Differential Expression of Activating Transcription Factor-2 and c-Jun in the Immature and Adult Rat Hippocampus Following Lithium-Pilocarpine Induced Status Epilepticus

PURPOSE: Lithium-pilocarpine induced status epilepticus (LPSE) causes selective and age-dependent neuronal death, although the mechanism of maturation-related injury has not yet been clarified. The activating transcription factor-2 (ATF-2) protein is essential for the normal development of mammalian brain and is activated by c-Jun N-terminal kinase (JNK). It induces the expression of the c-jun gene and modulates the function of the c-Jun protein, a mediator of neuronal death and survival. Therefore, we investigated the expression of c-Jun and ATF-2 protein in the immature and adult rat hippocampus to understand their roles in LPSE-induced neuronal death. MATERIALS AND METHODS: Lithium chloride was administrated to P10 and adult rats followed by pilocarpine. Neuronal injury was assessed by silver and cresyl violet staining, performed 72 hours after status epilepticus. For evaluation of the expression of ATF-2 and c-Jun by immunohistochemical method and Western blot, animals were sacrificed at 0, 4, 24, and 72 hours after the initiation of seizure. RESULTS: Neuronal injury and expression of c-Jun were maturation-dependently increased by LPSE, whereas ATF-2 immunoreactivity decreased in the mature brain. Since both c-Jun and ATF-2 are activated by JNK, and targets and competitors in the same signal transduction cascade, we could speculate that ATF-2 may compete with c-Jun for JNK phosphorylation. CONCLUSION: The results suggested a neuroprotective role of ATF-2 in this maturation-related evolution of neuronal cell death from status epilepticus.

The Effect and the Mechanism of Action of High Frequency Electrical Stimulation of Subthalamic Nucleus on Status Epilepticus Induced by Lithium-Pilocarpine of Rat / 대한간질학회지

OBJECTIVES: Deep brain stimulation (DBS) of subthalamic nuclei (STN) is one of the current modalities of refractory epilepsy, but its exact mechanism and route of action have not been elucidated yet. We investigated the effect of STN stimulation on the development and propagation of seizures in the rats with lithium-pilocarpine induced status epilepticus in its functional anatomy. METHODS: Both pilocarpine injection and high frequency stimulation on STN (HFSSTN) were provided to rats (STN group, n=12), but pilocarpine injection with no stimulation was done on the sham group (n=8). The latency to first discrete ictal discharges and the latency to status epilepticus (SE) were analyzed and the electrical stimulation lasted for 30, 60, 90, 120 minutes after its first discrete spikes. After stimulation, the rats were immediately decapitated for immunohistochemistry and histologic examination. RESULTS: Both the latency to first discrete ictal discharges and the latency to the onset of SE were delayed in the STN group than in the sham group. The latency to the first SE was also more delayed in the STN group (42.7+/-7.9 min) than in the sham group (p<0.05). Remarkably, there was marked Fos immunoreactivity (FIR) on the reticular thalamic nuclei in the STN group, but not in the sham group. CONCLUSIONS: Increased FIR in the reticular thalamic nuclei during HFSSTN suggested that the facilitation of the inhibitory thalamic output prevented generalized motor seizure behavior. We assume that HFSSTN has a pivotal role in the suppression or progression to SE, but cannot prevent seizure onset.

Antiepileptic and Neuroprotective Effect of Ketamine in Lithium-Pilocarpine Induced Status Epilepticus Rat Model / 대한간질학회지

PURPOSE: To examine the putative seizure-protective properties of ketamine in lithium-pilocarpine induced status epilepticus (LPSE). METHODS: Lithium chloride followed 24 h later by pilocarpine was administered for seizure induction. Ketamine (40 mg/kg) or phenytoin (50 mg/kg) was injected intraperitoneally 10 min or 60 min after the onset of continuous ictal discharge. Then the seizure behavior and EEG were observed and histological changes were compared through Nissl stain at 72 hours. RESULTS: The antiepileptic effect of ketamine, injected during the early stages of LPSE (10 min after the onset of continuous ictal discharge), was comparable to that of phenytoin. Ketamine was more effective than phenytoin in decreasing spike frequency, when administered on the plateau of LPSE (injection 60 min after onset of continuous ictal discharge electrographically). Anticonvulsant action of ketamine was confirmed by a less neuronal injury in hippocampus compared with control rats injected with phenytoin. CONCLUSIONS: In prolonged status epilepticus rat model, ketamine was effective as an antiepileptic, but phenytoin was not. Ketamine was also neuroprotective on the neuronal injury in the hippocampus. These results suggest that ketamine might be useful as an antiepileptic drug when standard antiepileptic drugs fail in the treatment of the refractory cases of status epilepticus.