Brain GABA Research Articles

Ameliorative Role of Certain Antioxidants Against Endosulfan Induced Neurotoxicity on GABA and Serotonin Levels in Mice Brain

Ameliorative Role of Certain Antioxidants Against Endosulfan Induced Neurotoxicity on GABA and Serotonin Levels in Mice Brain

Fipronil impairs the GABAergic brain responses of Nile Tilapia during the transition from normoxia to acute hypoxia.

γ-aminobutyric acid (GABA) is one of the main neurotransmitters involved in the adaptation processes against the damage that hypoxia can cause to the brain. Due to its antagonist action on GABA receptors, the insecticide fipronil can turn the fish more susceptible to the negative effects of hypoxia. This study aimed to understand better if fipronil affects these GABAergic responses of Tilapia ahead to hypoxia. Oreochromis Niloticus (Nile Tilapia) were exposed for 3 and 8 h to fipronil (0.0, 0.1, and 0.5 µg.L-1 ) under normoxia (dissolved O2 > 6 mg.L-1 ) and moderate hypoxia (dissolved O2 < 2 mg.L-1 ) conditions. Briefly, hypoxia caused opposite effects on the gene transcription of the evaluated ionotropic and metabotropic GABA receptors. Unexpectedly, we obtained reduced HIF1A mRNA and brain GABA levels, mostly in the first 3 h of the experiment, for the hypoxic group compared with the normoxia one. Besides that, we also demonstrated that the insecticide fipronil impairs the brain GABAergic signaling of a hypoxia-tolerant fish during the transition from a normoxic to an acute hypoxic state. Thus, these results predict the relevant impact on the brain metabolic adaptations of fishes exposed to such stressful conditions in an aquatic environment, as well as the effects of fipronil in the GABAergic responses to hypoxia, which in turn may have ecological and physiological significance to hypoxia-tolerant fishes exposed to this insecticide.

Evaluation of Antidepressant and Anxiolytic Activity of Fruit Extract of Hylocereus undatus in Experimental Animals

Hylocereus undatus, generally known as dragon fruit was used in the present study to investigate antidepressant and anti-anxiety activity. In antidepressant activity we found that administration of 200 mg/kg and 400 mg/kg ethanolic fruit extract of Hylocereus undatus (EFEHU) and standard drug imipramine (20 mg/kg) for 21 days to respective group of animals they showed significantly reduced the immobility time in both Tail suspension test (TST) and Despair swim test (DST) in dose dependent manner as well as biochemical estimation was done. In anxiolytic activity administration of 200 mg/kg and 400 mg/kg EFEHU and standard drug diazepam (2 mg/kg) for 14 days to respective group of animals. In Elevated plus maze test (EPMT) significantly increased time spent in open arm and number of entries in open arm. The significantly increased level of 5-HT and GABA in brain of mice in dose dependent manner in both DST and EPMT. The phytochemical study of EFEHU showed the presence of alkaloids, tannins, carbohydrates, flavonoids, terpenoids, saponins, oils, phenolic compounds and qualitative examination by HPTLC technique showed that presence of quercetin and gallic acid. Therefore, the presence of such compounds in the extract may be responsible for the antidepressant and anxiolytic activity. Therefore, present study validates its antidepressant and anxiolytic activity. Further, research is required to elucidate its specific mechanism of action and isolation of responsible active principles.

HPLC and GC–MS–based metabolic profiles and in vivo anticonvulsant, sedative, and antinociceptive potentials of truffles Tirmania nivea and Tirmania pinoyi hydromethanolic extracts in mice

GC-MS and HPLC analyses of the hydromethanolic extracts of the truffles Tirmania nivea (TN) and Tirmania pinoyi (TP) revealed the presence of 18 metabolites and 11 polyphenols, respectively. In vivo, TP extract protected against subcutaneous pentylenetetrazole (scPTZ) and maximal electric shock (MES)-induced convulsions faster than TN extract. TP extract (100 and 300 mg/kg) showed 100% protection and longer duration than TN extract in the scPTZ test. Similarly, at 300 mg/kg, TP demonstrated a quicker start (75%) and longer duration of action (100%) than TN in MES test. In the scPTZ test, ED50 of TP demonstrated greater anticonvulsant efficacy than that of TN. In mice given TP and TN treatments, the brain GABA levels noticeably increased. TP (100 and 300 mg/kg) produced a notable sedative effect in open-field test, whereas TN (100 or 300 mg/kg) and TP (300 mg/kg) reduced sleep latency by 52%, 45%, and 79%, respectively. In writhing test, TN (100 or 300 mg/kg) significantly enhanced analgesic efficacy by 50 and 87%, respectively. Comparatively, in formalin test, TP and TN at a dosage of 300 mg/kg decreased the length of the licking by 34 and 59%, respectively. For the first time, this study explains the anticonvulsant, sedative, central, and peripheral analgesic activities of truffle extracts.

Ongoing oxidative stress in individuals with post-acute sequelae of COVID-19.

Coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 infection is associated with lower plasma glutathione (GSH) levels due to oxidative stress. However, plasma levels may not reflect brain GSH levels. Individuals with post-acute sequelae of COVID-19 (PASC) have a higher prevalence of cognitive fatigue, which might be related to altered brain γ-aminobutyric-acid (GABA) levels. Hence, our study aims to measure the brain GSH and GABA levels in PASC. 29 PASC participants and 24 uninfected controls were recruited for this study. Each was evaluated with detailed neuropsychiatric assessments and an edited proton MRS (Hadamard Encoding and Reconstruction of Mega-Edited Spectroscopy, HERMES) method to measure GABA and GSH concentrations in predominantly grey matter (GM) and predominantly white matter (WM) brain frontal voxels. PASC participants were 219 ± 137 days since their COVID-19 diagnosis. Nine individuals with PASC were hospitalized. Compared to controls, individuals with PASC had similar levels of GABA in both brain regions, but lower GSH and greater age-related GSH decline in the frontal GM region. The lower-than-normal frontal GM GSH level in participants with PASC suggest that they have ongoing oxidative stress in the brain, and that older individuals may be even more vulnerable to oxidative stress.

Neurotoxicity of singular and combined exposure of Oreochromis niloticus to methomyl and copper sulphate at environmentally relevant levels: Assessment of neurotransmitters, neural stress, oxidative injury and histopathological changes

Aquatic organisms are concomitantly exposed to multiple noxious chemicals that can be discharged into water bodies. We aimed to investigate the single and simultaneous sub-acute exposure to copper and methomyl on juvenile Oreochromis niloticus. Compared to the controls, the outcomes revealed that brain of methomyl-exposed fish displayed significant declines in the activities of SOD, CAT, and GST in addition to higher MDA and lower GSH levels. Methomyl induced notable declines in levels of GABA and acetylcholine esterase in brain and muscle of exposed fish. Noteworthy downregulated gene expression levels of TNF-α, HSP-70 together with upregulated c-fos were evident in brain of fish expose to either of tested compounds. Marked apoptotic changes were observed in fish brain exposed to copper and methomyl indicated by augmented immune expression of caspase-3. Conclusively, the results indicated the possible interaction between both compounds with subsequent toxic effects that differ from their single exposure.

Sensorimotor Cortex GABA Moderates the Relationship between Physical Exertion and Assessments of Effort.

Experiences of physical exertion guide our assessments of effort. While these assessments critically influence our decisions to engage in daily activities, little is known about how they are generated. We had female and male human participants exert grip force and assess how effortful these exertions felt; and used magnetic resonance spectroscopy to measure their brain GABA concentration. We found that variability in exertion (i.e., the coefficient of variation in their force exertion profile) was associated with increases in assessments of effort, making participants judge efforts as more costly. GABA levels in the sensorimotor cortex (SM1) moderated the influence of exertion variability on overassessments of effort. In individuals with higher sensorimotor GABA, exertion variability had a diminished influence on overassessments of effort. Essentially, sensorimotor GABA had a protective effect on the influence of exertion variability on inflations of effort assessment. Our findings provide a neurobiological account of how the brain's GABAergic system integrates features of physical exertion into judgments of effort, and how basic sensorimotor properties may influence higher-order judgments of effort.SIGNIFICANCE STATEMENT Feelings of effort critically shape our decisions to partake in activities of daily living. It remains unclear how the brain translates physical activity into judgments about effort (i.e., "How effortful did that activity feel?"). Using modeling of behavior and neuroimaging, we show how the nervous system uses information about physical exertion to generate assessments of effort. We found that higher variability in exertion was associated with increases in assessments of effort, making participants judge efforts as more costly. GABA, the brain's main inhibitory neurotransmitter, moderated the influence of exertion variability on overassessments of effort. These findings illustrate how low-level features of motor performance and sensorimotor neurochemistry influence higher-order cognitive processes related to feelings of effort.

Combined Treatment of Levetiracetam and Mesenchymal Stem Cells Reverses the Biochemical Aberrations in the Acute Phase of Epilepsy Induced by Pilocarpine in Rats

In spite of the enormous evolution of the novel anti-seizure medications, about one-third of epilepsy patients stay resistant to the existing therapeutic drugs. Stem cells have provoked hopeful for treating diverse neurologic diseases comprises epilepsy. The rational of this investigation was to appraise the therapeutic intervention of a combination of levetiracetam (LEV) with rodent adipose-derived mesenchymal stem cells (ADMSCs) or rodent bone marrow-derived mesenchymal stem cells (BMMSCs) in counteracting pilocarpine-induced acute epilepsy in rats. In this research, the isolation and preparation of ADMSCs and BMMSCs from male albino rats were carried out. The identification of ADMSCs and BMMSCs was performed morphologically in the culture by using the inverted microscope and by the detection of the cell surface profile by using the flow cytometry technique. The induction of acute epilepsy was achieved by intraperitoneal injection of a single dose of pilocarpine (380 mg/kg b.wt). This study was conducted on fifty six adult male albino rats which were assigned into seven equal groups (8 rats/group); Group (1): Control, Group (2): Epileptic, Group (3): Epileptic + LEV (300 mg/kg b.wt daily for 12 weeks by gastric intubation with an oral gavage), Group (4): Epileptic + ADMSCs (single dose of ADMSCs; 3 × 106 cells/rat; intravenously), Group (5): Epileptic + BMMSCs (single dose of BMMSCs 3 × 106 cells/rat; intravenously), Group (6) : Epileptic + ADMSCs + LEV and Group (7) Epileptic + BMMSCs + LEV. After the end of the experimental period (12 weeks), all rats were tested by the mean electric shock (MES) test to prove the presence of strong seizures in the epileptic group and the modulation of these seizures after treatments. Then, the rats were decapitated and the whole brain of each rat was dissected into two halves, the first half was used for the quantitative determination of GABA, glutamate, dopamine, bFGF, BDNF, IL-6 and TNF-α, while the second half was fixed in formalin saline for histological investigation. The findings of the present work demonstrated that the morphological appearance of the isolated MSCs manifests spindle-shape. The flow cytometric analysis showed that the isolated MSCs are positive for CD90 and negative for CD14 and CD45. The homing of MSCs in the brain tissue of the treated rats was verified by their staining with the fluorescent dye. The recordings of the MES indicated the presence of strong seizures in the epileptic rats which were ameliorated after treatment with LEV, ADMSCs, BMMSCs. The level of brain GABA decreased significantly in the epileptic rats, whereas the level of brain glutamate, dopamine, bFGF, BDNF, IL-6 and TNF-α increased significantly; these alterations were improved after treatment with LEV or ADMSCs or BMMSCs. The histological examination of the brain tissue of the epileptic rats showed great histopathological alterations which were amended by the different treatment options. The combined treatment of either ADMSCs or BMMSCs with LEV displayed superior advantageous effect versus the single use of each type of cell in combating the acute phase of epilepsy. In conclusion, the outcomes of the present approach disclosed that the combined treatment of either ADMSCs or BMMSCs with the antiepileptic drug LEV has synergistic effect in alleviation of the behavioral and biochemical aberrations as well as brain histological deformation during the acute phase of epilepsy.

Perceived Stress, Cortical GABA, and Functional Connectivity Correlates: A Hypothesis-Generating Preliminary Study.

Stress exposures and dysregulated responses to stress are implicated in psychiatric disorders of mood, anxiety, and cognition. Perceived stress, an individual's appraisal of experienced stress and ability for coping, relates to dysregulated functioning in resting state brain networks. Alterations in GABAergic function may underlie perceived stress-related functional dysregulation in resting state networks but this has not yet been explored. Therefore, the current study examined the association of perceived stress, via the Perceived Stress Scale (PSS), with prefrontal GABA levels and corresponding resting state functional connectivity (RSFC) alterations. Twelve women and five men, ages 35–61, participated. MR spectroscopy was used to measure brain GABA levels in the anterior cingulate cortex (ACC), left dorsolateral prefrontal cortex (DLPFC), and ventromedial prefrontal cortex (VMPFC). Resting state functional scans acquired at 3 Tesla were used to measure RSFC within and between the default mode (DMN), salience (SN), and central executive networks (CEN), hippocampus and amygdala. We observed significant negative correlations between total PSS scores and left DLPFC GABA levels (r = −0.62, p = 0.023). However, PSS scores were not significantly correlated with RSFC measures (all p > 0.148). These preliminary results support a relationship between perceived stress and GABAergic functioning in DLPFC, a core node of the CEN, an intrinsic network thought to underlie goal-directed attentional processes. Our findings extend previous work suggesting that functioning in the CEN is related to perceived stress and may inform treatment strategies to improve outcomes in stress-related conditions.

The antiepileptic potential of Vateria indica Linn in experimental animal models: Effect on brain GABA levels and molecular mechanisms

BackgroundEpilepsy is a neurodegenerative condition characterized by uncontrollable convulsions caused by a misalignment of the central nervous system's inhibitory and excitatory branches. Vateria indica is a medicinal herb with anti-inflammatory, anthelmintic, antiulcer, antitumor, and anticancer properties. ObjectivesTo investigate the antiepileptic activity of Vateria indica using maximal electrical shock (MES), pentylenetetrazole (PTZ), and isoniazid (INH) induced experimental animal models. MethodologyVateria indica bark was subjected to Soxhlet extraction using ethanol and quantitative and qualitative analysis was performed. The antiepileptic activity of Vateria indica bark extract (VIE) was investigated using different animal models in mice. GABA levels in the brain and antioxidant capacity in vitro were estimated. ResultsTreatment of mice with VIE significantly reversed the MES-induced convulsions, which was reflected by the decrease in the duration (sec) of all the phases of MES-induced convulsions, with an increment in the GABA levels. In the PTZ and INH models, pretreatment with VIE delayed the latency to clonic convulsions (p 0.001), reduced the intensity and duration of clonic convulsions, and reduced the mortality rate in the treatment groups in a dose-dependent manner. VIE intervention dose-dependently restored brain GABA levels. VIE also exhibited significant in-vitro antioxidant activity. ConclusionOverall, the findings imply that Vateria indica has substantial antiepileptic activities, mediated by positive GABAergic neurotransmission and antioxidant capabilities. To summarize, Vateria indica may provide adequate protection against epileptic seizures, suggesting that it could be used to treat petitmal and grandmal epilepsy. We plan to provide pure lead compounds derived from Vateria indica in the future in order to better understand the role it could play in the development of natural anticonvulsant drugs.

Prenatal Hypoxia Induces Cl- Cotransporters KCC2 and NKCC1 Developmental Abnormality and Disturbs the Influence of GABAA and Glycine Receptors on Fictive Breathing in a Newborn Rat.

Prenatal hypoxia is a recognised risk factor for neurodevelopmental disorders associated with both membrane proteins involved in neuron homeostasis, e.g., chloride (Cl–) cotransporters, and alterations in brain neurotransmitter systems, e.g., catecholamines, dopamine, and GABA. Our study aimed to determine whether prenatal hypoxia alters central respiratory drive by disrupting the development of Cl– cotransporters KCC2 and NKCC1. Cl– homeostasis seems critical for the strength and efficiency of inhibition mediated by GABAA and glycine receptors within the respiratory network, and we searched for alterations of GABAergic and glycinergic respiratory influences after prenatal hypoxia. We measured fictive breathing from brainstem in ex vivo preparations during pharmacological blockade of KCC2 and NKCC1 Cl– cotransporters, GABAA, and glycine receptors. We also evaluated the membrane expression of Cl– cotransporters in the brainstem by Western blot and the expression of Cl– cotransporter regulators brain-derived neurotrophic factor (BDNF) and calpain. First, pharmacological experiments showed that prenatal hypoxia altered the regulation of fictive breathing by NKCC1 and KCC2 Cl– cotransporters, GABA/GABAA, and glycin. NKCC1 inhibition decreased fictive breathing at birth in control mice while it decreased at 4 days after birth in pups exposed to prenatal hypoxia. On the other hand, inhibition of KCC2 decreased fictive breathing 4 days after birth in control mice without any change in prenatal hypoxia pups. The GABAergic system appeared to be more effective in prenatal hypoxic pups whereas the glycinergic system increased its effectiveness later. Second, we observed a decrease in the expression of the Cl– cotransporter KCC2, and a decrease with age in NKCC1, as well as an increase in the expression of BDNF and calpain after prenatal hypoxia exposure. Altogether, our data support the idea that prenatal hypoxia alters the functioning of GABAA and glycinergic systems in the respiratory network by disrupting maturation of Cl– homeostasis, thereby contributing to long-term effects by disrupting ventilation.

Effects of sex hormones on brain GABA and glutamate levels in a cis- and transgender cohort

Sex hormones affect the GABAergic and glutamatergic neurotransmitter system as demonstrated in animal studies. However, human research has mostly been correlational in nature. Here, we aimed at substantiating causal interpretations of the interaction between sex hormones and neurotransmitter function by using magnetic resonance spectroscopy imaging (MRSI) to study the effect of gender-affirming hormone treatment (GHT) in transgender individuals.Fifteen trans men (TM) with a DSM-5 diagnosis of gender dysphoria, undergoing GHT, and 15 age-matched cisgender women (CW), receiving no therapy, underwent MRSI before and after at least 12 weeks. Additionally, sex differences in neurotransmitter levels were evaluated in an independent sample of 80 cisgender men and 79 cisgender women. Mean GABA+ (combination of GABA and macromolecules) and Glx (combination of glutamate and glutamine) ratios to total creatine (GABA+/tCr, Glx/tCr) were calculated in five predefined regions-of-interest (hippocampus, insula, pallidum, putamen and thalamus).Linear mixed models analysis revealed a significant measurement by gender identity effect (pcorr. = 0.048) for GABA+/tCr ratios in the hippocampus, with the TM cohort showing decreased GABA+/tCr levels after GHT compared to CW. Moreover, analysis of covariance showed a significant sex difference in insula GABA+/tCr ratios (pcorr. = 0.049), indicating elevated GABA levels in cisgender women compared to cisgender men.Our study demonstrates GHT treatment-induced GABA+/tCr reductions in the hippocampus, indicating hormone receptor activation on GABAergic cells and testosterone-induced neuroplastic processes within the hippocampus. Moreover, elevated GABA levels in the female compared to the male insula highlight the importance of including sex as factor in future MRS studies. Data availability statementDue to data protection laws processed data is available from the authors upon reasonable request. Please contact rupert.lanzenberger@meduniwien.ac.at with any questions or requests.

Early vigabatrin augmenting GABA-ergic pathways in post-anoxic status epilepticus (VIGAB-STAT) phase IIa clinical trial study protocol

BackgroundNearly one in three unconscious cardiac arrest survivors experience post-anoxic status epilepticus (PASE). Historically, PASE has been deemed untreatable resulting in its exclusion from status epilepticus clinical trials. However, emerging reports of survivors achieving functional independence following early and aggressive treatment of PASE challenged this widespread therapeutic nihilism. In the absence of proven therapies specific to PASE, standard of care treatment leans on general management strategies for status epilepticus. Vigabatrin—an approved therapy for refractory focal-onset seizures in adults—inhibits the enzyme responsible for GABA catabolism, increases brain GABA levels and may act synergistically with anesthetic agents to abort seizures. Our central hypothesis is that early inhibition of GABA breakdown is possible in the post-cardiac arrest period and may be an effective adjunctive treatment in PASE.MethodsThis is a phase IIa, single-center, open-label, pilot clinical trial with blinded outcome assessment, of a single dose of vigabatrin in 12 consecutive PASE subjects. Subjects will receive a single loading dose of 4500 mg of vigabatrin (or dose adjusted in moderate and severe renal impairment) via enteric tube within 48 h of PASE onset. Vigabatrin levels will be monitored at 0- (baseline), 0.5-, 1-, 2-, 3-, 6-, 12-, 24-, 48-, 72- and 168-h (7 days) post-vigabatrin. Serum biomarkers of neuronal injury will be measured at 0-, 24-, 48-, 72- and 96-h post-vigabatrin. The primary feasibility endpoint is the proportion of enrolled subjects among identified eligible subjects receiving vigabatrin within 48 h of PASE onset. The primary pharmacokinetic endpoint is the measured vigabatrin level at 3 h post-administration. Descriptive statistics with rates and proportions will be obtained regarding feasibility outcomes, along with the noncompartmental method for pharmacokinetic analyses. The area under the vigabatrin concentration-time curve in plasma from zero to the time of the last quantifiable concentration (AUC0-tlqc) will be calculated to estimate dose-linear pharmacokinetics.PerspectiveVigabatrin demonstrates high potential for synergism with current standard of care therapies. Demonstration of the feasibility of vigabatrin administration and preliminary safety in PASE will pave the way for future efficacy and safety trials of this pharmacotherapeutic.Trial Registration NCT04772547.

3-O-Acetyl-11-keto-β-boswellic acid ameliorates acquired, consolidated and recognitive memory deficits through the regulation of hippocampal PPAR γ, MMP9 and MMP2 genes in dementia model

Pentacyclic Phytomolecule 3-O-Acetyl-11-keto-β-boswellic acid (AKBA) from Frankincense family has proven for the neuroprotection and recognized as an orphan drug for the treatment of cerebral edema. Nonetheless, AKBA have promising indications with Peroxisome proliferator activated receptor gamma (PPARγ) associated to cognitive function not deliberated so far. In order to substantiate the potential role of AKBA on memory function, we examine the contribution of PPARγ activation and its downstream process. Modified method of scopolamine induced dementia rats were treated with AKBA (5, 10&15 mg/kg,i.p) and Donepezil (2.5 mg/kg,i.p). Scopolamine induced short term spatial, working memory and recognition memory impairment was reversed significantly after AKBA treatment. AKBA administration diminished the Acetylcholine esterase (AchE) activity and preserved brain GABA and glutamate mediated neuronal excitability. Further, gene expression study reveals AKBA ameliorates the memory impairment via activating PPARγ and its downstream regulators, matrix metalloproteinase 2 (MMP2) and matrix metalloproteinase 9 (MMP9) genes in hippocampus. This study concludes that the treatment with AKBA can be a novel Phyto-molecule of interest for treating dementia via up-regulating hippocampus genes mediated cholinergic activation.

Jiaotaiwan increased GABA level in brain and serum, improved sleep via increasing NREM sleep and REM sleep, and its component identification

Ethnopharmacological relevanceJiaotaiwan (JTW) is good at communicating the heart and kidney. That meets the main mechanism of insomnia in traditional Chinese medicine. But the mechanism of JTW in promoting sleep is not clear. Aim of the studyTo investigate the mechanism of JTW in promoting sleep and identify the main components. Materials and methodsIn this study, we detected the levels of GABA in serum and brain via LC-MS/MS analysis and investigated the hypnotic effect of JTW and its role in promoting sleep via Sleep monitoring and vigilance state analysis. Further, the identification of the main components was carried out by using LC-MS/MS analysis. ResultsJTW could increase the GABA levels in serum, FC and BS of SDM rats. JTW reduced the amount of wakefulness, increased the time of NREM sleep and REM sleep. A total of 25 compounds were identified. ConclusionsThe current work provides valuable information on the hypnotic effects of JTW and its regulatory mechanisms in promoting sleep.

OV329, a novel highly potent γ-aminobutyric acid aminotransferase inactivator, induces pronounced anticonvulsant effects in the pentylenetetrazole seizure threshold test and in amygdala-kindled rats.

An attractive target to interfere with epileptic brain hyperexcitability is the enhancement of γ-aminobutyric acidergic (GABAergic) inhibition by inactivation of the GABA-metabolizing enzyme GABA aminotransferase (GABA-AT). GABA-AT inactivators were designed to control seizures by raising brain GABA levels. OV329, a novel drug candidate for the treatment of epilepsy and addiction, has been shown in vitro to be substantially more potent as a GABA-AT inactivator than vigabatrin, an antiseizure drug approved as an add-on therapy for adult patients with refractory complex partial seizures and monotherapy for pediatric patients with infantile spasms. Thus, we hypothesized that OV329 should produce pronounced anticonvulsant effects in two different rat seizure models. We therefore examined the effects of OV329 (5, 20, and 40mg/kg ip) on the seizure threshold of female Wistar Unilever rats, using the timed intravenous pentylenetetrazole (ivPTZ) seizure threshold model as a seizure test particularly sensitive to GABA-potentiating manipulations, and amygdala-kindled rats as a model of difficult-to-treat temporal lobe epilepsy. GABA-AT inactivation by OV329 clearly increased the threshold of both ivPTZ-induced and amygdala-kindled seizures. OV329 further showed a 30-fold greater anticonvulsant potency on ivPTZ-induced myoclonic jerks and clonic seizures compared to vigabatrin investigated previously. Notably, all rats were responsive to OV329 in both seizure models. These results reveal an anticonvulsant profile of OV329 that appears to be superior in both potency and efficacy to vigabatrin and highlight OV329 as a highly promising candidate for the treatment of seizures and pharmacoresistant epilepsies.

Editors' Note: What Is the Mechanism of Therapeutic and Adverse Effects of Gabapentinoids?

Dr. Benarroch reviewed the mechanisms underlying the therapeutic and adverse effects of gabapentinoids such as gabapentin and pregabalin. The author noted that the efficacy of these drugs for neuropathic pain, restless legs syndrome, and focal seizures is primarily attributed to their inhibition of the α2δ subunit of presynaptic voltage-gated calcium channels, which decreases neurotransmitter release. He discussed the relevance of this inhibitory action in the potential induction of cerebellar ataxia by gabapentinoids. In response, Dr. Gazulla et al. argue that GABAergic effects of these medications are also important, noting that gabapentin has been shown to increase the expression of δGABAA receptors, inhibitory tone in the cerebellum, and brain GABA concentration in patients, whereas pregabalin has been shown to increase neuronal calcium influx, which facilitates neurotransmission. They argue that gabapentinoids could actually help treat ataxia in diseases involving GABA deficiency. Responding to these comments, Dr. Benarroch notes that he did cite work finding increased expression of GABAA receptors with gabapentin use but did not cite a pilot study of pregabalin for ataxia because the review was focused on mechanisms relating to the current clinical use of gabapentinoids. He agrees that increased GABAergic transmission by these drugs may benefit disorders affecting Purkinje cells and other inhibitory neurons such as periodic alternating nystagmus but cautions that the mechanisms of ataxia are complex and that further studies are needed to confirm potential beneficial effects of gabapentinoids in cerebellar ataxia. This exchange highlights uncertainties regarding the potential therapeutic vs adverse effects of gabapentinoids in ataxia and other cerebellar disorders. Dr. Benarroch reviewed the mechanisms underlying the therapeutic and adverse effects of gabapentinoids such as gabapentin and pregabalin. The author noted that the efficacy of these drugs for neuropathic pain, restless legs syndrome, and focal seizures is primarily attributed to their inhibition of the α2δ subunit of presynaptic voltage-gated calcium channels, which decreases neurotransmitter release. He discussed the relevance of this inhibitory action in the potential induction of cerebellar ataxia by gabapentinoids. In response, Dr. Gazulla et al. argue that GABAergic effects of these medications are also important, noting that gabapentin has been shown to increase the expression of δGABAA receptors, inhibitory tone in the cerebellum, and brain GABA concentration in patients, whereas pregabalin has been shown to increase neuronal calcium influx, which facilitates neurotransmission. They argue that gabapentinoids could actually help treat ataxia in diseases involving GABA deficiency. Responding to these comments, Dr. Benarroch notes that he did cite work finding increased expression of GABAA receptors with gabapentin use but did not cite a pilot study of pregabalin for ataxia because the review was focused on mechanisms relating to the current clinical use of gabapentinoids. He agrees that increased GABAergic transmission by these drugs may benefit disorders affecting Purkinje cells and other inhibitory neurons such as periodic alternating nystagmus but cautions that the mechanisms of ataxia are complex and that further studies are needed to confirm potential beneficial effects of gabapentinoids in cerebellar ataxia. This exchange highlights uncertainties regarding the potential therapeutic vs adverse effects of gabapentinoids in ataxia and other cerebellar disorders.

Protective Effects of Anthocleista djalonensis Extracts against Pentylenetetrazole-Induced Epileptic Seizures and Neuronal Cell Loss: Role of Antioxidant Defense System.

Oxidative stress and neurodegeneration are involved in the initiation of epileptogenesis and progression of epileptic seizures. This study was aimed at investigating the anticonvulsant, antioxidant, and neuroprotective properties of active fractions isolated from Anthocleista djalonensis root barks in pentylenetetrazole mouse models of epileptic seizures. Bioactive-guided fractionation of Anthocleista djalonensis (AFAD) extracts using acute pentylenetetrazole (90 mg/kg) induced generalised tonic-clonic seizures, which afforded a potent anticonvulsant fraction (FPool 5). Further fractionation of AFAD was performed by high-performance liquid chromatography, which yielded fifteen subfractions, which were chemically characterised. In addition, AFAD was tested against convulsions or spontaneous kindled seizures induced, respectively, by acute (50 mg/kg) or subchronic (30 mg/kg) injection of pentylenetetrazole. Finally, oxidative stress markers, brain GABA content, and neuronal cell loss were evaluated in AFAD-treated pentylenetetrazole-kindled mice. Administration of AFAD significantly protected mice against acute pentylenetetrazole (90 mg/kg)-induced convulsions. In acute pentylenetetrazole (50 mg/kg)-induced hippocampal and cortical paroxysmal discharges, AFAD significantly decreased the number of crisis, the cumulative duration of crisis, and the mean duration of crisis. Additionally, AFAD significantly decreased the number of myoclonic jerks and improved the seizure score in subchronic pentylenetetrazole-induced kindled seizures. The pentylenetetrazole-induced alteration of oxidant-antioxidant balance, GABA concentration, and neuronal cells in the brain were attenuated by AFAD treatment. This study showed that AFAD protected mice against pentylenetetrazole-induced epileptic seizures possibly through the enhancement of antioxidant defence and GABAergic signalling. These events might be correlated with the amelioration of neuronal cell loss; hence, AFAD could be a potential candidate for the treatment of epilepsy.

Role of Gamma-Aminobutyric Acid in the Antiepileptic Activity of Garcinia Mangostana Standardized Extract

Epilepsy is a neurodegenerative disorder characterized by recurrent seizure activity, accompanied by convulsions and loss of consciousness. The aim of the present study was to investigate the antiepileptic activity of GML in mice using MES- and INH-induced models. Estimation of brain GABA levels and in vitro antioxidant potential was also evaluated. Treatment of mice with GML significantly reversed the MES-induced convulsions, which was reflected by the decrease in the duration (in seconds) of all the phases, with an increment in the GABA levels. In the INH model, animals treated with test drug exhibited a significant delay in the onset (in minutes) of clonic convulsions, and a decrease in the duration (in minutes) of clonic convulsions. GML had a dose dependent positive effect on GABAergic neurotransmission that was evident by a significant increase in the brain GABA levels. GML also exhibited significant free radical scavenging (DPPH•), reducing power, and hydroxyl radical scavenging activity. Put together, the data from the current study suggests that GML has significant antiepileptic potential, modulated through positive GABAergic neurotransmission and antioxidant properties.

6-Gingerol, a Major Constituent of Zingiber officinale Rhizoma, Exerts Anticonvulsant Activity in the Pentylenetetrazole-Induced Seizure Model in Larval Zebrafish.

Zingiber officinale is one of the most frequently used medicinal herbs in Asia. Using rodent seizure models, it was previously shown that Zingiber officinale hydroethanolic extract exerts antiseizure activity, but the active constituents responsible for this effect have not been determined. In this paper, we demonstrated that Zingiber officinale methanolic extract exerts anticonvulsant activity in the pentylenetetrazole (PTZ)-induced hyperlocomotion assay in larval zebrafish. Next, we isolated 6-gingerol (6-GIN)—a major constituent of Zingiber officinale rhizoma. We observed that 6-GIN exerted potent dose-dependent anticonvulsant activity in the PTZ-induced hyperlocomotion seizure assay in zebrafish, which was confirmed electroencephalographically. To obtain further insight into the molecular mechanisms of 6-GIN antiseizure activity, we assessed the concentration of two neurotransmitters in zebrafish, i.e., inhibitory γ-aminobutyric acid (GABA) and excitatory glutamic acid (GLU), and their ratio after exposure to acute PTZ dose. Here, 6-GIN decreased GLU level and reduced the GLU/GABA ratio in PTZ-treated fish compared with only PTZ-bathed fish. This activity was associated with the decrease in grin2b, but not gabra1a, grin1a, gria1a, gria2a, and gria3b expression in PTZ-treated fish. Molecular docking to the human NR2B-containing N-methyl-D-aspartate (NMDA) receptor suggests that 6-GIN might act as an inhibitor and interact with the amino terminal domain, the glutamate-binding site, as well as within the ion channel of the NR2B-containing NMDA receptor. In summary, our study reveals, for the first time, the anticonvulsant activity of 6-GIN. We suggest that this effect might at least be partially mediated by restoring the balance between GABA and GLU in the epileptic brain; however, more studies are needed to prove our hypothesis.