Abstracts

Rationale: Present study was designed to characterize effects of early SE on development of cognitive abilities, adaptability and emotionality in short intervals after insult. Animals were tested using open field paradigm around weaning period, puberty onset and as young adults. Methods: SE was induced by pilocarpine (40 mg/kg) in LiCl (3meq/kg) pretreated P12 rats. To prevent mortality and to improve recovery rats were given a single dose of paraldehyde (0.3 mg/kg) 2h after SE onset. Controls received saline instead pilocarpine. The open field (OF) test was used to check the behavioral responses to novel environment, motor abilities, emotional stage and habituation. The animals were exposed to the OF box (45x45x30 cm) four times (6, 13, 26 and 40 days after SE) always for 5 minutes. Behavior was analyzed using EthoVision (Noldus Information Technology; The Netherland) and in addition to parameters of ambulation also time spent in central and peripheral zone, number of entries of central and peripheral zone and corners, incidence of wall leaning and rearing and duration of grooming were evaluated. Habituation, a non-associative learning process, was assessed as a progressive decrease of motor activity during the 5-min testing interval. Results: SE developed in all 24 animals. Clinically, status epilepticus was characterized by twitching of facial muscles, chewing, head bobbing, forelimb clonus, tail erection and swimming movements. Paraldehyde in a single dose of 0.3 ml/kg suppressed motor seizures. Mortality during 24h after SE was 42%, no animals died later. Slight decrease of the body weight was seen 24h after SE (3% decrease whereas controls gained 17 % of their weight at P12). Behavior in the open field was changing with age at the exposure. Animals with SE did not start to habituate before the second test whereas in controls the first signs of habituation occurred already at P18. In test 1, 2 and 3 SE animals prefer to stay in periphery (i.e. safe area) and they also explored central zone (i.e. dangerous area) less frequently than controls. Incomplete grooming as well as freezing was more often seen in SE than in control rats. These data suggest higher anxiety and altered adaptation in animals with SE compared to their intact siblings. In contrast, there was no difference in velocity of ambulation between these two groups suggesting that observed changes are not due to SE-induced motor impairment. Conclusions: SE during early postnatal development leads to developmental delay of cognitive abilities and to increase of emotionality later in the life. In contrast, motor abilities are not impaired. Supported by grants No P302/10/0971 (Grant Agency of the Czech Republic), ME08045 and LC554 (Ministry of Education of the Czech Republic)