Trend of subsequent epilepsy in children with recurrent febrile seizures: A retrospective matched cohort study.

PURPOSE: Trends of epilepsy in children were correlated with febrile seizure (FS) in a previous retrospective study. In the present study, the authors obtained relevant data from a nationwide cohort database to investigate trends in subsequent epilepsy in children with a history of recurrent FS. METHODS: A total of 10,210 children with FS comprised the cohort. The diagnosis date was used as the index date. A comparison cohort was randomly matched with each case based on age, sex, urbanization level, parents' occupation, and index date. Cox proportional hazard regression was performed to estimate the hazard ratio and confidence interval of FS-associated epilepsy. RESULTS: This retrospective cohort study included 7729 children with FS and a comparison cohort of 30,916 children. The incidence of epilepsy was 11.4-fold higher in the FS cohort than in the comparison cohort (5.67 vs. 0.49 per 1000 person-years, respectively). Compared with the comparison cohort, the epilepsy incidence rate ratio increased in children with admissions for FS, from 8.62 at 1 admission to 26.2 at ≥2 admissions (95% CI 6.80-10.9, and 19.78-34.8, respectively; p for trend < 0.0001). CONCLUSION: FS may increase the risk for subsequent epilepsy in children. Recurrent FS increased the cumulative incidence of epilepsy.

Intergenerational Transmission of Enhanced Seizure Susceptibility after Febrile Seizures.

Environmental exposure early in development plays a role in susceptibility to disease in later life. Here, we demonstrate that prolonged febrile seizures induced by exposure of rat pups to a hyperthermic environment enhance seizure susceptibility not only in these hyperthermia-treated rats but also in their future offspring, even if the offspring never experience febrile seizures. This transgenerational transmission was intensity-dependent and was mainly from mothers to their offspring. The transmission was associated with DNA methylation. Thus, our study supports a "Lamarckian"-like mechanism of pathogenesis and the crucial role of epigenetic factors in neurological conditions.

Searsia chirindensis reverses the potentiating effect of prenatal stress on the development of febrile seizures and decreased plasma interleukin-1ß levels.

It is estimated that more than 80% of patients with epilepsy live in developing countries with 50-60% of them being children. This high prevalence is perpetuated by low socio-economic challenges, poor health care facilities and lack of drug affordability. Searsia chirindensis formerly known as rhus chirindensis and commonly known as 'Red Current' is a popular traditional medicinal plant, which has been used to treat a number of illnesses such as heart complaints and neurological disorders. The aim of this study is to investigate the effects of S. chirindensis on the development of febrile seizure in a prenatally stressed rat. Febrile seizures were induced by administering lipopolysaccharide to 14-day-old rat pups followed by kainic acid. A subset of the rats was treated with Searsia after induction of febrile seizures. Interleukin-1ß (IL-1ß) levels were measured in plasma. Lipid peroxidation was determined in liver tissue. Our data shows that treatment with Searsia reduced interleukin-1ß levels in plasma of the febrile seizure rats and prevented lipid oxidation in the liver. Prenatal stress is dampened by the beneficial effects of Searsia on seizure development in rat pups. These results highlight the potentiating effects of Searsia in the reversal of febrile seizures and prenatal stress effects.

An enhanced home cage modulates hypothalamic CRH-ir labeling in juvenile rats, with and without sub-threshold febrile convulsions.

Pre and postnatal environments can have a profound impact on offspring development. This is especially true when considering the origin of neurological diseases, including epilepsy, a relatively common and chronic neurological condition, affecting 1-2% of the population. Previously, we have used maternal stress and an enhanced home cage (EHC) in an effort to identify potential factors in the early environment that may increase the risk for experiencing seizures. First, pregnant Long-Evans rats were exposed to a predator stress (PS). Then, at birth, litters were divided into standard cage (SC) and EHC groups until postnatal Day 14 (PD14) when a model of febrile convulsions was used to determine convulsion susceptibility of the various groups. Twenty-four hours later, pup brains were processed for immunohistochemical detection of corticotrophic releasing hormone (CRH) in the paraventricular nucleus of the hypothalamus. Analysis of CRH immunoreactive (-ir) patterns revealed a buffering of CRH-ir in EHC reared offspring. Further, experiencing convulsions led to decreased CRH-ir. Our results support the concept that postnatal environmental influences affect neonatal programming and neurodevelopment of processes that could underlie seizure susceptibility, and that these effects can be modulated by EHC conditions.

GABAergic excitation after febrile seizures induces ectopic granule cells and adult epilepsy.

Temporal lobe epilepsy (TLE) is accompanied by an abnormal location of granule cells in the dentate gyrus. Using a rat model of complex febrile seizures, which are thought to be a precipitating insult of TLE later in life, we report that aberrant migration of neonatal-generated granule cells results in granule cell ectopia that persists into adulthood. Febrile seizures induced an upregulation of GABA(A) receptors (GABA(A)-Rs) in neonatally generated granule cells, and hyperactivation of excitatory GABA(A)-Rs caused a reversal in the direction of granule cell migration. This abnormal migration was prevented by RNAi-mediated knockdown of the Na(+)K(+)2Cl(-) co-transporter (NKCC1), which regulates the excitatory action of GABA. NKCC1 inhibition with bumetanide after febrile seizures rescued the granule cell ectopia, susceptibility to limbic seizures and development of epilepsy. Thus, this work identifies a previously unknown pathogenic role of excitatory GABA(A)-R signaling and highlights NKCC1 as a potential therapeutic target for preventing granule cell ectopia and the development of epilepsy after febrile seizures.

Características clínicas, electroencefalográficas y genómicas de los pacientes con epilepsia con crisis febriles plus / Clinical, electroencephalographic and genomic characteristics of patients with epilepsy with febrile seizueres plus

Introducción. Las mutaciones en los canales de sodio dependientes del voltaje o en los receptores del ácido gamma-aminobutírico son las más frecuentes en el espectro de epilepsias con crisis febriles plus. Objetivo. Describir las características clínicas, electroencefalográficas y genómicas de los pacientes con epilepsia con crisis febriles plus y compararlo con la bibliografía. Pacientes y métodos. Analizamos 26 pacientes con este diagnóstico y estudio genético dirigido, recogiendo variables correspondientes a datos epidemiológicos, características de la epilepsia, evolución, pruebas complementarias, tratamientos antiepilépticos y estudio genético. Resultados. Nueve pacientes presentaron epilepsia generalizada con crisis febriles plus; seis, síndrome de Dravet; seis, síndrome de Dravet borderline; dos, síndrome de Doose; y tres, epilepsia parcial criptogénica. Se evidenció alteración genética en el 62% de los casos. La edad media de inicio de la epilepsia fue de 13,5 meses, siendo menor la edad, con diferencia estadísticamente significativa, en los pacientes con genética positiva. El 58% de los casos sufrió un estado epiléptico al inicio o en la evolución de la epilepsia. El 85% de los casos tomaba ácido valproico. El 58% manifestó deterioro cognitivo. Se realizaron pruebas complementarias en todos los pacientes. Conclusiones. Las epilepsias con crisis febriles plus componen un grupo genéticamente heterogéneo. Las mutaciones de tipo missense son las más frecuentes en nuestro estudio. Aunque las correlaciones fenotipo-genotipo son difíciles de establecer, los pacientes con deleciones mostraron un síndrome de Dravet típico o borderline, mientras que las mutaciones en el receptor del ácido gamma-aminobutírico tienen epilepsia menos grave (AU)

voltagedependent sodium channels or in the gamma-aminobutyric acid receptors. Aim. To describe the clinical, electroencephalographic and genomic characteristics of patients with epilepsy with febrile seizures plus and compare them with those found in the literature. Patients and methods. We analysed 26 patients who had been diagnosed with this condition and had had a targeted genetic study with the aim of collecting variables related to epidemiological data, characteristics of the epilepsy, development, complementary tests, antiepileptic treatments and genetic study. Results. Nine patients presented generalised epilepsy with febrile seizures plus; six had Dravet’s syndrome; six had borderline Dravet’s syndrome; two had Doose’s syndrome; and three of them had cryptogenic partial epilepsy. Genetic disorders were observed in 62% of the cases. The mean age of onset of epilepsy was 13.5 months and the age was lower (with statistically significant differences) in patients with positive genetic testing. Epileptic status was suffered by 58% of cases either at onset or in the development of the epilepsy. A total of 85% of cases were taking valproic acid and 58% displayed cognitive impairment. Complementary tests were performed in all the patients. Conclusions. Epilepsies with febrile seizures plus make up a genetically heterogeneous group. Missense mutations were the most common in our study. Although it is difficult to establish phenotype-genotype correlations, patients with deletions showed typical or borderline Dravet’s syndrome, whereas mutations in the gamma-aminobutyric acid receptor had less severe epilepsy (AU)

Long-lasting modulation of synaptic plasticity in rat hippocampus after early-life complex febrile seizures.

A small fraction of children with febrile seizures appears to develop cognitive impairments. Recent studies in a rat model of hyperthermia-induced febrile seizures indicate that prolonged febrile seizures early in life have long-lasting effects on the hippocampus and induce cognitive deficits. However, data on network plasticity and the nature of cognitive deficits are conflicting. We examined three specific measures of hippocampal plasticity in adult rats with a prior history of experimental febrile seizures: (i) activity-dependent synaptic plasticity (long-term potentiation and depression) by electrophysiological recordings of Schaffer collateral/commissural-evoked field excitatory synaptic potentials in CA1 of acute hippocampal slices; (ii) Morris water maze spatial learning and memory; and (iii) hippocampal mossy fiber plasticity by Timm histochemistry and quantification of terminal sprouting in CA3 and the dentate gyrus. We found enhanced hippocampal CA1 long-term potentiation and reduced long-term depression but normal spatial learning and memory in adult rats that were subjected to experimental febrile seizures on postnatal day 10. Furthermore, rats with experimental febrile seizures showed modest but significant sprouting of mossy fiber collaterals into the inner molecular layer of the dentate gyrus in adulthood. We conclude that enhanced CA1 long-term potentiation and mild mossy fiber sprouting occur after experimental febrile seizures, without affecting spatial learning and memory in the Morris water maze. These long-term functional and structural alterations in hippocampal plasticity are likely to play a role in the enhanced seizure susceptibility in this model of prolonged human febrile seizures but do not correlate with overt cognitive deficits.

N-methyl-D-aspartate, hyperpolarization-activated cation current (Ih) and gamma-aminobutyric acid conductances govern the risk of epileptogenesis following febrile seizures in rat hippocampus.

Febrile seizures are the most common types of seizure in children, and are generally considered to be benign. However, febrile seizures in children with dysgenesis have been associated with the development of temporal lobe epilepsy. We have previously shown in a rat model of dysgenesis (cortical freeze lesion) and hyperthermia-induced seizures that 86% of these animals developed recurrent seizures in adulthood. The cellular changes underlying the increased risk of epileptogenesis in this model are not known. Using whole cell patch-clamp recordings from CA1 hippocampal pyramidal cells, we found a more pronounced increase in excitability in rats with both hyperthermic seizures and dysgenesis than in rats with hyperthermic seizures alone or dysgenesis alone. The change was found to be secondary to an increase in N-methyl-D-aspartate (NMDA) receptor-mediated excitatory postsynaptic currents (EPSCs). Inversely, hyperpolarization-activated cation current was more pronounced in naïve rats with hyperthermic seizures than in rats with dysgenesis and hyperthermic seizures or with dysgenesis alone. The increase in GABAA-mediated inhibition observed was comparable in rats with or without dysgenesis after hyperthermic seizures, whereas no changes were observed in rats with dysgenesis alone. Our work indicates that in this two-hit model, changes in NMDA receptor-mediated EPSCs may facilitate epileptogenesis following febrile seizures. Changes in the hyperpolarization-activated cation currents may represent a protective reaction and act by damping the NMDA receptor-mediated hyperexcitability, rather than converting inhibition into excitation. These findings provide a new hypothesis of cellular changes following hyperthermic seizures in predisposed individuals, and may help in the design of therapeutic strategies to prevent epileptogenesis following prolonged febrile seizures.

New vistas and views in the concept of generalized epilepsies.

The aim of this work is to show explicitly why the "idiopathic generalized epilepsy" concept becomes outfashioned and untenable. As the concept of "generalized epilepsies" is from long ago closely related to the thalamo-cortical system, we briefly summarize the functional anatomy, the double working mode of the thalamo-cortical system in different vigilance states and it's role in development of the spike-wave pattern. The next part shows weaknesses of this concept from the EEG, seizure semiology, and neuroimaging point of view. Further experimental and clinical arguments are accumulated from the reflex epileptic features in IGE, indicating local/regional cortical hyperexcitability. A separate part is devoted to genetic aspects of the question. Lastly implications to epilepsy classification are shown and an outlook toward a unified epilepsy concept is provided. The epileptic disorder of the thalamo-cortical system is responsible for the development of "generalized", synchronous spike-wave paroxysms as the common neurophysiological background in "primary" - idiopathic and in "secondary" generalized epilepsies. This disorder is specifically related to the burstfiring working mode of the thalamo-cortical system during NREM sleep (is an epileptic exageration of it). The "generalized" epilepsy category should be abandoned, being misleading. Epilepsies are proposed to be classified according to their network properties and relations to different physiological systems of the brain. The different phenotypes, named earlier idiopathic (primary) generalized, or symptomatic (secondary) generalized (with encephalopathic features), should be delineated depending on the following factors: 1. speed and extent of syncronization within the thalamo-cortical system, 2. the way how the thalamo-cortical system is involved, 3. which kind of cortical triggers play role, 4. the degree and level of the disorder (restricted to the molecular level or extended to the level of structural alterations - in the cortex or more diffusely, 5. genetic targets and features.

The role of interleukin-1beta in febrile seizures.

Febrile seizures (FS) occur in children as a result of fever. Despite their prevalence, the pathophysiology of FS has remained unclear. Recent evidence from clinical and experimental studies has highlighted a potential role of immune generated products in the genesis of FS. Of particular interest are the pro-inflammatory cytokine, interleukin-1beta (IL-1beta) and its naturally occurring antagonist, interleukin 1 receptor antagonist (IL-1ra). Using a novel animal model of FS, involving the generation of physiological fever, we investigated the role of the IL-1beta/IL-1ra system in the genesis of FS. We found that animals with FS had increased hippocampal and hypothalamic IL-1beta compared to equally treated animals without FS, which was first evident at onset of FS in the hippocampus. There were no differences in IL-1ra levels. ICV IL-1beta increased the number of animals with FS while IL-1ra had an opposite anti-convulsant effect. The data from these studies, in combination with recent results from other laboratories, have established a putative role for the IL-1beta/IL-1ra system in the genesis of FS.

Low frequency electrical stimulation through subdural electrodes in a case of refractory status epilepticus.

OBJECTIVE: We delivered low frequency stimulation through subdural electrodes to suppress seizures in a case of refractory status epilepticus (RSE). METHODS: A 26-year-old female developed RSE after several days of febrile illness. Seizure control required continuous infusion of two anesthetics plus high doses of 2-4 enteral antiepileptic drugs. After 3 months of RSE, subdural strips were placed to determine surgical candidacy. Five independent ictal onset zones were identified. Because she was a poor candidate for epilepsy surgery and had a poor prognosis, the implanted subdural electrodes were used to administer 0.5 Hz stimulations to the ictal onset zones in 30 min trains daily for 7 consecutive days in an attempt to suppress seizures. RESULTS: After 1 day of stimulation, one anesthetic agent was successfully discontinued. Seizures only returned by the 4th day when the second anesthetic had been reduced by 60%. Upon returning, seizures arose from only one of the 5 original ictal onset zones. Unfortunately, RSE persisted, and she eventually died. CONCLUSIONS: In this case of RSE, low frequency stimulation through subdural electrodes transiently suppressed seizures from all but one ictal onset zone and allowed significant reduction in seizure medication. SIGNIFICANCE: Low frequency cortical stimulation may be useful in suppressing seizures.

[Alteration of hydrogen sulfide/cystathionine-beta-synthase system in rats with recurrent febrile seizures].

OBJECTIVE: To study the alteration of hydrogen sulfide (H(2)S)/ cystathionine-beta-synthase (CBS) system during recurrent febrile seizures (FS) in the hippocampus of developing rats. METHODS: The rats were randomly divided into control group (n=8) and hyperthermia-treated group (n=22). Which was subdivided into FS group (n=8) and H group(no seizure occurred, n=9) according to whether seizures occurred. The plasma level of H(2)S was detected by the spectrophotometer. The expression levels of CBS gene and protein were examined by in situ hybridization and immunohistochemistry respectively. RESULTS: The plasma levels of H(2)S were increased significantly in FS group compared with those of control group or H group. The expression levels of CBS gene and protein were enhanced in FS group compared with those of control group or H group. CONCLUSION: The expression levels of H(2)S/ CBS system were up-regulated during recurrent FS.

Causal links between brain cytokines and experimental febrile convulsions in the rat.

PURPOSE: Despite the prevalence of febrile convulsions (FCs), their pathophysiology has remained elusive. We tested the hypothesis that components of the immune response, particularly the proinflammatory cytokine interleukin-1beta (IL-1beta) and its naturally occurring antagonist interleukin-1 receptor antagonist (IL-1ra) may play a role in the genesis of FC. METHODS: Postnatal day 14 rats were treated with lipopolysaccharide (LPS; 200 microg/kg, i.p.) followed by a subconvulsant dose of kainic acid (1.75 mg/kg, i.p.). Brains were harvested at and 2 h after onset of FCs to measure brain levels of IL-1beta and IL-1ra. Separate groups of animals were given intracerebroventricular (ICV) injections of IL-1beta, or IL-1ra in an attempt to establish a causal relation between the IL-1beta/IL-1ra system and FCs. RESULTS: Animals with FCs showed increased IL-1beta in the hypothalamus and hippocampus but not in the cortex compared with noFC animals that also received LPS and kainic acid. This increase was first detected in the hippocampus at onset of FCs. No detectable difference in IL-1ra was found in brain regions examined in either group. When animals were treated with IL-1beta ICV, a dose-dependant increase was noted in the proportion of animals that experienced FCs, whereas increasing doses of IL-1ra, given to separate groups of animals, were anticonvulsant. CONCLUSIONS: Our results suggest that excessive amounts of IL-1beta may influence the genesis of FCs. This may occur by overproduction of IL-1beta, or by alteration in the IL-1beta/IL-1ra ratio in the brain after an immune challenge.

Freeze lesion-induced focal cortical dysplasia predisposes to atypical hyperthermic seizures in the immature rat.

PURPOSE: To determine the effects of focal cortical dysplasia on the behavioral and electrographic features of hyperthermia-induced seizures (HSs) in rats. METHODS: A right sensorimotor cortex freeze lesion was induced in postnatal day 1 (P1) rat pups, and HSs were provoked at P10 under continuous monitoring of core temperature; EEGs were recorded from the right amygdala during and after hyperthermia. Controls included both sham-operated at P1 and naïve rats. RESULTS: HSs began with jaw myoclonus, followed by hindlimb clonus and generalized convulsions (GCs), and terminated by a period of posthyperthermia depression. The threshold temperature and latency of jaw myoclonus were similar across the groups. However, both the threshold temperature and latency of GCs were significantly lower in lesioned pups than in controls (40.5 +/- 0.5 degrees C, n = 24, vs. 42.0 +/- 0.2 degrees C, n = 21; p < 0.001; 6.7 +/- 0.6 min, n = 20, vs. 8.4 +/- 0.6 min, n = 22; p < 0.05). In lesioned pups, the threshold and latencies for jaw myoclonus and hindlimb clonus were similar, whereas in controls, the progression from one to the other was marked by significant differences in both parameters. Posthyperthermia depression was longer in lesioned (13.3 +/- 1.2 min, n = 21) than in control (8.0 +/- 0.8 min, n = 20; p < 0.0001) pups. Ictal EEG activity was recorded during both behavioral seizures and posthyperthermia depression. CONCLUSIONS: An HS in rats with a localized freeze lesion results in lower threshold GC and prolonged ictal manifestations, thus supporting a pathophysiologic link between focal cortical dysplasia and atypical febrile seizures, conditions that have a high prevalence in children with mesial temporal lobe epilepsy.

Long-term plasticity of endocannabinoid signaling induced by developmental febrile seizures.

Febrile (fever-induced) seizures are the most common form of childhood seizures, affecting 3%-5% of infants and young children. Here we show that the activity-dependent, retrograde inhibition of GABA release by endogenous cannabinoids is persistently enhanced in the rat hippocampus following a single episode of experimental prolonged febrile seizures during early postnatal development. The potentiation of endocannabinoid signaling results from an increase in the number of presynaptic cannabinoid type 1 receptors associated with cholecystokinin-containing perisomatic inhibitory inputs, without an effect on the endocannabinoid-mediated inhibition of glutamate release. These results demonstrate a selective, long-term increase in the gain of endocannabinoid-mediated retrograde signaling at GABAergic synapses in a model of a human neurological disease.

The Metropolitan Atlanta Congenital Defects Program: 35 years of birth defects surveillance at the Centers for Disease Control and Prevention.

BACKGROUND: The Metropolitan Atlanta Congenital Defects Program (MACDP) is a population-based birth defects surveillance program administered by the Centers for Disease Control and Prevention (CDC) that has been collecting, analyzing, and interpreting birth defects surveillance data since 1967. This paper presents an overview of MACDP current methods and accomplishments over the past 35 years. METHODS: MACDP actively monitors major birth defects among infants born to residents of five counties of metropolitan Atlanta, an area with approximately 50,000 annual births. Cases are ascertained from multiple sources, coded using a modified British Pediatric Association six-digit code, and reviewed and classified by clinical geneticists. RESULTS: MACDP has monitored trends in birth defects rates and has served as a case registry for descriptive, risk factor, and prognostic studies of birth defects, including studies of Agent Orange exposure among Vietnam War veterans, maternal use of multivitamins, diabetes, febrile illnesses, and survival of children with neural tube defects. MACDP has served as a data source for one of the centers participating in the National Birth Defects Prevention Study, and for developing and evaluating neural tube defects prevention strategies related to the periconceptional use of folic acid supplements. CONCLUSIONS: Since its inception, MACDP has served as a resource for the development of uniform methods and approaches to birth defect surveillance across the United States and in many other countries, monitoring birth defects rates, and as a case registry for various descriptive, etiologic, and survival studies of birth defects. MACDP has also served as a training ground for a large number of professionals active in birth defects epidemiology.

Developmental febrile seizures modulate hippocampal gene expression of hyperpolarization-activated channels in an isoform- and cell-specific manner.

Febrile seizures, in addition to being the most common seizure type of the developing human, may contribute to the generation of subsequent limbic epilepsy. Our previous work has demonstrated that prolonged experimental febrile seizures in the immature rat model increased hippocampal excitability long term, enhancing susceptibility to future seizures. The mechanisms for these profound proepileptogenic changes did not require cell death and were associated with long-term slowed kinetics of the hyperpolarization-activated depolarizing current (I(H)). Here we show that these seizures modulate the expression of genes encoding this current, the hyperpolarization-activated, cyclic nucleotide-gated channels (HCNs): In CA1 neurons expressing multiple HCN isoforms, the seizures induced a coordinated reduction of HCN1 mRNA and enhancement of HCN2 expression, thus altering the neuronal HCN phenotype. The seizure-induced augmentation of HCN2 expression involved CA3 in addition to CA1, whereas for HCN4, mRNA expression was not changed by the seizures in either hippocampal region. This isoform- and region-specific transcriptional regulation of the HCNs required neuronal activity rather than hyperthermia alone, correlated with seizure duration, and favored the formation of slow-kinetics HCN2-encoded channels. In summary, these data demonstrate a novel, activity-dependent transcriptional regulation of HCN molecules by developmental seizures. These changes result in long-lasting alteration of the HCN phenotype of specific hippocampal neuronal populations, with profound consequences on the excitability of the hippocampal network.

The induction of BDNF and c-fos mRNA in the hippocampal formation after febrile seizures.

In this study we investigated the expression of brain-derived neurotrophic factor (BDNF) and c-fos mRNA in the hippocampal formation after febrile seizures (FSs) with in situ hybridization histochemistry using riboprobes. The induction of BDNF mRNA was firstly observed in the dentate gyrus at 30 min after FSs. The expression in the dentate gyrus peaked at 3 h and returned to basal level at 24 h. It was also observed in the CA3 of hippocampus from 2 to 3 h. The induction of c-fos mRNA was observed in the dentate gyrus at 30 min and 1 h. These observations suggest that BDNF and c-fos are the genes whose expression can be altered by FSs and might be related to pathologic alterations after FSs.

Do recurrent febrile convulsions decrease the threshold for pilocarpine-induced seizures? Effects of nitric oxide.

The aim of the study was to determine whether (1) number of febrile convulsions is a predictor of development of temporal lobe epilepsy, (2) the susceptibility of rats to pilocarpine-induced seizures is increased due to febrile convulsions and (3) nitric oxide is a mediator in the pathogenesis of febrile convulsions. Rat pups were exposed to single or multiple hyperthermic seizures. Subconvulsant doses of pilocarpine (100 mg/kg and 150 mg/kg) were injected intraperitoneally to these rats at 60--70 days of age. Also L-arginine was applied to some rats before a single hyperthermic seizure. We found that risk of future epilepsy increases parallel to the number of febrile convulsions and nitric oxide does not have a pathogenetic role at given doses.

Febrile seizures in the developing brain result in persistent modification of neuronal excitability in limbic circuits.

Febrile (fever-induced) seizures affect 3-5% of infants and young children. Despite the high incidence of febrile seizures, their contribution to the development of epilepsy later in life has remained controversial. Combining a new rat model of complex febrile seizures and patch clamp techniques, we determined that hyperthermia-induced seizures in the immature rat cause a selective presynaptic increase in inhibitory synaptic transmission in the hippocampus that lasts into adulthood. The long-lasting nature of these potent alterations in synaptic communication after febrile seizures does not support the prevalent view of the 'benign' nature of early-life febrile convulsions.