Effect of age and cognitive status on basal level AP-1 activity in rat hippocampus.

Activator protein-1 (AP-1) was examined at multiple levels (mRNA, DNA binding, composition) in hippocampus of young and aged rats that were behaviorally characterized for spatial memory. GFAP mRNA was measured as a gene product known to increase with aging and to be regulated by AP-1. The activity of Jun-amino terminal-kinase (JNK) was also assessed. Levels of c-jun and c-fos mRNAs were unchanged with aging or spatial learning ability. Abundance of GFAP mRNA was significantly increased in aged hippocampus but did not correlate with spatial learning. Total AP-1 binding activity was unaltered with age or cognitive ability. In hippocampus of young, aged unimpaired and aged impaired rats, AP-1 consists mainly of c-Jun, phosphorylated c-Jun (p-c-Jun), JunD, and smaller amounts of c-Fos. JNK is constitutively active in young and aged hippocampus. We conclude that the basal expression of c-fos and c-jun mRNA, overall AP-1 binding activity and AP-1 composition are not influenced by aging or cognitive ability.