Figure 1. Status epilepticus increases pre-rRNA levels suggesting stimulation of ribosomal biogenesis.

A, Pre-rRNA amplicons that were used for qRT-PCR determination of immature rRNA levels. Major processing sites of mouse pre-rRNA are marked [69]. The 5’ETS amplicon corresponds to the 47S pre-rRNA 5’ETS leader region that undergoes rapid processing providing best insight into nascent pre-rRNA levels. The amplicons corresponding to the 5’ETS/18S junction or the ITS1 regions may also detect more stable intermediates of rRNA processing. The indicated probes were used with 18S rRNA as a normalizer. Due to large quantities of mature ribosomes in the brain and post-mitotic/quiescent nature of most neural cells, total 18S rRNA levels are expected to change far slower than precursor rRNA providing optimal normalization for short-term pre-rRNA studies (i.e. hours-few days). B, Status epilepticus (SE) was induced in mice by kainic acid (KA). Levels of pre-rRNA were determined in the whole hippocampus as indicated. Note upregulation of 47S pre-rRNA as revealed by both 5’ETS and ITS1 probes and no changes in 5’ETS-18S processing intermediates at 6- but not 2 h after KA injection. C, Mice were injected with pilocarpine to induce SE. After 2.5 h, SE was interrupted by i.p. injections of diazepam and mice were killed one hour later. Control mice received the same treatment except pilocarpine. The 5’ETS leader probe revealed increased 47S pre-rRNA levels in the dentate gyrus (DG) and cornu Ammonis (CA) regions of pilocarpine-treated mice; in the CA, the upregulation was also detected with the ITS1 probe. Data represent averages ± SEM, u-test comparisons are to respective control groups; ns, p>0.05; *, p<0.05.