Involvement of hippocampal CAMKII/CREB signaling in the spatial memory retention induced by creatine

Although Creatine (Cr) and Phosphocreatine (PCr) systems play a key role in cellular energy and energy transport in neuronal cells, its implications for learning and memory are still controversial. Thus, we decided to investigate the involvement of cAMP-dependent protein kinase A (PKA), Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) and cAMP responsive element binding protein (CREB) in the spatial consolidation after an intrahippocampal injection of Cr. Statistical analysis revealed that Cr (2.5 nmol/hippocampus) (post-training) decreased the latency for escape and the mean number of errors on Barnes maze test. Post-training co-administration of the PKA inhibitor (H-89 25 ρmol/hippocampus) did not alter the facilitatory effect of Cr in this memory test. On the other hand, Cr-induced spatial retention was reverted by co-administration of the CaMKII inhibitor (STO-609 5 nmol/hippocampus). Neurochemical analysis revealed that intrahippocampal injection of Cr, when analyzed after 30 min rather than after 3 h, increased the levels of pCREB and pCaMKII but not pPKA levels. Statistical analysis also revealed that the post-training co-administration of STO-609 but not H-89 reversed the increase of pCREB levels induced by Cr. The results presented in this report suggest that intracellular CaMKII/CREB pathway plays a key role in the Cr-induced spatial retention. Thus, it is plausible to propose that Cr plays a putative role as a neuromodulator in the brain, and that at least some of its effects may be mediated by intracellular CaMKII/CREB pathway.