Multiple probe RNase protection assay for the simultaneous detection of Arc, c-fos, and zif268 RNAs. a, Hippocampal RNA levels for all three IEGs increased 45 min after systemic injection of pentylenetetrazole (PTZ) (50 mg/kg, i.p.) relative to caged controls. b, Detection of IEG RNAs in the hippocampus and primary visual cortex of rats trained in different versions of the spatial water task. The data shown here are from the experiment detailed in Results (Figs. 4, 5). See Materials and Methods and Results for full details of the assay and the behavioral groups. The asterisks in a and bindicate a small amount of full-length actin probe that was consistently seen in all samples.