Abstract
Spontaneously occurring spike-wave discharges (SWDs) and serum concentrations of ovarian steroid hormones were investigated before, during and after pregnancy in WAG/Rij rats, a rat strain with genetically determined absence seizures. Eight groups of rats were included in the assays of progesterone and estradiol: rats at diestrus, at various days of pregnancy and at lactating days while EEG's were recorded at the same days in rats equipped with cortical EEG electrodes. Serum concentration of progesterone was 3-fold increased at the 3rd day of pregnancy and remained elevated till the 18th day of pregnancy, thereafter it returned to control values before delivery. Estradiol was elevated only at the 18th day of pregnancy. The number of SWDs were decreased from 3rd up to 18th days of pregnancy and progressively increased to control level 2 days before parturition. Thereafter a new decrease was found 2-3 after giving birth. These results demonstrate that the changes in plasma progesterone concentration corresponds to the changes in number of SWDs and have a similar time-course. It can be concluded that an increased level of progesterone that occur during pregnancy is associated with a decreased number of SWDs. However, the relationship between SWDs and concentration of progesterone found here is opposite to non-pregnancy data and an antiepileptogenic reaction might have taken place.
