A kindling-like effect induced by repeated exposure to heated water in rats

Intracortical functional connectivity dynamics induced by reflex seizures

Functional connectivity analysis is gaining more interest due to its promising clinical applications. To study network mechanisms underlying seizure termination and postictal depression, we explore dynamics of interhemispheric functional connectivity near the offset of focal and bilateral seizures in the experimental model of reflex audiogenic epilepsy. In the model, seizures and spreading depression are induced by sound stimulation of genetically predisposed rodents. We characterize temporal evolution of seizure-associated coupling dynamics in the frontoparietal cortex during late ictal, immediate postictal and interictal resting states, using two measures applied to local field potentials recorded in awake epileptic rats. Signals were analyzed with mean phase coherence index in delta (1-4 Hz), theta (4-10 Hz) beta (10-25 Hz) and gamma (25-50 Hz) frequency bands and mutual information function. The study shows that reflex seizures elicit highly dynamic changes in interhemispheric functional coupling with seizure-, region- and frequency-specific patterns of increased and decreased connectivity during late ictal and immediate postictal periods. Also, secondary generalization of recurrent seizures (kindling) is associated with pronounced alterations in resting-state functional connectivity - an early wideband decrease and a subsequent beta-gamma increase. The findings show that intracortical functional connectivity is dynamically modified in response to seizures on short and long timescales, suggesting the existence of activity-dependent plastic network alterations that may promote or prevent seizure propagation within the cortex and underlie postictal behavioral impairments.

Long-term clinical course and prognosis of hot water epilepsy: 15-Year follow-up

OBJECTIVE

Hot water epilepsy (HWE) is a type of reflex epilepsy triggered by bathing with hot water. Hot water epilepsy is generally considered as a self-limiting benign disease although its long-term course and prognosis remains unknown. In this study, we aimed to determine the long-term clinical course and prognosis of hot water epilepsy and possible factors affecting them.

METHODS

The diagnosis of HWE was made based on the clinical history obtained from patients and their first degree relatives witnessing to the seizures and video recordings of seizures if available; then, the type of seizure was identified. Good prognosis was defined as patients whose seizures were controlled with or without preventive measures and who did not require antiepileptic treatment. The poor prognosis was defined as patients whose seizures continued despite preventive measures and required antiepileptic treatment.

RESULTS

The study included 50 (31 male and 19 female) patients with a mean follow-up of 17.63 ± 10.46 (median, 15.0) years. The age at onset of seizure was 14.52 ± 12.71 (median: 10.0) years. There were 38 (76%) patients in the good prognosis group. 18 (36%) of them achieved complete remission, who did not require preventive measures. In the remaining 20 (40%) patients, seizures could be controlled with only preventive measures. Seizures could be controlled with antiepileptic treatment in only 1 (2%) of 12 (24%) patients in the poor prognosis group. A significant relationship was found between the frequency of hot water seizures (HWSs) and poor prognosis (p = 0.019), as well as the presence of spontaneous seizures outside of bathing and poor prognosis (p = 0.000).

SIGNIFICANCE

Hot water epilepsy, as previously known, is not a self-limiting benign disease. Approximately ¾ of the cases have a good prognosis, but the rest are in the case of chronic epilepsy. The low response rate to antiepileptics' treatment suggests that the pathogenesis of the HWE may differ from other epilepsies.

Anti-convulsant effects of cultures bear bile powder in febrile seizure via regulation of neurotransmission and inhibition of neuroinflammation

ETHNOPHARMACOLOGICAL RELEVANCE

Natural bear bile powder (NBBP) has been used to treat seizures for thousands of years, but its application is greatly restricted due to ethical reasons. Cultured bear bile powder (CBBP), which is produced by biotransformation, may be an appropriate substitute for NBBP. However, the anti-convulsant effects of CBBP and its mechanisms remain unclear.

AIM OF THE STUDY

This study aimed to investigate the anti-convulsant effects and possible mechanisms of CBBP in a febrile seizure (FS) rat model.

MATERIALS AND METHODS

FS was induced by placing the rats in a warm water bath (45.5 °C). The incidence rate and latency of FS, and hematoxylin-eosin staining (HE) were conducted for neurological damage. The levels of 4 bile acids and 8 main neurotransmitters in vivo were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The expression of bile acid related transports, neurotransmitter receptors, inflammatory factors, neurotrophic factors and glial fibrillary acidic protein (GFAP) in hippocampal tissues were detected by real-time PCR, western blotting, and immunohistochemistry.

RESULTS

Pre-treatments with CBBP and similarly, NBBP, significantly reduced the incidence rate and prolonged the latency of FS. Additionally, CBBP alleviated the histological injury induced by FS in the rat hippocampus tissue. LC-MS/MS analyses revealed that CBBP markedly increased the levels of tauroursodeoxycholic acid (TUDCA), taurochenodeoxycholic acid (TCDCA), ursodeoxycholic acid (UDCA), and chenodeoxycholic acid (CDCA) in FS rats. Furthermore, the content of gamma-aminobutyric acid (GABA) was up-regulated in rats pre-treated with CBBP whereas GFAP was down-regulated. CBBP also significantly suppressed the expression of interleukin -1β (IL-1β), tumor necrosis factor α (TNF-α), nuclear factor kappa B (NF-κB), and brain-derived neurotrophic factor (BDNF) and its TrkB receptors, and improved the expression of GABA type A receptors (GABA_AR) and farnesoid X receptors (FXR).

CONCLUSIONS

The present study demonstrated that CBBP had anti-convulsant effects in a FS rat model. CBBP may protect rats against FS, probably by up-regulating FXR, which was activated by increasing brain bile acids, up-regulating GABAergic transmission by inhibiting BDNF-TrkB signaling, and suppressing neuroinflammation by inhibiting the NF-κB pathway.

Cortical-Subcortical morphometric signature of hot water epilepsy patients

BACKGROUND

Cortical and subcortical grey matter (GM) morphometric changes have been demonstrated Temporal Lobe Epilepsy (TLE) or Idiopathic Generalized Epilepsies (IGE). Hot Water Epilepsy (HWE) has not hitherto been studied in these perspectives.

PURPOSE

To investigate the cortical and subcortical grey matter in subjects with HWE in terms of thickness, volume, and surface area using Surface-Based Morphometry (SBM). To assess relationships of SBM-derived metrics with clinical variables.

MATERIALS AND METHODS

Ninety-nine people with HWE and 50 age-matched healthy controls underwent high resolution volumetric MRI brain. These were processed with FreeSurfer to obtain SBM parameters i:e cortical thickness, cortical volume, and Cortical surface area. Volumes of seven subcortical GM structures (hippocampus, globus pallidus, nucleus ambiguous(NA), caudate nucleus, putamen, thalamus, and amygdala) were computed. Intergroup morphometric differences and their correlation with epilepsy-specific clinical variables were calculated.

RESULTS

SBM revealed a global reduction in bihemispheric cortical thickness and left hemispheric cortical volume. Besides, a regional difference in the morphometric measures was noted in temporo-limbic, parietal, pre-cuneus, and the cingulate region. Reduced volume of thalami and left caudate alongside an increased volume of the bilateral amygdala, bilateral nucleus ambiguous (NA), right caudate, and putamen was the other cardinal observation.

CONCLUSION

HWE subjects show alterations in the morphometry of the cortical ribbon and the subcortical grey matter. The temporal semiology, 'reflex nature' pathophysiology correlates involvement of temporo-limbic structures/somatosensory cortex, while the involvement of structures like pre-cuneus, posterior cingulate, and frontal regions are in agreement with functional networks related loss of awareness. That bilateral amygdala swelling occurs in HWE is a novel observation and may signal that it could be a distinct variant of Mesial TLE.

Ictal Video-Electroencephalography Findings in Bathing Seizures: Two New Cases and Review of the Literature

INTRODUCTION

Reflex bathing seizures are described during the course of bathing in water near body temperature. These seizures differ from other epilepsies characterized by bathing-induced seizures such as hot water epilepsy, but there are few well-described patients and only some of these have been documented by ictal video-electroencephalography.

METHODS

Our objective was to characterize the clinical presentation of bathing-induced seizures demonstrated by ictal video-electroencephalographic recordings with water temperature below 38°C. We described two previously unreported infants and reviewed additional cases in the literature that fulfilled those criteria.

RESULTS

Eighteen infants were indentified. They were predominantly male (72%), and the mean age of seizure onset was 15 months (one to 36 months). The most frequent seizure triggers included pouring water over the face and immersion. Seizures were of focal onset with loss of awareness and prominent autonomic symptoms. Ictal video-electroencephalography revealed delta-theta high-amplitude focal waves involving temporal and adjacent regions, with a rapid spread to the ipsilateral hemisphere or generalization. Avoiding known triggers usually controlled the seizures, but carbamazepine, valproate, and levetiracetam were also helpful. Neuroimaging was normal in all cases, and neurodevelopment was unaffected.

DISCUSSION

Bathing seizures predominate in boys with an early onset and a benign self-limited course. The use of ictal video-electroencephalographic recordings in these cases leads to diagnosis and reveals individual differences in triggers.

Therapy for hyperthermia-induced seizures in Scn1a mutant rats

PURPOSE

Mutations in the SCN1A gene, which encodes the α1 subunit of voltage-gated sodium channels, cause generalized epilepsy with febrile seizures plus (GEFS+) and severe myoclonic epilepsy of infancy (SMEI). N1417H-Scn1a mutant rats are considered to be an animal model of human FS+ or GEFS+. To assess the pharmacologic validity of this model, we compared the efficacies of eight different antiepileptic drugs (AEDs) for the treatment of hyperthermia-induced seizures using N1417H-Scn1a mutant rats.

METHODS

AEDs used in this study included valproate, carbamazepine (CBZ), phenobarbital, gabapentin, acetazolamide, diazepam (DZP), topiramate, and potassium bromide (KBr). The effects of these AEDs were evaluated using the hot water model, which is a model of experimental FS. Five-week-old rats were pretreated with each AED and immersed in water at 45°C to induce hyperthermia-induced seizures. The seizure manifestations and video-electroencephalographic recordings were evaluated. Furthermore, the effects of each AED on motor coordination and balance were assessed using the balance-beam test.

KEY FINDINGS

KBr significantly reduced seizure durations, and its anticonvulsant effects were comparable to those of DZP. On the other hand, CBZ decreased the seizure threshold. In addition, DZP and not KBr showed significant impairment in motor coordination and balance.

SIGNIFICANCE

DZP and KBr showed potent inhibitory effects against hyperthermia-induced seizures in the Scn1a mutant rats, whereas CBZ exhibited adverse effects. These responses to hyperthermia-induced seizures were similar to those in patients with GEFS+ and SMEI. N1417H-Scn1a mutant rats may, therefore, be useful for testing the efficacy of new AEDs against FS in GEFS+ and SMEI patients.

A missense mutation of the gene encoding voltage-dependent sodium channel (Nav1.1) confers susceptibility to febrile seizures in rats

Although febrile seizures (FSs) are the most common convulsive syndrome in infants and childhood, the etiology of FSs has remained unclarified. Several missense mutations of the Na(v)1.1 channel (SCN1A), which alter channel properties, have been reported in a familial syndrome of GEFS+ (generalized epilepsy with febrile seizures plus). Here, we generated Scn1a-targeted rats carrying a missense mutation (N1417H) in the third pore region of the sodium channel by gene-driven ENU (N-ethyl-N-nitrosourea) mutagenesis. Despite their normal appearance under ordinary circumstances, Scn1a mutant rats exhibited remarkably high susceptibility to hyperthermia-induced seizures, which involve generalized clonic and/or tonic-clonic convulsions with paroxysmal epileptiform discharges. Whole-cell patch-clamp recordings from HEK cells expressing N1417H mutant channels and from hippocampal GABAergic interneurons of N1417H mutant rats revealed a significant shift of the inactivation curve in the hyperpolarizing direction. In addition, clamp recordings clearly showed the reduction in action potential amplitude in the hippocampal interneurons of these rats. These findings suggest that a missense mutation (N1417H) of the Na(v)1.1 channel confers susceptibility to FS and the impaired biophysical properties of inhibitory GABAergic neurons underlie one of the mechanisms of FS.

Intra-familial incidence and characteristics of hot water epilepsy

OBJECTIVE

To assess the clinical features of several members of the same family diagnosed with both hot water epilepsy (HWE) and cerebral lesions.

METHODS

Age at onset and types of seizure, precipitating factors, EEG findings, and neuroimages were evaluated.

RESULTS

The family consisted of six generations, including one consanguineous parent. Of eight family members diagnosed with epilepsy, seven suffered from HWE. Age at onset of seizures ranged within childhood. Seven patients with HWE experienced complex partial seizures, with or without secondary generalization; one experienced simple partial seizures as well as complex partial seizures. Three patients experienced spontaneous seizures as well as HWE. Interictal EEG revealed abnormalities in two patients. Magnetic resonance imaging revealed cerebral lesions in one patient, probably attributable to ischemic changes. Magnetic resonance images were consistent with findings of ischemic gliosis in two patients, and either demyelinating or ischemic gliosis in one patient.

CONCLUSIONS

Descriptions of HWE families with different ethnic backgrounds may permit more definite conclusions regarding the mechanisms epileptogenesis, and the genetic defects that underlie this disease.

A locus for autosomal dominant reflex epilepsy precipitated by hot water maps at chromosome 10q21.3-q22.3

Hot water epilepsy (HWE) is a form of reflex or sensory epilepsy wherein seizures are precipitated by an unusual stimulus, the contact of hot water over the head and body. Genome-wide linkage analysis of a large family with ten affected members, provided evidence of linkage (Z (max) = 3.17 at theta = 0 for D10S412) to chromosome 10q21. Analysis of five additional HWE families, for markers on chromosome 10, further strengthened the evidence of linkage to the same chromosomal region with three out of five families showing concordance for the disease haplotype and providing a two-point LOD score of 4.86 at theta = 0 and 60% penetrance for D10S412. The centromere-proximal and -distal boundaries of the critical genetic interval of about 15 Mb at 10q21.3-q22.3 were defined by D10S581 and D10S201, respectively. Sequence analysis of a group of functional candidate genes, the ion channels KCNMA1, VDAC2 and solute carriers SLC25A16, SLC29A3 revealed no potentially pathogenic mutation. We propose to carry out further analysis of positional candidate genes from this region to identify the gene responsible for this unusual neurobehavioral phenotype.

Genetic and environmental interactions determine seizure susceptibility in epileptic EL mice

Gene identification has progressed rapidly for monogenic epilepsies, but complex gene-environmental interactions have hindered progress in gene identification for multifactorial epilepsies. We analyzed the role of environmental risk factors in the inheritance of multifactorial idiopathic generalized epilepsy in the EL mouse. Seizure susceptibility was evaluated in the EL (E) and seizure-resistant ABP/LeJ (A) parental mouse strains and in their AEF1 and AEF2 hybrid offspring using a handling-induced seizure test. The seizure test was administered in three environments (environments I, II and III) that differed with respect to the number of seizure tests administered (one test or four tests) and the age of the mice when tested (young or old). The inheritance of seizure susceptibility appeared dominant after repetitive seizure testing in young or old mice, but recessive after a single test in old mice. Heritability was high (0.67-0.77) in each environment. Significant quantitative trait loci (QTL) that were associated with environments I and III (repetitive testing) were found on chromosomes 2 and 9 and colocalized with previously mapped El2 and El4, respectively. The El2 QTL found in environment I associated only with female susceptibility. A novel QTL, El-N, for age-dependent predisposition to seizures was found on proximal chromosome 9 only in environment II. The findings indicate that environmental risk factors determine the genetic architecture of seizure susceptibility in EL mice and suggest that QTL for complex epilepsies should be defined in terms of the environment in which they are expressed.

Self-induction behavior in patients with photosensitive and hot water epilepsy: a comparative study from a tertiary epilepsy center in Turkey

PURPOSE

The goal of this study was to compare self-induction (SI) patterns in photosensitive epilepsy (PSE) and hot water epilepsy (HWE).

METHODS

Among 7609 consecutive patients, 129 were diagnosed as having PSE, and 34, HWE.

RESULTS

Thirteen patients with PSE (10 females, 3 males, age at onset: 8.6; 3 with mental retardation) and 9 patients with HWE (all males, age at onset: 13.1) reported experiencing SI. During the seizures, a pleasurable feeling was described by all patients with HWE, but only by 3 patients with PSE. Patients with PSE induced their seizures by going very close to the TV screen or by waving their hands and blinking in front of the light sources. In the patients with HWE, seizures were precipitated by increasing the temperature of the water poured over the head or body.

CONCLUSIONS

Our results indicate that SI is more frequent in HWE, although this behavior was attributed mostly to PSE in previous studies.

Hot water epilepsy with cerebral lesion: a report of five cases with cranial MRI findings

Hot water epilepsy (HWE) is included in the reflex epilepsies. Although, in general, not common, HWE is concentrated in certain regions of the world. Different bathing habits and genetic factors may be responsible for the high incidence of HWE in these regions. However, the exact pathogenesis of HWE is not known. The facts that complex partial seizures are the most common clinical presentation and EEG recordings show an epileptic focus in the temporal lobe suggested the presence of a structural lesion in the temporal lobe. To our knowledge, however, there were no demonstrable structural changes on MRI and CT scans except in a few case reports. Here, we describe an additional five cases of HWE having an intracranial pathology, for example, hippocampal sclerosis, dysplasia, and a huge cystic lesion. We believe that investigations with new detailed neuroimaging techniques, in addition to experimental and clinical studies, might help us to understand the mechanism of this reflex epilepsy.

Hot water epilepsy occurring at temperature below the core temperature

A 6-year-old girl had water reflex epilepsy occurring at lower temperature than the core temperature. Seizures episodes consisted of a loss of consciousness absence followed by left predominant hypotonia with right fronto-temporal high voltage slow waves on the ictal-EEG. Seizures were only observed when the water was poured on scalp or face. Neuropsychological evaluation showed frontal dysfunction (Rey's figure). MRI study was normal. Oxcarbazepine permitted the disappearance of seizures and an improvement of executive disorders. In this case, the pathophysiological mechanism cannot be a hyperthermic related event. The temperature control as treatment of hot-water epilepsy could be used after the exploration of its implication in seizure induction.

The effects of the immature rat model of febrile seizures on the occurrence of later generalized tonic-clonic and absence epilepsy

This study was designed to investigate whether the intensity of experimental febrile seizures reduces the threshold to generalized tonic-clonic epilepsy and its effects on the development of generalized absence epilepsy in adulthood. For the evaluation of absence epilepsy, WAG/Rij rats and for the tonic-clonic seizures, PTZ injected Wistar rats were used. Our results showed that while the frequency of the experimental febrile seizures facilitates PTZ-induced generalized tonic-clonic seizures, it does not influence the properties of absence epileptic seizures in adulthood.

Hot-water epilepsy

Geographically specific epilepsy syndromes are of epidemiologic interest and may assist in understanding the pathogenic mechanism of epilepsy in general. Some may have a genetic basis with added environmental influence. Among these epilepsy syndromes in India is an interesting type of reflex seizure known as hot-water epilepsy (HWE) and single small computed tomography (CT)-enhancing lesions (SSCTLs).

Arginine vasopressin in the pathogenesis of febrile convulsion and temporal lobe epilepsy

We aimed to investigate the possible convulsant action of arginine vasopressin (AVP) in both a febrile convulsion model in rat pups and a temporal lobe epilepsy model in adult rats and to define the receptor type which mediates this effect. In rat pups, 125 ng V2 receptor antagonist significantly prevented hyperthermic seizures, but did not affect seizure latency. In adult rats, the only effective dose and agent was 125 ng V2 receptor antagonist, which prevented pilocarpine-induced status epilepticus, extended the status epilepticus latency and improved the 24 h survival rate. These data suggest that AVP has a convulsant activity in febrile convulsions and also in seizures independent of fever, and this effect is mediated by V2 receptors.

Hot water epilepsy: clinical and electrophysiologic findings based on 21 cases

PURPOSE

Our aim is to outline the clinical and electroencephalographic (EEG) features of patients with hot water epilepsy (HWE), a rare and unique form of reflex epilepsy.

METHODS

Twenty-one patients with HWE, seen in our clinic until 1999, were studied. Male outnumbered female subjects in a ratio of 3:1. The age at the onset of seizures ranged from 19 months to 27 years (mean age at onset, 12 years).

RESULTS

The main factors precipitating seizures were bathing with hot water and/or pouring water over the head. Six patients reported self-induction, either by increasing the heat or the amount of water and/or recalling earlier bathing experiences. Nine patients expressed feeling pleasure during the seizures. Twenty patients had partial seizures, eight of whom also had secondarily generalized seizures. One patient had apparent generalized seizures only. Spontaneous seizures were present in 62% of the cases. Interictal epileptogenic abnormalities were documented in the EEGs of eight patients; the other eight had normal EEGs. The major sites of epileptogenic activity were over the unilateral temporal regions (in 40% of patients). Neuroimaging studies available for 12 patients (four cranial computed tomography and eight cranial magnetic resonance imaging scans) revealed normal findings. Seizure control in patients who were followed up was achieved by reducing the temperature or the duration of the bath or shower; several of the patients required medication.

CONCLUSIONS

The major findings of this study are that HWE has a male preponderance, can be self-induced, is often done for pleasure, has complex triggering factors, and shows temporally located abnormalities in the EEGs. Although HWE is generally known to be self-limited, antiepileptic drug treatment may sometimes be necessary to control seizures. Hot water epilepsy should be classified separately among the epileptic syndromes.

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.

Effects of hyperthermia and continuous hippocampal stimulation on the immature and adult brain

Whether febrile seizures lead to hippocampal necrosis is a question of paramount clinical importance. This study attempted to simulate a complex febrile seizure, compared with hyperthermia (HYP) alone and prolonged seizure alone (produced by continuous hippocampal stimulation (CHS)). Four groups of rats were studied at each of two ages, immature (postnatal day, P20) and adult (P60). Group 1 was subjected to 45 min of HYP (body temperature 40 degrees C) plus CHS, Group 2 received 45 min of HYP alone, Group 3 got 45 min of CHS alone, and Group 4 was sham-handled control rats. Baseline and post-session EEGs were recorded in all groups. Subsequently, brains were examined histologically for evidence of hippocampal damage. Both CHS-treated groups (with and without HYP) exhibited behavioral and EEG seizures while the group undergoing HYP alone did not have seizures. There were no gross histological lesions in any group. Cell counts in regions CA1, CA3, dentate gyrus and dentate hilus did not differ in rats under any condition of hyperthermia and CHS, in either P20 or P60 rats compared to age-matched controls. These results indicate that both immature and mature rodents are resistant to hyperthermic brain damage and raises the question of whether febrile seizures play a role in the genesis of mesial temporal sclerosis.

The neuropathology of hyperthermic seizures in the rat

PURPOSE

Single and repeated hyperthermic seizures were induced in rats beginning at age 22 days to determine the neuroanatomic consequences to the hippocampus and to compare these changes with those in the hippocampi of patients with temporal lobe epilepsy (TLE) experiencing febrile seizures.

METHODS

Hyperthermic seizures were induced by placing rats in a bath of water at 45 degrees C for 4 min. Seizures were visually observed, and some animals also were monitored electroencephalographically. Neurodegeneration was examined with a silver stain, whereas granule cell sprouting was detected with the Timm stain.

RESULTS

In a majority of rats, hyperthermia-induced tonic-clonic seizures ranged in duration from 30 s to 6 min; the seizure duration increased with the number of seizures. No neurodegeneration was detectable in these animals, although there was sprouting of granule cell collaterals into the inner molecular layer (IML) of the dentate. In a small number of animals, the short seizures evolved into status epilepticus, and neuronal degeneration was present in the hippocampus and other parts of the temporal lobe, and the mediodorsal thalamus.

CONCLUSIONS

This study confirms the relation between hyperthermia and seizure occurrence. It shows in particular that, as in the human, only prolonged seizures such as status epilepticus cause a pattern of neurodegeneration similar to that observed in human TLE.

Acute heat stress model of seizures in weanling rats: influence of prototypic anti-seizure compounds

The present study tested the therapeutic potential for prototype anti-epilepsy drugs using an animal model of infantile febrile seizures. The model consisted of immersion of weanling rats (21 days old) in a 45 degrees C water bath for a maximum of 4 min (four exposures over a 2 week period) and observing for the progression to stage-5 seizures. All compounds were administered orally at the respective ED50 for prevention of seizures in the maximal electroshock (MES) test. Clonazepam effectively lowered the score for seizure grade, shortened the duration of seizures, as well as reduced the number of animals experiencing seizures during three of the four testing periods. MK801 reduced both the maximum seizure grade, and the number of animals experiencing seizures during sessions two and three. However, the dose of MK801 caused behavioral side effects. Valproate actively decreased seizure grade, while it modestly acted to attenuate seizure duration, extended the time to seizure onset, and reduced the number of animals experiencing seizures on testing day 1. Remacemide hydrochloride and phenobarbital were not effective. The method appears useful for evaluating the potential of agents to prevent acute febrile seizures.

Hyperthermic seizures: an animal model for hot-water epilepsy

Freely ambulant wistar adult rats of both sexes when exposed to a hot water jet on the head (50 degrees C - 55 degrees C) for a period of 8-10 minutes, manifested seizure activity similar to the ones noted in 'hot-water epilepsy' (HWE) in humans. Depth electrode recording from the hippocampus revealed seizure discharges during the ictus lasting from 34 seconds to three minutes, followed by low voltage indeterminate activity and a quiescent resting phase. Seizure initiation was noted to be critically dependent on the rectal temperature of 41.5 degrees C and regional hippocampal temperature of 37 degrees C. There appeared to be no clear evidence for kindling phenomenon. Intervention of hyperthermia by cooling the body after the ictus prevented subsequent occurrence of spontaneous seizures. Pathological study of the brain revealed ischaemic changes in specific topographic areas like Sommer's sector in hippocampus, layer 4 and 5 neurons of the cerebral cortex and reticular neurons in the brain stem- a pathological feature reminiscent of the human epileptic brain. Seizure initiation by hyperthermic stimulation with hot water poured over the head, the progression and the EEG recording the seizure activity in these rats appears to resemble the HWE in human subjects and could thus serve as the first animal model for this form of "reflex' epilepsy. This has given new insight into the understanding of human HWE. Our preliminary observations in humans has suggested that HWE is a type of hyperthermic seizure similar to febrile convulsion but differs from it with respect to stimulus and rate of rise in temperature in a susceptible individual.

The pathogenic role of the NMDA receptor in hyperthermia-induced seizures in developing rats

Hyperthermia-induced seizures (HS) in rats have been used as a model of febrile seizures. Activation of the N-methyl-D-aspartate (NMDA) receptor by increased extracellular glutamate (Glu) in the cortex during hyperthermia may be involved in the induction of HS and HS kindling. To confirm this hypothesis, the effects of a potent blocker of the NMDA receptor, MK-801, on the threshold and pattern of HS were evaluated. The threshold temperatures for rats given 0.1 (low dose) and 0.5 (high dose) mg/kg MK-801 (i.p.) for the first time were 41.6 degrees C (39.7-42) (median, range) and 42.0 (41.2-42.0), respectively, which were significantly higher than the 40.5 (39.4-41.2) for rats without MK-801 administration (P < 0.01). The recurrent occurrence of HS suppressed the increase in the threshold temperature with age, and changed the seizure from partial to generalized seizures (HS kindling), whereas these effects of recurrent HS on the threshold and pattern of HS were inhibited by the high dose (0.5 mg/kg) of MK-801. MK-801 blocks HS and HS kindling. The activation of the NMDA receptor during hyperthermia plays an important role in the induction of HS and HS kindling.

Hot water epilepsy

The clinical and EEG features of 10 patients with hot water epilepsy were presented. Eight of the 10 cases were male. The mean age of onset was 4.7 years. In four patients partial and in six cases generalized seizures were seen. Three patients also had non-hot water precipitated seizures. Interictal EEGs showed generalized abnormalities in eight and focal abnormalities in two cases. CT was performed and found normal in two patients. Anticonvulsant therapy was instituted for all patients. In six cases with adequate follow-up, complete remission was obtained in four and the frequency of the seizures was decreased in two, with anticonvulsant therapy.

Induction of epileptiform activity by temperature elevation in hippocampal slices from young rats: an in vitro model for febrile seizures?

Extracellular field potential recordings were performed in the CA1 subfield of hippocampal slices obtained from Wistar rats aged 2-38 days. When the brain tissue was maintained at 35 degrees-36 degrees C (values obtained in the tissue chamber well), single-shock orthodromic stimuli elicited a response in the stratum pyramidale that consisted of a single population spike. In contrast, when the temperature in the well was increased to levels greater than 38.2 degrees C for periods of 5-15 min, the same type of stimuli elicited an epileptiform response characterized by a 250- to 600-ms-long, positive-going field potential with superimposed, multiple, negative-going population spikes. This potential resembled the epileptiform response recorded in the hippocampal slice in the presence of convulsants such as penicillin or bicuculline. Once the temperature was restored to control values (i.e., 35 degrees-36 degrees C) after induction of epileptiform activity, the abnormal response could be observed for less than or equal to 2 h. In some experiments (approximately one third of the successful trials), spontaneous epileptiform discharges appeared during and persisted after the increase in temperature. The ability of the hyperthermic period to induce epileptiform changes was age dependent: Epileptiform activity outlasting the period of temperature elevation was not observed in slices obtained from rats aged less than 4 days or greater than 28 days. Our data show that epileptiform activity can be induced by a transient increase in temperature and that the age of the animals from which slices are obtained plays an important role in the appearance of this phenomenon.(ABSTRACT TRUNCATED AT 250 WORDS)

Hyperthermia sensitizes rats to cocaine's proconvulsive effects and unmasks EEG evidence of kindling after chronic cocaine

In phase I, 64 male and female Sprague-Dawley rat siblings from 8 litters were divided equally among 4 treatment groups; saline plus normothermia (S37), saline plus hyperthermia (S45), cocaine (30 mg/kg) plus normothermia (C37), and cocaine plus hyperthermia (C45) and treated daily from 45-60 days of age. Cocaine plus hyperthermia produced protracted, intense and often fatal convulsions, whereas animals from either treatment alone did not convulse. Subsequently, 12 males, representing all phase I treatment groups equally, were implanted with telemetric transmitters to monitor the EEG and core body temperature in phase II. Survivors of this second phase were exposed to one trial each of saline plus hyperthermia, cocaine plus normothermia, and cocaine plus hyperthermia, in that order. The data obtained suggests that 1) the telemetered EEG and temperature can be used to detect changes reflecting sensitization/kindling in the absence of behavioral expression (convulsions), 2) analysis of EEG power spectral bands and body temperature curves showed that a history of daily cocaine exposure seems to have contributed more than daily hyperthermia to subsequently observed seizure patterns and thermic responses, and, finally, 3) cocaine plus hyperthermia resulted in a shorter latency to convulse and a lower maximal EEG seizure voltage, while increasing the variety, severity and duration of its behavioral expression (convulsion).

Hot-water epilepsy: a variant of reflex epilepsy in southern India

"Hot water epilepsy" (HWE), precipitated by a bath or shower in hot water, has been described infrequently in the literature. We report 279 cases of HWE that were seen between 1980 to 1983 in Bangalore, South India. We found HWE to be more common in children, with cases more frequent among male than female patients (2.6:1). Complex partial seizures constituted the main clinical presentation (67.0%); HWE accounted for 4.4% of all complex partial seizures and generalize tonic-clonic seizures seen at our center during the 1980-1983 period. Although prognosis seems favorable 25.4% of our patients developed nonreflex epilepsy within 1-3 years. They were managed with antiepileptic drugs and the use of lukewarm water for bathing.

Kindling phenomenon of hyperthermic seizures in the epilepsy-prone versus the epilepsy-resistant rat

A kindling-like effect was produced by exposing 30-day-old rats to repeated hyperthermia-induced seizures. Naive audiogenic seizure (AGS)-susceptible rats (P77PMC) were easier to be kindled than AGS-resistant rats (Wistar). This hyperthermic kindling model may be used to study the outcome and mechanisms of human febrile seizures. The mechanisms underlying hyperthermic kindling remain to be investigated.