Epileptiform activity initiated by pial iontophoresis of ferrous and ferric chloride on rat cerebral cortex

Ferroptosis and Pyroptosis in Epilepsy

Epilepsy is sudden, recurrent, and transient central nervous system dysfunction caused by abnormal discharge of neurons in the brain. Ferroptosis and pyroptosis are newly discovered ways of programmed cell death. One of the characteristics of ferroptosis is the oxidative stress generated by lipid peroxides. Similarly, pyroptosis has unique pro-inflammatory properties. As both oxidative stress and neuroinflammation are significant contributors to the pathogenesis of epilepsy, increasing evidence shows that ferroptosis and pyroptosis are closely related to epilepsy. This article reviews the current comprehension of ferroptosis and pyroptosis and elucidates potential mechanisms by which ferroptosis and pyroptosis may contribute to epilepsy. In addition, we also highlight the possible interactions between ferroptosis and pyroptosis because they reportedly coexist in many diseases, and increasing studies have demonstrated the convergence of pathways between the two. This is of great significance for explaining the occurrence and development of epilepsy and provides a new therapeutic perspective for the treatment of epilepsy.

Redox-Related Neuronal Death and Crosstalk as Drug Targets: Focus on Epilepsy

Cell death has a vital role in embryonic development and organismal homeostasis. Biochemical, pharmacological, behavioral, and electrophysiological evidences support the idea that dysregulation of cell death programs are involved in neuropathological conditions like epilepsy. The brain is particularly vulnerable to oxidative damage due to higher oxygen consumption and lower endogenous antioxidant defense than other bodily organ. Thus, in this review, we focused on the comprehensive summarization of evidence for redox-associated cell death pathways including apoptosis, autophagy, necroptosis, and pyroptosis in epilepsy and the oxidative stress-related signaling in this process. We specially proposed that the molecular crosstalk of various redox-linked neuronal cell death modalities might occur in seizure onset and/or epileptic conditions according to the published data. Additionally, abundance of polyunsaturated fatty acids in neuronal membrane makes the brain susceptible to lipid peroxidation. This presumption was then formalized in the proposal that ferroptosis, a novel type of lipid reactive oxygen species (ROS)-dependent regulatory cell death, is likely to be a critical mechanism for the emergence of epileptic phenotype. Targeting ferroptosis process or combination treatment with multiple cell death pathway inhibitors may shed new light on the therapy of epilepsy.

Subclinical early posttraumatic seizures detected by continuous EEG monitoring in a consecutive pediatric cohort

PURPOSE

Traumatic brain injury (TBI) is an important cause of morbidity and mortality in children, and early posttraumatic seizures (EPTS) are a contributing factor to ongoing acute damage. Continuous video-EEG monitoring (cEEG) was utilized to assess the burden of clinical and electrographic EPTS.

METHODS

Eighty-seven consecutive, unselected (mild - severe), acute TBI patients requiring pediatric intensive care unit (PICU) admission at two academic centers were monitored prospectively with cEEG per established clinical TBI protocols. Clinical and subclinical seizures and status epilepticus (SE, clinical and subclinical) were assessed for their relation to clinical risk factors and short-term outcome measures.

KEY FINDINGS

Of all patients, 42.5% (37/87) had seizures. Younger age (p = 0.002) and injury mechanism (abusive head trauma - AHT, p < 0.001) were significant risk factors. Subclinical seizures occurred in 16.1% (14/87), while 6.9% (6/87) had only subclinical seizures. Risk factors for subclinical seizures included younger age (p < 0.001), AHT (p < 0.001), and intraaxial bleed (p < 0.001). SE occurred in 18.4% (16/87) with risk factors including younger age (p < 0.001), AHT (p < 0.001), and intraaxial bleed (p = 0.002). Subclinical SE was detected in 13.8% (12/87) with significant risk factors including younger age (p < 0.001), AHT (p = 0.001), and intraaxial bleed (p = 0.004). Subclinical seizures were associated with lower discharge King's Outcome Scale for Childhood Head Injury (KOSCHI) score (p = 0.002). SE and subclinical SE were associated with increased hospital length of stay (p = 0.017 and p = 0.041, respectively) and lower hospital discharge KOSCHI (p = 0.007 and p = 0.040, respectively).

SIGNIFICANCE

cEEG monitoring significantly improves detection of seizures/SE and is the only way to detect subclinical seizures/SE. cEEG may be indicated after pediatric TBI, particularly in younger children, AHT cases, and those with intraaxial blood on computerized tomography (CT).

Hippocampal gene expression profiling in a rat model of posttraumatic epilepsy reveals temporal upregulation of lipid metabolism-related genes

Traumatic brain injury occasionally causes posttraumatic epilepsy. To elucidate the molecular events responsible for posttraumatic epilepsy, we established a rodent model that involved the injection of microliter quantities of FeCl3 solution into the amygdalar nuclear complex. We previously compared hippocampal gene expression profiles in the traumatic epilepsy model and normal rats at 5 days after brain injury (acute phase) to determine the role of inflammation. In this study, we focused on later stages of epileptogenesis. We compared gene expression profiles at 5, 15 (sub-chronic phase), and 30 days (chronic phase) after brain injury to identify temporal changes in molecular networks involved in epileptogenesis. A total of 81 genes were significantly (at least twofold) up- or downregulated over the course of disease progression. We found that genes related to lipid metabolism, namely, Apoa1, Gh, Mc4r, Oprk1, and Pdk4, were temporarily upregulated in the sub-chronic phase. Changes in lipid metabolism regulation might be related to seizure propagation during epileptogenesis. This temporal description of hippocampal gene expression profiles throughout epileptogenesis provides clues to potential markers of disease phases and new therapeutic targets.

Hippocampal gene network analysis in an experimental model of posttraumatic epilepsy

In the present study, we performed comprehensive gene expression and gene network analyses using a DNA microarray to elucidate the molecular events responsible for the pathology of posttraumatic epilepsy at the partial seizure stage. We used an experimental posttraumatic epilepsy model of amygdalar focal FeCl(3)-injected rats and compared gene expression profiles in the hippocampus at the partial seizure stage (less than stage 3 on Racine's convulsion scale) and that of sham-operated animals. At the partial seizure stage, upregulation of phospholipase A2 (PLA2) and lipid metabolism were observed, which have been reported to be caused by brain injury and seizures in previous studies. Furthermore, significant upregulation of genes related to inflammation and the immune system was observed. These molecular changes in PLA2 and lipid metabolism may be related to seizure propagation.

Posttraumatic epilepsy: hemorrhage, free radicals and the molecular regulation of glutamate

Traumatic brain injury causes development of posttraumatic epilepsy. Bleeding within neuropil is followed by hemolysis and deposition of hemoglobin in neocortex. Iron from hemoglobin and transferring is deposited in brains of patients with posttraumatic epilepsy. Iron compounds form reactive free radical oxidants. Microinjection of ferric ions into rodent brain results in chronic recurrent seizures and liberation of glutamate into the neuropil, as is observed in humans with epilepsy. Termination of synaptic effects of glutamate is by removal via transporter proteins. EAAC-1 is within neurons while GLT-1 and GLAST are confined to glia. Persistent down regulation of GLAST production is present in hippocampal regions in chronic seizure models. Down regulation of GLAST may be fundamental to a sequence of free radical reactions initiated by brain injury with hemorrhage. Administration of antioxidants to animals causes interruption of the sequence of brain injury responses induced by hemorrhage, suggesting that such a strategy needs to be evaluated in patients with traumatic brain injury.

Inhibitory role of Acorus calamus in ferric chloride-induced epileptogenesis in rat

The roots and rhizomes of Acorus calamus (Family: Araceae) have been used in the ancient systems of medicine for the treatment of various neurological disorders. Of the various methods used for inducing experimental epileptic models, the intracortical administration of ferric chloride (FeCl(3)) into sensorimotor cortex induces recurrent seizures and epileptic discharge similar to human post-traumatic epilepsy through the generation of free radicals. The present study focuses on the effect of Acorus calamus on the behavioral, electroencephalographic, and antioxidant changes in FeCl(3)-induced rat epileptogenesis. Topical administration of FeCl(3) (5 microL; 100 mM) into the sensorimotor cortex of rats showed an increase in the wet dog shake behavior, spike wave discharges together with an significant increase in antioxidant enzyme activity, such as superoxide dismutase and catalase, resulting in an increase in the level of lipid peroxidation in cerebral cortex. Pretreatment with Acorus calamus (200 mg/kg b.w., p.o. for 14 days) and also diazepam (DZ, 20 mg/kg b.w., i.p.) decreased the WDS behavior, spike wave discharges with single isolated positive waves, and a significant decrease in activity of superoxide dismutase and level of lipid peroxidation was observed in cerebral cortex with respect to those observed in FeCl(3)-induced epileptic group. Data presented in this study clearly show that Acorus calamus possesses the ability for preventing the development of FeCl(3)-induced epileptogenesis by modulating antioxidant enzymes, which in turn exhibit the potentiality of Acorus calamus to be developed as an effective anti-epileptic drug.

Functional role for redox in the epileptogenesis: molecular regulation of glutamate in the hippocampus of FeCl3-induced limbic epilepsy model

We used western blotting to measure the quantity of glutamate and gamma-aminobutyric acid (GABA) transporters proteins within hippocampal tissue obtained from rats who had undergone epileptogenesis. Chronic seizures were induced by amygdalar injection of FeCl(3). We found that the glial glutamate transporters GLAST and GLT-1 were down-regulated at 60 days after initiation of chronic and recurrent seizures. However, the neuronal glutamate transporter EAAC-1 and the GABA transporter GAT-3 were increased. We performed in vivo microdialysis in freely moving animals to estimate in vivo redox state. We found that the hippocampal tissues were oxidized, resulting in even further impairment of glutamate transport. Our data show that epileptogenesis in rats resulting in chronic and recurrent seizures is associated with collapse of glutamate regulation caused by both the molecular down-regulation of glial glutamate transporters combined with the functional failure due to oxidation.

Effect of levetiracetam on molecular regulation of hippocampal glutamate and GABA transporters in rats with chronic seizures induced by amygdalar FeCl3 injection

Enhancement of the glutamatergic excitatory synaptic transmission efficacy in the FeCl3 induced epilepsy model is associated with changes in the levels of glutamate and GABA transporter proteins. This study examined the effect of levetiracetam (LEV) on glutamate overflow and glutamate/GABA transporters expression in rats with epileptogenesis induced by the amygdalar injection of 1.0 microl of 100 mM FeCl3 (epileptic rat) and in control rats receiving amygdalar acidic saline injection (non-epileptic rat). In amygdalar acidic saline injected rats, 40 mM KCl-evoked glutamate overflow was significantly suppressed by both 32 and 100 microM LEV co-perfusion. In unilateral amygdalar FeCl3 injected rats, 32 microM LEV was ineffective, but the 100 microM LEV statistically suppressed glutamate overflow. Western blotting was employed to determine the hippocampal expression of glutamate/GABA transporters in epileptic or non-epileptic rats. The rats were treated for 14 days with 54 mg/kg LEV or vehicle intraperitoneally injection. Following 14 days of treatment, the ipsilateral hippocampus was removed for a Western blot analysis. In non-epileptic rats, the expression increased for all of the glutamate and GABA transporters (GLAST, GLT-1, EAAC-1, GAT-1 and GAT-3) while the glutamate transporter regulating protein (GTRAP3-18) decreased in comparison to those of normal rats that were treated with the vehicle. In epileptic rats receiving LEV, the EAAC-1 and GAT-3 levels increased while GTRAP3-18 (89%) decreased in comparison to those of the epileptic rats treated with the vehicle. GTRAP3-18 inhibitor regulates glutamate-binding affinity to EAAC-1. The anti-epileptic action of LEV may be partially due to a reduction of glutamate-induced excitotoxicity and an enhancement of the GABAergic inhibition as observed with the inhibitory effect on the 40 mM KCl-evoked glutamate overflow. These conclusions are supported by the increase in the expression of glial glutamate transporters (GLAST and GLT-1), and the increase in the expression of EAAC-1 and GAT-3 associated with a decrease in GTRAP3-18. The increased expression of EAAC-1 and the decreased expression of GTRAP3-18 in association with the up-regulation of GAT-3 due to such continual LEV administration was thus found to enhance GABA synthesis and reverse the transport of GABA both in non-epileptic and epileptic rats. The suppression of glutamate excitation and the enhancement of GABA inhibition in the rats with continual LEV administration is a result of the up-regulation of glutamate and GABA transporters with the down-regulation of GTRAP3-18. These observations together demonstrated the critical molecular mechanism of the anti-epileptic activity of LEV.

The significance of folic acid for epilepsy patients

The following is a comprehensive review of the current understanding of the many important roles of folic acid in the health of patients with epilepsy. A review of past and current literature reveals that folic acid plays important roles in the areas of hematology, neurology, development, and reproduction. Also highlighted are new areas for exploration.

alpha-Tocopheryl-L-ascorbate-2-O-phosphate diester, a hydroxyl radical scavenger, prevents the occurrence of epileptic foci in a rat model of post-traumatic epilepsy

Intracortical injection of iron ions has been used to model post-traumatic epilepsy. The results obtained using these models suggest that oxidation of neural membranes by active oxygen free radicals may be involved in the etiology of post-traumatic epilepsy. This is a study of the effects of alpha-tocopheryl-L-ascorbate-2-O-phosphate diester potassium salt (EPC-K1), known as a hydroxyl radical scavenger, on the peroxidation of neural membranes by FeCl(3) in vitro and on the occurrence of epileptic discharges in the FeCl(3) injected post-traumatic epilepsy model rats. EPC-K1 dose-dependently inhibited the production of thiobarbituric acid reactive substances (TBARS) and protein carbonyl (P-Carb), both indices of biogenic macromolecular peroxidation. In vivo studies, sporadic spike discharges and/or epileptiform activities were observed in electrocorticograms (ECoG) of male Sprague-Dawley rat 15-90 min after 500 nmol of FeCl(3) was injected into the motor cortex. On the other hand, when 200 mg/kg of EPC-K1 was injected intraperitoneally 60 min prior to the injection of FeCl(3), the occurrence of epileptic discharges was prevented or delayed. When EPC-K1 (2.5-5 nmol) was injected along with the ferric ions, the occurrence of epileptiform activities was also prevented or delayed. EPC-K1 prevented the induction of early convulsion, the major risk factor of post-traumatic epilepsy. Rats in the Fe+EPC group were injected with 500 nmol of FeCl(3) into the left motor cortex and were given an EPC-K1-diet (CE-2 chow contained 0.2% of EPC-K1, and daily EPC-K1 intake was about 80 mg/kg/day). In the Fe+EPC group rats, the percent induction of epileptic discharges in ECoGs was significantly lower than that in the Fe+CE group rats, which were fed CE-2 after FeCl(3) injection. In the homotropic contra lateral cortex, TBARS and P-Carb content did not show any changes. However, the relative TBARS content in the focal area significantly increased in the Fe+CE and Fe+EPC group rats 3 h after the injection. It became normal 3 days after in the Fe+EPC group. The relative P-Carb content in the focal area significantly increased in the Fe+CE and Fe+EPC group rats 3 h after the injection. However, it became normal after 3 days. In the present study, EPC-K1, which consists of vitamins E and C connected by a phosphate, protected the oxidation of neural membranes and prevented the occurrence of ferric ion-induced epileptic discharges by its radical scavenger activity. These data suggest that EPC-K1 may be clinically useful in not only preventing the focus formation of post-traumatic epilepsy, but also in treating and attenuating the progression of free radical-induced degenerative disorders.

Comparative effects of metal chelating agents on the neuronal cytotoxicity induced by copper (Cu+2), iron (Fe+3) and zinc in the hippocampus

The ability of metal chelating agents to prevent neuronal death caused by intra-hippocampal injections of cupric sulphate, ferric citrate and zinc chloride was investigated. Ammonium tetrathiomolybdate was itself toxic after injection into the hippocampus, but this toxicity was reduced by formation of a metal ion/tetrathiomolybdate complex with Cu+2. Disodium bathocuproine disulphonate (BCDS) prevented neuronal death caused by Cu+2, but not that induced by Fe+3 or Zn+2. Desferrioxamine prevented death caused by Fe+3, had no significant effect of the toxicity of Zn+2, and increased that caused by Cu+2. Even though N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) has a higher affinity for Cu+2 than for Zn+2, TPEN had no effect on the toxicity of Cu+2 while totally preventing damage caused by Fe+3 or Zn+2. Ethylenediaminetetra-acetic acid (EDTA) prevented the toxicity of all three metal ions. Motor seizure activity occurred in most rats after injections of Fe+3; or combinations of Cu+2 plus TPEN, or 4 nmol Fe+3 plus 0.1 nmol desferrioxamine. However, apart from the low dose desferrioxamine/Fe+3 combination, only the occasional brain contained seizure-induced neuronal loss in limbic regions outside the injected hippocampus, and these brains were not used for analysis. Seizure activity was found even with very low levels of Cu+2 with a fixed amount of TPEN (a ratio of Cu+2/TPEN of 1:100), but the extent of hippocampal damage in these brains was not significantly different to that caused by injections of saline. These studies demonstrate that idiosyncratic interactions can occur between metal ions and chelating agents. Thus further investigations are needed before chelating agents can be examined for their protective properties in various neurodegenerative diseases.

Effects of hemoglobin and its breakdown products on synaptic transmission in rat hippocampal CA1 neurons

During head injuries and hemorrhagic stroke, blood is released into the extravascular space. The pooled erythrocytes get lysed and hemoglobin is released into the intracranial cavities. Therefore, neurons may be exposed to hemoglobin and/or its breakdown products, hemin and iron, for long periods of time. In this study, the electrophysiological actions of these agents on synaptic transmission in rat hippocampal CA1 pyramidal neurons were studied using extracellular field- and whole cell patch-recordings. Previously our laboratory reported that commercially available hemoglobin produced a dose dependent suppression of synaptic transmission in hippocampal CA1 neurons. In the present study, however, we found that this depression was caused by impurities present in the hemoglobin samples. Commercially available hemoglobin and methemoglobin did not have a significant effect on synaptic transmission. Although, reduced-hemoglobin prepared using a method described by Martin et al. [J. Pharm. Exp. Ther. 232 (1985) 708], produced a significant depression of synaptic transients, these effects were due to contamination with bisulfite that was present due to the reducing procedure. Therefore, the technique of Martin et al. was inadequate in removing the reducing agents or their breakdown products. A number of studies in literature used commercial samples of hemoglobin or reduced hemoglobin prepared using the method of Martin et al. Our observations indicate that it would be important to determine if contaminants, rather than hemoglobin, are responsible for the observed effects in these studies. Unlike hemoglobin, its breakdown products, ferrous chloride and hemin, produced an irreversible and significant depression of field excitatory postsynaptic potentials. The relevance of these effects in neurological complications that follow head injuries and hemorrhagic stroke awaits further investigation.

Melatonin inhibits iron-induced epileptic discharges in rats by suppressing peroxidation

PURPOSE

Intracortical injection of iron ion induces recurrent seizures and epileptic discharges in the electrocorticogram. This observation may be used as a model of posttraumatic epilepsy. The involvement of iron-mediated oxygen free radical species and neuronal lipid peroxidation in iron-induced seizure has been suggested. Melatonin exerts free radical scavenging properties. In this study, we examined the protective effect of melatonin against iron-induced seizures.

METHODS

We examined the protective effect of melatonin against in vitro iron-induced oxidative damage in homogenates from rat cerebral cortex, by measuring the concentration of thiobarbituric acid reactive substances (TBARS), as an index of oxidative damage. We also examined the effect of melatonin on the appearance of epileptic discharges in the EEG following injection of FeCl3 into the sensorimotor cortex in anesthetized rats, and by measuring the concentration of TBARS in the brain tissue.

RESULTS

FeCl3 increased the concentration of TBARS in brain homogenates in a concentration-dependent manner, and melatonin reduced FeCl3-induced rise in TBARS in a dose-response fashion. Pretreatment with melatonin suppressed or delayed the development of FeCl3-induced epileptic discharges and decreased the concentration of TBARS in brain tissues.

CONCLUSIONS

Our results suggest that iron ion generates oxygen free radical species that induce neuronal macromolecular peroxidation and seizure, and that melatonin inhibits iron-induced seizures by scavenging free radicals.

[Characteristics of epileptic seizures after ischemic stroke]

Cerebral infarctions are one of the most important causes of late onset epilepsy. We have studied 35 patients who presented epileptic seizures after ischemic stroke. All of them had the first seizure at least 24 hours after the stroke, and they had at least one recurrence of seizure. The objective was to determine the main characteristics of these seizures and to correlate them to clinical and laboratorial findings. The interval between the stroke and the first seizure was 3 to 1650 days. Late onset seizures (> 14 days) were present in 89%, they occurred predominantly 6 to 12 months after stroke. Partial seizures (31/35) were more frequent than generalized ones. Status epilepticus occurred in only 3 cases. Most of the patients (30/35) had occasional seizures (< or = 1 seizure monthly). There were no association between seizure type and the time interval between the stroke and the first seizure, neither with the seizure frequency. The most frequent EEG finding was focal slowing of cerebral activity. Pharmacological control was easily obtained. No patient needed more than one drug for seizure control.

[Subsidiary predictive tests in epileptic crisis after ischemic stroke]

We studied subsidiary laboratorial tests such as serum glucose, red blood cell count, total cholesterol, HDL and LDL cholesterol and triglycerides, electrocardiogram, electroencephalogram (EEG), cerebrospinal fluid, and CT scan of 35 patients with cerebral infarction who developed epileptic seizures (group 1 or G1), and compared them to a group of 35 patients who had cerebral infarction but have not developed epileptic seizures (group 2 or G2). The EEG analysis showed significance in the comparison between the groups; focal identification of the electrical cerebral activity was the most frequent abnormality found in G1. Extensive infarcts were also more frequent in G1. The association of abnormal EEG and extensive lesion on CT may be considered a preditive factor for occurrence of epileptic seizures after cerebral infarction. The analysis of the other tests showed no significance on the comparison between the groups.

Reduction in nitric oxide synthase activity with development of an epileptogenic focus induced by ferric chloride in the rat brain

Intracortical injection of iron ion has been shown to induce recurrent seizures and epileptic discharges in electrocorticograms. The importance of the effects of NO on seizure control systems and their regulation is suggested. In this paper, we examined the changes in nitric oxide synthase (NOS) activity in the epileptogenic focus induced by intracortical injection of iron ion at 5 min, 10 min, 1 h, 3 h and 3 days. Iron ion significantly decreased NOS activity in the cortex at the injection site 5 min, 3 h and 3 days after injection. These results suggest that the formation of an epileptic focus induced by iron ion is accompanied by decreased NOS activity.

Electrophysiological actions of hemoglobin on rat hippocampal CA1 pyramidal neurons

Hemoglobin, the oxygen-carrying component of red blood cells, can be released from erythrocytes in hemorrhagic stroke and intracranial bleeding associated with head injuries. Therefore, neurons may be exposed to this agent. In addition, hemoglobin can chelate nitric oxide (NO) and has been used in studying the role of NO in synaptic plasticity and excitotoxicity. However, the electrophysiological actions of hemoglobin on central neurons are not well characterized. In the present investigation, the electrophysiological actions of hemoglobin on CA1 pyramidal neurons in rat hippocampal slices were studied with conventional intracellular pointed microelectrode- as well as perforated patch-recordings. Superfusion of rat hippocampal slices with hemoglobin (0.05 or 0.1 mM for 10-15 min) induced a depolarization of CA1 neurons and suppressed the stratum radiatum stimulation-induced excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs). The hemoglobin-induced depolarization as well as the suppression of the synaptic transients were present in slices pretreated with 0.1 or 0.5 mM of N omega-nitro-L-arginine, a nitric oxide synthase inhibitor, suggesting that hemoglobin has electrophysiological actions on hippocampal CA1 neurons that are independent of its NO scavenging property.

Adenosines scavenged hydroxyl radicals and prevented posttraumatic epilepsy

Intracortical injection of iron ions has been used as a model of posttraumatic epilepsy. Oxidation of lipids in neural membranes by reactive oxygen species, especially hydroxyl radicals (OH), is involved in the mechanisms responsible for iron-induced seizures. We examined the scavenging effects of adenosine (Ado) and 2-chloroadenosine (Cl-Ado) on OH radicals and superoxide (O2.-) using an electron spin resonance (ESR) spectrometer, and the occurrence of epileptic discharges in electrocorticogram (ECoG) induced by FeCl3 injection into the sensorimotor cortex of rats. Though DMPO-O2.- spin adducts generated by the hypoxanthine-xanthine oxidase system were not quenched by Ado or Cl-Ado, 5 mM of each showed a quenching effect on DMPO-OH spin adducts (5.3 x 10(16) spins/ml) generated by the Fenton reagent. In ECoG of rats, spike discharges appeared 15-45 min after FeCl3 injection (500 nmol) into the sensorimotor cortex, and polyspikes and/or ictal patterns were observed 70-90 min after the injection. Cl-Ado (1 mg/kg) or Ado (5 mg/kg) injected intraperitoneally 30 min prior to the FeCl3 injection suppressed or delayed the occurrence of epileptic discharges induced by FeCl3. Cl-Ado and Ado may suppress the occurrence of epileptic discharges by scavenging OH and by their anticonvulsant effect.

Chaotic activity during iron-induced "epileptiform" discharge in rat hippocampal slices

Low-dimensional chaotic dynamics have been suggested in the rat hippocampal slice during iron-induced epileptiform activity. The dimensionality of this chaotic activity has been found to be similar in slices bathed in the same ionic extracellular medium. Some slices also displayed a drop in dimensionality prior to the onset of seizure-like activity. We suggest that techniques of nonlinear dynamical analysis are a useful reverse-engineering tool for studying the in vitro brain slice. We further conclude that neuronal circuits capable of displaying chaotic activity could exist at the level of the in vitro brain slice.

Monoamine metabolites, iron induced seizures, and the anticonvulsant effect of tannins

Intracortical injections of iron ions have been shown to induce recurrent seizures and epileptic discharges in the EEG. (-)-Epigallocatechin (EGC) and (-)-epigallocatechin-3-O-gallate (EGCG), isolated from green tea leaves, have been reported to prevent or diminish the occurrence of epileptic discharges induced by iron ions, and to inhibit catechol-O-methyltransferase. Iron ions significantly increased DOPAC and HVA levels in the intrastriatal perfusate 140 and 180 minutes, respectively, after injection. EGC and EGCG inhibited the increases induced by iron ions. Furthermore, EGCG decreased the HVA level in the perfusate 200 minutes after injection whether or not iron ions were injected. Iron ions had no effect on the 5-HIAA level, and EGC and EGCG raised it. These results suggest that formation of an epileptic focus induced by iron ions might be accompanied by activation of dopaminergic neurons, and that EGC and EGCG inhibit that hyperactivity.

Morphological investigation of iron-induced epileptic rats: with special reference to c-fos immunohistochemistry and iron staining

We investigated the iron-induced epileptic rats with special reference to c-fos immunohistochemistry and iron histochemistry in order to elucidate the pathogenesis of post-traumatic epilepsy. The c-fos-immunopositive neurons were observed in a hippocampal formation, especially in the dentate gyrus and CA1 and CA2, in the vicinity of the iron injected cerebral cortex and amygdala only at 3 hours after the iron administration. Three days later after administration, several heavily positively iron staining cells and nerve fibers were observed around the injection site. In the cases of 3 weeks after administration, the large cavity and gliosis were characteristically observed.

Iron-induced lipid peroxidation and brain injury responses

Head trauma with cerebral contusion causes extravasation of red blood cells, followed by hemolysis and deposition of iron-containing blood products within the neuropil. Liberation of heme compounds is associated with deposition of hemosiderin, and with gliosis, neuronal loss and occasionally the development of seizures. In this experiment we injected components of red blood cell contents into rat amygdala, and then measured the rate of appearance of products of lipid peroxidation. Injection of microliter volumes of hemin and hemoglobin, with hematoprotoporphyrin and rodent plasma injection and contralateral uninjected tissue as controls, showed that the presence of the iron moiety within the protoporphyrin ring was required to initiate and propagate peroxidation. Free radical reactions initiated by iron or heme deposited within the neuropil may be a fundamental reaction associated with brain injury responses, and possibly with posttraumatic epileptogenesis.

Spontaneous recurrent seizures in rats: an experimental model of partial epilepsy

Seizures induced by pilocarpine (PILO) have proven to be a useful procedure for investigating the basic mechanisms essential for generation, spread and motor expression of seizures in rodents. Here we report the long-term effects of PILO in rats. Following PILO (380 mg/kg, IP), 3 distinct phases were observed: 1) an acute period which lasted 1-2 days which corresponds to the pattern of repetitive seizures and status epilepticus; 2) a silent period (4-44 days) characterized by a progressive return to normal EEG and behavior; and 3) a period of recurrent seizures which started 5-45 days after PILO and lasted up to 120 days. These seizures lasted up to 50-60 sec, recurred 2-3 times per week and were more frequent during the light period of the light-dark cycle. These serial events offer a new method to induce spontaneous recurrent seizures in rats.

Effects of high-dose methylprednisolone on Na(+)-K+ ATPase and lipid peroxidation after experimental subarachnoid hemorrhage

The production of oxygen-free radicals and their subsequent peroxidative action on membrane unsaturated fatty acids could be enhanced after subarachnoid hemorrhage. High-dose methylprednisolone (30 mg/Kg i.v.) treatment can antagonize acute SAH-induced brain hypoperfusion and protect the ultrastructural integrity of endothelial cell membranes. Experimental subarachnoid hemorrhage (SAH) was induced in anesthesized rats by slow injection of 0.3 ml of autologous arterial blood into cisterna magna. Tissue lipid peroxidation, quantified as thiobarbituric acid reactive material (TBAR) and Na(+)-K+ ATPase activity were assayed in three different rat brain areas (cerebral cortex, hippocampus and brain stem) of controls (without any surgical manipulation), sham-operated (0.3 ml. of mock CSF into cisterna magna) and after SAH induction, at 1 h, 6 h and 48 h. Na(+)-K+ ATPase activity decreased in the cerebral cortex at 1 h and 6 h and in brain stem at 1 h after SAH, while the same enzymatic activity was unchanged in the hippocampus. High-dose methyl-prednisolone treatment (started immediately after SAH induction) enhanced the Na(+)-K+ ATPase activity until control levels. There was no significant difference in lipid peroxide content between sham-operated and hemorrhagic animals; however, the injection itself induces a transient increase of TBAR (1 h after injection) and methylprednisolone treatment decreases the products of lipid peroxidation in all brain areas.

Post-traumatic epilepsy: cellular mechanisms and implications for treatment

Epilepsy complicates severe head trauma. Development of persistent seizures appears to correlate with the extent of trauma. Although early reports suggested that prophylactic administration of antiepileptic drugs would prevent epileptogenesis, controlled studies have failed to corroborate this assumption. Head trauma initiates a sequence of responses that includes altered blood flow and vasoregulation, disruption of the blood-brain barrier, increases in intracranial pressure, focal or diffuse ischemia, hemorrhage, inflammation, necrosis, and disruption of fiber tracts. The presence of an intracranial hematoma has a robust association with the development of post-traumatic epilepsy. Extravasation of blood is followed by hemolysis and deposition of heme-containing compounds into the neuropil, initiating a sequence of univalent redox reactions and generating various free radical species, including superoxides, hydroxyl radicals, peroxides, and perferryl ions. Free radicals initiate peroxidation reactions by hydrogen abstraction from methylene groups adjacent to double bonds of fatty acids and lipids within cellular membranes. Intrinsic enzymatic mechanisms for control of free radical reactions include activation of catalase, peroxidase, and superoxide dismutase. Steroids, proteins, and tocopherol also terminate peroxidative reactions. Tocopherol and selenium are effective in preventing tissue injury initiated by ferrous chloride and heme compounds. Treatment strategies for prevention or prophylaxis of post-traumatic epilepsy must await absolute knowledge of mechanisms. Antioxidants and chelators may be useful, given the speculation that peroxidative reactions may be an important component of brain injury responses. However, potential treatment strategies involving gamma-aminobutyric acid (GABA) agonists, NMDA receptor antagonists, and barbiturates need further scientific assessment.

Biochemical pathogenesis of post-traumatic epilepsy

Head trauma is often followed by epilepsy and may be related to the breakdown of red blood cells and hemoglobin within the CNS. Injection of hemoglobin or iron salts into the rat cortex is known to induce a chronic epileptic focus. We observed the formation of superoxide anion (O2) and hydroxyl radical (.OH) after ferric chloride injection into the rat cerebral cortex and suggest that these radicals, especially .OH, may be responsible for the initiation of lipid peroxidation in neuronal membranes and for the accelerated production of guanidine compounds in the brain, which may in turn lead to epileptogenicity. Then, we found that treatment with epigallocatechin (EGC) or a phosphate diester of vitamins E and C (EPC), which are potent .OH scavengers, significantly inhibited the formation of malondialdehyde and epileptic discharges in the iron-induced epileptic focus.

Electrocorticographic characterization of chronic iron-induced epilepsy in rats

Electrocorticograms were recorded from rats which were unilaterally injected with ferrous chloride solution into the sensorimotor cortex to induce chronic epileptic activity. All of the iron-injected rats showed isolated spikes near the injection site and in the contralateral cortex immediately after the injection. The injection produced 3 kinds of responses in the rats according to the frequency of the isolated spikes. Spike and wave complexes appeared bilaterally approximately 30 days or more after the injection in the rats in which the frequency of the isolated spikes was dominant on the side ipsilateral to the injection site or nearly equal on the two sides. These results suggest that there are at least 2 stages in the development of chronic iron-induced epilepsy.

Lipid peroxidation and glutathione peroxidase, glutathione reductase, superoxide dismutase, catalase, and glucose-6-phosphate dehydrogenase activities in FeCl3-induced epileptogenic foci in the rat brain

This study investigated the relationship between lipid peroxidation, subsequent activation of antioxidative enzymes, and development of iron-induced epilepsy in the rat. Epileptic foci were produced in rat cerebral cortex by intracortical injection of ferric chloride (FeCl3). The epileptic foci were identified by electrocorticography (ECoG). Epileptiform ECoG activity was shown to occur in the contralateral homotopic cerebral cortex as well. We measured levels of lipid peroxides and changes in the activities of the enzymes: superoxide dismutase (SOD), glutathione peroxidase (GP), glutathione reductase (GR), catalase (CA), and glucose-6-phosphate dehydrogenase (G6P) in the epileptogenic focus (both ipsilateral and contralateral) at days 3, 8, 15, and 23 after FeCl3 injection. Biochemical estimations were made in subcellular fractions, and changes in the ipsilateral site were compared with those in the contralateral site. The results of this study showed that large increases in lipid peroxidation were associated with development and buildup of the ECoG epileptiform discharges. Lipid peroxides increased in the ipsilateral focus by approximately 100% as compared with control. In the contralateral site, however, the increase in lipid peroxides was marginal only. The increase in lipid peroxidation was concomitant with development of the high level of epileptiform activity. The time course of changes in lipid peroxidation paralleled the time course of development and persistence of the epileptiform activity. Regarding changes in the enzyme activities accompanying development of iron epilepsy, the data showed that although SOD and G6P increased by approximately 60% and GR increased by approximately 40%, the increases in the enzyme GP and CA were much lower, less than 20%. Thus, comparatively less increase in CA and GP activities produces a deficiency of these two enzymes in the iron (ipsilateral) focus. Among the various biochemical disturbances that have been identified as involved in epileptogenesis, peroxidative injury resulting from lipid peroxidation in neural plasma membrane may be causally related to development of paroxysmal epileptiform activity in the iron focus. Since GP is an enzyme of major importance in detoxification of lipid peroxides in the brain, based on the results presented in this article, it appears reasonable to suggest that GP deficiency causes lipid peroxidation to increase tremendously during iron epileptogenesis.

Petit mal epilepsy and parkinsonian tremor: hypothesis of a common pacemaker

Rhythmic oscillation in neuronal systems may serve physiological purposes or may interfere with normal functions of the brain. In disorders of petit mal epilepsy and parkinsonian tremor, centrally and peripherally observable rhythmic patterns are due to network oscillations of thalamocortical cells. This article reviews the afferent mechanisms that might be critically involved in controlling the ionic conductances of thalamic neurons in the behaving organism. We propose that during active behavior the subcortical aminergic and cholinergic inputs to the thalamus act as anti-burst and anti-oscillation mechanisms. We suggest further that the thalamopetal GABAergic inputs (pars reticulata of substantia nigra, entopeduncular nucleus, pallidum) are burst- and oscillation-promoting systems, whose output is controlled by the striatum. Experimental or disease-related decrease of the striatal dopamine levels is hypothesized to increase the efficacy of the GABAergic burst-promoting systems resulting in rhythmic network oscillation of thalamocortical neurons during rest. The recognition of the overlapping neuronal mechanisms in petit mal epilepsy and parkinsonian tremor, and the multistage control of thalamic oscillation suggests that drugs effectively used in petit mal attacks may be effective in levodopa-refractory parkinsonian tremor, and conversely, epileptic patients may benefit from drugs acting on the extrapyramidal system.

The role of iron-induced hippocampal peroxidation in acute epileptogenesis

Intracortical injection of iron salts causes lipid peroxidation, focal edema, necrosis, gliosis, and the development of behavioral and electrographic seizures. Tocopherol pretreatment prevents the histopathologic perturbations associated with iron injection, and appears to accelerate the resolution of focal accumulation of peroxidation products. In this experiment, rats were pretreated with 500 mg/kg DL-alpha-tocopherol acetate prior to the injection of 3 microliter of 100 mM FeCl2 into the dorsal hippocampus, or induction of convulsive seizures by s.c. injection of 0.8 mg/100 g bicucullin. Tocopherol pretreatment prevented the occurrence of convulsive seizures in a significant number of iron-salts injected animals. Lipid peroxidation measured in the dissected hippocampus was significantly increased in untreated rats developing iron-induced seizures and in rats treated with tocopherol, but developing convulsive seizures. Tocopherol failed to prevent bicucullin-induced seizures. Further, convulsive seizures induced by bicucullin failed to alter hippocampal fluorescence levels. Hence, we concluded that the epileptogenic effects of hippocampal injection of iron salts appear to be related to the induction of peroxidation of neural lipids within the injection site.

Method of lesioning brainstem determines seizure probability

We examined 3 different methods of brainstem lesioning to assess their propensities to evoke seizures in the early postoperative period. Lesioning by electrolysis or microinjection of the neurotoxin, N-methyl-D,L-aspartate, caused seizures, but lesioning by thermocoagulation (radiofrequency current) did not. In paradigms in which postoperative lesion-induced seizures could confound interpretation of experimental results, the thermocoagulative method offers an important advantage.

Reduced plasma haptoglobin and urinary taurine in familial seizures identified through the multisib strategy

The multisib (MS) sampling strategy was used for detecting possible genetic influences on a complex and heterogeneous disorder. The MS strategy increases the likelihood of selecting pedigrees for single genetic factors and allows the efficient analysis of data. The collection of complete pedigrees will procure additional data, but at a large marginal expense. The MS ascertainment procedure was applied to seizure disorders by examination of taurine excretion levels and by conducting two-dimensional gel electrophoresis of plasma proteins. Reduced taurine excretion (proposed to be genetically controlled) was found to associate with seizures, particularly in those individuals with a generalized spike and wave (GSW) EEg, or in families with a GSW-seizure history. Examination of two-dimensional gels showed hypohaptoglobinemia in several seizure patients [Panter et al, 1984]. The frequency of hypohaptoglobinemia is greatly increased in familial seizure cases, and may also be genetically controlled. Thus the MS strategy has proven successful in identifying kindreds in which specific physiological alterations may contribute toward the complex phenotype of seizures.

Epileptic seizures due to thrombotic and embolic cerebrovascular disease in older patients

Thromboembolic vascular disease is a frequent precipitant of seizures, and is the most common etiology in older patients. The occurrence of seizures shortly after a stroke, however, does not necessarily indicate that the patient will continue to have seizures following initial recovery. This is true even when patients present in epileptic status. This may be because early and late seizures are produced by different pathophysiologic mechanisms.

Seizures induced by intraventricular microinjection of ionized cobalt in the rat--a new experimental model of epilepsy

A new animal model for epilepsy was successfully produced by microinjection of cobaltous chloride into the lateral cerebral ventricle of the rat. The median convulsive dose (CD50) and the median lethal dose (LD50) of CoCl2 was 0.45 microM/10 microliters (0.27-0.77 microM/10 microliters) and 1.07 microM/10 microliters (0.73-1.57 microM/10 microliters), respectively. The behavioral changes, electrocorticogram (ECoG), and the action of 5 classical anticonvulsants were studied using this new model. Seizures induced by cobaltous chloride are clinically similar to those produced by systemic administration of kainic acid and amygdala kindling. These are characterized by staring spells, wet dog shakes, mild convulsive movements, and stereotyped convulsions. ECoG findings demonstrated a unique epileptic burst during the wet dog shakes. Generalized epileptiform discharges were seen during typical seizures. The burst of spikes first occurred in the opposite temporal and frontal regions; and then became generalized. Among the 5 anticonvulsants studied, phenobarbital (30 mg/kg) and nitrazepam (3 mg/kg) completely antagonized the seizures; carbamazepine showed a moderate effect; and phenytoin as well as sodium valproate showed little effect. It is postulated that the seizures induced by cobaltous chloride may originate in the limbic system; and that cobalt ions are responsible for the seizure-inducing action. The mechanism remains to be investigated.

Hypohaptoglobinemia associated with familial epilepsy

In select kindreds afflicted with familial idiopathic epilepsy, most individuals suffering seizures also have low levels of the plasma hemoglobin-binding protein, haptoglobin. This hypohaptoglobinemia may be causally associated with a tendency to develop epilepsy. Our experimental results indicate that artificially-induced hypohaptoglobinemia in mice causes retarded clearance of free hemoglobin from the central nervous system, and that such free hemoglobin may engender the peroxidation of brain lipids. We hypothesize that hypohaptoglobinemia, either inherited, or acquired via traumatic processes, may prevent efficient clearance of interstitial hemoglobin from the central nervous system, thereby predisposing these people to encephalic inflammation and the appearance of seizure disorders.

Epileptogenic effects of electrolytic lesions in the hippocampus: role of iron deposition

Small, anodal electrolytic lesions in the dorsal hippocampus were produced in rats, and continuous electrographic records were made from contralateral hippocampal electrodes for as long as 48 h following the lesion. Intense spontaneous epileptiform activity was observed, which developed from isolated spiking and spindling, to phasic spike trains, recurrent paroxysmal discharges and, in some cases, continuous ictal activity lasting to 7 h. Spontaneous clonic convulsions were observed in two cases. Epileptiform activity usually subsided after 12 h, but electrographic abnormalities such as spontaneous spiking and high-amplitude spindling persisted as long as 12 days. Such effects were reliably produced with iron-depositing lesions using stainless-steel electrodes, but not with platinum electrodes, suggesting that ionic deposition is critical for the lesion-induced seizure development. These results pose interpretive difficulties for the use of ion-depositing lesions in the study of limbic brain function.

Studies on sound-induced epilepsy in mice

The cerebral concentrations of pyridoxal-5'-phosphate and divalent transition metal ions (Cu2+ and Zn2+) are appreciably higher in the seizure-susceptible strain of mouse (DBA/2J) than those in normal strains (CBA/Ca and Parkes ). By injecting metal ions intracranially and pyridoxal-5'-phosphate intraperitoneally, we could render the normal mouse prone to sound-induced epilepsy. The behaviour of the treated seizure-susceptible strain of mouse. The levels of glutamate and aspartate in its inferior colliculus were elevated and the concentration of gamma-aminobutyrate was lowered. Glutaminase inhibitors, 6-diazo-5-oxo-L-norleucine (DON) and 0-diazo-acetyl-L-serine (azaserine), and a transaminase inhibitor, 4-amino-3- isoxazolidone (L-cycloserine), when injected intraperitoneally, protected the seizure-susceptible mouse from undergoing convulsions, whereas pyridoxal-5'-phosphate and methionine sulphoximine, a glutamine synthetase inhibitor, exacerbated its epileptic condition. We propose a possible sequence of biochemical events associated with susceptibility to audiogenic seizures.

The effect of tocopherol and dimethyl sulfoxide on focal edema and lipid peroxidation induced by isocortical injection of ferrous chloride

Addition of iron salts to suspensions of subcellular organelles or polyunsaturated fatty acids results in the formation of oxidative free radicals with subsequent initiation of lipid peroxidation. Pretreatment of rats with anti-oxidants prevents peroxidation following isocortical ferrous chloride injection, and increases the rate of resolution of iron-induced focal edema. In this experiment, treatment of rats at the time of injection of 5 microliters of 100 mM FeCl2 with tocopherol and DMSO caused decreased formation of brain peroxidation at the injection site, as measured by formation of MDA. Tocopherol failed to change the quantity of tissue fluid accumulation. However, DMSO alone, or combined with tocopherol, hastened the resolution of brain edema. Tocopherol may terminate peroxidation reactions by donation of a phenolic hydrogen, forming a quinone of tocopherol. DMSO has many pharmacologic effects; however, inhibition of initiation reactions by scavenging hydroxyl radicals, and direct and indirect effects on focal edema accumulation may account for our observations.

In vivo lipid peroxidation in rat brain following intracortical Fe2+ injection

Cerebral contusion, cortical laceration, intracerebral hematoma formation, and hemorrhagic cortical infarction cause extravasation of red blood cells, followed by hemolysis, decompartmentalization of iron, formation and deposition of hemosiderin, and an increased incidence of epilepsy. In this experiment, 10 microliter of an aqueous solution containing 100 mmol/L FeCl2, 100 mmol/L CoCl2, or 0.9% (wt/vol) NaCl were injected at a depth of 1.8 mm into rat isocortex. The rate of formation of fluorescent compounds was measured in chloroform-methanol extracts of isocortical homogenates. Significant increases in the quantity of fluorescent products of lipid peroxidation were found 120 min after the injection of 100 mmol/L FeCl2. Cobaltous chloride and saline injection had no effect on the levels of fluorescent products found in the cortical homogenates. Although the intracortical deposition of aqueous solutions containing CoCl2 or FeCl2 in rodent cortex causes acute epileptiform discharges, the epileptogenic effect of CoCl2 is transient, while the injection of iron salts causes persistent seizures. Since CoCl2 injection failed to cause formation of lipid peroxidation products while the isocortical injection of iron caused significant increase in fluorescence within the injected hemisphere, we suggest that the occurrence of iron-induced lipid peroxidation may be of importance in initiation of recurrent seizures in the rat.

Effect of phenytoin and corticosteroids on seizures and lipid peroxidation in experimental posttraumatic epilepsy

Head trauma, intracerebral hematoma formation, and hemorrhagic cerebral infarction cause extravasation of the intravascular contents, red blood cell (RBC) hemolysis, hemosiderin deposition within the neuropil, and an increased incidence of epilepsy. Reports conflict regarding the efficacy of the administration of prophylactic anticonvulsant drugs to head-injured patients to prevent the development of posttraumatic epilepsy. In this study, rats received a 10-microliter injection of 100 mM FeCl2 at a depth of 1.8 mm into the isocortex, or an equal volume of saline. Rats were then treated with 30 mg/kg methylprednisolone (MPS), 90 mg/kg MPS, 100 mg/kg phenytoin, or with an equal volume of propylene glycol. Behavioral or electroencephalographic (EEG) seizures occurred in all control-treated iron-injected rats within 93 +/- 6 minutes of injection. Brain injury responses as measured by the occurrence of fluorescent product formation from iron-induced lipid peroxidation showed 6.6 +/- 0.8 units/gm in the saline-injected animals, and 16.7 +/- 2.5 units/gm in the control-treated iron-injected rats. Of the 90-mg/kg MPS-treated rats, 8% had seizures; fluorescence in those animals was 5.7 +/- 0.5 units/gm. Phenytoin treatment prevented the occurrence of convulsive and EEG seizures; however, lipid peroxidation was unaffected (16.5 +/- 4.1 units/gm). If posttraumatic epilepsy develops because of RBC extravasation, hemolysis, parenchymal deposition of heme compounds, and initiation of lipid peroxidation, then treatments designed to prevent peroxidation may be more effective for epilepsy prophylaxis than administration of anticonvulsant drugs that mask convulsive seizures while biochemical brain injury continues.

Effects of antiperoxidants on FeCl2-induced lipid peroxidation and focal edema in rat brain

Head trauma with contusion or cortical laceration and hemorrhage causes focal edema with encephalomalacia and gliosis. Because cerebral hemorrhage ultimately results in deposition of heme compounds and iron into the neuropil, we injected an aqueous solution of iron salts to simulate the decompartmentalization of iron after trauma. We pretreated animals with saline or with 600 mg/kg alpha-tocopherol plus 5 ppm selenium added to the drinking water. Formation of lipid peroxidation products was significantly inhibited within the iron injection site in the antiperoxidant-pretreated rats at 30, 60, and 120 min after injection of iron into the isocortex. The antiperoxidants failed to prevent formation of focal brain edema at the injection site between 1 and 8 h after injection; however, significantly less edema was present in the alpha-tocopherol + selenium-pretreated animals 24 and 48 h after injection. The efficacy of antiperoxidants in preventing lipid peroxidation, and enhancing the resolution of ferrous-induced focal brain edema suggest that tocopherol + selenium administration caused free radical quenching and termination of lipid peroxidation, and increased membrane stabilization, an effect similar to the action of glucocorticoids.

Formation of superoxide radicals after FeCl3 injection into rat isocortex

Subpial injection of aqueous solutions of iron salts into rat isocortex induces recurrent epileptiform discharges with focal brain edema, cavitary necrosis and gliosis. Since aqueous iron or heme compounds cause peroxidation of lipids, we studied the sequence of changes in the formation of free radicals, and superoxide radicals, in rat isocortex injected with 5 microliter of 100 mM FeCl3. Electron spin resonance measurements of whole rat brain showed a transient increase in heme-bound Fe3+. Superoxide radicals were increased in a cylinder of tissue obtained at the injection site 5 min and 15 min after completion of the injection. This study shows that iron salts injected into rat isocortex cause transient formation of free radicals. We suggest that decompartmentalization of iron compounds may be of importance in trauma-related brain injury responses.

Experimentally induced susceptibility to audiogenic seizure

By injecting metal ions and pyridoxal-5'-phosphate, we made the normal mouse prone to sound-induced epilepsy. We showed that the levels of glutamate and aspartate in its inferior colliculus were elevated and the concentration of gamma-aminobutyrate was lowered. The time course of audiogenic susceptibility after the treatment was closely mirrored by changes in the concentrations of glutamate, aspartate, and gamma-aminobutyrate in the inferior colliculus.

Formation of malonaldehyde and focal brain edema induced by subpial injection of FeCl2 into rat isocortex

Subpial injection of iron salts or iron-containing blood products into rat isocortex induces recurrent epileptiform discharges coupled with cavitary necrosis and gliosis. Since aqueous iron or heme compounds cause formation of superoxide radicals and peroxidation of membrane lipids, we studied the rate of formation of malonaldehyde (MDA) after subpial injection of 5 microliters of various concentrations of FeCl2 and CoCl2. Injection of CoCl2 failed to alter isocortical MDA levels. However, significant formation of MDA occurred after injection of 25, 50 and 100 mM FeCl2 into rat isocortex. Formation of peak MDA levels of 13.4 +/- 1.0 nmol.mg protein-1 occurred at 15 in to 1 h after 100 mM FeCl2 injection; levels returned to equal control by 12 h. Tissue fluid accumulation occurred by 2 h after FeCl2 injection and persisted for 38 h. Histopathologic assessment using Nissl staining of tissue from the injection site showed loss of cellular staining, coagulation necrosis, and accumulation of macrophages and glial cells. Although these experiments showed the initiation of lipid peroxidation and formation of focal isocortical edema by injection of aqueous solutions of iron salts, we speculate that decompartmentalization of iron red blood cells after trauma, cerebral hemorrhage or infarction may be important in the propagation of tissue damage from such injuries.