Induction of integrin-associated protein (IAP) mRNA expression during memory consolidation in rat hippocampus

We have previously demonstrated that hippocampal integrin-associated protei n (IAP) gene expression is associated with memory formation in a one-way in hibitory avoidance learning in rats. In the present study, we further inves tigated the role and mechanism of IAP involved in memory consolidation in r ats. Because of the minute amount of IAP present in the brain, we have adop ted the quantitative reverse transcription-polymerase chain reaction (RT-PC R) method. Our results revealed that hippocampal IAP mRNA expression is app roximately fourfold higher in rats showing good memory retention (GM, reten tion score of 600 s) at 3 h, but not at other time points, after training w hen compared with the poor memory rats (retention score < 80 s). On the oth er hand, integrin alpha v mRNA level was markedly increased (similar to two fold), while integrin beta 3 mRNA level was decreased (similar to 50%) at 1 h post-training. Further, separate sets of RT-PCR analysis revealed that I AP5 and IAP6 mRNA expressions, but not that of IAP7, were markedly increase d in GM rats 3 h post-training. Moreover, regional distribution studies rev ealed that different isoforms of the IAP gene are similarly distributed in different brain areas, while IAP7 has been the predominant form present in astrocyte cells. These results together suggest that IAP mRNA expression is indeed induced upon training, rather than that the GM rats have constituti vely higher levels of IAP. The unparallel change of IAP and integrin mRNA e xpressions as far as time-course is concerned suggests that they are possib ly involved in different forms and stages of memory processing. Further, IA P5 and IAP6 are more closely associated with memory consolidation, while IA P7 may constitute the major isotype for signal transduction in astrocyte ce lls.