and severe comorbidity of epilepsy, greatly diminishes the quality of life. However, current therapeutic interventions for epilepsy can also cause untoward cognitive effects. Thus, there is an urgent need for new kinds of agents targeting both seizures and cognition deficits. Oxidative stress is considered to play an important role in epileptogenesis and cognitive deficits, and antioxidants have a putative antiepileptic potential. Metformin, the most commonly prescribed antidiabetic oral drug, has antioxidant properties. This study was designed to evaluate the ameliorative effects of metformin on seizures, cognitive impairment and brain oxidative stress markers observed in pentylenetetrazole-induced kindling animals. Male C57BL/6 mice were administered with subconvulsive dose of pentylenetetrazole (37mg/kg, i.p.) every other day for 14 injections. Metformin was injected intraperitoneally in dose of 200mg/kg along with alternate-day PTZ. We found that metformin suppressed the progression of kindling, ameliorated the cognitive impairment and decreased brain oxidative stress. Thus the present study concluded that metformin may be a potential agent for the treatment of epilepsy as well as a protective medicine against cognitive impairment induced by seizures.

Characterization of a Lamotrigine‐Resistant Kindled Model of Epilepsy in Mice: Evaluation of Drug Resistance Mechanisms

The aims of this study were to characterize a lamotrigine-resistant kindled model of epilepsy in mice, to study the anticonvulsant effect of carbamazepine (CBZ) and valproic acid (VPA), and to probe into the mechanism for resistance. Swiss albino mice were kindled by a subconvulsive dose of pentylenetetrazole (PTZ, 30mg/kg, i.p., every other day for 6weeks). The mice were pre-treated (30min.) either with a low dose of LTG (5mg/kg, i.p.) or with vehicle, and the seizures were scored. The acute treatment with LTG (15mg/kg, i.p.) on the last day blocked seizure in the vehicle-treated group, but the LTG pre-treated group showed resistance. This resistance was extended to CBZ, but not to VPA. The resistant model was successfully replicated in mice with less kindling development time (6weeks versus 9weeks 5days in rats). A highly significant decrease in the level of histamine (p<0.001) was found, and there were also decreases in serotonin, GABA and AChE levels (p<0.05). A significantly low level of histamine correlates with drug resistance and indicates involvement of the H1/H3 receptors. It is suggested that the selective action on voltage-gated Na(+) and Ca(2+) channels could explain the differences in the sensitivity of CBZ and VPA.

Ameliorative effect of Curcumin on seizure severity, depression like behavior, learning and memory deficit in post-pentylenetetrazole-kindled mice

Epilepsy is a chronic neurological disorder and generally associated with certain psychiatric comorbidities. Among several comorbidities depressive behavior and cognitive impairment has been reported to be most debilitating comorbidity associated with epilepsy. This study was envisaged to evaluate the ameliorative effect of Curcumin on depression like behavior and cognitive impairment observed in pentylenetetrazole kindled animals. Male Swiss Albino mice were kindled with subconvulsive dose of pentylenetetrazole (35mg/kg, i.p.). Successfully kindled animals were used in the study to observe the effect of different treatments. Treatment groups received phenytoin (30mg/kg) and Curcumin (50, 100 and 200mg/kg) for 15 days. The animals were challenged with pentylenetetrazole (35mg/kg, i.p.) on day 5, 10 and 15 and seizure severity score, immobility period, number of mistakes and step down latency were recorded. On 15th day, all the animals were sacrificed after behavioral evaluations and their brain was isolated and homogenized to estimate brain norepinephrine, serotonin, total nitrite level and acetylcholinesterase activity. Phenytoin treatment significantly improved the depressive like behavior along with its anticonvulsant effect, however was unable to improve memory impairment. Curcumin significantly attenuated seizure severity, depression like behavior and memory impairment in kindled animals, in dose dependent manner. These results were supported by the biochemical modulation of brain monoamine, nitrosative stress level and acetylcholinesterase activity. Thus present study concluded that Curcumin has the ameliorative effect on seizure severity, depression like behavior and memory impairment in pentylenetetrazole kindled mice, possibly via central monoaminergic modulation and inhibitory effect on nitrosative stress and acetylcholinesterase activity.

Overexpression of multidrug resistance-associated protein 2 in the brain of pentylenetetrazole-kindled rats

Clinical studies and animal models have shown that pharmacoresistant epilepsy is partly due to the overexpression of ATP-binding cassette transporters at the brain. The purposes of the study were to investigate the function and expression of multidrug resistance-associated protein 2 (Mrp2) in the brain of pentylenetetrazole (PTZ)-kindled rats, and the effect of the altered Mrp2 function and expression on phenytoin (PHT) distribution in the brain. Kindled rats were developed by sub-convulsive dose of PTZ (33mg/kg, every day, intraperitoneal (i.p.)) for 28days. Mrp2 expression and function were measured by western blot and bromosulfophthalein (BSP) distribution in the brain. PHT concentrations in the brain of PTZ-kindled rats were measured alone or with co-administration of probenecid (50mg/kg). Further experiment was designed to investigate whether PHT treatment prevented the up-regulated brain Mrp2 expression and function induced by PTZ-kindling. The results showed that PTZ-kindling resulted in an increase of Mrp2 level in the hippocampus and cortex of rats, accompanied by significant decreases in the brain-to-plasma concentration ratio of BSP. PTZ-kindling also decreased PHT levels in the hippocampus and cortex without altering PHT concentrations in plasma, resulting in a lower brain-to-plasma concentration ratio of PHT. Co-administration of probenecid increased the brain-to-plasma ratio of BSP and PHT in the brain of both normal and PTZ-kindled rats. A 14-day PHT treatment prevented the up-regulation of Mrp2 expression and function induced by PTZ-kindling, accompanied by increases of PHT concentrations in the brain and good anticonvulsive effects. The present study demonstrated that chronic PTZ-kindling increased Mrp2 expression and function in the rat brain, and the up-regulation partly came from epileptic seizure.

Influence of calcium channel blockers on anticonvulsant and antinociceptive activities of valproic acid in pentylenetetrazole-kindled mice

BackgroudComorbidities of epilepsy comprise some pain disorders, including acute nociceptive pain, therefore, antiepileptic drugs can prove efficacy in the management of this kind of pain albeit with several adverse reactions. The current study aimed to evaluate the modulatory effects of calcium channel blockers on the anticonvulsant and antinociceptive effects of valproic acid (VPA) in pentylenetetrazole (PTZ)-kindled mice. MethodsKindled mice were treated with 20mg/kg (ip) of diltiazem, nifedipine, or verapamil, then VPA (200mg/kg, ip) at 30min intervals before PTZ administration (35mg/kg, ip). ResultsOur data demonstrated that the three calcium channel blockers afforded a protection against sub-convulsive doses of PTZ. Their protective effects were comparable to that exerted by the standard antiepileptic drug, VPA. The anticonvulsant activity of VPA was further enhanced by its combination with diltiazem. Also, PTZ-kindling reduced pain-threshold as evaluated by hot plate anal-gesimeter and acetic acid-induced writhing test. Although the repeated administration of VPA significantly increased pain-threshold in kindled mice, it was not able to normalize it. Similar results were obtained with diltiazem and nifedipine. Interestingly, combination of diltiazem or nifedipine with VPA elicited the most profound antinociceptive effect in kindled mice. ConclusionsThese results demonstrate for the first time the beneficial role of some calcium channel blockers in combination with VPA in the management of acute nociceptive pain. Therapeutically, this enhancing profile for calcium channel blockers fosters a safer and more effective drug-combination regimen than valproic acid alone.

Enhanced susceptibility to the GABA antagonist pentylenetetrazole during the latent period following a pilocarpine-induced status epilepticus in rats

A variety of acute brain insults bear the risk of subsequent development of chronic epilepsy. Enhanced understanding of the brain alterations underlying this process may ultimately lead to interventions that prevent, interrupt or reverse epileptogenesis in people at risk. Various interventions have been evaluated in rat models of symptomatic epilepsy, in which epileptogenesis was induced by status epilepticus (SE) or traumatic brain injury (TBI). Paradoxically, recent data indicated that administration of proconvulsant drugs after TBI or SE exerts antiepileptogenic or disease-modifying effects, although epilepsy is often considered to represent a decrease in seizure threshold. Surprisingly, to our knowledge, it is not known whether alterations in seizure threshold occur during the latent period following SE. This prompted us to study seizure threshold during and after the latent period following SE induced by lithium/pilocarpine in rats. Timed intravenous infusion of the GABAA receptor antagonist pentylenetetrazole (PTZ) was used for this purpose. The duration of the latent period was determined by continuous video/EEG monitoring. Compared to control seizure threshold determined before SE, threshold significantly decreased two days after SE, but returned to pre-SE control thereafter. Moreover, the duration of PTZ-induced seizures was significantly increased throughout the latent period, which ranged from 6 to 10 days after SE. This increased susceptibility to PTZ likely reflects the complex alterations in GABA-mediated transmission that occur during the latent period following SE. The data will allow developing dosing regimens for evaluation of whether treatment with subconvulsant doses of PTZ during the latent period affects the development of epilepsy.

Anticonvulsant potential of the peroxisome proliferator-activated receptor gamma agonist pioglitazone in pentylenetetrazole-induced acute seizures and kindling in mice

Pioglitazone, a peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist, is used in inflammatory brain diseases, and it was shown to protect against seizures in genetically epileptic mice. The present study, therefore, verified its potential antiepileptic effect in pentylenetetrazole (PTZ)-induced acute seizures and kindling in mice. Kindling was induced in male Swiss albino mice using a subconvulsive dose of PTZ (40mg/kg, i.p., on alternate days) for 17days, while acute epileptic animals received a single dose of PTZ (60mg/kg, i.p.). Animals were pretreated with either pioglitazone (10mg/kg, p.o.) or the standard antiepileptic drug valproate (50mg/kg, p.o.). Kindled mice showed elevated cortical levels of TNF-α, IL-10, PGE2, and caspase-3, while acute PTZ increased only the cytokines. However, inducible nitric oxide synthase (iNOS) was not expressed in the hippocampi of both acutely convulsed and kindled animals. In acute PTZ convulsion, as well as kindled mice, pioglitazone and valproate protected against PTZ-induced seizures and delayed seizure latency onset. Pioglitazone normalized all altered parameters except for PGE2 in PTZ-kindled animals and, unpredictably, further elevated TNF-α in the acute model. Valproate showed also the same pattern but reinstated IL-10 partially in kindled mice. The present results revealed that both models increase pro- and anti-inflammatory cytokines, while only kindling elevates PGE2 and caspase-3; nonetheless, neither model affects the expression of iNOS. The anticonvulsive effect of either pioglitazone or valproate is presumably associated with attenuating inflammation and preventing apoptosis.

Neuroprotective effect of progesterone on acute phase changes induced by partial global cerebral ischaemia in mice

The possible neuroprotective effect of progesterone, a steroid hormone, on acute phase changes in a mouse model of cerebral ischaemia induced by bilateral common carotid artery occlusion (BCAO) was studied. A total of 72 male mice were included in the study. The BCAO model was used to induce partial global cerebral ischaemia. Morphological assessment included measurement of infarct size and brain oedema. Post-ischaemic seizure susceptibility was assessed using a subconvulsive dose of pentylenetetrazole (30 mgkg(-1) i.p.). Biochemical estimations included tumour necrosis factor alpha (TNF-alpha) levels and enzyme parameters such as lipid peroxidation, superoxide dismutase, catalase and glutathione peroxidase, and protein estimation. BCAO induced a significant infarct size and oedema in the saline-treated control group, along with an increase in oxidative stress, indicated by increased lipid peroxidation and decreased levels of antioxidants such as superoxide dismutase, catalase and glutathione peroxidase. Progesterone (15 mgkg(-1) i.p.) administration showed a neuro-protective effect by significantly reducing the cerebral infarct size as compared with the control group. Post-ischaemic seizure susceptibility was also reduced as the number of positive responders decreased. Brain oedema subsided, but not significantly. Progesterone significantly reduced TNF-alpha levels compared with the ischaemia group. Progesterone improved levels of all the antioxidants, indicating activity against oxidative stress induced by BCAO. The results demonstrate the neuroprotective effect of progesterone against ischaemic insult, suggesting a role for the steroid as a neuroprotective agent.