Abstracts

Convulsive status epilepticus (SE) induces acute morphological changes in the motor cortex of immature rats. The aim of this study was to find out if there are any longlasting changes in the activity of cortical neurons.
SE was induced by lithium-pilocarpine followed by paraldehyde treatment in 12- and 25-day-old rats. Three months later these animals and their control littermates (not receiving pilocarpine) were anesthetized with urethane and spontaneous activity of individual cortical neurons was recorded extracellularly by means of glass microelectrodes filled with NaCl.
A total of 52 units was recorded in 10 control rats; 33 out of them fired randomly whereas only 19 could be classified as bursting neurons. In the SE25 group (10 animals, 59 cells) the majority of neurons generated bursts (n=38) and 21 cells fired in a random manner. The difference between controls and SE25 groups was significant. Only 19 cells were recorded in SE12 rats; 11 of them generated bursts and 8 fired randomly. This difference did not reach the level of statistical significance. The differences were more marked under light than under deep urethane anesthesia (depth of anesthesia was estimated according to EEG pattern). Average firing frequency under light anesthesia was lower in both SE12 and SE25 groups than in controls.
Difference in a firing mode and rate was found even 3 months after SE in spite of experimental conditions (general anesthesia). Changes were more pronounced in animals seized at the age of 25 days than in SE12 rats.
[Supported by: A grant No 309/00/1643 of the Grant Agency of the Czech Republic]