Inducible brain COX-2 facilitates the recurrence of hippocampal seizures in mouse rapid kindling

Anticonvulsant and hypnotic effects of amiodarone

Amiodarone hydrochloride is a potent anti-arrhythmic agent, known as a multiple ion-channel blocker in the heart. Although it has been detected in the rat brain, there are no data related to its central nervous system (CNS) effects. In this study, we evaluated anticonvulsant and hypnotic effects of amiodarone. Convulsions were induced by phentylenetetrazole (PTZ) (100 mg/kg) or caffeine (300 mg/kg) in mice. In both models, amiodarone prolonged both latency period and time to death, and acted as an anticonvulsant drug. It was found to be more effective in the PTZ model than in the caffeine model; none of the animals treated with 150 mg/kg dose amiodarone had died in the PTZ model. For hypnotic effect, sleeping was induced with pentobarbital (35 mg/kg) in rats. Amiodarone dose-dependently increased the sleeping time (677.7%-725.9%). In the sleeping test, all rats in 200 mg/kg amiodarone group died. In conclusion, anticonvulsant and hypnotic effects of amiodarone have shown the depressant effects on CNS. These effects may be dependent on its pharmacological properties.

Alterations in excitotoxicity and prostaglandin metabolism in a transgenic mouse model of Alzheimer's disease

To address the potential impact of presenilin mutations on the prostaglandin metabolism in a neurodegenerative model of glutamatergic excitotoxicity, we injected kainic acid intraperitoneally (30mg/kg body weight) into mice over-expressing the human N141I mutation of presenilin-2, which is known to cause an early-onset form of Alzheimer's disease. We compared the seizure activity as well as seizure lethality in 2- and 6-month-old mice, transgenic for the above-mentioned point mutation, and their wildtype littermates and found that mice harboring the hN141I mutation showed a relative resistance to excitotoxic treatment. This was associated with a constituitively reduced expression of the cyclooxygenases COX-1 and COX-2 in the hippocampus of N141I presenilin-2 mice and a reduced induction of COX-2 expression post-kainate injection. In the past, clinical trials have suggested that both non-steroidal anti-inflammatory drugs, which impact upon a cell's prostaglandin metabolism, and glutamatergic antagonists might be of benefit to patients suffering from Alzheimer's-type dementias. Yet, the exact mechanism by which these drugs are beneficial remains unclear, although it seems possible that presenilins might be implicated in the process, at least in the case of early-onset forms. The data presented here strongly support the notion of an implication of presenilins in the alterations in the prostaglandin system, which have been observed in Alzheimer's disease and may contribute to the underlying pathogenesis of the disease.

Effects of SC58236, a selective COX-2 inhibitor, on epileptogenesis and spontaneous seizures in a rat model for temporal lobe epilepsy

Inflammation is an important biological process that is activated after status epilepticus and could be implicated in the development of epilepsy. Here we tested whether an anti-inflammatory treatment with a selective cox-2 inhibitor (SC58236) could prevent the development of epilepsy or modify seizure activity during the chronic epileptic phase. SC58236 was orally administered (10mg/kg) during the latent period for 7 days, starting 4h after electrically induced SE. Seizures were monitored using EEG/video monitoring until 35 days after SE. Cell death and inflammation were investigated using immunocytochemistry (NeuN and Ox-42). Sprouting was studied using Timm's staining after 1 week and after 4-5 months when rats were chronic epileptic. SC58236 was also administered during 5 days in chronic epileptic rats. Hippocampal EEG seizures were continuously monitored before, during and after treatment. SC58236 effectively reduced PGE(2) production but did not modify seizure development or the extent of cell death or microglia activation in the hippocampus. SC58236 treatment in chronic epileptic rats did not show any significant change in seizure duration or frequency of daily seizures. The fact that cox-2 inhibition, which effectively reduced prostaglandin levels, did not modify epileptogenesis or chronic seizure activity suggests that this type of treatment (starting after SE) will not provide an effective anti-epileptogenic or anti-epileptic therapy.

Involvement of endogenous prostaglandin F2alpha on kainic acid-induced seizure activity through FP receptor: the mechanism of proconvulsant effects of COX-2 inhibitors

COX-2 and prostaglandins (PGs) might play important roles in epilepsy. In kainic acid-induced seizures, the brain largely increases PGD(2), first from COX-1 and later COX-2-induced PGF(2alpha). Pre-treatment with COX-2 inhibitors such as indomethacin, nimesulide, and celecoxib is known to aggravate kainic acid (KA)-induced seizure activity. However it is not known whether the proconvulsant effect of those non-steroidal anti-inflammatory drugs (NSAIDs) is due to changes in endogenous prostaglandins (PGs), or what types of PGs are involved. The purpose of this study was to determine the effect of intracisternally administered PGs on KA-induced seizures aggravated by pre- or post-treatment with COX-2 inhibitors. Systemic KA injection (10 mg/kg i.p.) in mice evoked mild seizure activity within 15 min. PGs were administrated intracisternally 20 min prior to KA administration. COX inhibitors (indomethacin, nimesulide, and ketoprofen, 10 mg/kg i.p.) were injected 1 h before or 15 min after KA. An additional COX-2 inhibitor, celecoxib, was administered orally. Intracisternally administered PGF(2alpha) (700 ng), but not PGD(2) (700 ng) or PGE(2) (700 ng) completely alleviated KA-induced seizures potentiated by COX-2 inhibitors, and also reduced KA-induced hippocampal neuronal death aggravated by indomethacin. PGF(2alpha) alone did not affect KA-induced seizures. However, an FP receptor antagonist, AL 8810 (10 or 50 ng) which is an 11beta-fluoro analogue of PGF(2alpha) potentiated KA-induced seizure activity dose-dependently. In summary, pre- or post-treatment with COX-2 inhibitors aggravates KA-induced seizures, which suggests to change the endogenous PGF(2alpha). Seizure-induced PGF(2alpha) might act as an endogenous anticonvulsant through FP receptors.

Rofecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor increases pentylenetetrazol seizure threshold in mice: possible involvement of adenosinergic mechanism

Multiple lines of investigations have explored the role of cyclooxygenases (COX) in epilepsy and related neuropsychiatric disorders. Cyclooxygenase particularly, COX-2 expression was found to increase in brain during seizure paradigms. The present study was carried out to investigate the effect of rofecoxib, a selective COX-2 inhibitor against pentylenetetrazol (PTZ i.v.) seizure threshold in mice. The study was further extended to elucidate the possible involvement of adenosinergic mechanism in mediating its anticonvulsant action. Minimal dose of PTZ (i.v., mg/kg) needed to induce different phases (myoclonic jerks, generalized clonus and tonic extension) of PTZ convulsions were noted as an index of seizure threshold. Acute administration of rofecoxib (4mg/kg, i.p.) before PTZ infusion produced an elevation of seizure threshold for all the phases of convulsions. A lower dose of rofecoxib (2mg/kg, i.p.) showed an increase in PTZ seizure threshold for the onset of myoclonic jerks and tonic extension phases but not for generalized clonus. A still lower dose of rofecoxib (1mg/kg, i.p.) failed to increase the threshold in any of the convulsive phases induced by PTZ i.v. infusion. Pretreatment with sub-effective dose of rofecoxib (1mg/kg, i.p.) enhanced the action of sub-protective doses of either adenosine (25mg/kg, i.p.) or 2-chloroadenosine (1 or 2mg/kg, i.p.) in increasing the seizure threshold. On the contrary, treatment with caffeine (100 or 200mg/kg, i.p.) or theophylline (50 or 100mg/kg, i.p.), both non-selective A(1)/A(2) adenosine receptor antagonists reversed the anticonvulsant effect of rofecoxib (4mg/kg, i.p.). Further, dipyridamole (5mg/kg, i.p.), an adenosine uptake inhibitor displayed an anticonvulsant effect with rofecoxib (1mg/kg, i.p.). The study for the first time demonstrated the possible involvement of adenosinergic system in the anticonvulsant effects of rofecoxib against PTZ i.v. seizure threshold paradigm in mice.

Neuroprotective effect of nimesulide, a preferential COX-2 inhibitor, against pentylenetetrazol (PTZ)-induced chemical kindling and associated biochemical parameters in mice

Brain cyclooxygenases (COX), the rate-limiting enzyme in prostaglandin synthesis, is rapidly and transiently induced by convulsions in hippocampal and cortical neurons. Previous studies have explored the protective effect of naproxen (non-selective COX-inhibitor) or rofecoxib (selective COX-2 inhibitor) against chemical kindling in mice. With this background, the present study was designed to explore the possible effect of nimesulide (a preferential COX-2 inhibitor) against pentylenetetrazol (PTZ)-induced kindling epilepsy in mice. To induce kindling, PTZ was injected in a subconvulsive dose (40 mg/kg, i.p.) every other day for 15 days. Nimesulide (2.5 or 5 mg/kg, p.o.) was administered each day 45 min before either PTZ or vehicle challenge. The intensity of kindling was assessed immediately after PTZ administration according to a prevalidated scoring scale. On 16th day i.e. 24 h after the last dose of PTZ, animals were sacrificed and various biochemical parameters were assessed in the whole brain. Compared with normal control group, PTZ-kindled mice had significantly higher levels of malondialdehyde, nitrite, myeloperoxidase but had lower levels of reduced glutathione in the whole brain homogenate. Chronic treatment with nimesulide (2.5 or 5 mg/kg, p.o.) for 15 days showed significant decrease in kindling score and could play a role in controlling the accompanying biochemical alterations due to PTZ. These results suggested that nimesulide, a preferential COX-2 inhibitor offered neuroprotection against PTZ-induced kindling in mice.

Roles of prostaglandin synthesis in excitotoxic brain diseases

Cyclooxygenase (COX) is a rate-limiting enzyme in prostaglandin synthesis. COX consists of two isoforms, constitutive COX-1 and inducible COX-2. We have first found that COX-2 expression in the brain is tightly regulated by neuronal activity under physiological conditions, and electroconvulsive seizure robustly induces COX-2 mRNA in the brain. Our recent in-depth studies reveal COX-2 expression is divided into two phases, early in neurons and late in non-neuronal cells, such as endothelial cells or astrocytes. In this review, we present that early synthesized COX-2 facilitates the recurrence of hippocampal seizures in rapid kindling model, and late induced COX-2 stimulates hippocampal neuron loss after kainic acid treatment. Hence, we consider the potential role of COX-2 inhibitors as a new therapeutic drug for a neuronal loss after seizure or focal cerebral ischemia. The short-term and sub-acute medication of selective COX-2 inhibitors that suppresses an elevation of prostaglandin E(2) (PGE(2)) may be an effective treatment to prevent neuronal loss after onset of neuronal excitatory diseases. This review also discusses a novel role of vascular endothelial cells in brain diseases. We found that these cells produce PGE(2) by synthesizing COX-2 and microsomal prostaglandin E synthase-1 (mPGES-1) in response to excitotoxicity and neuroinflammation. We also show a possible mechanisms of neuronal damage associated with seizure via astrocytes and endothelial cells. Further analysis of the interaction among neurons, astrocytes and endothelial cells may provide a better understanding of the processes of neuropathological disorders, as well as facilitating the development of new treatments.

Angiotensin-(1-7)-induced plasticity changes in the lateral amygdala are mediated by COX-2 and NO

It is known from studies outside the brain that upon binding to its receptor, angiotensin-(1-7) elicits the release of prostanoids and nitric oxide (NO). Cyclooxygenase (COX) is a key enzyme that converts arachidonic acid to prostaglandins. Since there are no data available so far on the role of COX-2 in the amygdala, in a first step we demonstrated that the selective COX-2 inhibitor NS-398 significantly reduced the probability of long-term potentiation (LTP) induction in the lateral nucleus of the amygdala. Similarly, in COX-2(-/-) mice, LTP induced by external capsule (EC) stimulation was impaired. Second, we evaluated the action of angiotensin-(1-7) in the amygdala. In wild-type mice, angiotensin-(1-7) increased LTP. This LTP-enhancing effect of Ang-(1-7) was not observed in COX-2(+/-) mice. However, in COX-2(-/-) mice, Ang-(1-7) caused an enhancement of LTP similar to that in wild-type mice. The NO synthetase inhibitor L-NAME blocked this angiotensin-(1-7)-induced increase in LTP in COX-2(-/-) mice. Low-frequency stimulation of external capsule fibers did not cause long-term depression (LTD) in drug-free and angiotensin-(1-7)-treated brain slices in wild-type mice. In contrast, in COX-2(-/-) mice, angiotensin-(1-7) caused stable LTD. Increasing NO concentration by the NO-donor SNAP also caused LTD in wild-type mice. Our study shows for the first time that LTP in the amygdala is dependent on COX-2 activity. Moreover, COX-2 is involved in the mediation of angiotensin-(1-7) effects on LTP. Finally, it is recognized that there is a molecular cross-talk between COX-2 and NO that may regulate synaptic plasticity.

Effect of cyclooxygenase inhibitors on pentylenetetrazol (PTZ)-induced convulsions: Possible mechanism of action

Cyclooxygenase (COX) is reported to play a significant role in neurodegenerative and neuropsychiatric disorders, and may play a significant role in the pathogenesis of epilepsy. Various neurotransmitter abnormalities, especially of GABA and glutamate, have been reported to play a key role in the pathophysiology of epilepsy. The objective of the present study was to elucidate the effect of cyclooxygenase inhibitors on pentylenetetrazol (PTZ)-induced (80 mg/kg) convulsions in mice with possible mechanism of action. Various COX-inhibitors were administered 45 min prior to the PTZ administration. Onset, duration of clonic convulsions and percentage mortality/recovery were recorded. Pretreatment with COX-inhibitors aspirin (10 and 20 mg/kg, p.o.), naproxen (7 and 14 mg/kg, p.o.), nimesulide (1-5 mg/kg, p.o.) or rofecoxib (1-4 mg/kg, p.o.) dose-dependently showed protection against PTZ-induced convulsions. COX-2 inhibitors were more effective as compared to non-selective COX-inhibitors. Rofecoxib (1 mg/kg) or nimesulide (1 mg/kg) also enhanced the sub-protective effect of diazepam or muscimol showing GABAergic modulation of COX-2 inhibitors. COX-2 inhibitors also antagonized the effect of flumazenil (4 mg/kg)- against PTZ-induced convulsions further confirming the GABAergic mechanism. In conclusion, the results of the present study strongly suggest the possible role of cyclooxygenase isoenzymes in the pathophysiology of epilepsy and the use of COX-inhibitors as an adjuvant therapy in the treatment of epilepsy.

The role of inflammation in CNS injury and disease

For many years, the central nervous system (CNS) was considered to be 'immune privileged', neither susceptible to nor contributing to inflammation. It is now appreciated that the CNS does exhibit features of inflammation, and in response to injury, infection or disease, resident CNS cells generate inflammatory mediators, including proinflammatory cytokines, prostaglandins, free radicals and complement, which in turn induce chemokines and adhesion molecules, recruit immune cells, and activate glial cells. Much of the key evidence demonstrating that inflammation and inflammatory mediators contribute to acute, chronic and psychiatric CNS disorders is summarised in this review. However, inflammatory mediators may have dual roles, with detrimental acute effects but beneficial effects in long-term repair and recovery, leading to complications in their application as novel therapies. These may be avoided in acute diseases in which treatment administration might be relatively short-term. Targeting interleukin (IL)-1 is a promising novel therapy for stroke and traumatic brain injury, the naturally occurring antagonist (IL-1ra) being well tolerated by rheumatoid arthritis patients. Chronic disorders represent a greater therapeutic challenge, a problem highlighted in Alzheimer's disease (AD); significant data suggested that anti-inflammatory agents might reduce the probability of developing AD, or slow its progression, but prospective clinical trials of nonsteroidal anti-inflammatory drugs or cyclooxygenase inhibitors have been disappointing. The complex interplay between inflammatory mediators, ageing, genetic background, and environmental factors may ultimately regulate the outcome of acute CNS injury and progression of chronic neurodegeneration, and be critical for development of effective therapies for CNS diseases.

Effect of rofecoxib, a cyclo-oxygenase-2 inhibitor, on various biochemical parameters of brain associated with pentylenetetrazol-induced chemical kindling in mice

Cyclo-oxygenase (COX) has been reported to play a significant role in neurodegeneration and other brain-related disorders. Recent studies have reported that COX plays a significant role in the pathophysiology of brain-related disorders and COX-2 inhibitors could be useful drug therapy in neurodegenerative disorders. The aim of the present study was to explore the possible role of COX and the effect of COX-2 inhibitor, rofecoxib in epilepsy. In the present study, kindling was induced in mice by chronic administration of a subconvulsive dose of pentylenetetrazol (PTZ, 40 mg/kg, i.p.) on every other day for a period of 15 days. Rofecoxib was administered orally daily 45 min before either PTZ or vehicle. The kindling score was recorded after PTZ administration. Seizure severity was measured according to a prevalidated scoring scale. Biochemical estimations were performed on the day 16 of PTZ treatment (24 h after the last dose of PTZ). Chronic treatment with selective COX-2 inhibitor, rofecoxib (2.0 and 5.0 mg/kg, p.o.) for 15 days showed significant decrease in PTZ-induced kindling score. Biochemical analysis showed that chronic treatment with PTZ significantly increased lipid peroxidation, nitrite levels (NO levels), and myeloperoxidase levels and decreased the reduced glutathione levels in brain homogenate. Chronic treatment with rofecoxib, a selective COX-2 inhibitor, significantly reversed the PTZ-induced kindling score as well as various biochemical alterations suggesting the use of COX-2 inhibitor rofecoxib in epilepsy. In conclusion, results of the present study suggested that COX-2 plays an important role in the pathophysiology of PTZ-induced kindling in mice and rofecoxib is protective against various biochemical alterations against PTZ-induced kindling in mice.

Contributions of cyclooxygenase-2 to neuroplasticity and neuropathology of the central nervous system

Cyclooxygenase (COX) enzymes, or prostaglandin-endoperoxide synthases (PTGS), are heme-containing bis-oxygenases that catalyze the first committed reaction in metabolism of arachidonic acid (AA) to the potent lipid mediators, prostanoids and thromboxanes. Two isozymes of COX enzymes (COX-1 and COX-2) have been identified to date. This review will focus specifically on the neurobiological and neuropathological consequences of AA metabolism via the COX-2 pathway and discuss the potential therapeutic benefit of COX-2 inhibition in the setting of neurological disease. However, given the controversy surrounding the use of COX-2 selective inhibitors with respect to cardiovascular health, it will be important to move beyond COX to identify which down-stream effectors are responsible for the deleterious and/or potentially protective effects of COX-2 activation in the setting of neurological disease. Important advances toward this goal are highlighted herein. Identification of unique effectors in AA metabolism could direct the development of new therapeutics holding significant promise for the prevention and treatment of neurological disorders.

Cyclooxygenases, lipoxygenases, and epoxygenases in CNS: Their role and involvement in neurological disorders

Three enzyme systems, cyclooxygenases that generate prostaglandins, lipoxygenases that form hydroxy derivatives and leukotrienes, and epoxygenases that give rise to epoxyeicosatrienoic products, metabolize arachidonic acid after its release from neural membrane phospholipids by the action of phospholipase A(2). Lysophospholipids, the other products of phospholipase A(2) reactions, are either reacylated or metabolized to platelet-activating factor. Under normal conditions, these metabolites play important roles in synaptic function, cerebral blood flow regulation, apoptosis, angiogenesis, and gene expression. Increased activities of cyclooxygenases, lipoxygenases, and epoxygenases under pathological situations such as ischemia, epilepsy, Alzheimer's disease, Parkinson disease, amyotrophic lateral sclerosis, and Creutzfeldt-Jakob disease produce neuroinflammation involving vasodilation and vasoconstriction, platelet aggregation, leukocyte chemotaxis and release of cytokines, and oxidative stress. These are closely associated with the neural cell injury which occurs in these neurological conditions. The metabolic products of docosahexaenoic acid, through these enzymes, generate a new class of lipid mediators, namely docosatrienes and resolvins. These metabolites antagonize the effect of metabolites derived from arachidonic acid. Recent studies provide insight into how these arachidonic acid metabolites interact with each other and other bioactive mediators such as platelet-activating factor, endocannabinoids, and docosatrienes under normal and pathological conditions. Here, we review present knowledge of the functions of cyclooxygenases, lipoxygenases, and epoxygenases in brain and their association with neurodegenerative diseases.

Prostaglandin E2 produced by late induced COX-2 stimulates hippocampal neuron loss after seizure in the CA3 region

Injection of kainic acid (KA) into the brain causes severe seizures with hippocampal neuron loss. KA has been shown to immediately induce cyclooxygenase-2 (COX-2) expression in hippocampal neurons, indicating that neuronal COX-2 might be involved in neuronal death. In this study, however, we reveal that the delayed COX-2 induction in non-neuronal cells after KA injection plays an important role in hippocampal neuron loss rather than early COX-2 expression in neurons. We find that KA microinjection into the hemilateral hippocampus shows a later induction of COX-2 expression in non-neuronal cells, such as endothelial cells and astrocytes. In the KA-injected side, PGE2 concentration gradually increases and peaks at 24 h after injection, when non-neuronal COX-2 expression also peaks. When this delayed PGE2 elevation is prevented by selective COX-2 inhibitor NS398, it can block hippocampal cell death. Moreover, COX-2 knockout mice are also resistant to neuronal death after KA treatment. These findings indicate that delayed PGE2 production by non-neuronal COX-2 may facilitate neuronal death after seizure. Inhibition of COX-2 to an extent similar to PGE2 elevation after onset of seizure may be useful to prevent neuronal death.

Ameliorative effect of pioglitazone on seizure responses in genetically epilepsy-susceptible EL mice

Pioglitazone, a peroxisome proliferator-activated receptor-gamma agonist, delayed the development of seizure responses and mildly shortened the duration of convulsion of genetically epileptic EL mice. mRNA levels of IL-1beta, IL-6 and TNF-alpha before seizure and mRNA levels of IL-6 and TNF-alpha after seizure were decreased in the brains of the mice with pioglitazone. These results suggest that pioglitazone may have ameliorative effects on epileptic seizure responses partly through the reduction of inflammatory responses in the brain.

Epileptogenesis in diacylglycerol kinase epsilon deficiency up-regulates COX-2 and tyrosine hydroxylase in hippocampus

Diacylglycerol kinase (DGK) phosphorylates the second messenger diacylglycerol (DAG) to yield phosphatidic acid, two neural signaling elements that function to modulate synaptic activity. Of the nine mammalian DGK isotypes known, DGK epsilon (DGKepsilon) shows specificity for arachidonoyldiacylglycerol (20:4-DAG) and selectively contributes to modulate brain signaling pathways linked to synaptic activity and epileptic seizure activity. In this study, we examined changes in gene transcription in a mouse kindling model of epileptogenesis using control DGKepsilon (+/+) and DGKepsilon-knockout (-/-) mice. Total RNA was isolated from the hippocampus and analyzed using RNA and DNA arrays. Significantly altered gene-expression levels were confirmed independently using Western immunoblot analysis. In agreement with our previous studies, a very few number of genes reached a significance of twofold or greater (either up- or down-regulated; p<0.05). Among the most significantly up-regulated genes in DGKepsilon (+/+) mice included those encoding the inducible prostaglandin synthase cyclooxygenase-2 (COX-2) and tyrosine hydroxylase (TH), also known as tyrosine 3-monooxygenase, the rate-limiting enzyme of catecholamine biosynthesis. Kindled DGKepsilon (-/-) animals exhibited no large increases in COX-2 or TH gene expression. These data, plus our previous findings that DGKepsilon (-/-) mice show higher resistance to electroconvulsive shock, suggest an interplay between and regulatory role for DGKepsilon, COX-2, and catecholamine signaling during kindling epileptogenesis.

Protective effect of cyclooxygenase-2 (COX-2) inhibitors but not non-selective cyclooxygenase (COX)-inhibitors on ethanol withdrawal-induced behavioural changes

Cyclooxygenase (COX) is reported to play a significant role in neurodegeneration. Recent studies have shown that chronic ethanol administration up-regulates cyclooxygenase expression. In the present study we examined the effect of nimesulide (a preferential COX-2 inhibitor), rofecoxib (a highly selective COX-2 inhibitor) or naproxen (a non-selective COX-inhibitor displaying high affinity towards the COX-1 isoenzyme) on alcohol-induced withdrawal symptoms. Mice were made physically dependent on alcohol by the chronic administration of ethanol (2 g/kg of 10% v/v), intragastrically, twice on day 1 and then once-daily on successive days for a total of 7 days. Nimesulide [2.5 mg/kg, intraperitoneally (i.p.)], rofecoxib (2 mg/kg, i.p.) or naproxen (7 mg/kg, i.p.) were administered daily for 7 days before administering alcohol intragastrically. After 24 hours of the last alcohol administration, the treatments were reversed and the mice were tested for withdrawal, so that the animals that had received COX-inhibitors followed 30 minutes later by ethanol on days 1-7 were challenged with saline. Similarly, the animals which received saline followed 30 minutes later by ethanol received only saline. Behavioural analysis revealed hyperlocomotor activity, increased anxious response and increased hyperalgesia in mice. Also, alcohol withdrawal decreased the threshold for Pentylenetetrazole-(PTZ)-induced convulsions. Pretreatment with COX-inhibitors rofecoxib (2 mg/kg, i.p.) or nimesulide (2.5 mg/kg, i.p.) displayed significant protection against ethanol-induced withdrawal symptoms, while naproxen (7 mg/kg, i.p.) was not effective in reversing alcohol-induced withdrawal symptoms. The results of the present study suggest strongly the possible role of cyclooxygenases, particularly COX-2 inhibitors, on ethanol-induced withdrawal symptoms and the potential use of COX-2 inhibitors in their prevention and treatment.

Cyclooxygenase-2 expression is induced in rat brain after kainate-induced seizures and promotes neuronal death in CA3 hippocampus

Cyclooxygenase-2 (COX-2) is the predominant isoform of cyclooxygenase in brain. COX-2 activity produces oxidative stress and results in the production of prostaglandins that have many injurious effects. COX-2 transcription is induced by synaptic activity; therefore, COX-2 activity could contribute to epileptic neuronal injury. To address this hypothesis, COX-2 protein expression and PGE2 production were determined after kainate-induced limbic seizures in rats. The effects of a specific COX-2 inhibitor, SC58125, on neuronal survival and PGE2 concentration in the hippocampus were also determined. COX-2 protein expression was increased in CA3, dentate gyrus, and cortex at 18-24 h after seizures. Hippocampal PGE2 levels were increased at 24 h following seizures, and treatment with the selective COX-2 inhibitor SC58125, 3 mg/kg p.o., attenuated the increase in PGE2 concentration. The survival of CA3 neurons at 7 days after seizures was increased in rats treated with SC58125 compared to vehicle controls. There was no effect of drug treatment on body or brain temperature, nor on the duration or rate of Type IV EEG activity. These results suggest that COX-2 activity can contribute to epileptic neuronal injury and that selective COX-2 inhibitors are neuroprotective.

EFFECT OF NAPROXEN, A NON-SELECTIVE CYCLO-OXYGENASE INHIBITOR, ON PENTYLENETETRAZOL-INDUCED KINDLING IN MICE

1. Epilepsy is one of the major neurological disorders of the brain, affecting approximately 0.5-1.0% of the population worldwide. Various neurotransmitter abnormalities, especially of GABA and glutamate, have been reported to play a key role in the pathophysiology of epilepsy. 2. Cyclo-oxygenase (COX) is the rate-limiting enzyme in the production of prostaglandins and, as such, is a key target for many anti-inflammatory drugs. Cyclo-oxygenase has been reported to play a significant role in neurodegeneration. Recent studies have reported that COX plays a significant role in the pathophysiology of epilepsy. 3. The aim of the present study was to explore the possible role of COX and the effect of COX inhibitors in epilepsy. 4. Kindling is a chronic model of epilepsy. In the present study, kindling was induced in mice by chronic administration of a subconvulsive dose of pentylenetetrazole (PTZ; 40 mg/kg) on every other day for a period of 15 days. Naproxen was administered daily 45 min before PTZ or vehicle. The kindling score was recorded after PTZ administration. Seizure severity was measured according to a prevalidated scoring scale. Biochemical estimations were performed immediately after recording behavioural parameters on the 16th day of PTZ treatment. 5. Chronic treatment with PTZ significantly induced kindling in mice. Pretreatment with the non-selective COX inhibitor naproxen (7 and 14 mg/kg, i.p.) showed significant protection against PTZ-induced kindling in mice. Biochemical analysis revealed that chronic treatment with PTZ significantly increased lipid peroxidation and nitrite levels (NO levels), but decreased reduced glutathione (GSH) levels in brain homogenates. 6. In conclusion, the results of the present study strongly suggest that COX plays an important role in the pathophysiology of PTZ-induced kindling in mice and that COX inhibitors could be a useful neuroprotective strategy for the treatment of epilepsy.