Cycloheximide phase-shifts, but does not prevent, de novo Krox-24 protein expression

Previous studies show that focal hippocampal injury transiently increases NMDA receptor-dependent expression of inducible transcription factors (ITFs including Krox-24) in rat dentate gyrus neurons. Furthermore, pretreatment with the protein synthesis inhibitor, cycloheximide (CHX), prevents de novo ITF protein expression 1 h post-injury. Here, we further characterize the effects of a single pretreatment dose of CHX on injury-induced expression of Krox-24 and show that CHX pretreatment phase-shifts (delays), but does not prevent, de novo expression of Krox-24 in hippocampal dentate gyrus neurons following injury. This may have implications for studies which use CHX pretreatment to examine the role of gene expression and de novo protein synthesis in long-term memory formation, the stabilization of long-term potentiation, kindling and neuronal injury.