Aging alters electroencephalographic and clinical manifestations of kainate-induced status epilepticus

The elderly exhibit an increased risk for developing status epilepticus and status-related morbidity and mortality. However, it is unclear how aging alters the progression of electroencephalographic (EEG) activity and behavioral manifestations during status epilepticus.

A repetitive low-dose kainate treatment protocol (2.5 mg/kg/h; i.p.) was used in this study in conjunction with EEG and behavioral monitoring from freely behaving adult (7-8 months) and aged (22-25 months) Fischer 344 rats to assess the effects of aging on status epilepticus.

During kainate treatment, both groups exhibited an increase in EEG power that corresponded with the time course of kainate treatment. However, visual inspection and spectral analysis revealed a reduction of the faster frequencies (12.5-35 Hz) in the EEGs of aged rodents. A similar progression of behavioral manifestations was observed in adult and aged rodents during kainate treatment, although the frequency of preseizure manifestations (e.g., wet-dog shakes; aged rats, 110 events/h vs. adults, 25 events/h; median values) was greater, and latency to onset for any given behavioral manifestation (e.g., class V seizures; aged median, 60 min, vs. adult median, 145 min) was consistently shorter within the aged group.

These data reveal that aged Fischer 344 rats exhibit altered EEG activity (reduction of higher frequencies) and clinical manifestations during kainate-induced status epilepticus. Taken together, these data indicate an age-related change in seizure onset and spread after exposure to glutamate analogues.