Differential Expression Patterns of TDP-43 in Single Moderate versus Repetitive Mild Traumatic Brain Injury in Mice.

Traumatic brain injury (TBI) is a disabling disorder and a major cause of death and disability in the world. Both single and repetitive traumas affect the brain acutely but can also lead to chronic neurodegenerative changes. Clinical studies have shown some dissimilarities in transactive response DNA binding protein 43 (TDP-43) expression patterns following single versus repetitive TBI. We explored the acute cortical post-traumatic changes of TDP-43 using the lateral fluid percussion injury (LFPI) model of single moderate TBI in adult male mice and investigated the association of TDP-43 with post-traumatic neuroinflammation and synaptic plasticity. In the ipsilateral cortices of animals following LFPI, we found changes in the cytoplasmic and nuclear levels of TDP-43 and the decreased expression of postsynaptic protein 95 within the first 3 d post-injury. Subacute pathological changes of TDP-43 in the hippocampi of animals following LFPI and in mice exposed to repetitive mild TBI (rmTBI) were studied. Changes in the hippocampal TDP-43 expression patterns at 14 d following different brain trauma procedures showed pathological alterations only after single moderate, but not following rmTBI. Hippocampal LFPI-induced TDP-43 pathology was not accompanied by the microglial reaction, contrary to the findings after rmTBI, suggesting that different types of brain trauma may cause diverse pathophysiological changes in the brain, specifically related to the TDP-43 protein as well as to the microglial reaction. Taken together, our findings may contribute to a better understanding of the pathophysiological events following brain trauma.

Long-Term Effects of Repetitive Mild Traumatic Injury on the Visual System in Wild-Type and TDP-43 Transgenic Mice.

Little is known about the impairments and pathological changes in the visual system in mild brain trauma, especially repetitive mild traumatic brain injury (mTBI). The goal of this study was to examine and compare the effects of repeated head impacts on the neurodegeneration, axonal integrity, and glial activity in the optic tract (OT), as well as on neuronal preservation, glial responses, and synaptic organization in the lateral geniculate nucleus (LGN) and superior colliculus (SC), in wild-type mice and transgenic animals with overexpression of human TDP-43 mutant protein (TDP-43G348C) at 6 months after repeated closed head traumas. Animals were also assessed in the Barnes maze (BM) task. Neurodegeneration, axonal injury, and gliosis were detected in the OT of the injured animals of both genotypes. In the traumatized mice, myelination of surviving axons was mostly preserved, and the expression of neurofilament light chain was unaffected. Repetitive mTBI did not induce changes in the LGN and the SC, nor did it affect the performance of the BM task in the traumatized wild-type and TDP-43 transgenic mice. Differences in neuropathological and behavioral assessments between the injured wild-type and TDP-43G348C mice were not revealed. Results of the current study suggest that repetitive mTBI was associated with chronic damage and inflammation in the OT in wild-type and TDP-43G348C mice, which were not accompanied with behavioral problems and were not affected by the TDP-43 genotype, while the LGN and the SC remained preserved in the used experimental conditions.

Repetitive Traumatic Brain Injury Is Associated With TDP-43 Alterations, Neurodegeneration, and Glial Activation in Mice.

Increasing evidence points to a relationship between repetitive mild traumatic brain injury (mTBI), the Tar DNA binding protein 43 (TDP-43) pathology and some neurodegenerative diseases, but the underlying pathophysiological mechanisms are still unknown. We examined TDP-43 regulation, neurodegeneration, and glial responses following repetitive mTBI in nontransgenic mice and in animals with overexpression of human mutant TDP-43 protein (TDP-43G348C). In the frontal cortices of the injured nontransgenic animals, early TDP-43 cytoplasmatic translocation and overexpression of the protein and its pathological forms were detected. In the injured animals of both genotypes, neurodegeneration and pronounced glial activity were detected in the optic tract. In TDP-43G348C mice, these changes were significantly higher at day 7 after the last mTBI compared with the values in the nontransgenic animals. Results of this study suggest that the changes in the TDP-43 regulation in the frontal cortices of the nontransgenic animals were a transient stress response to the brain injury. Repetitive mTBI did not produce additional TDP-43 dysregulation or neurodegeneration or pronounced gliosis in the frontal cortex of TDP-43G348C mice. Our research also suggests that overexpression of mutated human TDP-43 possibly predisposes the brain to more intense neurodegeneration and glial activation in the optic tract after repetitive mTBI.

Pattern of Neuronal and Axonal Damage, Glial Response, and Synaptic Changes in Rat Cerebellum within the First Week following Traumatic Brain Injury.

We examined damage and repair processes in the rat cerebellum within the first week following moderate traumatic brain injury (TBI) induced by lateral fluid percussion injury (LFPI) over the left parietal cortex. Rats were killed 1, 3, or 7 days after the injury or sham procedure. Fluoro-Jade B staining revealed 2 phases of neurodegenerative changes in the cell bodies and fibers: first, more focal, 1 day after the LFPI, and second, widespread, starting on post-injury day 3. Purkinje cell loss was detected in posterior lobule IX 1 day following LFPI. Apoptosis was observed in the cerebellar cortex, on days 1 and 7 following LFPI, and was not caspase- or apoptosis-inducing factor (AIF)-mediated. AIF immunostaining indicated axonal damage in the cerebellar white matter tracts 3- and 7-days post-injury. Significant astrocytosis and microgliosis were noticed on day 7 following LFPI at the sites of neuronal damage and loss. Immunohistochemical labeling with the presynaptic markers synaptophysin and growth-associated protein-43 revealed synaptic perturbations already on day 1 that were more pronounced at later time points following LFPI. These results provide new insights into pathophysiological alterations in the cerebellum and their mechanisms following cerebral TBI.

Decrease in Oxidative Stress Parameters after Post-Ischaemic Recombinant Human Erythropoietin Administration in the Hippocampus of Rats Exposed to Focal Cerebral Ischaemia.

Recombinant human erythropoietin (rhEpo) is a multi-functional drug with antioxidant potential. However, the underlying molecular mechanisms of its action are still unclear. The purpose of this study was to investigate the effects of rhEpo on the brain infarct volume as well as on the levels of the neuronal damage, oxidative stress parameters and active caspase-3, nuclear factor erythroid 2-related factor 2 (Nrf2) and haemeoxygenase-1 (HO-1) expressions in the hippocampi of rats exposed to the right middle cerebral artery occlusion (MCAO) for 1 hr. Ischaemic animals received either vehicle or rhEpo (5000 IU/kg, i.p.) immediately or 3 hr after the induction of ischaemia. Sham-operated, vehicle-treated animals served as the control group. Rats were killed 24 hr after the onset of the ischaemic or sham experimental procedure. MCAO caused ipsilateral brain infarction within the striatum and cortex. In the CA1 region of the hippocampi, we did not find significant neuronal loss, but a statistically significant rise in the active caspase-3 and Nrf2 protein expressions was registered. We detected also significant increases in the hippocampal levels of oxidative stress parameters (thiobarbituric acid-reactive substances, superoxide dismutase, glutathione peroxidase). Post-ischaemic administration of rhEpo significantly reduced the brain infarct volume, decreased levels of all tested oxidative stress parameters and increased the Nrf2 expression level. These findings suggest that decrease in oxidative stress parameters in the hippocampus could be an early indicator of post-ischaemic neuroprotective effect of rhEpo in rats exposed to focal cerebral ischaemia and that this effect could be attributable to additional post-ischaemic activation of Nrf2 endogenous antioxidant system.

Temporal pattern of neurodegeneration, programmed cell death, and neuroplastic responses in the thalamus after lateral fluid percussion brain injury in the rat.

The effects of traumatic brain injury (TBI) on the thalamus are not well characterized. We analyzed neuronal degeneration and loss, apoptosis, programmed cell death-executing pathways, and neuroplastic responses in the rat thalamus during the first week after lateral fluid percussion injury (LFPI). The most prominent neurodegenerative and neuroplastic changes were observed in the region containing the posterior thalamic nuclear group and ventral posteromedial and posterolateral thalamic nuclei ipsilateral to the LFPI. There was progressive neurodegeneration in these regions, with maximal neuronal loss on Day 7. Increases in numbers of apoptotic cells were detected on Day 1 and were enhanced on Days 3 and 7 after TBI. There was unchanged expression of active caspase-3 at all postinjury time points, but there was increased expression of apoptosis-inducing factor (AIF) on Day 7. The AIF nuclear translocation was detected on Day 1 and was maximal on Day 7. Total thalamic synaptophysin expression was unchanged, but immunostaining intensities were increased at all time points after TBI. Decreased growth-associated protein-43 expression and signal intensity were observed on Day 1. Our results suggest that progressive neuronal damage and loss, AIF signaling pathway-dependent programmed cell death, and limited neuroplastic changes occur in the rat thalamus during the first week after LFPI induction.

A single dose of PPARγ agonist pioglitazone reduces cortical oxidative damage and microglial reaction following lateral fluid percussion brain injury in rats.

Neuroprotective actions of the peroxisome proliferator-activated receptor-γ (PPARγ) agonists have been observed in various animal models of the brain injuries. In this study we examined the effects of a single dose of pioglitazone on oxidative and inflammatory parameters as well as on neurodegeneration and the edema formation in the rat parietal cortex following traumatic brain injury (TBI) induced by the lateral fluid percussion injury (LFPI) method. Pioglitazone was administered in a dose of 1mg/kg at 10min after the brain trauma. The animals of the control group were sham-operated and injected by vehicle. The rats were decapitated 24h after LFPI and their parietal cortices were analyzed by biochemical and histological methods. Cortical edema was evaluated in rats sacrificed 48h following TBI. Brain trauma caused statistically significant oxidative damage of lipids and proteins, an increase of glutathione peroxidase (GSH-Px) activity, the cyclooxygenase-2 (COX-2) overexpression, reactive astrocytosis, the microglia activation, neurodegeneration, and edema, but it did not influence the superoxide dismutase activity and the expressions of interleukin-1 beta, interleukin-6 and tumor necrosis factor-alpha in the rat parietal cortex. Pioglitazone significantly decreased the cortical lipid and protein oxidative damage, increased the GSH-Px activity and reduced microglial reaction. Although a certain degree of the TBI-induced COX-2 overexpression, neurodegeneration and edema decrease was detected in pioglitazone treated rats, it was not significant. In the injured animals, cortical reactive astrocytosis was unchanged by the tested PPARγ agonist. These findings demonstrate that pioglitazone, administered only in a single dose, early following LFPI, reduced cortical oxidative damage, increased antioxidant defense and had limited anti-inflammatory effect, suggesting the need for further studies of this drug in the treatment of TBI.

Temporal and regional changes of superoxide dismutase and glutathione peroxidase activities in rats exposed to focal cerebral ischemia.

Reactive oxygen species are important cause of tissue injury during cerebral ischemia and reperfusion (I/R). Superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) are intracellular enzymes responsible for endogenous antioxidant defense of tissues affected by I/R. The aim of this study was to examine temporal and regional changes of SOD and GSH-Px activities in animals exposed to transient focal cerebral ischemia. Male Wistar Hannover rats were subjected to the right middle cerebral artery occlusion for 2 h. The animals were sacrificed immediately, 0·5, 1, 2, 3, 6, 24, 48, 72 or 168 h after ischemic procedure. SOD and GSH-Px activities were determined spectrophotometrically in the hippocampus and parietal cortex, both unilaterally and contralaterally to the occlusion. Sham-operated animals were used as the control group. Our results indicated that transient focal cerebral ischemia causes significant changes in SOD activities in the hippocampus and parietal cortex such as in GSH-Px activities in the parietal cortex, unilaterally and contralaterally to the lesion in rats during different reperfusion periods. Statistically significant activation of GSH-Px was registered neither in the right nor in the left hippocampus of ischemic animals.

Effects of enoxaparin in the rat hippocampus following traumatic brain injury.

Purpose of this study was to investigate the effects of low molecular weight heparin, enoxaparin, on different parameters of the hippocampal damage following traumatic brain injury (TBI) in the rat. TBI of moderate severity was performed over the left parietal cortex using the lateral fluid percussion brain injury model. Animals were s.c. injected with either enoxaparin (1mg/kg) or vehicle 1, 7, 13, 19, 25, 31, 37, and 43 h after the TBI induction. Sham-operated, vehicle-treated animals were used as the control group. Rats were sacrificed 48h after the induction of TBI. Hippocampi were processed for spectrophotometric measurements of the products of oxidative lipid damage, thiobarbituric acid-reactive substances (TBARS) levels, as well as the activities of antioxidant enzymes, superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px). Moreover, the Western blotting analyses of the oxidized protein levels, expressions of cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), pro- and mature-interleukin-1ß (pro-, and mature-IL-1ß), and active caspase-3 were performed. COX-2 expressions were also explored by using immunohistochemistry. Glial fibrillary acidic protein immunochistochemistry was performed with the aim to assess the level of astrocytic activity. Fluoro-Jade B staining was used to identify the level and extent of hippocampal neuronal injury. TBI caused statistically significant increases of the hippocampal TBARS and oxidized protein levels as well as COX-2, pro-IL-1ß, and active caspase-3 overexpressions, but it did not significantly affect the SOD and GSH-Px activities, the iNOS, and mature-IL-1ß expression levels. TBI also induced hippocampal reactive astrocytosis and neurodegeneration. Enoxaparin significantly decreased the hippocampal TBARS and oxidized protein levels, COX-2 overexpression and reactive gliosis, but it did not influence the SOD and GSH-Px activities, pro-IL-1ß and active caspase-3 overexpressions as well as neurodegeneration following TBI. These findings demonstrate that enoxaparin may reduce oxidative damage, inflammation and astrocytosis following TBI in the rat and could be a candidate drug for neuroprotective treatment of this injury.

Oxidative stress parameters in different brain structures following lateral fluid percussion injury in the rat.

Free radicals mediated damage of phospholipids, proteins and nucleic acids results in subsequent neuronal degeneration and cell loss. Aim of this study was to evaluate the existence of lipid and protein oxidative damage and the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in various rat brain structures 24 h after lateral fluid percussion brain injury (LFPI). Parietal cortex, hippocampus, thalamus, entorhinal cortex, and cerebellum from the ipsilateral hemisphere were processed for analyses of the thiobarbituric acid reactive substances (TBARS) and oxidized protein levels as well as for the SOD and GSH-Px activities. Immunohistochemical detection of oxidized proteins was also performed. Results of our study showed that LFPI caused significant oxidative stress in the parietal cortex and hippocampus while other brain regions tested in this study were not oxidatively altered by LFPI. GSH-Px activities were significantly increased in the parietal cortex and hippocampus, while the SOD activities remained unchanged following LFPI in all regions investigated.

Seizure susceptibility and the brain regional sensitivity to oxidative stress in male and female rats in the lithium-pilocarpine model of temporal lobe epilepsy.

Several studies have shown the existence of sex differences in the sensitivity to various convulsants in animals and to the development of some epilepsy types in humans. The purpose of this study was to investigate whether there are sex differences in seizure susceptibility and sensitivity of different brain regions to oxidative stress in rats with status epilepticus (SE) induced by lithium-pilocarpine administration, that provides a common experimental model of temporal lobe epilepsy (TLE) in humans. Latencies to isolated full limbic seizures or SE onset as well as the number of the animals presenting full limbic seizures, SE or full limbic seizures that progressed to SE were recorded for 2 h after pilocarpine administration. Number of animals which survived 24 h after SE onset was also monitored. Levels of lipid peroxidation as well as the superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities in the piriform and entorhinal cortices, temporal neocortex, thalamus, and hippocampus in rats of both sexes, at 24 h after SE onset were determined. Results of our study showed that males developed full limbic seizures and SE more rapidly and in greater number than females. Levels of lipid peroxidation in all brain regions examined, the SOD activities in the piriform and entorhinal cortices, and temporal neocortex as well as the GSH-Px activities in the piriform and entorhinal cortices, and thalamus were significantly higher in rats with SE in comparison to the values of mentioned biochemical parameters in rats of the control groups. Lipid peroxidation level in the temporal neocortex as well as the GSH-Px activity in the hippocampus in male rats were significantly higher in comparison to the values registered in females. With the exception of the thalamus, where SOD activity in male rats with SE was significantly higher in relation to the respective control group and also to females with SE, sex differences in the response of other brain regions investigated to oxidative stress were not obtained, at 24 h after SE.

Activation of ERK and JNK MAP kinases in optic nerves of rats exposed to global cerebral ischemia.

OBJECTIVES: To determine the influence of global cerebral ischemia on the activation of extracellular-regulated kinases (ERK) and c-Jun N-terminal kinases (JNK) in optic nerves of rats exposed to different reperfusion periods. MATERIALS AND METHODS: Transient global cerebral ischemia (20-min duration) was induced by the four-vessel occlusion method. After different reperfusion periods (5 and 10 min; 1; 6 and 12 h after ischemia), optic nerves were extracted and ERK and JNK activation signals were determined by Western immunoblot analyses. RESULTS: The activation signals of ERK and JNK were detected within first 10 min of reperfusion, but striking activation for both enzymes was found 1 h after ischemia. After a transient decrease, the activation of ERK returned to peak level after 12 h of reperfusion in the second wave of kinase activation. In that period, a slight increase of JNK activation was registered. CONCLUSION: Our results demonstrated for the first time that ERK and JNK were activated in rat optic nerves during early and later periods of reperfusion, suggesting their potential active role in the response of cerebral white matter tissue to ischemic injury.

NA+, K+-ATPase activity in the brain of the rats with kainic acid-induced seizures: influence of lamotrigine.

OBJECTIVE: Kainic acid (KA) is used as an experimental agent which produces convulsions and neurotoxic lesions. Lamotrigine (LTG) is an antiepileptic drug, a glutamate release inhibitor, with action at the neuronal voltage-gated sodium channel. The aim of the present study was to investigate the Na+-K+-ATPase activity in the hippocampus and cortex of rats with KA-induced convulsions. Further, this study was also designed to investigate the influence of the LTG pre-treatment on the mentioned hippocampal and cortex changes. MATERIALS AND METHODS: The study was carried out on Hannover-Wistar rats. Na+, K+-ATPase activity from hippocampal and temporal cortex tissue was determined two hours after a single subcutaneous KA (8 mg/kg) injection as well as on the third or the fifth experimental day. LTG (30 mg/kg i.p.) was used one hour before KA application and during the next two or four consecutive days. All animals of KA and KA+LTG groups were observed during the first 2 hours after KA application and their behavior was noted. Only animals with characteristically KA-induced behavioral changes observed were used in the study. KA typical behavioral changes were confirmed with electroencephalography. RESULTS: After KA application, Na+, K+-ATPase activity was significantly inhibited. Na+-K+-ATPase activity inhibition in the hippocampus of the LTG pretreated rats on the fifth experimental day was statistically less pronounced than in KA treated rats. The LTG pretreatment showed also a protective effect on the Na+-K+-ATPase activity in the rats' brain cortex. CONCLUSION: KA systemic application induced Na+, K+- ATPase activity inhibition in the rat hippocampus and cortex and LTG pre-treatment showed a partially protective effect on the enzyme activity.

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.

Characteristics of blood-pressure control in treated hypertensive patients in Croatia.

The aim of our study was to investigate blood pressure (BP) control and different factors with possible influence on BP control in Croatian hypertensive patients. In this cross-sectional investigation, a representative sample of target populations (primary care physicians and patients) from different parts of Croatia was included according to the study protocol. During December 2003 and January 2004, we included, according to correctly completed questionnaires, 141 physicians and 814 hypertensive patients. A controlled BP (BP < 140/90 mmHg) in this hypertensive population treated with antihypertensive drugs was in 23% of patients. The analysis of BP control according to risk factors showed that significantly related with higher levels of systolic or diastolic BP were the age (poorer systolic BP control in patients older than 60 years), left ventricular hypertrophy, changes of the eye retina, smoking and diabetes mellitus. Furthermore, patients from towns closer to the hospital, from urban centers, with higher education and employed had significantly lower average BP. According to our results of hypertension control in Croatia, there is a need and a possibility for the improvement of the quality of hypertension care. The relationship between demographic and cardiovascular risk factors with poor BP control should be taken into account when treating patients.

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.

Differential effects of dihydropyridine calcium channel blockers in kainic acid-induced experimental seizures in rats.

The anticonvulsant effects of the dihydropyridine calcium channel blockers nifedipine, nicardipine and nimodipine were studied on experimental seizures induced by intra-hippocampal injection of kainic acid (KA) in chloralhydrate anesthetized Wistar rats. The rats were anesthetized and placed in a stereotaxic apparatus. After midline incision four screw electrodes were placed over the left and right frontal and parietal cortex and KA was injected into left dorsal hippocampus via 5-microliter Hamilton microsyringe. The changes in electroencephalograph (EEG) activity and EEG power spectra were recorded in basal conditions and 5, 10, 15, 30 and 60 min following KA injection. KA-induced excitatory changes in the surface EEG activity were associated with the marked increase in EEG power spectra in the frequency range from 14.5-22 Hz. Pretreatment with nifedipine, nicardipine and nimodipine revealed that they exerted certain differences in their anticonvulsant properties. Nimodipine significantly delayed the onset of seizures and prevented the KA-induced changes in EEG and in EEG power spectra in all recorded channels and in a dose dependent manner. Nifedipine exerted significant anticonvulsant effect only in channel four, while nicardipine was ineffective. Our results suggest that anticonvulsant action of some dihydropyridine calcium channel blockers, especially nimodipine may be in part independent of its antagonism on L-type voltage-gated calcium (Ca(2+)) channels.

Pentylenetetrazol-induced seizures and kindling: changes in free fatty acids, superoxide dismutase, and glutathione peroxidase activity.

The whole brain free fatty acid (FFA) level, as well as the activities of superoxide dismutase (SOD) and glutathione peroxidase (GPX) were determined in the frontal cortex, cerebellum, hippocampus, and pons-medulla region of the single pentylenetetrazol (PZT)-treated and PZT-kindled Hannover-Wistar rats. PZT administration in the convulsive dose caused significant increase of the brain FFA content. Decreased SOD activity was detected in the frontal cortex of PZT-kindled rats, whereas decreased GPX activity was found in the frontal cortex and cerebellum of all treated rats, as well as in the hippocampus and pons-medulla of PZT-kindled rats. Kindling caused distinctive change of antioxidative defense in the frontal cortex, hippocampus, and pons-medulla region.

The influence of MK-801 on the hippocampal free arachidonic acid level and Na+,K+-ATPase activity in global cerebral ischemia-exposed rats.

The influence of 20 min global cerebral ischemia on the free arachidonic acid (FAA) level and Na+,K+-ATPase activity in the rat hippocampus at different time points after ischemia was examined. In addition, the effect of MK-801 on mentioned parameters was studied. Animals were exposed to 20 min global cerebral ischemia and were sacrificed immediately, 0.5, 1, 2, 6, 24, 48, 72, and 168 h after ischemic procedure. The level of the FAA and the Na+,K+-ATPase activity was measured during all reperfusion periods examined. Various doses of MK-801 (0.3, 1.0, 3.0, and 5.0 mg/kg) had been injected 30 min before ischemic procedure started. It was found that 20 min global cerebral ischemia induces a statistically significant increase of the FAA level immediately after ischemia and during the first 0.5 h of reperfusion. After a transient decrease, the level of FAA level increased again after 24 and 168 h of recirculation. Treatment with 3.0 mg/kg of MK-801 significantly prevented the FAA accumulation immediately and 0.5 h after ischemic insult while application of 5.0 mg/kg of MK-801 exerted a protective effect during the first 24 h. Global cerebral ischemia induces the significant decline in the Na+,K+-ATPase activity in the hippocampus starting from 1 to 168 h of reperfusion. Maximal inhibition was obtained 24 h after the ischemic damage. Application of 3.0 mg/kg of MK-801 exerted statistically significant protection during the first 24 h while the treatment with 5.0 mg/kg of MK-801 prevented fall in enzymatic activity during all reperfusion periods examined. Our results suggest that, in spite of different and complex pathophysiological mechanisms involved in the increase of FAA level and the decrease of the Na+,K+-ATPase activity, blockade of NMDA receptor subtype provides a very important strategy for the treatment of the postischemic excitotoxicity.