Dentate gyrus autonomous ictal activity in the status epilepticus rat model of epilepsy.

The dentate gyrus (DG) as part of the hippocampal formation is believed to serve as a gatekeeper with strong inhibitory properties against uncontrolled propagation of neuronal activity from the entorhinal cortex and neocortical structures. In temporal lobe epilepsy, the DG becomes hyperexcitable and loses its gate function, enabling propagation of ictal activity into downstream structures such as CA3 and CA1 areas. Furthermore, the DG, apart from facilitating propagation, may also be able to autonomously generate ictal activity, but this point has remained open so far.

Circadian dentate gyrus excitability in a rat model of temporal lobe epilepsy.

In human mesial temporal lobe epilepsy (mTLE), seizure occurrence peaks in the late afternoon and early evening. This temporal binding of seizures has been replicated in animal models of mTLE following electrically-induced status epilepticus (SE). We hypothesized that in chronic epilepsy, alterations of circadian excitatory and inhibitory functions of the dentate gyrus (DG), which is believed to regulate the generation of limbic seizures, pathophysiologically contribute to the temporal binding of ictogenesis.

Functional and morphological changes in the dentate gyrus after experimental status epilepticus.

Status epilepticus may cause long-term functional and structural consequences possibly resulting in brain dysfunctions such as chronic epilepsy. In epileptogenesis, the dentate gyrus plays a key role in regulating the excitability of highly vulnerable and potentially epileptogenic downstream structures in the hippocampus proper. One, four and eight weeks after electrically induced status epilepticus, excitability and neuronal degeneration in the rat dentate gyrus were examined with intracerebral electrodes and Fluoro Jade (FJ) staining, respectively.

Temperature regulation is compromised in experimental limbic status epilepticus.

Temperature dysregulation is well known in generalized convulsive status epilepticus but so far has not been reported in non-convulsive forms. In order to detect possible subtle alterations, we have analyzed the capability to compensate for external cooling in an animal model of limbic status epilepticus. Rats with electrically induced self-sustaining status epilepticus (SSSE) (n=6) as well as rats without electrical stimulation (n=6) were cooled for 3 h and then rewarmed for another hour.

Diagnosis of psychogenic nonepileptic status epilepticus in the emergency setting.

Episodes of psychogenic nonepileptic status epilepticus (PNESE) characterized by pronounced generalized motor features were compared with those of refractory generalized convulsive status epilepticus. Patients with PNESE were younger, had port systems implanted more frequently, received higher doses of benzodiazepines until seizure termination or respiratory failure, and had lower serum creatine kinase levels.

Repetitive spreading depression-like events result in cell damage in juvenile hippocampal slice cultures maintained in normoxia.

Prolonged seizures, e.g., induced by fever, experienced early in life are considered a precipitating injury for the subsequent development of temporal lobe epilepsy.

A "malignant" variant of status epilepticus.

Background: Status epilepticus (SE) frequently does not respond to common first-line anticonvulsants. In a substantial portion of patients, administration of anticonvulsant anesthetics is inevitable. Even this aggressive approach fails to terminate SE in an undefined number of cases.

Processes and components participating in the generation of intrinsic optical signal changes in vitro.

Imaging of intrinsic optical signals has become an important tool in the neurosciences. To better understand processes underlying changes in intrinsic optical signals, we studied electrical stimulation at varying strengths in hippocampal slices of adult Wistar rats. Following serial stimulation we observed an increase in light transmittance in all tested slices.

Oxygen consumption and mitochondrial membrane potential indicate developmental adaptation in energy metabolism of rat cortical neurons.

Neuronal energy needs are mainly covered via mitochondrial oxidative phosphorylation. Even if the energy supply appears identical in immature and adult brain, nevertheless quantitative differences exist. The present study focuses on the adaptations in cellular energy metabolism caused by the neuronal maturation.

Increased extracellular K+ concentration reduces the efficacy of N-methyl-D-aspartate receptor antagonists to block spreading depression-like depolarizations and spreading ischemia.

Background And Purpose: Spreading depression (SD)-like depolarizations may augment neuronal damage in neurovascular disorders such as stroke and traumatic brain injury. Spreading ischemia (SI), a particularly malignant variant of SD-like depolarization, is characterized by inverse coupling between the spreading depolarization wave and cerebral blood flow. SI has been implicated in particular in the pathophysiology of subarachnoid hemorrhage.

Seizure spread through the life cycle: optical imaging in combined brain slices from immature, adult, and senile rats in vitro.

The semiology of epileptic seizures changes during the lifetime. Hence, it can be assumed that age-related changes in brain plasticity influence the patterns of seizure onset, spread and propagation velocity. We employed the 4-aminopyridine model of epilepsy to study seizure-like events in vitro.

Limbic self-sustaining status epilepticus in rats is not associated with hyperthermia.

Purpose: To evaluate the impact of limbic status epilepticus on temperature.

Methods: The perforant path in freely moving rats was stimulated electrically for 120 min to induce self-sustaining status epilepticus (SSSE). For 150 min after the end of stimulation, epidural temperature and electrographic and clinical seizure activity were assessed in animals with limbic and motor SSSE, as well as in animals without development of SE.

Decrease in haemoglobin oxygenation during absence seizures in adult humans.

Near-infrared spectroscopy (NIRS) is a noninvasive method that allows the assessment of activation-induced cortical oxygenation changes in humans. It has been demonstrated that an increase in oxygenated and a decrease in deoxygenated haemoglobin can be expected over an area activated by functional stimulation. Likewise, an inverse oxygenation pattern has been shown to be associated with cortical deactivation.

Furosemide terminates limbic status epilepticus in freely moving rats.

Purpose: To evaluate the anticonvulsant properties of furosemide and to determine sedative side effects compared with pentobarbital and diuretic side effects compared with saline-treated controls in an experimental model of limbic status epilepticus.

Methods: Self-sustaining status epilepticus was induced in rats by continuous electrical stimulation of the perforant path. Five minutes after the end of the stimulation, animals were given 100 mg/kg furosemide, 30 mg/kg pentobarbital, or an equal amount of saline, intraperitoneally.

Intrinsic optical imaging reveals regionally different manifestation of spreading depression in hippocampal and entorhinal structures in vitro.

The spatiotemporal features of spreading depression (SD) were analyzed in vitro by using combined hippocampal-entorhinal cortex slices. SDs were induced by microinjection of 1 M KCl in the stratum radiatum of the CA1 region of the hippocampus. Measurements of extracellular field potentials, extracellular space (ECS) volume changes and intrinsic optical signal changes were combined to study SD features in different regions of the slice.