Hippocampal levels of ChAT, PKA, phospho-PKA and phospho-CaMKIIα but not CaMKIIα positively correlate with spatial learning skills in rats.

Despite very extensive investigations on molecular processes underlying memory formation, there are very few studies examining potential differences in the brain biochemistry between "good" and "poor" learners belonging to a random population of young animals. In the present study, an attempt was made to correlate individual variation in spatial learning in young-adult Long-Evans rats with hippocampal levels of protein kinase A (PKA), calcium/calmodulin-dependent protein kinase II alpha (CaMKIIα), and choline acetyltransferase (ChAT). Additionally, in order to indirectly estimate the activity of CaMKIIα and PKA, hippocampal levels of their phosphorylated forms (pCaMKIIα and pPKA) were assessed using Western blot technique. Rats were classified as "good" and "poor" learners on the basis of their performance in a partially baited 12-arm radial maze. The biochemical assays did not reveal a significant difference in the basal hippocampal levels of the CaMKIIα, however, the level of pCaMKIIα, was significantly higher in "good" learners. Also, hippocampal levels of both PKA and pPKA, as well as that of ChAT, were significantly higher in "good" as compared to "poor" learners. Our results suggest that the differences in the expression level of PKA and ChAT (but not of CaMKIIα), as well as the differences in the activation of both PKA and CaMKIIα, may contribute to the individual variation in learning skills and episodic-like memory in a random population of young-adult subjects.