Neurochemical evidence based suggested therapy for safe management of epileptogenesis

Most of the clinically available antiepileptic drugs have only antiseizure effects and are reported unable to prevent epileptogenesis. In the past decade, several drugs underwent clinical trials for management of epileptogenesis, but none of the drugs tested was found effective. One of the major lacunas is availability of appropriate preclinical approaches to delineate mechanisms of epileptogenesis. Thus, the present study attempts to suggest a neurochemistry based approach for safe management of epileptogenesis. The altered neurochemical milieu in amygdala, cortex and hippocampus areas of the mice brain in naïve, kindled and kindling resistant animals has been delineated. The endogenous natural antiepileptogenic neurochemical defense mechanism observed in kindling resistant animals may uncover neurochemical mechanisms of epileptogenesis and in turn suggest us novel interventions for safe management of epileptogenesis. The kindling epileptogenesis was carried out in two month old male Swiss albino mice by administering subconvulsive pentylenetetrazole (35 mg/kg; i.p.) at an interval of 48 ± 2 h for 42 days. 2 h after the last pentylenetetrazole injection, the animals were subjected to behavioral evaluations. Four hours after behavioral evaluation, all animals were euthanized and discrete parts of brain (amygdala, cortex and hippocampus) were harvested for neurochemical analysis. Results revealed that 60% of animals responded to kindling as observed with decreased seizure threshold, while the rest were found resistant. The kindled animals were found to be associated with anxiety, depression and cognitive impairment; while in kindling resistant animals no such behavioral deficits were observed. The neurochemical analysis revealed that in kindled animals altered glutamate–GABA neurotransmission, and decreased taurine, glycine, d-serine, monoamine levels with elevated indoleamine 2,3-dioxygenase activity were observed, which may be convicted for progression of kindling epileptogenesis. However, in kindling resistant animals elevated GABA, taurine, tryptophan, serotonin, glycine, and d-serine levels with decreased indoleamine 2,3-dioxygenase activity were observed as natural endogenous antiepileptogenic mechanisms, which may be foreseen as safe pharmacological targets for management of epileptogenesis.     

The effect of l-arginine and l-NAME on pentylenetetrazole induced seizures in ovariectomized rats,an in vivo study

The role of ovarian hormones and nitric oxide (NO) on seizure and their interaction have been widely investigated. The present study carried out to evaluate the effect of chronic administration of l-arginine (lA) and l-NAME (lN) on pentylenetetrazole (PTZ) induced epilepsy in ovariectomized (OVX) and naïve female rats.Fourty-eight female rats were randomly divided into six groups (n = 8) as follows: (1) sham, (2) ovarectomized (OVX), (3) sham-lA, (4) sham-lN, (5) OVX-lA, and (6) OVX-lN.The animals of sham-lA and OVX-lA received daily injection of 500 mg/kg l-arginine (i.p.) during 4 weeks. Sham-lN and OVX-lN were treated by 10 mg/kg l-NAME (i.p.) daily for 4 weeks. The animals of sham and OVX groups received 1 ml/kg saline (i.p.) instead of l-arginine and l-NAME. The latencies to minimal clonic seizures (MCS) and generalized tonic–clonic seizures (GTCS) after intraperitoneal injection of penetylenetetrazole (PTZ, 90 mg/kg) was recorded and compared between groups.A significant increase in the GTCS, but not MCS, latency was seen in OVX rats in comparison with sham-operated animals. Pretreatment of animals with l-NAME resulted in a significant increase in the GTCS and MCS latencies in sham group while no significant effects were seen in OVX rats. On the contrary, while pretreatment with l-arginine had no effects on MCS and GTCS latencies in sham group, a significant decrease in GTCS latency was observed in OVX rats.It is concluded that ovarian sex hormones affect seizure thresholds induced by PTZ and NO has a role on seizures susceptibility following PTZ administration. This NO effect might be differing in the presence or absence of ovarian hormones, but further investigations need to be done.     

Effects of agomelatine on pentylenetetrazole-induced kindling,kindling-associated oxidative stress,and behavioral despair in mice and modulation of its actions by luzindole and 1-(m-chlorophenyl) piperazine

In view of well-evidenced antiepileptic effects of melatonin and few reports of anticonvulsant action of agomelatine, the present study investigated whether agomelatine protects against pentylenetetrazole (PTZ)-induced kindling in mice and kindling-associated oxidative stress, depression, and impairment of spatial memory. In order to explore whether effects are mediated by melatonergic or serotonergic mechanisms, 1-(m-chlorophenyl) piperazine (mCPP), selective 5HT2c receptor agonist and luzindole, melatonergic receptor antagonist, were taken as pharmacological tools. In view of few hepatotoxic reports on agomelatine, the study evaluated effects on hepatic enzyme levels. Swiss strain albino mice were injected with PTZ (25 mg/kg, i.p.) once every two days for 5 weeks to induce kindling. The effects of agomelatine (10 mg/kg, p.o.) alone and in combination with luzindole (2.5 mg/kg, i.p.) or mCPP (7 mg/kg, i.p.) on seizure severity during induction and % incidence of animals kindled at the end of 5 weeks were recorded. Modified forced swim test was used for studying depression-like behavior while spontaneous alternation behavior was used for studying effects on spatial memory. Serum AST and ALT concentrations, cortical and hippocampal malondialdehyde, and reduced glutathione were measured. Agomelatine 10 mg/kg, p.o. effectively delayed development of kindling, reduced seizure severity, and decreased % incidence. Luzindole reversed the protective effects of agomelatine while mCPP failed to show such a reversal, indicating melatonergic (and not serotonergic) mechanisms in the observed effects. Agomelatine also showed antioxidant effects that can partially contribute to its anticonvulsant action. In addition, it alleviated PTZ-kindling-associated behavioral despair and favorably modulated liver enzymes. Its effects on improvement of kindling-associated spatial memory could possibly be related to its effects on locomotor activity. Agomelatine, thus, could be explored as an adjunct to antiepileptic drugs for seizure control and for alleviating epilepsy-associated depression.     

Comparing sleep profiles between patients with juvenile myoclonic epilepsy and symptomatic partial epilepsy: Sleep questionnaire-based study

ObjectivesPatients with epilepsy commonly report excessive daytime sleepiness and daytime fatigue, which may be attributed to the direct effect of seizures, a side effect of antiepileptic drugs or a combination of the two. The aim of the study was to compare sleep profiles in patients with juvenile myoclonic epilepsy (JME) and symptomatic partial epilepsy (PE) in drug naïve and treated patients using standardized sleep questionnaires.MethodsThree study groups: - 1) juvenile myoclonic epilepsy (N = 40) [drug naïve (N = 20); On sodium valproate (SVA) (N = 20)]; 2) symptomatic partial epilepsy (N = 40) [drug naïve (N = 20); On carbamazepine (CBZ) (N = 20)]; 3) healthy controls (N = 40) completed 3 standardized sleep questionnaires – Epworth Sleepiness Scale, Pittsburgh Sleep Quality Index, and NIMHANS Comprehensive Sleep Disorders Questionnaire. Scores were compared using t-test and Chi-squared tests (P ≤ 0.005).ResultsThe mean PSQI scores as well as the proportion of subjects with abnormal PSQI scores were higher in patients with JME and PE compared to controls. Although the mean ESS scores were comparable between patients with epilepsy and controls, the percentage of patients with partial epilepsy having abnormal ESS scores was higher. No significant differences were present between drug naïve and treatment monotherapy groups. Excessive daytime somnolence was reported more often by patients with JME compared to patients with partial epilepsy and controls.ConclusionThis study found that patients with epilepsy have a higher prevalence of poor sleep quality compared to controls. Moreover, a significantly higher percentage of patients with partial epilepsy had higher ESS scores compared to healthy controls. However, there was no difference between ESS and PSQI scores between drug naïve and treated patients with JME or PE.SignificancePoor sleep quality is more prevalent in patients with epilepsy irrespective of the use of antiepileptic medications. Excessive daytime somnolence is more commonly seen in patients with partial epilepsy when compared to the general population.     

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) (30 mg/kg, i.p.), on alternating days until animals were fully kindled. After a one-week PTZ-free period, kindled rats were challenged with PTZ 30 mg/kg, and the latency, duration, and severity of seizures were recorded. Etoricoxib was then administered intraperitoneally at 1 mg/kg and 10 mg/kg in kindled rats for nine days (days 6–14). On the ninth day of etoricoxib treatment, PTZ challenge (30 mg/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 (1 mg/kg) had an anticonvulsant effect which was reduced or reversed at higher dose (10 mg/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.     

Cannabis use and callosal white matter structure and integrity in recent-onset schizophrenia

Adolescent-onset cannabis use, compared with adult-onset use, has been associated with a higher risk for developing symptoms of schizophrenia-like psychotic disorders. To test the hypothesis that onset of cannabis use in early adolescence in male schizophrenia patients is associated with abnormalities in white matter structure and integrity, we used high resolution structural and diffusion tensor brain images to compare three groups of patients: those who started regular use of cannabis (1) before the age of 15 years (early-onset cannabis users, n = 10) or (2) at the age of 17 years or later (late-onset cannabis users, n = 8), and (3) those who were cannabis naïve (n = 8). To verify patient findings, we also compared white matter integrity of the three patient groups with that of a healthy control group (n = 10). Cannabis naïve patients showed reduced white matter density and reduced fractional anisotropy, an indicator for white matter integrity, in the splenium of the corpus callosum compared with patients with early-onset cannabis use. In the same brain area, cannabis naïve patients showed reduced fractional anisotropy compared with healthy controls. Our results suggest that the age of onset of cannabis use is not an identifying characteristic for white matter abnormalities in schizophrenia patients; however, our results might indicate a more vulnerable brain structure in cannabis naïve schizophrenia patients.     

The antidepressant sertraline prevents the behavioral and EEG changes induced in two animal models of seizures

In order to investigate a potential anticonvulsive action of sertraline (i.p.), its effects on seizures, EEG epileptiform activity and EEG amplitude increases induced by two convulsive agents were evaluated and compared with the effects of carbamazepine. Around 20 min following 4-aminopyridine (4-AP, 2.5 mg/kg, i.p.), tonic-clonic seizures and epileptiform activity were observed in control animals. A single sertraline pre-injection of 2.5 mg/kg, but not of 0.75 mg/kg, prevented these changes to 4-AP. Repeated daily administration of 0.75 mg/kg for one week, however, effectively inhibited the changes induced by 4-AP. The first generalized tonic-clonic seizure and EEG changes in response to pentylenetetrazole (PTZ, 50 mg/kg, i.p.) were observed near the first minute in control animals. Single sertraline doses above 5 mg/kg prevented the PTZ-induced changes. Moreover, a single carbamazepine dose of 25 mg/kg (i.p.), but not of 15 mg/kg, prevented the changes induced by the above convulsive agents. An anti-seizure action of the antidepressant sertraline is strongly suggested by these findings.     

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.     

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.     

Blast neurotrauma impairs working memory and disrupts prefrontal myo-inositol levels in rats

Working memory, which is dependent on higher-order executive function in the prefrontal cortex, is often disrupted in patients exposed to blast overpressure. In this study, we evaluated working memory and medial prefrontal neurochemical status in a rat model of blast neurotrauma. Adult male Sprague–Dawley rats were anesthetized with 3% isoflurane and exposed to calibrated blast overpressure (17 psi, 117 kPa) while sham animals received only anesthesia. Early neurochemical effects in the prefrontal cortex included a significant decrease in betaine (trimethylglycine) and an increase in GABA at 24 h, and significant increases in glycerophosphorylcholine, phosphorylethanolamine, as well as glutamate/creatine and lactate/creatine ratios at 48 h. Seven days after blast, only myo-inositol levels were altered showing a 15% increase. Compared to controls, short-term memory in the novel object recognition task was significantly impaired in animals exposed to blast overpressure. Working memory in control animals was negatively correlated with myo-inositol levels (r = − .759, p < 0.05), an association that was absent in blast exposed animals. Increased myo-inositol may represent tardive glial scarring in the prefrontal cortex, a notion supported by GFAP changes in this region after blast overexposure as well as clinical reports of increased myo-inositol in disorders of memory.     

The evaluation of antimuscarinic-induced convulsions in fasted rats after food intake

The present study was performed to evaluate convulsions after food intake in fasted rats pretreated with scopolamine or atropine and to determine whether these convulsions respond to drugs found effective in fasted mice. Scopolamine (2.4 mg/kg) and atropine (2.4 mg/kg) were given intraperitoneally (i.p.) to rats fasted for 52 h. Both drugs induced convulsions after animals were allowed to eat ad lib. Another group of fasted rats pretreated with saline, MK-801 (0.1 mg/kg), clonidine (0.1 mg/kg), chlorpromazine (2 and 4 mg/kg), valproate (200 mg/kg), diazepam (1.5 and 2 mg/kg) or gabapentin (50 mg/kg) were treated i.p. with saline or scopolamine (2.4 mg/kg) and were allowed to eat ad lib. Clonidine, MK-801, chlorpromazine (4 mg/kg) and diazepam (2 mg/kg) reduced the incidence of scopolamine-induced convulsions in fasted rats. Gabapentin could only prolong the onset of convulsions. Neither treatment was effective against myoclonus of hindlimbs. Present results showed that fasted rats also develop antimuscarinic-induced convulsions which do not completely respond to treatments found effective in convulsions of fasted mice.     

Proton magnetic resonance spectroscopy in pediatric obsessive–compulsive disorder: Longitudinal study before and after treatment

Abnormalities in neurochemical compounds in obsessive–compulsive disorder (OCD) may help increase our knowledge of neurobiological abnormalities in the fronto-subcortical circuits. The aims of this exploratory study were to identify with in vivo magnetic resonance spectroscopy (¹H-MRS) the possible alterations in neurometabolites in a group of drug naïve children and adolescents with OCD in comparison with a control group and to determine whether there was any effect of treatment on the metabolite levels. Eleven OCD children and adolescents (age range 9–17 years; 6 male, 5 female) and twelve healthy subjects with similar age, sex and estimated intellectual quotient were studied. Proton magnetic resonance spectroscopy at 1.5 T was used. We placed 3 voxels, one bilaterally located involving anterior cingulate-medial frontal regions, and one in each striatal region involving the caudate and putaminal regions. Concentrations of creatine (Cr), myo-inositol (mI), total Cho (glycerophosphocholine + phosphocholine), total NAA (N-acetyl aspartate + N-acetyl aspartylglutamate), and total Glx (glutamate + glutamine) were calculated. We found significantly lower concentrations of total Cho in left striatum in OCD patients compared with healthy subjects. The difference in Cho concentrations in left striatum between the two groups did not change over time and persisted at follow-up assessment. Like the control subjects, OCD patients undergoing pharmacological treatment and clinical recovery showed no significant changes in neurometabolic activity between the first and second evaluations.     

Sabril® registry 5-year results: Characteristics of adult patients treated with vigabatrin

Vigabatrin (Sabril®), approved in the US in 2009, is currently indicated as adjunctive therapy for refractory complex partial seizures (rCPS) in patients ≥ 10 years old who have responded inadequately to several alternative treatments and as monotherapy for infantile spasms (IS) in patients 1 month to 2 years of age. Because of reports of vision loss following vigabatrin exposure, FDA approval required a risk evaluation mitigation strategy (REMS) program. Vigabatrin is only available in the US through Support, Help, And Resources for Epilepsy (SHARE), which includes a mandated registry. This article describes 5 years of demographic and treatment exposure data from adult patients (≥ 17 years old) in the US treated with vigabatrin and monitored in the ongoing Sabril® registry. Registry participation is mandatory for all US Sabril® prescribers and patients. A benefit–risk assessment must be documented by the physician for a patient to progress to maintenance therapy, defined as 1 month of vigabatrin treatment for patients with IS and 3 months for patients with rCPS. Ophthalmologic assessments must be documented during and after completion of therapy. As of August 26, 2014, a total of 6823 patients were enrolled in the registry, of which 1200 were adults at enrollment. Of these patients, 1031 (86%) were naïve to vigabatrin. The majority of adult patients (n = 783, 65%) had previously been prescribed ≥ 4 AEDs, and 719 (60%) were receiving ≥ 3 concomitant AEDs at vigabatrin initiation. Prescribers submitted an initial ophthalmological assessment form for 863 patients; an ophthalmologic exam was not completed for 300 (35%) patients and thus, were considered exempted from vision testing. Of these patients, 128 (43%) were exempted for neurologic disabilities. Clinicians discontinued treatment in 8 patients because of visual field deficits (VFD) (5 patients naïve to vigabatrin and 3 patients previously exposed). Based on Kaplan–Meier survival estimates, it is estimated that approximately 71%, 55%, and 40% of adult patients naïve to vigabatrin would remain in the registry at 3, 6, and 12 months, respectively. These demographic data suggest that a proportion of adult patients remain on vigabatrin long-term despite the risks of adverse events and significant underlying AED resistance and neurologic disease.     

Probenecid treatment enhances retinal and brain delivery of N-4-benzoylaminophenylsulfonylglycine: An anionic aldose reductase inhibitor

Anion efflux transporters are expected to minimize target tissue delivery of N-[4-(benzoylaminophenyl)sulfonyl]glycine (BAPSG), a novel carboxylic acid aldose reductase inhibitor, which exists as a monocarboxylate anion at physiological conditions. Therefore, the objective of this study was to determine whether BAPSG delivery to various eye tissues including the retina and the brain can be enhanced by probenecid, a competitive inhibitor of anion transporters. To determine the influence of probenecid on eye and brain distribution of BAPSG, probenecid was administered intraperitoneally (120 mg/kg body weight; i.p.) 20 min prior to BAPSG (50 mg/kg; i.p.) administration. Drug disposition in various eye tissues including the retina and the brain was determined at 15 min, 1, 2 and 4 h after BAPSG dose in male Sprauge–Dawley rats. To determine whether probenecid alters plasma clearance of BAPSG, influence of probenecid (120 mg/kg; i.p.) on the plasma pharmacokinetics of intravenously administered BAPSG (15 mg/kg) was studied as well. Finally, the effect of probenecid co-administration on the ocular tissue distribution of BAPSG was assessed in rabbits following topical (eye drop) administration. Following pretreatment with probenecid in the rat study, retinal delivery at 1 h was increased by about 11-fold (2580 ng/g vs. 244 ng/g; p < 0.05). Further, following probenecid pretreatment, significant BAPSG levels were detectable in the brain (45 ± 20 ng/g) at 1 h, unlike controls where the drug was not detectable. Plasma concentrations, plasma elimination half-life, and total body clearance of intravenously administered BAPSG were not altered by i.p. probenecid pretreatment. In the topical dosing study, a significant decline in BAPSG delivery was observed in the iris–ciliary body but no significant changes were observed in other tissues of the anterior segment of the eye including tears. Thus, inhibition of anion transporters is a useful approach to elevate retinal and brain delivery of BAPSG.     

Anticonvulsant effect of dextrometrophan on pentylenetetrazole-induced seizures in mice: Involvement of nitric oxide and N-methyl-d-aspartate receptors

Dextrometrophan (DM), widely used as an antitussive, has recently generated interest as an anticonvulsant drug. Some effects of dextrometrophan are associated with alterations in several pathways, such as inhibition of nitric oxide synthase (NOS) enzyme and N-methyl d-aspartate (NMDA) receptors. In this study, we aimed to investigate the anticonvulsant effect of acute administration of dextrometrophan on pentylenetetrazole (PTZ)-induced seizures and the probable involvement of the nitric oxide (NO) pathway and NMDA receptors in this effect. For this purpose, seizures were induced by intravenous PTZ infusion. All drugs were administrated by intraperitoneal (i.p.) route before PTZ injection. Our results demonstrate that acute DM treatment (10–100 mg/kg) increased the seizure threshold. In addition, the nonselective NOS inhibitor L-NAME (10 mg/kg) and the neural NOS inhibitor, 7-nitroindazole (40 mg/kg), at doses that had no effect on seizure threshold, augmented the anticonvulsant effect of DM (3 mg/kg), while the inducible NOS inhibitor, aminoguanidine (100 mg/kg), did not affect the anticonvulsant effect of DM. Moreover, the NOS substrate l-arginine (60 mg/kg) blunted the anticonvulsant effect of DM (100 mg/kg). Also, NMDA antagonists, ketamine (0.5 mg/kg) and MK-801 (0.05 mg/kg), augmented the anticonvulsant effect of DM (3 mg/kg). In conclusion, we demonstrated that the anticonvulsant effect of DM is mediated by a decline in neural nitric oxide activity and inhibition of NMDA receptors.     

Effects of d-penicillamine on pentylenetetrazole-induced seizures in mice: Involvement of nitric oxide/NMDA pathways

Besides the clinical applications of penicillamine, some reports show that use of d-penicillamine (d-pen) has been associated with adverse effects such as seizures. So, the purpose of this study was to evaluate the effects of d-pen on pentylenetetrazole (PTZ)-induced seizures in male NMRI mice. It also examined whether N-methyl-d-aspartate (NMDA) receptor/nitrergic system blockage was able to alter the probable effects of d-pen.Different doses of d-pen (0.1, 0.5, 1, 10, 100, 150, and 250 mg/kg) were administered intraperitoneally (i.p.) 90 min prior to induction of seizures. d-Penicillamine at a low dose (0.5 mg/kg, i.p.) had anticonvulsant effects, whereas at a high dose (250 mg/kg, i.p.), it was proconvulsant. Both anti- and proconvulsant effects of d-pen were blocked by a single dose of a nonspecific inhibitor of nitric oxide synthase (NOS), l-NAME (10 mg/kg, i.p.), and a single dose of a specific inhibitor of neuronal nitric oxide synthase (nNOS), 7-nitroindazole (30 mg/kg, i.p.). A selective inhibitor of iNOS, aminoguanidine (100 mg/kg, i.p.), had no effect on these activities. An NMDA receptor antagonist, MK-801 (0.05 mg/kg, i.p.), alters the anti- and proconvulsant effects of d-pen.The results of the present study showed that the nitric oxide system and NMDA receptors may contribute to the biphasic effects of d-pen, which remain to be clarified further.     

ATP-sensitive potassium channels contribute to the time-dependent alteration in the pentylenetetrazole-induced seizure threshold in diabetic mice

Although there is evidence that diabetes affects seizure susceptibility, the underlying mechanism has not been completely understood. Several studies also suggest a pivotal role for K_ATP channels in the seizure modulation. The aim of the present study was to evaluate the seizure threshold induced by pentylenetetrazole in diabetic mice at different times (3 days, 1–8 weeks) after induction of diabetes with streptozocin and to examine the possible role of ATP-sensitive potassium (K_ATP) channels in this manner.Our data showed a time-dependent alteration in the threshold in diabetic mice, reaching a peak on week 2 after streptozocin injection and declining significantly afterwards. The seizure threshold in 8-week diabetic mice was even lower than control levels, though the difference was not significant. The K_ATP channel opener cromakalim (0.1–30 μg/kg, i.p.) significantly increased the seizure threshold in control mice. Although the K_ATP channel blocker glibenclamide (0.5, 1 mg/kg) had no effect, it prevented the effects of the potent dose of cromakalim (30 μg/kg) on seizure threshold in control mice. Glibenclamide (1 mg/kg, i.p.) also decreased the seizure threshold in 2-week diabetic mice to the control levels which was blocked by pre-treatment with cromakalim (10 μg/kg, i.p.). Cromakalim (10 μg/kg, i.p.) significantly increased the seizure threshold in 8-week diabetic mice which was inhibited by pre-treatment with glibenclamide (1 mg/kg, i.p.).We demonstrated a time-dependent alteration in the pentylenetetrazole-induced seizure threshold in diabetic mice. This phenomenon might be due to the probable alteration in the K_ATP channel functioning during the diabetic condition.     

Postnatal caffeine treatment affects differently two pentylenetetrazol seizure models in rats

Effects of repeated postnatal administration of caffeine (10 and 20 mg/kg s.c. daily from P7 to P11) were studied in two models of epileptic seizures characterized by spike-and-wave EEG rhythm in 18- and 25-day-old rats. Rhythmic metrazol activity (RMA, model of human absences) was induced by low dose of pentylenetetrazol (PTZ, 20 mg/kg or 40 mg/kg, i.p.) and minimal clonic seizures (model of human myoclonic seizures) by two successive doses of PTZ (20 and 40 mg/kg i.p.). Early postnatal caffeine treatment resulted in significant changes of RMA only in 18-day-old rats. Anticonvulsant effects were observed in RMA episodes elicited by the 20-mg/kg dose of PTZ in both caffeine groups whereas latency of RMA episodes induced by the 40-mg/kg dose was shortened and their duration was prolonged. No changes were found in 25-day-old animals. Incidence, EEG and motor pattern of minimal clonic seizures were not changed. Some animals in both control age groups exhibited transition to generalized tonic–clonic seizures. This type of seizures never appeared in caffeine-treated 25-day-old animals. Mixed effects of postnatal caffeine exposure were demonstrated; these predominantly anticonvulsant effects are age- and model-specific.     

The effects of valproate exposure in utero on behavior and the need for educational support in school-aged children

Children exposed to valproate monotherapy in utero were evaluated with respect to neurological functioning, behavior, and additional educational needs, and the results were compared with those for age- and gender-matched controls exposed to carbamazepine and children with no prenatal exposure to antiepileptic drugs. We identified from the community-based pregnancy registry of Kuopio University Hospital area (1989–2000) all first-born and school-aged children exposed to valproate (N = 13). Neurological and neuropsychological assessments were made clinically, and behavioral problems were assessed with the Conners’ Teacher Rating Scale (CTRS). Eight children (62%) exposed to valproate and two (15%) each in the carbamazepine-exposed and nonexposed groups (P = 0.022) required educational support. Minor dysmorphic features were noted in eight children (62%) exposed to valproate and in three children (23%) each in the carbamazepine-exposed and nonexposed groups. On CTRS, children exposed to valproate received higher scores, indicating behavioral problems. In our small but population-based study, all children exposed to valproate had minor, and some of them major, cognitive or neurological problems. This difference is clearly observed when assessing each child individually, but the many confounding factors explaining at least part of this difference are difficult to control and avoid in clinical practice. Larger studies with a prospective design are needed to confirm these findings.     

Water maze impairments after combined depletion of somatostatin and serotonin in the rat

This study examined the effect of both separate and combined depletion of brain somatostatin and serotonin on acquisition of the water maze (WM) task. Naïve male Long-Evans rats received injections of p-chlorophenylalanine (PCPA; 500 mg/kg × 2) to deplete serotonin or cysteamine (90 or 200 mg/kg) to deplete somatostatin, or both treatments prior to spatial and reversal training in the water maze. Some rats first received Morris’ nonspatial pretraining to train them in the behavioral strategies that are required for successful spatial place learning in this task, prior to drug treatment and spatial training. A detailed behavioral analysis indicated that somatostatin or serotonin depletion alone caused little or no impairment in naïve animals. Depletion of both somatostatin and serotonin in naïve rats impaired performance, with differences in the impairments that depended on the dose of cysteamine. Nonspatially pretrained rats were not impaired. Thus, neither somatostatin nor serotonin alone is crucial for the water maze task, but impairments occur if both somatostatin and serotonin are depleted in naïve rats. The results indicate that some of the performance impairment was due to strategies impairment rather than a spatial place learning impairment. Depletion of both somatostatin and serotonin in naïve rats produces results comparable to the spatial navigation deficits seen in some Alzheimer patients and suggests that combinations of antagonist treatments may better model this disorder than single antagonist treatments do.