Hypoxia/ischemia a key player in early post stroke seizures: modulation by opioidergic and nitrergic systems

Risk factors of posthemorrhagic seizure in spontaneous intracerebral hemorrhage

Seizure is a relatively common neurological consequence after spontaneous intracerebral hemorrhage (SICH). This study aimed to investigate risk factors of early, late, and overall seizures in patients with SICH. Retrospective analysis was performed on all patients with SICH who completed two years of follow-up. The variables collected were obtained from demographic, clinical, radiographic and treatment data, in-hospital complications, and follow-up results. Univariate and multivariate analyzes were used to identify risk factors for post-hemorrhagic stroke seizure. Of 400 SICH patients recruited, 30 (7.5%) and 40 (10%) developed early and late seizures during the 2-year follow-up period, respectively. In the final result of the multivariate analysis, factors associated with the occurrence of the early seizure included lobar location of hematoma (p = 0.018), and GCS ≤ 12 on initial clinical presentation (p = 0.007). Factors associated with the occurrence of the late seizure included lobar location of hematoma (p = 0.001), volume of hematoma greater than 10 ml (p = 0.009), and midline shift on initial cranial CT (p = 0.036). Risk factors of the overall seizure after SICH included lobar location of hematoma (p < 0.001), volume of hematoma greater than 10 ml (p < 0.001), and craniotomy with evacuation of hematoma (p = 0.007). Furthermore, seizure was also associated with a poor functional outcome 2 years after the onset of SICH. Several factors associated with the appearance of post-ICH seizures were revealed. In patients with increased risk of post-SICH seizures, appropriate surveillance and management of seizures should be carried out.

Giant cell arteritis (GCA) as a risk factor for seizures: a cohort study

OBJECTIVES

The objective of this study was to assess the risk of seizures in Giant Cell Arteritis (GCA) patients in a large cohort of Israeli subjects, in comparison to matched controls.

METHODS

Patients diagnosed with GCA between 2002 and 2017 were included. Controls were matched based on sex, age, socioeconomic status, country of birth, diabetes mellitus, and hypertension in a 4:1 ratio. Patients with seizure records prior to the study period were excluded. Hazard ratios for seizures was obtained by cox regression models.

RESULTS

The study cohort was composed by 8,103 GCA patients and 32,412 matched controls. The GCA group included 5,535 women (68%), 2,644 patients born in Israel (33%), and 2,888 patients with low socioeconomic status (36%). The median age of this group was 71. During the followed cumulative person-years of 54,641 and 222,537 in the GCA and control group, respectively, 15.92 cases per 10,000 person-years was found in the GCA group, compared to 9.62 per 10,000 person-years in the controls. GCA was associated with seizures in the unadjusted (HR = 1.66, 95% CI [1.29 to 2.13]) and adjusted (HR = 1.67, 95% CI [1.3 to 2.14]) models. GCA was also associated with seizures after controlling for strokes (HR = 1.55, 95% CI [1.16 to 2.07]).

CONCLUSION

According to this study, individuals with GCA are at a higher risk of developing seizures when compared to the general population. This increased risk is independent of their predisposition for stroke. One proposed mechanism is that the GCA pro-inflammatory state may decrease the neuronal threshold for depolarization.

Beneficial effects of arthrocen on neuroinflammation and behavior like depression in stroke in a murine model

Stroke is a considerable reason for death, disability, socioeconomic loss, and depression in the world. Notably, many attempts to the reduction of the complications of poststroke injuries like depression have failed so far. In this study, we aimed to evaluate the anti-inflammatory effect of arthrocen, avocado/soybean unsaponifiables (ASU), in the poststroke injuries like depression improvement in a mice model. We examined the antidepressant-like effect of arthrocen using the forced swimming test and tail suspension test in mice subjected to stroke. Furthermore, immunohistochemistry of proinflammatory cytokines, IL-10 and TNF-α, and neural cell count were performed in the ischemic brain hippocampus of mice. Oral arthrocen reduced significantly (p < .001) the immobility time in the forced swimming test and tail suspension test in the stroke animals. Also, immunohistochemistry analysis of the hippocampus indicated significantly (p < .01) the reduction of IL-10 and TNF-α cytokines production. Nissl staining showed a significant (p < .0001) increase in the number of viable neurons in stroke mice receiving arthrocen. In conclusion, our data revealed the antidepressant activity of arthrocen in the stroke mice which may be the result of its anti-inflammatory and neuroprotective role.

Poststroke Seizure and Epilepsy: A Review of Incidence, Risk Factors, Diagnosis, Pathophysiology, and Pharmacological Therapies

Stroke is the most common cause of epilepsy and ultimately leads to a decrease in the quality of life of those affected. Ischemic and hemorrhagic strokes can both lead to poststroke epilepsy (PSE). Significant risk factors for PSE include age < 65age less than 65 years, stroke severity measured by the National Institutes of Health Stroke Scale (NIHSS), cortical involvement, and genetic factors such as TRPM6 polymorphism. The diagnosis of PSE is made by using imaging modalities, blood biomarkers, and prognostic criteria. Electroencephalography (EEG) is currently the gold standard to diagnose PSE, while new combinations of modalities are being tested to increase diagnostic specificity. This literature review uncovers a newly found mechanism for the pathology of poststroke epilepsy. The pathogenesis of early-onset and late-onset is characterized by sequelae of neuronal cellular hypoxia and disruption of the blood-brain barrier, respectively. Interleukin-6 is responsible for increasing the activity of glial cells, causing gliosis and hyperexcitability of neurons. Epinephrine, high-mobility group protein B1, downregulation of CD32, and upregulation of HLA-DR impact the pathology of poststroke epilepsy by inhibiting the normal neuronal immune response. Decreased levels of neuropeptide Y, a neurotransmitter, act through multiple unique mechanisms, such as inhibiting intracellular Ca²⁺ accumulation and acting as an anti-inflammatory, also implemented in the worsening progression of poststroke epilepsy. Additionally, CA1 hippocampal resonant neurons that increase theta oscillation are associated with poststroke epilepsy. Hypertensive small vessel disease may also have an implication in the temporal lobe epilepsy by causing occult microinfarctions. Furthermore, this review highlights the potential use of statins as primary prophylaxis against PSE, with multiple studies demonstrating a reduction in incidence using statins alone, statins in combination with antiepileptic drugs (AEDs), and statins with aspirin. The evidence strongly suggests that the second generation AEDs are a superior treatment method for PSE. Data from numerous studies demonstrate their relative lack of significant drug interactions, increased tolerability, and potential superiority in maintaining seizure-free status.

Neuroprotective effects of Lasmiditan and Sumatriptan in an experimental model of post-stroke seizure in mice: Higher effects with concurrent opioid receptors or KATP channels inhibitors

BACKGROUND

Early post-stroke seizure frequently occurs in stroke survivors within the first few days and is associated with poor functional outcomes. Therefore, efficient treatments of such complications with less adverse effects are pivotal. In this study, we investigated the possible beneficial effects of lasmiditan and sumatriptan against post-stroke seizures in mice and explored underlying mechanisms in their effects.

METHODS

Stroke was induced by double ligation of the right common carotid artery in mice. Immediately after the ligation, lasmiditan (0.1 mg/kg, intraperitoneally [i.p.]) or sumatriptan (0.03 mg/kg, i.p.) were administered. Twenty-four hours after the stroke induction, seizure susceptibility was evaluated using the pentylenetetrazole (PTZ)-induced clonic seizure model. In separate experiments, naltrexone (a non-specific opioid receptor antagonist) and glibenclamide (a K_ATP channel blocker) were administered 15 min before lasmiditan or sumatriptan injection. To evaluate the underlying signaling pathways, ELISA analysis of inflammatory cytokines (TNF-α and IL-1β) and western blot analysis of anti- and pro-apoptotic markers (Bcl-2 and Bax) were performed on mice isolated brain tissues.

RESULTS

Lasmiditan (0.1 mg/kg, i.p.) and sumatriptan (0.03 mg/kg, i.p.) remarkably decreased seizure susceptibility in stroke animals by reducing inflammatory cytokines and neuronal apoptosis. Concurrent administration of naltrexone (10 mg/kg, i.p.) or glibenclamide (0.3 mg/kg, i.p.) with lasmiditan or sumatriptan resulted in a higher neuroprotection against clonic seizures and efficiently reduced the inflammatory and apoptotic markers.

CONCLUSION

Lasmiditan and sumatriptan significantly increased post-stroke seizure thresholds in mice by suppressing inflammatory cytokines and neuronal apoptosis. Lasmiditan and sumatriptan seem to exert higher effects on seizure threshold with concurrent administration of the opioid receptors or K_ATP channels modulators.

Efficacy and safety of antiseizure medication in post-stroke epilepsy

BACKGROUND

Specific antiseizure medications (ASM) would improve the outcome in post-stroke epilepsy (PSE). The aim of this multicenter observational study was to compare different antiseizure monotherapies in PSE.

METHODS

We collected the data from 207 patients with PSE who did not change their initial antiseizure monotherapy during the period of 12 months. Efficacy was assessed by a standardized three month seizure frequency and seizure freedom. Safety was estimated by the reported side effects.

RESULTS

The mean three month seizure frequency was 1.9 ± 3.1 on eslicarbazepine, 2.1 ± 3.2 on lacosamide, 3.4 ± 4.4 on levetiracetam, 4.3 ± 6.8 on lamotrigine, and 5.1 ± 7.3 on valproate (p < 0.05 for eslicarbazepine or lacosamide in comparison with levetiracetam, lamotrigine and valproate, respectively). The lowest seizure frequency and the highest seizure freedom was observed on ASMs acting via the slow inactivation of sodium channels in comparison to other mechanisms of action (0.7 ± 0.9 vs 2.2 ± 2.4, p < 0.01). Among side effects, the most frequently reported were vertigo (25%) and tiredness (15.9%). They were similar in all investigated groups of ASM. The independent factors increasing seizure frequency that were identified in multiple regression analyses were increased size of infarction, cortical involvement, hemorrhagic transformation, neurological deficits at admission and functional impairment. Administration of ASM with the mechanism of action via the slow inactivation of sodium channels was an independent factor decreasing the seizure frequency.

CONCLUSION

Our data show that antiseizure medications acting via the slow inactivation of sodium channels, such as lacosamide and eslicarbazepine, are well tolerated and might be associated with better seizure control in PSE.

Alterations of Cerebral Perfusion and Functional Connectivity in Children With Idiopathic Generalized Epilepsy

Background

Studies have demonstrated that adults with idiopathic generalized epilepsy (IGE) have functional abnormalities; however, the neuropathological pathogenesis differs between adults and children. This study aimed to explore alterations in the cerebral blood flow (CBF) and functional connectivity (FC) to comprehensively elucidate the neuropathological mechanisms of IGE in children.

Methods

We obtained arterial spin labeling (ASL) and resting state functional magnetic resonance imaging data of 28 children with IGE and 35 matched controls. We used ASL to determine differential CBF regions in children with IGE. A seed-based whole-brain FC analysis was performed for regions with significant CBF changes. The mean CBF and FC of brain areas with significant group differences was extracted, then its correlation with clinical variables in IGE group was analyzed by using Pearson correlation analysis.

Results

Compared to controls, children with IGE had CBF abnormalities that were mainly observed in the right middle temporal gyrus, right middle occipital gyrus (MOG), right superior frontal gyrus (SFG), left inferior frontal gyrus (IFG), and triangular part of the left IFG (IFGtriang). We observed that the FC between the left IFGtriang and calcarine fissure (CAL) and that between the right MOG and bilateral CAL were decreased in children with IGE. The CBF in the right SFG was correlated with the age at IGE onset. FC in the left IFGtriang and left CAL was correlated with the IGE duration.

Conclusion

This study found that CBF and FC were altered simultaneously in the left IFGtriang and right MOG of children with IGE. The combination of CBF and FC may provide additional information and insight regarding the pathophysiology of IGE from neuronal and vascular integration perspectives.

Epilepsy-associated comorbidities among adults: A plausible therapeutic role of gut microbiota

Epilepsy is a debilitating disorder that affects about 70 million people in the world currently. Most patients with epilepsy (PWE) often reported at least one type of comorbid disorder. These may include neuropsychiatric disorders, cognitive deficits, migraine, cardiovascular dysfunction, systemic autoimmune disorders and others. Current treatment strategies against epilepsy-associated comorbidities have been based on targeting each disorder separately with either anti-seizure medications (ASMs), anti-inflammatories or anti-depressant drugs, which have often given inconsistent and ineffective results. Gut dysbiosis may be a common pathological pathway between epilepsy and its comorbid disorders, and thus may serve as a possible intervention target. Therefore, this narrative review aimed to elucidate the potential pathological and therapeutic role of the gut microbiota in adult epilepsy-associated comorbidities. This review noticed a scarcity in the current literature on studies investigating the direct role of the gut microbiota in relation to epilepsy-associated comorbidities. Nevertheless, gut dysbiosis have been implicated in both epilepsy and its associated comorbidities, with similarities seen in the imbalance of certain gut microbiota phyla (Firmicutes), but differences seen in the mechanism of action. Current gut-related interventions such as probiotics have been consistently reported across studies to provide beneficial effects in correcting gut dysbiosis and improving various disorders, independent of epilepsy. However, whether these beneficial effects may translate towards epilepsy-associated comorbidities have yet to be determined. Thus, future studies determining the therapeutic potential of gut microbiota interventions in PWE with epilepsy-associated comorbidities may effectively improve their quality of life.

Neuroprotective phosphatidylserine liposomes alleviate depressive-like behavior related to stroke through neuroinflammation attenuation in the mouse hippocampus

OBJECTIVE

To investigate the protective effect of phosphatidylserine liposomes (PSL) on post-stroke (ST) injuries such as neuroinflammation and depression in mice.

METHODS

Brain ischemia was induced via the right unilateral common carotid artery occlusion model. Then, behavioral assessments including the forced swimming test (FST) and tail suspension test (TST) were used to evaluate the antidepressant-like effect of PSL. Moreover, inflammatory cytokines changes in the hippocampus including TNF-α and IL-10 levels as well as the number of survived neurons were evaluated in ST mice using immunohistochemistry (IHC).

RESULTS

A significant reduction of the immobility time in both behavioral tests indicated the antidepressant activity of PSL. Moreover, the number of viable neurons increased significantly with PSL treatment, which was similar to control group, compared to the untreated ST group. IHC analysis of ST mice receiving PSL showed a significant reduction in TNF-α and IL-10 levels in the inflamed hippocampus of mice.

CONCLUSION

Oral PSL may improve post-stroke depression (PSD) through its anti-inflammatory properties.

Thousand and one kinase 1 protects MCAO-induced cerebral ischemic stroke in rats by decreasing apoptosis and pro-inflammatory factors

Background: Birth hypoxia causes neonatal mortality and morbidity. Hypoxia/ischemia can facilitate brain damage, causing various kinds of diseases, such as ischemic stroke. It is necessary to understand the potential underlying mechanisms of ischemic stroke. Previous studies revealed the involvement of thousand and one kinase 1 (TAOK1) in many cellular processes. Methods: Herein, middle cerebral artery (MCA) occlusion (MCAO) was performed in rats to establish ischemic stroke in the animal model, and cortical neural stem cells from rats were treated with oxygen-glucose deprivation (OGD) to induce ischemic stroke cell model. The animal model of ischemic stroke was validated by Bederson and Zea-Longa neurological deficit scores and rotarod test. TAOK1 expression was examined by quantitative real-time PCR (qRT-PCR), Western blot, and immunofluorescent staining both in vivo and in vitro. Result: Compared with sham animals, the MCAO rats showed a significant increase in the neurological scores, and obvious motor behavioral deficits. Meanwhile, there was increased apoptosis and inflammatory response in the model group. TAOK1 overexpression reversed the OGD-induced cell injury, while TAOK1 knockdown exhibited the opposing effects. On the mechanism, the OGD-induced suppression of PI3K/AKT, and activation of mitogen-activated protein kinase (MAPK) signaling pathways were abolished by TAOK1 overexpression, and aggravated by TAOK1 knockdown in vitro. Moreover, we proved that the inhibitory effect of TAOK1 on OGD-induced apoptosis was dependent on the intracellular kinase activity. Conclusion: TAOK1 protected MCAO-induced cerebral ischemic stroke by decreasing the pro-inflammatory factors and apoptosis via PI3K/AKT and MAPK signaling pathways.

Anticonvulsant Effects of Thalidomide on Pentylenetetrazole-Induced Seizure in Mice: A Role for Opioidergic and Nitrergic Transmissions

Although accumulating evidence indicates that the immunomodulatory medication thalidomide exerts anticonvulsant properties, the mechanisms underlying such effects of thalidomide are still unknown. Our previous preclinical study suggested that nitric oxide (NO) signaling may be involved in the anticonvulsant effects of thalidomide in a mouse model of clonic seizure. Additionally, several studies have shown a modulatory interaction between thalidomide and opioids in opioids intolerance, nociception and neuropathic pain. However, it is unclear whether opioidergic transmission or its interaction with NO signaling is involved in the anticonvulsant effects of thalidomide. Given the fact that both opioidergic and nitrergic transmissions have bimodal modulatory effects on seizure thresholds, in the present study we explored the involvement of these signaling pathways in the possible anticonvulsant effects of thalidomide on the pentylenetetrazole (PTZ)-induced clonic seizure in mice. Our data showed that acute administration of thalidomide (5-50 mg/kg, i.p., 30 min prior PTZ injection) dose-dependently elevated PTZ-induced clonic seizure thresholds. Acute administration of low doses (0.5-3 mg/kg, i.p., 60 min prior PTZ) of morphine exerted anticonvulsant effects (P < 0.001), whereas higher doses (15-60 mg/kg, 60 min prior PTZ) had proconvulsant effects (P < 0.01). Acute administration of a non-effective anticonvulsant dose of morphine (0.25 mg/kg) prior non-effective dose of thalidomide (5 mg/kg) exerted a robust (P < 0.01) anticonvulsant effect. Administration of a non-effective proconvulsant dose of morphine (7.5 mg/kg) prior thalidomide (5 mg/kg) didn't affect clonic seizure thresholds. Acute administration of a non-effective dose of the opioid receptor antagonist naltrexone (1 mg/kg, i.p.) significantly prevented anticonvulsant effects of thalidomide (10 mg/kg, i.p.). Pretreatment with non-effective dose of the NO precursor L-arginine (60 mg/kg, i.p.) significantly (P < 0.01) reduced the anticonvulsant effects of combined low doses of morphine (0.25 mg/kg) and thalidomide (5 mg/kg). Conversely, pretreatment with non-effective doses of either non-selective (L-NAME, 5 mg/kg, i.p.) or selective neuronal (7-nitroindazole, 30 mg/kg, i.p.) NO synthase (NOS) inhibitors significantly augmented the anticonvulsant effects of combined low doses of thalidomide and morphine, whereas the inducible NOS inhibitor aminoguanidine (100 mg/kg, i.p.) did not exert such effect. Our results indicate that opioidergic transmission and its interaction with neuronal NO signaling may contribute to the anti-seizure activity of thalidomide in the mice PTZ model of clonic seizure.

Cardiovascular effects of antiobesity drugs: are the new medicines all the same?

Waiting for a definite answer from well-designed randomized prospective clinical trials, the impact of the new antiobesity drugs -liraglutide, bupropion/naltrexone, phentermine/topiramate and lorcaserin- on cardiovascular outcomes remains uncertain. What has been learned from previous experience with older medicines is that antiobesity drugs may influence cardiovascular health not only causing weight reduction but also through direct actions on the cardiovascular system. Therefore, in the present review, we examine what is known, mainly from preclinical investigations, about the cardiovascular pharmacology of the new antiobesity medicines with the aim of highlighting potential mechanistic differences. We will show that the two active substances of the bupropion/naltrexone combination both exert beneficial and unwanted cardiovascular effects. Indeed, bupropion exerts anti-inflammatory effects but at the same time it does increase heart rate and blood pressure by potentiating catecholaminergic neurotransmission, whereas naltrexone reduces TLR4-dependent inflammation and has potential protective effects in stroke but also impairs cardiac adaption to ischemia and the beneficial opioid protective effects mediated in the endothelium. On the contrary, with the only exception of a small increase in heat rate, liraglutide only exerts favorable cardiovascular effects by protecting myocardium and brain from ischemic damage, improving heart contractility, lowering blood pressure and reducing atherogenesis. As far as the phentermine/topiramate combination is concerned, no direct cardiovascular beneficial effect is expected for phentermine (as this drug is an amphetamine derivative), whereas topiramate may exert cardioprotective and neuroprotective effects in ischemia and anti-inflammatory and antiatherogenic actions. Finally, lorcaserin, a selective 5HT_2C receptor agonist, does not seem to exert significant direct effects on the cardiovascular system though at very high concentrations this drug may also interact with other serotonin receptor subtypes and exert unwanted cardiovascular effects. In conclusion, the final effect of the new antiobesity drugs on cardiovascular outcomes will be a balance between possible (but still unproved) beneficial effects of weight loss and "mixed" weight-independent drug-specific effects. Therefore comparative studies will be required to establish which one of the new medicines is more appropriate in patients with specific cardiovascular diseases.

Methadone's effects on pentylenetetrazole-induced seizure threshold in mice: NMDA/opioid receptors and nitric oxide signaling

Methadone is a synthetic opioid used to treat opiate withdrawal and addiction. Studies have demonstrated the impact of methadone on seizure susceptibility. This study investigated the modulatory impacts of acute and subchronic (three times daily for 5 days) intraperitoneal methadone treatment on pentylenetetrazole-induced clonic seizure threshold (CST) in mice, as well as the involvement of the nitric oxide, N-methyl-d-aspartate (NMDA), and µ-opioid pathways. Acute administration of different doses of methadone (0.1, 0.3, 1, and 3 mg/kg) 45 min before CST significantly decreased the seizure threshold. Additionally, pretreatment with noneffective doses of an opioid receptor antagonist (naltrexone) and NMDA receptor antagonists (ketamine and MK-801) inhibited methadone's proconvulsive activity in the acute phase, while l-NAME (a nonspecific nitric oxide synthase (NOS) inhibitor) did not affect that activity. In the subchronic phase, methadone (3 mg/kg) demonstrated an anticonvulsive effect. Although subchronic pretreatment with noneffective doses of l-NAME and 7-nitroindazole (a specific neuronal NOS inhibitor) reversed methadone's anticonvulsive activity, aminoguanidine (a specific inducible NOS inhibitor), naltrexone, MK-801, and ketamine did not change methadone's anticonvulsive characteristic. Our results suggest that NMDA and µ-opioid receptors may be involved in methadone's proconvulsive activity in the acute phase, while methadone's anticonvulsive activity may be modulated by neuronal NOS in the subchronic phase.

Naloxone attenuates ischemic brain injury in rats through suppressing the NIK/IKKα/NF-κB and neuronal apoptotic pathways

Although naloxone has been documented to exert neuroprotection in animal model of cerebral ischemia, the mechanism is not well understood. In this present study we investigated whether naloxone affected the mitochondrial apoptotic pathway in ischemic brain injury of rats. SD rats were subjected to a permanent middle cerebral artery occlusion surgery, and received naloxone (0.5, 1, 2 mg/kg, i.v.) immediately after ischemia. Neurological deficits were evaluated 24 h after ischemia using the McGraw Stroke Index, and then the rats were killed, and the brains were collected for further analyses. We show that naloxone treatment dose-dependently decreased the infarction volume and morphological injury, improved motor behavioral function, and markedly curtailed brain edema. Furthermore, naloxone administration significantly inhibited the nuclear translocation of NF-κB p65 and decreased the levels of nuclear NF-κB p65 in the ischemic penumbra. Naloxone administration also dose-dependently increased the NF-κB inhibitory protein (IκBα) levels and attenuated phosphorylated NIK and IKKα levels in the ischemic penumbra. In addition, naloxone administration dose-dependently increased Bcl-2 levels, decreased Bax levels, stabilized the mitochondrial transmembrane potential, and inhibited cytochrome c release and caspase 3 and caspase 9 activation. These results indicate that the neuroprotective effects of naloxone against ischemic brain injury involve the inhibition of NF-κB activation via the suppression of the NIK/IKKα/IκBα pathway and the obstruction of the mitochondrial apoptotic pathway in neurons.

The Progress of Epilepsy after Stroke

BACKGROUND

Epilepsy is the second most common disease caused by multiple factors and characterized by an excessive discharge of certain neurons in the nervous system. Cerebrovascular disease, including stroke, is viewed as the most common cause of epilepsy in the elderly population, accounting for 30%-50% of the newly diagnosed cases of epilepsy cases in this age group.

METHODS

Data were collected from Web of Science, Medline, Pubmed, Scopus, through searching of these keywords: "Stroke" and "epilepsy".

RESULTS

Depending on the underlying cerebrovascular disease, 3%-30% of patients after stroke may develop post-stroke epilepsy (PSE), which has a negative effect on stroke prognosis and the quality of life.

CONCLUSION

In this review, we summarized new aspects emerging from research into PSE, including definition, epidemiology, risk factors, mechanism, accessory examination and treatment strategies for post-stroke epilepsy, which will enrich our knowledge of this disorder.

Endogenous Opiates and Behavior: 2015

This paper is the thirty-eighth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2015 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia, stress and social status, tolerance and dependence, learning and memory, eating and drinking, drug abuse and alcohol, sexual activity and hormones, pregnancy, development and endocrinology, mental illness and mood, seizures and neurologic disorders, electrical-related activity and neurophysiology, general activity and locomotion, gastrointestinal, renal and hepatic functions, cardiovascular responses, respiration and thermoregulation, and immunological responses.

Levosimendan exerts anticonvulsant properties against PTZ-induced seizures in mice through activation of nNOS/NO pathway: Role for KATP channel

AIMS

Although approving new anticonvulsants was a major breakthrough in the field of epilepsy control, so far we have met limited success in almost one third of patients suffering from epilepsy and a definite and reliable method is yet to be found. Levosimendan demonstrated neuroprotective effects and reduced mortality in conditions in which seizure can be an etiology of death; however, the underlying neuroprotective mechanisms of levosimendan still eludes us. In the light of evidence suggesting levosimendan can be a KATP channel opener and nitrergic pathway activator, levosimendan may exert antiseizure effects through KATP channels and nitrergic pathway.

MAIN METHODS

In this study, the effects of levosimendan on seizure susceptibility was studied by PTZ-induced seizures model in mice.

KEY FINDINGS

Administration of a single effective dose of levosimendan significantly increased seizures threshold and the nitrite level in the hippocampus and temporal cortex. Pretreatment with noneffective doses of glibenclamide (a KATP channel blocker) and L-NAME (a non-selective NOS inhibitor) neutralize the anticonvulsant and nitrite elevating effects of levosimendan. While 7-NI (a neural NOS inhibitor) blocked the anticonvulsant effect of levosimendan, Aminoguanidine (an inducible NOS inhibitor) failed to affect the anticonvulsant effects of levosimendan. Cromakalim (a KATP channel opener) or l-arginine (an NO precursor) augmented the anticonvulsant effects of a subeffective dose of levosimendan. Moreover, co-administration of noneffective doses of Glibenclamide and L-NAME demonstrated a synergistic effect in blocking the anticonvulsant effects of levosimendan.

SIGNIFICANCE

Levosimendan has anticonvulsant effects possibly via KATP/nNOS/NO pathway activation in the hippocampus and temporal cortex.

Predictors of seizures in patients with posterior reversible encephalopathy syndrome

PURPOSE

Although seizures are common in patients with posterior reversible encephalopathy syndrome (PRES), epilepsy is rare. Our objective was to identify predictors and impact of seizures in patients with PRES.

METHODS

A retrospective review of the clinical and radiological parameters of all patients diagnosed with PRES from 2007 to 2014 was performed. Patients were divided into two groups based on the occurrence of PRES-related seizures at presentation or during their hospital course. Univariate and multivariate analyses were performed to determine factors associated with the occurrence of PRES-related seizures.

RESULTS

Of 100 patients, 70% experienced at least one seizure from PRES. On univariate analysis, the factors associated with seizures were the following: high Charlson comorbidity index (4.16±2.89 vs. 2.87±2.20, p=0.03), systemic malignancy (41.4% vs. 16.7%, p=0.02), occipital lobe involvement (97.1% vs. 83.3%, p=0.02), more lobes involved (4.6±1.48 vs. 3.9±1.32, p=0.03) but less likely in patients with visual disturbances (15.7% vs. 46.7%, p=0.005), and facial droop (12.9% vs. 16.7%, p=0.002). On multivariate analysis, only occipital lobe involvement was significantly (odds ratio: 9.63, 95% CI: 1.45-64.10, p=0.02) associated with the occurrence of PRES-related seizures. Despite the occurrence of seizures, they were less likely to require a nursing home placement upon hospital discharge (odds ratio: 0.17, 95% CI: 0.03-0.91, p=0.04).

CONCLUSION

We conclude that seizures are common in patients with occipital lobe involvement from PRES.

Low-Dimensional Models of "Neuro-Glio-Vascular Unit" for Describing Neural Dynamics under Normal and Energy-Starved Conditions

The motivation of developing simple minimal models for neuro-glio-vascular (NGV) system arises from a recent modeling study elucidating the bidirectional information flow within the NGV system having 89 dynamic equations (1). While this was one of the first attempts at formulating a comprehensive model for neuro-glio-vascular system, it poses severe restrictions in scaling up to network levels. On the contrary, low-­dimensional models are convenient devices in simulating large networks that also provide an intuitive understanding of the complex interactions occurring within the NGV system. The key idea underlying the proposed models is to describe the glio-vascular system as a lumped system, which takes neural firing rate as input and returns an “energy” variable (analogous to ATP) as output. To this end, we present two models: biophysical neuro-energy (Model 1 with five variables), comprising K_ATP channel activity governed by neuronal ATP dynamics, and the dynamic threshold (Model 2 with three variables), depicting the dependence of neural firing threshold on the ATP dynamics. Both the models show different firing regimes, such as continuous spiking, phasic, and tonic bursting depending on the ATP production coefficient, ɛ_p, and external current. We then demonstrate that in a network comprising such energy-dependent neuron units, ɛ_p could modulate the local field potential (LFP) frequency and amplitude. Interestingly, low-frequency LFP dominates under low ɛ_p conditions, which is thought to be reminiscent of seizure-like activity observed in epilepsy. The proposed “neuron-energy” unit may be implemented in building models of NGV networks to simulate data obtained from multimodal neuroimaging systems, such as functional near infrared spectroscopy coupled to electroencephalogram and functional magnetic resonance imaging coupled to electroencephalogram. Such models could also provide a theoretical basis for devising optimal neurorehabilitation strategies, such as non-invasive brain stimulation for stroke patients.

Effects and Mechanism of Action of Inducible Nitric Oxide Synthase on Apoptosis in a Rat Model of Cerebral Ischemia-Reperfusion Injury

Inducible nitric oxide synthase (iNOS) is a key enzyme in regulating nitric oxide (NO) synthesis under stress, and NO has varying ability to regulate apoptosis. The aim of this study was to investigate the effects and possible mechanism of action of iNOS on neuronal apoptosis in a rat model of cerebral focal ischemia and reperfusion injury in rats treated with S-methylisothiourea sulfate (SMT), a high-selective inhibitor of iNOS. Seventy-two male Sprague-Dawley (SD) rats were randomly divided into three groups: the sham, middle cerebral artery occlusion (MCAO) + vehicle, and MCAO + SMT groups. Neurobehavioral deficits, infarct zone size, and cortical neuron morphology were evaluated through the modified Garcia scores, 2,3,5-triphenyltetrazolium chloride (TTC), and Nissl staining, respectively. Brain tissues and serum samples were collected at 72 hr post-reperfusion for immunohistochemical analysis, Western blotting, Terminal deoxynucleotidyl transferase-mediated dUTP-biotin Nick End Labeling assay (TUNEL) staining, and enzyme assays. The study found that inhibition of iNOS significantly attenuated the severity of the pathological changes observed as a result of ischemia-reperfusion injury: SMT reduced NO content as well as total nitric oxide synthase (tNOS) and iNOS activities in both ischemic cerebral hemisphere and serum, improved neurobehavioral scores, reduced mortality, reduced the infarct volume ratio, attenuated morphological changes in cortical neurons, decreased the rate of apoptosis (TUNEL and caspase-3-positive), and increased phospho (p)-AKT expression in ischemic penumbra. These results suggested that inhibition of iNOS might reduce the severity of ischemia-reperfusion injury by inhibiting neuronal apoptosis via maintaining p-AKT activity.

Early-Onset Convulsive Seizures Induced by Brain Hypoxia-Ischemia in Aging Mice: Effects of Anticonvulsive Treatments

Aging is associated with an increased risk of seizures/epilepsy. Stroke (ischemic or hemorrhagic) and cardiac arrest related brain injury are two major causative factors for seizure development in this patient population. With either etiology, seizures are a poor prognostic factor. In spite of this, the underlying pathophysiology of seizure development is not well understood. In addition, a standardized treatment regimen with anticonvulsants and outcome assessments following treatment has yet to be established for these post-ischemic seizures. Previous studies have modeled post-ischemic seizures in adult rodents, but similar studies in aging/aged animals, a group that mirrors a higher risk elderly population, remain sparse. Our study therefore aimed to investigate early-onset seizures in aging animals using a hypoxia-ischemia (HI) model. Male C57 black mice 18-20-month-old underwent a unilateral occlusion of the common carotid artery followed by a systemic hypoxic episode (8% O2 for 30 min). Early-onset seizures were detected using combined behavioral and electroencephalographic (EEG) monitoring. Brain injury was assessed histologically at different times post HI. Convulsive seizures were observed in 65% of aging mice post-HI but not in control aging mice following either sham surgery or hypoxia alone. These seizures typically occurred within hours of HI and behaviorally consisted of jumping, fast running, barrel-rolling, and/or falling (loss of the righting reflex) with limb spasms. No evident discharges during any convulsive seizures were seen on cortical-hippocampal EEG recordings. Seizure development was closely associated with acute mortality and severe brain injury on brain histological analysis. Intra-peritoneal injections of lorazepam and fosphenytoin suppressed seizures and improved survival but only when applied prior to seizure onset and not after. These findings together suggest that seizures are a major contributing factor to acute mortality in aging mice following severe brain ischemia and that early anticonvulsive treatment may prevent seizure genesis and improve overall outcomes.