[Postictal depression in 12-day-old animals]

Postictal depression systematically follows epileptic after-discharges (AD) evoked from many different regions of the brain of adult animals. In presented experiments we tested by evoking ADs from sensorimotor cortex whether the susceptibility to undergo postictal depression is age-dependent and whether it correlates with the individual duration of ADs. Groups of 12-, 18- and 25-day-old male rats were used (freely moving animals--semichronic preparations; six trains of rhythmic electrical stimulations in one min. intervals after the end of previous seizure; EEG recordings; durations of ADs were measured). In the whole group of the 25-day-old animals the mean duration of ADs after individual stimulations illustrated the inhibitory influence of the first seizure on the duration of all subsequent ADs. In 18-day-old animals the depression was less pronounced and in 12-day-old it seemed to be not present. Analysis of results in individual animals in the group of youngest animals showed, that duration of pairs of subsequent seizures was related to the duration of the first of them. Also in this age group long seizures caused postictal depression. Duration of seizures seems to vary individually and it strongly influences the mean results of the whole group. The differences between the groups could be explained on the basis of the different pattern of ADs in young and older animals. In young animals the total "output" of seizure is low and it could also cause not so intensive and long posttetanic depression based on changes of intracellular Ca2+, because this form of synaptic plasticity seems to involve the activation of Ca(2+)-dependent protein kinases. Synaptic energy consumption also may play some role in postictal depression occurrence.