Seizure Susceptibility In Rats Research Articles

Seizure Susceptibility and Sleep Disturbance as Biomarkers of Epileptogenesis after Experimental TBI.

Objectives: We investigated whether seizure susceptibility increases over weeks–months after experimental traumatic brain injury (TBI), and whether seizure susceptibility in rats predicts the development of post-traumatic epilepsy (PTE) or epileptiform activity. We further investigated whether rats develop chronic sleep disturbance after TBI, and whether sleep disturbance parameters—alone or in combination with pentylenetetrazol (PTZ) test parameters—could serve as novel biomarkers for the development of post-traumatic epileptogenesis. Methods: TBI was induced in adult male Sprague-Dawley rats with lateral fluid-percussion injury. Sham-operated experimental controls underwent craniectomy without exposure to an impact force. Seizure susceptibility was tested with a PTZ test (30 mg/kg, intraperitoneally) on day (D) 30, D60, D90, and D180 after TBI (n = 28) or sham operation (n = 16) under video electroencephalogram (vEEG). In the 7th post-injury month, rats underwent continuous vEEG monitoring to detect spontaneous seizures and assess sleep disturbances. At the end of the experiments, rats were perfused for brain histology. Results: In the TBI group, the percentage of rats with PTZ-induced seizures increased over time (adjusted p < 0.05 compared with D30). Combinations of three PTZ test parameters (latency to the first epileptiform discharge (ED), number of EDs, and number of PTZ-induced seizures) survived the leave-one-out validation for differentiating rats with or without epileptiform activity, indicating an area under the receiver operating curve (AUC) of 0.743 (95% CI 0.472–0.992, p = 0.05) with a misclassification rate of 36% on D90, and an AUC of 0.752 (95% CI 0.483–0.929, p < 0.05) with a misclassification rate of 32% on D180. Sleep analysis revealed that the number of transitions to N3 or rapid eye movement (REM) sleep, along with the total number of transitions, was increased in the TBI group during the lights-on period (all p < 0.05). The sleep fragmentation index during the lights-on period was greater in the TBI rats than in sham-operated rats (p < 0.05). A combination of sleep parameters showed promise as diagnostic biomarkers of prior TBI, with an AUC of 0.792 (95% CI 0.549–0.934, p < 0.01) and a misclassification rate of 28%. Rats with epilepsy or any epileptiform activity had more transitions from N3 to the awake stage (p < 0.05), and the number of N3–awake transitions differentiated rats with or without epileptiform activity, with an AUC of 0.857 (95% CI 0.651–1.063, p < 0.01). Combining sleep parameters with PTZ parameters did not improve the biomarker performance. Significance: This is the first attempt to monitor the evolution of seizure susceptibility over months in a well-described rat model of PTE. Our data suggest that assessment of seizure susceptibility and sleep disturbance can provide diagnostic biomarkers of prior TBI and prognostic biomarkers of post-traumatic epileptogenesis.

Experimental chronic sleep fragmentation alters seizure susceptibility and brain levels of interleukins 1β and 6.

Brain hyperexcitability in sleep apnea is believed to be provoked by hypoxemia, but sleep fragmentation can also play a significant role. Sleep fragmentation can trigger inflammatory mechanisms. The aim of this research was to investigate the effects of chronic sleep fragmentation on seizure susceptibility and brain cytokine profile. Chronic sleep fragmentation in male rats with implanted EEG electrodes was achieved by the treadmill method. Rats were randomized to: treadmill control (TC); activity control (AC) and sleep fragmentation (SF) group. Convulsive behavior was assessed 14 days later by seizure incidence, latency time and seizure severity during 30 min following lindane administration. The number and duration of EEG ictal periods were determined. Levels of IL-1β and IL-6 were measured in the animals' serum and brain structures (hippocampus, thalamus and cerebral cortex), in separate rat cohort that underwent the same fragmentation protocol except lindane administration. Incidence and severity of seizures were significantly increased, while latency was significantly decreased in SF+L compared with TC+L group. Seizure latency was also significantly decreased in SF+L compared to AC+L group. The number and duration of ictal periods were increased in the SF+L compared to the AC+L group. IL-1β was significantly increased in the thalamus, cortex and hippocampus in the SF compared to the AC and TC groups. IL-6 was statistically higher only in the cortex of SF animals, while in the thalamic or hippocampal tissue, no difference was observed between the groups. It could be concluded that fourteen-day sleep fragmentation increases seizure susceptibility in rats and modulates brain production of IL-1β and IL-6. Brain hyperexcitability in sleep apnea is believed to be provoked by hypoxemia, but sleep fragmentation can also play a significant role. Sleep fragmentation can trigger inflammatory mechanisms. The aim of this research was to investigate the effects of chronic sleep fragmentation on seizure susceptibility and brain cytokine profile. Chronic sleep fragmentation in male rats with implanted EEG electrodes was achieved by the treadmill method. Rats were randomized to: treadmill control (TC); activity control (AC) and sleep fragmentation (SF) group. Convulsive behavior was assessed 14 days later by seizure incidence, latency time and seizure severity during 30 min following lindane administration. The number and duration of EEG ictal periods were determined. Levels of IL-1β and IL-6 were measured in the animals’ serum and brain structures (hippocampus, thalamus and cerebral cortex), in separate rat cohort that underwent the same fragmentation protocol except lindane administration. Incidence and severity of seizures were significantly increased, while latency was significantly decreased in SF+L compared with TC+L group. Seizure latency was also significantly decreased in SF+L compared to AC+L group. The number and duration of ictal periods were increased in the SF+L compared to the AC+L group. IL-1β was significantly increased in the thalamus, cortex and hippocampus in the SF compared to the AC and TC groups. IL-6 was statistically higher only in the cortex of SF animals, while in the thalamic or hippocampal tissue, no difference was observed between the groups. It could be concluded that fourteen-day sleep fragmentation increases seizure susceptibility in rats and modulates brain production of IL-1β and IL-6.

Effect of fluoxetine on seizures in rats with high susceptibility to audiogenic stress

The seizures, triggered by a loud sound in laboratory animals, are associated with the imbalance of the brain monoamines. Serotonin (5-HT) is regarded as one of the principal neurotransmitters to be involved in regulation of wide variety of physiological and psychological processes. Among the drugs that affect 5-HT synaptic transmission, the leading role is given to selective serotonin reuptake inhibitors (SSRIs), such as fluoxetine. The aim of the study is to investigate the effects of fluoxetine on seizures in Wistar rats with high susceptibility to audiogenic stress. The study was performed on male Wistar rats. Before the experiments, the animals were tested for susceptibility to audiogenic seizures by exposure to a sound of 90-110 dB for 2 min in the soundproof box. The difference between congenital susceptibility to seizures served as a basis for dividing animals into two groups: Seizure-susceptible (SS) and seizure-tolerant (ST) rats. One hour before the experiment, the experimental animals were orally administered with fluoxetine, while the control rats were treated with distilled water. The effect of fluoxetine on the level of the biogenic amines in different regions of the brain was determined by enzyme-linked immunosorbent assay (ELISA). It has been shown that in 100% of the cases, the control SS rats, exposed to audiogenic stimulus, exhibited wild running around in circles and jumping as some of the signs of seizure responses that evolved into tonic-clonic seizures in 70% of the cases. As regards the experimental SS animals: Only in 60% of the cases (P<0.05), they exhibited wild running and flinch, which did not evolve into the tonic-clonic phase. Decreased manifestation of seizures in the experimental SS rats under acute administration of fluoxetine may be explained by highly distinctive repertoire and spatial distribution of 5-HT receptors in their brain structures in comparison to the ST rats. The study of the monoaminergic mechanisms of seizure generation is of practical importance due to the existence of pharmacological agents, which selectively affect the activity of the monoaminergic systems of the brain, as well as the metabolism of the monoamines synthesized by them.

The role of the GLP-1/GLP-1R signaling pathway in regulating seizure susceptibility in rats

ObjectiveThis study aimed to investigate the role of glucagon-like peptide-1 (GLP-1)/GLP-1 receptor(R) signaling in the regulation of seizure susceptibility and to explore the potential mechanism in rats. MethodsHyperthermia-induced seizures in SD rats were generated using hot bath methods, and seizure severity was measured according to Racine scores and electroencephalogram (EEG). Protein levels of GLP-1 and GLP-1R in the brain tissues of rats were evaluated through ELISA, western blot analysis, and immunohistochemistry to explore the possible roles of each in FS. Neuronal excitability, spontaneous inhibitory postsynaptic currents (sIPSCs) and transient receptor potential cation channel subfamily V member 1(TRPV1) currents were tested using the patch-clamp method in cultured hippocampal neurons. ResultSignificant decreases in the levels of GLP-1 and GLP-1R were observed in the hippocampi of rats compared to those in the control group. Furthermore, treatment with the GLP-1R pharmacological inhibitor exendin9-39 increased hyperthermia- induced seizure severity in rats and promoted neuronal firing activity in cultured neurons. Importantly, exendin9-39 and GLP-1R knockdown decreased the amplitude and frequency of sIPSCs in cultured neurons. In addition, GLP-1R knockdown elevated downstream TRPV1 expression and promoted capsaicin-induced TRPV1 function, which may regulate inhibitory neurotransmission to affect seizure susceptibility. ConclusionThe present study suggests that inhibition of GLP-1R signaling promotes seizure activity, which plays a key role in the pathogenesis of FS.

Pentylenetetrazole-induced seizures in developing rats prenatally exposed to valproic acid.

BackgroundEpidemiological evidence indicates epilepsy is more common in patients with autism spectrum disorders (ASD) (20–25%) than in the general population. The aim of this project was to analyze seizure susceptibility in developing rats prenatally exposed to valproic acid (VPA) as autism model.MethodsPregnant females were injected with VPA during the twelfth embryonic day. Seizures were induced in fourteen-days-old rat pups using two models of convulsions: pentylenetetrazole (PTZ) and lithium-pilocarpine (Li-Pilo).ResultsTwo subgroups with different PTZ-induced seizure susceptibility in rats exposed to VPA were found: a high susceptibility (VPA+) (28/42, seizure severity 5) and a low susceptibility (VPA−) (14/42, seizure severity 2). The VPA+ subgroup exhibited an increased duration of the generalized tonic-clonic seizure (GTCS; 45 ± 2.7 min), a higher number of rats showed several GTCS (14/28) and developed status epilepticus (SE) after PTZ injection (19/27) compared with control animals (36.6 ± 1.9 min; 10/39; 15/39, respectively). No differences in seizure severity, latency or duration of SE induced by Li-Pilo were detected between VPA and control animals.DiscussionPrenatal VPA modifies the susceptibility to PTZ-induced seizures in developing rats, which may be linked to an alteration in the GABAergic transmission. These findings contribute to a better understanding of the comorbidity between autism and epilepsy.

Alcohol Withdrawal Increases Protein Kinase A Activity in the Rat Inferior Colliculus.

Cyclic AMP-dependent protein kinase A (PKA) signaling is a key target for the action of alcohol and may therefore play a role in the pathophysiology of alcohol withdrawal seizures (AWSs). Here, we investigated the role of PKA activity with respect to increased seizure susceptibility in rats that were subjected to alcohol withdrawal. Adult male Sprague Dawley rats received 3 daily doses of ethanol (EtOH) (or vehicle) for 4 consecutive days. Rats were then tested for susceptibility to acoustically evoked AWSs 3, 24, and 48hours after the last alcohol dose. In separate experiments, the inferior colliculus (IC) was collected at these same time points from rats subjected to alcohol withdrawal and control rats following alcohol withdrawal. PKA activity, catalytic Cα (PKACα ) protein, regulatory RIIα (PKARIIα ) protein, and RIIβ (PKARIIβ ) protein were measured in the IC. Lastly, insitu pharmacological studies were performed to evaluate whether inhibiting PKA activity in the IC suppressed AWSs. In the EtOH-treated group, AWSs were observed at the 24-hour time point, but not at the 3-hour or 48-hour time points. In the IC, PKA activity was significantly higher both 3hours (i.e., before AWS susceptibility) and 24hours after the last alcohol dose (when AWS susceptibility peaked) than in control rats. Consistent with these findings, protein levels of the PKACα subunit were significantly increased in the IC both 3 and 24hours after the last alcohol dose. Lastly, insitu inhibition of PKA activity within the IC suppressed AWSs. The increase in PKA activity and PKACα protein expression in the IC preceded the occurrence of AWSs, and inhibiting PKA activity within the IC suppressed acoustically evoked AWSs. Together, these findings suggest that altered PKA activity plays a key role in the pathogenesis of AWSs.

A Missense Mutation of the Gene Encoding Synaptic Vesicle Glycoprotein 2A (SV2A) Confers Seizure Susceptibility by Disrupting Amygdalar Synaptic GABA Release

Synaptic vesicle glycoprotein 2A (SV2A) is specifically expressed in the membranes of synaptic vesicles and modulates action potential-dependent neurotransmitter release. To explore the role of SV2A in the pathogenesis of epileptic disorders, we recently generated a novel rat model (Sv2aL174Q rat) carrying a missense mutation of the Sv2a gene and showed that the Sv2aL174Q rats were hypersensitive to kindling development (Tokudome et al., 2016). Here, we further conducted behavioral and neurochemical studies to clarify the pathophysiological mechanisms underlying the seizure vulnerability in Sv2aL174Q rats. Sv2aL174Q rats were highly susceptible to pentylenetetrazole (PTZ)-induced seizures, yielding a significantly higher seizure scores and seizure incidence than the control animals. Brain mapping analysis of Fos expression, a biological marker of neural excitation, revealed that the seizure threshold level of PTZ region-specifically elevated Fos expression in the amygdala in Sv2aL174Q rats. In vivo microdialysis study showed that the Sv2aL174Q mutation preferentially reduced high K+ (depolarization)-evoked GABA release, but not glutamate release, in the amygdala. In addition, specific control of GABA release by SV2A was supported by its predominant expression in GABAergic neurons, which were co-stained with antibodies against SV2A and glutamate decarboxylase 1. The present results suggest that dysfunction of SV2A by the missense mutation elevates seizure susceptibility in rats by preferentially disrupting synaptic GABA release in the amygdala, illustrating the crucial role of amygdalar SV2A-GABAergic system in epileptogenesis.

Sleep disruption increases seizure susceptibility: Behavioral and EEG evaluation of an experimental model of sleep apnea

Sleep disruption accompanies sleep apnea as one of its major symptoms. Obstructive sleep apnea is particularly common in patients with refractory epilepsy, but causing factors underlying this are far from being resolved. Therefore, translational studies regarding this issue are important. Our aim was to investigate the effects of sleep disruption on seizure susceptibility of rats using experimental model of lindane-induced refractory seizures.Sleep disruption in male Wistar rats with implanted EEG electrodes was achieved by treadmill method (belt speed set on 0.02m/s for working and 0.00m/s for stop mode, respectively). Animals were assigned to experimental conditions lasting 6h: 1) sleep disruption (sleep interrupted, SI; 30s working and 90s stop mode every 2min; 180cycles in total); 2) activity control (AC, 10min working and 30min stop mode, 9cycles in total); 3) treadmill chamber control (TC, only stop mode). Afterwards, the animals were intraperitoneally treated with lindane (L, 4mg/kg, SI+L, AC+L and TC+L groups) or dimethylsulfoxide (DMSO, SIc, ACc and TCc groups). Convulsive behavior was assessed by seizure incidence, latency time to first seizure, and its severity during 30min after drug administration. Number and duration of ictal periods were determined in recorded EEGs.Incidence and severity of lindane-induced seizures were significantly increased, latency time significantly decreased in animals undergoing sleep disruption (SI+L group) compared with the animals from TC+L. Seizure latency was also significantly decreased in SI+L compared to AC+L groups. Number of ictal periods were increased and duration of it presented tendency to increase in SI+L comparing to AC+L. No convulsive signs were observed in TCc, ACc and SIc groups, as well as no ictal periods in EEG.These results indicate sleep disruption facilitates induction of epileptic activity in rodent model of lindane-epilepsy enabling translational research of this phenomenon.

The effect of co-administration of restraint stress and morphine in prenatal period and re-exposure to stress at the end of infancy on corticosterone blood levels and pentylentetrazol-induced epileptic behaviors in rat

Stressful events during gestation have important effects on the later physical and mental health of the offspring. The present study aimed to identify effects of co-administration of stress and morphine in prenatal period and re-exposure to stress at the end of infancy on corticosterone blood levels and pentylentetrazol-induced epileptic behaviors in rat. Materials and Methods: Pregnant rats were divided to six groups of control, stress, saline, morphine, stress-saline and stressmorphine. In the stressed group, rats were stressed and held immobile for three consecutive days started on day 15 of pregnancy. The rats in saline and morphine groups received saline and morphine in the same days. In the morphine/saline-stress groups, rats were exposed to stress and received morphine/saline simultaneously. On postnatal day 22, half of the pups re-exposed to stress, and pentylentetrazol-induced epileptic behaviors of each rat were assessed. Blood samples were collected to determine corticosterone level. Results: Latency of first epileptic behavior decreased significantly in stress-morphine group compared to other groups. Re-exposure to stress significantly led to a decrease in number of clonic seizure. There was no significant difference between the experimental groups in duration of clonic attacks and mortality rate. The level of corticosterone showed a significant increase in stressed pups and decreased in morphine group. Conclusion: these results indicated that co-administration of morphine and restraint stress during late pregnancy had profound impact on neurochemical development and might alter vulnerability to PTZ-induced epileptic behaviors. Prenatal stress is more powerful than postnatal stress on influencing neural development and seizure susceptibility in rats

Advances on genetic rat models of epilepsy.

Considering the suitability of laboratory rats in epilepsy research, we and other groups have been developing genetic models of epilepsy in this species. After epileptic rats or seizure-susceptible rats were sporadically found in outbred stocks, the epileptic traits were usually genetically-fixed by selective breeding. So far, the absence seizure models GAERS and WAG/Rij, audiogenic seizure models GEPR-3 and GEPR-9, generalized tonic-clonic seizure models IER, NER and WER, and Canavan-disease related epileptic models TRM and SER have been established. Dissection of the genetic bases including causative genes in these epileptic rat models would be a significant step toward understanding epileptogenesis. N-ethyl-N-nitrosourea (ENU) mutagenesis provides a systematic approach which allowed us to develop two novel epileptic rat models: heat-induced seizure susceptible (Hiss) rats with an Scn1a missense mutation and autosomal dominant lateral temporal epilepsy (ADLTE) model rats with an Lgi1 missense mutation. In addition, we have established episodic ataxia type 1 (EA1) model rats with a Kcna1 missense mutation derived from the ENU-induced rat mutant stock, and identified a Cacna1a missense mutation in a N-Methyl-N-nitrosourea (MNU)-induced mutant rat strain GRY, resulting in the discovery of episodic ataxia type 2 (EA2) model rats. Thus, epileptic rat models have been established on the two paths: ‘phenotype to gene’ and ‘gene to phenotype’. In the near future, development of novel epileptic rat models will be extensively promoted by the use of sophisticated genome editing technologies.

Deletion of insulin-regulated aminopeptidase in mice decreases susceptibility to pentylenetetrazol-induced generalized seizures

The peptide angiotensin IV (Ang IV) influences seizure susceptibility in rat and mouse models. Indeed, Ang IV has been shown to protect rats from limbic seizures in the focal pilocarpine model. Moreover, both anticonvulsive and antiepileptogenic effects of Ang IV have been reported in the acute pentylenetetrazol (PTZ) and kindling model of generalized seizures in mice. It has been hypothesized that the latter effects on seizures could be established via a modulatory effect on dopamine receptors in the basal ganglia or via an indirect interaction between Ang IV and adenosine A1 receptors. However, a possible role for insulin-regulated aminopeptidase (IRAP), the high affinity binding site for Ang IV, has not been studied yet. To unequivocally unravel the involvement of IRAP in generalized seizure generation, we investigated the susceptibility of male IRAP wild-type (IRAP +/+) and knock-out (IRAP −/−) mice to PTZ-induced seizures. Challenging these mice intravenously with PTZ resulted in significantly increased thresholds for myoclonic twitch and generalized clonic seizures with loss of righting reflexes in IRAP −/− mice compared to their IRAP +/+ littermates. These behavioural data were confirmed by video-electrocorticography monitoring. Our study shows that IRAP −/− mice are less sensitive to the development of PTZ-induced seizures and suggests that IRAP is involved in generalized seizure generation.

The Effect of Spinal Cord Stimulation on Seizure Susceptibility in Rats

Spinal cord stimulation (SCS) activates the thalamus, which may be involved in generation of seizures. SCS may therefore influence seizure susceptibility. We investigated the effect of SCS on seizure susceptibility when performed at low frequency (4 Hz) and a frequency in the typical range of SCS treatment (54 Hz). Rats were divided in three groups: control (N = 8), 4 Hz SCS (N = 6), and 54 Hz SCS (N = 8). Tonic-clonic seizures were induced by 10-min intravenous infusion of pentylenetetrazole (PTZ). SCS was started 5 min prior to PTZ infusion and continued for 5 min after infusion offset. Seizure susceptibility was accessed via the latency, number, and total duration of seizures. Four Hz SCS significantly increased seizure susceptibility. Fifty-four Hz SCS produced a nonsignificant trend toward decreased seizure susceptibility. Low-frequency SCS is proconvulsive in rats. Further research needs to investigate if this also applies to humans.

The effects of chronic losartan pretreatment on restraint stress-induced changes in motor activity, nociception and pentylenetetrazol generalized seizures in rats

Accumulated evidence has shown that renin-angiotensin system has a pivotal role in stress responses. to assess the participation of AT1 receptor in stress-induced modulation of motor activity, nociception and seizure susceptibility in male Wistar rats. AT1 receptor antagonist losartan was administered subcutaneously to rats for 10 days at a dose of 10 mg/kg either alone or as a pretreatment before chronic restraint stress applied for 10 days. Locomotor and exploratory activity (open field test), the nociception (paw-pressure test) and the seizure susceptibility (pentylenetetrazol seizure test) were analysed. Chronic restraint stress decreased motor activity and increased anxiety-like behaviour (grooming) while losartan pretreatment alleviated anxiety-like behaviour. Chronic restraint stress had an antinociceptive effect in paw-pressure test and losartan pretreatment abolished stress-induced antinociception. Both chronic restraint stress and losartan showed anticonvulsant activity in pentylenetetrazol seizure test. However, drug pretreatment attenuated this effect in chronically-stressed rats. Our findings suggest that the AT1 receptor is involved in the mechanism of stress-induced changes in anxiety-like behaviour, nociception and seizure susceptibility in rats.

Effects of early postnatal caffeine exposure on seizure susceptibility of rats are age- and model-dependent

Repeated caffeine treatment during early postnatal period led to a decreased sensitivity to convulsant action of drugs interfering with inhibitory systems. To know if it is a general effect we studied convulsant action of agonists of glutamate receptors N-methyl-d-aspartate (NMDA) and kainic acid (KA). Early (the first day after the last injection) and delayed (at postnatal day (P) 25) consequences of daily administration of caffeine at P7-P11 or P13-P17 days were studied. Two doses (one submaximal and one supramaximal) of either drug were chosen for each age group on the basis of our older data demonstrating decreasing sensitivity during postnatal development. Both early and delayed proconvulsant effects of submaximal doses of either agonist were observed in P7-P11 groups, early effect was markedly expressed; the effects of the supramaximal doses were not affected. The other administration group (P13-P17) also exhibited an increased sensitivity to convulsant action but delayed effects were more pronounced than early consequences especially with supramaximal doses of both agonists. In contrast to a decreased sensitivity to drugs suppressing inhibitory systems, seizures induced by glutamate receptor agonists are potentiated in caffeine-treated immature rats. Timing of caffeine administration and interval between the last exposure and testing play an important role.

Dietary omega‐3 polyunsaturated fatty acid deprivation lowers seizure threshold in rats

Several candidate genes that play a role in seizure etiology have been identified. Yet, the impact of environmental influences such as dietary omega‐3 polyunsaturated fatty acids (n‐3 PUFA) is not known. We therefore tested the impact of chronic dietary n‐3 PUFA deprivation on seizure threshold in the cortex and amygdala. Rats were surgically implanted with electrodes in the cortex or amygdala, and subsequently randomized to the AIN‐93G diet containing n‐3 PUFA derived from soybean oil, or a modified n‐3 PUFA‐deficient version derived from coconut and safflower oil. The rats were maintained on the diets for 33 weeks. Seizure thresholds were measured monthly by electrically stimulating the cortex and amygdala. At the end of 33 weeks, seizure threshold was assessed following a bolus subcutaneous injection of oleic (OA) or docosahexaenoic acids (DHA). Dietary n‐3 PUFA deprivation resulted in a statistically significant decrease in cortical and amygdaloid thresholds by week 16, relative to baseline (P&lt;0.05). The decrease in thresholds was not observed in rats on the control, soybean oil diet. Compared to a bolus injection of OA, acute injection of DHA raised seizure threshold in rats on the control diet but not the n‐3 PUFA deficient diet (P&lt;0.05). These findings demonstrate for the first time that dietary n‐3 PUFA deficiency increases seizure susceptibility in rats.Grant Funding SourceCanadian Institutes of Health research

Hyperthermia-induced seizure-susceptible rats: a novel model of febrile seizures

Evidence that febrile seizures have a strong genetic predisposition has been well documented. In families of probands with multiple febrile convulsions, an autosomal dominant inheritance with reduced penetrance is suspected. Four candidate loci for febrile seizures have been suggested to date; FEB1 on 8q13–q21, FEB2 on 19p, FEB3 on 2q23–q24, and FEB4 on 5q14–15. A missense mutation was identified in the voltage-gated sodium (Na+)-channel β1 subunit gene, SCN1B at chromosome 19p13.1 in generalized epilepsy with the febrile seizures plus type 1 (GEFS+1) family. Several missense mutations of the (Na+)-channel α1 subunit (Nav1.1) gene, SCN1A were also identified in GEFS+2 families at chromosome 2q23–q24.3. The aim of this report is precisely to describe the phenotypes of Japanese patients with novel SCN1A mutations and to reevaluate the entity of GEFS+. Four family members over three generations and one isolated (phenotypically sporadic) case with SCN1A mutations were clinically investigated. The common seizure type in these patients was febrile and afebrile generalized tonic–clonic seizures (FS+). In addition to FS+, partial epilepsy phenotypes were suspected in all affected family members and electroencephalographically confirmed in three patients of two families. GEFS+ is genetically and clinically heterogenous, and associated with generalized epilepsy and partial epilepsy as well. The spectrum of GEFS+ should be expanded to include partial epilepsies and better to be termed autosomal dominant epilepsy with febrile seizures plus (ADEFS+).

Intestinal Inflammation and Seizure: understanding the role of TNF‐alpha in rat model

Objective: Present study was carried out to evaluate the role of TNF α and correlation between intestinal inflammation and PTZ induced seizure susceptibility in rat model.Methods and Materials: Rats were divided into 3 groups (n=6 in each group). Colitis was induced by single intra‐colonic administration of TNBS (20mg / 35% ethanol). Group I received ethanol (vehicle) intra colonic, Group II (TNBS), Group III (thalidomide 150mg/kg b. wt/d orally for 14 days after induction of colitis). After 14 days animals were sacrificed and colonic tissue was used for morphological score, histological score and different biochemical parameters (MPO, MDA, SOD, Catalase, GPx, TNF‐α in serum &amp; brain).Results: Seizure susceptibility showed increase seizure score as well as reduction of onset of the seizure in the colitis group compared to control group. Thalidomide provided protection against TNBS‐induced colonic damage both histologically, morphologically and as evident in different biochemical parameters (MPO, MDA SOD, CAT, GPx, and TNF‐α in serum and brain) (p&lt;0.001).Conclusion: Present study showed the increase seizure susceptibility following peripheral inflammation of colitis indicate correlations of colitis and seizure with role of TNF α. (Supported by PGIMER, Chandigarh, India)

Effects of a Single Dose of Erythropoietin on Subsequent Seizure Susceptibility in Rats Exposed to Acute Hypoxia at P10

To determine if posthypoxia treatment with erythropoietin (EPO) has protective effects against subsequent susceptibility to seizure related neuronal injury in rat pups subjected to acute hypoxia at P10. Four groups of rats were manipulated at P10, as described below, then all received kainic acid (KA) (10 mg/kg i.p.) at P29: Hypoxia-NS-KA group (n = 11): subjected to acute hypoxia (down to 4% O2), and then immediately received saline i.p. Hypoxia-EPO-KA group (n = 10): subjected to acute hypoxia and then immediately received EPO (1,000 U/Kg i.p.). Normoxia-NS-KA group (n = 11): sham manipulated and injected with saline. Normoxia-EPO-KA group (n = 10): sham manipulated then immediately injected with EPO (1000 U/Kg i.p.). After receiving KA at P29, all rats were monitored using videotape techniques, and were sacrificed at P31. TUNEL and Hoechst stains to assess for apoptosis, and regular histology for hippocampal cell counts were performed. Administration of the single dose of erythropoietin directly after an acute hypoxic event at P10 resulted at P29 in increased latency to forelimb clonus seizures, reduced duration of these seizures, protection against hippocampal cell loss, and decreased hippocampal apoptosis in the Hypoxia-EPO-KA group as compared to the Hypoxia-NS-KA group. These data support the presence of favorable protective effects of erythropoietin against the long-term consequences of acute hypoxia in the developing brain and raise the possibility of its investigation as a potential neuroprotective agent after human neonatal hypoxic encephalopathy.

Aversive effects elicited by electrical stimulation of the inferior colliculus in normal and audiogenic seizure susceptible rats

Trains of electrical stimulations were applied to the dorsal or ventral part of the inferior colliculus (IC) of audiogenic seizure susceptible rats from the AGSR strain. Threshold and duration of wild running (WR), were evaluated in the first experiment. All stimulation sites elicited WR, even in normal control rats. Stimulation of the IC of AGSR rats required a lower quantity of current, i.e., such brain sites were more sensitive to the current, than normal controls. The duration of post-stimulus WR was shorter in AGSR rats. Lower quantities of current applied to the ventral IC were needed to elicit WR than to the dorsal IC in AGSR rats. In a second experiment, using the same stimulations sites in the same rats, the emotional effect of the stimulation was tested through an instrumental learning procedure (switch-off paradigm) in which the rat was trained to press a bar to put an end to the stimulation. Both dorsal and ventral IC stimulation sites sustained switch-off behavior in AGSR rats, but only ventral IC stimulation sites sustained switch-off learning in control rats.

Pilocarpine-Induced Seizure Susceptibility in Rats Following Prenatal Methylazoxymethanol Treatment

Several rodent models of cortical malformation are available for the study of cellular mechanisms associated with early-onset epilepsy, but few are associated with spontaneous seizures. We examined the effect of pilocarpine on the spontaneous seizure development and excitability of the CA1 pyramidal cells of rats after prenatal treatment with methylazoxymethanol (MAM). Pilocarpine induced status epilepticus (SE) onset latency was greater for normal rats than for MAM-treated rats. After several days of normal behavior following pilocarpine treatment, the duration of spontaneous seizures were greater in MAM-pilocarpine rats than in normal-pilocarpine rats. Compared with the normal rats, electrical stimulation of afferent fibers resulted in more robust population responses in the CA1 region in all groups. At interstimulus intervals of 30 and 70 ms, the MAM-pilocarpine rats displayed a decrease in paired pulse inhibition versus the conventional MAM rats. A loss of somatostatin- and parvalbumin-immunoreactive neurons was apparent in the normal-pilocarpine rats, MAM-pilocarpine rats, and conventional MAM rats. These results indicate that pilocarpine induces spontaneous seizures and hyperexcitability in MAM-pilocarpine rats.