zif/268 does not mediate increases in proenkephalin mRNA levels after NMDA receptor stimulation

THE immediate-early gene zif/268 is induced in the hippocampal dentate gyrus by stimuli leading to long-term potentiation (LTP), and is though then to alter the rate of transcription of other genes involved in hippocampal plasticity, such as the proenkephalin (Penk) gene. Injection of 50 microM NMDA in vivo on to the granule cells of the dentate gyrus results in a highly localized increase in Penk mRNA levels 24 h later, while vehicle has no effect. In contrast, there is a widespread induction of zif/268 mRNA throughout the dentate gyrus, after injection of either NMDA or vehicle. This suggests that zif/268 induction in the hippocampal dentate gyrus is not sufficient to increase Penk gene expression.