Modeling early-onset post-ischemic seizures in aging mice

The novel ROCK2 selective inhibitor NRL-1049 preserves the blood-brain barrier after acute injury

Endothelial blood-brain barrier (BBB) dysfunction is critical in the pathophysiology of brain injury. Rho-associated protein kinase (ROCK) activation disrupts BBB integrity in the injured brain. We aimed to test the efficacy of a novel ROCK2 inhibitor in preserving the BBB after acute brain injury. We characterized the molecular structure and pharmacodynamic and pharmacokinetic properties of a novel selective ROCK2 inhibitor, NRL-1049, and its first metabolite, 1-hydroxy-NRL-1049 (referred to as NRL-2017 hereon) and tested the efficacy of NRL-1049 on the BBB integrity in rodent models of acute brain injury. Our data show that NRL-1049 and NRL-2017 both inhibit ROCK activity and are 44-fold and 17-fold more selective towards ROCK2 than ROCK1, respectively. When tested in a mouse model of cortical cryoinjury, NRL-1049 significantly attenuated the increase in water content. Interestingly, 60% of the mice in the vehicle arm developed seizures within 2 hours after cryoinjury versus none in the NRL-1049 arm. In spontaneously hypertensive rats, NRL-1049 attenuated the dramatic surge in Evans Blue extravasation compared with the vehicle arm after transient middle cerebral artery occlusion. Hemorrhagic transformation was also reduced. We show that NRL-1049, a selective ROCK2 inhibitor, is a promising drug candidate to preserve the BBB after brain injury.

A companion to the preclinical common data elements for phenotyping seizures and epilepsy in rodent models. A report of the TASK3-WG1C: Phenotyping working group of the ILAE/AES joint translational task force

Epilepsy is a heterogeneous disorder characterized by spontaneous seizures and behavioral comorbidities. The underlying mechanisms of seizures and epilepsy across various syndromes lead to diverse clinical presentation and features. Similarly, animal models of epilepsy arise from numerous dissimilar inciting events. Preclinical seizure and epilepsy models can be evoked through many different protocols, leaving the phenotypic reporting subject to diverse interpretations. Serendipity can also play an outsized role in uncovering novel drivers of seizures or epilepsy, with some investigators even stumbling into epilepsy research because of a new genetic cross or unintentional drug effect. The heightened emphasis on rigor and reproducibility in preclinical research, including that which is conducted for epilepsy, underscores the need for standardized phenotyping strategies. To address this goal as part of the TASK3-WG1C Working Group of the International League Against Epilepsy (ILAE)/American Epilepsy Society (AES) Joint Translational Task Force, we developed a case report form (CRF) to describe the common data elements (CDEs) necessary for the phenotyping of seizure-like behaviors in rodents. This companion manuscript describes the use of the proposed CDEs and CRF for the visual, behavioral phenotyping of seizure-like behaviors. These phenotyping CDEs and accompanying CRF can be used in parallel with video-electroencephalography (EEG) studies or as a first visual screen to determine whether a model manifests seizure-like behaviors before utilizing more specialized diagnostic tests, like video-EEG. Systematic logging of seizure-like behaviors may help identify models that could benefit from more specialized diagnostic tests to determine whether these are epileptic seizures, such as video-EEG.

Can Old Animals Reveal New Targets? The Aging and Degenerating Brain as a New Precision Medicine Opportunity for Epilepsy

Older people represent the fastest growing group with epilepsy diagnosis. For example, cerebrovascular disease may underlie roughly 30-50% of epilepsy in older adults and seizures are also an underrecognized comorbidity of Alzheimer's disease (AD). As a result, up to 10% of nursing home residents may take antiseizure medicines (ASMs). Despite the greater incidence of epilepsy in older individuals and increased risk of comorbid seizures in people with AD, aged animals with seizures are strikingly underrepresented in epilepsy drug discovery practice. Increased integration of aged animals into preclinical epilepsy drug discovery could better inform the potential tolerability and pharmacokinetic interactions in aged individuals as the global population becomes increasingly older. Quite simply, the ASMs on the market today were brought forth based on efficacy in young adult, neurologically intact rodents; preclinical information concerning the efficacy and safety of promising ASMs is not routinely evaluated in aged animals. Integrating aged animals more often into basic epilepsy research may also uncover novel treatments for hyperexcitability. For example, cannabidiol and fenfluramine demonstrated clear efficacy in syndrome-specific pediatric models that led to a paradigm shift in the perceived value of pediatric models for ASM discovery practice; aged rodents with seizures or rodents with aging-related neuropathology represent an untapped resource that could similarly change epilepsy drug discovery. This review, therefore, summarizes how aged rodent models have thus far been used for epilepsy research, what studies have been conducted to assess ASM efficacy in aged rodent seizure and epilepsy models, and lastly to identify remaining gaps to engage aging-related neurological disease models for ASM discovery, which may simultaneously reveal novel mechanisms associated with epilepsy.

Epileptiform activity in mouse hippocampal slices induced by moderate changes in extracellular Mg2+, Ca2+, and K. BMC Neurosci 2021;22:46. [PMID: 34301200 PMCID: PMC8305515 DOI: 10.1186/s12868-021-00650-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

BACKGROUND

Rodent brain slices-particularly hippocampal slices-are widely used in experimental investigations of epileptiform activity. Oxygenated artificial cerebrospinal fluid (ACSF) is used to maintain slices in vitro. Physiological or standard ACSF containing 3-3.5 mM K⁺, 1-2 mM Mg²⁺, and 1-3 mM Ca²⁺ generally does not induce population epileptiform activity, which can be induced by ACSF with high K⁺ (8-10 mM), low Mg²⁺, or low Ca²⁺ alone or in combination. While low-Mg²⁺ ACSF without intentionally added Mg salt but with contaminating Mg²⁺ (≤ 50-80 µM) from other salts can induce robust epileptiform activity in slices, it is unclear whether such epileptiform activity can be achieved using ACSF with moderately decreased Mg²⁺. To explore this issue, we examined the effects of moderately modified (m)ACSF with 0.8 mM Mg²⁺, 1.3 mM Ca²⁺, and 5.7 mM K⁺ on induction of epileptiform discharges in mouse hippocampal slices.

RESULTS

Hippocampal slices were prepared from young (21-28 days old), middle-aged (13-14 months old), and aged (24-26 months old) C57/BL6 mice. Conventional thin (0.4 mm) and thick (0.6 mm) slices were obtained using a vibratome and pretreated with mACSF at 35-36 °C for 1 h prior to recordings. During perfusion with mACSF at 35-36 °C, spontaneous or self-sustained epileptiform field potentials following high-frequency stimulation were frequently recorded in slices pretreated with mACSF but not in those without the pretreatment. Seizure-like ictal discharges were more common in thick slices than in thin slices.

CONCLUSIONS

Prolonged exposure to mACSF by pretreatment and subsequent perfusion can induce epileptiform field potentials in mouse hippocampal slices.

Stroke-Onset Seizures During Midbrain Infarction in a Patient With Top of the Basilar Syndrome

Risk factors for early-onset seizures in acute ischemic stroke include anterior circulation stroke, infarction of the cerebral cortex, large infarct size, and ischemic-to-hemorrhagic transformation. We define stroke-onset seizures as seizures occurring within 2 hours of stroke onset. A 64-year-old woman presented with top of the basilar artery syndrome-thalamic infarction occurred first and midbrain infarction 12 days later. She manifested stroke-onset seizures during midbrain infarction, which was heralded by stupor. Within 2 hours of the onset of stupor, she had a clonic seizure of the lower extremities, electroencephalography (EEG) revealed nonconvulsive status epilepticus, and an episode of convulsive movements of all extremities was recorded on video and on EEG. Continuous EEG recording showed epileptiform discharges that would appear, disappear, and reappear over a 3-week period. It took 3 weeks and 4 antiepileptic drugs to fully suppress cortical hyperexcitability, perhaps because injury to some midbrain structures resulted in global lowering of the seizure threshold. The most important risk factor for stroke-onset seizures appears to be posterior circulation stroke, particularly brainstem infarction. The difference in risk profile between stroke-onset seizures and other forms of early-onset seizures suggest that their pathophysiology is not exactly the same. Focusing some of the research spotlight on stroke-onset seizures can help us better understand their unique clinical, electrographic, radiologic, and pathophysiologic features.

Electrographic Features of Spontaneous Recurrent Seizures in a Mouse Model of Extended Hippocampal Kindling

Epilepsy is a chronic neurological disorder characterized by spontaneous recurrent seizures (SRS) and comorbidities. Kindling through repetitive brief stimulation of a limbic structure is a commonly used model of temporal lobe epilepsy. Particularly, extended kindling over a period up to a few months can induce SRS, which may simulate slowly evolving epileptogenesis of temporal lobe epilepsy. Currently, electroencephalographic (EEG) features of SRS in rodent models of extended kindling remain to be detailed. We explored this using a mouse model of extended hippocampal kindling. Intracranial EEG recordings were made from the kindled hippocampus and unstimulated hippocampal, neocortical, piriform, entorhinal, or thalamic area in individual mice. Spontaneous EEG discharges with concurrent low-voltage fast onsets were observed from the two corresponding areas in nearly all SRS detected, irrespective of associated motor seizures. Examined in brain slices, epileptiform discharges were induced by alkaline artificial cerebrospinal fluid in the hippocampal CA3, piriform and entorhinal cortical areas of extended kindled mice but not control mice. Together, these in vivo and in vitro observations suggest that the epileptic activity involving a macroscopic network may generate concurrent discharges in forebrain areas and initiate SRS in hippocampally kindled mice.

Seizures in patients with respiratory disease - a retrospective single center study

OBJECTIVE

Seizures are a neurological condition commonly experienced during the follow-up period after systemic or metabolic disorders. The aim of the present study was to determine the etiological factors of seizures in patients at a tertiary care chest clinic.

METHODS

We reviewed all neurology consultations that were requested due to seizures in inpatient clinics in a tertiary care hospital specializing in respiratory disorders between January 2011 and January 2018 were retrospectively reviewed.

RESULTS

The present study included 705 of 2793 (25.2%) patients who requested consultations for seizures during the study period. The mean age of the sample was 64.05±17.19 years. Of the 705 patients, 307 (43.5%) had a previous history of epilepsy (Group I) and 398 (56.5%) had a first-time seizure and were considered to have symptomatic seizures (Group II). Multiple factors played roles in the development of seizures in 54.8% of the patients. In most patients, metabolic causes, systemic infections, and drug use were identified and an intracranial metastatic mass lesion was the major cause in patients with lung cancer. Rates of hypoxemia and respiratory acidosis were significantly higher in patients with symptomatic seizures (Group II) than in patients with primary epilepsy (Group I).

CONCLUSIONS

Blood gas changes such as hypoxemia and respiratory acidosis were among the factors statistically associated with the development of symptomatic seizures in patients with respiratory diseases. Additionally, hypoxemia, hypercapnia, and respiratory acidosis were correlated with mortality in patients hospitalized for respiratory system diseases who requested consultations for seizures.

The need to incorporate aged animals into the preclinical modeling of neurological conditions

Neurological conditions such as traumatic brain injury, stroke, Parkinson's disease, epilepsy, multiple sclerosis, and Alzheimer's disease are serious clinical problems that affect millions of people worldwide. The majority of clinical trials for these common conditions have failed, and there is a critical need to understand why treatments in preclinical animal models do not translate to patients. Many patients with these conditions are middle-aged or older, however, the majority of preclinical studies have used only young-adult animals. Considering that aging involves biological changes that are relevant to the pathobiology of neurological diseases, the lack of aged subjects in preclinical research could contribute to translational failures. This paper details how aging affects biological processes involved in neurological conditions, and reviews aging research in the context of traumatic brain injury, stroke, Parkinson's disease, epilepsy, multiple sclerosis, and Alzheimer's disease. We conclude that aging is an important, but often overlooked, factor that influences biology and outcomes in neurological conditions, and provide suggestions to improve our understanding and treatment of these diseases in aged patients.

Role of microRNA-155 in modifying neuroinflammation and γ-aminobutyric acid transporters in specific central regions after post-ischaemic seizures

In the central nervous system, interleukin (IL)‐1β, IL‐6 and tumour necrosis factor (TNF)‐α have a regulatory role in pathophysiological processes of epilepsy. In addition, γ‐aminobutyric acid (GABA) transporter type 1 and type 3 (GAT‐1 and GAT‐3) modulate the levels of extracellular GABA in involvement in the neuroinflammation on epileptogenesis. Thus, in the current report we examined the effects of inhibiting microRNA‐155 (miR‐155) on the levels of IL‐1β, IL‐6 and TNF‐α, and expression of GAT‐1 and GAT‐3 in the parietal cortex, hippocampus and amygdala of rats with nonconvulsive seizure (NCS) following cerebral ischaemia. Real time RT‐PCR, ELISA and Western blot analysis were used to examine the miR‐155, proinflammatory cytokines (PICs) and GAT‐1/GAT‐3 respectively. With induction of NCS, the levels of miR‐155 were amplified in the parietal cortex, hippocampus and amygdala and this was accompanied with increases of IL‐1β, IL‐6 and TNF‐α. In those central areas, expression of GAT‐1 and GAT‐3 was upregulated; and GABA was reduced in rats following NCS. Intracerebroventricular infusion of miR‐155 inhibitor attenuated the elevation of PICs, amplification of GAT‐1 and GAT‐3 and impairment of GABA. Furthermore, inhibition of miR‐155 decreased the number of NCS events following cerebral ischaemia. Inhibition of miR‐155 further improved post‐ischaemia‐evoked NCS by altering neuroinflammation‐GABA signal pathways in the parietal cortex, hippocampus and amygdala. Results suggest the role of miR‐155 in regulating post‐ischaemic seizures via PICs‐GABA mechanisms.

Contributions of the Hippocampal CA3 Circuitry to Acute Seizures and Hyperexcitability Responses in Mouse Models of Brain Ischemia

The hippocampal circuitry is widely recognized as susceptible to ischemic injury and seizure generation. However, hippocampal contribution to acute non-convulsive seizures (NCS) in models involving middle cerebral artery occlusion (MCAO) remains to be determined. To address this, we occluded the middle cerebral artery in adult C57 black mice and monitored electroencephalographic (EEG) discharges from hippocampal and neocortical areas. Electrographic discharges in the absence of convulsive motor behaviors were observed within 90 min following occlusion of the middle cerebral artery. Hippocampal discharges were more robust than corresponding cortical discharges in all seizure events examined, and hippocampal discharges alone or with minimal cortical involvement were also observed in some seizure events. Seizure development was associated with ipsilateral hippocampal injuries as determined by subsequent histological examinations. We also introduced hypoxia-hypoglycemia episodes in mouse brain slices and examined regional hyperexcitable responses ex vivo. Extracellular recordings showed that the hippocampal CA3 region had a greater propensity for exhibiting single/multiunit activities or epileptiform field potentials following hypoxic-hypoglycemic (HH) episodes compared to the CA1, dentate gyrus, entorhinal cortical (EC) or neocortical regions. Whole-cell recordings revealed that CA3 pyramidal neurons exhibited excessive excitatory postsynaptic currents, attenuated inhibitory postsynaptic currents and intermittent or repetitive spikes in response to HH challenge. Together, these observations suggest that hippocampal discharges, possibly as a result of CA3 circuitry hyperexcitability, are a major component of acute NCS in a mouse model of MCAO.

Mild hypothermia inhibits the Notch 3 and Notch 4 activation and seizure after stroke in the rat model

Ischemic brain injury is an important cause for seizure. Mild hypothermia of the brain or the whole body is an effective way to remit the post-stroke seizure. Our previous study revealed an implication of Notch 1 and 2 in the post-stroke seizure. This study further investigated the involvement of Notch 3 and 4 in post-stroke seizure and the effect of mild hypothermia on these two factors. A global cerebral ischemia (GCI) model was conducted in Sprague Dawley rats. Seizure activity was evaluated by the frequency of seizure attacks, seizure severity scores, and seizure discharges. Seizures were frequently occurred in the first and the second 24 h after GCI, however active whole-body cooling (mild hypothermia) and DAPT (Notch inhibitor) injection into the hippocampus, alone or in combination, alleviated seizure activity after GCI. Immunohistochemistry and Western blot assays revealed the up-regulation of Notch intracellular domain (NICD) 3 and 4 in the cerebral cortex and hippocampus following GCI, but mild hypothermia and DAPT inhibited the up-regulation of NICD 3 and 4. NF-κB, PPARα, PPARγ, cyclin D1, Sox2 and Pax6 are associated with the pathogenesis of diverse type of seizures. GCI induced NF-κB, cyclin D1, and Pax6 activity, but suppressed PPARγ. These effects of GCI were abolished by both mild hypothermia and DAPT treatment. This indicated the implication of Notch signaling in the effects of GCI. Collectively, mild hypothermia inhibits Notch 3 and Notch 4 activation and seizure after stroke in the rat model. This study adds to the further understanding of the pathogenesis of post-stroke seizures and the protective mechanism of mild hypothermia.

mTOR is involved in stroke-induced seizures and the anti-seizure effect of mild hypothermia

Stroke is considered an underlying etiology of the development of seizures. Stroke leads to glucose and oxygen deficiency in neurons, resulting in brain dysfunction and injury. Mild hypothermia is a therapeutic strategy to inhibit stroke‑induced seizures, which may be associated with the regulation of energy metabolism of the brain. Mammalian target of rapamycin (mTOR) signaling and solute carrier family 2, facilitated glucose transporter member (GLUT)‑1 are critical for energy metabolism. Furthermore, mTOR overactivation and GLUT‑1 deficiency are associated with genetically acquired seizures. It has been hypothesized that mTOR and GLUT‑1 may additionally be involved in seizures elicited by stroke. The present study established global cerebral ischemia (GCI) models of rats. Convulsive seizure behaviors frequently occurred during the first and the second days following GCI, which were accompanied with seizure discharge reflected in the EEG monitor. Expression of phosphor (p)‑mTOR and GLUT‑1 were upregulated in the cerebral cortex and hippocampus, as evidenced by immunohistochemistry and western blot analyses. Mild hypothermia and/or rapamycin (mTOR inhibitor) treatments reduced the number of epileptic attacks, seizure severity scores and seizure discharges, thereby alleviating seizures induced by GCI. Mild hypothermia and/or rapamycin treatments reduced phosphorylation levels of mTOR and the downstream effecter p70S6 in neurons, and the amount of GLUT‑1 in the cytomembrane of neurons. The present study revealed that mTOR is involved in stroke‑induced seizures and the anti‑seizure effect of mild hypothermia. The role of GLUT‑1 in stroke‑elicited seizures appears to be different from the role in seizures induced by other reasons. Further studies are necessary in order to elucidate the exact function of GLUT-1 in stroke‑elicited seizures.

Susceptibility to hippocampal kindling seizures is increased in aging C57 black mice

The incidence of seizures increases with old age. Stroke, dementia and brain tumors are recognized risk factors for new-onset seizures in the aging populations and the incidence of these conditions also increased with age. Whether aging is associated with higher seizure susceptibility in the absence of the above pathologies remains unclear. We used classic kindling to explore this issue as the kindling model is highly reproducible and allows close monitoring of electrographic and motor seizure activities in individual animals. We kindled male young and aging mice (C57BL/6 strain, 2-3 and 18-22 months of age) via daily hippocampal CA3 stimulation and monitored seizure activity via video and electroencephalographic recordings. The aging mice needed fewer stimuli to evoke stage-5 motor seizures and exhibited longer hippocampal afterdischarges and more frequent hippocampal spikes relative to the young mice, but afterdischarge thresholds and cumulative afterdischarge durations to stage 5 motor seizures were not different between the two age groups. While hippocampal injury and structural alterations at cellular and micro-circuitry levels remain to be examined in the kindled mice, our present observations suggest that susceptibility to hippocampal CA3 kindling seizures is increased with aging in male C57 black mice.

Synergistic effect of mild hypothermia and the Notch inhibitor DAPT against post stroke seizures

Seizure is a serious complication of stroke, indicating poor prognosis. Notch signaling is associated with neuronal activity. Inhibition of Notch signaling suppresses seizure activity induced by kainic acid. The present study investigated the effect of the Notch inhibitor, DAPT, alone or in combination with mild hypothermia, on post-stroke seizures. A global cerebral ischemia (GCI) model was performed in Sprague Dawley (SD) male rats. Seizure activity was evaluated by the frequency of seizure attacks, seizure severity scores, and seizure discharges. Without any intervention, seizures occurred intensively between 24h and 48h following GCI. Seizure activity was confirmed using EEG monitoring. The expression of Notch intracellular domains (NICD) 1 and 2 were up-regulated in the cerebral cortex and hippocampus following GCI. DAPT was injected into the hippocampus of the rats to inhibit local Notch signaling. Active whole-body cooling was performed to maintain the core temperatures of rats at 33.5°C (mild hypothermia). Mild hypothermia and DAPT synergistically inhibited NICD 1 and 2 up-regulation, and post-stroke seizures. GCI augmented excitatory synaptic neurotransmission by up-regulating glutamate receptor subunits (GluN2A, GluA1) and the cotransporter, NKCC1, but attenuated inhibitory synaptic neurotransmission by down-regulating gamma amino acid, butyric acid (GABA), and the cotransporter, KCC2. DAPT treatment normalized the homeostasis of excitatory and inhibitory synaptic neurotransmission, suggesting that aberrant activation of Notch signaling is involved in post-stroke seizures. The present study adds to the further understanding of the pathogenesis of post-stroke seizures and the improvement of the treatment provided with hypothermia.

Continuous Monitoring via Tethered Electroencephalography of Spontaneous Recurrent Seizures in Mice

We describe here a simple, cost-effective apparatus for continuous tethered electroencephalographic (EEG) monitoring of spontaneous recurrent seizures in mice. We used a small, low torque slip ring as an EEG commutator, mounted the slip ring onto a standard mouse cage and connected rotary wires of the slip ring directly to animal's implanted headset. Modifications were made in the cage to allow for a convenient installation of the slip ring and accommodation of animal ambient activity. We tested the apparatus for hippocampal EEG recordings in adult C57 black mice. Spontaneous recurrent seizures were induced using extended hippocampal kindling (≥95 daily stimulation). Control animals underwent similar hippocampal electrode implantations but no stimulations were given. Combined EEG and webcam monitoring were performed for 24 h daily for 5–9 consecutive days. During the monitoring periods, the animals moved and accessed water and food freely and showed no apparent restriction in ambient cage activities. Ictal-like hippocampal EEG discharges and concurrent convulsive behaviors that are characteristics of spontaneous recurrent seizures were reliably recorded in a majority of the monitoring experiments in extendedly kindled but not in control animals. However, 1–2 rotary wires were disconnected from the implanted headset in some animals after continuous recordings for ≥5 days. The key features and main limitations of our recording apparatus are discussed.

Association between seizures after ischemic stroke and stroke outcome: A systematic review and meta-analysis

A systematic review and meta-analysis were performed to investigate a potential association between post-ischemic stroke seizures (PISS) and subsequent ischemic stroke (IS) outcome.A systematic search of two electronic databases (Medline and Embase) was conducted to identify studies that explored an association between PISS and IS outcome. The primary and secondary IS outcomes of interest were mortality and disability, respectively, with the latter defined as a score of 3 to 5 on the modified Rankin Scale.A total of 15 studies that were published between 1998 and 2015 with 926,492 participants were examined. The overall mortality rates for the patients with and without PISS were 34% (95% confidence interval [CI], 27-42%) and 18% (95% CI, 12-23%), respectively. The pooled relative ratio (RR) of mortality for the patients with PISS was 1.97 (95% CI, 1.48-2.61; I = 88.6%). The overall prevalence rates of disability in the patients with and without PISS were 60% (95% CI, 32-87%) and 41% (95% CI, 25-57%), respectively. Finally, the pooled RR of disability for the patients with PISS was 1.64 (95% CI, 1.32-2.02; I = 66.1%).PISS are significantly associated with higher risks of both mortality and disability. PISS indicate poorer prognoses in patients experiencing IS.

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.