Apoptotic markers in various stages of amygdala kindled seizures in rats

The aim of the study was to elucidate the relationship between various stages of amygdala kindling in rats and neuronal apoptosis. We used the unbiased method of RNase protection assay (RPA), measuring expression of several apoptosis-associated genes (for: caspase 1, caspase 2, caspase 3, FAS antigen, bax and bcl-x, bcl-2). The obtained results were also verified in situ in hippocampal slices, using the TUNEL method. The mRNA level of the investigated genes was estimated by densitometry and standardized according to the amount of L32 RNA. Only the expression of bcl-x L, caspase 2, caspase 3 and bax genes was measureable. In all experimental groups, the mRNA levels of bax and bcl-x genes were higher than mRNA of caspase-2 and caspase-3 genes. However, there were no statistically significant differences between the control and kindled animals. On the other hand, the TUNEL positive cells were found in total contralateral hippocampus of investigated animals belonging to C(0) (control group), C(3) (rats with 3rd stage of seizures) and c(5) (rats with 5th stage of seizures) groups. The number of TUNEL positive cells in the hippocampus was significantly higher in C(3) and C(5) groups (4.0 +/- 0.40 and 3.75 +/- 0.49) when compared to C(0) group (1.25 +/- 0.25). In conclusion, although apoptotic cells were found in situ in the hippocampus of kindled rats, RNase protection assay failed to measure any changes in mRNA levels of the chosen apoptotic genes. In our opinion, apoptotic cells might be too rare to detect any changes in gene expression. Therefore, the TUNEL procedure still remains the most favorable method of apoptotic cell death evaluation in the brain structures.