Structural alterations in the rat brain and behavioral impairment after status epilepticus: An MRI study

Abstract

Temporal lobe epilepsy (TLE) is one of the most common neurologic disorders often associated with behavioral impairments and cognitive deficit. Lithium–pilocarpine model of seizures in rodents reproduces many features of human convulsive status epilepticus (SE) and subsequent TLE. In this study, we have investigated changes in the rat brain after lithium–pilocarpine SE using a high-field MRI system for small animals in early and chronic periods after SE. We have studied the relationship between T2 relaxation time measured in these periods and the development of behavioral exploratory response to novelty and habituation in the open field test. A significant increase in T2 in the hippocampus and associated structures was found 2days after SE and practically resolved by day seven, while an increase in T2 in the parietal and prefrontal cortex appeared 30days after SE. High T2 values in the parietal cortex and thalamus on day two after SE were associated with an increased mortality risk. A substantial variability in T2 relaxation time was observed in the hippocampus and amygdala 30days after SE. Rats survived after SE showed locomotor hyperactivity and disruption of long-term habituation in the open field test carried out 5weeks after the seizures. Interestingly, T2 in the amygdala 30days after SE had a strong correlation with hyperactivity in the novel open field. Therefore, the amygdala damage may be an important factor in the development of hyperactivity in the chronic period after SE.