TRANSCRIPTIONAL ACTIVATION OF ORNITHINE DECARBOXYLASE IN ADULT AND NEONATAL HIPPOCAMPAL SLICES

Ornithine decarboxylase (ODC) is the rate-limiting enzyme in polyamine synthesis and is regulated by both transcription-dependent and transc ription-independent mechanisms. We compared the effects of asparagine, an amino acid previously shown to increase ODC activity in adult hipp ocampal slices, on ODC mRNA and activity in adult and neonatal hippoca mpal slices. In addition, we evaluated the effects of asparagine on OD C activity following seizure activity elicited by systemic administrat ion of kainic acid (KA) in both adult and neonatal rats. Asparagine pr oduced an increase in ODC gene expression and activity in both adult a nd neonatal hippocampal slices. The increase in ODC activity elicited by asparagine in hippocampal slices was the same in control animals as in animals sacrificed 16 h after KA-induced seizure activity. The asp aragine-elicited increase in ODC activity in neonatal and adult hippoc ampal slices was blocked by the RNA synthesis inhibitor, actinomycin D . Finally, polyamines produced an inhibition of ODC activity in neonat al hippocampal slices. The results indicate that the regulation of the expression and activity of ODC is similar in neonatal and adult hippo campus.