Electroconvulsive shock in rats: changes in superoxide dismutase and glutathione peroxidase activity

Oxidative Stress and Neurodegeneration in Animal Models of Seizures and Epilepsy

Free radicals are generated in the brain, as well as in other organs, and their production is proportional to the brain activity. Due to its low antioxidant capacity, the brain is particularly sensitive to free radical damage, which may affect lipids, nucleic acids, and proteins. The available evidence clearly points to a role for oxidative stress in neuronal death and pathophysiology of epileptogenesis and epilepsy. The present review is devoted to the generation of free radicals in some animal models of seizures and epilepsy and the consequences of oxidative stress, such as DNA or mitochondrial damage leading to neurodegeneration. Additionally, antioxidant properties of antiepileptic (antiseizure) drugs and a possible use of antioxidant drugs or compounds in patients with epilepsy are reviewed. In numerous seizure models, the brain concentration of free radicals was significantly elevated. Some antiepileptic drugs may inhibit these effects; for example, valproate reduced the increase in brain malondialdehyde (a marker of lipid peroxidation) concentration induced by electroconvulsions. In the pentylenetetrazol model, valproate prevented the reduced glutathione concentration and an increase in brain lipid peroxidation products. The scarce clinical data indicate that some antioxidants (melatonin, selenium, vitamin E) may be recommended as adjuvants for patients with drug-resistant epilepsy.

N-acetyl cysteine: A new look at its effect on PTZ-induced convulsions

INTRODUCTION/AIM

Epilepsy is widely investigated as a common neurological disease requiring pharmacologically effective agents. N-acetyl cysteine (NAC), has become a remarkable molecule with its role in both antioxidant and glutaminergic modulation. There are many points and processes waiting to be revealed regarding the role of NAC in epilepsy.

MATERIALS AND METHODS

Pentylenetetrazole (PTZ) was administered to induce seizures in a total number of 48 Sprague-Dawley rats. 35 mg/kg PTZ dose as a sub-convulsive dose was administered to 24 animals to monitor EEG changes, while 70 mg/kg PTZ dose which was a convulsive dose was administered to 24 animals to determine seizure-related behavioral changes with the Racine's scale. 30 min before the seizure-induced procedure, NAC was administered at doses of 300 and 600 mg/kg as pretreatment to investigate anti-seizure and anti-oxidative effects. The spike percentage, the stage of convulsion, and the onset time of the first myoclonic jerk were evaluated to determine the anti-seizure effect. Furthermore, its effect on oxidative stress was determined by measuring both malondialdehyde (MDA) level and superoxide dismutase (SOD) enzyme activity.

RESULTS

There was a dose-dependent reduction in the seizure stage and prolonged onset time of the first myoclonic jerk in rats with NAC pretreatment. EEG recordings resulted in a dose-dependent decrease in spike percentages. Moreover, the same dose-dependent changes were observed in oxidative stress biomarkers, both 300 mg/kg NAC and 600 mg/kg decreased MDA levels and ameliorated SOD activity.

CONCLUSION

We can report that 300 mg/kg and 600 mg/kg doses of NAC are promising with their reducing effect on convulsions and have a beneficial effect by preventing oxidative stress. In addition, NAC has been also determined that this effect is dose-dependent. Detailed and comparative studies are needed on the convulsion-reducing effect of NAC in epilepsy.

Effect of Hesperetin on the Antidepressant Activity of Electroconvulsive Therapy in an Enforced Reserpine Model of Depression in Male Rats

Background: Depression is a common and debilitating disorder of the brain. Many pharmacological therapies, including many plant components (such as flavonoids), are used to treat depression. Electroconvulsive therapy (ECT) is a useful method for depressed patients who do not respond to medication. However, this method has some side effects. Hence, investigators have tried to improve ECT’s positive points by diminishing its side effects. Objectives: We investigated the effect of hesperetin (a flavonoid component) on the antidepressant activity of ECT in an enforced reserpine model of depression in male rats. Methods: Eighty male rats (230 - 250 g) were randomly divided into control, ECT + reserpine (Res), Res + hesperetin (Hes; 10 or 20 mg/kg), Res + ECT, and Res + ECT + Hes (10 or 20 mg/kg) groups. The effects of hesperetin were evaluated by the forced swimming test (FST), sucrose preference test (SPT), open field test (OFT), elevated plus maze test (EPMT), as well as by measurement of the brain-derived neurotrophic factor (BDNF) and oxidative stress biomarkers [ie, malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione (GSH)] in the prefrontal cortex area. Results: The outcomes of the behavioral experiments showed that Hes + ECT treatment could raise the percentage of open arm entrance in EPMT, anhedonia in SPT, and decrease immobilization time in FST compared to the groups treated with ECT (P < 0.05) or hesperetin alone. Our biochemical research also illustrated a significant reduction in MDA in the groups treated with ECT + Hes (10 or 20 mg/kg; P < 0.01 and P < 0.001) and ECT or hesperetin, as well as a significant increase in GSH, SOD, and BDNF in the ECT + Hes (20 mg/kg) animal group (P < 0.001). Conclusions: In depressed rats, the ECT linked to the application of hesperetin could significantly elevate BDNF, GSH, and SOD reduction in depressed male rats.

Molecular Biomarkers of Electroconvulsive Therapy Effects and Clinical Response: Understanding the Present to Shape the Future

Electroconvulsive therapy (ECT) represents an effective intervention for treatment-resistant depression (TRD). One priority of this research field is the clarification of ECT response mechanisms and the identification of biomarkers predicting its outcomes. We propose an overview of the molecular studies on ECT, concerning its course and outcome prediction, including also animal studies on electroconvulsive seizures (ECS), an experimental analogue of ECT. Most of these investigations underlie biological systems related to major depressive disorder (MDD), such as the neurotrophic and inflammatory/immune ones, indicating effects of ECT on these processes. Studies about neurotrophins, like the brain-derived neurotrophic factor (BDNF) and the vascular endothelial growth factor (VEGF), have shown evidence concerning ECT neurotrophic effects. The inflammatory/immune system has also been studied, suggesting an acute stress reaction following an ECT session. However, at the end of the treatment, ECT produces a reduction in inflammatory-associated biomarkers such as cortisol, TNF-alpha and interleukin 6. Other biological systems, including the monoaminergic and the endocrine, have been sparsely investigated. Despite some promising results, limitations exist. Most of the studies are concentrated on one or few markers and many studies are relatively old, with small sample sizes and methodological biases. Expression studies on gene transcripts and microRNAs are rare and genetic studies are sparse. To date, no conclusive evidence regarding ECT molecular markers has been reached; however, the future may be just around the corner.

Hesperetin ameliorates electroconvulsive therapy-induced memory impairment through regulation of hippocampal BDNF and oxidative stress in a rat model of depression

Depression is one of the most common mental health disorders and it is generally characterized by negative mood. Although electroconvulsive therapy (ECT) is an effective treatment for depression, however, it can cause cognitive deficit. Hesperetin, an active ingredient in citrus peels, has antioxidant and neuroprotective properties. In this study, we evaluated the effect of hesperetin on memory impairment induced by ECT in a reserpine-induced depression model in male rat. For this purpose, 105 male rats weighing 230-250 g were randomly divided into control and reserpine-treated groups. The reserpine-treated animals were subdivided into: Reserpine, Hesperetin (10 and 20 mg/kg), ECT and ECT+Hesperetin (10 and 20 mg/kg). After taking the drugs, the effect of hesperetin was evaluated through behavioral NORT, Y Maze, FST, SPT and also via assessment of hippocampal brain-derived neurotrophic factor (BDNF) and oxidative stress biomarkers i.e., MDA, SOD and GSH. As a result, our biochemical studies showed a significant decrease of MDA in groups treated with ECT+Hesperetin as compared to ECT and hesperetin groups (P < 0.001) and a marked increase in SOD, GSH and BDNF in ECT+Hesperetin 20 group as compared to other groups (p < 0.05). Also, the results of behavioral tests revealed that treatment with hesperetin can increase the novel object recognition index and alternation behaviors in Y maze test as compared to the groups treated with hesperetin or ECT (p < 0.05). These results suggest that co-administration of hesperetin with ECT is effective for improvement of cognitive function and can alleviate ECT-induced memory impairment in reserpine-treated rats.

Effects of electroconvulsive shock on neuro-immune responses: Does neuro-damage occur?

Electroconvulsive therapy (ECT) is one of the most effective treatments for treatment-resistant depression. However, this treatment may produce memory impairment. The mechanisms of the cognitive adverse effects are not known. Neuroimmune response is related to the cognitive deficits. By reviewing the available animal literature, we examined the glia activation, inflammatory cytokines, neuron oxidative stress responses, and neural morphological changes following electroconvulsive shock (ECS) treatment. The studies showed that ECS activates microglia, upregulates neuro-inflammatory cytokines, and increases oxidative stress responses. But these effects are rapid and may be transient. They normalize as ECS treatment continues, suggesting endogenous neuroprotection may be mobilized. The transient changes are well in line with the clinical observations that ECT usually does not cause significant long-lasting retrograde amnesia. The longitudinal studies will be particularly important to explore the dynamic changes of neuroplasticity following ECT (Jonckheere et al., 2018). Investigating the neuroplasticity changes in animals that suffered chronic stress may also be crucial to giving support to the translation of preclinical research.

[Oxidative stress in epilepsy]

This article contains an analysis of clinical and experimental studies in which oxidative stress is considered as a possible mechanism in the pathogenesis of epilepsy. Oxidative stress occurs as a result of brain damage after epileptic seizures and may later cause epileptogenesis. Patients with epilepsy showed a high level of lipid peroxidation markers, while the activity of antioxidant defense system was low. The level of oxidative stress was shown to be significantly higher in epileptics with associated mental disorders and in patients with refractory epilepsy. Further study of oxidative stress in epilepsy may play the key role in the treatment of this disease.

Comparative studies on the effects of clinically used anticonvulsants on the oxidative stress biomarkers in pentylenetetrazole-induced kindling model of epileptogenesis in mice

BACKGROUND

Oxidative stress plays a key role in the pathogenesis of epilepsy and contributes in underlying epileptogenesis process. Anticonvulsant drugs targeting the oxidative stress domain of epileptogenesis may provide better control of seizure. The present study was carried out to investigate the effect of clinically used anti-epileptic drugs (AEDs) on the course of pentylenetetrazole (PTZ)-induced kindling and oxidative stress markers in mice.

METHODS

Six mechanistically heterogeneous anticonvulsants: phenobarbital, phenytoin, levetiracetam, pregabalin, topiramate, and felbamate were selected and their redox profiles were determined. Diazepam was used as a drug control for comparison. Kindling was induced by repeated injections of a sub-convulsive dose of PTZ (50 mg/kg, s.c.) on alternate days until seizure score 5 was evoked in the control kindled group. Anticonvulsants were administered daily. Following PTZ kindling, oxidative stress biomarkers were assessed in homogenized whole brain samples and estimated for the levels of nitric oxide, peroxide, malondialdehyde, protein carbonyl, reduced glutathione, and activities of nitric oxide synthase and superoxide dismutase.

RESULTS

Biochemical analysis revealed a significant increase in the levels of reactive oxygen species with a parallel decrease in endogenous anti-oxidants in PTZ-kindled control animals. Daily treatment with levetiracetam and felbamate significantly decreased the PTZ-induced seizure score as well as the levels of nitric oxide (p<0.001), nitric oxide synthase activity (p<0.05), peroxide levels (p<0.05), and malondialdehyde (p<0.05). Levetiracetam and felbamate significantly decreased lipid and protein peroxidation whereas topiramate was found to reduce lipid peroxidation only.

CONCLUSIONS

An AED that produces anticonvulsant effect by the diversified mechanism of action such as levetiracetam, felbamate, and topiramate exhibited superior anti-oxidative stress activity in addition to their anticonvulsant activity.

Evaluation of Oxidative Status in Patients Treated with Electroconvulsive Therapy

Objective

Electroconvulsive therapy (ECT) is used in the treatment of many psychiatric diseases and this therapy may be effective on antioxidant defence system. In this study, we aimed to evaluate the effects of ECT on oxidative stress.

Methods

Fourteen major depression, 11 schizophrenia and 8 bipolar affective disorder patients diagnosed and received ECT treatment, and 37 healthy volunteers enrolled in the study. ECT was applied to all patients. Before ECT, after the first and last ECTs, serum samples were obtained. Serum total antioxidant status (TAS), total oxidant status (TOS), and calculated oxidative stress index (OSI) were measured in patients before and after ECTs.

Results

TOS values before ECT were higher in major depression (p=0.005) and schizophrenia (p=0.001) groups compared to the control group. TAS values were lower in major depression (p=0.0001), schizophrenia (p=0.004), bipolar affective disorder (p=0.004) groups compared to the controls. Also OSI values were higher in major depression (p=0.0001), schizophrenia (p=0.001), bipolar affective disorder (p=0.009) groups compared to healthy group. After the last ECT, TOS values were significantly lower compared to TOS values before ECT in major depression (p=0.004) and schizophrenia patients (p=0.004). TAS values after the first ECT were higher compared to values before ECT in major depression patients (p=0.004). After last ECT, OSI values were significantly lower compared to before ECT in schizophrenia patients (p=0.006).

Conclusion

As a result, it can be said that ECT did not increase oxidative stress. However, further studies with more patients are needed.

An isolated epileptic seizure elicits learning impairment which could be prevented by melatonin

We tested the relation between a single short tonic-clonic seizure elicited by flurothyl vapors and changes of learning in Morris water maze (MWM) in Wistar rats. Oxidative stress usually accompanies seizures. Large melatonin doses were applied immediately before and after seizures to test consequences on learning impairment. One hour of hypobaric hypoxia (8000 m) three days prior to the seizure served as an activator of intrinsic antioxidant systems. Learning in MWM (7 days) started 24 h after seizures. Following seizures, latencies in MWM were longer than in controls and were shortened by hypoxia and preventive melatonin application. Melatonin was also applied before hypoxia to influence free radical (FR) production and intrinsic antioxidant activation. Some behavioral characteristics were changed and preconditioning effect of hypoxia was reduced. Melatonin after seizure (150 s and 6 h) had negligible effect. Results allow us to hypothesize about the role of FR and the beneficial effect of melatonin on the behavioral consequences of seizures.

Analgesic, anticonvulsant and antioxidant activities of 3-[4-(3-trifluoromethyl-phenyl)-piperazin-1-yl]-dihydrofuran-2-one dihydrochloride in mice

Recently we have shown that 3-[4-(3-trifluoromethyl-phenyl)-piperazin-1-yl]-dihydrofuran-2-one dihydrochloride (LPP1) is an antinociceptive and local anesthetic agent in rodents. Below an extended study of the pharmacological activity of LPP1 is described. In vitro LPP1 has no affinity for GABA(A), opioidergic μ and serotonergic 5-HT(1A) receptors. The total antioxidant capacity of LPP1 (1-10mM) measured as ABTS radical cation-scavenging activity showed that LPP1 has dose-dependent antioxidant properties in vitro. Low plasma concentration of this compound detected by means of HPLC method 30min after its intraperitoneal administration suggests a rapid conversion to metabolite(s) which may be responsible for its analgesic and anticonvulsant activities in vivo. In vivo the compound's influence on the electroconvulsive threshold and its activity in the maximal electroshock seizure test (MES) were evaluated. The results demonstrated that LPP1 had an anticonvulsant activity in the MES model (ED(50)=112mg/kg) and at a dose of 50mg/kg was able to elevate the electroconvulsive threshold for 8mA as compared to the vehicle-treated mice. The analgesic activity of LPP1 was investigated in the acetic acid-induced writhing test in two groups of mice: animals with sensory C-fibers ablated, and mice with C-fibers unimpaired. It proved the potent activity of this compound in both groups (approximately 85% as compared to the vehicle-treated mice). The adverse effects of LPP1 were evaluated as acute toxicity (LD(50)=747.8mg/kg) and motor coordination impairments in the rotarod and chimney tests. The results from these tests show that LPP1 at doses higher than 100mg/kg is likely to impair the motor performance of experimental animals. Concluding, LPP1 is an analgesic and anticonvulsant compound which has antioxidant properties in vitro. Further studies are necessary to assess whether the antioxidant activity and the receptor profiling demonstrated in vitro can be confirmed for its metabolite(s) that are formed in vivo.

Oxidative stress parameters in different rat brain structures after electroconvulsive shock-induced seizures

Electroconvulsive therapy has been used in the treatment of psychiatric disorders since the 1930s, but little progress has been made in understanding the cellular mechanisms underlying its therapeutic and adverse effects. Electroconvulsive shock (ECS) in animals provides a common experimental model for studying the effects of electroconvulsive therapy in humans. In order to examine the changes of the brain oxidative stress parameters in several brain structures in the early time period after ECS-induced seizures, the levels of lipid peroxidation as well as superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities in the rat hippocampus, cerebellum, frontal cortex and the pons/medulla region were determined at different time points during the first 24 h after single ECS-induced seizures. In the hippocampus and cerebellum the levels of lipid peroxidation were unchanged, while the SOD and GSH-Px activities were significantly increased. Levels of lipid peroxidation and the activities of SOD and GSH-Px were not statistically changed in the pons/medulla region. Levels of lipid peroxidation in the frontal cortex were significantly higher in comparison to the control group at all time points examined while the SOD and GSH-Px activities were not statistically changed. In conclusion, the results of the present study indicate that single ECS causes the rat brain structure-specific alterations in the levels of lipid peroxidation as well as in the SOD and GSH-Px activities at different time points within the first 24 h after the seizures induction. Oxidative lipid damage was evident only in the frontal cortex, while the hippocampus, cerebellum and the pons/medulla region remained oxidatively unaffected in our experimental conditions.

Maximal electroshock induces changes in some markers of oxidative stress in mice

The oxidative/antioxidative status was investigated in maximal electroshock-induced seizures in mice, a well established model of generalized seizures in humans. Mice were given a single electroshock resulting in tonic convulsions. Total antioxidant capacity (TAC), lipid peroxidation intensity and glutathione peroxidase (GSH-Px) activity was measured spectrophotometrically in the brain, plasma and erythrocytes collected from mice sacrificed at different time points after stimulation. For comparison, sham-stimulated and subeffectively stimulated (no tonic seizures) mice were used. Tonic seizures caused an immediate increase in GSH-Px activity in the brain and during the following three hours the enzyme activity decreased below control values. Similar changes were seen after subconvulsive stimulations, however, a significant increase occurred only one hour after electroshock. A marked TAC reduction in the brain was observed three hours after subconvulsive stimulations. Nevertheless, no significant changes in TAC after tonic seizures were noted. TAC in plasma was significantly reduced three hours after both subconvulsive and convulsive stimulation. Marked reduction of lipid peroxidation intensity in the brain and plasma was recorded after both modes of stimulation. In conclusion, pronounced changes in oxidative/antioxidative status in mice following electroshock are caused by both convulsive and subconvulsive stimuli. Participation of oxidative stress in seizures and pathophysiology of epilepsy awaits further clarification.

Effects of febrile and afebrile seizures on oxidant state in children

No comparative studies have addressed the oxidant and antioxidant states of blood and cerebrospinal fluid. To reveal this differential state, the study was designed to identify the seizure type with the worse prognosis by determining erythrocyte arginase and erythrocyte catalase, plasma and cerebrospinal fluid malondialdehyde, and plasma and cerebrospinal fluid nitric oxide levels. Study groups were classified as febrile (group 1, n = 21), afebrile (group 2, n = 21), and control (group 3, n = 41, subdivided as 3a, febris positive, convulsion negative, and 3b, febris negative, convulsion negative). Levels of erythrocyte arginase, erythrocyte catalase, plasma malondialdehyde, cerebrospinal fluid malondialdehyde, plasma nitric oxide, and cerebrospinal fluid nitric oxide levels were determined for all groups. A difference was detected between the control and febrile seizure groups with respect to erythrocyte catalase and plasma and cerebrospinal fluid levels of nitric oxide (P < 0.05). Both febrile states and convulsions influence oxidative mechanism. Oxidative stress-generating potential differs for febrile and afebrile seizures. In afebrile seizures, greater levels of oxidative stress might affect prognosis adversely. This phenomenon can be interpreted in terms of fever as a protective factor against possible neurological damage during convulsive seizures.

Effects of lipopolysaccharide on blood-brain barrier permeability during pentylenetetrazole-induced epileptic seizures in rats

We investigated the effects of lipopolysachharide (LPS) on functional and structural properties of the blood-brain barrier (BBB) during pentylenetetrazole (PTZ)-induced epileptic seizures in rats. Arterial blood pressure was significantly elevated during epileptic seizures irrespective of LPS pretreatment. Plasma levels of interleukin (IL)-1, interleukin (IL)-6, nitric oxide (NO) and malondialdehyde (MDA) increased while catalase concentrations decreased in animals treated with LPS, PTZ and LPS plus PTZ. The significantly increased BBB permeability to Evans blue (EB) dye in the cerebral cortex, diencephalon and cerebellum regions of rats by PTZ-induced seizures was markedly reduced upon LPS pretreatment. Immunoreactivity for tight junction proteins, zonula occludens-1 and occludin, did not change in brain vessels of animals treated with PTZ and LPS plus PTZ. Glial fibrillary acidic protein immunoreactivity was increased in LPS, but not in PTZ and LPS plus PTZ. These results indicate that LPS pretreatment reduces the passage of EB dye bound to albumin into the brain, at least partly, by increasing plasma NO and IL-6 levels during PTZ-induced epileptic seizures. We suggest that LPS may provide protective effects on the BBB integrity during epileptic seizures through transcellular pathway, since the paracellular route remained unaffected by LPS and LPS plus PTZ.

Depletion of reduced glutathione precedes inactivation of mitochondrial enzymes following limbic status epilepticus in the rat hippocampus

The time course and critical determinants of mitochondrial dysfunction and oxidative stress following limbic status epilepticus (SE) were investigated in hippocampal sub-regions of an electrical stimulation model in rats, at time points 4-44h after status. Mitochondrial and cytosolic enzyme activities were measured spectrophotometrically, and reduced glutathione (GSH) concentrations by HPLC, and compared to results from sham controls. The earliest change in any sub-region was a fall in GSH, appearing as early as 4h in CA3 (-13%, p<0.05), and persisting at all time points. This was followed by a transient fall in complex I activity (CA3, 16h, -13%, p<0.05), and later changes in aconitase (CA1,-18% and CA3, -22% at 44h, p<0.05). The activity of the cytosolic enzyme glyceraldehyde-3-phosphate-dehydrogenase was unaffected at all time points. It is known that GSH levels are dependent both on redox status, and on the availability of the precursor cysteine, in turn dependent on the cysteine/glutamate antiporter, for which extracellular glutamate concentrations are rate limiting. Both mechanisms are likely to contribute indirectly to GSH depletion following seizures. That a relative deficiency in GSH precedes later changes in the activities of complex I and aconitase in vulnerable hippocampal sub-regions, occurring within a clinically relevant therapeutic time window, suggests that strategies to boost GSH levels and/or otherwise reduce oxidative stress following seizures, deserve further study, both in terms of preventing the biochemical consequences of SE and the neuronal dysfunction and clinical consequences.

Increased susceptibility of glutathione peroxidase-1 transgenic mice to kainic acid-related seizure activity and hippocampal neuronal cell death

Glutathione peroxidase (GSHPx) has been demonstrated in several in vivo studies to reduce both the risk and severity of oxidatively-induced tissue damage. The seizure-inducing neurotoxin kainic acid (KA) has been suggested to elicit its toxic effects in part via generation of oxidative stress. In this study, we report that expression of elevated levels of murine GSHPx-1 in transgenic mice surprisingly results in increased rather than decreased KA susceptibility including increased seizure activity and neuronal hippocampal damage. Isolated transgenic primary hippocampal culture neurons also display increased susceptibility to KA treatment compared with those from wildtype animals. This could be due to alterations in the redox state of the glutathione system resulting in elevated glutathione disulfide (GSSG) levels which, in turn, may directly activate NMDA receptors or enhanced response of the NMDA receptor.

No evidence for oxidative damage in the hippocampus after acute and chronic electroshock in rats

Although several advances has occurred over the past 20 years concerning the use of electroconvulsive therapy (ECT), little progress has been made in the mechanisms underlying its therapeutic or adverse effects. Thus, this work was performed in order to determine the level of oxidative damage and antioxidant enzyme activities early and late after acute and chronic electroconvulsive shock (ECS). We demonstrated a decrease in lipid peroxidation in the hippocampus immediately after and up to 30 days after a single or multiple electroconvulsive shock. This was also true for protein carbonyls in the acute protocol. We demonstrated an increase in catalase (CAT) and superoxide dismutase (SOD) activities at different time points after single and multiple electroconvulsive shock. Our findings, for the first time, demonstrated that after electroconvulsive shock, there is an increase in antioxidant enzyme activities and we cannot demonstrate oxidative damage in the hippocampus.

Effects of the hyperbaric oxygen treatment on the Na+,K+ -ATPase and superoxide dismutase activities in the optic nerves of global cerebral ischemia-exposed rats

The effects of hyperbaric oxygen (HBO) treatment on the Na+,K+ -ATPase and superoxide dismutase (SOD) activities were examined in the optic nerves of the rats exposed to global cerebral ischemia. Animals were exposed to global cerebral ischemia of 20-min duration and were either sacrificed or exposed to the first HBO treatment immediately, 0.5, 1, 2, 6, 24, 48, 72 or 168 h after ischemic procedure (for Na+,K+ -ATPase activities measurement) or 2, 24, 48 or 168 h after ischemia (for SOD activities measurement). HBO procedure was repeated for 7 consecutive days. It was found that global cerebral ischemia induced a statistically significant decrease in the Na+,K+ -ATPase activity of the optic nerves, starting from 0.5 to 168 h of reperfusion. Maximal enzymatic inhibition was registered 24 h after the ischemic damage. The decline in the Na+,K+ -ATPase activity was prevented in the animals exposed to HBO treatment within the first 6 h of reperfusion. The results of the presented experiments demonstrated also a statistically significant increase in the SOD activity after 24, 48 and 168 h of reperfusion in the optic nerves of non-HBO-treated ischemic animals as well as in the ischemic animals treated with HBO. Our results indicate that global cerebral ischemia induced a significant alterations in the Na+,K+ -ATPase and SOD activities in the optic nerves during different periods of reperfusion. HBO treatment, started within the first 6 h of reperfusion, prevented ischemia-induced changes in the Na+,K+ -ATPase activity, while the level of the SOD activity in the ischemic animals was not changed after HBO administration.

Hyperbaric oxygen treatment: the influence on the hippocampal superoxide dismutase and Na+,K+-ATPase activities in global cerebral ischemia-exposed rats

The influence of hyperbaric oxygen (HBO) treatment on the activities of superoxide dismutase (SOD) and Na(+),K(+)-ATPase was determined during different time periods of reperfusion in rats exposed to global cerebral ischemia. Ischemic animals were either sacrificed or exposed to the first HBO treatment 2, 24, 48 or 168 h after ischemic insult (for SOD activities measurement) or immediately, 0.5, 1, 2, 6, 24, 48, 72 or 168 h after ischemic procedure (for Na(+),K(+)-ATPase activities measurement). Hyperbaric oxygenation procedure was repeated for seven consecutive days. The results of presented experiments demonstrated the statistically significant increase in the hippocampal SOD activity 24 and 48 h after global cerebral ischemia followed by a decrease in the enzymatic activity 168 h after ischemic insult. In the ischemic rats treated with HBO the level of hippocampal SOD activity was significantly higher after 168 h of reperfusion in comparison to the ischemic, non HBO-treated animals. In addition, it was found that global cerebral ischemia induced a statistically significant decrease of the hippocampal Na(+),K(+)-ATPase activity starting from 1 to 168 h of reperfusion. Maximal enzymatic inhibition was obtained 24 h after the ischemic damage. Decline in Na(+),K(+)-ATPase activity was prevented in the animals exposed to HBO treatment within the first 24 h of reperfusion. Our results suggest that global cerebral ischemia induces significant alterations in the hippocampal SOD and Na(+),K(+)-ATPase activities during different periods of reperfusion. Enhanced SOD activity and preserved Na(+),K(+)-ATPase activity within particular periods of reperfusion, could be indicators of a possible beneficial role of HBO treatment in severe brain ischemia.

The role of mitochondria and oxidative stress in neuronal damage after brief and prolonged seizures

Studies in vitro and in other disease states where excitotoxicity is believed to be important have demonstrated that mitochondrial function is a critical determinant of cell death, reflecting key roles in intracellular calcium homeostasis, energy production and oxidative stress. Central to this is the process of mitochondrial permeability transition, for which there are numerous influencing factors, although many, if not all, may specifically act though effects on the redox state of the cell and oxidative stress. Mitochondrial function in relation to seizure-induced cell death has been little studied until recently, but there is now accumulating evidence that similar mechanisms operate, certainly in cell death, following prolonged seizures. To what extent these same mechanisms might contribute to non-fatal but pathologically significant functional cellular changes in epilepsy, and the significance of reported free radical production after brief seizures is as yet uncertain. However, with the wide range of established techniques available to study mitochondrial function and oxidative stress, and those currently under development, these questions are undoubtedly answerable in the near future. Increased understanding of the mechanisms involved in seizure-induced cellular damage is an essential basis for the development of rational neuroprotective strategies.

Sleep deprivation decreases superoxide dismutase activity in rat hippocampus and brainstem

Sleep deprivation by the disk-over-water technique results in a predictable syndrome of physiological changes in rats. It has been proposed that reactive oxygen species (ROS) may be responsible for some of these effects. A variety of antioxidative enzymes such as superoxide dismutase (SOD) and glutathione peroxidase (GPx) help to regulate the level of ROS. In this study we investigated the effects of prolonged (5-11 days) sleep deprivation on the activities of SOD and GPx as well as the metabolic activity of the mitochondria (using alamar blue) in several brain regions (cortex, hippocampus, hypothalamus, brainstem and cerebellum). We show that prolonged sleep deprivation significantly decreased Cu/Zn-SOD activity in the hippocampus and brainstem, suggesting an alteration in the metabolism of ROS resulting in oxidative stress.

Catalase and alpha-tocopherol attenuate blood-brain barrier breakdown in pentylenetetrazole-induced epileptic seizures in acute hyperglycaemic rats

Experimental data indicate that acute hyperglycaemia can aggravate the consequences of epileptic seizures on the permeability of the blood-brain barrier (BBB). The purpose of this study was to examine the effects of chronic administration of alpha -tocopherol (vitamin E) and acute catalase administration on the disrupted BBB during experimentally pentylenetetrazole-induced status epilepticus in acute hyperglycaemic rats. The integrity of the BBB was tested using the Evans Blue (EB) dye extravasation. The concentration of EB dye was measured in four regions of the brain. Epileptic seizures induced a significant increase in EB dye extravasation in the brain regions compared with that of the groups of rats treated with saline, glucose, catalase and alpha -tocopherol (P< 0.01). The content of EB dye in the brain regions of animals in the acute hyperglycaemia plus epileptic group was higher than that of the saline, glucose, catalase, alpha -tocopherol and epileptic groups (P< 0.01). The increased EB dye transfer from blood to the brain in status epilepticus and acute hyperglycaemia plus status epilepticus was attenuated by the treatment with catalase and alpha -tocopherol. These data suggest that a partial reduction in the production of reactive oxygen species by catalase and alpha -tocopherol contributes to decreases in the content of EB dye across the BBB during pentylenetetrazole-induced status epilepticus in acute hyperglycaemic rats.

Altered activities of rat brain metabolic enzymes in electroconvulsive shock-induced seizures

PURPOSE

Electroconvulsive shock (ECS) induces generalized seizure activity and provides an excellent experimental model for studying the effects of global electrical stimulation on various biochemical parameters. The aim of this work was to investigate the influence of a single or repeated ECS-induced seizures on rat brain metabolism.

METHODS

Experiments were carried out on female Hannover-Wistar rats divided into four groups: (a) the control group, which was intact; (b) the 1ECS group, which was killed 2 h after single ECS; (c) the 5ECS group with 24 h rest, which was killed 24 h after the fifth daily ECS; and (d) the 10ECS group with 48 h rest, which was given ECS every 48 h and killed 24 h after the tenth ECS. Activities of glutamate dehydrogenase (GLDH), aspartate-aminotransferase (AST), alanine-aminotransferase (ALT), gamma-glutamyltransferase (GGT), alkaline phosphatase (ALP), lactate dehydrogenase (LDH), and creatine kinase (CK) in the frontal cortex, cerebellum, hippocampus, and pons/medulla regions were determined.

RESULTS

Increased AST, ALP, LDH, and CK activities were detected in all examined regions of the 1ECS and 5ECS groups. ALT activity was increased in both these groups, except in the hippocampus of the 5ECS group, where increased GGT activity was detected. In the hippocampus of 1ECS group, GLDH activity was decreased. Increased hippocampal AST and cortical CK activities, together with increased LDH activities in the cortex, cerebellum, and pons/medulla, were found.

CONCLUSIONS

ECS treatment induces region-specific changes in metabolic activity. Neither a 24-h nor a 48-h rest period between two ECSs was sufficient for complete brain recovery, although most of the observed increased enzyme activities present in 1ECS and 5ECS were not present in 10ECS.