Continuous electroencephalographic monitoring with radio-telemetry in a rat model of perinatal hypoxia-ischemia reveals progressive post-stroke epilepsy

Impact of injury location and severity on posttraumatic epilepsy in the rat: role of frontal neocortex

Human posttraumatic epilepsy (PTE) is highly heterogeneous, ranging from mild remitting to progressive disabling forms. PTE results in simple partial, complex partial, and secondarily generalized seizures with a wide spectrum of durations and semiologies. PTE variability is thought to depend on the heterogeneity of head injury and patient's age, gender, and genetic background. To better understand the role of these factors, we investigated the seizures resulting from calibrated fluid percussion injury (FPI) to adolescent male Sprague-Dawley rats with video electrocorticography. We show that PTE incidence and the frequency and severity of chronic seizures depend on the location and severity of FPI. The frontal neocortex was more prone to epileptogenesis than the parietal and occipital, generating earlier, longer, and more frequent partial seizures. A prominent limbic focus developed in most animals, regardless of parameters of injury. Remarkably, even with carefully controlled injury parameters, including type, severity, and location, the duration of posttraumatic apnea and the age and gender of outbred rats, there was great subject-to-subject variability in frequency, duration, and rate of progression of seizures, indicating that other factors, likely the subjects' genetic background and physiological states, have critical roles in determining the characteristics of PTE.

Inflammation enhances epileptogenesis in the developing rat brain

In many experimental systems, proinflammatory stimuli exhibit proconvulsant properties. There are also accumulating data suggesting that inflammation may contribute to epileptogenesis in experimental models as well as in humans. Using two different models (Lithium-pilocarpine induced-status epilepticus (SE) and rapid kindling), we address this issue in the developing brain. Using P14 Wistar rat pups, we showed that inflammation induced by LPS results, after SE, into a more severe disease in adulthood. The main histological feature was an active gliosis that was observed only when inflammation and SE was combined. The use of a kindling model at P14, a model where seizure progress without any neurodegeneration, permits to show that systemic inflammation is responsible of an enhancement of epileptogenesis. The role of inflammation should be further explored in immature brain to identify therapeutic targets that may be relevant to clinical practice where the association of inflammation and epileptic events is common.

The effect of the cannabinoid-receptor antagonist, SR141716, on the early stage of kainate-induced epileptogenesis in the adult rat

Pretreatment with the endocannabinoid-receptor antagonist, SR141716, has been reported to suppress the long-lasting hyperexcitability and increased seizure susceptibility present after 30 min of hyperthermia-induced convulsions in immature rats, an animal model of complex febrile seizures in children, which may be a cause of temporal lobe epilepsy. The present experiments tested the hypothesis that SR141716 suppresses epileptogenesis in the adult kainate model, an animal model of temporal lobe epilepsy. Adult male rats (n = 35), implanted for electroencephalography (EEG) recordings, were treated with kainate. Immediately after the first acute electrographic seizure during kainate-induced status epilepticus, either vehicle or SR141716 (10 mg/kg) was injected intraperitoneally. Chronic video-EEG data were collected for the first 2-week period after kainate-induced status epilepticus. More than one-half of both the vehicle- and drug-treated animals showed spontaneous recurrent seizures. Similarly, mean seizure frequency did not differ significantly for the drug- and vehicle-treated animals during the first 2 weeks (n = 9 and 8, respectively). Therefore, no significant differences were found between SR141716-treated and control animals during the first 2 weeks of epileptogenesis. These results suggest that the endocannabinoid-receptor antagonist, SR141716, had no detectable effect on the early stages of epileptogenesis in the adult kainate model. We discuss several potential explanations for the differences in the effects of SR141716 in the adult-rat, kainate versus immature-rat, hyperthermia models.