Rapid and transient increase in hippocampal IEG RNA levels after spatial water-task training. IEG RNA levels from rats killed at 0.5, 2, and 6 hr after spatial water-task training were compared with caged control levels using the multiple probe RPA. RNA levels for all three IEGs were significantly above control levels at 0.5 hr after training, and c-fos RNA levels were lower than caged control levels 6 hr after training. *p< 0.05 relative to caged (0 hr) group, Mann–Whitney Utest. n = 3–5 rats per group.