Markers Of Excitotoxicity Research Articles

Anticonvulsant and neuroprotective effects of carbamazepine-levetiracetam adjunctive treatment in convulsive status epilepticus rat model: Inhibition of cholinergic transmission

This study evaluated the anticonvulsant and neuroprotective effects of carbamazepine (CBZ), levetiracetam (LEV), and CBZ + LEV adjunctive treatment in convulsive status epilepticus (CSE) rat model.Twenty-five male Wistar rats were randomized into five groups (n = 5). Groups I and II received 0.2 ml of normal saline intraperitoneally (i.p), while groups III-V received CBZ (25 mg/kg i.p), LEV (50 mg/kg i.p) or combination of sub-therapeutic doses of CBZ (12.5 mg/kg i.p) and LEV (25 mg/kg i.p). Thirty minutes later, seizure was kindled with pilocarpine hydrochloride (350 mg/kg) in group II-V rats. Seizure indices, markers of excitotoxicity, and astroglioses were determined, while the hippocampal morphometry was also evaluated. The data was analysed using descriptive and inferential statistics, while the results were presented as mean ± SEM in graphs or tables, and the level of significance was taken at p < 0.05.The anticonvulsant treatments delayed the inception of seizure indices (p = 0.0006), while the percentage mortality decreased significantly (p = 0.0001) in all the treatment groups. The hippocampal concentrations of acetylcholine, malondialdehyde, and tissue necrotic factor-alpha decreased significantly (p = 0.0077) in all the treated group relative to the positive control. The reactive astrogliosis in the hippocampus (CA 1) increased significantly (p = 0.0001) compared with the control but abrogated in all the treatment groups relative to the positive control.The anticonvulsant and neuroprotective effects are in this order: LEV < CBZ + CBZ < CBZ. The drug efficacy is attributable to the inhibition of cholinergic transmission.

GABAergic/glutamatergic imbalance relative to excessive neuroinflammation in autism spectrum disorders.

BackgroundAutism spectrum disorder (ASD) is characterized by three core behavioral domains: social deficits, impaired communication, and repetitive behaviors. Glutamatergic/GABAergic imbalance has been found in various preclinical models of ASD. Additionally, autoimmunity immune dysfunction, and neuroinflammation are also considered as etiological mechanisms of this disorder. This study aimed to elucidate the relationship between glutamatergic/ GABAergic imbalance and neuroinflammation as two recently-discovered autism-related etiological mechanisms.MethodsTwenty autistic patients aged 3 to 15 years and 19 age- and gender-matched healthy controls were included in this study. The plasma levels of glutamate, GABA and glutamate/GABA ratio as markers of excitotoxicity together with TNF-α, IL-6, IFN-γ and IFI16 as markers of neuroinflammation were determined in both groups.ResultsAutistic patients exhibited glutamate excitotoxicity based on a much higher glutamate concentration in the autistic patients than in the control subjects. Unexpectedly higher GABA and lower glutamate/GABA levels were recorded in autistic patients compared to control subjects. TNF-α and IL-6 were significantly lower, whereas IFN-γ and IFI16 were remarkably higher in the autistic patients than in the control subjects.ConclusionMultiple regression analysis revealed associations between reduced GABA level, neuroinflammation and glutamate excitotoxicity. This study indicates that autism is a developmental synaptic disorder showing imbalance in GABAergic and glutamatergic synapses as a consequence of neuroinflammation.

Neuropathological responses to chronic NMDA in rats are worsened by dietary n-3 PUFA deprivation but are not ameliorated by fish oil supplementation.

BackgroundDietary long-chain n-3 polyunsaturated fatty acid (PUFA) supplementation may be beneficial for chronic brain illnesses, but the issue is not agreed on. We examined effects of dietary n-3 PUFA deprivation or supplementation, compared with an n-3 PUFA adequate diet (containing alpha-linolenic acid [18:3 n-3] but not docosahexaenoic acid [DHA, 22:6n-3]), on brain markers of lipid metabolism and excitotoxicity, in rats treated chronically with NMDA or saline.MethodsMale rats after weaning were maintained on one of three diets for 15 weeks. After 12 weeks, each diet group was injected i.p. daily with saline (1 ml/kg) or a subconvulsive dose of NMDA (25 mg/kg) for 3 additional weeks. Then, brain fatty acid concentrations and various markers of excitotoxicity and fatty acid metabolism were measured.ResultsCompared to the diet-adequate group, brain DHA concentration was reduced, while n-6 docosapentaenoic acid (DPA, 22:5n-6) concentration was increased in the n-3 deficient group; arachidonic acid (AA, 20:4n-6) concentration was unchanged. These concentrations were unaffected by fish oil supplementation. Chronic NMDA increased brain cPLA2 activity in each of the three groups, but n-3 PUFA deprivation or fish oil did not change cPLA2 activity or protein compared with the adequate group. sPLA2 expression was unchanged in the three conditions, whereas iPLA2 expression was reduced by deprivation but not changed by supplementation. BDNF protein was reduced by NMDA in N-3 PUFA deficient rats, but protein levels of IL-1β, NGF, and GFAP did not differ between groups.ConclusionsN-3 PUFA deprivation significantly worsened several pathological NMDA-induced changes produced in diet adequate rats, whereas n-3 PUFA supplementation did not affect NMDA induced changes. Supplementation may not be critical for this measured neuropathology once the diet has an adequate n-3 PUFA content.

C-fos mRNA Expression in Rat Cortical Neurons During Glutamate-Mediated Excitotoxicity

We have previously reported that exposure of mouse cerebellar granule cells (mCGCs) to excitotoxic concentrations of glutamate (Glu) induced a delayed, elevated, and sustained expression of c-fos mRNA, which was N-methyl-D-aspartic acid (NMDA) receptor mediated. In this study, the overstimulation of Glu receptors in primary rat cortical neurons by excitotoxins was used to study the cellular events triggering excitotoxic neuronal cell death, as the rat is the preferred species in regulatory and nonregulatory toxicological investigations. Exposure of rat cortical neurons to excitotoxins at high, toxic concentrations showed a change in the c-fos mRNA expression profile from a transient expression to one of sustained elevated levels. The excitotoxins induced much higher levels of c-fos mRNA in rat cortical neurons than in the mouse CGC system. Glu-induced c-fos mRNA expression, under excitotoxic conditions, was inhibited by D-2-amino-5-phosphonopentanoate (AP5) but not 6-cyano-7-nitro-quinoxaline-2,3-dione (CNQX), indicating an event mediated by the NMDA subtype of Glu receptors. Using 12 compounds, which covered a range of nontoxic, toxic, and excitotoxic effects on rat cortical neurons, excitotoxicity was paralleled by a sustained, elevated c-fos mRNA expression. Furthermore, on account of the high expression levels of c-fos mRNA under excitotoxic conditions, it is suggested that an unambiguous elevation in c-fos mRNA expression at a single time point of 60 min can be used to predict the excitotoxic properties of a range of functionally different chemical compounds. In view of the high levels of expression of c-fos mRNA, the rat cortical cell system may also be used as a more sensitive model than mCGCs for investigations into early markers of excitotoxicity.